This handbook is meant as a companion, not a substitute for your visits. The goal is simple: when something is recommended in clinic — a medication, a procedure, a device, a follow-up plan — you should be able to come home, sit with this guide, and feel confident about what is happening and why.

Heart rhythm conditions can be confusing the first time you meet them. Names like atrial fibrillation, SVT, AV block, or tachycardia all describe variations on a single underlying idea — the heart's electrical timing has shifted from where it usually sits. Most of the time, the variation is small, manageable, and compatible with a long, full life. A smaller number of conditions need closer attention; a smaller number still are urgent. The work we do together is to figure out which kind of problem yours is, and to choose a plan that respects your life as much as it respects the heart.

This handbook is organized into three parts. Part one explains how the heart's electrical system works. Part two covers the most common rhythm conditions we see, one chapter each. Part three explains the devices we sometimes need to implant, also one chapter each. A short glossary and a clear list of when to call us close out the book.

Throughout the chapters, look for the Key points boxes — they summarize what to remember if you read nothing else. Each chapter ends with what to expect at your visit and links to learn more on the patient education library at learn.colombowala.com.

The heart is, at its core, a pump. But it can only pump if its four chambers contract in the right sequence and the right speed. The electrical system is what tells the chambers when to squeeze.

The pacemaker, the wires, and the muscle

Each heartbeat begins in a small cluster of specialized cells in the top right chamber of the heart called the sinoatrial (SA) node. The SA node is the heart's natural pacemaker. About once a second, it generates a tiny electrical impulse. That impulse spreads outward through both upper chambers — the atria — causing them to contract and push blood into the lower chambers.

The impulse then reaches a relay point at the center of the heart called the atrioventricular (AV) node. The AV node delays the signal by a fraction of a second, giving the atria time to finish their squeeze. After this brief pause, the signal travels down the His-Purkinje system, a fast set of electrical fibers that distributes the impulse to the lower chambers — the ventricles — which contract to push blood out to the lungs and the body.

Where things can go wrong

Rhythm problems show up when one of these steps misfires:

• The SA node fires too fast, too slow, or unpredictably — leading to sinus tachycardia, bradycardia, or sick sinus syndrome.
• The atria misfire chaotically — leading to atrial fibrillation or atrial flutter.
• An extra electrical circuit competes with the normal one — leading to SVT (supraventricular tachycardia).
• The AV node or His-Purkinje conduction fails — leading to heart block, sometimes requiring a pacemaker.
• The ventricles initiate their own rhythm — leading to PVCs, ventricular tachycardia, or ventricular fibrillation.

Each chapter that follows takes one of these problems and walks through what it looks like, what it feels like, how we diagnose it, and what we can do about it.

What is happening in the heart

Normally, each heartbeat starts in the sinus node — a small cluster of cells in the upper-right chamber of the heart — and travels in an orderly wave that squeezes the atria, then the ventricles. In atrial fibrillation, the atria stop firing in that orderly way. Instead, many small electrical wavelets fire chaotically — often more than 400 times per minute. The atria don’t really squeeze; they quiver.

The AV node acts as a gatekeeper between the atria and the ventricles. It blocks most of those chaotic signals, but a fraction get through, and the ventricles end up beating irregularly — sometimes fast, sometimes at a normal rate.

Why it matters

Two main reasons:

1. Stroke risk. When the atria don’t contract well, blood can pool — especially in a small pouch called the left atrial appendage — and a clot can form. If a clot travels to the brain, it causes a stroke. This is the single most important reason we treat AFib aggressively.
2. Symptoms and heart function. Some people don’t feel AFib at all. Others feel palpitations, fatigue, breathlessness, or chest discomfort. Long-standing fast AFib can also weaken the heart muscle (called tachycardia-mediated cardiomyopathy), which usually improves once the rhythm is controlled.

How we classify it

• Paroxysmal — comes and goes on its own, episodes lasting less than 7 days.
• Persistent — lasts longer than 7 days; usually needs a cardioversion or rhythm-control plan to convert back.
• Long-standing persistent — continuous for more than a year, but rhythm control still being attempted.
• Permanent — a shared decision to stop trying to restore normal rhythm and focus on rate control and stroke prevention.

The classification matters because earlier, more episodic AFib tends to respond better to ablation than long-standing AFib.

How we diagnose it

A standard 12-lead ECG is enough when AFib is happening at the moment we record it. When AFib is intermittent, we use longer monitors: a 24–48-hour Holter, a 2-week patch monitor, a mobile cardiac telemetry monitor, or — for very infrequent episodes — an implanted loop recorder. Smartwatches and consumer ECG devices are increasingly useful for catching episodes at home.

How we treat it

We think about three pillars:

1. Stroke prevention. Based on individual risk (we use a calculator called CHA₂DS₂-VASc), most AFib patients benefit from a blood thinner. For patients who can’t take a blood thinner long term, a left-atrial appendage closure device (such as WATCHMAN) is an option.
2. Rate control. If the ventricles are beating fast, we slow them with medications like beta-blockers or non-dihydropyridine calcium channel blockers.
3. Rhythm control. Restoring and maintaining normal rhythm. Options include antiarrhythmic medications, cardioversion (a brief electrical reset), and catheter ablation — which has become a first-line option for many patients, particularly with paroxysmal AFib.

What to expect at your visit

We’ll talk through your symptoms, look at any monitoring data, and tailor a plan to your goals. There’s almost always more than one reasonable path. Lifestyle factors — alcohol, sleep apnea, weight, blood pressure — matter a lot and we’ll discuss those too.

Further reading

Additional patient resources on AFib from the American Heart Association:

• What Is Atrial Fibrillation? — AHA Answers by Heart — a two-page plain-English fact sheet
• Atrial Fibrillation — AHA animation library — pick “Atrial Fibrillation” from the topic menu for an animated explanation of how AFib develops in the upper chambers and why it raises stroke risk

What is happening in the heart

“Supraventricular” simply means “above the ventricles.” SVT is an umbrella term for fast heart rhythms whose engine sits in the atria or in the small electrical junction between the atria and ventricles — not in the ventricles themselves. During an episode, the heart rate often jumps to 150–220 beats per minute and stays there until the rhythm breaks.

The three patterns we see most often look similar to a patient but use different wiring inside the heart:

AVNRT (AV nodal reentrant tachycardia)

The most common form. Two pathways with slightly different conduction speeds exist inside the AV node — the small junction between the atria and the ventricles. Under the right conditions, the electrical signal loops back on itself inside that junction, going around and around at high speed and driving the rest of the heart along with it.

AVRT (AV reentrant tachycardia)

This form uses an accessory pathway — an extra strand of muscle that someone is born with, connecting the atria and the ventricles outside the normal AV node. The circuit loops between the two chambers using that extra connection. Wolff-Parkinson-White syndrome is the best-known example.

Atrial tachycardia

Here a single small spot in the atrium — outside the sinus node — fires rapidly on its own and drives the heart, like a second engine running too fast.

Why it matters

For most patients, SVT is uncomfortable but not dangerous. The chambers are still filling and emptying in sequence, and the heart muscle itself is healthy. The bigger problems are quality of life and unpredictability — episodes can interrupt work, exercise, driving, and sleep, and some patients describe a lingering anxiety between episodes.

There are two situations where we treat SVT more urgently:

• Long episodes that drop blood pressure or cause chest pain, severe shortness of breath, or fainting.
• AVRT with rapid AFib through an accessory pathway — uncommon, but the reason we take Wolff-Parkinson-White seriously even when symptoms are mild.

How we diagnose it

The single most useful piece of information is a 12-lead ECG captured during an episode. The pattern on that tracing usually tells us which type of SVT is at work. Because episodes are often brief, we lean on monitors:

• Holter (24–48 hours) when episodes are frequent.
• Patch monitor (1–2 weeks) when episodes are weekly or so.
• Mobile cardiac telemetry for longer monitoring with real-time review.
• Implantable loop recorder for very infrequent but disabling episodes.
• Smartwatch ECG — increasingly useful for capturing a tracing the moment symptoms hit.

When the diagnosis is still unclear, or when we are planning ablation, we recommend an electrophysiology (EP) study: thin catheters are positioned in the heart through veins in the groin, and we deliberately bring on the rhythm in a controlled setting to map exactly what’s happening.

How we treat it

Stopping an episode

• Vagal maneuvers — bearing down as if having a bowel movement, or applying a cold pack to the face. These work by stimulating the vagus nerve, which briefly slows conduction through the AV node and can break the circuit.
• Adenosine — a short-acting medication given through an IV that interrupts conduction through the AV node for a few seconds. Effective, but the few seconds while it works can feel unpleasant.
• Cardioversion — a brief electrical reset, reserved for episodes that don’t break with medication or that cause significant symptoms.

Preventing future episodes

• Daily medication — beta-blockers or calcium channel blockers reduce how often episodes occur, though they rarely eliminate them.
• Catheter ablation — the definitive treatment for most SVTs. We map the circuit in the EP lab and then create a tiny area of scar that interrupts it. For AVNRT, success rates exceed 95% with a very low complication rate. For most accessory-pathway SVTs, success is similarly high. For atrial tachycardia, success depends on where the focus sits but is generally 80–90%.

What to expect at your visit

We’ll go through what your episodes feel like, how they start and stop, what triggers them, and what (if anything) helps. We’ll review any tracings you’ve captured — from monitors, hospital visits, or your watch. If we already have an ECG during an episode, we can often predict the type. If not, we’ll talk about which monitor makes sense, and whether an EP study with possible ablation is the right next step.

What is happening in the heart

A normal heartbeat starts at the top of the heart and travels down through the wiring system to the ventricles in a tightly orchestrated wave. In ventricular tachycardia, the rhythm bypasses that wiring entirely and fires from somewhere inside the ventricular muscle itself — usually 150 to 250 beats per minute. Because the signal is no longer coming through the normal pathway, the two ventricles squeeze inefficiently and out of sync with the atria. Blood pressure can fall, and if the rhythm degenerates further into ventricular fibrillation, the heart stops pumping altogether. That is what we mean by sudden cardiac arrest.

The two shapes we look for

On the ECG, every VT beat looks the same in monomorphic VT — meaning the rhythm is escaping from a single spot in the ventricle and following the same path each time. In polymorphic VT, the QRS complexes change shape from beat to beat, often spiraling, because the rhythm is moving around constantly. The distinction matters because each shape points to different causes and different treatments.

Two big categories of cause

Idiopathic VT — a structurally normal heart

Some patients develop VT despite having a completely healthy heart muscle. These rhythms often arise from very specific spots — the right ventricular outflow tract or one of the fascicles of the left bundle branch are classic locations. Idiopathic VT is usually monomorphic, often triggered by exercise or stress, and is generally well tolerated. The good news is that ablation cures most of these cases.

Scar-mediated VT — VT in a damaged heart

Far more concerning. When heart muscle has been injured — usually by a prior heart attack, but also by cardiomyopathies, sarcoidosis, myocarditis, or surgical scars — strands of surviving tissue weave through the scar. Electrical signals can loop around those strands, creating a sustained, organized circuit. Scar-mediated VT tends to be faster, less tolerated, and is the rhythm we worry about most in patients with reduced ejection fraction.

Polymorphic VT and torsades

When VT is polymorphic, the cause is usually different again — acute ischemia (an unfolding heart attack), severe electrolyte abnormalities, or a long QT interval. Torsades de pointes is a specific polymorphic VT seen with long QT and is covered in the long-QT entry.

Why it matters

VT is the most common mechanism of sudden cardiac death in adults. Even when an episode self-terminates, it’s a warning shot. We take every documented VT seriously, work hard to find the underlying cause, and decide whether an ICD is needed.

How we diagnose it

We rely on the 12-lead ECG captured during an episode whenever possible — the shape and rate of the rhythm tell us where it’s coming from. When VT is intermittent, we use longer monitors: patch monitors, mobile telemetry, or a loop recorder. We then look at the heart itself — usually with an echocardiogram, often with a cardiac MRI to look for scar — to decide which category of VT we’re dealing with. In selected cases, we do an electrophysiology study: catheters inside the heart that map the circuit directly.

How we treat it

Treatment has three pillars, and most patients need more than one.

1. Treat what’s underneath. Open a blocked artery, optimize heart-failure medications, correct potassium and magnesium, stop a QT-prolonging drug. Many VT problems improve dramatically once the trigger is addressed.
2. Suppress the rhythm. Beta-blockers are the foundation for almost every type of VT. Antiarrhythmic drugs — amiodarone, sotalol, mexiletine — are added when needed.
3. Ablation. For idiopathic VT, ablation is often curative. For scar-mediated VT, ablation reduces the burden of episodes and shocks; we map the scar and burn the circuits that drive the rhythm.

ICDs: primary and secondary prevention

An implantable cardioverter defibrillator is the only therapy proven to abort a sudden-cardiac-death event in progress. We use them in two settings:

• Secondary prevention — you’ve already had a sustained VT or a cardiac arrest. The ICD is highly recommended in nearly every case.
• Primary prevention — you haven’t had an event, but your risk is high enough that we recommend the device before something happens. The clearest example is a reduced ejection fraction (typically 35% or below) despite good medical therapy. Inherited conditions like hypertrophic cardiomyopathy, long QT, and Brugada have their own risk frameworks.

ICDs come in transvenous and subcutaneous designs, and the choice depends on whether you also need pacing.

What to expect at your visit

We’ll go through the ECG of your episode (or any monitor recordings), look at your heart’s structure and function, and figure out which category of VT you’re in. From there we talk through medication, ablation, and ICD options. None of these decisions are made in isolation — they’re based on the underlying cause, your symptoms, your other medical conditions, and your goals.

What is happening in the heart

Each normal heartbeat starts in the sinus node at the top of the right atrium, spreads across both atria, and then has to pass through a single narrow gateway — the AV node — to reach the ventricles. From the AV node, the signal travels down a specialized wire called the His-Purkinje system that branches into the left and right bundles and delivers the impulse to every cell of the ventricles almost simultaneously.

“AV block” means that somewhere along this pathway, signals are not getting through reliably. The block can sit in the AV node itself or further downstream in the His-Purkinje system, and that location is one of the most important things we try to figure out — because it predicts how the block will behave.

The grades of AV block

First-degree AV block

The signal always makes it from the atria to the ventricles, but the trip takes longer than usual. On an ECG, this shows up as a prolonged PR interval. By itself, first-degree block is almost always benign — common with age, with certain medications, and in well-trained athletes. We watch it but do not treat it.

Second-degree AV block

Some atrial impulses get through, others don’t. The pattern of which ones drop tells us a great deal.

Mobitz I (Wenckebach). Each PR interval gets slightly longer, beat after beat, until one impulse fails to conduct entirely — then the cycle starts over. This pattern almost always means the block sits inside the AV node itself. It is usually benign, often appears during sleep in healthy people, and rarely progresses to anything worse. Treatment is reserved for patients with clear symptoms tied to the block.

Mobitz II. Some impulses suddenly fail to conduct without any warning lengthening of the PR interval. This pattern usually means the block sits below the AV node, in the His-Purkinje system — a structurally less forgiving location. Mobitz II is unstable and unpredictable, and can deteriorate suddenly into complete heart block with long pauses. A pacemaker is recommended for Mobitz II regardless of symptoms.

2:1 AV block. Every other beat conducts. Without other clues we can’t always tell whether this is a slow Mobitz I or a Mobitz II, and we sometimes need additional testing — or an electrophysiology study — to localize the level.

High-grade AV block. Two or more consecutive impulses fail to conduct. This is treated the same way as Mobitz II: a pacemaker is almost always indicated.

Third-degree (complete) AV block

No atrial impulses get through to the ventricles at all. The atria and ventricles beat completely independently — the atria still firing at the usual rate from the sinus node, and the ventricles relying on a slow “escape” rhythm from somewhere below the block. If the escape comes from just below the AV node, it is usually around 40–55 beats per minute and reasonably stable. If it comes from deep in the His-Purkinje system, it is often slower and far less reliable. Either way, complete AV block requires a pacemaker.

Why it matters

The risks tracked with AV block are two-fold:

1. The heart rate is too slow for what the body needs. Patients feel fatigue, exertional shortness of breath, lightheadedness, exercise intolerance, and sometimes confusion. The lower and more unreliable the escape rhythm, the more profound the symptoms.
2. Long pauses. When the escape rhythm fails to kick in promptly, a several-second pause can cause fainting and falls — sometimes with significant injury — and in rare cases sudden death.

Mobitz II and complete AV block are particularly dangerous because they sit below the AV node and the escape rhythms are unreliable. That’s why we pace them even when the patient hasn’t yet had severe symptoms.

How we diagnose it

• 12-lead ECG. Often diagnostic on its own, especially for higher grades of block.
• Holter or patch monitor. When block is intermittent. We look at how often non-conducted beats happen, whether they cluster at night versus during the day, and how the block behaves with exertion.
• Exercise treadmill test. A particularly useful test — block that worsens with exercise points strongly to a problem below the AV node and lowers our threshold to pace.
• Implantable loop recorder. For unexplained fainting where intermittent AV block is on the differential.
• Electrophysiology study. Used when we need to know exactly where the block sits.

We also look hard at reversible causes: medications (beta-blockers, calcium channel blockers, digoxin, certain antiarrhythmics), electrolyte abnormalities, ischemia, Lyme disease, sarcoidosis, and recent cardiac surgery. If a clear reversible cause is found and corrected, the block sometimes resolves entirely.

How we treat it

Observe

First-degree block and asymptomatic Mobitz I are observed. We address any contributing medications and follow over time.

Pacemaker

Recommended for:

• Symptomatic second-degree block of any type.
• Mobitz II AV block, even without symptoms.
• High-grade AV block.
• Third-degree (complete) AV block.
• Block that worsens with exercise.

In most patients with AV block we choose a dual-chamber pacemaker so we can pace the ventricle when the atrial impulse fails to make it through, while still tracking and preserving the heart’s own atrial rhythm. For some patients, particularly when extensive ventricular pacing is expected, we consider conduction-system pacing (His-bundle or left-bundle-branch-area pacing) to preserve a more natural pattern of ventricular activation.

What to expect at your visit

We’ll go over symptoms — fatigue, breathlessness, lightheadedness, any fainting — and any monitor or ECG findings that brought you in. We’ll examine you, review medications carefully, and decide whether more testing is needed or whether the picture already supports pacing. When a pacemaker is recommended, we’ll walk through what type, what the procedure involves, and what life looks like afterward.

What is happening when we faint

Consciousness depends on a steady supply of oxygenated blood to the brain. When that supply briefly falls — even for just six to ten seconds — we lose consciousness. The body lies down (or falls down), gravity restores blood flow to the head, and consciousness returns within seconds. That whole sequence is syncope.

The interesting question is always: why did blood flow to the brain drop in the first place? The cause sorts into a few broad categories.

Reflex (vasovagal) syncope

By far the most common. A trigger — pain, the sight of blood, prolonged standing, heat, dehydration, strong emotion — sets off an overactive reflex through the vagus nerve. The reflex slows the heart, opens up blood vessels in the legs, and pools blood away from the brain. Most people get clear warning: lightheadedness, tunnel vision, nausea, sweating, ringing in the ears, a feeling of being far away. Then they go down. They usually wake up within seconds, feel washed out for an hour or so, and recover fully.

Orthostatic syncope

The blood pressure drops on standing up, especially after sitting or lying for a while. Often related to dehydration, blood-pressure medications, blood loss, or autonomic-nervous-system problems (sometimes from diabetes or Parkinson’s disease).

Cardiac syncope

This is the group we have to identify. The mechanism is either a heart rate that’s suddenly too slow (a pause, advanced AV block, sinus arrest) or a heart rhythm that’s suddenly too fast and pumping ineffectively (ventricular tachycardia, less commonly very rapid SVT). Sometimes the cause is structural — severe aortic stenosis, hypertrophic cardiomyopathy, or pulmonary embolism. Cardiac syncope carries a higher risk of sudden death if left undiagnosed, so we look carefully.

Warning signs that point toward a cardiac cause

We pay extra attention when fainting is:

• Sudden, with no warning — the patient drops without lightheadedness, nausea, or sweating.
• During exertion — particularly during peak exercise rather than after finishing.
• Preceded by palpitations or chest pain.
• Associated with injury because there was no time to brace or sit down.
• Happening while supine — lying flat almost rules out a vasovagal mechanism.
• In a patient with known heart disease, a low ejection fraction, or a family history of sudden cardiac death.

A faint in a young person at the sight of a needle, with a long warning, in an upright posture, that recovers fully in a minute, is almost always vasovagal. A faint in an older patient during stair climbing, with no warning, causing facial injury, is a different story.

How we diagnose it

We start with the history — which often does most of the diagnostic work — followed by a physical exam, a 12-lead ECG, and an echocardiogram in most patients to look at heart structure and pump function. From there:

• Holter or patch monitor. For frequent symptoms (every week or two).
• Mobile cardiac telemetry. For longer monitoring with real-time alerts.
• Implantable loop recorder (ILR). A small device about the size of a paper clip placed under the skin of the chest. It records the heart rhythm for up to three years and is invaluable for syncope that happens rarely.
• Tilt-table test. The patient is strapped to a table that tilts upright for 30–45 minutes while we watch the heart rate and blood pressure. Useful when we suspect vasovagal or orthostatic syncope but the picture isn’t classic.
• Electrophysiology study. Reserved for patients with structural heart disease or a high suspicion of a tachyarrhythmia.
• Exercise testing. When syncope is exertional.

How we treat it

Vasovagal and reflex syncope

Most patients do very well with non-medical strategies: generous fluid intake, liberal salt (if blood pressure allows), avoiding triggers, and learning counter-pressure maneuvers — crossing the legs, tensing the thigh and abdominal muscles, gripping a fist — at the first warning sign. Medications and, rarely, pacing are reserved for severe, recurrent, injury-causing episodes.

Orthostatic syncope

Hydration, salt, slower position changes, compression stockings, review of blood-pressure medications, and occasionally medications that raise standing blood pressure.

Cardiac syncope

Treatment targets the underlying rhythm or structural problem: a pacemaker for symptomatic bradycardia or high-grade AV block, an ICD for a documented or strongly suspected dangerous ventricular arrhythmia, and structural treatment for valve or muscle disease.

What to expect at your visit

We’ll spend most of our time on the story — what you were doing in the minutes before, what (if any) warning you had, what witnesses saw, and how you felt afterward. Bring anyone who saw the event if you can. We’ll review your ECG and any prior records, examine you, and decide whether more monitoring or testing is needed. The goal is always to sort benign from worrisome confidently — and then either reassure you or treat the cause directly.

What a pacemaker does

A pacemaker has two jobs: sense the heart’s own electrical activity, and pace when the heart’s rate falls below a programmed threshold. When the heart beats normally, the pacemaker stays quiet — it only fires when needed. Most modern pacemakers also collect detailed diagnostics we can review at follow-up visits.

The current FDA-approved pacemaker systems in the United States fall across three categories: traditional transvenous devices (Medtronic Azure / Astra, Abbott Assurity, Boston Scientific Accolade / Resonate), leadless devices (Medtronic Micra, Abbott Aveir), and CRT-P resynchronization devices (Medtronic Cobalt HF / Crome HF, Abbott Quadra Assura / Quadra Allure, Boston Scientific Resonate HF).

Who needs one

Pacemakers are recommended when the heart’s own electrical system can’t reliably deliver a normal heart rate, and that’s causing symptoms or is dangerous on its own. The two most common reasons are:

• Sinus node dysfunction — the heart’s natural pacemaker is sluggish or pauses, especially with exertion (the heart can’t speed up appropriately) or with certain medications.
• AV block — the electrical signal from the atria can’t reliably reach the ventricles. High-grade AV block always needs pacing; lesser degrees depend on symptoms.

We do not implant pacemakers for fast heart rhythms or for irregular rhythms like AFib alone — those are treated differently.

The three main types

Transvenous (traditional)

The most common design. A small generator (about the size of a large coin) is placed under the skin just below the collarbone. One or two thin insulated wires (leads) are threaded through a vein into the heart and fixed in place. This is what most people picture when they hear “pacemaker.”

• Single-chamber — one lead, usually in the right ventricle. Often chosen when the patient has chronic atrial fibrillation and ventricular pacing alone is sufficient.
• Dual-chamber — two leads, one in the right atrium and one in the right ventricle. Preserves the natural sequence of atria-then-ventricles contraction. This is the most common configuration.

Leadless

A self-contained capsule, roughly the size of a multivitamin, placed entirely inside the right ventricle through a catheter from a leg vein. There is no chest incision, no pocket under the skin, and no lead. Leadless pacemakers are an excellent option when single-chamber ventricular pacing is enough. Newer leadless systems can also communicate with a second device in the atrium to provide dual-chamber pacing.

CRT-P (cardiac resynchronization therapy — pacemaker)

A specialized pacemaker for patients with heart failure and a wide QRS pattern on ECG (an electrical delay between the left and right ventricles). It uses an extra lead that paces the left ventricle through a coronary vein, restoring coordinated contraction. CRT-P improves symptoms and survival in selected heart-failure patients. (CRT can also be combined with a defibrillator — that version is called CRT-D and is covered in the ICD section.)

What life is like after implant

For most people, very little changes day-to-day. After the initial healing period (about 4–6 weeks of avoiding heavy lifting and overhead arm motion on the implant side), normal activity resumes. The device is checked at a wound visit, then in clinic, and afterward via remote monitoring — your device transmits data from home automatically. Some hospitals embed MRI compatibility in modern pacemakers, but we always verify before any MRI is scheduled.

Most patients only feel the device occasionally — when it paces hard, or when it’s checked in clinic. The vast majority of pacemaker recipients report a significant improvement in symptoms — particularly fatigue, exertional shortness of breath, and presyncope.

Practical details after implant

A few specifics that come up in nearly every post-implant conversation:

• Lifting and arm motion. Avoid lifting more than ten pounds with the arm on the implant side for the first four weeks, and avoid raising that arm above shoulder level — this lets the leads scar in and settle. After four weeks, gradually return to normal activity. Day-to-day movements (driving, light cooking, shampooing your hair) are fine from day one.
• The wound dressing. You’ll go home with a clear plastic dressing that looks a bit like kitchen wrap. Leave it in place; we’ll remove it at your wound-check visit in one to two weeks. A small amount of discoloration or dried blood underneath is normal. Do not pull the edges off.
• When to call us. Fever of 102°F or higher, dramatic swelling at the incision site (think the size of an orange), unusual pain, lightheadedness, or any sensation that the device is moving — call the office. None of these are common, but each one is the kind of thing we want to hear about right away rather than at the next scheduled visit.
• Home monitoring. A bedside transmitter or a smartphone app pairing will be arranged in the weeks after implant. We’ll show you how it works; from then on the device sends its data home automatically, and we usually have the information before any office visit.
• Airport security. Modern airport metal detectors will reveal your device. You’ll receive a manufacturer-issued device-identification card; carry it in your wallet and present it to screening personnel. Walking through the detector is generally fine; many patients prefer to request a hand search to avoid the small chance of interference.
• MRI and strong magnetic fields. Today’s pacemakers are designed to be MRI-conditional, but every scan needs to be cleared by us first — the scanner has to be set up correctly and the device reprogrammed for the scan and back. Avoid close proximity to industrial-strength magnets, arc welders, and large speaker magnets. Ordinary cell phones, microwaves, and household electronics are not a problem.

Manufacturer reference

For technical specifications, indications, and the latest official information on the pacemaker systems referenced above, see the manufacturers’ product pages:

• Medtronic pacemakers
• Medtronic Micra leadless pacemaker
• Abbott pacemakers
• Boston Scientific pacemakers

(External links — content is each manufacturer’s and may be technical.)

Further reading

Patient resources from the American Heart Association:

• What Is a Pacemaker? — AHA Answers by Heart — a two-page plain-English fact sheet covering why pacemakers are used, life after implant, and household-electronics guidance
• Pacemaker — AHA animation library — pick “Pacemaker” from the topic menu for an animated explanation of how a pacemaker senses your heart’s rhythm and steps in when needed

What an ICD actually does

An ICD is a small, computerized device — about the size of a small pager — that sits under the skin near the collarbone and connects to the heart through one or two insulated wires (leads). It is constantly listening to every heartbeat. When the rhythm looks normal, it does nothing. When the heart goes into a dangerously fast rhythm from the lower chambers — ventricular tachycardia (VT) or ventricular fibrillation (VF) — the device steps in within seconds to restore order.

It has two ways of doing that. The first is anti-tachycardia pacing (ATP) — a quick burst of painless pacing that often interrupts VT before a shock is needed. Many patients with an ICD have episodes treated entirely by ATP and never feel a thing. The second is a shock — a strong, brief jolt of energy delivered through a coil on the lead, which resets the heart’s electrical activity. A shock is the backup when the rhythm is too fast or chaotic for pacing to fix.

If the heart is too slow, the same device also paces — so an ICD includes everything a pacemaker can do.

The major FDA-approved transvenous ICD platforms currently used in the United States are the Medtronic Cobalt / Crome, Abbott Gallant, and Boston Scientific Resonate / Momentum families.

Single chamber vs dual chamber

A single-chamber ICD has one lead anchored in the right ventricle. It’s the simplest configuration and works well when the only job is to watch the ventricles.

A dual-chamber ICD adds a second lead in the right atrium. The atrial lead helps in two situations: it preserves the natural atria-then-ventricles pacing sequence if pacing is needed, and — importantly — it gives the device extra information to distinguish a fast rhythm coming from the atria (like atrial fibrillation with a rapid response) from a true ventricular rhythm. That helps avoid inappropriate shocks. We choose between the two based on your underlying rhythm and pacing needs.

Primary vs secondary prevention

This distinction shapes the whole conversation. Primary prevention means we recommend an ICD because the risk of sudden cardiac death is high — most commonly because the heart muscle is weakened (ejection fraction at or below 35%) and is not expected to recover with medications alone. The device is put in before a life-threatening event happens.

Secondary prevention means a dangerous rhythm has already occurred — a cardiac arrest you survived, sustained VT, or unexplained fainting with structural heart disease — and we are protecting against the next one. The bar for an ICD here is lower because we already know the risk is real.

What a shock feels like

Patients describe it differently — most commonly as a sharp kick or thump in the chest, sometimes painful for a moment but always brief. Because VT and VF often cause lightheadedness or loss of consciousness, many people don’t actually feel the shock at all — they wake up afterward feeling shaken but alive. If you receive a shock and feel fine afterward, call us within 24 hours. If you receive multiple shocks in a row or don’t feel right, that’s a 911 call.

Driving rules

Driving restrictions exist because losing consciousness behind the wheel is dangerous to you and to others. For primary prevention implants without prior events, most patients can drive a private vehicle after about a week. For secondary prevention — or after any appropriate shock — we typically ask patients to avoid driving for several months. Commercial driving rules are stricter. We go over the specifics that apply to your situation and your state at the time of implant and after any therapy.

Remote monitoring and life with the device

The device sends data from home automatically using a small bedside transmitter or a smartphone app. We see information about your rhythms, the device’s battery, and lead performance — usually before any symptom would bring you in. In-person device checks happen once or twice a year, with remote transmissions in between.

Day-to-day, most patients forget the device is there. MRI compatibility is now standard for modern systems but we always verify before any scan is scheduled. Strong magnetic fields (industrial equipment, arc welders, large speaker magnets at close range) should be avoided; ordinary household electronics, airport security, and cell phones are not a problem.

Practical details after implant

A few specifics worth knowing in the weeks after:

• Lifting and arm motion. Avoid lifting more than ten pounds with the arm on the implant side for the first four weeks, and keep that arm below shoulder level — the leads need that time to anchor in. Normal day-to-day motion (driving, light cooking, shampooing your hair) is fine from day one. After four weeks, gradually return to normal activity.
• The wound dressing. You’ll go home with a clear plastic dressing over the incision. Leave it in place; we remove it at the wound-check visit in one to two weeks. A small amount of discoloration or dried blood underneath is normal. Do not peel the edges off.
• When to call us — non-shock issues. Fever of 102°F or higher, dramatic swelling at the incision site, unusual pain, lightheadedness, or any sensation that the device is moving. (Shock guidance is in the section above — one shock with you feeling fine afterward is a same-day phone call; multiple shocks or not feeling right is a 911 call.)
• The home transmitter. Your remote-monitoring transmitter or smartphone app pairing will be set up shortly after implant. From then on, the device sends data home automatically — we’ll usually see episodes before you call us about them.
• Airport security and the wallet card. You’ll receive a manufacturer-issued device-identification card in the weeks after implant. Carry it in your wallet and present it to airport screening personnel. Walking through metal detectors is generally fine; many patients prefer to request a hand search to avoid even the small chance of interference.

Manufacturer reference

For technical specifications, indications, and the latest official information on the transvenous ICD platforms referenced above, see the manufacturers’ product pages:

• Medtronic ICDs
• Abbott ICDs
• Boston Scientific ICDs

(External links — content is each manufacturer’s and may be technical.)

Further reading

Patient resources from the American Heart Association:

• What Is an Implantable Cardioverter Defibrillator (ICD)? — AHA Answers by Heart — a two-page plain-English fact sheet on how an ICD works, what to expect after implant, and living with the device
• Implantable Cardioverter Defibrillator — AHA animation library — pick “Implantable Cardioverter Defibrillator” from the topic menu for an animated explanation of how the ICD detects dangerous rhythms and delivers therapy

What makes the S-ICD different

A traditional ICD relies on a lead — a long insulated wire — that runs from the device, through a vein under the collarbone, and into the heart. That lead is what makes the device powerful: it can sense beats directly, pace, and deliver anti-tachycardia pacing as well as shocks. But that lead is also where most of the long-term trouble with ICDs comes from. Leads can fracture, infect, and become very difficult to remove years later because they scar into the vein and heart wall.

The S-ICD was designed to solve that problem by keeping everything outside the bloodstream. The generator sits in a pocket on the left side of the chest, under the arm. A single lead is tunneled in a Z-shape under the skin — across to the breastbone, then up alongside it. When the device detects a dangerous rhythm, it delivers a shock between a coil on that lead and the generator itself, sending the energy across the chest and through the heart.

Nothing ever enters a vein or heart chamber.

The currently FDA-approved subcutaneous ICD system in the United States is the Boston Scientific EMBLEM MRI S-ICD.

The trade-off: no pacing, no ATP

The S-ICD’s biggest strength is also its biggest limitation. Because the lead never touches the heart, the device cannot reliably pace from outside the chest wall for any length of time — it can only deliver very brief external-style pacing immediately after a shock, and it cannot deliver anti-tachycardia pacing (ATP), the painless pacing burst that often stops VT without a shock.

That means the S-ICD is best for patients who:

• Need protection against sudden cardiac death.
• Do not need long-term pacing for slow heartbeats.
• Have a type of VT that doesn’t tend to respond to ATP, or have not had documented VT at all (most primary-prevention patients).

If you have known slow-rhythm problems, a high pacing need, or VT that has been treated successfully by ATP in the past, a transvenous or EV-ICD is usually the better fit.

Why we screen with an EKG first

Because the S-ICD watches the heart from the surface — not from inside it — the signal it sees is smaller and noisier than a wire’s view from within the heart. To make sure the device can reliably tell the difference between a normal beat and a dangerous one, we do a special screening EKG before implant. We record from several body positions (sitting, standing, sometimes during light exercise) and check that the signal is clean in at least one of the device’s possible sensing vectors. A small number of patients — often those with very unusual T-waves on their EKG — fail screening, and in those cases we recommend a transvenous or EV-ICD instead.

Who tends to do especially well with an S-ICD

• Younger patients with many decades of device-life ahead, where avoiding lead-related complications matters most.
• Patients with prior device infections — a clean, vein-free system reduces re-infection risk.
• Patients on dialysis or with limited venous access, where preserving veins is critical.
• Patients with congenital heart disease whose anatomy makes transvenous lead placement difficult.

What a shock feels like

Because the shock energy crosses more tissue (skin, muscle, then the heart) than a transvenous shock, S-ICD shocks tend to feel more substantial — most patients describe a hard thump or a kick to the chest. The duration is the same: a single, brief moment. Most appropriate shocks are followed by an immediate sense of feeling unwell for a few seconds, then relief that the rhythm is back to normal. If you receive a shock and feel okay afterward, call us within 24 hours. Multiple shocks or feeling unwell after a shock should prompt a 911 call.

Living with an S-ICD

The device is larger and more lateral than a transvenous ICD — some patients can feel a slight bulge on the side of the chest, particularly when lying on that side. Remote monitoring works the same way as with a transvenous system: data is sent from home automatically, and we usually see episodes before you would think to call.

Battery life is somewhat shorter than transvenous ICDs because the device works harder to sense and to shock from outside the heart. When the time comes, only the generator is replaced through the same incision — the lead is left in place if it’s still working well.

Manufacturer reference

For technical specifications, indications, and the latest official information on the EMBLEM MRI S-ICD system from its maker, see Boston Scientific’s product page: EMBLEM S-ICD System on bostonscientific.com. (External link — content there is Boston Scientific’s and may be technical.)

What a loop recorder is for

Some of the most important questions in cardiac electrophysiology are simply: what is the heart doing when the patient is having symptoms? If the symptom happens every day, a 24-hour Holter often answers it. If it happens every couple of weeks, a 2-week patch monitor usually does. But many symptoms come around once every few months — or even less — and short-term monitors miss them. That’s the gap an implantable loop recorder is built to fill.

The device sits under the skin and watches the heart continuously for about three years. It stores abnormal rhythms automatically based on programmed criteria, and the patient can also press a button on a handheld activator (or tap a button in the app) whenever they feel a symptom — that flags the surrounding minutes of recording for us to review.

The current FDA-approved implantable loop recorder we use in the United States is the Medtronic LINQ II.

Common reasons we use one

Unexplained syncope (fainting). When a careful workup hasn’t found the cause, a loop recorder is often the next step. In roughly half of these patients, the device captures the answer within the first year — sometimes a long pause, sometimes a fast rhythm, sometimes a perfectly normal rhythm during a faint (which itself is a very useful answer, because it points away from a heart-rhythm cause).

Cryptogenic stroke. When someone has a stroke and no clear source is found on routine workup, paroxysmal atrial fibrillation is one of the most common hidden causes. Catching it changes management — usually by starting an anticoagulant. Long-term monitoring with a loop recorder finds AFib in roughly one in three patients with cryptogenic stroke over a few years, far more than short monitors do.

Atrial fibrillation surveillance. After an AF ablation, in patients with infrequent palpitations, or in patients whose AF burden we want to track over time, a loop recorder gives a continuous view that no wearable can match.

Unexplained palpitations. When palpitations are infrequent but troubling, and short-term monitoring hasn’t caught the event, a loop recorder usually settles the question.

The implant itself

This is one of the simplest implants we do. After numbing a patch of skin just to the left of the breastbone, we make a small incision and slide the device into a pocket directly beneath the skin using a special inserter. There is no lead, no vein access, and no X-ray needed. The whole procedure is usually done in about 20–30 minutes, often in the office, and the patient is up and walking out the same hour.

The device sits horizontally just under the skin and is barely visible in most people. After the small incision heals (usually a week or two), most patients forget the device is there.

How we get the data

A small bedside transmitter — or, with the newest systems, a smartphone app — pairs with the device wirelessly. It downloads any stored episodes automatically, usually overnight, and sends them to a secure server we review. If something significant is found, the system alerts us, and we reach out. Patients can also press an activator button when they feel a symptom; that recording is uploaded the same way.

In-person checks are uncommon — usually only at implant, sometimes once midway through the device’s life if questions arise, and then at removal.

Battery life and removal

The battery lasts about three years in most cases. When the device reaches the end of its useful life — or when we have the answer we were looking for — we remove it. Removal is straightforward: local anesthesia, a small incision over the device, slide it out, close. This is typically also a 20-minute office visit.

If the loop recorder catches a rhythm that requires treatment — a long pause needing a pacemaker, atrial fibrillation needing a blood thinner, or a fast rhythm needing further evaluation — we plan that next step based on what the device has shown.

What the loop recorder can’t do

It listens, but it doesn’t treat. The device cannot pace, cannot shock, and cannot deliver medication. Its value is entirely in showing us what the rhythm is during a symptom — and in many cases, that single piece of information changes the entire treatment plan.

Manufacturer reference

For technical specifications, indications, and the latest official information on the loop recorder systems referenced above, see the manufacturers’ product pages:

• Medtronic LINQ II

(External links — content is each manufacturer’s and may be technical.)

A practical triage card. Tear this page out and put it on the fridge if it helps.

This handbook is educational. It does not create a doctor-patient relationship and does not replace your visits. Your situation may differ — talk to Dr. Colombowala or your treating physician before making decisions about your care.

© 2026 Ilyas K. Colombowala, MD. All rights reserved. Reproduction, redistribution, or republication of this material in any form without written permission is prohibited.