Acute Ischemic Stroke at High Altitudes in China: Early Onset and Severe Manifestations

Abstract

The detailed characteristics of strokes at high altitudes in diverse nations have not been extensively studied. We retrospectively enrolled 892 cases of first-ever acute ischemic strokes at altitudes of 20, 2550, and 4200 m in China (697 cases from Penglai, 122 cases from Huzhu, and 73 cases from Yushu). Clinical data and brain images were analyzed. Ischemic strokes at high altitudes were characterized by younger ages (69.14 ± 11.10 vs. 64.44 ± 11.50 vs. 64.45 ± 14.03, p < 0.001) and larger infract volumes (8436.37 ± 29,615.07 mm³ vs. 17,213.16 ± 47,044.74 mm³ vs. 42,459 ± 84,529.83 mm³, p < 0.001). The atherosclerotic factors at high altitude, including diabetes mellitus (28.8% vs. 17.2% vs. 9.6%, p < 0.001), coronary heart disease (14.3% vs. 1.6% vs. 4.1%, p < 0.001), and hyperlipidemia (20.2% vs. 17.2% vs. 8.2%, p = 0.031), were significantly fewer than those in plain areas. Polycythemia and hemoglobin levels (138.22 ± 18.04 g/L vs. 172.87 ± 31.57 g/L vs. 171.81 ± 29.55 g/L, p < 0.001), diastolic pressure (89.98 ± 12.99 mmHg vs. 93.07 ± 17.79 mmHg vs. 95.44 ± 17.86 mmHg, p = 0.016), the percentage of hyperhomocysteinemia (13.6% in Penglai vs. 41.8% in Huzhu, p < 0.001), and the percentage of smoking (33.1% in Penglai vs. 50.0% in Huzhu, p = 0.023) were significantly elevated at high altitudes. We concluded that ischemic stroke occurred earlier and more severely in the Chinese plateau. While the atherosclerotic factors were not prominent, the primary prevention of strokes at high altitudes should emphasize anticoagulation, reducing diastolic pressure, adopting a healthy diet, and smoking cessation.

Keywords: acute ischemic stroke; altitude; neuroimaging; polycythemia; risk factors.

Figure A1

Histogram of frequency distribution of first-ever acute ischemic stroke infarct volume in three groups. Most patients possessed a first-ever ischemic stroke infarct volume in the range of 0–25,000 mm³ (Penglai) or 0–50,000 mm³ (Huzhu and Yushu). While there were still a significant number of patients with catastrophic infarct volumes in the range of 50,000–500,000 mm³, leading to a skewed distribution of infarct volume data in all three areas and mean values much smaller than its corresponding standard deviations. A. Histogram of data from Penglai: minimum-35.71 mm³, maximum-294,400 mm³, 25th percentile-413.55 mm³, 50th percentile-1081.00 mm³, 75th percentile-3693.50 mm³. B. Histogram of data from Huzhu: minimum-100.10 mm³, maximum-404,900.00 mm³, 25th percentile-419.65 mm³, 50th percentile-1359.50 mm³, 75th percentile-12,622.50 mm³. C. Histogram of data from Yushu: minimum-48.35 mm³, maximum-474,300.00 mm³, 25th percentile-1310.50 mm³, 50th percentile-5270.00 mm³, 75th percentile-28,205.00 mm³.

Figure 1

Topographic map of China and the geographical location of the three areas.

Figure 2

Using the software ITK-SNAP to obtain infarct volume by manual segmentation.