Effect of Isometric Exercise on QTc Interval.

Area of Science:

• Cardiology
• Exercise Physiology
• Autonomic Nervous System Function

Background:

• The QTc interval is influenced by heart rate, autonomic activity, and diseases like diabetes.
• The impact of exercise on QTc interval, despite its effect on autonomic function, remains unclear.
• Increased incidence of sudden cardiac death post-exercise suggests a link to QTc interval changes.

Purpose of the Study:

• To assess QTc interval variations following isometric exercise in healthy individuals.
• To investigate the influence of parental diabetes history on exercise-induced QTc changes.
• To correlate QTc duration with the LF-HF ratio, an indicator of autonomic balance.

Main Methods:

• Twenty-nine healthy medical students participated in a 5-minute isometric handgrip test.
• Electrocardiogram (ECG) was recorded before and at intervals after exercise.
• Statistical analysis included paired and unpaired t-tests for intra- and inter-group comparisons.

Main Results:

• Significant differences in QTc values were observed pre- and post-exercise, with lower values in Group I subjects.
• The LF:HF ratio significantly increased post-exercise compared to pre-exercise levels in both groups.
• No significant correlation was found between the LF:HF ratio and QTc duration.

Conclusions:

• Exercise induces measurable QTc interval changes in healthy individuals, which may increase arrhythmia risk in susceptible individuals.
• A prolonged QTc interval is a known risk factor for cardiac arrhythmias.
• Women might have a higher susceptibility to post-exercise arrhythmias due to longer baseline QTc intervals.