Ann Thorac Surg 2004;77:149-150
© 2004 The Society of Thoracic Surgeons
Original article: cardiovascular
Invited commentary
Kevin Lachapelle, MD
Department of Cardiac Surgery, McGill University Health Center, 687 Pine Ave W, Suite S8.30, Montreal, Quebec, Canada H3A 1A1
e-mail: kevin.lachapelle{at}muhc.mcgill.ca
Pulsatile ventricular assist is a recognized treatment for life threatening heart failure [1]. This type of therapy is a laborious undertaking and the complication rate following device implantation remains high, with an overall survival rate of 65% to transplant. Significant ongoing problems include bleeding, infection, right heart failure, and mechanical failure of the assist device [1, 2].
Nonpulsatile continuous flow devices have been developed and, very recently, implanted in the hope of reducing procedural complications due to their small size, ease of implantation, and easier maintenance [3, 4]. Some of the potential drawbacks with these newer assist devices are the negative effects of not completely unloading the failing ventricle and the consequences nonpulsatile flow over the long term. In their paper, Klotz and colleagues attempt to address these concerns.
In this small, yet well-studied series of patients, right heart catheterizations as well as echocardiograms were performed before and at an average of 3.4 months after left ventricular device implantation in a relatively similar group of patients with either a pulsatile (21 patients) or nonpulsatile device (10 patients). They found that both devices were equally effective in reducing LV pressure as measured by mean pulmonary pressure and wedge pressure. As anticipated, left ventricular volume unloading was superior in the pulsatile group and, as such, the mean arterial pressure was also higher. Interestingly, the degree of LV volume unloading in the nonpulsatile group was dependent on the length of time the device had been implanted. Device contribution to overall cardiac output was higher soon after implant and then diminished over time in a near linear fashion. Five of the ten patients with the nonpulsatile device had resumption of antegrade flow across the aortic valve and two had a return of pulsatile flow measured noninvasively. Taken together, this is consistent with an improving and remodeling ventricle overtime in the nonpulsatile group. Clinically, both groups of patients were able to exercise to at least 50 W. The overall outcome to transplant was similar in both groups, but the numbers are too small to make meaningful judgments.
What this information does mean is that it is not physiologically necessary to have complete volume unloading to support the failing ventricle and the underperfused patient. Rehabilitation of both the patient and the ventricle appears possible with a nonpulsatile device, and a sign of ventricular improvement is the restoration of pulsatile flow. Whether one could further the ventricular recovery using this device to the point of explant is an intriguing concept.
That being said, we need more data regarding the overall outcome and complication rate of these newer nonpulsatile devices. In those patients with profound shock where complete unloading and circulatory support is crucial, this device may not work or may require significant inotropic supplementation. Patient selection may again play a significant role in outcome.
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References
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- Rose E.C., Gelijns A.C., Moskowitz A.J., et al. Long-term use of a left ventricular assist device for end-stage heart failure. N Engl J Med 2001;345:1435-1443.[Abstract/Free Full Text]
- Miller L.W. Patient selection for the use of ventricular assist devices as a bridge to transplantation. Ann Thorac Surg 2003;75:S66-71.[Abstract/Free Full Text]
- Grinda J.M., Latremouille C.H., Chevalier P., et al. Bridge to transplantation with the Debakey VAD axial pump: a single center report. Eur J Cardiothorac Surg 2002;22:965-970.[Abstract/Free Full Text]
- Vitali E., Lanfranconi M., Ribera E., et al. Successful experience in bridging patients to heart transplantation with the Micro- Med Debakey ventricular assist device. Ann Thorac Surg 2003;75:1200-1204.[Abstract/Free Full Text]
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