The effect of altitude on P-wave and QT duration and dispersion

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.

Long-Term High-Altitude Exposure Does Not Increase the Incidence of Atrial Fibrillation Associated with Organic Heart Diseases

Wang, Man, Mengxue Liu, Jia Huang, Dan Fan, Shengzhong Liu, Tao Yu, Keli Huang, Xinchuan Wei, and Qian Lei. Long-term high-altitude exposure does not increase the incidence of atrial fibrillation associated with organic heart diseases. High Alt Med Biol. 00:000-000, 2021.- Background: Atrial fibrillation (AF) is one of the most common arrhythmias and is associated with several complications following cardiac surgery. However, the differences in the incidence of AF associated with organic heart diseases between highland and lowland populations have not been comprehensively studied. Methods: In this retrospective study, a total of 2,316 highland and lowland patients who underwent cardiac surgery between January 2013 and December 2018 in a single center were enrolled. According to the altitude of residence, patients were divided into high-altitude (>1,500 m) and low-altitude (<1,500 m) groups. A propensity score matching analysis was performed to estimate the association of lifetime high-altitude exposure with AF. Results: Among the enrolled patients, 239 (10.9%) were from a high-altitude plateau, while 1,946 (89.1%) were from a low-altitude area. There were statistical differences in age, gender, European System for Cardiac Operative Risk Evaluation, and other factors, between the two groups (p < 0.05). According to the propensity score, 237 patients in the high-altitude group were successfully matched to 237 patients in the low-altitude group without significant difference in baseline data (p > 0.05). Among the matched patients, 125 patients (26.4%) suffered from AF, with 66 (27.8%) in the high-altitude group and 59 (24.9%) in the low-altitude group. The incidence of AF was statistically similar between the two groups and not significantly influenced by long-term high-altitude exposure (odds ratio 1.07; 95% confidence interval 0.71-1.60, p > 0.05). Conclusion: Long-term high-altitude exposure did not significantly increase the occurrence of AF in patients with organic heart diseases. Clinical Trial No. ChiCTR1900028612.

Altered cardiac repolarisation in highlanders with high-altitude pulmonary hypertension during wakefulness and sleep

High-altitude pulmonary hypertension (HAPH) is an altitude-related illness associated with hypoxaemia that may promote sympathetic excitation and prolongation of the QT interval. The present case-control study tests whether QT intervals, markers of malignant cardiac arrhythmias, are prolonged in highlanders with HAPH (HAPH+) compared to healthy highlanders (HH) and healthy lowlanders (LL). The mean pulmonary artery pressure (mPAP) was measured by echocardiography in 18 HAPH+ (mPAP, 34 mmHg) and 18 HH (mPAP, 23 mmHg) at 3,250 m, and 18 LL (mPAP, 18 mmHg) at 760 m, Kyrgyzstan (p < .05 all mPAP comparisons). Groups were matched for age, sex and body mass index. Electrocardiography and pulse oximetry were continuously recorded during nocturnal polysomnography. The heart rate-adjusted QT interval, QTc, was averaged over consecutive 1-min periods. Overall, a total of 26,855 averaged 1-min beat-by-beat periods were semi-automatically analysed. In HAPH+, maximum nocturnal QTc was longer during sleep (median 456 ms) than wakefulness (432 ms, p < .05) and exceeded corresponding values in HH (437 and 419 ms) and LL (430 and 406 ms), p < .05, respectively. The duration of night-time QTc >440 ms was longer in HAPH+ (median 144 min) than HH and LL (46 and 14 min, p < .05, respectively). HAPH+ had higher night-time heart rate (median 78 beats/min) than HH and LL (66 and 65 beats/min, p < .05, respectively), lower mean nocturnal oxygen saturation than LL (88% versus 95%, p < .05) and more cyclic oxygen desaturations (median 24/hr) than HH and LL (13 and 3/hr, p < .05, respectively). In conclusion, HAPH was associated with higher night-time heart rate, hypoxaemia and longer QTc versus HH and LL, and may represent a substrate for increased risk of malignant cardiac arrhythmias.

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.

Effects of Nasal Septum Deviation and Septoplasty on Cardiac Arrhythmia Risk

OBJECTIVE

Upper airway obstruction (UAO) can result in cardiac complications, including arrhythmias and sudden cardiac death. Nasal septum deviation (NSD) is a common cause of UAO. The aim of this study was to assess the risk of cardiac arrhythmias in patients with NSD. To assess this risk, we measured noninvasive indicators of atrial arrhythmia (P-wave dispersion [Pd]) and ventricular arrhythmia (corrected QT dispersion [QTcd]) and compared these values between NSD patients and healthy subjects.

STUDY DESIGN

Prospective study.

SETTINGS

Tertiary referral center.

SUBJECTS AND METHODS

This study included 53 consecutive patients who had underwent septoplasty due to marked NSD. Electrocardiographic records were used to determine Pd and QTcd values preoperatively and 6 months postoperatively. Fifty-three consecutive age- and sex-matched subjects without any UAO were also examined as a control group.

RESULTS

Preoperative Pd and QTcd values were significantly higher in NSD patients than in the control group (Pd: 57.40 ± 14.21 vs 34.11 ± 7.12 milliseconds, P < .001; QTcd: 81.77 ± 16.39 vs 50.25 ± 11.51 milliseconds, P < .001, respectively). In addition, Pd and QTcd values were significantly greater in preoperative NSD patients when compared with the same patients postoperatively (Pd: 57.40 ± 14.21 vs 36.32 ± 8.9 milliseconds, P = .013; QTcd: 81.77 ± 16.39 vs 55.76 ± 11.4 milliseconds, P = .012, respectively).

CONCLUSION

In conclusion, NSD patients are at risk for both atrial and ventricular cardiac arrhythmias; however, septoplasty in these patients can relieve UAO and reduce the risk of arrhythmias.

Meta-analysis of p-wave dispersion values in healthy individuals: the influence of clinical characteristics

BACKGROUND

P-wave dispersion (Pd) is an appealing marker for predicting the risk of developing atrial fibrillation. At present, no definitive cutoff value has been determined as to the diagnosis of high-risk patients. Our aims were to evaluate P-wave parameters of healthy subjects published in the literature, determine normal range and weighted means of Pd and P-wave parameters, and investigate the influences of gender, age, and BMI on the weighted results.

METHODS

A systematic search of studies published in PubMed was conducted. Only studies which included control groups of healthy individuals were included.

RESULTS

Of the 657 studies initially identified, 80 were eligible for inclusion. The total number of participants was 6,827. The highest reported Pd values were 58.56 ± 16.24 ms; the lowest were 7 ± 2.7 ms. The weighted mean was 33.46 ± 9.65 ms; weighted median was 32.2 ms. Gender and age were not found to be associated with significant influences on P-wave parameter values. High-normal BMI was not found to be associated with increased P-wave parameter values.

CONCLUSIONS

Pd, Pmax, and Pmin span a wide range of values in healthy individuals. Seemingly, abnormal values were often reported in healthy adults. The high variability of P-wave parameters in healthy individuals, and overlapping of the results with those reported for patients with increased risk for atrial fibrillation, might suggest that this technique has limited sensitivity and specificity. The variability between studies may stem from methodological issues and, therefore, there is a definite need for methodological standardization of Pd measurements.

Evaluation of QT and P wave dispersion and mean platelet volume among inflammatory bowel disease patients

BACKGROUND

In inflammatory bowel disease (IBD) number of thromboembolic events are increased due to hypercoagulupathy and platelet activation. Increases in mean platelet volume (MPV) can lead to platelet activation, this leads to thromboembolic events and can cause acute coronary syndromes. In IBD patients, QT-dispersion and P-wave dispersion are predictors of ventricular arrhythmias and atrial fibrilation; MPV is accepted as a risk factor for acute coronary syndromes, we aimed at evaluating the correlations of these with the duration of disease, its localization and activity.

METHODS

The study group consisted of 69 IBD (Ulcerative colitis n: 54, Crohn's Disease n: 15) patients and the control group included 38 healthy individuals. Disease activity was evaluated both endoscopically and clinically. Patients with existing cardiac conditions, those using QT prolonging medications and having systemic diseases, anemia and electrolyte imbalances were excluded from the study. QT-dispersion, P-wave dispersion and MPV values of both groups were compared with disease activity, its localization, duration of disease and the antibiotics used.

RESULTS

The P-wave dispersion values of the study group were significantly higher than those of the control group. Duration of the disease was not associated with QT-dispersion, and MPV levels. QT-dispersion, P-wave dispersion, MPV and platelet count levels were similar between the active and in mild ulcerative colitis patients. QT-dispersion levels were similar between IBD patients and the control group. No difference was observed between P-wave dispersion, QT-dispersion and MPV values; with regards to disease duration, disease activity, and localization in the study group (p>0.05).

CONCLUSIONS

P-wave dispersion which is accepted as a risk factor for the development of atrial fibirilation was found to be high in our IBD patients. This demonstrates us that the risk of developing atrial fibrillation may be high in patients with IBD. No significant difference was found in the QT-dispersion, and in the MPV values when compared to the control group.

The effects of iron deficiency anemia on p wave duration and dispersion

OBJECTIVES

The association between P wave dispersion and iron deficiency anemia has not been documented in the literature. In this study, we evaluated P wave dispersion in patients with iron deficiency anemia and the possible relationships between P wave dispersion and other echocardiographic parameters.

INTRODUCTION

The iron status of an individual may play an important role in cardiovascular health. Anemia is an independent risk factor for adverse cardiovascular outcomes. P wave dispersion is a simple electrocardiographic marker that has a predictive value for the development of atrial fibrillation. Apart from cardiovascular diseases, several conditions, such as seasonal variation, alcohol intake and caffeine ingestion, have been demonstrated to affect P wave dispersion.

METHODS

The study included 97 patients who had iron deficiency anemia and 50 healthy subjects. The cases were evaluated with a clinical examination and diagnostic tests that included 12-lead electrocardiography and transthoracic echocardiography.

RESULTS

Compared to the control group, patients with iron deficiency anemia showed significantly longer maximum P wave duration (Pmax) (91.1 ± 18.0 vs. 85.8 ± 6.7 msec, p = 0.054), P wave dispersion (PWD) (48.1 ± 7.7 vs. 40.9 ± 5.6 msec, p < 0.001), mitral inflow deceleration time (DT) (197.5 ± 27.9 vs. 178.8 ± 8.9 msec, p < 0.001) and isovolumetric relaxation time (IVRT) (93.3 ± 9.2 vs. 77.4 ± 8.2 msec, p < 0.001); they also showed increased heart rate (85.7 ± 16.1 vs. 69.0 ± 4.4, p < 0.001) and frequency of diastolic dysfunction (7 (7.2%) vs. 0). Correlation analysis revealed that PWD was significantly correlated with IVRT, DT, heart rate, the presence of anemia and hemoglobin level.

CONCLUSIONS

Iron deficiency anemia may be associated with prolonged P wave duration and dispersion and impaired diastolic left ventricular filling.