| Popis: |
Based on the premise that the QRS complex is also involved in reversible ischemia, we designed a computerized electrocardiographic method, that we have named Ventricular Ischemic Site Analysis (VISA). This method compares mean resting QRS to the QRS complex recorded during exercise or pharmacologic stress. The effect of ischemia on the electrical process of myocardial depolarization can be seen as a smaller slope in the QR and/or RS segment of the QRS signal, thus causing a local change in shape of the QRS. This method makes it possible to evaluate both the maximum entity of the change in shape and the time at which this occurs with reference to the beginning of the cycle. The VISA test was compared to SPECT and to the normal ECG stress test on a group of 53 patients who underwent a SPECT 99mTc-Sestamibi for suspected myocardial ischemia. Among the 39 patients confirmed as ischemic, the VISA test was positive in 37, while the ischemic alterations of the ST-T segment were observed in only 10 patients. According to this study, the sensitivity of the VISA test is comparable to the levels seen in SPECT. Moreover, this method demonstrates a trend towards localization of the ischemia in posterior or lateral sites when the shape change in localized in RS segment, and in anterior or infero-apical sites when the change is in QR segment. In addition to increasing sensitivity with respect to normal ECG stress tests, this method may also represent a new field of application for the ECG stress test, offering the possibility of localizing ischemic areas via simple computerized electrocardiography. |
