[Secondary tricuspid insufficiency and right atrial myosin ATPase activity]

Myosin of heart muscle shows ATPase activity. In the atrial myocardium, normal isozymic pattern was alpha dominant which converted to being beta dominant in an overloaded hypertrophy. In order to clarify the distribution of myosin isozymes in human heart, ATPase activity of the atrial myosin recovered from the patient underwent open heart surgery was determined. In the present study, ATPase activity of right atrial myosin from the heart with tricuspid regurgitation (TR) (group A (n = 6); 398.1 +/- 67.0 nmol pi/mg/min) was significantly less than that from the heart without TR (group B (N = 7); 533.9 +/- 62.4, p less than 0.05). The myosin ATPase activity showed correlation with systemic RA pressure (y = 0.019x + 19.6, r = -0.68429), systemic RV pressure (y = 0.039x + 58.67, r = 0.73484), SVI (y = 0.05x + 18.1, r = 0.87587) and RV maxDp/Dt (y = 0.42x + 589.9, r = -0.67493) (p less than 0.05). These data suggests that preoperative cardiac function involves in cardiomuscular structure with redistribution of contractile protein.