MOC Questions

Cardiology Review® Online, August 2006, Volume 23, Issue 8

The following cardiology-focused cases and questions should assist in fostering the continuing scholarship required for professional excellence in the practice of medicine. This section appears every other month; we hope you find it useful.

Preparing for the American Board of Internal Medicine Maintenance of Certification

Questions

1. All of the following outcomes have been shown to be significantly decreased as a result of tight glycemic control in coronary artery bypass graft (CABG) patients with diabetes, EXCEPT:a) short-term mortality.

b) long-term mortality.

c) deep sternal wound infections.

d) hospital length of stay.

e) strokes and neurological complications.

f) all of the above.

g) none of the above.

2. In patients undergoing CABG surgery: a) glomerular filtration rate (GFR) is a more accurate indicator of postoperative mortality than serum creatinine.

b) GFR < 60 mL/min per 1.73 m2 is an independent predictor of operative mortality.

c) perioperative hemodialysis decreases mortality.

d) all of the above.

e) none of the above.

f) a & b.

g) b & c.

3. Therapeutic agents with Class I recommendations to reduce recurrent ischemic events following CABG surgery include all of the following, except: a) angiotensin-converting enzyme (ACE) inhibitors.

b) beta blockers.

c) aspirin.

d) statins.

e) calcium channel blockers.

4. Which of the following are contraindications for the use of the radial artery as a conduit for CABG surgery? a) diabetes mellitus.

b) revascularization of a 60% obtuse marginal lesion.

c) positive Allen’s test.

d) revascularization of a 90% posterior descending artery lesion.

e) intolerance to oral nitrates.

f) all of the above.

g) none of the above.

h) a, c, & e.

i) b & c.

5. All of the following statements regarding the benefits and risks of oral platelet agents and heparin therapy prior to CABG are correct, EXCEPT: a) preoperative aspirin use in CABG patients reduces the risk of perioperative myocardial infarction (MI) and in-hospital mortality.

b) aspirin should be discontinued prior to CABG because of the increased risk of postoperative bleeding.

c) patients receiving clopidogrel within 5 days of CABG have an increased incidence of morbidity and mortality.

d) low-molecular-weight heparin given within 48 hours prior to CABG increases postoperative bleeding and transfusion requirements.

6. A 65-year-old male with diabetes is admitted to the hospital with an acute transmural MI. Cardiac catheterization shows a 100% occlusion of the mid-circumflex artery with left-to-left collateral flow of a second obtuse marginal branch, a 70% distal right coronary lesion, and an 80% proximal left anterior descending coronary artery lesion. His ejection fraction is 30% with 1+ mitral regurgitation and severe hypokinesis of the posterior lateral wall. An attempt was made to open the circumflex artery, thought to be the culprit lesion, but this was unsuccessful. He is now pain free. A decision is made to proceed with CABG surgery. Which of the following approaches would result in the least chance for a 30-day mortality? a) proceed with an emergent CABG.

b) insert an intra-aortic balloon pump and proceed directly with CABG.

c) in the absence of ischemia, proceed with CABG following a 3-day waiting period.

d) in the absence of ischemia, proceed with CABG after a 4-week waiting period.

7. A 47-year-old man with past medical history significant for Hodgkin’s lymphoma treated with radiation therapy presents complaining of worsening shortness of breath, dyspnea on exertion, and lower extremity edema. His physical exam is significant for an elevated jugular venous pressure that does not decline with inspiration, tachycardia, an early third heart sound, bibasilar rales, and bilateral lower-extremity edema. A lateral chest x-ray reveals pericardial calcifications. What is the treatment of choice? a) diuretics.

b) corticosteroids.

c) nonsteroidal anti-inflammatory drugs (NSAIDs).

d) pericardiectomy.

e) pericardiocentesis.

a) If this patient develops a narrow-complex tachycardia, any atrioventricular (AV) nodal blocker can be safely used for acute treatment.

b) Recent data suggest that even asymptomatic patients may benefit from prophylactic accessory pathway ablation to prevent life-threatening tachyarrhythmias.

c) The short PR interval is caused by preexcitation of the ventricles.

d) If this patient develops a wide-complex tachycardia, verapamil is the drug of choice for acute termination.

e) The accessory fibers are quick-conducting fibers.

9. All the following about aortic stenosis (AS) are true EXCEPT: a) Aortic stenosis is the most common adult cardiac valve lesion.

b) The earlier the murmur peaks in systole the more critical the stenosis.

c) If left untreated, one half of all patients who present with syncope due to AS will die in 3 years.

d) Stress echocardiography has been proven safe and useful for patients with moderate-to-severe asymptomatic AS.

e) Patients with moderate AS (valve area less than 1.2 cm2) undergoing CABG should have their valve replaced at the same time.

10. Based on the 2002 American College of Cardiology/American Heart Association guidelines for perioperative cardiovascular evaluation for noncardiac surgery, all the following are true, EXCEPT: a) A patient with diabetes and poor functional capacity (< 4 Metabolic Equivalent) should undergo non&shy;invasive cardiac evaluation if not done within the last 5 years.

b) All emergent surgeries should be done without cardiac evaluation regardless of cardiac history.

c) For anyone who has had coronary revascularization within the last 5 years, surgery can proceed if the patient is asymptomatic regardless of other clinical predictors.

d) All vascular disease surgeries are considered high risk.

e) Diabetes, history of stroke, and uncontrolled systemic hypertension are intermediate clinical predictors of increased perioperative cardiovascular risk.

1: e

There are now several studies that show that tight glycemic control improves outcomes in CABG patients with diabetes. Furnary and colleagues demonstrated improved 30-day mortality with insulin infusions; Lazar et al showed improved 3-year survival in patients receiving low-dose glucose-insulin-potassium (GIK) solutions. Both studies showed significant decreases in deep sternal wound infections. Lazar et al also showed that GIK decreased the incidence of atrial fibrillation, the need for inotropic support, and hospital length of stay. However, no series to date has demonstrated a lower incidence of neurologic complications in CABG patients with or without diabetes treated with tight glycemic control.

Answers

Furnary AP, Gao G, Grukeimeir GL, et al. Continuous insulin infusion reduces mortality in patients with diabetes undergoing coronary artery bypass grafting. J Thorac Cardiovasc Surg. 2003;125:1007-1021.

Lazar HL, Chipkin SR, Fitzgerald CA, et al. Tight glycemic control in diabetic coronary artery bypass graft patients improves perioperative outcomes and decreases recurrent ischemic events. Circulation. 2004;109:1497-1502.

Lazar HL, Chipkin SR, Fitzgerald CA, et al. Tight glycemic control in diabetic coronary artery bypass graft patients improves perioperative outcomes and decreases recurrent ischemic events. Circulation. 2004;109:1497-1502.

2: fStudies by Hillis and Cooper and their colleagues have identified GFR as an independent predictor of operative mortality following CABG surgery irrespective of serum creatinine. A GFR < 60 mL/min per 1.73 m2 is associated with increased mortality. These studies suggest that GFR and not serum creatinine should be used to determine perioperative risk in CABG patients.

Hillis GS, Croal BL, Buchan KG, et al. Renal function and outcome from coronary artery bypass grafting. Circulation. 2006;113:1056-1062.

Cooper WA, O’Brien SM, Thourani VH, et al. Impact of renal dysfunction on outcomes of coronary artery bypass surgery. Circulation. 2006;113:1063-1070.

3: e

Class I recommendations for therapy include those conditions for which there is evidence and/or general agreement that a given procedure or treatment is beneficial, useful, and effective. The level of evidence may be A) data derived from multiple randomized clinical trials or meta-analysis; B) data derived from a single, randomized trial, or nonrandomized studies; or C) only consensus opinion of experts, case studies, or standard of care. The current Class I interventions for post-CABG patients and their level of evidence include: antiplatelet therapy (IA), ACE inhibitors (IA), statins (IA), beta blockers (IB), smoking cessation (IB), exercise (IB), cardiac rehabilitation (IB), and emotional and psychosocial therapy (IB).

Arora R, Sowers JR, Saunders E, Probstfield J, Lazar HL. Cardioprotective strategies to improve long-term outcomes following coronary artery bypass surgery. J Card Surg. 2006;21:198-204.

4: i

The radial artery has emerged as another potential arterial conduit for use during CABG surgery. Although its patency is less than that for the internal mammary artery, it is equal or, in some series, superior to that of the saphenous vein after 1 year. To obtain optimal patency, it should only be used to bypass smaller (<2 mm) vessels with > 80% stenoses. Patients with a positive Allen’s test should not have the radial artery harvested from that extremity. Calcified radial arteries make poor conduits and should be avoided, if possible. Although calcified vessels are more likely to be found in patients with diabetes, the presence of diabetes is not a contraindication to the use of the radial artery, if the vessel is disease free. While it is recommended that patients receiving a radial artery remain on an antispasmodic agent for 1 year, patients intolerant of oral nitrates can be treated with calcium channel antagonists.

Mussa S, Choudhary BP, Taggart DP. Radial artery conduits for coronary artery bypass grafting: current perspective. J Thorac Cardiovasc Surg. 2005;129:250-253.

Buxton BF, Raman JS, Rvengsakulrach P, et al. Radial artery patency and clinical outcomes: 5-year interim results of a randomized trial. J Thoracic Cardiovasc Surg. 2003;125:1363-1371.

Tatoulis J, Royse AG, Buxton BF, et al. The radial artery in coronary surgery: a 5-year experience—clinical and angiographic results. Ann Thorac Surg. 2002;143:143-147.

5: b

The current guidelines regarding aspirin, clopidogrel, and low-molecular-weight heparin are as follows: Aspirin should be given up to the time of CABG and not be discontinued, since it has been shown to decrease cardiac ischemic events and postoperative mortality; especially in patients with acute coronary syndromes and recent MIs. The increased mediastinal drainage that is sometimes seen in these patients is not enough to result in increased blood product utilization. Clopidogrel should be discontinued for at least 5 days prior to CABG if possible. Clopidogrel has been associated with an increased requirement for blood products in all studies, and an increased incidence of mortality by Ascione and colleagues. If patients must undergo CABG while on clopidogrel for urgent or emergent reasons, patients should receive platelet transfusions (10-20 units) following discontinuation of cardiopulmonary bypass. Low-molecular-weight heparin increases bleeding when given within 48 hours of CABG and, therefore, should be stopped immediately and the patient placed on unfractionated heparin as soon as the decision is made to proceed with CABG surgery.

Ascione R, Ghosh A, Rogers CA, et al. In-hospital patients exposed to clopidogrel before coronary artery bypass graft surgery: a word of caution. Ann Thorac Surg. 2005;79:1210-1216.

Bybee KN, Powell BD, Valeta V, et al. Preoperative aspirin therapy is associated with improved postoperative outcomes in patients undergoing coronary artery bypass grafting. Circulation. 2005;112(9 suppl):I286-I292.

Cannon CP, Mehta SR, Aranki SF. Balancing the benefit and risk of oral antiplatelet agents in coronary artery bypass surgery. Ann Thorac Surg. 2005;80:768-779.

Ferraris VA, Ferraris SP, Moliterno DJ, et al. The Society of Thoracic Surgeons Practice Guideline Series: aspirin and other antiplatelet agents during operative coronary revascularization. Ann Thorac Surg. 2005;79:1454-1461.

6: c

The appropriate timing for surgical intervention following an acute transmural MI has long been a subject of intense debate. It is generally agreed that immediate surgery is associated with the highest mortality. However, it is unclear how long one can safely wait before proceeding with surgery. All patients experiencing post-MI angina should undergo urgent CABG since mortality from reinfarction is significantly increased in the absence of revascularization. Recently, Lee and colleagues studied the optimal timing for surgical revascularization after an acute transmural MI in 32,099 patients from the New York State Database. They found that revascularization within 3 days of an acute transmural MI was an independent predictor of 30-day mortality. In the absence of recurrent or ongoing ischemia, a 3-day waiting period prior to CABG significantly reduces mortality. Waiting longer than 3 days resulted in no further significant decrease in operative deaths. In fact, waiting longer periods of time in patients with 3-vessel disease and reduced ejection fractions may result in further ischemic events that will ultimately increase operative mortality.

Lee DC, Oz MI, Weinberg AD, Ting W. Appropriate timing of surgical intervention after transmural acute myocardial infarction. J Thorac Cardiovasc Surg. 2003;125:115-120.

7: d

In constrictive pericarditis, the normally elastic pericardium undergoes scarring and becomes stiff and noncompliant. This loss of compliance leads to restriction of cardiac filling, and may lead to signs and symptoms suggestive of congestive heart failure, such as dyspnea, tachycardia, an elevated venous pressure, pleural effusions, and edema. Some specific findings that may also be found include Kussmaul’s sign, a pericardial knock, and pericardial calcifications best seen on a lateral chest x-ray. Kussmaul’s sign, a paradoxical rise in the jugular venous pressure with inspiration, occurs secondary to resistance to right atrial filling. Most cases of constrictive pericarditis are of unknown etiology, although there are many known causes. Of the known causes, the most common are infections, history of cardiac surgery, and as in this patient, a history of therapeutic mediastinal irradiation. Echocardiogram and hemodynamic monitoring are essential for management of these patients. The treatment of choice for chronic constrictive pericarditis is pericardiectomy, although long-term survival remains disappointing, especially for patients with radiation-induced constriction. In a 1999 Circulation article, the 5- and 10-year survival rate was 78% and 57%, respectively. Diuretics can be used for symptom control, but must be used cautiously, with a goal of reducing central venous pressure only mildly.

Ling LH, Oh JK, Schaff HV, et al. Constrictive pericarditis in the modern era. Evolving clinical spectrum and impact on outcome after pericardiectomy. Circulation. 1999;100:1380-1386.

8: d

The EKG shows the classic short PR interval and a slow upstroking delta wave (arrow) seen with Wolff-Parkinson-White (WPW), also termed the preexcitation syndrome. In WPW, a fast-conducting accessory pathway (classically termed the Bundle of Kent) between the atria and the ventricles allows for conduction to bypass the slower AV node and thereby cause preexcitation of the ventricles. Patients with WPW often present with life-threatening tachyarrhythmias. Two of the tachyarrhythmias involve a reentry loop between the atria and the ventricles with conduction occurring over the accessory pathway and the AV node; these are termed atrioventricular reentrant tachycardia (AVRT) or reciprocating tachycardia. If the tachycardia is narrow complex, then the antegrade conduction runs through the AV node, and the retrograde conduction is through the accessory pathway. This is termed orthodromic AVRT. Acute treatment of orthodromic AVRT is aimed at slowing AV nodal conduction and therefore disrupting the reentrant loop. Therefore, vagal maneuvers and AV nodal blockers such as verapamil can be safely used. If the tachycardia is wide complex, then the antegrade conduction is over the accessory pathway and the retrograde conduction is through the AV node. This is termed antidromic AVRT. In this situation, AV nodal blockers, such as verapamil, may precipitate life-threatening preexcited atrial fibrillation that can degenerate into ventricular fibrillation, and therefore should be avoided. If the patient is hemodynamically stable, procainamide is the treatment of choice. A 2003 New England Journal of Medicine article showed for the first time that some high-risk asymptomatic patients with WPW benefited from prophylactic radiofrequency ablation of their accessory pathway.

Olgin JE, Zipes DP. Preexcitation syndrome. In: Braunwald E, Zipes DP, Libby P, eds. Heart Disease: A Textbook of Cardiovascular Medicine. 6th ed. Philadelphia, Pa: Elsevier Saunders; 2001:845-855.

Pappone C, et al. A randomized study of prophylactic catheter ablation in asymptomatic patients with the Wolff-Parkinson-White syndrome. N Engl J Med. 2003;349:1803-1811.

9: b

Aortic stenosis is the most common cardiac valvular disorder secondary to the high rate of congenital bicuspid aortic valves as well as the aging of the general population. The murmur of AS is described as a crescendo-decrescendo systolic murmur best heard at the upper right sternal border radiating to the carotids. As the valve area decreases from the normal 3-4 cm2 to the critical 1 cm2, the mean pressure gradient increases exponentially. This increase in the pressure gradient causes the peak of the murmur to occur later in systole often accompanied by a soft S2. An early or mid-peaking murmur usually signifies noncritical AS. Aortic valve replacement is the only treatment for severe, symptomatic AS. The risk of surgery must be weighed against the risk of delay. Of the 35% of patients with AS who present with angina, 50% will die within 5 years if the valve is left unreplaced. Of the 15% who present with syncope, 50% will die within 3 years. And, of the 50% who present with dyspnea secondary to heart failure, 50% will die within 2 years. Therefore it is imperative to replace all critical valves in symptomatic patients if possible. Stress echocardiography is contraindicated in patients with severe or symptomatic AS. But in patients with moderate-to-severe asymptomatic AS, stress echocardiography can help to identify patients at increased risk who would benefit from early valve replacement. All patients who are scheduled for CABG should be evaluated for AS, and concomitant aortic valve replacement should be performed if present, even if the valve area is not yet critical.

Carabello BA. Clinical practice: aortic stenosis. N Engl J Med. 2002;346:677-682.

10: e

In 2002 the ACA/AHA released updated guidelines for the perioperative cardiovascular evaluation for noncardiac surgery. These guidelines have provided a concise algorithm that is easy to follow, based on surgery-specific risk, numerous clinical predictors, functional capacity, and results of previous cardiac evaluation. Based on the algorithm, a patient with diabetes, an intermediate clinical predictor, and poor functional capacity should undergo noninvasive coronary evaluation if not previously performed. Any patient who has had coronary revascularization within the last 5 years and is without signs or symptoms of recurrent disease may proceed to surgery regardless of any other clinical predictors, functional capacity, or type of surgery. Diabetes is an intermediate clinical predictor, but both history of stroke and uncontrolled systemic hypertension are both minor predictors. High-risk surgical procedures include vascular surgeries, emergent surgeries, and intrathoracic or intraperitoneal surgeries.

Eagle KA, Berger PB, Calkins H, et al. ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery—executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). J Am Coll Cardiol. 2002;39(3):542-553.