The ability of QRST isointegral maps to detect myocardial infarction in the presence of simulated left bundle branch block.

The clinical value of QRST isointegral maps (I-maps) for the detection of myocardial infarction (MI) in the presence of left bundle branch block (LBBB) was investigated. We recorded I-maps during sinus rhythm and right ventricular (RV) pacing, which simulated LBBB, in 62 patients with MI (42 patients had at least one akinetic segment and the remaining 20 patients had only hypokinesis or normal contraction) and 26 patients without MI. An abnormal decrease in the QRST value of the I-map was assessed by the difference map (D-map), which indicated a '-2SD area', where the QRST integral value was less than the lower limit of the normal range (mean -2SD) calculated from 608 normal individuals. The I-maps recorded during the two activation sequences were similar to each other in patients with and without MI (r = 0.87 and 0.92, respectively). The '-2SD area' was located over the left anterior chest in patients with an anterior MI and over the lower torso in patients with an inferior MI during each activation sequence. We were able to diagnose MI during simulated LBBB with a sensitivity of 84%, a specificity of 81% and a diagnostic accuracy of 83% when we used the criterion that MI is present if the sum of QRST integral values below the normal range (sigma DM) exceeds 100 mV.ms. We were able to diagnose an akinesis with a sensitivity of 81%, a specificity of 85% and a diagnostic accuracy of 83% when we used the criterion that akinesis is present if sigma DM exceeds 500 mV.ms during simulated LBBB.(ABSTRACT TRUNCATED AT 250 WORDS)