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A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation
Published on: February 28, 2012
Prophylactic use of an implantable cardioverter-defibrillator after acute myocardial infarction
Stefan H Hohnloser1, Karl Heinz Kuck, Paul Dorian
1Department of Medicine, Division of Cardiology, J.W. Goethe University, Frankfurt, Germany. hohnloser@em.uni-frankfurt.de
Insights
Implantable cardioverter-defibrillators (ICDs) did not reduce overall mortality in high-risk patients soon after myocardial infarction. While ICDs lowered arrhythmia deaths, nonarrhythmic deaths increased, offsetting benefits.
Area of Science:
- Cardiology
- Clinical Trials
- Electrophysiology
Background:
- Implantable cardioverter-defibrillator (ICD) therapy improves survival in high-risk patients prone to ventricular arrhythmias.
- The efficacy of ICDs in patients early after myocardial infarction (MI) was previously unknown.
Purpose of the Study:
- To evaluate the effectiveness of prophylactic ICD therapy in high-risk patients following acute myocardial infarction.
- To determine the impact of ICDs on overall mortality and cause-specific mortality in this patient population.
Main Methods:
- The Defibrillator in Acute Myocardial Infarction Trial was a randomized, open-label study comparing ICD therapy versus no ICD therapy.
- Enrolled patients (6-40 days post-MI) had reduced left ventricular ejection fraction (≤0.35) and impaired cardiac autonomic function.
- Primary outcome was all-cause mortality; secondary outcome was death from arrhythmia.
Main Results:
- No significant difference in overall mortality was observed between the ICD and control groups over a mean follow-up of 30 months.
- ICD therapy significantly reduced deaths due to arrhythmia (12 vs. 29), but increased nonarrhythmic deaths (50 vs. 29).
- The increase in nonarrhythmic deaths offset the benefit of reduced arrhythmia deaths, resulting in no net survival advantage.
Conclusions:
- Prophylactic ICD therapy does not reduce overall mortality in high-risk patients early after myocardial infarction.
- While ICDs effectively decrease deaths from arrhythmias, this benefit is counteracted by an increased risk of nonarrhythmic mortality.
- Current guidelines may need re-evaluation for early post-MI patients with reduced ejection fraction and autonomic dysfunction.
Background:
Implantable cardioverter-defibrillator (ICD) therapy has been shown to improve survival in patients with various heart conditions who are at high risk for ventricular arrhythmias. Whether benefit occurs in patients early after myocardial infarction is unknown.
Methods:
We conducted the Defibrillator in Acute Myocardial Infarction Trial, a randomized, open-label comparison of ICD therapy (in 332 patients) and no ICD therapy (in 342 patients) 6 to 40 days after a myocardial infarction. We enrolled patients who had reduced left ventricular function (left ventricular ejection fraction, 0.35 or less) and impaired cardiac autonomic function (manifested as depressed heart-rate variability or an elevated average 24-hour heart rate on Holter monitoring). The primary outcome was mortality from any cause. Death from arrhythmia was a predefined secondary outcome.
Results:
During a mean (+/-SD) follow-up period of 30+/-13 months, there was no difference in overall mortality between the two treatment groups: of the 120 patients who died, 62 were in the ICD group and 58 in the control group (hazard ratio for death in the ICD group, 1.08; 95 percent confidence interval, 0.76 to 1.55; P=0.66). There were 12 deaths due to arrhythmia in the ICD group, as compared with 29 in the control group (hazard ratio in the ICD group, 0.42; 95 percent confidence interval, 0.22 to 0.83; P=0.009). In contrast, there were 50 deaths from nonarrhythmic causes in the ICD group and 29 in the control group (hazard ratio in the ICD group, 1.75; 95 percent confidence interval, 1.11 to 2.76; P=0.02).
Conclusions:
Prophylactic ICD therapy does not reduce overall mortality in high-risk patients who have recently had a myocardial infarction. Although ICD therapy was associated with a reduction in the rate of death due to arrhythmia, that was offset by an increase in the rate of death from nonarrhythmic causes.
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