Dependency of Exercise‐Induced T‐Wave Alternans Predictive Power for the Occurrence of Ventricular Arrhythmias from Heart Rate

Abstract

Exercise-induced TWA predictive power for the occurrence of ventricular arrhythmias, quantified using both maxTWAA and TWAAratio, was higher at low rather than at high HR.

Heart Rate–Dependent Hysteresis of T‐Wave Alternans in Primary Prevention ICD Patients

“…Still, such HR range was not optimal to discriminate ICD_Cases from ICD_Controls (Table ), that is to identify those ICD patients who developed VT/VF during follow‐up, and thus who were retrospectively identified as at increased risk of major cardiac events. Similarly to what found in our previous studies, the best exercise HR for discriminating the two ICD groups was 80 bpm, in correspondence of which ICD_Cases and ICD_Controls were characterized by low but significantly different TWA levels, with the former showing higher TWA than the latter (Table ). Such HR also represents a common HR at which arrhythmias occur, observation that supports the hypothesis of TWA being an arrhythmogenic phenomenon.…”

“…Microvolt T‐wave alternans (TWA) consists in a subtle every‐other‐beat fluctuation of the electrocardiographic (ECG) T‐wave amplitude at stable heart rate (HR) during sinus rhythm, and is considered a promising noninvasive index to predict the occurrence of malignant ventricular arrhythmias and sudden cardiac death . It has been observed that TWA tends to increase its amplitude with increasing HR so that, even though it has also been observed in resting conditions, TWA analysis is often performed at accelerated HRs reached through exercise . Several studies have shown that exercise‐induced TWA is capable of stratifying risk for cardiovascular death and lethal arrhythmias .…”

“…When evaluated during an exercise testing, TWA is typically measured during the HR‐increasing phase of the test or at fast HRs (100–125 bpm) in correspondence of which it significantly increases its amplitude . Still, any exercise test also includes a recovery phase, characterized by a decreasing HR, during which the patient returns to his/her initial conditions.…”

Overnight T-Wave Alternans in Sleep Apnea Patients

“…Microvolt T-wave alternans (TWA), consisting in a subtle alternation of the electrocardiographic (ECG) T wave, is a promising noninvasive indicator of sudden cardiac death [9]. Although low-levels of TWA have been also observed in resting healthy subjects [10,11,12], TWA is more commonly found in patients affected by cardiovascular diseases [11,13,14,15,16] and its amplitude tends to increase with increasing heart rate (HR) [9,17,18]. As a consequence, since HR decrease during sleep and TWA is more hardly detectable, only few studies have investigated TWA incidence during sleep, especially when SA occurs [7,19].…”

T-wave alternans hysteresis on heart rate

“…It is well-known that TWA depends on HR. Specifically, it has been observed that TWA tends to increase with increasing HR [6][7][8][9] so that, even though it has also been observed in resting conditions [10][11][12][13], TWA analysis is often performed at accelerated HRs reached through exercise [1,[4][5][6][7][8][9]14,15].…”