Anatomy and Physiology of Left Ventricular Suction Induced by Rotary Blood Pumps.
This study in five large greyhound dogs implanted with a VentrAssist left ventricular assist device focused on identification of the precise site and physiological changes induced by or underlying the complication of left ventricular suction. Pressure sensors were placed in left and right atria, proximal and distal left ventricle, and proximal aorta while dual perivascular and tubing ultrasonic flow meters measured blood flow in the aortic root and pump outlet cannula. When suction occurred, end-systolic pressure gradients between proximal and distal regions of the left ventricle on the order of 40-160 mm Hg indicated an occlusive process of variable intensity in the distal ventricle. A variable negative flow difference between end systole and end diastole (0.5-3.4 L/min) was observed. This was presumably mediated by variable apposition of the free and septal walls of the ventricle at the pump inlet cannula orifice which lasted approximately 100 ms. This apposition, by inducing an end-systolic flow deficit, terminated the suction process by relieving the imbalance between pump requirement and delivery from the right ventricle. Immediately preceding this event, however, unnaturally low end-systolic pressures occurred in the left atrium and proximal left ventricle which in four dogs lasted for 80-120 ms. In one dog, however, this collapse progressed to a new level and remained at approximately -5 mm Hg across four heart beats at which point suction was relieved by manual reduction in pump speed. Because these pressures were associated with a pulmonary capillary wedge pressure of -5 mm Hg as well, they indicate total collapse of the entire pulmonary venous system, left atrium, and left ventricle which persisted until pump flow requirement was relieved by reducing pump speed. We suggest that this collapse caused the whole vascular region from pulmonary capillaries to distal left ventricle to behave as a Starling resistance which further reduced right ventricular output thus contributing to a major reduction in pump flow. We contend that similar complications of manual speed control also occur in the human subject and remain a major unsolved problem in the clinical management of patients implanted with rotary blood pumps.
['Salamonsen|Robert Francis|RF|', 'Lim|Einly|E|', 'Moloney|John|J|', 'Lovell|Nigel Hamilton|NH|', 'Rosenfeldt|Franklin L|FL|']
D000818:Animals D004195:Disease Models, Animal D004285:Dogs D006353:Heart-Assist Devices D006439:Hemodynamics D008955:Models, Cardiovascular D011474:Prosthesis Design D011475:Prosthesis Failure D013318:Stroke Volume D013997:Time Factors D014160:Transducers, Pressure D014655:Vascular Resistance D018487:Ventricular Dysfunction, Left D016277:Ventricular Function, Left D017725:Ventricular Pressure
Left ventricular suction Rotary blood pump Left ventricular assist device Canine model Heart failure