What is happening in the heart
The ventricles are supposed to squeeze in one coordinated motion — top to bottom, side to side, all in roughly a tenth of a second. In heart failure with reduced ejection fraction (HFrEF), the muscle has been weakened, usually by a prior heart attack, long-standing high blood pressure, viral injury, alcohol, chemotherapy, or a genetic cardiomyopathy. The ventricles dilate and pump less of their volume out with each beat.
On top of weakened contraction, many of these patients also develop an electrical delay — most often a left bundle branch block. When the left bundle is blocked, the right ventricle squeezes first and the left ventricle follows several tenths of a second later. The two chambers fight each other instead of cooperating, and the heart’s output drops further.
Why it matters
Two distinct risks travel together in HFrEF:
- Pump failure. Fluid backs up into the lungs and legs; exercise capacity falls; hospitalizations climb.
- Sudden death. A weakened, scarred ventricle is electrically unstable. Sustained ventricular tachycardia and ventricular fibrillation are far more common when EF is reduced, and they can occur in patients who otherwise feel relatively well.
A complete plan addresses both.
How we diagnose and risk-stratify
We start with two cornerstones: an echocardiogram to measure EF and look at the chambers and valves, and a 12-lead ECG to measure the QRS width and look for bundle branch block. Bloodwork (including BNP), a stress test, sometimes a cardiac MRI, and occasionally a coronary angiogram round out the workup. We also screen for sleep apnea, anemia, kidney dysfunction, and thyroid disease — all of which can worsen heart failure.
The two numbers I quote most often:
- EF below 35% — defines high enough sudden-death risk to discuss a primary-prevention ICD after a few months of guideline-directed therapy.
- QRS width of 150 ms or more, especially with a left bundle branch pattern — defines the patients most likely to benefit from CRT.
How we treat it
Medications first
The foundation is always guideline-directed medical therapy — four classes of drugs working together: beta-blockers, an ACE inhibitor / ARB / ARNI, an aldosterone antagonist, and an SGLT2 inhibitor. These medications genuinely change the course of disease. Many patients see their EF improve significantly with just months of consistent therapy, and we always give the medications time to work before committing to a device.
Cardiac resynchronization therapy (CRT)
CRT is a special kind of pacemaker that places an extra lead on the left ventricle — usually through a branch of the coronary venous system on the back of the heart. By pacing both ventricles together (and ahead of the natural delayed signal), CRT restores coordinated contraction. In the right patient, the benefits include:
- Improved exercise capacity and quality of life
- A meaningful rise in ejection fraction over months
- Fewer heart-failure hospitalizations
- A survival benefit
We see the biggest response in patients with a wide left bundle branch block, sinus rhythm, and an EF at or below 35% despite optimal medications. Women, and patients with non-ischemic causes of cardiomyopathy, tend to respond especially well.
Defibrillator (ICD) decisions
ICDs come into play when the goal is preventing sudden death:
- Secondary prevention — anyone who has already survived a sustained VT or cardiac arrest from a structural cause.
- Primary prevention — patients with EF at or below 35% after at least three months of optimal medical therapy. We look hard at whether EF has recovered before committing to a long-term device.
CRT-D versus CRT-P
If a patient needs CRT and meets criteria for an ICD, the two functions are combined in a single device called CRT-D — a biventricular pacemaker with defibrillation built in. If the only goal is resynchronization (for example, in an older patient with significant comorbidities where the defibrillator burden outweighs the benefit), we choose CRT-P without the defibrillator.
Newer pacing options
For some patients, left bundle branch area pacing — placing a single lead directly into the heart’s wiring — is now a strong alternative to traditional CRT, particularly when coronary venous anatomy is unfavorable.
What to expect at your visit
We’ll review your EF, ECG, and medication list and figure out where you are in the staircase: medications still being optimized, ready for CRT, ready for an ICD, or both. We do not rush to a device — getting the medications right first often changes the picture. When a device is the right answer, we walk through the procedure, the expected benefit, and what life looks like with remote monitoring afterward.