( This ( ( results ( in ( blood ( ( ( ( backing up ) ( in ( ( ( the ( left atrium ) ) and ) lungs ) ) ) , ) ( which ( ( in turn ) ( leads ( to ( symptoms ( of ( heart failure ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ results) (PP (IN in) (NP (NP (NN blood)) (VP (VBG backing) (PRT (RP up)) (PP (IN in) (NP (NP (DT the) (JJ left) (NN atrium)) (CC and) (NP (NNS lungs)))) (, ,) (SBAR (WHNP (WDT which)) (S (PP (IN in) (NP (NN turn))) (VP (VBZ leads) (PP (TO to) (NP (NP (NNS symptoms)) (PP (IN of) (NP (NN heart) (NN failure)))))))))))) (. .)))
This results in blood backing up in the left atrium and lungs, which in turn leads to symptoms of heart failure.
(ROOT (S (NP (NP (NNP Blood)) (PP (IN from) (NP (DT the) (NNS lungs)))) (VP (VBZ enters) (PP (IN into) (NP (DT the) (JJ left) (NN atrium)))) (. .)))