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Ann Thorac Surg 2001;71:S56-S59
© 2001 The Society of Thoracic Surgeons
a Department of Surgery, East Tennessee State University, Johnson City, Tennessee, USA
b Department of Thoracic and Cardiovascular Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
c Department of Cardiothoracic Surgery, Hahnemann University Hospital, Philadelphia, Pennsylvania, USA
d Division of Cardiothoracic Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
e Division of Cardiothoracic Surgery, University of Missouri, Columbia, Missouri, USA
f Section of Cardiac Surgery, University of Michigan, Ann Arbor, Michigan, USA
Address reprint requests to Dr Pennington, Department of Surgery, East Tennessee State University, PO Box 70575, Johnson City, TN 37614
e-mail: penningg{at}etsu.edu
Presented at the Fifth International Conference on Circulatory Support Devices for Severe Cardiac Failure, New York, NY, Sept 15–17, 2000.
Abstract
Circulatory support devices are frequently required in postcardiotomy shock, postmyocardial infarction shock, and acute myocarditis. A panel of cardiac surgeons addressed the use of these devices in 4 patients. Cardiogenic shock after mitral valve replacement was considered best served by a left ventricular assist device (VAD) with apical rather than atrial cannulation. A left VAD should be placed first and a right VAD only if needed. Acute myocardial infarction shock was considered best treated with a left VAD with left ventricular cannulation to avoid thrombosis. If cardiac transplantation is an option, a long-term device must be considered. Young patients with acute fulminant myocarditis should be implanted with VADs in anticipation of recovery, and transplantation should be delayed. Patients with severe heart failure after coronary bypass grafting were considered best served by an extracorporal membrane oxygenation (ECMO) system or a VAD. Current postcardiotomy survival rates of postcardiotomy patients of 20% to 40% are worthwhile, but can be improved. Temporary devices such as ECMO can be changed to more long-term devices when necessary.
The earliest cases of mechanical circulatory support were applied for acute heart failure, particularly postcardiotomy shock [1, 2]. During the last decade, applications of devices for longer-term use, such as the bridge to transplantation [3], and even destination therapy [4], have experienced a large degree of success. However, acute heart failure continues to represent a challenge for the application of mechanical circulatory support devices. The applications generally occur in three broad categories: (1) postcardiotomy shock, in which patients having undergone a cardiac operation either cannot be weaned from cardiopulmonary bypass or develop low cardiac output in the postoperative period; (2) acute cardiogenic shock resulting from myocardial infarction, and (3) various forms of cardiogenic shock or low cardiac output state caused by acute myocarditis.
The application of circulatory devices for postcardiotomy shock has been available for many years and has provided a justifiable but somewhat disappointingly low salvage of patients. The various factors determining the success of such applications in the postcardiotomy period include appropriate timing, selection of the appropriate type of support (ie, right ventricular support as well as left ventricular support when required), the use of devices that are simple to insert, control of bleeding, and concomitant medical therapy, such as the proper use of inotropic and vasodilatory drugs, including nitric oxide for pulmonary vasoconstriction. Several different devices are currently being used for postcardiotomy shock including extracorporal membrane oxygenation (ECMO) [5], the ABIOMED (Danvers, MA) ventricular assist device (VAD) [6], the Thoratec (VAD) (Thoratec Laboratories Corporation, Pleasanton, CA) [7], and several centrifugal pumps [8]. Circulatory support in postcardiotomy patients has yielded a hospital survival rate of 20% to 40%, a percentage that has not increased substantially over the last decade, and does not differ with the use of different devices. It is widely held principle that the severity of the patient’s condition is a much more important determinant of outcome than the type of device used.
Patients and methods
Acute myocardial infarction shock has been recognized for many years but until recently has not been one of the common entities for which mechanical circulatory support has been applied. In recent years there is increasing experience with this type of application [9]. Patients are being placed on circulatory support early in the course of cardiogenic shock in hopes of salvaging vital organs and providing a form of triage in which vital organ function, particularly neurological and renal, can be accurately assessed. Some of these patients may subsequently be candidates for cardiac operation, the application of more sophisticated devices, or even cardiac transplantation, but the initial salvage is necessary in order to make those options available.
Finally, in most large series of circulatory support there are a number of patients implanted for acute onset of cardiac failure, either proven or presumed due to some form of myocarditis. The extent of the myocarditis and the degree to which it may produce severe heart failure and cardiogenic shock is not easily predicted, but it represents a small fraction of all patients who develop myocarditis. In the last several years, sporadic cases of myocardial recovery have occurred, particularly in young patients who have had shock for shorter periods of time and benefit from several days or weeks of support [10]. The general philosophy has arisen that such patients may be better served by maintaining circulatory support than pursuing transplantation, since many of them have a reasonable chance for recovery and the long-term outcome of younger patients requiring cardiac transplantation is not encouraging.
Considering these three major categories, the cardiothoracic surgeon, cardiologist, and other members of the heart failure team are faced with several decisions regarding how, when, and with which device to apply circulatory support for acute heart failure. To provide some guidelines, typical patients were reviewed that illustrate the principles and necessary decision-making that go into the treatment of such patients. These patients were presented to a panel of cardiac surgeons, including the authors, as well as a large audience of heart failure surgeons and physicians attending The Society of Thoracic Surgeons-sponsored Circulatory Support 2000 meeting in New York in September. The synopses of recommendations for these patients were prepared by the principal author as a summary of the recommendations that came out of the discussion.
Patient 1
The first patient is a 55-year-old woman with rheumatic mitral valve disease, a previous mitral commissurotomy, and chronic atrial fibrillation who has undergone mitral valve replacement with a St. Jude bileaflet prosthesis. She develops severe biventricular failure and cannot be weaned from cardiopulmonary bypass in spite of vasodilators, inotropic drugs, nitric oxide, and intraaortic balloon pump. What is your recommendation?
This patient was thought to be a somewhat unusual circumstance of severe cardiac failure following mitral valve replacement, but it was obvious that several members of the panel as well as the audience had been involved in similar situations. The salient features of the case are a patient with severe biventricular failure who has had a mechanical valve implanted in the mitral position. Discussion centered first on the etiology of the failure and the need to assure that it was not related to mechanical device malfunction, such as a stuck leaflet or other malfunction of the valve. This could be determined by transesophageal echocardiography and if malfunction of the valve was observed, the valve would be explored for correction or replacement. Assuming that there was no valve problem, the recommendation was that she undergo placement of a left ventricular assist device using left ventricular cannulation. This was particularly stressed by the panel because of the previously reported cases of thrombosis of mechanical mitral valves in patients who were supported with left atrial cannulation. If the left ventricle is cannulated, one can promote high velocity flow across the mitral valve, thereby washing the valve and preventing stasis that leads to thrombosis. The general opinion was that a left ventricular assist device be placed first and attempts made to wean her from cardiopulmonary bypass and then determine the extent of right ventricular dysfunction. If the left ventricular device was in place and filling well with a central venous pressure below 20 millimeters of mercury, it is presumed that right ventricular support may not be required. However, if there is evidence of poor filling of the left ventricle, elevated central venous pressure above 20 millimeters of mercury and gross evidence of right ventricular dysfunction, biventricular support should be applied. Of course, the use of nitric oxide for pulmonary hypertension or right ventricular failure should be applied before inserting the right device.
In general, the use of an ABIOMED or a Thoratec left ventricular assist device was thought desirable, but if neither was available, then a centrifugal pump was considered acceptable. Application of centrifugal pumps to the left ventricle are more challenging because there are no commercially available cannulae. Although the need for cardiac transplantation seemed unlikely, if cardiac transplantation was considered a future option, a Thoratec device has an advantage over other systems since it can provide several months of support needed to come to the conclusion.
Patient 2
The second patient is a 50-year-old man brought to the cardiac catheterization laboratory 6 hours after suffering a large anterior myocardial infarction caused by occlusion of his left anterior descending coronary artery. The left anterior descending coronary artery was opened and stented in the catherization laboratory, but he was hypotensive with low cardiac output and mild metabolic acidosis in spite of large doses of inotropic and vasodilating drugs, as well as intraaortic balloon pump support. The cardiac surgeon was called to consider VAD placement.
This patient was viewed as not being an infrequent circumstance and the discussion centered around whether he should be supported with a ventricular assist device or an ECMO system. His left ventricle was markedly compromised by the acute infarction, but there may have been some degree of stunning and the potential existed for significant recovery of left ventricular function. If circulatory support could be maintained for a period of several days or weeks, the degree of ventricular recovery would become more clear and a definitive plan could then be determined. In general, left ventricular cannulation was thought to be an advantage in this particular patient because it prevents stasis in the left ventricle, which is a risk for thrombosis and subsequent systemic embolization. Some panel members suggested ECMO, but others believed that ECMO is a poor method of supporting such a patient because it does not decompress the left ventricle and may produce increased left ventricular wall stress or promote thrombus formation in spite of anticoagulation. The question arose as to the risk of cannulating a freshly infarcted left ventricle, but the general experience is that this is rarely a problem since left ventricular cannulation markedly reduces left ventricular pressure so that ventricular tearing or significant bleeding from that site are very unlikely. There was also the admonition that the patient’s other coronary arteries should be carefully studied to determine whether coronary bypass grafting of the other vessels would be of value. If there are no other major vessels involved, there is no rationale to perform bypass grafting to the left anterior descending artery. The possibility of cardiac transplantation is also an option in the young patient if he should not recover enough function to allow for left ventricular assist device removal. The strategy of cardiac transplantation would either require change to a more sophisticated device such as a Novacor (World Heart Corporation, Ottawa, Ontario, Canada) or TCI Heartmate (ThermoCardio Systems, Woburn, MA) or the initial implantation of a Thoratec VAD, which could support him until cardiac transplantation was accomplished.
Patient 3
The third patient is that of a 20-year-old professional soccer player who developed a chronic cardiorespiratory illness and was ultimately listed for cardiac transplantation because of severe myocarditis. He suddenly deteriorated and required admission to the intensive care unit, but was hemodynamically stabilized with ventilator and drug support. His pulmonary vascular resistance was normal and he had normal renal function. After a week of attempted weaning from drugs or the ventilator, the cardiac surgeon was consulted to consider circulatory support.
This patient was considered a particularly good candidate for a short-term ventricular assist system, which could provide time for myocardial recovery. The treatment should focus on the potential for recovery rather than upon transplantation. It is presumed that this patient had a form of fulminant myocarditis, which paradoxically may allow a somewhat better chance for complete recovery. Either left ventricular or left atrial cannulation can be used and may be accomplished without cardiopulmonary bypass. The need for biventricular support can be determined at the time of device implantation. A Thoratec VAD is preferred since it allows time for recovery of the ventricle without the need for more complex devices, such as the Novacor or TCI Heartmate.
The question arose as to when this patient might be considered a candidate for cardiac transplantation since there is certainly a possibility that his heart would never recover. In general, if recovery has not occurred after 2 months of successful support with all vital organs functioning well, cardiac transplantation should be pursued with the assumption that the heart is not going to recover. There were no specific guidelines outlined for determining exactly whether cardiac recovery had occurred. Although some centers are using "loading of the ventricle" to stimulate recovery, those protocols have not been established or proven.
Patient 4
The fourth patient is a 75-year-old man with a previous myocardial infarction due to severe coronary artery disease, marginal renal function (blood urea nitrogen, 50; creatinine, 2.0) and a left ventricular ejection fraction of 40% who developed severe left ventricular failure after coronary artery bypass grafting. He was weaned from cardiopulmonary bypass with large doses of inotropic and vasodilatory drugs and an intraaortic balloon pump. His blood pressure was 100/60 mm of mercury, but his cardiac index was 1.4 L/min/m2 and his left atrial pressure was 20 mm of mercury. He had urine output of 50 cubic cm/hr and normal blood gases. What is your recommendation?
Such patients are occasionally encountered in all large practices of cardiac operations. They undergo coronary bypass grafting but respond poorly to the usual pharmacologic methods of providing support. At the end of a difficult case, and multiple attempts to provide satisfactory hemodynamics, the surgical and anesthesia teams may be tempted to increase the ionotropic drugs to exceedingly high levels to get the patient out of the operating room and into the intensive care unit.
This patient’s poor cardiac output and marginal renal function could prolong the period of deterioration and precipitate his demise because of his multiple organ failure. Therefore, it was recommended that he receive support either with an ECMO system or a VAD. At least two members of the panel thought ECMO would be a suitable support system since it could be applied quickly in the operating room, is relatively inexpensive, and would provide a period of time to determine the potential for recovery. Others believed that a ventricular assist device would be more desirable because it could be applied either to the left atrium or the left ventricle and the choices would include an ABIOMED VAD, Thoratec VAD, or a centrifugal pump. It was thought that left heart support would probably be successful and that biventricular support would not be necessary, but should be readily available.
The question arose as to whether the patient was too old to be considered for postcardiotomy support. The panel believed that if the patient’s operation was undertaken in the first place, all efforts should be made to save him. There was a question whether such patients may be denied support on the basis of financial restrictions, but none of the panelists thought this particular patient would fall into that category. However, in later discussion it was pointed out by some of the European cardiac surgeons that there are certainly patients who would not be supported at their institutions because of economic restrictions and the undue pressure placed on the resources of the institution.
Results
These presentations and subsequent discussion may help to define the current practice of using mechanical circulatory support for acute heart failure. It is apparent that, in spite of the relatively low yield from such applications, there continues to be a steady use of these systems in postcardiotomy patients and an increased use in patients with shock caused by myocardial infarction and myocarditis. The actual devices used vary depending upon the institution and the devices available. It is interesting that this discussion suggests that a significant number of postcardiotomy patients are being supported with ECMO instead of ventricular assist devices. This is somewhat surprising because ECMO requires constant surveillance by either perfusionists or ECMO technicians rather than the nurses in the intensive care unit. Yet the advantages of ECMO are that it can be inserted rapidly, it is relatively inexpensive, and it often provides support long enough to determine whether postcardiotomy function may improve. However, we would like to believe that ventricular assist devices cannot only provide better efficiency and effectiveness, but also be made easy to implant. It does appear that of all the ventricular assist devices currently being used in patients with acute cardiogenic shock, the ABIOMED is the most common. The Thoratec, which is also approved for postcardiotomy use, is increasing in use; it provides the potential for bridging to transplantation over several months or even years if necessary. Centrifugal pumps continue to be used exclusively in some centers, but it seems that their use in this population has diminished.
Comment
This symposium clearly focused on the need for improvements in acute circulatory support devices and particularly simpler, more easily implanted and less expensive devices that could provide the support needed to determine whether recovery may occur. The panelists and the audience must accept this as our challenge for the next decade.
Footnotes
Dr Pennington has an association with Thoratec Laboratories, Inc, for which he is a consultant.
References
This article has been cited by other articles:
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  B. G. Leshnower, T. G. Gleason, M. L. O'Hara, A. Pochettino, Y. J. Woo, R. J. Morris, T. J. Gardner, and M. A. Acker Safety and Efficacy of Left Ventricular Assist Device Support in Postmyocardial Infarction Cardiogenic Shock Ann. Thorac. Surg., April 1, 2006; 81(4): 1365 - 1371. [Abstract] [Full Text] [PDF]
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 N. C. Dang, V. K. Topkara, B. T. Kim, M. L. Mercando, J. Kay, and Y. Naka Clinical outcomes in patients with chronic congestive heart failure who undergo left ventricular assist device implantation J. Thorac. Cardiovasc. Surg., November 1, 2005; 130(5): 1302 - 1309. [Abstract] [Full Text] [PDF]
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 Y. Asaumi, S. Yasuda, I. Morii, H. Kakuchi, Y. Otsuka, A. Kawamura, Y. Sasako, T. Nakatani, H. Nonogi, and S. Miyazaki Favourable clinical outcome in patients with cardiogenic shock due to fulminant myocarditis supported by percutaneous extracorporeal membrane oxygenation Eur. Heart J., October 2, 2005; 26(20): 2185 - 2192. [Abstract] [Full Text] [PDF]
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 P. Naughton and C. A. Bashour Mechanical Support After Cardiac Surgery Seminars in Cardiothoracic and Vascular Anesthesia, September 1, 2002; 6(3): 237 - 257. [Abstract] [PDF]
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