Increased Short-Term Beat-To-Beat Variability of QT Interval in Patients with Acromegaly
Andrea Orosz1, Éva Csajbók2, Csilla Czékus2
1Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.
Insights
Patients with acromegaly show increased short-term beat-to-beat QT variability, an early indicator of arrhythmia risk. This occurs despite normal conventional repolarization parameters, highlighting a subtle cardiac electrical abnormality in acromegaly.
Area of Science:
- Cardiology
- Endocrinology
- Clinical Electrophysiology
Background:
- Acromegaly, a condition of excess growth hormone, is linked to increased cardiovascular mortality, particularly from ventricular arrhythmias.
- Acromegaly can impair cardiac repolarization, potentially increasing arrhythmia susceptibility through mechanisms like QT prolongation.
Purpose of the Study:
- To investigate short-term, beat-to-beat QT interval variability in patients diagnosed with acromegaly.
- To compare QT variability and conventional repolarization parameters between acromegalic patients and a matched control group.
Main Methods:
- Evaluated 30 acromegalic patients and 30 age/sex-matched controls.
- Assessed cardiac repolarization using standard ECG parameters (QTc, QT dispersion) and short-term beat-to-beat QT variability.
- Performed transthoracic echocardiography and autonomic function tests.
Main Results:
- No significant differences were found in conventional ECG repolarization parameters (QTc, QT dispersion) between groups.
- Acromegalic patients exhibited significantly increased short-term beat-to-beat QT variability compared to controls (P<0.0001).
- Echocardiography revealed significant differences in left ventricular dimensions and wall thickness in acromegalic patients.
Conclusions:
- Elevated short-term beat-to-beat QT variability in acromegaly patients suggests an increased liability to arrhythmias.
- This enhanced temporal QT variability may serve as an early marker for cardiac risk in acromegaly, independent of conventional repolarization measures.
Abstract:
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.
Related Concept Videos
01:29Disturbances in Heart Rhythm
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
01:29Dysrhythmias III: Characteristics of Dysrhythmias
01:18Dysrhythmias IV: Characteristics of Bradyarrhythmias
01:25ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias
01:28Dysrhythmias II: Classification of Tachyarrhythmias
01:16ECG Interpretation of Arrhythmias I: Sinus Arrhythmias
Types of Arrhythmias
Sinus Node Arrhythmias
Sinus Bradycardia: Originating from the sinoatrial (SA) node, sinus bradycardia involves slower impulses, resulting in a heart rate of less than 60 beats per minute (bpm). Causes include sleep, vagal stimulation, beta-blockers, hypothyroidism,...