Atrial transport function and the corresponding transmitral flow and stroke volume depend on the timing of atrial contraction. To study the influence of short atrioventricular delay (AVD) on these hemodynamic parameters, transmitral flow velocity (by pulsed wave Doppler) and aortic flow (by electromagnetic technique) were studied and compared (paired t test) during normal and short AVD at fixed rate DDD pacing (80 bpm) in AV-blocked, open-chest canine preparations (n:16).
The short AVD resulted in a shorter acceleration (difference 4.1 ± 4.9 msec, mean ± SD, p<0.05), a lower peak velocity (difference: 7.1 ± 3.2 cm/sec, p < 0.001), a shorter (difference: 26.9 ± 16.2 msec, p<0.001) and more rapid deceleration (difference: 220.7 ± 291.7 cm/sec2, p < 0.005) of the late diastolic transmitral flow elicited by atrial systole. Stroke volume decreased (7.8 ± 5.2%, p < 0.001) during short AVD as a consequence of a reduced left ventricular filling due to the interruption of the active atrial transport by the onset of the ventricular contraction.
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