Abstract
Purpose: Ventricular reserve is defined as the response of the ventricle to exercise or pharmacological stimulation. VR usually includes a change in stroke volume or ventricular elastance. In chronic right ventricular (RV) failure, impairment of VR had not been yet investigated. In an experimental model of pulmonary hypertension (PH) we studied non invasive parameters that could correlate with RV reserve alteration in order to be used in PH patients. Methods and Materials: Chronic PH was induced in pigs by ligation of the left pulmonary artery (PA) followed by weekly injections of n-butyl2-cyanoacrylate to progressively occlude right lower lobe arteries for 5 weeks (PH group, n 9). Those animals were compared to sham operated animals (n 9). Right heart catheterization to assess mean PA pressure (mPAP) and pulmonary vascular resistances (PVR), echocardiography to assess RV myocardial performance index (RVMPI), tricuspid annular plane systolic excursion (TAPSE) and isovolumic acceleration (IVA), and RV conductance catheterization to assess RV elastance without and with pharmacological stimulation using dobutamine (5 mcg.kg-1.min-2) were performed at baseline and 5 weeks. Results: At 5 weeks, mPAP (35 9 vs. 13 2 mmHg, p 0.001) and PVR (872 128 vs. 348 24 dynes.s.cm-5, p 0.012) increased in PH animals and remained unchanged in Sham group. Compared to controls, PH group had higher RVMPI (0.57 0.05 vs. 0.34 0.02, p 0.013), lower TAPSE (1.37 0.06 vs. 1.83 0.06 cm, p 0.001) and lower elastance in response to dobutamine (0.17 0.03 vs. 0.55 0.11 mmHg.ml-1, p 0.001). Right ventricular elastance response to dobutamine was positively correlated with TAPSE (r 0.811, p 0.002) and IVA changes (r 0.639, p 0.046) and inversely correlated with RVMPI changes (r 0.744, p 0.008). Conclusions: Ventricular reserve is early impaired in chronic PH and represents a sensitive marker of RV dysfunction. TAPSE, IVA and RVMPI are non invasive parameters that correlate with RV reserve impairment and may be used to predict RV dysfunction in PH patients.
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