The impact of chronotropic incompetence on atrioventricular conduction
times in heart failure patients
Objectives: To evaluate changes in intrinsic atrioventricular
(AV) conduction associated with exercise and atrial pacing among heart
failure patients with cardiac resynchronization therapy (CRT).
Methods: RAVE was a multicenter prospective trial of CRT
patients. Heart rate was increased with incremental atrial pacing up to
130 beats/min and with submaximal exercise without atrial pacing.
According to maximal heart rate achieved during exercise, patients whose
maximal heart rate < 100 bpm or 75% of 85% of age predicted
max heart rate were diagnosed with chronotropic incompentence(CI).
Others were classified as patients with chronotropic compentence(CC).
For CI patients, an additional symptom limited exercise with rate
adaptive pacing activated was performed. Intracardiac intervals were
measured from the implantable lead electrograms. Results: There
were 12 subjects with CI and 24 with CC. With atrial pacing, AV interval
immediately increased and gradually increased with incremental atrial
pacing in all patients. However, the changes in the atrial to right
ventricular (ARV) and atrial to left ventricular (ALV) intervals with
increasing atrial pacing rates were about 3-fold greater in CI patients
compared to CC patients (28.3±29.5 vs. 10.8±8.9 ms/10 bpm for ARV and
25.5±22.1 vs. 9.9±8.8 ms/10 bpm for ALV in the supine position, p
< 0.05). In CI pacing with rate-adaptive pacing during
exercise, AV interval changes with paced heart rate were variable.
Conclusions: AV response to overdrive atrial pacing at rest may
provide a simple means of identifying chronotropic competence in CRT
patients. For patients with CI, who often require rate-adaptive atrial
pacing, rate-adaptive AV algorithms should be adjusted individually.