Cardiac Electrophysiology and Heart Failure Practice Test

The main idea is how ICDs are used to prevent sudden death in systolic heart failure: who gets them to prevent a first event (primary prevention) versus who already had a dangerous rhythm and needs protection from recurrence (secondary prevention).

Primary prevention is for patients with substantial LV dysfunction who have not yet had a VT storm or cardiac arrest. The key clinical trigger is an ejection fraction of 35% or less, despite optimized medical therapy, and this applies to both ischemic and nonischemic cardiomyopathy. The goal is to prevent a first sudden death by providing timely device therapy if a dangerous rhythm occurs.

Secondary prevention, on the other hand, is for those who have already survived a life-threatening arrhythmia, such as sudden cardiac arrest or sustained VT. In these patients, an ICD is indicated to reduce the risk of recurrence and further sudden death, independent of current EF, though EF still helps guide broader management.

An important nuance is that in ischemic disease, revascularization can improve EF. If EF rises above the threshold after revascularization and optimization, the primary-prevention indication may no longer apply; if EF remains ≤35%, the patient continues to meet primary-prevention criteria. The other statements don’t align with these thresholds and the role of ablation, which isn’t the deciding factor for primary versus secondary prevention, so they’re not the correct framing.