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Ann Thorac Surg 1996;61:388-390
© 1996 The Society of Thoracic Surgeons
Departments of Thoracic and Cardiovascular Surgery Cardiology, Centre National de la Recherche Scientifique, Unité de Recherche Associée 1431, Hospital Henri Mondor, Creteil, France
Abstract
Background. Optimal timing of implantation of a mechanical circulatory support system in the treatment of acute cardiogenic shock is still unsettled. The issue has been addressed in a retrospective analysis of a group of 98 patients in cardiogenic shock refractory to medical therapy who were candidates for cardiac transplantation, admitted from 1987 to 1994.
Methods. The treatment included reinforced inotropic support by addition of phosphodiesterase inhibitors to sympathomimetic agents. The patients who did not improve were immediately brought to the operating room for mechanical circulatory support system implantation.
Results. The overall survival in the group of 28 patients selected for mechanical bridge is 50%. No predictive factors of death or multiorgan failure while on the device could be identified, suggesting a lack of contraindications to mechanical circulatory support system implantation.
Conclusions. The high death rate in patients maintained on medical therapy because of initial improvement as they are awaiting transplantation suggests the benefit of a rapid semielective implantation of an intracorporeal device.
The need for mechanical circulatory support (MCS) as a bridge to cardiac transplantation in patients in cardiogenic shock is determined by well-established clinical and hemodynamic guidelines (aortic mean pressure <85 mm Hg, pulmonary capillary wedge pressure >20 mm Hg, cardiac index <2 L•min-1•m-2 with optimal medical treatment) associated with organ dysfunction. The timing of implantation, however, is less well defined. Previous work of our group [1] confirmed by others [2, 3] has shown that optimization of sympathomimetic treatment may gain time before mechanical support is required. This strategy improves immediate survival and consequently reduces the number of patients requiring emergency circulatory support. This flexible approach of a combined pharmacologic and mechanical bridge to transplantation also allows more efficient use of limited resources. To determine the optimal timing of operation we have undertaken this retrospective analysis of our database of patients in cardiogenic shock who initially meet the criteria for MCS.
Material and Methods
Clinical Material
From 1987 to June 1994, 98 patients (89 male, 9 female; mean age, 46 ± 11 years) were referred, in cardiogenic shock unresponsive to conventional therapy, for urgent transplantation or implantation of a mechanical circulatory support system. Patients characteristics were as follows:
Cardiogenic shock was due to acute myocardial infarction in 20 and acute decompensation of a cardiomyopathy in 78 (idiopathic in 46, ischemic in 17, toxic in 4, viral in 5, valvular in 5, and hypertrophic in 1). When the patient was admitted to the intensive care unit, surgeons were called, and after a medical and surgical examination, each patient received an intravenous (IV) bolus of enoximone (1 to 2 mg/kg) according to our protocol [1]. There was no response in 31 (32%), but a dramatic improvement in 67 (68%). In the latter group, the criteria for MCS implantation were not met any more. A comparison of the patient characteristics in these two groups is given in Table 1
. Patients not responding were more likely to be anuric, require mechanical ventilation, and have no previous history of cardiac failure.
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Evaluation of Timing
Evaluation of MCS is considered to have been too late if a patient died on the device due to irreversible organ failure, loss of vascular tone, or a right ventricular failure on a left ventricular assist device associated with increased pulmonary resistances. Early implantation is evaluated by analysis of the outcome of two groups of patients. The first group comprises those who, having met the criteria for MCS system implantation, did not immediately have implantation due to improvement with pharmacologic treatment, but who finally were not suitable for transplantation due to either (1) contraindications that only became apparent with prolonged survival or (2) total recovery of native cardiac function. The second group consists of those accepted for transplantation waiting in the hospital on IV treatment (n = 26) or at home on oral treatment (n = 14).
Results
Late Implantation
Five patients (17%) died on the device due to multiple organ failure (n = 2), loss of vascular tone (n = 2), or right ventricular failure with a Novacor left ventricular assist system (n = 1). The initial diagnosis was myocardial infarction in 3 and acute decompensation in 2. Univariate analysis of preimplantation risk factors shows that although those dying were older (46 ± 12 versus 40 ± 9 years) and had worse left ventricular function (pulmonary capillary wedge pressure, 33 ± 6 versus 25 ± 7 mm Hg), they had no clinical evidence of worse organ dysfunction (proportion requiring mechanical ventilation, proportion with anuria, mean blood urea nitrogen level, creatinine level, bilirubin level not significantly different). The method of implantation may influence survival on MCS: when CPB was used, the incidence of multiorgan failure was significantly greater than when a pneumatic ventricular assist device was implanted without CPB (30% versus 11%).
Early Implantation
PATIENTS TOO SICK TO RECEIVE A TRANSPLANT.
Twenty-one patients who initially improved with optimization of medical therapy and no longer met the criteria for MCS were not suitable for transplantation because of the subsequent discovery of initially hidden contraindications while still on IV drugs (n = 11) or later, as they were weaned off IV therapy (n = 10). None of these patients but 1 survived long term (>1 year).
PATIENTS TOO WELL TO RECEIVE A TRANSPLANT.
In 6 patients, after weaning from IV drug therapy, recovery of native cardiac function was complete. The cause of the initial cardiac failure was ischemic in 1, viral in 2, and dilated cardiomyopathy in 3. All are living 1 year later and in functional class I.
PATIENTS WAITING FOR A TRANSPLANT.
Forty patients were reconfirmed as good candidates for transplantation: 26 could not be weaned off medical therapy, and 14 could be sent home on oral treatment. Eleven of the first group and 6 of the second died. In these 17 patients (42%), the ultimate treatment aim, cardiac transplantation, was not achieved because of sudden death (n = 10) or a rapid deterioration (n = 7). These patients should have received MCS but an indication that initially was not clear due to the improvement with pharmacologic treatment was ultimately lost due to the rapidity of their deterioration. Of the 23 who received a transplant, 15 were on IV therapy (9 long-term survivors) and 8 were at home (7 long-term survivors). Irreversible organ failure was the main cause of death after transplantation.
Comment
It is clear, from our experience and that of others, that MCS should be started as soon as possible: in patients not improved with medical therapy immediately and in those who are improved with medical therapy as soon as the condition is stabilized.
Implantation relatively late in the course of cardiogenic shock is more usual, however. There is no single prognostic indicator that precludes MCS; however, there are some preimplantation indices that suggest an unfavorable outcome. In a multicenter study of the Thoratec device, blood urea nitrogen level was a significant univariate and multivariate predictor, hepatic function was of predictive value, and a redo procedure more than 30 days after the original operation carried a high risk [4]. Similar findings are reported with pneumatic [5–7] and electric [8–9] left ventricular assist devices and from the European database on mechanical support [10]. In the present study, which does not have the limitations of multicenter study, age and pulmonary capillary wedge pressure are the only predictive parameters with a trend toward significance. Multiorgan failure on the device is more frequent in patients with acute myocardial infarction, suggesting that this carries a higher risk of death on the device. This is supported by the observation that patients with acute myocardial infarction are in worse condition at the time of implantation than those with more chronic cardiac failure, with a significantly higher plasma creatinine level. Interestingly, the cardiac index of patients with acute myocardial infarction (1.8 ± 0.3 L•min-1•m-2) is greater (p = 0.02) than that of patients with chronic failure (1.7 ± 0.3 L•min-1•m-2), suggesting that the rapidity of circulatory failure influences the development of organ failure and that hemodynamic indices, per se, are not sensitive indices of prognosis. We may conclude that it is never too late for MCS, especially in younger patients. The patients should always have the benefit of the doubt.
Our data also indicate that use of CPB to implant MCS systems increases the risk of irreversible organ failure and loss of vascular tone on the device. The activation of an inflammatory response with CPB may have an especially marked deleterious effect in patients with cardiogenic shock who have been already submitted to an activation process. In these patients VAD implantation without CPB is preferable to a more complicated technique using the Jarvik device or an implantable left ventricular assist system. This further clarifies the role of these systems as being more suitable for long-term implantation than last-ditch treatment.
The decision to initiate MCS may be rushed by the emotional nature of the decision and the urgency of the clinical situation. Optimizing medical treatment gains time and allows identification of patients who will ultimately not be suitable for transplantation (30%) because of associated problems (23%) or reversibility of the cardiac dysfunction (7%). For this reason we advocate use of the initial pharmacologic strategy.
The disadvantage of the pharmacologic bridge, however, is that 42% of the 40 patients who apparently improved and stabilized suddenly died before cardiac transplantation. No specific risk factor for this can be identified. This danger of the pharmacologic bridge, which we [11] and others [12] have previously identified, can be reduced by using the time gained to plan a semielective implantation of a mechanical bridge as soon as weaning of IV drugs appears difficult or it becomes apparent that rapid transplantation will not be possible.
Footnotes
Presented at The Third International Conference on Circulatory Support Devices for Severe Cardiac Failure, Pittsburgh, PA, Oct 28-30, 1994.
Address reprint requests to Dr Loisance, Centre de Recherches Chirurgicales Henri Mondor, Faculté de Médecine, CHU Henri Mondor, 8 rue du Général Sarrail, 65212 Créteil, France.
References
This article has been cited by other articles:
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  M. Kirsch, E. Vermes, C. Radu, B. Streich, K. Nakashima, A. Mekontso-Dessap, and D. Loisance Impact of preoperative hemodynamic support on early outcome in patients assisted with paracorporeal Thoratec((R)) ventricular assist device. Eur. J. Cardiothorac. Surg., August 1, 2008; 34(2): 262 - 267. [Abstract] [Full Text] [PDF]
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 A K Mahmood, J M Courtney, S Westaby, M Akdis, and H Reul Critical review of current left ventricular assist devices Perfusion, September 1, 2000; 15(5): 399 - 420. [PDF]
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 S. J. Park, D. Q. Nguyen, A. J. Bank, S. Ormaza, and R. M. Bolman III Left ventricular assist device bridge therapy for acute myocardial infarction Ann. Thorac. Surg., April 1, 2000; 69(4): 1146 - 1151. [Abstract] [Full Text] [PDF]
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