LEFT ATRIAL PRESSURE-CLAMP SERVOMECHANISM DEMONSTRATES LV-SUCTION IN CANINE HEARTS WITH NORMAL MITRAL-VALVES

A novel technique is presented to study suction of the in situ left ve ntricle in open-chest experimental animals without requiring cardiopul monary bypass or disturbing the native mitral valvular apparatus. In 1 7 dogs, left ventricular pressure (LW) and left atrial pressure (LAP) were measured, the left atrium was cannulated and connected to a servo pump, and LAP was controlled to a setpoint near 0 mmHg by withdrawing blood from the left atrium. Heart rate [103 +/- 17 (SD) min(-1)], pea k pressure (100 +/- 13 mmHg), minimum pressure (1.4 +/- 0.8 mmHg), and maximum rate of change of pressure with respect to time during isovol umic contraction and relaxation (2,506 +/- 775 and -1,761 +/- 855 mmHg /s, respectively) were normal. Servo control of LAP was possible to +/ - 1 mmHg. LV suction was demonstrated in each heart (mean negative LVP -2.3 +/- 1.1 mmHg; P < 0.0001). This new technique demonstrates that the left ventricle can generate negative diastolic suction pressures w hen examined in vivo and in situ with an undisturbed mitral valve and physiologically normal preload and afterload. This adds to a growing b ody of evidence that, under appropriate circumstances, the heart can s uck blood into itself and thereby aid in its own filling.