Should Survivors of Myocardial Infarction With Low Ejection Fraction Be Routinely Referred to Arrhythmia Specialists?

Abstract

Because survivors of myocardial infarction are at risk for ventricular arrhythmias and sudden death, physicians must decide whether to refer these patients to specialists for arrhythmia assessment and therapy. However, this decision is complex as few randomized data are available concerning either diagnostic or therapeutic options. Therefore, we modeled the potential impact of current arrhythmia detection and management strategies on mortality in survivors of myocardial infarction with reduced left ventricular function who are managed in a contemporary manner. Based on recent data we estimated that the mortality for myocardial infarction survivors with left ventricular ejection fraction less than 0.40 is 20 percent over 3.5 years and that half of the deaths are sudden. The sensitivity and specificity of a Holter electrocardiogram (ECG), a signal-averaged ECG, and an invasive electrophysiology study for predicting sudden death were obtained from a literature review of trials published after 1990 that included more than 300 patients. A series of models were constructed to predict mortality achieved by different arrhythmia management strategies that reduced sudden death by 50 percent and 75 percent--reductions estimated to be within the range for amiodarone and implantable defibrillators. We found that, when routinely applied to all infarct survivors with depressed ventricular function, a therapy that reduces sudden death by 50 percent with 1 percent fatal adverse effects (potentially amiodarone) saves approximately 1 life for every 25 patients treated. Therapy that reduces sudden death by 75 percent with 2 percent fatal adverse effects (potentially implantable defibrillators) saves 1 life for every 14 patients treated. Using Holter ECG recordings, a signal-averaged ECG, or an invasive electrophysiology study to select higher-risk groups, 1 life can be saved for every 4 to 11 patients treated, and the negative impact of adverse effects can be reduced. However, to achieve this benefit, additional and potentially invasive arrhythmia testing must be applied to 28 to 47 patients for each life saved. Thus, with contemporary management of acute myocardial infarction, the risk of sudden death for survivors is sufficiently low that broad application of available antiarrhythmic therapies has limited potential for further improving survival, particularly if therapy also has significant adverse effects. Thus, routine referral to arrhythmia specialists is not warranted for the majority of infarct survivors and should be largely reserved for patients with serious, symptomatic arrhythmias.