Clinical significance of QS complexes in V1 and V2 without other electrocardiographic abnormality

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.

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.

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.

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.