This new total right/left-volume index correlated with almost all clinically used biomarkers of heart failure : brain natriuretic peptide ( r = 0.691 ; P = 0.0003 ) , QRS ( r = 0.432 ; P = 0.039 ) , peak oxygen consumption/kg ( r = -0.479 ; P = 0.024 ) , ventilatory response to carbon dioxide production at anaerobic threshold ( r = 0.426 ; P = 0.048 ) , the severity of tricuspid regurgitation ( r = 0.692 ; P = 0.009 ) , tricuspid valve offset ( r = 0.583 ; P = 0.004 ) , and tricuspid annular plane systolic excursion ( r = 0.554 ; P = 0.006 ) .