Abnormal interventricular septal displacement reflects increased oxidative metabolism in right ventricular free wall but not interventricular septum in patients with pulmonary hypertension using C-11 acetate PET

Objectives Abnormal interventricular septum displacement toward left ventricle (LV) reflects right ventricle (RV) volume or pressure overload. However, the association between this change in shape and myocardial physiological condition has not been studied. The aim of the study was to evaluate oxidative metabolism in RV free wall and interventricular septum in patients with pulmonary hypertension (PH) who had abnormal interventricular septum displacement using 11C-acetate PET.

Methods 26 patients with WHO functional class II to III PH [mean PAP 38.0±9.7 mmHg, pulmonary vascular resistance (PVR) 584.6±232.1] and 8 controls prospectively underwent C-11acetate PET. An eccentricity index, which reflects abnormal interventricular septum displacement, was obtained by echocardiography. C-11 acetate PET was used to simultaneously measure oxidative metabolism (kmono) for LV and RV.

Results The diastolic eccentricity index (DEI) was higher in patients with PH compared to control (1.26±0.22 vs 1.0±0.01, P<0.001). DEI was correlated with PVR (R=0.71, P<0.01) and RV free wall kmono (R=0.45, P=0.02). However, DEI was not correlated with interventricular septum (R=0.23) or LV lateral wall kmono (R=0.08). PH patients showed higher RV free wall/LV free wall oxidative metabolism ratio (83.6±12.1% vs 60.5±16.4%, P<0.01). However, there was no difference in LV interventricular septum/LV lateral wall kmono ratio (100.25.6% vs 99.43.0%, P=0.57).

Conclusions Abnormal interventricular septum displacement toward left ventricle is associated with increasing pulmonary vascular resistance and increased oxidative metabolism in RV free wall but not interventricular septum. This echocardiographic index might be useful in predicting elevated oxygen consumption in RV free wall