Abstract
BackgroundControversy exists regarding how atrial activation mode and heart rate affect optimal atrioventricular (AV) delay in cardiac resynchronization therapy. We studied these questions using high‐reproducibility hemodynamic and echocardiographic measurements.MethodsTwenty patients were hemodynamically optimized using noninvasive beat‐to‐beat blood pressure at rest (62 ± 11 beats/min), during exercise (80 ± 6 beats/min), and at three atrially paced rates: 5, 25, and 45 beats/min above rest, denoted as Apaced,r+5, Apaced,r+25, and Apaced,r+45, respectively. Left atrial myocardial motion and transmitral flow were timed echocardiographically.ResultsDuring atrial sensing, raising heart rate shortened optimal AV delay by 25 ± 6 ms (P < 0.001). During atrial pacing, raising heart rate from Apaced,r+5 to Apaced,r+25 shortened it by 16 ± 6 ms; Apaced,r+45 shortened it 17 ± 6 ms further (P < 0.001).In comparison to atrial‐sensed activation, atrial pacing lengthened optimal AV delay by 76 ± 6 ms (P < 0.0001) at rest, and at ∼20 beats/min faster, by 85 ± 7 ms (P < 0.0001), 9 ± 4 ms more (P = 0.017). Mechanically, atrial pacing delayed left atrial contraction by 63 ± 5 ms at rest and by 73 ± 5 ms (i.e., by 10 ± 5 ms more, P < 0.05) at ∼20 beats/min faster.Raising atrial rate by exercise advanced left atrial contraction by 7 ± 2 ms (P = 0.001). Raising it by atrial pacing did not (P = 0.2).ConclusionsHemodynamic optimal AV delay shortens with elevation of heart rate. It lengthens on switching from atrial‐sensed to atrial‐paced at the same rate, and echocardiography shows this sensed‐paced difference in optima results from a sensed‐paced difference in atrial electromechanical delay.The reason for the widening of the sensed‐paced difference in AV optimum may be physiological stimuli (e.g., adrenergic drive) advancing left atrial contraction during exercise but not with fast atrial pacing.
Highlights
Optimization of atrioventricular (AV) delay has been shown to augment the acute hemodynamic benefits of cardiac resynchronization therapy (CRT) and has the potential to improve New York Heart Association (NYHA) functional classification and quality of life scores.[1]At present, routine optimization of the AV delay is not universally performed
The hemodynamically optimal programmed AV delay found during atrial pacing was significantly longer than that during atrial sensing, at the equivalent heart rate (Figure 5)
We found that the optimal AV delay shortens with increasing heart rate, regardless of whether the atrial rate is increased by exercise or by pacing
Summary
Optimization of atrioventricular (AV) delay has been shown to augment the acute hemodynamic benefits of cardiac resynchronization therapy (CRT) and has the potential to improve New York Heart Association (NYHA) functional classification and quality of life scores.[1]At present, routine optimization of the AV delay is not universally performed. In patients who have undergone physiological AV optimization with atrial sensing, the paced AV delay is commonly programmed longer by a fixed increment of 30 or 40 ms; this offset is applied across all heart rates. The principle behind this offset is to deliver the same time interval between mechanical motion of atrium and ventricle (Figure 1) regardless of whether the atrium is sensed or paced. Controversy exists regarding how atrial activation mode and heart rate affect optimal atrioventricular (AV) delay in cardiac resynchronization therapy. We studied these questions using high-reproducibility hemodynamic and echocardiographic measurements
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