RESUMO
This study evaluated the possibility of diagnosing chronic myocardial infarction in the presence of the pacing electrocardiogram. Forty-five patients with known myocardial infarction (anterior 23, inferior 22) and 26 healthy controls were studied. After coronary angiography, pacing was applied from the right ventricular apex, and the sensitivity, specificity, and average diagnostic accuracy of five criteria on the paced electrocardiogram were assessed: (1) Notching 0.04 second in duration in the ascending limb of the S wave of leads V3, V4, or V5 (Cabrera's sign); (2) Notching of the upstroke of the R wave in leads I, aVL, or V6 (Chapman's sign); (3) Q waves > 0.03 second in duration in leads I, aVL, or V6; (4) Notching of the first 0.04 second of the QRS complex in leads II, III, and aVF; (5) Q wave > 0.03 second in duration in leads II, III, and aVF. The most sensitive criteria, for anterior and inferior myocardial infarctions were Cabrera's and Chapman's (91.1 and 86.6%, respectively). All criteria had low specificity (range 42.3-69.2%). The combination of Cabrera's and Chapman's sign decreased the sensitivity to 77.7%, but increased specificity to 82.2%. The sensitivity and specificity of all the criteria were independent of the myocardial infarction site. In paced patients, the application of electrocardiographic criteria, and especially the combination of Cabrera and Chapman, provides useful clinical information in recognizing prior myocardial infarction but not in assigning the specific infarct site.
