Key result
Short QT syndrome patients exhibited a significantly reduced adaptation of the QT interval to heart rate during exercise compared with controls (slope -0.53 vs -1.29 ms/beat/min; P<0.0001).
Why the study?
Does exercise testing help differentiate patients with short QT syndrome from healthy controls based on QT interval adaptation to heart rate?
Case-Control (n=41)
Does exercise testing help differentiate patients with short QT syndrome from healthy controls based on QT interval adaptation to heart rate?
Absolute Event Rate: -0.53% vs -1.29%
p-value: p=<0.0001
Exercise testing reveals a reduced adaptation of the QT interval to heart rate in short QT syndrome patients, providing a useful diagnostic tool.
Exercise testing may aid short QT syndrome differentiation; leaves open prospective validation before clinical use.
AIMS: Short QT syndrome (SQTS) is a rare arrhythmogenic inherited heart disease. Diagnosis can be challenging in subjects with slightly shortened QT interval at electrocardiogram. In this study we compared the QT interval behaviour during exercise in a cohort of SQTS patients with a control group, to evaluate the usefulness of exercise test in the diagnosis of SQTS. METHODS AND RESULTS: Twenty-one SQTS patients and 20 matched control subjects underwent an exercise test. QT interval was measured at different heart rates (HRs), at rest and during effort. The relation between QT interval and HR was evaluated by linear regression analysis according to the formula: QT = β ×HR + α, where β is the slope of the linear relation, and α is the intercept. Rest and peak exercise HRs were not different in the two groups. Short QT syndrome patients showed lower QT intervals as compared with controls both at rest (276 ± 27 ms vs. 364 ± 25 ms, P < 0.0001) and at peak exercise (228 ± 27 ms vs. 245 ± 26 ms, P = 0.05), with a mean variation from rest to peak effort of 48 ± 14 ms vs. 120 ± 20 ms (P < 0.0001). Regression analysis of QT/HR relationship revealed a less steep slope for SQTS patients compared with the control group, never exceeding the value of -0.90 ms/beat/min (mean value -0.53 ± 0.15 ms/beat/min vs. -1.29 ± 0.30 ms/beat/min, P < 0.0001). CONCLUSION: Short QT syndrome patients show a reduced adaptation of the QT interval to HR. Exercise test can be a useful tool in the diagnosis of SQTS.
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Giustetto et al. (2015) conducted a case-control in Short QT syndrome (n=41). Short QT syndrome vs. Matched controls was evaluated on Slope of QT/HR relationship during exercise (p=<0.0001). Short QT syndrome patients exhibited a significantly reduced adaptation of the QT interval to heart rate during exercise compared with controls (slope -0.53 vs -1.29 ms/beat/min; P<0.0001).
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