Survival After Rate-Responsive Programming in Patients With Cardiac Resynchronization Therapy-Defibrillator Implants Is Associated With a Novel Parameter

Cardiac resynchronization therapy (CRT) has been shown to improve quality-of-life, functional status, exercise capacity, and survival in patients with left ventricular systolic dysfunction, moderate to severe heart failure symptoms, and a wide QRS. Controlled, randomized CRT trials have used atrial sensing to provide atrial-synchronized biventricular pacing, but have not focused on atrial pacing or rate response. Current CRT devices are capable of atrial pacing for atrial rate support and rate-responsive pacing (DDDR), and these are 2 commonly programmed modes in CRT devices. However, no randomized prospective clinical trial has shown survival benefit from these pacing modes. Increasing heart rate through atrial support pacing in heart failure patients can increase cardiac output. However, higher resting and mean heart rates are associated with increased mortality. In a heart failure population, although lower resting rates are associated with better outcomes, no one has specifically considered outcomes in those with lower resting heart rates but better heart rate response with exercise. Similarly, in an implantable cardioverter defibrillator (ICD) population, the mean heart rate predicts outcomes of heart failure hospitalization and total mortality, but this generally represents resting rate and does not provide information about heart rate changes with exertion or in other circumstances. Chronotropic incompetence, either pathophysiologic or iatrogenic (eg, β-blocker therapy), is common in heart failure patients. In these patients, it is reasonable to suspect that the hemodynamic benefits of biventricular pacing may be enhanced by increasing atrial rates with increased physical demands. Large, remote monitoring databases offer the opportunity to assess associations between programming parameters and clinical outcomes. A novel parameter, the heart rate score (HRSc),