Sudden death after myocardial infarction

Cardiology Review® Online, April 2006, Volume 23, Issue 4

Strategic Alliance Partnership | <b>Lowe Syndrome Association</b>

Anderson and Solomon (page 17) elegantly elucidate the patterns of sudden death after myocardial infarction (MI) in their analysis of the Valsartan in Acute Myocardial Infarction Trial (VALIANT) database.

Anderson and Solomon elegantly elucidate the patterns of sudden death after myocardial infarction (MI) in their analysis of the Valsartan in Acute Myocardial Infarction Trial (VALIANT) database. They show convincingly that sudden death remains a problem and that risk stratification fails to adequately identify patients for implantable cardioverter defibrillator (ICD) therapy, which presumably would have been life-saving in the majority of patients had they received it.

Current guidelines and Medicare rules (which are very different concepts, as discussed later) suggest that ICD therapy is appropriate for primary prevention in MI survivors with an ejection fraction below 30% at least 1 month after MI (or 3 months after coronary artery bypass graft surgery). The present study, however, suggests that half of all sudden deaths observed in patients with left ventricular dysfunction followed-up for 2 years would have already occurred by 1 month if the guidelines were followed. Furthermore, low ejection fraction only identified half of all sudden deaths. Although a low ejection fraction consistently places patients at significantly increased risk, there are actually more patients with higher ejection fractions, so although their risk is lower, the greater numbers mean that selection by ejection fraction is unlikely to identify more than half of all patients after MI or those who will die suddenly. Risk markers, such as increased age and widened QRS complex (< 120 ms), among others, also result in less-than-stellar accuracy. T-wave alternans seems to have an excellent negative predictive value and a fair positive predictive value, but has not been studied early after MI.1 Putting defibrillators in a larger number of patients with an ejection fraction below 30% would be a start, but to tackle the risk in patients with an ejection fraction above 30% would result in tremendous costs, with a higher number of patients being treated and a larger proportion never receiving a shock. What we really need is a good risk stratification tool with excellent sensitivity and specificity because sudden death is a dire outcome and ICD therapy is expensive, with potentially significant complications.

More distressing than our mediocre risk stratification process is the fact that the Centers for Medicare & Medicaid Services (CMS) has overridden specialty consensus guidelines to come up with its own determination of which patients require an ICD. The criterion of a widened QRS complex, which was once a necessity, has been abolished even though no evidence ever supported it. CMS issued a proposed decision memo in December 2005 announcing its intention to accept T-wave alternans testing for its beneficiaries.2 Such a decision would provide a broader evidence base, but clinicians who implant an ICD in a patient older than 65 years in violation of Medi&shy;care guidelines may face criminal prosecution or fines for Medicare fraud. Thus, Anderson and Solomon’s findings that half of sudden deaths occur within 30 days of MI cannot readily be incorporated into practice. On a positive note, the authors did find a favorable effect of beta-blocking agents on sudden death; thus, it is reassuring to recognize that what used to work probably still does.

The take-home message is that revascularization and evidence-based drug therapy are not enough to eliminate the risk of sudden death. We must remain vigilant and apply beta-blocking agents widely, use ICD therapy as often as our database permits, and recognize that our ability to identify patients who will (and will not) benefit from ICD therapy needs much improvement.