Author + information
- Received October 8, 1996
- Revision received January 31, 1997
- Accepted February 20, 1997
- Published online June 1, 1997.
- Paul J Kovack, DOA,
- Mark A Rasak, DOA,
- Eric R Bates, MD, FACCB,
- E.Magnus Ohman, MD, FACCC and
- Robert J Stomel, DO, FACCA,*
- ↵*Dr. Robert J. Stomel, 28080 Grand River, Suite 300 West, Farmington Hills, Michigan 48336.
Objectives. We sought to explore the potential benefit of combining intraaortic balloon counterpulsation (IABP) with thrombolysis for acute myocardial infarction (MI) complicated by cardiogenic shock.
Background. In community hospitals, this condition is usually managed with thrombolysis alone.
Methods. We reviewed the charts of 335 patients from two community hospitals who presented with acute MI and had cardiogenic shock between 1985 and 1995.
Results. Of 46 patients who underwent thrombolysis within 12 h of acute infarction with confirmed cardiogenic shock, 27 underwent IABP and 19 did not. Age, systolic blood pressure with shock, pulmonary artery catheter use, pulmonary capillary wedge pressure and the incidence of diabetes mellitus and anterior MI did not differ between groups. Patients treated with IABP were somewhat more likely to have prior MI and had a significantly greater cardiac index (2.0 vs. 1.5 liters/min per m2, p = 0.04). Although no deaths occurred within 2 h of presentation, patients not treated with IABP tended to die earlier (6.8 ± 5 vs. 23.8 ± 19 h, p = 0.13). Patients treated with IABP had a significantly higher rate of community hospital survival (93% vs. 37%, p = 0.0002), and more of them were transferred for revascularization (85% vs. 37%). Of 30 patients transferred for revascularization, 27 underwent angioplasty or bypass surgery; hospital survival was 74%. Patients treated with IABP also had a significantly higher overall hospital and 1-year survival rate (67% vs. 32%, p = 0.019).
Conclusions. Survival may be enhanced and transfer for revascularization facilitated when community hospitals use both thrombolysis and IABP to treat patients with acute MI complicated by cardiogenic shock.
(J Am Coll Cardiol 1997;29:1454–8)
The survival rate for cardiogenic shock in most hospitals has changed little over the last few decades (). Although thrombolytic therapy has revolutionized the treatment of community hospital patients with myocardial infarction (MI) ([2–5]), those whose infarction is complicated by severe left ventricular failure and hypotension are rarely helped by this treatment strategy alone ([6, 7]), perhaps because of low infarct artery patency rates ([8, 9]). It is therefore not surprising that cardiogenic shock is responsible for 58% of all hospital deaths from infarction ([7, 10]) and has a survival rate of <20% in most community hospitals ().
Intraaortic balloon counterpulsation (IABP) theoretically should benefit these patients, because it increases diastolic blood pressure and significantly diminishes the work of the heart by decreasing afterload. Unfortunately, prethrombolytic-era randomized trials ([11, 12]) failed to show that IABP reduced mortality in cardiogenic shock. The use of IABP in the thrombolytic era was discouraged after it was shown to be an independent predictor of hemorrhagic complications (). This has led to a reduction in its use for cardiogenic shock after thrombolysis in the United States (32% incidence) and elsewhere (7% incidence) ().
Recent observational studies suggest that IABP combined with thrombolytic therapy can be safe ([15, 16]) and reduce mortality ([17, 18]) in cardiogenic shock. IABP is also an important method of stabilizing patients until they can be transferred to tertiary care centers for acute revascularization. To further evaluate the potential survival benefit of a strategy combining IABP with thrombolysis in patients with MI and cardiogenic shock who present to a community hospital within 12 h of symptom onset, we performed a retrospective hospital chart review.
We reviewed 335 hospital records that had discharge diagnosis codes for cardiogenic shock and MI from two community hospitals (Botsford General Hospital, Garden City Hospital) over the 10-year period from 1985 to 1995 (Fig. 1). Of these, 255 patients had confirmed cardiogenic shock, defined as systolic blood pressure <90 mm Hg for >30 min not responsive to fluid therapy alone, thought to be secondary to cardiac dysfunction and associated with either signs of hypoperfusion (cold, clammy skin, oliguria or altered sensorium) or a cardiac index <2.2 liters/min per m2(in patients who underwent IABP, the cardiac index was measured during IABP). The remaining 80 patients had shock due to septicemia or hypovolemia. One-hundred ninety-one patients also had ST segment elevation (≥1 mm in two consecutive leads) or left bundle branch block, had cardiac enzyme levels consistent with acute MI and were eligible for thrombolytic therapy. Only 65 patients (34%) received thrombolytic therapy. Nineteen patients were excluded because thrombolytic therapy was started >12 h after initial symptom onset. Therefore, 46 patients formed the study group.
None of the patients had a contraindication for IABP insertion. In all cases, the initial arterial puncture was achieved with a modified Seldinger technique through the anterior femoral artery wall with an open-ended arterial needle.
All therapies and clinical events were recorded from both the community hospital and tertiary hospital (University of Michigan Medical Center, Ann Arbor) records. Late end points were obtained from the follow-up physician’s office chart. Patients were followed up for a minimum of 1 year.
1.1 Statistical Analysis.
The primary end points were community hospital survival and 30-day and 1-year mortality. Left ventricular ejection fraction at ≥6 months was also evaluated by multigated acquisition scan, echocardiogram or contrast left ventriculogram.
Continuous variables were compared with a Student ttest (two-tailed). Categoric variables were compared with a chi-square test. Continuous variables are reported as mean value ± SD. Categoric variables are reported as frequencies and percentages. A p value < 0.05 was considered significant.
Of the 46 study patients, 27 received both thrombolytic therapy and IABP; 19 received thrombolytic therapy alone. The groups did not differ significantly by age, systolic blood pressure with shock, time to thrombolytic treatment, the proportion of male patients or the incidence of anterior MI (Table 1). Patients treated with IABP had a slightly greater incidence of prior MI and presented significantly more often with Killip class I. Balloon pumps were placed an average of 3.2 h after thrombolytic therapy (an average of 5.7 h from the onset of chest pain).
The use of pulmonary artery catheters was similar between groups, but more patients treated without IABP required mechanical ventilation and vasopressor therapy (Table 2). In the 16 patients from the community hospital who had a pulmonary artery catheter placed, mean pulmonary capillary wedge pressure (after balloon inflation in patients with IABP) did not differ with the use of IABP, but the cardiac index (during IABP use) was higher in patients treated with IABP (mean 2.0 vs. 1.5 liters/min per m2, p = 0.041).
Community hospital complications are shown in Table 3. Patients not treated with IABP had somewhat more asystole and significantly more atrioventricular block than patients so treated. The complications associated with IABP use were infrequent (15% overall).
All patients in both treatment groups survived ≥2.2 h after admission to the emergency department. The shortest time from the identification of cardiogenic shock to death was 1.8 h, allowing enough time for insertion of a balloon pump in both groups. The mean time from emergency department presentation to balloon pump insertion was 4.4 h. Among patients who died in the community hospital, the time from chest pain to death, emergency department presentation to death and diagnosis of cardiogenic shock to death did not differ between treatment groups (Table 4).
Significantly more patients treated with IABP survived the community hospital stay (93% vs. 37% treated without IABP, p = 0.0002) (Table 4, Fig. 1). Four patients treated with IABP remained in the community hospital; two survived. Of the 12 patients not treated with IABP who remained in the community hospital, none survived.
Thirty patients (65%) were transferred to a tertiary care center, and 22 (73%) survived. More patients treated with IABP were transferred for revascularization (85% vs. 37%). Of the 23 patients treated with IABP who were transferred, 16 (70%) survived compared with 6 (86%) of 7 transferred patients not so treated. Twenty-seven (90%) of the 30 patients who were transferred underwent either coronary angioplasty or bypass surgery. Eight (67%) of 12 patients who underwent angioplasty, 10 (83%) of 12 who underwent bypass grafting and 2 (67%) of 3 who underwent both procedures survived, for an overall survival rate with revascularization of 20 (74%) of 27. The overall hospital and 1-year survival rate was 67% in patients treated with IABP versus 32% in those not so treated (p = 0.019).
The ejection fraction beyond 6 months was evaluated in 10 patients (56%) treated with IABP and 5 (83%) treated without IABP; the results did not differ significantly (42 ± 13% vs. 45 ± 21%, p = 0.79).
Each year, up to 70,000 patients die of MI complicated by cardiogenic shock (). Most of these patients are first treated in a community hospital, where angiographic and surgical facilities may be unavailable. Treatment options in these centers include thrombolytic therapy or immediate transfer to a tertiary care facility for angiography and revascularization, but many patients will remain at the local hospital because physicians are reluctant to transfer hemodynamically unstable patients. This observational study suggests that when early IABP support is used in conjunction with thrombolysis, short- and long-term survival can be enhanced, primarily because of the increased opportunity for transfer and revascularization.
Thrombolysis alone may not reduce mortality in these high risk patients (), and IABP alone has not proved to be an effective alternative. Two small randomized trials ([11, 12]) that each examined <50 patients with MI and cardiogenic shock showed no survival benefit with IABP, but both trials were performed before thrombolytic therapy became the standard treatment for MI. More recent observational data suggest that IABP can be used safely ([15, 16]) and may reduce mortality in patients with MI complicated by cardiogenic shock ([17, 18]). These findings may be a result of enhanced thrombolysis, improved infarct artery patency, decreased reocclusion, or supported ventricular function (while ischemically stunned myocardium recovers). Our data support this concept: Patients who received both IABP and thrombolytic therapy rather than thrombolysis alone had better community-hospital, 30-day and 1-year survival rates.
Nonrandomized data ([18, 20]) also suggest that revascularization, when available, is associated with a survival advantage. Two multicenter international trials, SHOCK (SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK) and SMASH (Swiss Multicenter study of Angioplasty for SHock following myocardial infarction), are currently addressing this issue. Meanwhile, the decision to use thrombolytic therapy, IABP, or both, or to transfer critically ill patients to tertiary care centers for revascularization remains in dispute among community hospital physicians. It may be that the best use of IABP is as a bridge until transfer and revascularization can be performed. Of the 30 patients in our study who survived to be transferred, 23 (77%) had been treated with IABP. Of the 191 patients with shock and MI in our study, 126 (66%) did not receive thrombolytic agents. Of such patients who remained in the community hospital, only 6 (5%) survived to be discharged home. Prompt stabilization and transfer may be even more important for these patients, for whom IABP was rarely used as an initial treatment.
3.1 Preclinical Studies.
Through enhanced diastolic augmentation, IABP may improve thrombolysis () and promote coronary blood flow (), which resulted in improved survival and myocardial salvage in one study of a hypotensive canine model of MI (). In a normotensive model (), IABP reduced the reperfusion time after recombinant tissue-type plasminogen activator (rt-PA) administration from 39 to 13 min. Coronary blood flow velocity was not affected, indicating that the IABP-augmented diastolic pressure caused the improvement in rate of thrombolysis.
3.2 Previous Community Hospital Studies.
In a previous observational study at our institution (), 13 patients with MI and cardiogenic shock received thrombolytic therapy, 29 received IABP alone and 22 received both interventions. The survival rate was 68% with the combined treatments compared with 23% for thrombolytic therapy alone and 28% for IABP alone (p = 0.005). Similar to the current study, these initial observations suggest a survival advantage when IABP is combined with thrombolytic therapy. However, in contrast to the current study, cardiogenic shock developed in many of these patients >12 h after hospital admission, and 29 patients received IABP support without thrombolysis.
The complication rate of balloon pump insertion after thrombolysis was low in our two previous studies ([15, 17]). In contrast, the TAMI (Thrombolysis and Angioplasty in Myocardial Infarction) study () showed that balloon pump insertion resulted in almost a 5-fold higher risk of severe hemorrhagic or vascular complications. The disparity between the complication rate in the TAMI study and ours may be explained by our insertion technique (see Methods).
3.4 Limitations of the Study.
Our retrospective study was specifically designed to analyze the survival benefits of intravenous thrombolysis in conjunction with IABP within 12 h of symptom onset in patients with MI complicated by cardiogenic shock. We were limited by the small number of patients who manifested cardiogenic shock and received thrombolytic therapy within 12 h of symptom onset. We chose the 12-h cutoff point because of the limited benefit of thrombolysis after this time ([25, 26]). Given the nonrandomized and retrospective nature of our observations, with the inherent danger of selection bias, these data should be interpreted with some caution, although the groups were matched for variables known to predict adverse outcome in patients with cardiogenic shock. Further, both groups were attended by invasive cardiologists with expertise in cardiac catheterization and balloon pump insertion, and their treatment strategies were similar (i.e., early stabilization and transfer to a tertiary care center for intervention whenever possible). Nonetheless, large prospective randomized studies will be required to define the best treatment strategy for patients in community hospitals who have MI complicated by cardiogenic shock.
This study suggests that survival is enhanced and transfer for revascularization facilitated when patients with MI complicated by cardiogenic shock who present to a community hospital undergo thrombolysis and IABP rather than thrombolysis alone. This strategy is undergoing prospective, randomized evaluation in the Thrombolysis And Counterpulsation To Improve Cardiogenic Shock survival (TACTICS) trial.
- intraaortic balloon counterpulsation
- myocardial infarction
- Thrombolysis and Angioplasty in Myocardial Infarction
- Received October 8, 1996.
- Revision received January 31, 1997.
- Accepted February 20, 1997.
- The American College of Cardiology
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