To evaluate whether T Wave Alternans can predict ventricular arrhythmias and sudden cardiac
death (SCD) in a prospective epidemiologic natural history study.
The prospective epidemiologic pilot study included 550 patients that had left ventricular
dysfunction and no history of sustained ventricular arrhythmias. The primary hypothesis
tested was whether there was an increased risk of having an arrhythmic event when T Wave
Alternans was present in the patient. The secondary aims included comparing risk due to T
Wave Alternans between the ischemic patients and non-ischemic patients and assessing whether
T Wave Alternans remained an independent predictor of risk upon adjustment for other known
risk factors for arrhythmic events such as ejection fraction, ventricular ectopy, NSVT,
average NN interval, and RR interval variability.
The study approach was a standard epidemiologic surveillance technique. The subject
population consisted of individuals with Class I to III heart failure who will underwent a
TWA and Holter monitor test and then were followed for up to two years or until arrhythmic
Sudden cardiac death accounts for approximately 400,000 deaths each year in the United
States and remains a health problem of epidemic proportions. Most sudden cardiac deaths are
caused by fatal ventricular arrhythmias. An effort aimed at the primary prevention of sudden
cardiac death requires efficient identification of patients who are at high enough risk for
having these arrhythmias to warrant aggressive prophylactic therapy. A number of recently
completed, randomized clinical trials have demonstrated that an implantable cardiac
defibrillator (ICD) can prevent sudden cardiac death in a highly selected group of high-risk
patients. When these trials are viewed together, the only patients in whom the prophylactic
implantation of an ICD has proven benefit are those patients identified by documented,
spontaneous or inducible, sustained ventricular arrhythmias.
Two randomized treatment trials (MADIT II, SCD-HEFT) tested the hypothesis that implantation
of an ICD would reduce mortality in patients with congestive heart failure (CHF) and left
ventricular dysfunction without any further risk tratification. However, the implications of
these two trials-implantation of an ICD in every patient with CHF-were unlikely to be
accepted either by the medical community or by health care payers. More efficient methods of
risk stratification were necessary to identify those patients with CHF who were most likely
to benefit from prophylactic treatment with an ICD.
T Wave Alternans is a subtle every-other-beat variation in electrocardiographic T waves that
is prognostic of patients at high risk for life-threatening cardiac arrhythmias and sudden
cardiac death. It has recently been shown that T Wave Alternans (TWA) measured during
exercise is strongly associated with inducible monomorphic CVT and with subsequent
spontaneous arrhythmic events. This preliminary data suggest that TWA may be an efficient
and non-invasive surrogate for electrophysiologic testing to screen patients who may be at
high-risk for sudden cardiac death.
1. Patients with left ventricular dusfunction
2. Patients with non-ischemic cardiomyopathy
1. Patients not at high risk for sudden cardiac death (SCD)