Background: Proto-oncogenes have been implicated in the pathogenesis of gene-mediated myocardial remodeling. In the human heart, however, it has not been clarified whether these proto-oncogenes are related to contractile impairment and structural alteration of the myocardium. The present study is designed to investigate the relationship between the c-Myc protein expression in the myocardium and the myocardial contractile dysfunction in patients with chronic aortic regurgitation who underwent indicated for aortic valve replacement.
Methods and results: Twelve patients (11 males and one female) with an average age of 55 years who underwent aortic valve replacement for isolated chronic aortic regurgitation were studied. The preoperative New York Heart Association class was II in four patients and III in eight. Ejection fraction, end-systolic volume index, end-systolic stress (Mirsky's form), and mass index of the left ventricle before surgery were 47+/-13%, 93+/-37 mL/m2, 223.2+/-44.4 Kdyn/cm2, and 210+/-38 g/m2, respectively. A left ventricular endomyocardial biopsy was performed to assess the myocardial cell diameter, fibrous content, and c-Myc protein expression in the myocardium. Cell diameter and fibrous content were significantly higher than those in five normal controls. C-Myc was detected in 9 of 12 present patients but in none of the normal controls. The degree of c-Myc expression had significant positive correlations with ejection fraction (r=0.93; P<.01) and end-systolic stress/end-systolic volume index (r=0.96; P<.01) and significant negative correlations with end-systolic volume index (r=-0.90; P<.01), cell diameter (r=-0.97; P<.01), and fibrous content (r=-0.92; P<.01), which suggested that the degree of c-Myc expression may have a significant negative correlation with myocardial contractility and myocardial hypertrophy.
Conclusions: C-Myc expression may be related to the pathogenesis of myocardial remodeling in patients with chronic aortic regurgitation.