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P Lowe

Publications and source records attributed to P Lowe.

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The effect of graded exercise on cardiac output of the Jarvik-7-70 total artificial heart in humans.

Animal exercise studies have shown a self-regulated change in cardiac output (CO) with the J-7 total artificial heart (TAH). A 49-year-old, 75 kg patient received a J-7-70 TAH as a bridge to transplant. During bicycle exercise, the TAH heart rate, drive pressures, percent systole, and vacuum were unchanged. Cardiac output was measured by analysis of diastolic air exhaust. Mean arterial pressure (MAP) was measured via a radial artery catheter. Daily recordings of hemodynamics were made from TAH day 35 to 56 at rest, cycling with zero resistance, 18 watts resistance, return to zero resistance, and at rest. Values were as follows: baseline MAP, 75.7 +/- 9.7; LCO, 6.4 +/- 0.2; RCO, 6.8 +/- 0.2. For zero watts resistance MAP was 92.2 +/- 7.2*; LCO, 7.1 +/- 0.2*; RCO, 7.8 +/- 0.3*. For eighteen watts resistance MAP was 101.3 +/- 6.2*; LCO, 7.6 +/- 0.3*; RCO, 8.4 +/- 0.4*. For zero watts resistance MAP was 98.5 +/- 4.9*; LCO, 7.2 +/- 0.4*; RCO, 8.0 +/- 0.4*. The postexercise MAP was 86.4 +/- 4.1*; LCO, 6.2 +/- 0.2; RCO, 6.9 +/- 0.2. For all but baseline and postexercise MAPs, the average response was over a 4 minute interval. The starred values were significant compared to baseline p less than 0.05. Exercise resulted in an autoregulated change in TAH CO in man. Increasing the work of exercise produced an increased CO, reflecting changes in venous return. A TAH patient can exercise for more than 30 minutes with an autoregulated CO and no deleterious effects.

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