A comparison of the acute and long-term hemodynamic effects of ventricular inhibited and atrial synchronous ventricular inhibited pacing.

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Abstract
Sixteen patients treated with a noninvasively progammable pacemaker were examined after a prolonged period of ventricular inhibited (VVI) and atrial synchronous ventricular inhibited (VDD) pacing. Maximal working capacity was determined by bicycle ergometry. Atrial and ventricular rates, brachial artery cuff pressure and breathing rate were determined at rest and during exercise. There was a mean increase in working capacity of 24% with VDD compared with VVI pacing (P < 0.001). Thirteen of the patients were catheterized. During VDD pacing, cardiac output was significantly higher, particularly during exercise (.+-. 32%) due to the capability of heart rate increase and despite a substantial compensatory stroke volume increase during VVI pacing. Arteriovenous O2 difference was much higher during VVI pacing, reaching 164 .+-. 14 ml/l during the highest work load, while the corresponding level during VDD pacing was 140 .+-. 14 ml/l (P < 0.001). During exercise, arterial blood lactate was significantly higher during VVI than during VDD pacing. Heart size was significantly smaller, 568 .+-. 98 vs. 530 .+-. 96 ml/m2 BSA (P < 0.05), during VDD pacing. A questionnaire was completed by the patients to evaluate subjective symptoms and pacemaker preference. This part of the study favored the VDD mode of pacing. VDD pacing is apparently superior to VVI pacing.