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Ann Thorac Surg 1987;44:21-25
© 1987 The Society of Thoracic Surgeons

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Articles

A Valveless Counterpulsation Left Ventricular Assist Pump in the Descending Aorta: Hemodynamic Benefit with a Reduced Risk of Cerebral Emboli

From the Department of Cardiothoracic Surgery, the Carlyle Fraser Heart Center, Crawford W. Long Memorial Hospital of Emory University School of Medicine, Atlanta, GA

Because of valve malfunction and cerebral embolism reported with use of the total artificial heart, the descending aorta was reexamined as a site for a valveless counterpulsation left ventricular assist pump. The pump was introduced into the thoracic aorta at the level of the eighth thoracic vertebra in 11 canine right-heart bypass preparations. Heart rate (110 beats per minute), stroke volume (20 ml), and mean arterial pressure (80 or 100 mm Hg) were precisely controlled. The pump ejection volume was adjusted to equal 1 time or 2 times the stroke volume of the dog. A 20-ml ejection led to an 11% reduction in left atrial pressure, an 11% reduction in peak left ventricular pressure, and a 20% reduction in tension time index (all, p < .05 at a mean arterial pressure of 80 mm Hg). Systolic shortening (ultrasonic crystals) increased by 5% (p < .05 at a mean arterial pressure of 80 mm Hg). A 40-ml pump ejection led to an 11% reduction in mean left atrial pressure, a 17% reduction in peak left ventricular pressure, and a 21% reduction in tension time index (all, p < .05 at a mean arterial pressure of 80 mm Hg). The systolic shortening increased by 15% (p < .05).

To assess the relative risk of cerebral embolism, albumin spheres (40 to 60 µg) labeled with technetium-99 were injected into the pump chamber in 5 dogs (40-ml ejection, 2.1 ± 0.1 times the dog's stroke volume). Simultaneous sampling from the descending aorta and brachiocephalic artery revealed that 90 ± 4% of the total counts were from the descending aorta and 10 ± 4% were from the brachiocephalic artery. Exposure of the cerebral circulation to blood that had passed through the pump was approximately one-tenth that of the lower body. This valveless counterpulsation left ventricular assist pump, positioned in the descending aorta, significantly improved cardiac function with a greatly reduced risk of cerebral embolism.

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