Cardiac-resynchronization therapy in heart failure with narrow QRS complexes

Area of Science:

• Cardiology
• Medical Devices
• Heart Failure Management

Background:

• Cardiac-resynchronization therapy (CRT) is indicated for heart failure patients with prolonged QRS intervals (≥120 msec).
• Some heart failure patients with narrow QRS complexes exhibit left ventricular mechanical dyssynchrony and might benefit from CRT.

Purpose of the Study:

• To evaluate the efficacy of CRT in patients with moderate-to-severe heart failure, specifically assessing its impact on exercise capacity.
• To determine if CRT offers benefits in patients with narrow QRS intervals.

Main Methods:

• 172 patients with standard implantable cardioverter-defibrillator indications were enrolled.
• Patients were randomized to receive CRT or no CRT for 6 months.
• The primary endpoint was the proportion of patients showing at least a 1.0 ml/kg/min increase in peak oxygen consumption.

Main Results:

• No significant difference in peak oxygen consumption improvement was observed between the CRT and control groups (46% vs. 41%).
• In patients with QRS intervals ≥120 msec, peak oxygen consumption increased with CRT (P=0.02).
• Patients with QRS intervals <120 msec showed no change in peak oxygen consumption with CRT (P=0.45).

Conclusions:

• CRT did not improve peak oxygen consumption in patients with moderate-to-severe heart failure.
• Evidence suggests that heart failure patients with narrow QRS intervals may not benefit from CRT.