Does Increased Valvulo-arterial Impedance Lead to Left Ventricular Hypertrophy and Myocardial Fibrosis in Severe Aortic Stenosis?

Abstract

Background: Valvulo-arterial impedance (Zva) is a composite marker of afterload, combining valvular gradient and arterial compliance and has prognostic significance in aortic stenosis (AS). Increased afterload in AS is associated with raised left ventricular mass index (LVMI) and ultimately myocardial fibrosis. We sought to investigate the relationship between increased Zva and LVMI and fibrosis in myocardial biopsies in AS. Methods: Thirty-eight patients, mean age 69 years (SD = 12.4), 50% females with severe AS underwent preoperative transthoracic echocardiograms (TTE) and intraoperative left ventricular (LV) myocardial biopsies during aortic valve replacement. LVMI and Zva were calculated on TTE (JACC 2005;46:291). Preoperative LV mass index (LVMI) and fibrosis on left ventricular myocardial biopsies were compared with ranges of Zva. Results: Using a Zva cut-off value of 4.5 mmHg/ml/m2 (range 2.4–7.8 mmHg/ml/m2) patients were grouped into a high Zva (31.6%, n = 12) or low Zva (68.4%, n = 26) cohort. Mean LVMI in the low and high Zva cohort were 141.6 g/m2 (SD = 6.9) and 148.2 g/m2 (SD = 10.8) respectively, with no significant difference (p = 0.6). The cohort with the low Zva had a lower incidence of myocardial fibrosis 30.7% (n = 8) compared with 58% (n = 7) amongst the high Zva group. Whilst a clear trend of a higher incidence of myocardial fibrosis in patients with higher Zva was noted the difference did not reach statistical significance (p = 0.1). Conclusions: LV hypertrophy did not correlate with high or low Zva. However, a trend towards increased prevalence of myocardial fibrosis in the cohort with higher Zva was found.