A Time-Related Study by Doppler and M-Mode Echocardiography of Hemodynamics, Heart Size, and AV Valvular Function During Activity-Sensing Rate-Responsive Ventricular Pacing

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Abstract
Noninvasive Doppler and M-mode echocardiography were used to: measure stroke volume (SV), left atrial (LA) size, left ventricular end-diastolic (EDD), end-systolic dimensions (ESD), left ventricular fractional shortening (FS), and for determination of mitral and tricuspid insufficiency (MI and TI) before starting and after 1, 3, and 6 months of rate-responsive ventricular pacing (RRP). The study group consisted of 13 patients (mean age, 75 years) who could be expected to benefit from an increase in cardiac output mediated by an increment of heart rate during exercise. In VVI + activity mode (RRP), the pacemaker was programmed to a basic heart rate of 60 and a maximum heart rate of 125 bpm. The SV at rest was 71 +/- 5 before RRP, and fell to 57 +/- 4 after 3 months (p less than 0.05) and to 53 +/- 4 ml/beat after 6 months of RRP (p less than .01). The LA size and ESD were unchanged during follow-up. The EDD decreased from 6.2 +/- 0.3 to 5.4 +/- 0.2 (p less than 0.002) during the first 6 months of RRP. The FS was reduced from 33 +/- 4 to 27 +/- 3% (p less than 0.02) during the first 6 months of RRP. Four of 6 patients treated previously with a VVI pacemaker (mean duration, 9 years) had MI + TI, and 3 of the 7 patients not paced previously had MI before RRP. In the last group, 1 new patient developed MI, 1 new patient developed MI + TI, and 2 patients who had MI also developed TI within 6 months of pacing. Thus, of 13 patients, 9 (69%) had either MI or MI + TI.