AN IN VITRO CONTRACTILE STUDY IN PEDIATRIC HUMAN HEARTS WITH CONGENITAL HEART DISEASE

Abstract

Contractile compensatory mechanisms exploited in mature (older pediatric or adult) hearts may not be developed in younger pediatric hearts. With congenital heart disease (CHD), these patients are dependent on treatments specific to their cellular maturity. We hypothesized that younger CHD hearts may not comply with the contractile phenotype (ex: + force/frequency relationship (FFR), low resting tension (RT): developed tension (DT) ratio, and post-rest potentiation (PRP)) associated with mature cardiac function. We used tissue from pediatric hearts undergoing surgery; 24 with CHD and 7 with heart failure (HF), age ranged from 2mon-12yrs. Baseline contractility and FFR were assessed. In addition, PRP experiments were performed to measure sarcoplasmic reticulum (SR) function. Positive FFR was evident between 0.5-1.5Hz. DT and DT rate was lower in CHD vs HF pediatric hearts. RT was about 3x the DT in CHD vs <2x the DT in published adult human heart data. There was an absence of the PRP response in younger CHD (n=10; age 0.3-1.5yrs) vs older HF hearts (n=6; age 1.5-12yrs). A significantly lower DT, higher RT/DT ratio, and the absence of a PRP response suggest that these muscles may not be as dependent on SR function as older pediatric and adult hearts. Hence these data supports the need for more studies using younger patients where contractile regulation needs further elucidation.