engleski

Does the aortic velocity profile in aortic stenosis patients reflect more than stenosis severity? The impact of myocardial fibrosis on aortic flow symmetry

Background: In severe aortic stenosis (AS), the gradient measured over a stenotic valve is indicative of stenosis severity, but often does not relate to a potential decrease in myocardial function. After initial hypertrophic remodeling of the left ventricle, myocardial fibrosis occurs leading to systolic dysfunction. We hypothesize a relation between the shape of the aortic outflow velocity profile and myocardial functional impairment due to fibrosis in AS. Methods: 34 patients undergoing aortic valve surgery for severe AS were studied by echocardiography pre- (PRE) and 9 months postoperatively (POST). 29 healthy volunteers served as controls. Semi-automated analysis was applied to aortic continuous wave velocity traces from which the asymmetry of the velocity profile (asymm) was quantified as the normalized difference of area under the curve of left and right half of the spectrum so that a lower asymm corresponded to more symmetrical, later peaking flow. Cardiac Magnetic Resonance imaging (CMR) including images for late enhancement (LE) diagnostics was performed preoperatively in 18 of the pts for the assessment of replacement fibrosis. Left ventricular myocardial biopsy specimens were acquired during aortic valve replacement surgery in 29 of the pts for the assessment of interstitial fibrosis. Results: Asymm PRE values ≥0.15 showed 95 % specificity and 100 % sensitivity in detecting patients with postoperative EF improvement, regardless of PG mean PRE. Signs of LE were demonstrated by CMR in 72% of the patients in which such a study was performed. The same percentage of patients showed signs of myocardial fibrosis in the biopsies, In the subgroup of patients with asymm PRE ≥ 0.15 (which all improved EF postoperatively), CMR LE was present in 50% of these patients. Conversely, in the subgroup of patients with asymm PRE < 0.15, CMR detected LE in 90.9% of these patients. Finally, after AVR, values of asymm had increased to ≥ 0.15 in all patients. Nevertheless, 10 patients retained asymm < 0.25. Preoperative CMR data were available in 6/10 patients and in all of them showed signs of LE detectable on CMR imaging. Conclusions: A symmetrical aortic outflow profile seems related to a reduction in left ventricular function as well as to replacement fibrosis as detected by CMR LE. Furthermore, it predicts functional recovery after surgery with high specificity and sensitivity. Semi-automated analysis provides additional clinical information on the functional impact of AS.

Aortic stenosis; myocardial fibrosis; Doppler echocardiography; Ventricular function; haemodinamics

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