Which combination of characteristics is typically used to determine CRT eligibility?

• A. QRS duration ≥ 120 ms
• B. All of the above
• C. EF ≤ 35%
• D. NYHA II-IV

Answer: (B)

CRT is considered for patients with heart failure who have both electrical dyssynchrony and reduced pumping function, and who still have symptoms. The key criteria are reduced ejection fraction (≤35%), indicating systolic dysfunction; a widened QRS complex (≥120 ms), reflecting interventricular dyssynchrony; and NYHA class II–IV symptoms, showing functional limitation despite therapy. When all three are present, the patient is most likely to benefit from resynchronization, because the device can coordinate the timing of ventricular contractions to improve overall heart efficiency and reduce adverse outcomes. Clinicians may also consider QRS pattern (like left bundle branch block) and ensure optimal medical therapy, but the combination of reduced EF, prolonged QRS, and symptomatic status is the typical basis for CRT eligibility.