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Randomized Controlled Trial
. 2022 Mar 23;17(3):e0265607.
doi: 10.1371/journal.pone.0265607. eCollection 2022.

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

George M Watson  1 , Jacalin Sutherland  1 , Cameron Lacey  2 , Paul G Bridgman  1
Affiliations
Randomized Controlled Trial

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

George M Watson et al. PLoS One. .

Abstract

Objectives: 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.

Method: 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.

Results: 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<0.001), heart rate response (p<0.0001), and QTc (p<0.0002) compared to diaphragmatic breathing, but no differences between the cases and controls. Only first phone call caused an increase in QTc in cases and controls (p = 0.0098). SDNN increased with hyperventilation (p<0.0001) but did not differ between cases and controls.

Conclusions: QTc response in women with a history of stress cardiomyopathy does not differ from controls. The relevance of QT prolongation and sensitivity in the autonomic response to the pathogenesis of stress cardiomyopathy remains uncertain.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. CONSORT flowchart showing number of patients recruited, assigned to each intervention, and analysed.
Fig 2
Fig 2. The effects of hyperventilation versus diaphragmatic breathing on subjective anxiety in cases and controls, as measured by a five-point Likert scale.
Fig 3
Fig 3. The effects of hyperventilation versus diaphragmatic breathing on the heart rate of all participants in the first 60 minutes.
Fig 4
Fig 4. The effects of hyperventilation versus diaphragmatic breathing on the QTc of all participants in the first 60 minutes.
Fig 5
Fig 5. The effects of hyperventilation on the QTc of cases versus controls in the first 60 minutes.
Fig 6
Fig 6. The effects of an unheralded phone call on QTc in cases and controls.
Fig 7
Fig 7. The effects of hyperventilation on SDNN in cases and controls.
See this image and copyright information in PMC

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