DETECTION OF INFERIOR MYOCARDIAL INFARCTI ONS BY AMBULATORY ELECTROCARDIOGRAPHY - SENSITIVITY OF 9 BIPOLAR LEADS

The sensitivity of ambulatory electrocardiography (Holter ECG) for det ecting ischaemia is relatively low. A case report of an inferior infar ction missed by three-lead Holter monitoring that included a modified lead aVF especially places its sensitivity for detecting inferior isch aemia and infarction in question. Therefore, the present study evaluat ed the sensitivity of nine bipolar Holter leads for detecting isolated inferior Q-wave infarctions, and compared the sensitivity of the modi fied leads II, III, and aVF of the Holter ECG with the sensitivity of the ''corresponding'' leads of the standard ECG. Methods: Sixteen pati ents, each of whom had a pathological Q-wave (>0.04 s and >0.1 mV) in at least two of the three standard ECG leads II, III, and aVF but in n one of the other standard leads, were studied for the presence of a pa thological Q-wave on the modified Holter leads II, III, aVF, CM2, CM5, CR4, Frank Z, Nehb D, and inverse Nehb J. Results: Of the nine Holter leads, modified lead III provided the highest sensitivity for detecti ng inferior Q-wave infarctions, followed by lead Frank Z; leads CR 4 a nd inverse Nehb J were only slightly less sensitive. In contrast, modi fied leads II and aVF were significantly less sensitive than modified lead III. Modified bipolar lead aVF of the Holter ECG was significantl y less sensitive than the ''corresponding'' lead aVF of the standard E CG, whereas modified leads II and III provided similar sensitivities f or detecting inferior Q-wave infarctions as the ''corresponding'' lead s of the standard ECG. Conclusions: The significantly lower sensitivit y of modified lead aVF for detecting inferior Q-wave infarctions compa red with standard lead aVF shows that the sensitivity of a Holter ECG lead cannot be deduced from that of the ''corresponding'' standard ECG lead. Moreover, the significantly higher sensitivity of modified lead III compared with modified leads II and aVF shows that lead selection is important for Holter monitoring.