How Does the Heart Respond to Aortic Stenosis
Let Me Count the Ways
Another Chapter in the Complex Vagaries of Aortic Stenosis
Barone-Rochette et al,1 in this issue of Circulation: Cardiovascular Imaging, have provided us with an elegant study comparing pertinent echocardiographic measurements in patients with aortic stenosis (AS) with cardiac MRI measurements of similar parameters in the same patients. Reassuringly, they found that aortic flow measured by the 2 techniques was in good agreement, that anatomic aortic valve area (AVA) was slightly larger than physiological area as has been predicted in the past,2 and they shed new light on the patient with low flow, low gradient normal ejection fraction (EF) AS.
Article see p 1009
There are 3 ways that a patient with a normal EF can have reduced aortic flow: (1) end-diastolic volume is reduced; (2) there is mitral regurgitation; and (3) small nonstatistically significant differences in the components of aortic flow add up to major differences in stroke volume. Thus, a patient with an end-diastolic volume of 120 cc, an EF of 0.63, and no mitral regurgitation has a stroke volume of 75.6 cc, whereas a patient with an end-diastolic volume of 118 cc, an EF of 0.60, and a regurgitant fraction of 0.09 has a forward aortic stroke volume of 64.4 cc, a 15% reduction. Accordingly, patients in the current study with low flow and high gradient seemed to have more mitral regurgitation than other groups because stroke volume determined volumetrically was substantially more than aortic flow.
Patients with low flow and low gradient had a clinically significant but statistically insignificant 10% reduction in end-diastolic volume compared with the high flow groups and they also had the lowest EF of all groups in the study but still normal at 0.60. Of interest is their finding that in this group the mass:volume ratio was not excessively high in contrast to other reports.3–5 Thus, …