Effect of Concomitant Asymmetric Septal Hypertrophy when Assessing the Severity of Aortic Valve Stenosis: An In-Vitro Study

Background and aim of the study: Aortic valve stenosis (AS) is an important cardiovascular disease that affects between 2% and 7% of the elderly population in industrialized countries. AS often coexists with asymmetric septal hypertrophy (ASH), which is generally caused by a protrusion of the hypertrophied left ventricular outflow tract (LVOT) just below the aortic valve. The study aim was to determine, based on measurement of the aortic valve effective orifice area (EOA), if ASH might potentially interfere with the assessment of AS severity.
Methods: The effects of different levels of ASH (from normal to 90%) on the EOA measured from orifices
mimicking different AS severities, and from a homebuilt AS model constructed from a bioprosthetic aortic valve, were examined in a pulsatile flow in-vitro
model.

Results: For the most severe AS, the level of ASH had
no impact on the measured EOA. In contrast, for the
less severe AS, beyond an ASH level of 50% the AS
severity was progressively overestimated, and
reached a reduction of about 60% of EOA for a ASH
level of 90%.
Conclusion: The presence of concomitant ASH may
cause an overestimation of the hemodynamic severity
of AS. The extent of overestimation is more important
in less-severe AS. Hence, the presence of ASH
may lead the clinician to conclude, erroneously, that
the AS is severe and that aortic valve replacement is
indicated. However, beyond an ASH level of 50% the
AS severity can be accurately determined.

The Journal of Heart Valve Disease 2009;21:623-627