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Ann Thorac Surg 1997;64:1757-1762
© 1997 The Society of Thoracic Surgeons
Divisions of Cardiothoracic Surgery and Circulatory Physiology, Columbia-Presbyterian Medical Center, New York, New York
Accepted for publication July 3, 1997.
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Abstract |
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 TopFootnotes Abstract IntroductionPatients and MethodsResultsCommentReferences |
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Methods. Between April 1993 and February 1997, 12 patients underwent insertion of an implantable left ventricular assist device for postcardiotomy cardiogenic shock after coronary artery bypass grafting. Indications for insertion included postoperative cardiogenic shock (7 patients), postoperative cardiac arrest (3 patients), and failure to wean from cardiopulmonary bypass (2 patients).
Results. The median time to device insertion was 3.5 days. The mean duration of left ventricular assist device support was 103 ± 19 days (range, 2 to 225 days). Nine of 11 patients (82%) survived to undergo either transplantation (8 patients) or explantation (1 patient), with successful hospital discharge of all 9 patients. The major complication was device-related infection (42%). A single thromboembolism occurred in a patient with an infection.
Conclusions. Long-term outcome after postcardiotomy cardiogenic shock is improved substantially with the use of an implantable left ventricular assist device early in the postoperative course. Access to such a device is an important consideration before undertaking a high-risk cardiac operation, and early implantation of the device is a critical factor in ensuring long-term survival.
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Introduction |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Postcardiotomy cardiogenic shock (PCCS) occurs in approximately 2% to 6% of patients who undergo myocardial revascularization or valvular heart operations [1]. Early institution of intraaortic balloon counterpulsation (IABP) together with aggressive inotropic support allows successful weaning from cardiopulmonary bypass of 75% to 85% of patients, with a hospital survival rate of 50% to 55% [1–5]. In the remaining patients who are unresponsive to IABP and inotropic support, various forms of mechanical circulatory assistance have been used, with hospital discharge rates ranging from 25% to 50% [4, 6–14].
The relatively poor results of mechanical support in this setting are related to the late institution of support and a subsequently high incidence of complications. Renal failure, coagulopathy, bleeding, right heart failure, pulmonary hypertension, and the need for biventricular support all are more prevalent in this critically ill cohort of patients compared with other populations who receive mechanical circulatory support. Preexisting depressed myocardial function, recent or intraoperative myocardial infarction, and myocardial necrosis also negatively affect survival in patients who receive ventricular assist devices for PCCS.
Between August 1990 and February 1997, 84 patients underwent implantation of the Thermocardiosystems Incorporated (TCI; Woburn, MA) Heartmate left ventricular assist device (LVAD) at our institution, with an overall survival rate to transplantation or explanation of 79% [15]. The acceptably low thromboembolism rate of 0.015 events per patient-month of support [15, 16] and the facilitation of early progressive rehabilitation [17] has made implantable devices an appealing option as a bridge to both transplantation and myocardial recovery.
In an attempt to improve the relatively poor survival of patients with PCCS, we initiated a program of early TCI LVAD implantation in patients who have circulatory failure after having undergone high-risk coronary artery bypass grafting (CABG). Herein we report on 12 patients with PCCS who were supported with the TCI LVAD.
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Patients and Methods |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Eleven of the patients were men, with a mean age of 55 ± 6 years (range, 47 to 62 years). Nine of the patients underwent high-risk elective CABG, 2 underwent reoperative CABG, and 1 underwent emergency CABG after failed percutaneous transluminal coronary angioplasty (Table 1
). Six of the patients underwent their initial operation at our institution and the other 6 were transferred from referral hospitals for further management after temporary stabilization.
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). Seven patients had IABP placement, 3 patients were transferred from outside referral hospitals on short-term external LVAD support (1 ABIOMED [ABIOMED Cardiovascular, Danvers, MA], 1 BioMedicus [Medtronic Biomedicus, Inc, Eden Prairie, MN]), and 2 patients had no additional mechanical circulatory support before TCI LVAD implantation.
The median period from CABG to TCI LVAD implantation was 3.5 days, and 11 patients (92%) were intubated for 3.1 ± 2.0 days before implantable LVAD insertion. Hemodynamic indices before LVAD insertion included a systolic blood pressure of 92 ± 20 mm Hg, a left ventricular ejection fraction of 0.16 ± 0.06, a cardiac index of 1.7 ± 0.5 L • min-1 • m-2, and a central venous pressure of 17 ± 3 mm Hg (Table 2). Preoperative laboratory values were significant for elevations in prothrombin time (9 patients receiving heparin), serum creatinine, serum aspartate transaminase/alanine transaminase, and white blood cell count (Table 3). Of the 12 LVADs implanted, 8 were pneumatic and 4 were vented electric devices.
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Statistics
All results are recorded as the mean plus or minus the standard deviation. Continuous variables were analyzed by the paired Student's t-test. Fisher's exact test for 2 x 2 tables was used for categorical variables. Analysis was considered significant at a p value of 0.05 or less.
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Results |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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). Prothrombin time, aspartate transaminase/alanine transaminase, and serum creatinine likewise showed trends toward normalization at the time of intensive care unit discharge, although none of these improvements reached statistical significance (Table 3). Patients were intubated after operation for a mean of 6.6 ± 6.2 days (range, 1 to 21 days), and they had a mean intensive care unit stay of 12.6 ± 5.8 days (range, 5 to 24 days). The mean duration of LVAD support was 103 ± 62 days (range, 2 to 225 days). Nine patients underwent successful transplantation and 1 patient underwent explantation, for an overall survival-to-discharge rate of 82%. The patient who underwent explantation required device removal for device endocarditis after 4 months of support. This patient experienced malignant ventricular arrhythmias before device insertion in the setting of a depressed ejection fraction. During ventricular support, the patient's arrhythmias were managed well. At the time of device removal, acute measures of cardiac function had normalized substantially. It was elected to forego transplantation for explantation. This patient has recovered to New York Heart Association class II heart failure 18 months after device removal and has an ejection fraction of 0.50 by multigated angiography. The 9 patients who underwent transplantation remain alive and well through a mean follow-up period of 20 ± 13 months.
There was 1 death in a patient who was transferred from an outside hospital in cardiogenic shock on IABP support after reoperative CABG. This patient experienced cardiac arrest on transport to the operating room for LVAD placement. After LVAD implantation, right ventricular failure necessitated the placement of an ABIOMED right ventricular assist device (ABIOMED Cardiovascular, Danvers, MA). A profound coagulopathy subsequently developed and necessitated extracorporeal membrane oxygenation for severe hypoxia. At the family's request, support was discontinued. A second death occurred in a patient who was transferred to our institution on external LVAD support after failure to wean from cardiopulmonary bypass. The patient was bridged successfully to an implantable device and was supported for 100 days. However, while in the hospital, the patient had an upper gastrointestinal hemorrhage resulting in hypoxia, decreased LVAD flows, and unresuscitatable cardiopulmonary arrest.
Intraoperative right heart failure occurred in 2 patients. This was managed with a right ventricular assist device in 1 patient and with inhaled nitric oxide in the other. Complications included one episode of device-related thromboembolism, for an incidence of 0.025 events per patient-month of support (Table 4). This patient experienced a cerebrovascular accident on postoperative day 60 in the setting of an LVAD pocket infection and suspected LVAD endocarditis. A follow-up echocardiogram and cardiac catheterization revealed no evidence of native or device valvular vegetations. There were two device infections and three additional driveline infections. Other complications included one episode each of deep vein thrombosis, heparin-induced thrombocytopenia, and renal insufficiency secondary to aminoglycoside toxicity. There were 3 patients with sacral decubitus pressure ulcers and 1 patient who required a tracheostomy for prolonged mechanical ventilation. No patients required dialysis in the preoperative or postoperative period.
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Comment |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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In the acute setting, the placement of a short-term external LVAD often proves lifesaving. These devices are inserted easily and can be used in centers that do not have long-term ventricular assist devices. Pneumatic pulsatile pumps such as the ABIOMED also might benefit community hospitals that do not have the technical manpower to operate centrifugal pumps or long-term implantable LVADs. Nonetheless, external LVADs provide only short-term support, during which time ventricular recovery may not be achieved. Emergency heart transplantation has been advocated by some in the setting of PCCS [21]. However, the high mortality rate of heart transplantation in the setting of preoperative intubation and end-organ failure wastes the precious resource of available donor hearts.
Conversion to an implantable device after temporary stabilization with an IABP or an external LVAD allows for prolonged support times and improved survival compared with temporary support alone. However, the ability to perform early interventions is critical to ensuring this survival advantage. Among the 6 patients who underwent their initial operation at our institution, the median time to TCI LVAD insertion was 2.5 days. Intervention with an implantable device results in immediate unloading of the failing left ventricle and restoration of end-organ function. Furthermore, therapeutic strategies including the use of aprotinin, inhaled nitric oxide, and arginine vasopressin, have allowed us to avoid the negative survival determinants of bleeding, need for biventricular support, and renal insufficiency. Attention to technical detail also has been critical in ensuring success. In the setting of myocardial damage and recent myocardial infarction, the sewing ring must be secured to the left ventricular apex with large, pledgeted bites and a short inflow conduit.
Our results with the use of mechanical circulatory assistance in the setting of PCCS are remarkably similar to those obtained in our overall experience (Table 4). Thromboembolism rates remained extremely low despite the use of little or no anticoagulation. Of the five thromboembolic events that occurred in our overall experience (0.0147 events per month of patient support), three occurred in the setting of device endocarditis. The one event in this series again occurred in a patient with a pocket infection and suspected device endocarditis. Device-related infections were slightly more prevalent in the PCCS cohort, but this difference failed to reach statistical significance. Finally, it is interesting to note that only 1 patient in this series required right ventricular assistance for right ventricular failure. This is in accordance with our overall LVAD experience, in which only 5 of 29 patients with right ventricular failure required a right ventricular assist device. The judicious use of inhaled nitric oxide has reduced further the need for right ventricular assist device placement over our past 40 LVAD insertions.
Postcardiotomy cardiogenic shock remains a difficult problem with a high mortality rate and a significant morbidity rate. However, rapid and logical decision-making can result in improved survival. As opposed to the usual cohort of LVAD recipients, patients who experience PCCS usually are fairly healthy before operation, without chronic debilitation or end-organ injury. Therefore, early mechanical support results in rapid return of normal end-organ function. Return of cardiac function after mechanical unloading is well documented [22]. However, the ability to wean a patient off temporary assistance early (within 3 to 5 days) is dependent on both preoperative ventricular function and the degree of intraoperative myocardial injury. Decisions regarding conversion to an implantable device should be made within several days of temporary external LVAD assistance. In the present series, most patients received a device within 48 hours of temporary external LVAD placement or within 72 hours of initial cardiotomy.
On the basis of our experience with mechanical circulatory assistance in the setting of PCCS, we have devised an algorithm for use in managing such patients (Fig 1). Patients with severely depressed ventricular function before operation who are considered to be at high risk for postoperative ventricular failure should have either permanently implantable or short-term mechanical support systems available at the time of operation. Mechanical prostheses should be avoided because the risk of infection would be increased greatly if mechanical assistance should become necessary. During operation, the decision to use temporary mechanical assistance usually is governed by the inability to maintain an appropriate cardiac output or systolic blood pressure despite maximal inotropic support and IABP placement. In the immediate postoperative period, the need for mechanical support should be assessed by measures of end-organ function. Serious acidosis, a myocardial oxygen consumption of less than 50%, the onset of renal failure, hypoxia, and coagulopathy all are indicators that survival will be dependent on mechanical assistance. In patients with normal preoperative ventricular function, we advocate the placement of a short-term device with hopes of early ventricular recovery and subsequent device withdrawal. If the patient is considered to be an appropriate potential transplant candidate and is undergoing high-risk CABG with LVAD backup, the insertion of an implantable device at this time also is an option. At our institution, we recently adopted a policy of using TCI LVAD backup for high-risk patients, with plans for TCI insertion should circulatory failure ensue. This has allowed preoperative discussions with the patient and family about mechanical support, transplantation, and advanced medical directives.
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Finally, patients who are placed on temporary external LVADs who are not transplant candidates and cannot be weaned in the early postoperative period have few options. Discussions with the family should be initiated and device withdrawal may be necessary in this setting. It is hoped that in the future, implantable LVADs can be offered to such patients as destination therapy for end-stage heart disease. Trials to answer this question are ongoing, and such treatments soon may be possible for those patients who have no other alternatives [24].
Long-term outcome after PCCS is improved substantially with the use of an implantable LVAD early in the postoperative course. Implantable LVAD support should be considered as an initial treatment option in patients who are unresponsive to IABP and ionotropic support when ventricular recovery is not expected. The technical challenges of TCI device insertion are a major limitation to its use in the emergency setting, leading us to advise short-term device insertion for acute stabilization. In conclusion, either the presence of an implantable device at the operating facility or access to a center to which a patient can be referred rapidly is an important consideration before undertaking high-risk CABG.
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Footnotes |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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References |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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