T wave alternans

T-wave alternans and prolonged QT interval in a male patient found to be in a narrow-complex tachycardia and ruled in for an acute myocardial infarction. Administered Ibutilide and converted to sinus rhythm but subsequently had an episode of Torsades de Pointes which required DC cardioversion back into sinus rhythm.

In cardiology, T wave alternans (TWA) is a periodic beat-to-beat variation in the amplitude or shape of the T wave in an electrocardiogram (ECG or EKG). TWA was first described in 1908. At that time, only large variations ("macroscopic" TWA) could be detected. Those large TWAs were associated with increased susceptibility to lethal ventricular tachycardias.

Most modern references to TWA refer to microvolt T wave alternans (MTWA), a non-invasive heart test that can identify patients who are at increased risk of sudden cardiac death.[1][2] It is most often used in patients who have had myocardial infarctions (heart attacks) or other heart damage to see if they are at high risk of developing a potentially lethal cardiac arrhythmia. Those who are found to be at high risk would therefore benefit from the placement of a defibrillator device which can stop an arrhythmia and save the patient's life.

The TWA test uses an ECG measurement of the heart's electrical conduction using electrodes attached to one's torso. It takes approximately a half-hour to perform on an outpatient basis. The test looks for the presence of repolarization alternans (T-wave alternans), which is variation in the vector and amplitude of the T wave component of the EKG. The amount of variation is small, on the order of microvolts, so sensitive digital signal processing techniques are required to detect TWA. See also wikidoc article on TWA.

  1. ^ Chow T, Saghir S, Bartone C, Goebel M, Schneider J, Booth T, Chan PS (August 2007). "Usefulness of microvolt T-wave alternans on predicting outcome in patients with ischemic cardiomyopathy with and without defibrillators". Am J Cardiol. 100 (4): 598–604. doi:10.1016/j.amjcard.2007.03.069. PMID 17697813.
  2. ^ Bloomfield DM, Bigger JT, Steinman RC, Namerow PB, Parides MK, Curtis AB, Kaufman ES, Davidenko JM, Shinn TS, Fontaine JM (January 2006). "Microvolt T-wave alternans and the risk of death or sustained ventricular arrhythmias in patients with left ventricular dysfunction". J Am Coll Cardiol. 47 (2): 456–63. doi:10.1016/j.jacc.2005.11.026. PMID 16412877.