A randomised cross-over trial of QT response to hyperventilation-induced anxiety and diaphragmatic breathing in patients with stress cardiomyopathy and in control patients

The most perfect example of the mind-body interaction in all of medicine is provided by stress cardiomyopathy. In stress cardiomyopathy, what is initially a purely emotional event may become rapidly fatal. Prolongation of the QT interval is a cardinal feature of the condition, but the mechanism of the prolongation is unknown. We undertook a randomised controlled trial of stress with a cross-over design, comparing the cardiac response of women with a history of stress cardiomyopathy to age-matched controls to explore the mind-body interaction. Our hypothesis is that the hearts of women with a history of stress cardiomyopathy will respond differently to emotional stress than those of the controls. This is a randomised cross-over study. Each patient underwent two separate 24-hour Holter monitors performed at least 5 days apart. Baseline recording was followed by either the stress intervention (hyperventilation) or control (diaphragmatic breathing). Our primary endpoint is change in QTc interval over the first hour. Secondary endpoints were change in QTc over 24 hours, and change in SDNN, a measure of heart rate variability. As a secondary stressor, each participant was telephoned four times during their stressed recording and asked to complete a questionnaire. Twelve stress cardiomyopathy patients and twelve control patients were recruited. Baseline characteristics did not differ between cases and controls. With hyperventilation, there was a significant initial difference in anxiety (p