急性冠心症（acute coronary syndrome, ACS）的臨床表現多變，早期識別非典型ST段上升急性心肌梗塞（ST-elevation myocardial infarction）相當重要，當延遲診斷或處置時會導致高死亡率。本案例是一位 59 歲男性病人，於家中出現胸悶由救護車送至本院，到院前十二導程心電圖可見超急性T波，到院後十二導程心電圖無典型ST段上升，且無心肌旋轉蛋白I上升，但HEART Score為6分屬中等風險，需留院觀察；到院43分鐘後胸悶緩解，但開始呼吸急促、冒冷汗與血壓下降，十二導程心電圖出現R波遞增不良，回溯先前運動心電圖為陽性反應，經全面性評估確診為非典型ST段上升急性心肌梗塞，於心導管檢查和經皮冠狀動脈介入治療後，臨床症狀改善順利出院。針對初期以典型胸悶為表現的案例，若無典型ST段上升變化，不應只憑一次心電圖即排除ST段上升急性心肌梗塞，需將非典型ST段上升急性心肌梗塞列為鑑別診斷之一，以免錯失最佳治療時機。

The clinical manifestations of acute coronary syndrome (ACS) are highly variable. Early recognition of atypical ST-elevation myocardial infarction (STEMI) is extremely important, as delayed diagnosis and treatment can result in a high mortality rate. The case involves a 59-year-old male who experi-enced chest tightness at home and was transported to our hospital by ambulance. The pre-hospital 12-lead electrocardiogram (ECG) showed hyperacute T waves. However, upon arrival at the hospital, his 12-lead ECG did not reveal typical ST-segment elevation, and his troponin I level remained within the normal range. Given his HEART Score of 6, indicating moderate risk, he was admitted for further observation. After 43 minutes of hospital arrival, his chest tightness subsided but was followed by shortness of breath, cold sweating, and hypotension, with the 12-lead ECG revealing poor R-wave pro-gression. A retrospective review of his prior treadmill exercise test showed a positive result. Following a comprehensive evaluation, he was diagnosed with atypical STEMI. He subsequently underwent cor-onary angiography and percutaneous coronary intervention (PCI), which resulted in significant clini-cal improvement, leading to a successful discharge. For patients presenting with typical chest tightness but lacking definitive ST-segment elevation, STEMI should not be ruled out based solely on a single ECG. Instead, atypical STEMI should be considered as part of the differential diagnosis to avoid miss-ing the optimal window for treatment.