Clinical Significance of QS Complexes in V1 and V2 without Other Electrocardiographic Abnormality

Background: In the absence of other electrocardiographic (ECG) abnormalities, QS deflections simultaneously in both of the leads V₁–V₂ may have multiple possible causes. Despite much information in the literature indicating that this is an unlikely pattern for pure septal infarction, such an ECG diagnosis is frequently given. Methods: Ninety‐nine cases having QS deflections in both leads V₁ and V₂ but no other ECG abnormality were compared to 99 other patients with entirely normal ECGs, to whom they were matched by age, gender, and the presence or absence of septal Q waves. Retrospective analysis of medical records was performed to determine the nature of any cardiovascular disease in these two groups, and to find a possible explanation for the ECG abnormality. Results: Because of its intermittence in subjects with multiple ECGs, QS deflections in leads V₁–V₂ appeared most often to be an artifact of precordial lead placement. Prior myocardial infarction, or presence of clinical coronary disease was present in only about 20% of the cases. Neither the intermittence of Q wave in V₂ on repeated ECGs nor the absence of septal Q waves was useful in distinguishing between those with and without coronary heart disease. Conclusions: This ECG pattern is a sign of prior myocardial infarction in only a minority of cases, and in the latter, infarction limited to the interventricular septum is exceptional. This ECG finding should be interpreted as a nonspecific QRS abnormality with multiple possible causes. Clinical correlation and repeat tracings with attention to lead placement will help to clarify its significance.