Electrocardiography in people living at high altitude of Nepal

Prevalence of hypertension and its relationship with altitude in highland areas: a systematic review and meta-analysis

This systematic review and meta-analysis synthesized the pooled prevalence of hypertension at high altitudes and explored its correlation with altitude using studies published in Chinese and English from database inception to February 2021. A systematic literature search was conducted among bibliographic databases (PubMed, Embase, and Web of Science) and three Chinese databases (CNKI, VIP, and Wanfang data) to identify eligible studies. A random-effects model was used to calculate the overall pooled prevalence of hypertension. The I² statistic was used to assess heterogeneity across studies. Random-effects meta-regression was conducted to investigate covariates that may have influenced between-study heterogeneity. The pooled prevalence of hypertension among the general population in high-altitude areas was 33.0% (95% CI: 29.0-38.0%), with high between-study heterogeneity (I² = 99.4%, P < 0.01). Subgroup analyses showed the pooled prevalence of hypertension in Tibetan individuals was significantly higher than that in non-Tibetan individuals living in the Himalayas and Pamir Mountains (41% vs. 18%). A trend toward an increase in the prevalence of hypertension was found with every 100-m increase in elevation (coefficient: 0.012, 95% CI: -0.001 to 0.025, P = 0.069) only in Tibetan individuals. In addition, in these individuals, we found an increase in mean diastolic BP with each 100-m increase in altitude (coefficient: 0.763, 95% CI: 0.122-1.403, P = 0.025). Our meta-analysis suggests that the pooled prevalence of hypertension among the general population in high-altitude areas is 33.0%. Subjects of Tibetan ethnicity were more prone to developing hypertension at high altitudes. However, a very weak relationship between altitude and the prevalence of hypertension was found only in Tibetan individuals.

A systematic review of electrocardiographic changes in healthy high-altitude populations

High-altitude environments are characterized by decreased atmospheric pressures at which individuals exhibit a reduced volume of maximal oxygen uptake and arterial partial pressure of oxygen, both of which lead to hypobaric hypoxia. While acute exposure may temporarily offset cardiovascular homeostasis in sea-level residents, native highlanders have become accustomed to these high-altitude conditions and often exhibit variations in normal ECG parameters. As part of the "Altitude Non-differentiated ECG Study" (ANDES) project, this paper aims to systematically review the available literature regarding ECG changes in healthy highlander populations. After searching the PubMed, Medline, and Embase databases, 286 abstracts were screened, of which 13 full-texts were ultimately included. This process was completed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Major ECG deviations in native healthy highlanders include right QRS axis deviation, right ventricular hypertrophy signs, and more prevalent T-wave inversion in the right precordial leads. Notably, they exhibit a prolonged QTc compared to sea-level residents, although within normal limits. Evidence about increased P-wave amplitude or duration, variations in PR interval, or greater prevalence of complete right bundle branch block is not conclusive. This review provides ECG reference standards that can be used by clinicians, who should be aware of the effects of high-altitude residence on cardiovascular health and how these may change according to age, ethnicity, and other factors.

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

INTRODUCTION

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.