Clinical assessment of the risk for sudden cardiac death in patients with sickle cell anemia.

BACKGROUND: Previous studies suggest that patients with sickle cell anemia (SCA) have an increased risk of sudden cardiac death; however, its etiology and mechanism are not well defined. Left ventricular hypertrophy (LVH), ventricular tachycardia (VT) and poor left ventricular systolic function are known risk factors for sudden cardiac death. An abnormal microvolt T-wave alternans (TWA) test is also a predictor of sudden cardiac death risk, but it has not been applied to this patient population.
METHODS: We performed a 12-lead electrocardiogram, 24-hour Holter monitor, two-dimensional echocardiogram, nuclear stress test and microvolt TWA test to determine whether markers of sudden cardiac death could be identified.
RESULTS: Twenty-six patients were evaluated with a mean age of 40 +/- 12 years. The two-dimensional echocardiogram revealed a normal ejection fraction in 23 patients and LVH in 17 (65%), whereas hypertension was noted in only five (19%). Microvolt TWA testing was abnormal in six of 22 patients (27%). Holter monitor revealed VT in two patients. Among the clinical variables tested, only LVH was predictive of an abnormal TWA test. The sensitivity, specificity, positive and negative predictive value of LVH for and abnormal TWA test was 100, 56, 46 and 100%.
CONCLUSION: LVH was common in patients with SCA and disproportional to the number of patients with hypertension. Microvolt TWA tests were abnormal in 27% of patients; however, LVH was the only clinical variable that predicted an abnormal TWA test. Risk stratification of SCA patients may require echocardiographic detection of LVH and an abnormal TWA test due to the high negative predictive value. The significance of an abnormal TWA test should be further evaluated in a large study, with a longer follow-up period.