ECG criteria for left ventricular hypertrophy and ECG criteria for acute ischemia/ myocardial infarction represent two distinct categories. ECG signs of left ventricular hypertrophy (ECG-LVH) are based on so-called voltage criteria, i.e. the increased amplitude of QRS complex. On the other hand, the standard ECG diagnosis of MI is based on the presence of pathological Q waves and ST segment deviations and additionally on the so-called STEMI equivalents. However, animal, as well as clinical studies bring evidence on the occurrence of the increased QRS voltage /ECG-LVH signs in acute ischemia. This paper is focused on the pathophysiological mechanisms that are common for both hypertrophied and ischemic myocardium and thus can lead to identical QRS patterns. Recognizing the underlying mechanisms of the ECG-LVH patterns in myocardial ischemia has a strong clinical implication. The ECG-LVH signs/ the increased QRS voltage need to be recognized as a predictive electrophysiological marker independent of LV anatomy. Its misinterpretation in patients with acute coronary syndrome can lead to reperfusion delays and worst outcomes.