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[Evaluation of the atrial contribution to ventricular filling in patients with DDD pacemakers]
Abstract:
To evaluate the usefulness of physiologic cardiac pacing, the trasmitral flow velocity was recorded using the pulsed Doppler method combined with 2-D echocardiography in 14 patients in whom a DDD pacemaker was implanted. DDD pacemakers were programmed to atrioventricular (AV) sequential pacing with AV intervals of 50, 100, 150, 200 and 250 msec, and VVI pacing modes at a heart rate of 70 bpm. The time-velocity integral (TVI) of the left ventricular (LV) inflow curve was obtained by digitizing the outline of the tracings and expressed in the percentage of that of AV sequential pacing with AV interval of 150 msec (the percent LV filling volume). The percent LV filling volume was 75% for 50 msec, 89% for 100 msec, 96% for 200 msec and 90% for 250 msec of an AV interval in AV sequential pacing. It was significantly smaller at AV intervals of 50, 100 and 250 msec than at an AV interval of 150 msec. It was significantly smaller (68%) in VVI pacing than at AV intervals of 100, 150, 200 and 250 msec in AV sequential pacing. The left atrial (LA) contribution to LV filling was assessed in terms of the fraction of TVI during LA contraction to that during total LV filling at the optimal AV interval (A/Fmax). The optimal AV interval was defined as the interval at which the maximum LV filling volume was achieved in individual patients. The A/Fmax showed a positive correlation with the percent increase of LV inflow volume, with conversion from VVI to AV sequential pacing with the optimal AV interval. It also showed a positive correlation with age. These results suggested that the LV inflow volume was greater in AV sequential pacing with the optimal AV interval than in VVI pacing, especially in patients with a large A/Fmax. In conclusion, pulsed Doppler echocardiography could be a useful, non-invasive technique to determine the indications for implanting a DDD pacemaker and the optimal AV interval in patients in whom DDD pacemakers are implanted.