Clinical Benefit of Rigourous AV Delay Optimization in Patients With a Dual Chamber Pacemaker

Ergospirometry protocol:

Symptom-limited exercise testing was performed on an electronically braked cycle ergometer (eBike 1.8, GE (General Electric) Healthcare) in a non-fasting condition and under medication. All exercise tests took place at a standardized time for each patient. After 1minute (min) of rest followed by 1min of unloaded cycling, the initial load was set at 20W (Watt) for 1 min, and was increased by 10 or 20W every 2 min until exhaustion. Cycle load increments were based on previous exercise testing, aiming to yield a test duration of approximately 10min. All tests were continued to volitional fatigue and no patients were limited by angina. The recovery period lasted at least 2 minutes. A 12-lead electrocardiogram was monitored continuously (Cardiosoft 6.6); maximum heart rate was registered.

The oxygen uptake efficiency slope (OUES) was calculated using [VO2= m(log10VE)+b, where m= OUES]. VO2=oxygen consumption

cf. Ergospirometry protocol

Quality of life, measured by a standardized Heart Qol questionnaire

IACD is defined as the time interval from the onset of the P wave on the ECG to the onset of A'm(c)(with A'm(c) representing the annular late diastolic peak velocities lateral mitral annular level). IACD measured this way in the study is called IACD³.

Hypothesis: interatrial conduction time will be higher in an elderly population

All standard 12-lead ECGs were obtained using the same recorder (Schiller, CARDIOVIT AT-10 plus) set at a 50 mm/s paper speed and 2 mV (millivolt)/cm standardization. To decrease the error, we measured P-wave duration manually with calipers. The mean P-wave duration (PWD) of 3 complexes was calculated in lead II. A PWD of > 120 ms, with or without a biphid P wave morphology was considered to be pathological and used for correlation study with IACD.

Components of left atrial function, as mentioned in secondary outcomes measures, namely left mitral annular late diastolic peak velocity (A'm(c)), left atrial late diastolic peak strain (εm), left atrial late diastolic peak strain rate (SRm).

Hypothesis: the larger the IACD, the poorer the left atrial function.

Hypothesis: change in VTI of the A wave on mitral inflow on echocardiography is a predictor of clinical response after AV optimization.

Hypothesis:change in mitral annular late diastolic peak velocity (A'm(c)) after AV optimization on echocardiography is a predictor of clinical response after AV optimization.

Intra-atrial asynchrony was defined as the differences between EMD(electromechanical delay)s'(c) and EMDt'(c) (RA asynchrony) and between EMDm'(c) and EMDs'(c) (LA asynchrony). EMDm'(c) is defined as the time interval from the onset of the P wave on the ECG to the onset of A'm(c). EMDt'(c) is defined as the time interval from the onset of the P wave on the ECG to the onset of A't(c). EMDs'(c) is defined as the time interval from the onset of the P wave on the ECG to the onset of A's(c). A't(c), A's(c) and A'm(c) are defined as the annular late diastolic peak velocities at lateral tricuspid, interatrial and lateral mitral annular level.

Hypothesis: the larger the IACD, the larger the P sense offset (time from P-onset to P-detection).

All measurements were done in sinus rhythm and during atrial pacing. IACD (and left atrial function) was also measured for each patient at an atrial pacing frequency of 75 ppm (at the time of AVD optimization).

All measurements were done in sinus rhythm and during atrial pacing. IACD (and left atrial function) was also measured for each patient at an atrial pacing frequency of 75 ppm (at the time of AVD optimization).

Hypothesis: AV block indication might have smaller IACD compared to bradycardia tachycardia syndrome indication, since in the latter one might consider more elaborate atrial pathology.

Hypothesis: the larger the IACD, the more the AV delay should be lengthened to optimize mitral inflow.

IACD¹ is defined as the time interval from the onset of the P wave on the ECG to the onset of the mitral peak late (A) velocity.

IACD² is defined as the time interval from the onset of the P wave on the ECG to the onset of A'm (with A'm representing late diastolic myocardial velocity at the lateral mitral annulus level).

IACD³ is defined as the time interval from the onset of the P wave on the ECG to the onset of A'm(c)(with A'm(c) representing the annular late diastolic peak velocities lateral mitral annular level).