Effect of heart failure on the mechanism of exercise-induced augmentation of mitral valve flow.

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Abstract
The exercise response of left ventricular (LV) filling dynamics may be altered by congestive heart failure (CHF). Accordingly, we studied 18 conscious dogs, instrumented to measure micromanometer LV and left atrial (LA) pressures and determine LV volume from three dimensions. CHF was produced by 4-5 weeks of right ventricular rapid pacing. Before CHF, exercise (5.5-8.5 mph for 8-15 minutes) increased the maximum rate of LV filling (dV/dtmax) (197 +/- 37 versus 297 +/- 56 ml/sec [mean +/- SD], p < 0.05) in response to an increase in the maximum early diastolic LA to LV pressure gradient (5.8 +/- 2.0 versus 9.8 +/- 1.9 mm Hg, p < 0.05) produced by a fall in minimum LV pressure (1.0 +/- 2.9 versus -3.9 +/- 3.1 mm Hg, p < 0.01), whereas mean LA pressure was unchanged (6.4 +/- 3.1 versus 6.4 +/- 4.2 mm Hg, p = NS). The time constant of LV relaxation was shortened (28.1 +/- 3.2 versus 21.0 +/- 4.2 msec, p < 0.05). After CHF, dV/dtmax (141 +/- 51 versus 200 +/- 59 ml/sec, p < 0.05) and the maximum LA to LV press...

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