Myocardial structure as a determinant of pre- and postoperative ventricular function and long-term prognosis after valve replacement for aortic stenosis.

BACKGROUND

Long-term results after aortic value replacement for aortic stenosis can be correlated to a cardiac-related pre-operative risk profile. This predictability indicates that there is a common basis in subtle or overt structural abnormalities of left ventricular myocardium.

METHODS AND RESULTS

Forty-nine patients aged 24-82 (mean 61) years, with aortic stenosis had a full wall thickness transmural biopsy of the left ventricular antero-lateral free wall during aortic valve replacement. Echocardiography and radionuclide ventriculography were performed prior to, and 18 months (n = 41) after, the operation. Postoperative follow-up to a maximum of 7.7 years was 100% complete. Pre-operatively, all patients had an increase in both the left ventricular mass index (202 +/- 67 g.m-2) and the muscle cell diameter (41 +/- 8 microns); other morphological data included a muscle cell nucleus volume of 752 +/- 192 microns3, a muscle cell mass index of 163 +/- 54.m-2, and a fibrous tissue mass index of 39 +/- 16 g.m-2. Patients with a pre-operative episode of clinical left ventricular failure (n = 19) had significantly greater morphological variables than those without. Pre-operative ejection fraction and other measures of systolic function correlated inversely with the morphological data, except for the fibrous tissue mass index; diastolic function indices correlated inversely with all the morphological variables. At the 18-month re-study, the same general picture was noted, but with an underlying strengthening, especially of the muscle cell mass index. Overall, the mass index dropped to 152 +/- 51 g.m-2 (P < 0.0001), but in 17% of the patients it became normal; the mass index at 18 months was directly correlated to morphological variables. A high muscle cell nucleus volume was identified as an independent predictor of early and late mortality.

CONCLUSIONS

Abnormalities of the hypertrophied left ventricular muscle cell and the degree of muscle hypertrophy are, to some degree, underlying determinants of pre-operative symptomatology, pre- and postoperative ventricular function, and early and late mortality after valve replacement for aortic stenosis. Incomplete hypertrophy impaired results, was related to pre-operative myocardial structural abnormalities.