MEDizzy - An 85-year-old former lawyer presents with several months of

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Disorders of the cardiovascular system 2

An 85-year-old former lawyer presents with several months of accelerating dyspnea on exertion and lower extremity edema. On examination, you note a laterally displaced point of maximal impulse (PMI) and an S4 gallop. She has a III/VI systolic murmur at the base radiating to the carotid arteries. A transthoracic echocardiogram reveals a left ventricular ejection fraction of 25% with global hypokinesis. The calculated aortic valve area is 0. 8cm2 and the mean gradient is 25 mmHg. What is the next most reasonable step to determine whether this patient would benefit from aortic valve replacement?

ExplanationThis patient has evidence of the clinical entity referred to as low-gradient, low-flow AS. Conceptually, the aortic valve area during systole is dependent on two factors: (1) aortic valve morphology (e.g., calcific AS with restricted leaflet motion), and (2) ventricular contractile force. Even a normal aortic valve will open very little if the ventricle contracts very weakly. In this patient’s case, the finding of a low calculated aortic valve area without a severely high gradient (severe is >40 mmHg) in the setting of reduced LV function defends the entity of low-gradient, low-flow AS. It is difficult to determine whether the valve area is low due to reason 1 or 2 during resting echocardiography. However, dobutamine stress will accomplish two goals. First, it will assess ventricular viability (the ability to increase stroke volume by 20%), which is shown to predict outcomes after aortic valve replacement. Second, and more importantly, as the ventricular contractility increases, it allows the clinician to differentiate between true, morphologic AS and the appearance of AS due to compromised ventricular function (termed pseudo-AS). Although the other options may aid in other facets of this patient’s management, none will allow the clinician to make this differentiation.