Right ventricular overloading evaluated by thallium-201 myocardial imaging in patients with chronic lung diseases

Recently the usefullness of thallium-201 myocardial imaging for the detection of right ventricular overloading is becoming widely accepted. To evaluate the correlation of (1) electrocardiogram and (2) arterial blood gas analysis with thallium myocardial imaging, we compared those findings in 21 patients with chronic lung disease. Visualization of the right ventricular free wall was observed in 10 cases but the extent of tracer activity was small. 1) We selected twelve electrocardiogram criteria for assessment of right ventricular overloading. Out of them, PII > 0.2 mV, QRS axis > 90, RV5(V6) < 0.5 mV, R/SV5(V6) < 1.0, transitional QRS leftward ≥ V5, V1qR and predominant SI are specific for visualization of the right ventricular wall by tracer. Thallium activity ration (TAR) tended to decrease with increasing numbers of criteria satisfied. 2) The right ventricles of patients showing PAO2 within 70 Torr or PaCO2 more than 45 Torr were all visualized by tracer. Patients with visualization of the right ventricular wall showed significantly lower PaO2, higher PaCO2 and larger AaDO2 than those without. Furthermore, TAR significantly correlated with PaO2 and PaCO2 (each r = 0.68 and r = -0.71). The above results suggest that PaCO2, as well as PaO2, closely correlated with right ventricular overloading. (author)