Impedance cardiography-dipyridamole test in detecting coronary artery disease

Thallium-201 dipyridamole test (Tl-201DT) has high sensitivity and specificity in the assessment of coronary disease (CAD), but is not always available. We proposed impedance cardiography DT (IDT)instead. To determine the characteristic changes of impedance cardiogram (ICG) in patients with typical angina and to compare with those in normal subjects, 37 subjects undergoing IDT were divided into 3 groups: typical angina (15), suspected chest pain (11) and normals (11). Dipyridamole (DP) was infused intravenously for over 10 minutes at a total dose of 0.75 mg/kg. Simultaneous recording of ECG, PCG, and ICG were repeated immediately 2 minutes and 4 minutes after infusion of DP, and immediately and 5 minutes after intravenous infusion of aminophylline. Eleven parameters, HR, SPRP, QZ/ZA2, HI, SV, CO, A wave, A/C, O wave, O/C, A + O/C were observed. Only in O/C and A + O/C there were changes of significant differences (P less than 0.01) between groups. Specificity was 100% (0/11 positive) in normals. Sensitivity was 80% (12/15 positive) in the angina group, but only 46.7% (7/15) with ECG. The characteristic changes in CAD patients during IDT were angina induced by DP, abnormal O wave on ICG and change from deep A wave to abnormal O wave. No serious complication occurred after IDT. Our results indicate that IDT is a simple, practical and valuable method for detecting CAD.