Objective: To analyze the clinical manifestations of a huge inverted T wave and to summarize the causes of misdiagnosis of deformed papillary muscle as myocardial ischemia. Cases and Results: A retrospective analysis of the clinical data of 215 patients with 12-lead ECG T wave inverted myocardial ischemia from 2006 to 2018 in our hospital. Combined with multi-factor logistic regression analysis of echocardiography and electrocardiogram, we evaluated 11 cases of unique clinical malformed papillary muscles with lowered position. The electrocardiogram showed sinus rhythm, the electrocardiogram axis was normal, and the T wave inversion was 6-10 mm. The angiography showed no abnormalities. The echocardiogram showed that the left ventricular wall structure, motion, and left ventricular ejection fraction were within the normal range. Echocardiography showed that the anterolateral papillary muscle base of 11 patients originated from the apex 1/3. A 12-lead ECG with deformed papillary muscles shows that a huge inverted T wave is not a feature of myocardial ischemia. In this case, the 12-lead ECG feature is insufficient to identify the cause of myocardial ischemia. Therefore, we must exclude these myocardial ischemia in order to diagnose and treat correctly. Conclusion: Conventional 12-lead electrocardiogram shows that the giant inverted T wave of the deformed papillary muscles is diagnosed as myocardial ischemia, which is a misdiagnosis.