Cardiovascular diseases, including ventricular arrhythmias are responsible for increased mortality in patients with acromegaly. Acromegaly may cause repolarization abnormalities such as QT prolongation and impairment of repolarization reserve enhancing liability to arrhythmia. The aim of this study was to determine the short-term beat-to-beat QT variability in patients with acromegaly. Thirty acromegalic patients (23 women and 7 men, mean age±SD: 55.7±10.4 years) were compared with age- and sex-matched volunteers (mean age 51.3±7.6 years). Cardiac repolarization parameters including frequency corrected QT interval, PQ and QRS intervals, duration of terminal part of T waves (Tpeak-Tend) and short-term variability of QT interval were evaluated. All acromegalic patients and controls underwent transthoracic echocardiographic examination. Autonomic function was assessed by means of five standard cardiovascular reflex tests. Comparison of the two groups revealed no significant differences in the conventional ECG parameters of repolarization (QT: 401.1±30.6 ms vs 389.3±16.5 ms, corrected QT interval: 430.1±18.6 ms vs 425.6±17.3 ms, QT dispersion: 38.2±13.2 ms vs 36.6±10.2 ms; acromegaly vs control, respectively). However, short-term beat-to-beat QT variability was significantly increased in acromegalic patients (4.23±1.03 ms vs 3.02±0.80, P<0.0001). There were significant differences between the two groups in the echocardiographic dimensions (left ventricular end diastolic diameter: 52.6±5.4 mm vs 48.0±3.9 mm, left ventricular end systolic diameter: 32.3±5.2 mm vs 29.1±4.4 mm, interventricular septum: 11.1±2.2 mm vs 8.8±0.7 mm, posterior wall of left ventricle: 10.8±1.4 mm vs 8.9±0.7 mm, P<0.05, respectively). Short-term beat-to-beat QT variability was elevated in patients with acromegaly in spite of unchanged conventional parameters of ventricular repolarization. This enhanced temporal QT variability may be an early indicator of increased liability to arrhythmia.

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Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Office Introduction Polycystic ovary syndrome (PCOS) is a multifactorial, endocrine disease associated with metabolic disturbances (e.g. hyperinsulinemia, insulin resistance) and increased cardiovascular risk. Recent data strongly suggest that different QT variability parameters characterizing cardiac repolarization instability represent novel markers in proarrhythmic risk assessment. Purpose In the present study we investigated ECG repolarization parameters, including QT variability parameters in patients with polycystic ovary syndrome. Methods Fifty-five PCOS patients (age: 29±6 years) and 55 age-matched healthy volunteers (age: 29±10 years) were enrolled in the study. Five-minute 12-lead resting electrocardiograms were recorded, the ECGs were digitized and evaluated off-line using the Cardiosys-A01 system (Cardiosys-A01). The following parameters were determined: the frequency corrected QT interval (QTc) using Bazett’s, Fridericia, Framingham and the Hodges formulas; QT dispersion (QTd) and T wave peak-to-end distance (Tpeak-Tend). Among QT variability parameters we analyzed the QT variance (QTv), the QT variability index (QTVI), the short-term beat-to-beat QT and RR interval variability (STV-QT, STV-RR) based on constructed Poincaré plots and the variability ratio (VR). Results The RR interval did not differ significantly in PCOS patients compared to controls (821±129 ms vs. 847±99 ms), however the QT interval (373±30 ms vs. 391±27 ms, p&lt;0.01), the QTc calculated with Bazett’s, Framingham, Fridericia and Hodges correction formulas (QTc Bazett’s: 413±18 ms vs. 426±21 ms, p&lt;0.01) and the Tpeak-Tend intervals were significantly shorter (76±10 ms vs. 83±12 ms, p&lt;0.01). The QTd, QTv, and STV-RR did not differ significantly. However, the VR (0.3±0.4 vs. 0.2±0.2, p&lt;0.05), the QTVI (-0,9±0.5 vs. -1,3±0.4, p&lt;0.001), and importantly, the STV-QT were significantly higher in PCOS patients compared to controls (4.0±0.9 ms vs. 3.2±0.9 ms, p&lt;0.0001). Conclusion Some of the alterations in repolarization parameters and the significant increase in the short-term beat-to-beat QT interval variability and the QT variability index may indicate increased repolarization instability in patients with polycystic ovary syndrome compared to age-matched controls, however, further studies are needed to establish the exact relation of this finding to increased arrhythmia propensity in this population.

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Office Introduction Polycystic ovary syndrome (PCOS) is a multifactorial, endocrine disease associated with metabolic disturbances (e.g. hyperinsulinemia, insulin resistance) and increased cardiovascular risk. Recent data strongly suggest that different QT variability parameters characterizing cardiac repolarization instability represent novel markers in proarrhythmic risk assessment. Purpose In the present study we investigated ECG repolarization parameters, including QT variability parameters in patients with polycystic ovary syndrome. Methods Fifty-five PCOS patients (age: 29±6 years) and 55 age-matched healthy volunteers (age: 29±10 years) were enrolled in the study. Five-minute 12-lead resting electrocardiograms were recorded, the ECGs were digitized and evaluated off-line using the Cardiosys-A01 system (Cardiosys-A01, MDE Heidelberg GMBH, Heidelberg, Germany). The following parameters were determined: the frequency corrected QT interval (QTc) using Bazett’s, Fridericia, Framingham and the Hodges formulas; QT dispersion (QTd) and T wave peak-to-end distance (Tpeak-Tend). Among QT variability parameters we analyzed the QT variance (QTv), the QT variability index (QTVI), the short-term beat-to-beat QT and RR interval variability (STV-QT, STV-RR) based on constructed Poincaré plots and the variability ratio (VR). Results The RR interval did not differ significantly in PCOS patients compared to controls (821±129 ms vs. 847±99 ms), however the QT interval (373±30 ms vs. 391±27 ms, p&lt;0.01), the QTc calculated with Bazett’s, Framingham, Fridericia and Hodges correction formulas (QTc Bazett’s: 413±18 ms vs. 426±21 ms, p&lt;0.01) and the Tpeak-Tend intervals were significantly shorter (76±10 ms vs. 83±12 ms, p&lt;0.01). The QTd, QTv, and STV-RR did not differ significantly. However, the VR (0.3±0.4 vs. 0.2±0.2, p&lt;0.05), the QTVI (-0,9±0.5 vs. -1,3±0.4, p&lt;0.001), and importantly, the STV-QT were significantly higher in PCOS patients compared to controls (4.0±0.9 ms vs. 3.2±0.9 ms, p&lt;0.0001). Conclusion Some of the alterations in repolarization parameters and the significant increase in the short-term beat-to-beat QT interval variability and the QT variability index may indicate increased repolarization instability in patients with polycystic ovary syndrome compared to age-matched controls, however, further studies are needed to establish the exact relation of this finding to increased arrhythmia propensity in this population.

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