NEW ELECTROCARDIOGRAPHIC PREDICTORS OF SUDDEN CARDIAC DEATH
Michael E. Cain, M.D., University at Buffalo, Buffalo, NY, USA
Each year, sudden cardiac death (SCD) claims the lives of 180,000 to 450,000 Americans. During the past 20 years, strategies for prevention of SCD have focused on a subset of patients with coronary artery disease and have relied on the predictive power of low left ventricular ejection fractions (less than 35%) to determine candidacy for an implantable cardioverter defibrillator (ICD). While this subset of patients is at highest risk for SCD, most patients who die suddenly have more preserved ventricular function or have SCD as the first manifestation of heart disease; and currently are not candidates for primary prevention therapy with an ICD. Accordingly, risk stratification must be more inclusive. Effective, inexpensive, noninvasive, and widely available approaches are needed. Data from the Atherosclerosis Risk in Communities and from the Cardiovascular Health Studies recently reported by Waks and co-workers are noteworthy. The authors calculated five measures (sum absolute QRST integral, spatial QRST angle, spatial ventricular gradient [SVG] magnitude, SVG elevation, and SVG azimuth) of global electric heterogeneity (GEH) from the standard 12-lead ECG obtained in each of 20,177 patients representative of the general population (age range 44-100 yrs, 56% female, 77% white) to see how well GEH identified patients who suffered SCD during a mean follow-up of 14 yrs. After multivariable adjustment, baseline GEH measures and large increases in GEH parameters over time were each independently associated with SCD. When GEH data were added to standard clinical/demographic factors (age, sex, race, diabetes, hypertension, coronary heart disease, and stroke), risk prediction improved significantly. Data from a large set of patients who are representative of the general population demonstrate that measures of GEH are independently associated with SCD. These results set the stage for interventional trials aimed at preventing SCD in a broader set of patients at risk for dying suddenly.