Abstract
Objectives
This study aimed to determine whether the elective insertion of an intra-aortic balloon counter pulsation (IABP) device at the time of myocardial revascularization in patients presenting with an acute anterior ST-elevation myocardial infarction (STEMI) without cardiogenic shock has any impact on the in-hospital rate of cardiac mortality.
Background
The role of IABP in patients presenting with an acute MI without cardiogenic shock remains ill defined.
Methods
The present study comprised 605 consecutive patients who underwent primary percutaneous coronary intervention for an anterior STEMI without cardiogenic shock. Patients who received IABP at the time of their coronary revascularization ( n = 105) were compared to those who had not ( n = 500). Patients with stable angina, unstable angina, non-STEMI, non-anterior STEMI, and cardiogenic shock were excluded.
Results
The two cohorts were well matched for the conventional risk factors for coronary artery disease. Although the left ventricular ejection fraction was significantly lower in the patients who received IABP (0.32 ± 0.11 vs. 0.39 ± 0.12; P < 0.001), the two cohorts were well matched for history of MI, coronary revascularization, and chronic renal impairment. Following propensity scoring, the in-hospital rate of cardiac death was similar between the two cohorts (5.6% vs. 0%; P = .12) as was the rate of vascular complications. Major bleeding was significantly greater in the IABP cohort (10.0% vs. 0%; P = .01) leading to a greater transfusion requirement (14.9% vs. 2.9%; P = .01).
Conclusion
The adjunctive use of an IABP in patients presenting with an acute anterior STEMI without cardiogenic shock may not be associated with an in-hospital mortality benefit.
1
Introduction
Since the introduction of intra-aortic balloon counter pulsation (IABP) by Kantrowitz et al. for patients with cardiogenic shock, its indications have extended to the provision of circulatory support for patients with de-compensated heart failure, postoperative left ventricular systolic dysfunction, and “high-risk” percutaneous coronary intervention (PCI) . Indeed IABP remains the most commonly used circulatory assist device in the United States with up to 30% of complex PCIs utilizing the device .
The use of IABP in patients presenting with acute myocardial infarction (MI) complicated by cardiogenic shock and undergoing PCI has become dogma . Indeed the current American College of Cardiology/American Heart Association (ACC/AHA) guidelines describe IABP therapy as a Class I indication for the treatment of shock complicating acute MI . By contrast, there is currently limited data regarding the role of IABP in patients presenting with acute ST-elevation myocardial infarction (STEMI) without cardiogenic shock who undergo primary PCI . The aim of this study was therefore to determine whether the elective insertion of an IABP device at the time of myocardial revascularization in patients presenting with an acute anterior STEMI without cardiogenic shock has any impact on the in-hospital rate of cardiac mortality.
2
Methods
This single-center, retrospective study comprised 605 consecutive patients who underwent primary PCI for an anterior STEMI without cardiogenic shock at our institution from 2003 to 2010. Within this cohort, an IABP device was inserted at the time of revascularization in 105 patients. Patients with stable angina, unstable angina, non-STEMI, non-anterior STEMI, and cardiogenic shock were excluded. All patients provided written informed consent. The study complied with the Declaration of Helsinki for investigation in human beings, and was approved by the local institutional ethics committee. The procedures were performed according to standard clinical guidelines. In all cases, the interventional strategy, as well as the use of adjunctive devices and pharmacotherapy, was at the discretion of the operating interventional cardiologist. All patients received aspirin 325 mg pre-procedure and recommended to continue this regimen indefinitely. In addition, clopidogrel 75 mg daily following a 300-mg or 600-mg loading dose was commenced pre-procedurally and recommended to continue for at least 12 months.
The analyzed clinical end points were the in-hospital rate of cardiac death, vascular complications, and major bleeding. Cardiogenic shock was defined as systolic blood pressure ≤ 90 mmHg for at least 30 min and/or presence of peripheral signs of hypoperfusion, as evidenced by peripheral vasoconstriction or urine output < 30 ml/min or altered sensorium. Hypercholesterolemia was defined as fasting cholesterol > 250 mg/dl or the use of lipid lowering therapy. Hypertension was defined as blood pressure > 140/90 mmHg or the use of anti-hypertensive therapy. Renal impairment was defined as serum creatinine > 1.2 mg/dL. Angiographic success was defined as postprocedural stenosis ≤ 30% and Thrombolysis in Myocardial Infarction Flow Grade 3. Gastrointestinal bleeding was defined as evidence of an upper (coffee ground emesis, endoscopy demonstrating active bleeding) or lower (melena, hematochezia, or endoscopy demonstrating an active bleeding site) gastrointestinal bleed. Major bleeding was defined as any combination of gastrointestinal bleeding, hematocrit drop ≥ 15% and/or a hematoma.
Statistical analysis was performed using SAS version 8.2 (SAS institute, Cary, NC). Continuous variables and categorical variables are expressed as mean ± S.D. and percentages, respectively. Student t test was used to compare continuous variables, and the chi-square test or Fisher’s exact test was used to compare categorical variables. Using propensity scoring, patients in the IABP group ( n = 70) were 1:1 matched with patients in the no IABP group ( n = 70) in order to obtain groups with similar baseline characteristics and to minimize selection bias.
To calculate the propensity score, the following variables were entered into the model: age, sex, hypertension, diabetes mellitus, hypercholesterolemia, current smoker, body mass index, left ventricular ejection fraction, history of myocardial infarction, history of coronary revascularization, chronic renal impairment, no re-flow, and the use of intravascular ultrasound. Hosmer and Lemeshow’s goodness-of-fit test was used to assess the model fit to the data. A P value < .05 was considered statistically significant.
2
Methods
This single-center, retrospective study comprised 605 consecutive patients who underwent primary PCI for an anterior STEMI without cardiogenic shock at our institution from 2003 to 2010. Within this cohort, an IABP device was inserted at the time of revascularization in 105 patients. Patients with stable angina, unstable angina, non-STEMI, non-anterior STEMI, and cardiogenic shock were excluded. All patients provided written informed consent. The study complied with the Declaration of Helsinki for investigation in human beings, and was approved by the local institutional ethics committee. The procedures were performed according to standard clinical guidelines. In all cases, the interventional strategy, as well as the use of adjunctive devices and pharmacotherapy, was at the discretion of the operating interventional cardiologist. All patients received aspirin 325 mg pre-procedure and recommended to continue this regimen indefinitely. In addition, clopidogrel 75 mg daily following a 300-mg or 600-mg loading dose was commenced pre-procedurally and recommended to continue for at least 12 months.
The analyzed clinical end points were the in-hospital rate of cardiac death, vascular complications, and major bleeding. Cardiogenic shock was defined as systolic blood pressure ≤ 90 mmHg for at least 30 min and/or presence of peripheral signs of hypoperfusion, as evidenced by peripheral vasoconstriction or urine output < 30 ml/min or altered sensorium. Hypercholesterolemia was defined as fasting cholesterol > 250 mg/dl or the use of lipid lowering therapy. Hypertension was defined as blood pressure > 140/90 mmHg or the use of anti-hypertensive therapy. Renal impairment was defined as serum creatinine > 1.2 mg/dL. Angiographic success was defined as postprocedural stenosis ≤ 30% and Thrombolysis in Myocardial Infarction Flow Grade 3. Gastrointestinal bleeding was defined as evidence of an upper (coffee ground emesis, endoscopy demonstrating active bleeding) or lower (melena, hematochezia, or endoscopy demonstrating an active bleeding site) gastrointestinal bleed. Major bleeding was defined as any combination of gastrointestinal bleeding, hematocrit drop ≥ 15% and/or a hematoma.
Statistical analysis was performed using SAS version 8.2 (SAS institute, Cary, NC). Continuous variables and categorical variables are expressed as mean ± S.D. and percentages, respectively. Student t test was used to compare continuous variables, and the chi-square test or Fisher’s exact test was used to compare categorical variables. Using propensity scoring, patients in the IABP group ( n = 70) were 1:1 matched with patients in the no IABP group ( n = 70) in order to obtain groups with similar baseline characteristics and to minimize selection bias.
To calculate the propensity score, the following variables were entered into the model: age, sex, hypertension, diabetes mellitus, hypercholesterolemia, current smoker, body mass index, left ventricular ejection fraction, history of myocardial infarction, history of coronary revascularization, chronic renal impairment, no re-flow, and the use of intravascular ultrasound. Hosmer and Lemeshow’s goodness-of-fit test was used to assess the model fit to the data. A P value < .05 was considered statistically significant.
3
Results
Patient baseline characteristics are summarized in Table 1 . The two cohorts were well matched for age, sex, and the conventional risk factors for coronary artery disease. In the IABP cohort, the average systolic and diastolic blood pressures prior to IABP were 104 ± 22.3 and 73 ± 16.3, respectively. The average augmented systolic blood pressure was 126 ± 28.3. Although the left ventricular ejection fraction was significantly lower in the IABP patients (0.32 ± 0.11 vs. 0.39 ± 0.12; P < .001), the two cohorts were well matched for history of MI, coronary revascularization, and chronic renal impairment.
| Variable | IABP ( n = 105) | No IABP ( n = 500) | P value |
|---|---|---|---|
| Age, years | 59.0 ± 12.5 | 60.6 ± 13.4 | .27 |
| Men | 75 (71.4%) | 346 (69.5%) | .69 |
| Hypertension | 77 (73.3%) | 400 (80.2%) | .12 |
| Diabetes | 23 (22.3%) | 135 (27%) | .29 |
| Hypercholesterolemia | 80 (76.2%) | 400 (80%) | .32 |
| Current smoker | 44 (41.9%) | 181 (36.2%) | .27 |
| Body mass index (kg/m 2 ) | 29.7 ± 6.4 | 29.5 ± 6.5 | .79 |
| Left ventricular ejection fraction | 0.32 ± 0.11 | 0.39 ± 0.12 | < .001 |
| History of: | |||
| Myocardial infarction | 13 (12.4%) | 48 (9.6%) | .39 |
| Percutaneous coronary intervention | 16 (15.2%) | 78 (15.6%) | .93 |
| Coronary artery bypass surgery | 0 | 11 (2.2%) | .23 |
| Chronic renal impairment | 8 (7.7%) | 48 (9.6%) | .53 |
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