Effects of Acute Mental Stress and Exercise on T-Wave Alternans in Patients With Implantable Cardioverter Defibrillators and Controls

Abstract

Background-Malignant cardiac arrhythmias can be triggered by exercise and by mental stress in vulnerable patients.Exercise-induced T-wave alternans (TWA) is an established marker of cardiac electrical instability. However, the effects of acute mental stress on TWA have not been investigated as a vulnerability marker in humans. Methods and Results-TWA responses to mental stress (anger recall and mental arithmetic) and bicycle ergometry were evaluated in patients with implantable cardioverter defibrillators (ICDs) and documented coronary artery disease (nϭ23, age 62.1Ϯ12.3 years) and controls (nϭ17, age 54.2Ϯ12.1 years). TWA was assessed from digitized ECGs by modified moving average analysis. Dual-isotope single photon emission computed tomography was used to assess myocardial ischemia. TWA increased during mental stress and exercise (P values Ͻ0.001), and TWA responses were higher in ICD patients than in controls (arithmetic ⌬ϭ8.9Ϯ1.4 versus 4.3Ϯ2.2 V, Pϭ0.043; exercise ⌬ϭ21.4Ϯ2.8 versus 13.8Ϯ3.2 V, Pϭ0.038). TWA increases with mental stress occurred at substantially lower heart rates (anger recall ⌬ϭ9.7Ϯ7.7 bpm, arithmetic ⌬ϭ14.3Ϯ13.3 bpm) versus exercise (⌬ϭ53.7Ϯ22.7 bpm; P values Ͻ0.001). After adjustment for heart rate increases, mental stress and exercise provoked increased TWA in ICD patients (P values Ͻ0.05), but not in controls (P values Ͼ0.2). Ejection fraction and stress-induced myocardial ischemia were not associated with TWA. Conclusions-Mental stress can induce cardiac electrical instability, as assessed via TWA, among patients with arrhythmic vulnerability and occurs at lower heart rates than with exercise. Pathophysiological mechanisms of mental stressinduced arrhythmias may therefore involve central and autonomic nervous system pathways that differ from exercise-induced arrhythmias.

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

“…This is not in disagreement with previous investigations, which also found that dynamics of TWA cannot be completely explained by changes in heart rate in patients with coronary artery disease. 32,33 Consistent with the relatively small changes in heart rate, there was also a small shortening of QT intervals before the onset of VTA (2.5%). Although correction of QT intervals with the use of Bazett's formula resulted in prolongation of QTc-B before the onset, this effect could be due to overestimation of QT intervals at faster heart rates.…”

Phobic Anxiety and Risk of Coronary Heart Disease and Sudden Cardiac Death Among Women

“…20 Potential mechanisms include increases in sympathetic nervous system activity, leading to cardiac instability 21 and an acute increase in susceptibility to ventricular fibrillation and SCD. When we examined the associations between phobic anxiety and risk of CHD over time, only the association with SCD risk appeared to vary by time.…”

Heart Rate Variability, Catecholamine and Hemodynamic Responses During Rest and Stress in Coronary Artery Disease Patients: The PIMI Study

“…Results revealed that SBP levels during metal task and SBP reactivity (increases) were highest for the severely ischemic group and lowest for controls (Krantz et al, 1991). Acute, laboratory-induced anger as part of a mental stress task has also been found to increase the risk of cardiac arrhythmias associated with sudden cardiac death in CAD patients with implantable cardioverter-defibrilators (Kop et al, 2004;Lampert, Jain, Burg, Batsford, & McPherson, 2000).…”