Explaining the clinical manifestations of T wave alternans in patients at risk for sudden cardiac death

摘要

The mechanisms underlying sudden cardiac death (SCD) are complex and diverse. Therefore, correct application of any marker to risk stratify patients for appropriate therapy requires knowledge regarding how the marker is reflective of a particular electro-anatomical substrate for arrhythmias. Non-invasive measurement of beat-to-beat alternation of the electrocardiographic T-wave, referred to as T-wave alternans (TWA), is an important marker of risk for sudden cardiac death (SCD). Is this relationship a mere association or is TWA mechanistically linked to SCD? Recent experimental evidence strongly supports a mechanistic relationship between TWA and SCD. This review will consider the underlying mechanisms of TWA derived from experimental studies, as they relate to clinical observations of TWA in humans, addressing the following questions derived from common clinical observations: 1) Where does TWA on the surface ECG come from? 2) Why is controlled heart rate elevation required to elicit TWA? 3) Why is TWA associated with risk for SCD? 4) Why is TWA associated with a broad range of ventricular arrhythmias? and 5) How do commonly used medications affect TWA?