Atrial Pacing Lead Location Alters the Effects of Atrioventricular Delay on Atrial and Ventricular Hemodynamics

Abstract

The combined role of atrial pacing lead location and AV timing on cardiovascular performance has not been defined. This study tested the hypothesis that atrial pacing lead location can change the dependence of LA and LV hemodynamics on AV timing in vivo. Dogs anesthetized with isoflurane (n = 8) were instrumented for measurement of hemodynamics including LA pressure, LA volume, and pulmonary venous bloodflow. Data were recorded during normal sinus rhythm, and atrial overdrive pacing from the right atrial appendage (RAA), proximal coronary sinus (CS), and LA lateral wall (LAW). The AV node was then ablated and measurements repeated during synchronous ventricular pacing and during dual chamber pacing from each atrial lead location at various AV delays (20, 60, 120, 180, 240, and 350 ms). Hemodynamics during intrinsic sinus rhythm and overdrive atrial pacing from different sites were similar. In contrast, ventricular or dual chamber pacing caused significant (P < 0.05) changes in cardiac output with different AV timing during RAA (3.5 +/- 0.2 vs 2.9 +/- 0.2 L/min at 120 and 350 ms, respectively) and LAW pacing but not CS pacing. A significant interaction between atrial lead location and AV delay was observed for changes in stroke volume, pulmonary venous blood transport, LA volume, and LV preload. The results indicate that the atrial contribution to cardiac output depends on AV timing and atrial lead location in isoflurane-anesthetized dogs with AV nodal conduction block.

Influence of Atrial Function and Mechanical Synchrony on LV Hemodynamic Status in Heart Failure Patients on Resynchronization Therapy

“…Goyal and Spodick (18) found an inverse correlation between P-wave duration and LA ejection fraction. Furthermore, AP reduced LV stroke volume without significant differences in regional LV strain in an animal study (21). In our study, AP resulted in a reduction of LV filling and stroke volume as re- Tables 1 and 3.…”

Safety and Performance of a System Specifically Designed for Selective Site Pacing

“…However, many experimental studies and large clinical trials have shown that the abnormal conduction of ventricular paced depolarization may lead to impaired cardiac function, arrhythmias, increased morbidity, and even mortality 1–8 . Similarly the RAA pacing results in intraatrial dyssynchrony, as reflected by prolonged P‐wave duration, with potentially important implications for atrial arrhythmias and for atrial hemodynamic function 9,10 …”

Automatic Beat‐to‐Beat Left Heart AV Normalization:

“…Correction for this delay is currently available as the “differential AV” or P‐sense offset (PSO) in most DDD pacemakers, 6 with a default value of about 30 ms. Spontaneous interatrial delay, that is, the time between the onset of the right atrial (RA) and left atrial (LA) P waves, which is reflected in the P wave width of the surface ECG, is related to LA size 7 . Spodick 8 has shown that interatrial block is correlated with a large LA, Hettrick et al 9 have shown in dogs the value of both AV delay and atrial lead positioning on ventricular hemodynamics, and Daubert et al 10 has found that correction of interatrial block by atrial resynchronization can improve hemodynamics. Atrial pacing causes another delay, from the onset of the RA pacing pulse to the onset of the LA P wave, as measured from the coronary sinus or the esophageal electrodes 11–14 .…”