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[QT dispersion and characteristics of left ventricular hypertrophy in primary hypertension]
Leszek Szymański1, Tadeusz Mandecki, Romuald Twardowski
1II Katedra i Klinika Kardiologii Sl. AM w Katowicach.
Insights
Asymmetrical left ventricular hypertrophy in hypertensive patients significantly increases QT dispersion, a measure of heart electrical instability. However, this increased QT dispersion does not appear to affect the occurrence of ventricular arrhythmias.
Area of Science:
- Cardiology
- Electrophysiology
- Hypertension Research
Background:
- Left ventricular hypertrophy (LVH) is a common complication of hypertension.
- The relationship between LVH asymmetry and cardiac electrical activity, specifically QT dispersion, requires further investigation.
- QT dispersion is a marker of repolarization heterogeneity and a potential predictor of arrhythmias.
Purpose of the Study:
- To evaluate QT dispersion and arrhythmia severity in hypertensive patients with symmetrical versus asymmetrical left ventricular hypertrophy.
- To determine the correlation between the asymmetry index (AI) of LVH and QT dispersion parameters.
- To assess the relationship between LVH, QT dispersion, and the occurrence of ventricular and supraventricular arrhythmias.
Main Methods:
- A study involving 47 hypertensive patients, categorized into symmetrical (Group I) and asymmetrical (Group II) LVH groups, and 20 healthy controls (Group III).
- Assessment of LVH asymmetry using an asymmetry index (AI) derived from echocardiographic measurements of ventricular wall thickness.
- Utilized standard 12-lead ECG, 24-hour Holter monitoring, and echocardiography to analyze QT dispersion (QTd, QTdc, QTdR) and arrhythmia frequency.
Main Results:
- Hypertensive patients with asymmetrical LVH (Group II) exhibited significantly higher QT dispersion (QTd, QTdc, QTdR) compared to those with symmetrical LVH (Group I) and controls (Group III).
- A strong positive correlation was observed between the asymmetry index (AI) and all QT dispersion parameters (p < 0.001).
- Supraventricular premature complexes were significantly more frequent in patients with asymmetrical LVH compared to both symmetrical LVH and control groups.
Conclusions:
- Left ventricular hypertrophy in primary hypertension can increase QT dispersion, with asymmetry exacerbating this effect.
- Increased QT dispersion in hypertensive patients does not significantly correlate with the frequency of ventricular arrhythmias.
- The study highlights the impact of LVH asymmetry on cardiac repolarization but suggests a limited role in predicting ventricular ectopy.
Unlabelled:
The aim of the study was to evaluate the QT dispersion and the severity of arrhythmias in hypertensive patients according to the asymmetry of the left ventricular hypertrophy. The study group consisted of 47 hypertensive patients. In 24 of them the left ventricular hypertrophy was symmetrical (group I) and in 23--asymmetrical (group II). For the evaluation of the left ventricular hypertrophy its thickness was analyzed in 13 segments. The ratio between the maximum and minimum thickness from any location was determined as the asymmetry index (AI). The value of this index 1,3 distinguished between patients with the symmetrical and asymmetrical left ventricular hypertrophy. 20 healthy subjects were examined as a control group (group III). All subjects underwent physical examination, the standard 12-lead electrocardiogram (ECG), twenty-four hour Holter recording and echocardiography. All the results for the QT dispersion (QTd, QTdc, QTdR) were highest in group II, lower in patients from group I and the lowest were observed in the control group. The differences in all parameters between group I and II were statistically significant: for QTd--V p < 0.01, QTdc--p < 0.05, QTdR--p < 0.05. The differences between groups II and III as well as I and III were statistically significant for all QT dispersion parameters: for QTd--p < 0.001 and p < 0.01 respectively, QTdc--p < 0.001, QTdR--p < 0.001 for both groups. We have observed a very distinct positive correlation between the asymmetry index and QTd, QTdc, QTdR (p < 0.001). These values correlated also, but less distinctly with the left ventricular mass index--LVMI (p < 0.05). The frequency and severity of ventricular ectopic beats did not differ significantly between group I and II. The results obtained indicate the lack of connection between the frequency of ventricular premature complexes and (1) all QT dispersion parameters, (2) LVMI, (3) AI. Supraventricular premature complexes occurred significantly more frequently in patients with the asymmetrical left ventricular hypertrophy compared to the group with the regular left ventricular hypertrophy (p < 0.05) and control group (p < 0.01).
Conclusions:
The left ventricular hypertrophy in primary hypertension may increase the QT dispersion. It seems that asymmetry of the left ventricular hypertrophy reinforces this increase. The increased QT dispersion in primary hypertension does not influence significantly the occurrence of ventricular arrhythmias.