The relationship between functional capacity and ultrasonic tissue characterization in patients with idiopathic dilated cardiomyopathy

Abstract

Background: Ultrasonic tissue characterization (UTC) has been widely used to investigate left ventricular (LV) dysfunction in various cardiac disorders. The aim of this study was to investigate the correlation between functional capacity and UTC in patients with idiopathic dilated cardiomyopathy (IDCM). Methods and Results: Treadmill test according to modified-Bruce protocol was performed in 48 patients with IDCM to assess their functional capacity. Baseline clinical and echocardiographic variables were obtained and UTC was performed on images obtained from septum and posterior wall (PW). Cyclic variation (CV) index of mean gray level (MGL) was calculated according to the formula: [(MGLdiastole - MGLsystole) ÷ MGLdiastole] × 100. PW and septum CV indices were correlated with exercise duration (r = 0.63, p = 0.001 and r = 0.67, p = 0.0001, respectively) and "MET" level (r = 0.80, p = 0.0001 and r = 0.83, p = 0.0001, respectively). The ROC curve analysis revealed that the PW CV index was a strong indicator of good exercise capacity (> 8 METs) with an AUC of 0.97 (95% CI 0.90-1.0), as the interventricular septum (IVS) CV index (AUC = 0.97, 95% CI 0.89-1.0). Sensitivity, specificity, positive predictive value, and negative predictive value to identify good exercise capacity for IVS CV index were 90%, 88%, 82%, and 94%, respectively and for the PW CV index, 90%, 88%, 82%, and 94%, respectively. Conclusions: In this particular study, we found out that in patients with severe LV dysfunction good exercise capacity was related to septum and PW CV indices measured by UTC, and these indices may be used as an indirect prognostic marker in heart failure. © 2013 Via Medica.