"Very little has been published regarding the ability of continuous flow pumps to have similar effects on the right ventricle", stated study lead author Jeffrey A. Morgan, M.D., director of Cardiac Surgery Research at Henry Ford Hospital. "So we set out to evaluate its short-term and mid-term effects on central venous pressure and pulmonary artery pressures, on the severity of tricuspid regurgitation, as well as on the functioning of the right ventricle."
The study has been presented at the American Society for Artificial Internal Organs in Baltimore.
The pump, a left ventricular assist device (LVAD) known as the HeartMate II, was developed by Thoratec Corporation. LVADs are used to treat patients who are not candidates for heart transplant, and offer the advantage of being replaceable.
When implanted just below the heart and connected to a patient's diseased left ventricle - the heart chamber that pumps blood into the body through the aorta - it provides a constant, rather than a pulsing, flow. The only moving part in the HeartMate II is a tiny turbine with synthetic ruby bearings, lubricated by the blood itself. It's powered by a battery pack worn outside the body and connected by wires through the chest wall.
An earlier version of the device, which was larger and more complicated, was designed to mimic the heart's natural pulsing, but its size and the intricacies of its mechanism called for a simpler, smaller device that could also be used in more and physically smaller heart patients. Those implanted with the newer device have virtually no pulse because of the continuous blood flow.
Earlier studies showed that the pulsing, left-side version improved pressure in the pulmonary artery, which carries blood to the lungs from the right ventricle; improved function in the right ventricle; and reduced the severity of tricuspid regurgitation, a disorder that causes blood to leak back into the heart's atrium - the upper chamber on the right side - through the valve that's supposed to prevent such backward flow.
For the Henry Ford study, researchers monitored 41 patients, who were implanted with the HeartMate II to treat chronic heart failure, from March 2006 to July 2009. The mean age of the study group was just over 52 years.
At the end of the study, they found significant improvements in all of six measures included in the research, similar to published data for the earlier version of the HeartMate.
A companion study from Henry Ford also found that the HeartMate II, which is implanted in a much less invasive surgical procedure than its predecessor, also carried a far smaller risk of infections related to the device.
"Left ventricular assist devices have become the standard of care for patients with end-stage heart failure", stated lead author Jeffrey A. Morgan, M.D., Associate Director of Circulatory Assist Device Programme and Cardiac Transplantation, at Henry Ford. "However, development of a device-related infection can be a source of significant morbidity and mortality. The HeartMate II was designed to address specific limitations of the HeartMate I, including minimizing the invasiveness of LVAD implantation. The focus of this study was to ascertain whether the HeartMate II was associated with a decreased incidence of device-related infections."
This study has also been presented at the American Society for Artificial Internal Organs in Baltimore.
The study, which ran from March 2006 through June 2009, included 58 patients with chronic heart failure who were implanted with either the HeartMate II - which the United States Food and Drug Administration approved in January for use in patients with severe heart failure who are not candidates for a heart transplant - or its predecessor, the larger and more complicated HeartMate I XVE.
Of the study group, 41 patients were implanted with the HeartMate II and 17 with the older model. Those who developed infections were treated with antibiotics, and the effects of those infections on their short- and long-term survival were also studied.
Two patients, or 4,9 percent of those who had HeartMate II pumps, developed infections, compared to four patients, or 23,5 percent of those whose hearts were assisted by the previous model. The researchers also found no significant difference in survival between HeartMate II patients with and without infection at 30 days and one year.
Both devices were developed by Thoratec Corporation. Funding for both studies was provided by the Division of Cardiothoracic Surgery at Henry Ford Hospital.