ECG-gated 99mTc single-photon emission CT for assessment of right ventricular structure and function -: Is the information provided similar to echocardiography?

Study objective: Te-99m single-photon emission CT (SPECT) and ECG-gated SPECT can visualize well the right ventricle (RV) in most patients, but their utility for assessment of the RV has not been formally evaluated. We examined whether Tc-99m SPECT/ECG-gated SPECT provide similar information to transthoracic two-dimensional Doppler echocardiography (2D-ECHO) regarding RV cavity size, wall thickness, and systolic function. Design: Retrospective analysis. Setting: A major university teaching hospital. Patients: A consecutive series of 194 patients with good quality stress SPECT and 2D-ECHO studies performed within I day of each other and no significant interim cardiac events. Measurements and results: RV size and function were visually assessed by SPECT/ECG-gated SPECT and 2D-ECHO. RV wall thickness was visually assessed by SPECT and measured in nun in end-diastole by 2D-ECHO. Of 142 patients with normal RV cavity size by SPECT, 134 patients (94%) had normal RV cavity size by 2D-ECHO. However, of 52 patients with RV dilation by SPECT, only 9 patients (17%) had RV dilation by 2D-ECHO. A perfusion abnormality in the right coronary artery territory was significantly associated with RV dilation by SPECT (p < 0.005) and 2D-ECHO (p < 0.05). Among 150 patients with ECG-gated SPECT, only 2 patients had abnormal RV systolic function, as compared with 18 patients by 2D-ECHO. RV wall thickness measurements by SPECT and 2D-ECHO did not correlate. Conclusions: For normal interpretations regarding RV cavity size, wall thickness, and systolic function, there is good agreement between Tc-99m stress SPECT/ECG-gated SPECT and 2D-ECHO. However, there is poor overall agreement between gated SPECT/ECG-gated SPECT and 2D-ECHO regarding the presence of RV dilation, hypertrophy, and systolic dysfunction.