Preimplantation echo Doppler evaluation of VVI versus DDD pacing

This study was carried out to select before permanent pacemaker implantation patients with complete atrioventricular block (CHB) who would benefit best from DDD pacing, and to determine the optimal atrioventricular delay (AVD) for each of those patients. This was achieved with the aid of Doppler echocardiography. The effect of different AVDs on both the systolic and diastolic function of the normal and failing heart was also delineated in this study.

Thirty patients with CHB and normal sinoatrial function were selected, with no age or sex predilection. These patients were categorized into three equal groups: groups A, B, and C with normal left ventricular (LV) systolic and diastolic function, LV diastolic dysfunction, and LV systolic dysfunction, respectively. For each patient, systolic and diastolic function was calculated utilizing echo Doppler during CHB, temporary VDD pacing with different AVDs, and temporary VVI pacing with a rate matching that during VDD mode. Temporary VDD mode of pacing was performed utilizing a temporary bipolar ventricular lead for ventricular pacing and an esophageal lead for atrial sensing to trigger ventricular pacing.

Qualitatively the most obvious change in the pattern of LV filling as AVD is increased in the three groups, is the earlier occurrence of active atrial filling A wave due to progressive approximation of the ECG P wave toward the previous QRS. As the AV interval is increased, the following changes occur: (a) A wave occurs progressively earlier with superimposition onto the early filling E wave resulting in a progressive increase in its velocity (VA), its FVI, and its percent atrial contribution (%AC); (b) the three times diastolic filling time (DFT), mitral valve opening to Q wave (MVO-Q), and closure (Q-MVC) progressively shorten; (c) since DFT decreases, less passive filling occurs early during diastole, thus E.FVI decrease with longer AV intervals; (d) the ratios VE/VA and FVI E/A decrease subsequently to the previous described changes. Compared to CHB, percent ejection fraction (% EF) was not significantly changed during VVI pacing. Percent EF increased significantly during VDD in comparison to VVI pacing modes. Percent EF was highest at optimal AVD and decreased as this AVD increased or decreased. The cardiac output (CO) increment during VDD in comparison to VVI pacing modes differed much among the three groups. In group A, a 10.29% increase in CO was seen when comparing VDD pacing (with optimal AVD) with that of VII one; in group B, this increment was much greater and reached 29.48%; in group C it reached 23.68%.(ABSTRACT TRUNCATED AT 400 WORDS)