The atrioventricular delay of cardiac resynchronization can be optimized hemodynamically during exercise and predicted from resting measurements.
BACKGROUND
Atrioventricular (AV) optimization of cardiac resynchronization therapy (CRT) is typically calculated at rest. However, patients often become symptomatic during exercise.


OBJECTIVE
In this study, we use acute noninvasive hemodynamics to optimize the AV delay of CRT during exercise and investigate whether this exercise optimum can be predicted from a three-phase resting model.


METHODS
In 20 patients with CRT, we adjusted the sensed AV delay while the patient exercised on a treadmill up to a heart rate of 100 bpm to identify the hemodynamically optimal value. Separately, at rest, by pacing with three different configurations and calculating the sensed-paced difference, we calculated an "expected" value for the exercise optimum.


RESULTS
It was possible to perform AV delay optimization while a patient exercised. The resting three-phase model correlated well with the actual exercise optimal AV delay (r = 0.85, mean difference +/- standard deviation [SD] = 3.7 +/- 17 ms). Simply using measurements made at rest during atrial-sensed pacing showed a poorer correlation with exercise (r = 0.64, mean difference +/- SD = 2.2 +/- 24 ms). The three-phase resting model allows improved exercise hemodynamics to be achieved. Programming according to the three-phase resting model yields an exercise blood pressure of only 0.5 mmHg (+/-1.4 mmHg; P = NS) less than the true exercise optimum, whereas programming the resting sensed optimum yields an exercise blood pressure of 1.4 mmHg (+/-2.2 mmHg, P = .02) less than the true optimum.


CONCLUSIONS
Using acute noninvasive hemodynamics and a protocol of alternations, it is possible to optimize the AV delay of cardiac resynchronization devices even while a patient exercises. In clinical practice, the exercise optimum AV delay could be determined from three phases of resting measurements, without performing exercise.
Whinnett
Zachary I
ZI
International Centre for Circulatory Health, St. Mary's Hospital and Imperial College, London, United Kingdom. zacharywhinnett@yahoo.com
Briscoe
Cathy
C
Davies
Justin E R
JE
Willson
Keith
K
Manisty
Charlotte H
CH
Davies
D Wyn
DW
Peters
Nicholas S
NS
Kanagaratnam
Prapa
P
Hughes
Alun D
AD
Mayet
Jamil
J
Francis
Darrel P
DP
D001283:Atrioventricular Node / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D016009:Chi-Square Distribution; D017147:Defibrillators, Implantable; D015444:Exercise; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics; D006801:Humans; D011237:Predictive Value of Tests; D012146:Rest