AUTOMATED ST-SEGMENT ANALYSIS DURING CESAREAN DELIVERY - EFFECTS OF ECG FILTERING MODALITY

Study Objectives: To determine the effect of different electrocardiogr aphic (ECG) filtering modalities on ST-segment changes during cesarean delivery. We compared the use of narrow and standard bandwidth ECG fi ltering modes in assessing ECG-detected ischemic changes in healthy pa tients undergoing routine, elective cesarean delivery. Design: Prospec tive, nonrandomized clinical trial. Setting: Academic medical center. Patients: 20 healthy parturients undergoing elective cesarean delivery with regional anesthesia. Interventions: Continuous 5-lead ECG monito ring was performed in all 20 study parturients. The same incoming ECG signal was divided by a special cable and displayed on two Marquette 7 010 monitors. Leads I, II, and V5 were analyzed. One of the monitors f iltered the signal with a 0.07 to 100 Hz filter (DIAG), the other with a 0.3 to 40 Hz filter (MON). The ST segment was analyzed continuously by electronic comparison with a template established as a baseline at the beginning of the case. This continuous output was fed in digital form every 15 seconds to an IBM PC computer for data analysis. Measure ments and Main Results: In each of the leads analyzed, the mean MON ve rsus DIAG difference showed a bias, with MON showing consistently lowe r (ie, more negative) readings than DIAG. Using different criteria for ST depression (> 0.25, > 0.5, or > 1.0 mm), we categorized patients a s showing more ST depression on either MON or DIAG. With the 0.25 mm c riterion, ST depression was identified significantly more often in MON than DIAG in leads II and V5 (p < 0.05). Using the other criteria, th e differences were similar, but were not statistically significant. In general, very few instances of ST depression were identified in lead I. No patient had sequelae indicative of intraoperative myocardial isc hemia, such as chest pain, dyspnea, persistent ectopy, or hemodynamic instability. Conclusions: In patients at low risk for myocardial ische mia, narrow bandwidth (monitor mode) ECG filtering reveals greater deg rees of ST-segment depression than does standard (diagnostic mode) ECG filtering. Studies examining ST-segment phenomena would be facilitate d by including a description of the ECG filtering-technique. (C) 1996 by Elsevier Science Inc.