Cardiac resynchronization therapy during rest and exercise: comparison of two optimization methods

Abstract

Aims: Optimal exercise programming of cardiac resynchronization therapy (CRT) devices is unknown. We aimed to: (i) investigate variations in optimal atrioventricular (AV) and interventricular (VV) delays from rest to exercise, assessed by both echocardiography and an automated intracardiac electrogram (IEGM) method; (ii) evaluate the acute haemodynamic impact of CRT optimization performed during exercise.

Methods and results: Twenty-four heart failure patients, previously implanted with a CRT defibrillator, underwent AV and VV delay optimization, by echocardiography and IEGM methods, both at rest and during supine bicycle exercise. Rest-to-exercise variations in optimal VV delay were observed in 58% of patients. Conversely, optimal AV delay did not change during exercise compared with rest. Substantial agreement of AV and VV delays was observed between both the optimization methods. Exercise optimization of VV delay by either method improved intraventricular dyssynchrony and increased aortic velocity time integral compared with the resting setting (P < 0.001).

Conclusion: In patients implanted with a CRT device, optimal VV delay varied considerably from rest to exercise, while AV delay did not change. Re-assessment of the optimal pacing configuration during supine exercise, by echocardiography as well as IEGM methods, yielded an additional haemodynamic benefit to that provided by resting optimization.

Figure 1

Boxplot (25th–75th percentile), median values (open squares) and outliers (open circles) showing distributions in septal-to-lateral delay during intrinsic rhythm (without biventricular stimulation) and during cardiac resynchronization therapy with intracardiac electrogram and echo-optimized atrioventricular and interventricular delays, both at rest and during exercise. IEGM, intracardiac electrogram; ECHO, echocardiogram; biv, biventricular pacing.

Figure 2

Plot of septal-to-lateral delay after echocardiographic vs. IEGM optimization of atrioventricular and interventricular delays. The left part refers to rest and the right to exercise. The relative frequencies of the number of data represented by a single plot position are indicated with circles of varying sizes. IEGM, intracardiac electrogram; ECHO, echocardiogram.

Figure 3

Boxplot (25th–75th percentile), median values (□) showing distributions in LVOT VTI during intrinsic rhythm (without biventricular stimulation) and during cardiac resynchronization therapy with IEGM and echo-optimized atrioventricular and interventricular delays, both at rest and during exercise. IEGM, intracardiac electrogram; ECHO, echocardiogram; LVOT, left ventricular outflow tract; VTI, velocity time integral; biv, biventricular pacing.

Figure 4

Plot of left ventricular outflow tract VTI after echocardiographic vs. IEGM optimization of atrioventricular and interventricular delay. The left part refers to rest and the right to exercise. IEGM, intracardiac electrogram; ECHO, echocardiogram; VTI, velocity time integral.