Chapter 20. Acquired Cardiac Disease
Which of the following does not contribute to the susceptibility of coronary ischemia?
A. High baseline oxygen extraction
B. Coronary flow limited largely during diastole
C. Atherosclerosis that tends to occur diffusely in small coronary vessels
D. Increased myocardial oxygen demand, which requires proportional increase in coronary blood flow
The correct answer is C. Atherosclerosis tends to occur diffusely in small coronary vessels. Myocardial tissue extracts 70%-80% of arterial blood oxygen at rest, unlike other organs which can extract additional oxygen during periods of increased demand. The myocardium recruits additional blood flow by vasodilation and recruitment of an extensive capillary bed via a feedback mechanism from adenosine diphosphate and other byproducts of metabolism, increasing oxygen delivery to match consumption. Atherosclerosis, or the formation of intra-arterial cholesterol plaques, tends to occur in the more proximal and larger epicardial vessels, leaving the distal vasculature relatively unobstructed. This allows revascularization by either percutaneous or surgical techniques.
Which of the following is true about aortic stenosis?
A. Senile calcific aortic stenosis is associated with ascending aortic aneurysms.
B. Rheumatic heart disease affects the aortic valve most commonly, followed by the mitral and tricuspid valves.
C. Presence of left ventricular hypertrophy is an indication for surgery in patients with aortic stenosis.
D. Typical symptoms are exertional dyspnea, angina, or syncope.
The correct answer is D. Typical symptoms are exertional dyspnea, angina or syncope. Senile calcific aortic stenosis occurs in the eighth decade of life in patients with tricuspid (normal) aortic valves. While dilation of the ascending aorta is a normal part of the aging process, aneurysms of the ascending aorta are associated with bicuspid aortic valves, related to abnormalities in elastin fiber formation. Rheumatic heart disease affects the mitral valve most commonly. It is unusual for a patient with rheumatic heart disease to present with isolated aortic stenosis but not mitral valve disease, whereas the opposite is fairly common. Indications for surgery in aortic stenosis are the presence of symptoms, which are exercise intolerance, angina, syncope, and dyspnea.
For patients with mitral regurgitation, indications for mitral reconstruction do not include
A. Left ventricular dilation
C. Asymptomatic with a prolapsed anterior mitral leaflet
D. Moderate mitral regurgitation at the time of coronary bypass surgery