[Monitoring of ischemic changes of the QRS complex with a new system of computerized electrocardiography]

Evoked ischemia induces morphological modifications in QRS complex that can be detected by a new electrocardiographic computerized system that we have developed (ventricular ischemic site analysis-VISA). The aim of this study was to evaluate, by continuous recording, the ischemia evolution during stress or pharmacological test and to correlate the modifications of QRS with the shift of the ST-T segment.

According to our method, the vectorial differences between rest QRS and stress QRS are recorded as deformations of the QR and/or RS segments. Sixty patients were studied: 44 had inducible ischemia during single photon emission computed tomography 99mTc-sestamibi test; 33 of these underwent ergometric test and 11 pharmacological test.

The VISA test was positive in 91% of patients against the 61% with standard ECG. Ischemic deformations of the QRS appeared at 62.1% of stress duration, while the ST-T shift appeared at 81.4% of the test. During pharmacological stress the ST-T segment did not change.

Our method is more sensitive than standard ECG in identifying inducible ischemia. Ischemic deformations of the QRS complex occur earlier than the repolarization modifications and they may be present also in their absence. The higher sensitivity of the VISA test depends on the fact that QRS ischemic modifications are caused both by the lesion current and a conduction delay in the ischemic zone.