This new total right/left-volume index correlated with almost all clinically used biomarkers of heart failure : brain natriuretic peptide ( r = @ ; P = @ ) , QRS ( r = @ ; P = @ ) , peak oxygen consumption/kg ( r = -@ ; P = @ ) , ventilatory response to carbon dioxide production at anaerobic threshold ( r = @ ; P = @ ) , the severity of tricuspid regurgitation ( r = @ ; P = @ ) , tricuspid valve offset ( r = @ ; P = @ ) , and tricuspid annular plane systolic excursion ( r = @ ; P = @ ) .