Doppler echocardiography determination of systolic and diastolic function in sequential and ventricular stimulation

In 16 patients with sequential pacing and partly impaired left-ventricular function (mean shortening fraction 23 +/- 7%), the flow through the mitral and aortic valves were studied with Doppler echocardiography at different AV-intervals, keeping heart rate constant at 70/min. The time-velocity integral of the early and late diastolic filling, the first one-third filling fraction, and the diastolic-filling time were found to be significantly dependent on the length of the AV interval (p less than 0.001). In the left ventricular outflow tract, the maximum stroke volume of 85.6 +/- 28.4 ml was measured at an AV interval of 200 ms. The stroke volume under VOO stimulation (70.5 +/- 24.1 cm) was 17% less (p less than 0.003). There was no correlation between the increase in stroke volume during sequential pacing and M mode or Doppler echocardiographic parameters. Thus, the haemodynamic benefit of sequential pacing cannot be predicted by echocardiography. Doppler echocardiography is useful for determining the AV interval leading to the maximal cardiac output at rest. In the Doppler echocardiographic assessment of left-ventricular function, the influence of the AV interval on diastolic-filling parameters must be considered.