The effect of moderate altitude on Tp-e interval, Tp-e/QT, QT, cQT and P-wave dispersion

Long-time exposure to high altitude leads to changing at the respiratory, cardiovascular and hematological systems. There is no sufficient study about cardiovascular changes in moderate altitude. The distance between the peak and the end of the T wave (Tp-e) is a measure of transmyocardial distribution of repolarization and may be associated to dangerous rhythm disorders and ventricular arrhythmias. Again, P-wave dispersion (PWD) described as the extension of interatrial and intraatrial conduction time and inhomogeneous spread of sinus pulses are well recognized electrophysiologic features in patients with atrial fibrillation. We aimed to compare repolarization parameters (Tp-e interval, Tp-e/QT ratio, QT, cQT) and P wave dispersion between healthy people living at moderate altitude and sea level.

In this study included 80 healthy people living at moderate altitude (1600 m, Group I) and 90 people living at sea level (0-4 m, Group II). All people were born and grew up at the same altitude area. Being migrant to living area, people with structural heart disease, rhythm disorders, pulmonary diseases or any systemic chronic disease were excluded criteria in the study. Tp-e interval, QT interval, cQT, Tp-e/QT ratio, P wave durations and PWD were measured from D2 and V5 leads with 20 mm/mV amplitude and 50 mm/s rate. All the measurements were repeated three times and were evaluated manually with a magnifying glass.

There were no differences in baseline demographic, laboratory, echocardiographic parameters and coronary artery risk factors. The QRS duration (94.2 ± 14.8 msn and 90.2 ± 9.3 msn, p = 0.05) and corrected QT time (415.8 ± 20.1 msn and 403.9 ± 20.5 msn; p = 0.001), Tp-e interval (86.5 ± 11.7 msn and 80.5 ± 10.4 msn p = 0.001) and Tp-e/QT ratio (0.23 ± 0.03 msn and 0.22 ± 0.03 msn p = 0.011) were statistically significantly higher in the moderate altitude group. P wave maximum, minimum time and PWD were similar in both groups (p > 0.05).

Moderate altitude leads to subclinical electrocardiographic changes in healthy individuals such as high altitude. Repolarization parameters (Tp-e interval, Tp-e/QT ratio, and cQT) are prolonged without cardiac structural changes. It should be kept in mind that people living in moderate altitude may be more susceptible to arrhythmia in the future, and findings should be supported in large randomized trials.