Ann Thorac Surg 2000;70:282-283
© 2000 The Society of Thoracic Surgeons
Case report
Invited commentary
G. Kimble Jett, MDa
a Department of Cardiovascular Surgery, Providence Seattle Medical Center, 1600 E Jefferson, #101, Seattle, WA 98122, USA
e-mail: kjett{at}providence.org
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Introduction
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The article by Westaby and colleagues describes the use of an implantable centrifugal blood pump for nonpulsatile left heart bypass for support of acute fulminant lymphocytic myocarditis. The patient had reversal of her shock and recovery of cardiac function, allowing removal of the device after 7 days of support. Although mechanical support has previously been used for support of myocarditis, this is a report of a successful outcome with the implantable AB-180 device. Several interesting points deserve attention.
Although acute fulminant myocarditis can be rapidly fatal [1], it has been shown that the heart can recover if the circulation is supported [2]. Survival rates of 70% have been demonstrated with pulsatile support [3]. Immunosuppression in the treatment of myocarditis, however, remains controversial [4]. Spontaneous improvement in biopsy-proven myocarditis has been shown in 48% of patients [5], so mechanical circulatory support is critical to allow myocardial recovery. The duration of support by Westaby and associates was short compared to other studies for duration of support has ranged from 8 to 14 days [2, 3]. Perhaps this short duration was due to their innovative weaning protocol, which deserves more evaluation. Nevertheless, one should allow adequate time for recovery of myocarditis prior to transplantation. Many cases of myocarditis can be supported merely with a left ventricular assist device, despite it being a biventricular process. Most myocarditis patients are young with normal pulmonary vascular resistance.
Reversal of shock is flow and pressure dependent [6]. Pulsatile flow can reverse shock more effectively than nonpulsatile [7]; however, when flows are 95 ml/kg/min there is no difference between pulsatile and nonpulsatile flow [8]. Westaby and colleagues were able to successfully reverse shock with their nonpulsatile device by maintaining flows of 5.5 L/min (approximately 100 ml/kg/min) and mean blood pressure of 70 mm Hg. With non-pulsatile pumps, flows need to be in excess of 90 ml/kg/min, and perfusion pressure needs to be normal. Pulsatile pumps are more likely to reverse shock and maintain normal organ function with reduced flows or pressures [6]. The ability of nonpulsatile pumps to reverse shock is important, because nonpulsatile pumps are small and more efficient than pulsatile pumps.
There are multiple uses for an inexpensive implantable support device. We are eager to see the further development of the AB-180 and similar devices.
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References
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Dec G.W., Jr, Palacios I.F., Fallon J.T., et al. Active myocarditis in the spectrum of acute dilated cardiomyopathies. N Engl J Med 1985;312:885-898.[Abstract]
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Marelli D., Laks H., Amsel D., Jett G.K., et al. Temporary mechanical support with the BVS 5000 assist device during treatment of acute myocarditis. J Card Surg 1997;12:55-59.[Medline]
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Personal Communication from ABIOMED, Inc. Data contained in PMA supplement to PMA P900023-BVS 5000-bi-ventricular support system.
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Mason J.W., O’Connell J.B., Herskowitz A., et al. A clinical trial of immunosuppressive therapy for myocarditis. N Engl J Med 1995;333:269-275.[Abstract/Free Full Text]
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O’Connell J.B. The role of myocarditis in end-stage dilated cardiomyopathy. Texas Heart Inst J 1987;14:268-275.[Medline]
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Jett G.K. Physiology of nonpulsatile circulation. ASAIO J 1999;45:119-122.[Medline]
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Orime Y., Shino M., Nakata K., et al. The role of pulsatility in end-organ microcirculation after cardiogenic shock. ASAIO J 1992;42:M724-M729.
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Satoh H., Miyamoto Y., Shimazaki Y., et al. Comparison between pulsatile and nonpulsatile circulatory assistance with recovery of shock liver. ASAIO J 1995;41:M596-M600.[Medline]
Related Article
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Mechanical bridge to recovery in fulminant myocarditis
- Stephen Westaby, Takahiro Katsumata, David Pigott, Xu Y. Jin, Kjell Saatvedt, Matthew Horton, and Richard E. Clark
Ann. Thorac. Surg. 2000 70: 278-282.
[Abstract]
[Full Text]
[PDF]
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Introduction
References