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

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.

Comparing the variants of takotsubo syndrome: an observational study of the ECG and structural changes from a New Zealand tertiary hospital.

OBJECTIVES: In takotsubo syndrome, QTc prolongation is a measure of risk of potentially fatal arrhythmia. It is not known how this risk, or derangement of other markers, differs across the echo variants of takotsubo syndrome. Therefore, we sought to explore whether apical takotsubo syndrome differs from the variants of the syndrome in more ways than just regional wall motion pattern. As the region of affected myocardium is usually larger, we hypothesised that patients with the classic apical ballooning form of takotsubo syndrome would have more severe derangement of their markers. DESIGN: Observational study of patients gathered from a prospective database (2010-2018) and by retrospective review (2006-2009). SETTING: The sole tertiary hospital from a New Zealand region in which case clusters of takotsubo syndrome were precipitated by large earthquakes in 2010, 2011 and 2016. PARTICIPANTS: A total of 222 patients who met a modified version of the Mayo criteria for takotsubo syndrome were included. All patients had digitally archived echocardiograms that were over-read by a second echocardiologist blinded to the clinical report. PRIMARY OUTCOME MEASURES: Ejection fraction, peak troponin and QTc interval. RESULTS: Patients with the apical form were older (p=0.011), had a lower initial left ventricular ejection fraction (35% vs 44%, p<0.0001) and a higher peak high-sensitivity troponin I (hsTnI) (p=0.01) than those with variant forms. There was no difference in the electrical abnormalities between the variants (QTc interval, heart rate, PR interval, QRS duration or T-wave axis). There was also no correlation between any of peak hsTnI, peak QTc and ejection fraction. QTc interval increased on day 2 and peaked on day 3 before falling steeply (p<0.0001). CONCLUSIONS: The variants of takotsubo syndrome differ in more ways than just their echo pattern but do not differ in their electrical abnormalities. There is a dissociation between the structural and electrical abnormalities. QTc peaks on day 3 and then falls steeply.

Comparison of retinal nerve fiber layer and central macular thickness measurements among five different optical coherence tomography instruments in patients with multiple sclerosis and optic neuritis.

BACKGROUND: To compare the mean central macular thickness (CMT) and the mean average optic nerve retinal nerve fiber layer (RNFL) thickness in the eyes of patients with a history of optic neuritis and/or multiple sclerosis (MS) using 5 commercially available optical coherence tomography (OCT) instruments. METHODS: Cross-sectional study including 46 patients (92 eyes) with a history of optic neuritis and/or MS. Both eyes were imaged on the same day with 5 OCT instruments: 1 time-domain OCT (Stratus) and 4 different Fourier-domain (spectral-domain) OCT (3D OCT-1000, Cirrus, RTVue-100, and Spectralis). RESULTS: Twenty-five patients (50 eyes) were included in the final analysis after excluding patients with diabetes, glaucoma, ocular hypertension, or retinal pathology and inadequate scan quality. Randomized block analysis of variance revealed statistically significant differences across instruments (P < 0.001) for both eyes for mean CMT and mean average optic nerve RNFL. When testing for significant differences in measurements from instrument to instrument, some difference was noted between the right and left eyes. CONCLUSIONS: Statistically significant differences exist among commercially available OCT instruments in measuring mean CMT and mean average RNFL thickness in patients with optic neuritis and/or MS. These findings likely result from the differences in data acquisition and segmentation algorithm software among OCT instruments. Awareness of these variations among OCT instruments will be important in using these instruments for clinical trials and management of patients with optic neuritis and/or MS.