title: The effect of respiration on normal and abnormal Q waves. An electrocardiographic and vectorcardiographic analysis.
abstract: The diagnostic significance of Q waves in Leads II, III, and aVF when analyzed retrospectively remains controversial. Persistence of the Q wave on inspiration is said to reflect inferior infarction. Studies in the past, which have evaluated respiratory variation as a means to separate normal from abnormal Q waves, were performed utilizing the ECG only, were often retrospective, and frequently there was inadequate documentation of myocardial infarction. The present study was performed prospectively and utilized both electrocardiographic and vectorcardiographic analysis of the first 30 msec. vector before and after inspiration in 33 patients with documented acute myocardial infarction and in 22 normal volunteers. Inferior myocardial infarction was documented prospectively by ECG, VCG, by conventional enzymes, and by MB CPK. The VCG demonstrated increased sensitivity over that of the ECG, but the effect of inspiration noted on ECG and VCG was variable and extremely unreliable as a means of separating normal from abnormal Q waves.
mesh_terms: D004562:Electrocardiography; D006801:Humans; D009203:Myocardial Infarction / Q000175:diagnosis*; D011446:Prospective Studies; D012119:Respiration; D014672:Vectorcardiography