Sudden Cardiac Death Early After Myocardial Infarction

Abstract

The issue of SCD primary prevention early after MI remains unresolved. The focus is now firmly centered on the elucidation of risk stratification tests that effectively select patients at high risk of SCD who benefit from early ICD implantation. Zaman and Kovoor Primary Prevention of SCD Early After MI 2429A summary of major risk stratification tests currently used to identify patients at high risk of SCD is given in Table 2. LV DysfunctionImpaired LVEF, one of the most powerful predictors of survival, 64 has been shown to identify patients who derive a mortality benefit from an ICD when implanted predominantly in the remote period after MI. 16,65 However, there are major concerns with the use of LVEF alone as a risk stratifier to guide ICD implantation. One such concern is the low specificity of LVEF for selecting patients who experience arrhythmic versus nonarrhythmic death. In the MADIT II trial, the use of LVEF ≤30% alone to stratify patients for an ICD resulted in relatively small absolute improvement in mortality with low therapeutic efficiency (15-17 defibrillators per life saved). 66 Another concern is the sensitivity of LVEF, given that a large proportion of SCDs still occur in patients with preserved LV function. VALIANT demonstrated that, although the risk of SCD is greatest in patients with severe dysfunction (LVEF ≤30%), almost half of all sudden deaths occur in patients with a higher ejection fraction (LVEF, 31%-40%). 5 The use of LVEF as a risk stratification tool has been tested in the early post-MI stage in the DINAMIT and IRIS trials, which selected patients with LVEF ≤35% and ≤40%, respectively, and failed to show a benefit of early ICD implantation. 12,17 The major limitation with the use of an early LVEF cutoff is the phenomenon of myocardial stunning with variable and unpredictable recovery of LV function after MI. This is especially relevant in the contemporary era of primary PCI for STEMI. Of STEMI patients with LVEF ≤40% at day 3, 24% will improve to have an LVEF >40% at 6 months with a mean 6% relative improvement. 67 Hence, although LV function will invariably be incorporated into risk stratification models for the prevention of SCD, it is clear that other tests are required to adequately select high-risk patients early after MI. RV DysfunctionAlthough impaired LV function has been studied extensively as a predictor of mortality and arrhythmic death, RV dysfunction has been largely overlooked. We know from the VALIANT study that almost 50% of arrhythmic deaths occur in patients with a preserved LVEF.5 RV involvement in inferior MI has been shown to be a predictor of morbidity and mortality, with a higher rate of serious arrhythmias in patients with inferior MI and RV dysfunction. 68,69 In addition, RV dysfunction has been correlated with increased inducibility of VT at EPS. 70 Although there is no current evidence to support the role of early RV assessment to guide ICD implantation, these findings highlight the inadequacy of LVEF alone as a risk stratification tool for the prevention...

Update to Practice Standards for Electrocardiographic Monitoring in Hospital Settings: A Scientific Statement From the American Heart Association

“…101,102 Although the rate of sudden cardiac death (SCD) has decreased with advanced reperfusion and medical and secondary prevention therapies, it still accounts for 24% to 40% of total mortality after MI, 101,103 with an overall incidence of 2% to 4% per year. 104 The highest absolute rates of SCD occur within the early hours after MI and during the initial hospitalization, a relatively brief period that accounts for 17% of the sudden deaths likely to occur within the first 30 days after infarction.…”

Cardiovascular Magnetic Resonance in Acute ST-Segment–Elevation Myocardial Infarction

“…99 However, mortality within the first 30 days post-MI has been shown to be the highest 100 but is predominantly believed to be due to MI or myocardial rupture. 101 Despite that, a quarter of those deaths are still due to ventricular arrhythmias 101 and currently there is no established tool to risk stratify these patients in the acute phase of an MI.…”

Thyroid Function and Sudden Cardiac Death

“…8 As much as 75% of SCDs have been attributed to CHD (known or unknown), and the risk factors for CHD and SCD are therefore very similar and include older age, male sex, hypertension, HF, smoking, and dyslipidemia. 7,9,10 Additional risk factors include nonischemic cardiac disease (eg, congenital heart disease) and noncardiac disorders (eg, drug-induced). 10 However, the predictability of SCD in the general population remains poor, because almost half of the SCD cases are the first presentation of cardiac disease.…”