What beta-blockers do
Your heart is wrapped in a network of nerves that carry adrenaline signals. When those signals reach beta receptors on heart cells, the heart speeds up and contracts more forcefully. Beta-blockers sit on those receptors and block the signal — the heart slows down, the contraction softens, and the electrical system becomes less excitable. The blood pressure also drops modestly.
This is useful in a lot of situations: when the heart is racing in AF, when an SVT is hard to control, when ventricular arrhythmias are triggered by adrenaline, or when an inherited rhythm condition makes the heart vulnerable to sudden adrenaline surges.
The beta-blockers we use most often
There are a lot of beta-blockers, but in electrophysiology we use a few regularly:
- Metoprolol — comes as immediate-release (tartrate, dosed two to three times a day) and extended-release (succinate, once daily). Selective for the heart’s beta-1 receptors, so it’s gentler on the lungs.
- Carvedilol — blocks both beta and alpha receptors. We use it especially when heart failure with reduced ejection fraction is in the picture, because of strong evidence in that population.
- Atenolol — older, beta-1 selective, once or twice daily. Cleared by the kidneys, so the dose depends on kidney function.
- Bisoprolol — beta-1 selective, once daily, well-tolerated, and another good option in heart failure.
- Nadolol — long-acting, non-selective. We reach for this one specifically in long QT syndrome and catecholaminergic polymorphic VT (CPVT), where its long duration and non-selectivity matter.
- Propranolol — non-selective, used in some inherited arrhythmias and for symptom control.
Who we prescribe them for
The main uses in our practice:
- Rate control in AF and atrial flutter — slowing the ventricular response so the heart doesn’t race during episodes. Often the first drug we add.
- Symptom control in SVT — reducing the frequency or severity of episodes, particularly while we plan ablation.
- Long QT syndrome — nadolol or propranolol blunts the adrenaline surges that trigger dangerous rhythms.
- CPVT — same logic; nadolol is standard.
- Frequent PVCs (premature ventricular contractions) that are symptomatic.
- After a heart attack — protective, separate from arrhythmia use.
- Heart failure with reduced ejection fraction — carvedilol, metoprolol succinate, and bisoprolol are evidence-based here.
How we titrate
We almost always start at a low dose and work up. The goal is a heart rate that feels reasonable at rest (usually 60–80) and doesn’t shoot too high with normal activity. Many patients need a few dose adjustments before we land on the right number.
For inherited arrhythmias, the right dose is one that meaningfully blunts your heart rate response to exercise — we often confirm with a stress test.
Side effects to watch for
Most patients tolerate beta-blockers well. Common things:
- Fatigue, particularly in the first few weeks — this often improves as the body adjusts.
- Cold hands and feet — from reduced peripheral circulation.
- Slow heart rate (bradycardia) — sometimes too slow, particularly in athletic patients or with high doses.
- Light-headedness on standing — from the modest blood-pressure effect.
- Sexual dysfunction — particularly with older, non-selective drugs.
- Vivid dreams or sleep disturbance — more common with lipophilic agents like metoprolol and propranolol.
- Worsened wheezing in asthma or COPD — especially with non-selective drugs. We choose selective beta-blockers in this situation.
- Masking of low blood sugar symptoms in diabetes — patients on insulin should know that the heart-racing warning of hypoglycemia may be blunted.
What not to do
Never stop a beta-blocker abruptly if you have been on it for more than a few weeks. The body upregulates beta receptors during chronic use, and sudden withdrawal can cause a rebound — racing heart, high blood pressure, chest pain. If we need to stop, we taper over a week or two.
Drug interactions
A few combinations need attention:
- Calcium channel blockers (diltiazem, verapamil) — combination meaningfully slows the heart rate and AV conduction. We sometimes use both deliberately, but at lower doses and with closer monitoring.
- Other rhythm drugs — generally compatible but the cumulative slowing effect needs watching.
- Clonidine — combination can cause significant bradycardia, and stopping clonidine while on a beta-blocker can cause a hypertensive surge.
There are no specific dietary restrictions.
Monitoring
We check heart rate and blood pressure at follow-up. Periodic ECGs confirm the rhythm and rate. For carvedilol or metoprolol succinate in heart failure, we follow ejection fraction over time.
When to call us
Call about pulse under 50 with symptoms, fainting or near-fainting, new shortness of breath, new wheezing, or significant fatigue that doesn’t settle.