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 tends to occur diffusely in small coronary vessels
D. Increased myocardial oxygen demand requires proportional increase in coronary blood flow
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
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
C. Asymptomatic with a prolapsed anterior mitral leaflet. Indications for surgery in patients with mitral regurgitation include heart failure symptoms, left ventricular dilation and reduced left ventricular systolic function. In asymptomatic patients without symptoms and normal ventricular function and size, surgery could be recommended if the likelihood of durable repair is high. Repair of posterior leaflet prolapse is much more common than in prolapse of the anterior leaflet. Mitral replacement would entail either a bioprosthetic with limited durability, or a mechanical valve and a lifelong requirement for anticoagulation. Moderate mitral regurgitation is typically addressed incidentally at the time of other cardiac surgery, including coronary bypass grafting or aortic valve replacement.
Which of the following is true of the thoracic aorta?
A. Fibrosis results in contraction of the ascending aorta with age
B. The ascending aorta should only be replaced when its maximum diameter exceeds 5.5 cm in the absence of symptoms
C. Stanford type B dissections cause early death from intrapericardial rupture, aortic valve insufficiency or coronary malperfusion
D. Malperfusion of the abdominal viscera can occur with either Stanford type A or type B aortic dissections
D. Malperfusion of the abdominal viscera can occur with either Stanford type A or type B aortic dissections. Due to gradual and progressive breakdown of elastin fibers, the ascending aorta dilates as part of the natural aging process. Indications for replacement of the ascending aorta include size of 5-5.5 cm in asymptomatic patients, 4.5 cm in patients with know Marfan syndrome, interval growth of 1 cm in 1 year, or 4.5 cm when incidental to other cardiac surgery including aortic valve replacement or coronary bypass grafting. Stanford type A dissections involve the ascending aorta, which can cause sudden death from intrapericardial rupture and tamponade, aortic valve insufficiency from prolapse, or coronary malperfusion and myocardial infarction. Stanford type B dissections are distal to the ascending aorta and thus not within the pericardial space and not directly adjacent to the aortic valve or coronary ostia. Malperfusion from an aortic dissection occurs when the intimal flap occludes any branch of the aorta causing ischemia. Both Stanford type A and B can cause malperfusion of the abdominal viscera, depending on the extent and geometry of the dissection.
Which of the following is true regarding advanced heart failure?
A. Beta-blockers improve survival in heart failure in part by up-regulation of beta-receptors
B. The incidence of heart failure is decreasing because of advances in medical treatment
C. The use of mechanical circulatory support does not affect priority status for heart transplantation
D. Left ventricular dysfunction is the most frequent early complication following heart transplantation
A. Beta-blockers improve survival in patients with advanced heart failure from a variety of proposed mechanisms, including up-regulation of beta-receptors in the myocardium. Heart failure incidence is increasing related to aging population and the rising incidence of diabetes as well as obesity. Deaths from coronary artery disease and myocardial infarctions are decreasing from improved medical care. Temporary mechanical circulatory support increases a heart transplant candidate to status 1A, while implantable mechanical circulatory support results in status 1B. Patients with chronic heart failure on oral medical treatment are status 2. Following heart transplantation, right ventricular dysfunction is the most frequent complication, as the donor’s untrained right ventricle is required to maintain circulation in a recipient with pulmonary hypertension, which is often present from long standing heart failure.