Ann Thorac Surg 2005;80:543-547
© 2005 The Society of Thoracic Surgeons
Original article: Cardiovascular
A Multidisciplinary Network To Save the Lives of Severe, Persistent Cardiogenic Shock Patients
Aly El-Banayosy, MD
*
,
Dagmar Cobaugh, MD,
Armin Zittermann, PhD,
Lukasz Kitzner, MD,
Latif Arusoglu, MD,
Michiel Morshuis, MD,
Hendrik Milting, PhD,
Gero Tenderich, MD,
Reiner Koerfer, MD
Department of Cardiothoracic Surgery, Heart Center North-Rhine Westfalia, Ruhr University of Bochum, Bad Oeynhausen, Germany
Accepted for publication March 7, 2005.
* Address reprint requests to Dr El-Banayosy, Department of Cardiothoracic Surgery, Heart Center North-Rhine Westfalia, Ruhr University of Bochum, Georgstrasse 11, D-32545 Bad Oeynhausen, Germany (Email: abanayosy{at}hdz-nrw.de).
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Abstract
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BACKGROUND: Severe, persistent cardiogenic shock is associated with very high morbidity and lethality. We therefore tried to improve the outcome of these patients using a network between local hospitals and a specialized heart center that has facilities for transplantation and ventricular assist device (VAD) implantation.
METHODS: Between 1998 and 2000, 50 patients, who were in cardiogenic shock (mean age 49 years, SD 14) despite high doses of at least three inotropic agents, were admitted to our specialized heart center. During the first 12 hours, we tried to stabilize the patient’s condition, to reduce inotropic support agents, and to keep cardiac index above 2.4 L·min–1
·m–2. According to this strategy, patients were allocated to medical treatment only, emergency VAD therapy, urgent VAD implantation, or heart transplantation. To assess variables potentially influencing patients’ outcome, we performed univariate and multivariate analyses.
RESULTS: Early in-hospital mortality was 36% and late mortality was 10%. Overall survival at 1, 6, and 12 months of follow-up was 70%, 56%, and 52%, respectively. Even when the heart transplant patients were excluded, overall 12-months survival after cardiogenic shock was still 50%. Higher age, and the absence of sinus rhythm were the only independent risk factors for 12-month mortality.
CONCLUSIONS: Our data show that a network between cardiology departments of local hospitals and specialized heart centers can be life-saving for severe, persistent cardiogenic shock patients.
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Introduction
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A variety of cardiovascular conditions such as myocardial infarction, dilatative cardiomyopathy, and myocarditis can lead to cardiogenic shock. According to the SHOCK trial [1], clinical criteria for cardiogenic shock are a systolic blood pressure less than 90 mm Hg for 30 minutes before inotropes/vasopressors, the requirement of vasopressors or intra-aortic balloon pumping to maintain systolic blood pressure at 90 mm Hg or more, evidence of decreased organ perfusion, and heart rate of 60 beats per minutes or less. Hemodynamic criteria for cardiogenic shock are a pulmonary capillary wedge pressure of 15 mm Hg or more and a cardiac index of 2.2. L·min–1
·m–2 or less [1]. In earlier studies, unacceptably high morbidity and mortality rates of cardiogenic shock patients have been reported, irrespective of the etiology and despite advanced interventive measures [2–7]. Although the overall incidence of cardiogenic shock remains unchanged, mortality rates from this clinical entity appear to be declining [8, 9]. In the SHOCK trial, 1-year survival was 34% and 47%, respectively, depending on the strategy of emergency therapy [1].
Usually, patients with acute cardiogenic shock are transported to local hospitals. However, a significant percentage of the patients remain in cardiogenic shock, despite therapy with inotropic support agents and intra-aortic balloon pumping (IABP). Therefore, these patients (designated severe, persistent cardiogenic shock patients) often need a ventricular assist device (VAD) system and sometimes need heart transplantation to save them. However, most local clinics do not have the possibility to implant VAD systems or to perform heart transplantation. Consequently, these patients usually die in the local hospital. A network between cardiologists from local hospitals and specialized heart centers with experience in the management of severe, persistent cardiogenic shock patients including heart transplantation and VAD programs might improve the outcome of these patients. Since 1994, we have established a network at the Heart Center Northrhine Westfalia, Germany, for further treatment and diagnosis of severe persistent cardiogenic shock patients [10]. The present investigation was aimed at evaluating 1-year survival of the patients who were admitted to our hospital. Moreover, we assessed the impact of variables potentially influencing patients’ outcome.
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Material and Methods
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Multidisciplinary Network and Management Protocol
Our network consists of 20 cardiologic clinics including several university hospitals. All these other clinics have heart failure programs and heart failure cardiologists by themselves. Only severe, persistent cardiogenic shock patients who have already received multiple medications including high doses of at least three inotropic support agents and several interventive measures are admitted to us (Fig 1). The severe, persistent cardiogenic shock patients who are hemodynamically stable are transferred to our center by regular ambulance or helicopter. For the patients who are hemodynamically unstable, however, a mobile specialized mechanical circulatory support team at our clinic is responsible for the transport of these selected patients from the emergency hospital to our specialized center. The team consists of a cardiac surgeon, an emergent interventional cardiologist, an intensivist, and a VAD coordinator.
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Fig 1. Management protocol for severe, persistent cardiogenic shock patients. (IABP = intra-aortic balloon pump; VAD = ventricular assist device.)
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Severe, persistent cardiogenic shock patients need rapid intervention to restore adequate circulation. This is a key for successful management. The management at our specialized heart center includes an evaluation protocol during the first 6 hours after admission and a decision-making protocol from 6 hours until 12 hours after admission.
Evaluation and decision-making protocol
Directly after admission we try to stabilize the hemodynamics to achieve a cardiac index greater than 2.4 L·min–1
·m–2, a mean arterial pressure greater than 60 mm Hg, and a urine output greater than 30 mL/h. This strategy is performed in two ways: First, we implant IABP in all patients admitted without pump. Second, we try to modify inotropic support agents and vasoactive drugs. In the meantime, social history, and brain, kidney, liver and gastrointestinal functions are assessed by routine clinical methods to evaluate those patients who are candidates for VAD therapy and for cardiac transplantation. Since all admitted patients are on very high doses of inotropic support agents and vasoactive drugs, our main effort is to reduce these high doses from 6 hours until 12 hours after admission and to keep cardiac index above 2.4 L·min–1
·m–2. When this is not possible, an emergent VAD system is applied.
Patients
From January 1998 to December 2000, 50 patients with severe, persistent cardiogenic shock despite apparently maximal medical treatment were referred to our intensive care unit for further diagnoses and treatment. None of the patients died during transfer. Moreover, none of the patients has been rejected because of severity of illness. The patients’ mean age was 49 years (SD 14). Characteristics of that cohort are presented in Table 1. The majority of the patients were male (76%). In most patients, the etiology of cardiogenic shock was acute myocardial infarction, followed by idiopathic dilatative cardiomyopathy, fulminate myocarditis, and ischemic dilated cardiomyopathy. Nineteen of the 22 patients with acute myocardial infarction have had an anterior wall infarction. Fifteen of these 22 patients (68.2%) have had rescue percutaneous transluminal coronary angioplasty (PTCA). Several patients had a history of concomitant chronic diseases such as hypertension, insulin-dependent diabetes mellitus, and stroke (Table 1). Some patients have had previous concomitant cardiac procedures such as implantation of a defibrillator and cardiac surgery. The vast majority of the patients needed emergency ventilatory support, nearly 50% required IABP, 38% needed continuous venovenous hemofiltration, and 16% depended on coronary artery bypass grafting. Four patients (8%) have already had cardiopulmonary resuscitation. Twenty-one patients (42%) were hemodynamically very unstable and needed the intervention of our mechanical circulatory support team to secure the transport to our hospital. On admission, all patients were on high doses of at least three inotropic agents. Mean doses of inotropic support agents were: adrenaline 0.33 µg·kg–1
·min–1 (SD 0.24 µg·kg–1
·min–1), dopamine 8.8 µg·kg–1
·min–1 (SD 5.5 µg·kg–1
·min–1), dobutamine 8.6 µg·kg–1
·min–1 (SD 4.2 µg·kg–1
·min–1), and nor-adrenaline 0.25µg·kg–1
·min–1 (SD 0.34 µg·kg–1
·min–1). Echocardiography of the patients revealed a mean left ventricular end diastolic diameter of 66 mm Hg (SD 12 mm Hg). Despite inotropic support, systolic arterial pressure was only 83 mm Hg (SD 13 mm Hg), and mean arterial blood pressure was only 60 mm Hg (SD 12 mm Hg) on admission. Left ventricular ejection fraction was 24% (SD 13%), pulmonary artery pressure was 33 mm Hg (SD 11 mm Hg), pulmonary artery wedge pressure was 20 mm Hg (SD 7 mm Hg), and cardiac index was 2.6 L·min–1
·m–2 (SD 1.0 L·min–1
·m–2).
To assess variables potentially influencing patients’ outcome, we performed univariate and multivariate analyses. Variables tested were as follows: absence of sinus rhythm on admission, sex, previous cardiac surgery, need for cardiopulmonary resuscitation, renal replacement therapy, left ventricular ejection fraction, pulmonary artery pressure, left ventricular end diastolic diameter, pulmonary artery wedge pressure, cardiac index, percutaneous cardiopulmonary bypass, etiology of cardiogenic shock, VAD therapy, acute myocardial infarction, insulin-dependent diabetes mellitus, hypertension, ventricular tachycardia, IABP, mean arterial blood pressure on admission, systolic arterial blood pressure, and ventilatory support.
Statistics
Statistical evaluations were performed with the Statistical Package for Social Sciences, version 11 (SPSS, Chicago, Illinois). Survival rates were calculated with the Kaplan-Meier product-limit estimator. The log-rank test was used to test for differences in survival rates of specific subgroups. Associations of factors with long-term survival were first tested in a univariate Cox regression model. Every univariate variable showing marginal significance (p < 0.15) was then tested in a Cox multivariate model and removed stepwise if no significant influence was proved. A p value less than 0.05 was considered statistically significant.
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Results
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The outcome of the patients is given in Figure 2. According to our protocol and decision tree, we could classify our patients into two groups. Group 1 (n = 6) failed to show improved hemodynamics with medical treatment. Therefore, patients received initial emergency VAD therapy. Four of these 6 patients died, while 2 patients could be transplanted later on. Group 2 (n = 44) could initially be successfully stabilized with optimal medical treatment. Of these 44 patients, 9 patients died. Sixteen patients could be weaned from inotropic support and recovered from cardiogenic shock. They were discharged at home. In 6 other patients who remained on low-dose inotropic support agents, heart transplantation became available. Mean time until heart transplantation was 54 ± 30 days (range, 26 to 94). Five of these 6 patients could be discharged at home, and 1 patient died. Because heart transplantation was initially not available, 13 patients who could not be weaned from moderate inotropic support received late urgent VAD therapy. Mean time until VAD implantation was 6 ± 6 days (range, 1 to 21). Of the 13 patients, 4 patients were transplanted later on, 5 patients could be weaned later on, and 4 patients died. The VAD systems applied were Thoratec (Thoratec Inc, Pleasanton, CA) (n = 6 LVAD; n = 5 BiVAD), Novacor LVAS (World Heart Inc, Oakland, CA) (n = 2), Heart Mate 1 (Thoratec Inc) (n = 2), and CardioWest TAH (SynCardia Systems Inc, Tucson AZ) (n = 4). The criteria for the selection of the type of the VAD system has been described elsewhere [11, 12].
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Fig 2. Outcome of patients with severe, persistent cardiogenic shock. (HTx = heart transplantation; VAD = ventricular assist device.)
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Early in-hospital mortality was 36% (18 patients). The causes of death were multiple organ failure (16 patients) and mesenteric ischemia (2 patients). Sixteen patients (31%) with VAD implantation or heart transplantation and 16 patients (31%) with optimal medical treatment survived their in-hospital stay (Fig 2). Late mortality rate after discharge, including after heart transplantation and VAD patients, was 10% (5 patients). The causes of late follow-up deaths were cardiac failure (2 patients), pneumonia (1 patient), renal failure (1 patient), and gastrointestinal bleeding (1 patient). Overall survival at 1, 6, and 12 months was 70%, 56%, and 52%, respectively (data not shown). Even when the heart transplant patients were excluded, survival rate at 12 months of follow-up was still 50% (Fig 3).
In a multivariate Cox proportional hazard analysis, age and the absence of sinus rhythm were the only risk factors of 12-month mortality (Table 2). Our data demonstrate that the relative risk of death during 12 months of follow-up was approximately 2 times higher in the absence of sinus rhythm, and increased by 7.1% with each year of age.
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Table 2. Relative Risks and 95% Confidence Intervals (CI) for 12-Month Mortality According to Absence of Sinus Rhythm and Age
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Comment
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Our multidisciplinary approach through a network including cardiologists and a specialized cardiac center was based on the assumption that such a network might decrease the fatal outcome of severe, persistent cardiogenic shock patients. In the present study, we could demonstrate that our approach indeed leads to the survival of a significant number of patients with severe persistent cardiogenic shock. It should be mentioned that the status of this cohort was very precarious: On admission, 46% of the patients required rescue IABP and 86% required ventilatory support. Moreover, 8% of the patients needed reanimation and 16% needed percutaneous cardiopulmonary bypass. Therefore, our data are very encouraging. Our cohort of patients is not comparable with the patients of the SHOCK trial. One inclusion criteria in that earlier study was a systolic blood pressure less than 90 mm Hg for 30 minutes before inotropes/vasopressors, or vasopressors or IAPB were required to maintain systolic blood pressure at 90 mm Hg or higher [1]. In the patients of our study, however, systolic arterial blood pressure was only 83 ± 13 mm Hg, although the patients were on high doses of at least three inotropic support agents. Moreover, in the SHOCK trial all patients of the revascularization treatment arm received emergency early PTCA/CABG, while in our study 68% of the patients with myocardial infarction needed rescue PTCA.
In the SHOCK trial, overall survival at 1, 6, and 12 months of follow-up was 53%, 50%, and 47%, respectively, in the emergency revascularization arm and 44%, 37%, and 34%, respectively, in the initial medical stabilization arm [1, 13]. Compared with that earlier study, the overall survival at 1, 6, and 12 months in our study of 70%, 56%, and 52% was excellent, given the precarious medical status of our patients.
One reason for the relatively low mortality of our patients is the possibility to perform VAD implantations and heart transplantations at our heart center. Indeed, 11 patients survived because of successful emergency or urgent VAD implantation and 11 patients survived because heart transplantation became available (Fig 2). However, our data also demonstrate that the lives of 16 patients could be saved with optimal medical treatment only. Obviously, we were able to accumulate a lot of experience through the network to successfully wean a significant number of severe, persistent patients from high inotropic support agents and to discharge them at home. We are planning to use our experience to teach the doctors of the local hospitals to improve their medical treatment of severe, persistent cardiogenic shock patients. Moreover, it is our strategy that only those severe, persistent cardiogenic shock patients are admitted to our heart center, who presumably need VAD implantation or heart transplantation to rescue them.
Cardiologists should use the possibility to send severe, persistent cardiogenic shock patients to a specialized cardiac center with VAD and heart transplantation facilities in order to improve the outcome of these patients. As early treatment is essential and sufficient time to observe the patient and to make decisions about the best therapeutic strategy is also important, the transport of severe, cardiogenic shock patients has to be performed very rapidly and safely. A mobile specialized team with experience in mechanical circulatory support should be responsible for the transport of those patients to the specialized center, who are hemodynamically very unstable. In our opinion, an established network is an optimal guarantee for a successful therapy of severe, persistent cardiogenic shock patients and also for an optimal use of medical resources.
In view of the disastrous condition of the patients before transport, the survival rate of more than 50% 1 year after the cardiogenic shock justifies the employment of immense financial and staff resources. As expected, age was identified as a risk factor for mortality after cardiogenic shock. Thus, our data demonstrate that the procedure should be restricted to younger patients in whom organ recovery is more likely. In Germany, for example, approximately 12,000 patients less than 65 years of age died from cardiogenic shock due to myocardial infarction in 2001, given an incidence of this cause of death of 0.015% in the general population [14]. Acute myocardial infarction was the cause of cardiogenic shock in only 44% of our patients. As we observed no difference in survival between patients with acute myocardial infarction and other reasons of severe cardiogenic shock, our network can be life-saving for patients independent of the etiology of severe, persistent cardiogenic shock. Provided that more networks can be established in future, it may be possible to rescue a large number of these patients.
In our study, even early in-hospital death was independent of cardiac reasons, but rather, was due to toxic catecholamine-induced ischemia and to preexisting multiple organ failure. Moreover, late death was caused by other reasons than cardiac failure in 3 of the 5 patients who died (see Results section). It is also noteworthy that of the 50 patients with severe persistent cardiogenic shock, 21 could be discharged to home with their own heart (Fig 2). These results further demonstrate that the experience with an optimal medical treatment and the availability of specific therapeutic procedures at a specialized cardiac center can be life-saving and has an immense impact on the quality of life of these patients and their family.
The absence of sinus rhythm as a risk factor for 12-month mortality is unclear at present and needs further evaluation.
In summary, early as well as late medical results emphasize the multidisciplinary and network approach to improve the outcome of cardiogenic shock patients. In future studies, further improvements of medical treatment as well as the optimal time span between admission and implantation of VADs should be evaluated. Moreover, the optimal VAD systems, including system-related survival, and quality of life has to be assessed.
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Abstract
Introduction
