NEW ORLEANS — New results further supported T-wave alternans as a way to identify patients with nonischemic cardiomyopathy who do not need an implantable cardioverter defibrillator.
Findings from a study with 446 patients done in Italy showed that among patients with nonischemic cardiomyopathy and New York Heart Association class II or III heart failure, “patients with a normal TWA [T-wave alternans] test have a very good prognosis and are unlikely to benefit from ICD [implantable cardioverter defibrillator] therapy,” Dr. Gaetano M. De Ferrari said at the annual meeting of the American College of Cardiology.
In contrast, similar patients with an abnormal TWA result had a fourfold increased risk of cardiac death or a life-threatening ventricular arrhythmia during 18–24 months of follow-up, suggesting that these patients are good candidates for an ICD, said Dr. De Ferrari, chief of the cardiac ICU at Hospital San Matteo in Pavia, Italy.
The results from this “methodologically sound, prospective study confirm with high quality what [results from] other studies have shown,” that the predictive value of TWA in patients with nonischemic cardiomyopathy is similar to its predictive value in patients with ischemic cardiomyopathy, said Dr. Theodore Chow, director of electrophysiology research at the Ohio Heart and Vascular Center in Cincinnati. The new findings, in combination with prior results from other studies, “provide a rationale for a careful, prospective evaluation of whether ICD implants are useful in nonischemic patients with normal TWA.”
Until such a trial is done, “I think that most cardiologists will still generally favor placing ICDs based on data from” the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), which showed that ICDs significantly cut mortality in all patients with a left ventricular ejection fraction of 35% or less, said Dr. Chow in an interview.
“We need strategies to sort out who gets an ICD. It's not clear why the use of ICDs is so low, but it's hard to picture that it will be solved by having TWA measurement in all patients,” commented Dr. Mariell L. Jessup, professor of medicine and medical director of heart failure and cardiac transplantation at the University of Pennsylvania, Philadelphia.
The T-Wave Alternans in Patients with Heart Failure (ALPHA) study was done at nine centers in Italy, and was funded in part by Boston Scientific, a company that markets an ICD but does not market equipment used for assessing TWA. The equipment used to measure TWA in the ALPHA study was made by Cambridge Heart.
Dr. De Ferrari and his associates screened more than 3,500 patients with heart failure to identify 446 with nonischemic, dilated cardiomyopathy, a left ventricular ejection fraction of 40% or less, New York Heart Association class II or III heart failure, and no other indication for receiving an ICD. TWA testing identified 154 patients with normal readings and 292 patients with an abnormal result.
During follow-up, the incidence of the study's primary end point—cardiac death or development of a life-threatening ventricular arrhythmia—was 10% in the patients with an abnormal TWA and 3% in those with a normal TWA, a statistically significant difference. When adjusted for baseline differences in age, gender, New York Heart Association class, and left ventricular ejection fraction, patients with an abnormal TWA reading at baseline were 3.2-fold more likely to develop the primary end point than were those with a normal TWA result.
“The most important finding” was the negative predictive value of a normal TWA result at baseline, said Dr. De Ferrari. During 18 months of follow-up, 97% of patients with a normal TWA result were free from the primary end point. “Patients with a normal TWA had a very good prognosis and were unlikely to benefit from an ICD,” he said.
Dr. De Ferrari agreed with the opinion voiced by Dr. Chow: The way to prove that TWA can identify patients who do not need an ICD is to randomize patients with a normal TWA result to either receive an ICD or not and then compare the outcomes of patients in these two groups.
'Patients with a normal TWA test have a very good prognosis and are unlikely to benefit from ICD therapy.' DR. DE FERRARI