A Case of Acute Myocardial Infarction During Rapid Ascent to High Altitude

Abstract

Medical history: Male, 46 years old, driver. A long-term resident of the plains with no history of hypertension or altitude-related hypertension. High-altitude BP at 110/70-120/80 mmHg, fasting blood glucose at 6.6 mmol/L (health check indicated elevated fasting blood glucose; no further examinations conducted), previously undiagnosed diabetes, no thyroid-related disorders. Pre-altitude health assessment: BMI: 27.27, uric acid: 446 µmol/L (2023), 457 µmol/L (2024). No smoking history; occasional alcohol consumption in small amounts (approximately 50-150 g each time, 1-2 times per month). Symptoms developed about 12 h after driving from the plains to an average altitude of 2,580 m.Symptoms and signs: Sudden onset of squeezing pain behind the sternum after breakfast. Accompanied by palpitations, fatigue, numbness in the fingertips, and soreness in the jaw, the patient is observed sweating profusely with a distressed expression. BP 141/89 mmHg, HR 110 beats/min, SpO2 91% (not on supplemental oxygen), R 28 breaths/min. Consciousness is clear, no cough or pink frothy sputum, no significant respiratory distress, and no obvious abnormalities in urination or defecation. Physical examination: Bilateral pupils are equal and round, no neck stiffness, no dry or wet rales heard in both lungs, normal muscle strength and tone in the limbs, physiological reflexes present, and pathological reflexes not elicited. The patient developed upper back pain 0.5 h after symptom onset.Diagnostic methods: Bedside electrocardiogram shows ST segment elevation in leads V1-V5 and frequent premature ventricular contractions (PVCs). A complete myocardial enzyme profile, prothrombin time (PT), D-dimer, C-reactive protein (CRP), biochemical tests, chest CT, and other relevant examinations were conducted. A repeat electrocardiogram was performed.Treatment methods: Cardiac monitoring and vital sign observation were administered, and venous access was established. Due to limitations in field medical care, percutaneous coronary intervention (PCI) could not be performed. According to the “Guideline for rational medication of ST-segment elevation myocardial infarction in primary care,”[1] and considering the unique circumstances of high altitude, the following treatment plan was implemented on-site: (1) Clopidogrel loading dose of 300 mg and aspirin 300 mg (chewed for rapid absorption) for antithrombotic therapy; (2) 2 million units of Urokinase dissolved in 100 ml of normal saline (administered intravenously over 45 min) for thrombolysis (1.5 h after symptom onset). During thrombolysis, cardiac monitoring showed BP 110-140/60-86 mmHg, HR 30-80 beats/min, and R 24 breaths/min. (3) Emergency oxygen therapy. The oxygen flow rate is set at 4 L/min via nasal cannula for continuous delivery and results in oxygen saturation levels of 95-97%.Clinical outcome: After thrombolysis, the chest pain decreased, and a repeat electrocardiogram still indicated the presence of PVCs, with ST-segment elevation reduced compared to before. Following the administration of morphine for pain relief, the patient was transferred to the Chest Pain Center at West China Hospital, Sichuan University, approximately 4 h after symptom onset. During transport, the patient remained strictly in bed and received continuous oxygen at 2-4 L/min. Throughout the transfer, the chest pain intensity gradually reduced. Cardiac monitoring during transport showed BP 120/60-140/89 mmHg, heart rate 50-90 beats/min, respiration rate 21-24 breaths/min, and SpO2 91%-97%; there were no instances of urination or defecation. The patient was admitted to West China Hospital, Sichuan University, 16 h after symptom onset, and received PCI. After one day of post-operative observation, the patient was discharged and returned home without any discomfort.