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J Thorac Cardiovasc Surg 2009;137:243-245
© 2009 The American Association for Thoracic Surgery
Brief Communication |
a University Hospital, Leuven, Belgium
b University of Maryland, College Park, Md
c University of Louisville, Louisville, Ky
d Newark Beth Israel Medical Center, Newark, NJ
e Columbia University, New York, NY
Received for publication December 30, 2007; accepted for publication February 2, 2008. * Address for reprints: Filip Rega, MD, University Hospitals Leuven, Cardiac Surgery, Herestraat 49, 3000 Leuven, Belgium.
The clinical benefits of implantable left ventricular assist devices (LVADs) as a bridge to transplant and for destination therapy have been demonstrated.1-3
The low rate of LVAD use is attributed to the invasive nature of the implantation surgery and the relatively high rate of complications.4 If LVADs were used in less critical hemodynamic and clinical states, the flow requirements could be reduced.
The Synergy Micro-Pump (CircuLite, Inc, Hackensack NJ) is approximately the size of a size AA battery, weighs only 25 g, and can pump as much as 2.5 to 3 L/min. Its small size permits insertion through a right-sided minithoracotomy. The pump is then placed subcutaneously in the pectoral region, similar to a pacemaker. This is the first clinical report describing the Synergy Micro-Pump's implantation procedure, hemodynamic effects, and clinical results.
The patient was a 46-year-old man (weight 85 kg, height 184 cm, body surface area 2.01 m2) without significant illness in his medical history who had a large anterior myocardial infarction in March 2007. New York Heart Association functional class IV symptoms developed within 2 months (cardiac index 2.2 L/[min/m2], pulmonary arterial pressure 55/24 mm Hg, pulmonary capillary wedge pressure 31 mm Hg, maximum oxygen consumption 8.5 mL kg/min). The patient was listed for a heart transplant. His condition continued to deteriorate during the ensuing 6 weeks, however, and he was accepted for investigational study of the Synergy Micro-Pump. This study was conducted in accordance with the Declaration of Helsinki according to a study protocol approved by the Leuven University Ethics Committee and the Belgian Competent Authority. The study protocol was approved by the University Hospitals Leuven Ethical Committee on April 10, 2007.
After informed consent was obtained (June 28, 2007), the patient underwent elective surgery. Hemodynamics after anesthesia included an arterial pressure of 96/69 mm Hg, a cardiac output of 2.5 L/min, a pulmonary arterial pressure of 55/24 mm Hg, and a pulmonary capillary wedge pressure of 31 mm Hg. A 4-cm subclavicular incision was made to isolate the right subclavian artery. A small subcutaneous pocket, similar to a pacemaker pocket, was formed for the pump anterior to the right pectoralis major muscle. An incision was then made in the right fourth intercostal space to gain access to the left atrium through the Waterson groove. The nitinol-reinforced silicone inflow cannula was inserted into the left atrium between the insertions of the right upper and lower pulmonary veins. The inflow cannula was tunneled through the second intercostal space to exit the thorax in the area of the subcutaneous pocket. The 8-mm expanded polytetrafluoroethylene outflow graft was anastomosed to the subclavian artery. The electrical wire of the pump was then tunneled to exit the body over the right lower quadrant of the abdomen. Pump speed was set at 22,000 rpm (pump flow approximately 2.5 L/min), the surgical wounds were closed, and the patient was taken to the intensive care unit. The duration of the surgery was approximately 2 hours. Pump position is illustrated in
Figure 1.
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Table 1 summarizes the evolution of clinical parameters during the first 100 days after the procedure.
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We summarize here the first use of the Synergy Micro-Pump in a patient as a bridge to transplant. This device provides partial left ventricular support (2-3 L/min) and is specifically designed to be implanted in patients who are not as critically ill as the patients now typically receiving full support LVADs. Because of the small size of the device, the surgery was relatively short and significantly less traumatic than with other LVADs. The combination of the patient's intrinsic cardiac output of 3.6 L/min with the 2.5 L/min provided by the pump summed to a total cardiac output in excess of 6 L/min, a normal resting value. No significant hemolysis was noted, and there were no serious adverse effects.
There are several unique features of the device. This pump is the smallest implanted assist device ever used as a bridge to transplant. This is the first implanted device with the inflow cannula placed in the left atrium and the outflow cannula connected to the subclavian artery. Because of the unique anatomic position, the procedure was anticipated to be less invasive. As a result, flows of only 2.5 L/min were able to produce clinically significant and sufficient acute hemodynamic effects.
Footnotes
Synergy Micro-Pump (CircuLite, Inc, Hackensack, NJ) was provided by the manufacturer.
References
This article has been cited by other articles:
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  S. Demertzis, H. Tevaearai, T. Carrel, and S. Vandenberghe Aortic flow patterns resulting from right axillary artery cannulation Interact CardioVasc Thorac Surg, June 1, 2011; 12(6): 973 - 977. [Abstract] [Full Text] [PDF]
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 B. P. Meyns, A. Simon, S. Klotz, T. Wittwer, C. Schlensak, F. Rega, and D. Burkhoff Clinical benefits of partial circulatory support in New York Heart Association Class IIIB and Early Class IV patients Eur J Cardiothorac Surg, May 1, 2011; 39(5): 693 - 698. [Abstract] [Full Text] [PDF]
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 B. Meyns, S. Klotz, A. Simon, W. Droogne, F. Rega, B. Griffith, R. Dowling, M. J. Zucker, and D. Burkhoff Proof of Concept: Hemodynamic Response to Long-Term Partial Ventricular Support With the Synergy Pocket Micro-Pump J. Am. Coll. Cardiol., June 30, 2009; 54(1): 79 - 86. [Abstract] [Full Text] [PDF]
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