False positive ECG reports of anterior myocardial infarction in women

The prevalence of electrocardiographic poor R-wave progression was estimate d by reviewing all electrocardiograms recorded in Glasgow Royal Infirmary o ver a 2-week period. It was found to be higher in women (19% vs. 11%) than in men. To investigate one possible reason, the effect of chest electrode p ositioning in women was thereafter examined. Eighty four women were recruit ed to a study in which chest electrodes were placed strictly in adherence w ith recommendations of using the 4th and 5th intercostal spaces as referenc es and also using the mure widely adopted technique of placing electrodes V 3 to V6 under the left breast. R wave amplitudes were compared in V3 to V6 from both sets of recordings. It was found that measurements recorded on th e breast by electrode V3 have a significantly smaller R wave magnitude comp ared to corresponding measurements below the breast, the mean difference be ing 34 (95% confidence interval [CI] of 7 to 60) microvolts. For V5 and V6, the reverse is true with measurements taken on the breast being larger, on average, than those taken below the breast by 119 (95% CI of 87 to 152) an d 134 (95% CI of 108 to 160) microvolts respectively. For V4, there was no significant difference. Seventeen women with poor R wave progression sugges tive of old anterior myocardial infarction had clinical data examined from which it was determined that 11 had a history suggestive of myocardial infa rction, ie, the positive predictive value was 65% (95% CI of 42% to 87%). I t was concluded that positioning of electrodes beneath rather than on top o f the breast was not responsible for the increased prevalence of poor R wav e progression in women and that the criterion of isolated poor R wave progr ession was too nonspecific to be of clinical value.