MEDizzy - You are taking care of a 77-year-old patient with severe

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Disorders of the cardiovascular system 2

You are taking care of a 77-year-old patient with severe aortic stenosis in the cardiac intensive care unit. Surgical aortic valve replacement is planned for tomorrow. However, suddenly, he becomes severely short of breath and manifests signs of acute pulmonary edema. On auscultation, you can now appreciate a soft, short apical systolic murmur (in addition to his previously appreciated murmur of aortic stenosis) that was not present previously. You suspect that he has suffered a ruptured mitral valve chordae and now has severe, acute mitral regurgitation. Which of the following parameters will likely increase due to his new severe mitral regurgitation?

ExplanationThis patient is in a precarious situation and likely will require emergent surgical intervention to survive. The combination of severe obstruction to LV outflow (severe AS) and acute, severe regurgitant mitral valve disorder will inevitably lead to intractable pulmonary edema and cardiogenic shock unless both structural abnormalities are corrected. At the advent of severe mitral regurgitation, the LV will be more effectively “unloaded” because now it can eject not only against the stenosed aortic valve, but also into the relatively low-pressure left atrium, and thus afterload will decline. Likewise, with more of the stroke volume going ineffectively into the left atrium, the effective stroke volume (total stroke volume – regurgitant volume) will decline. The aortic valve gradient will decline merely because there is less volume going across the aortic valve with each contraction. Likewise, because both the catheter-derived and echocardiographic-derived calculations of the aortic valve area are dependent on the gradient for calculation, they will decline. Ejection fraction, however, will increase as the LV will be better able to contract in the state of relatively lower afterload. This highlights a misconception that a higher ejection fraction is always better. LV ejection fraction is highly dependent not only on the contractile state of the ventricle but also on its afterload state.