NMS. Casos Clínicos

18

Part I ♦ Foundations

Case Variation 1.6.7. The patient had a coronary artery bypass graft (CABG) 2 years ago. ◆ ◆ Prior coronary artery revascularization may reduce the risk of cardiac complications in patients who are undergoing other surgery. This may be especially true for patients who had the cardiac surgery 6 months to 5 years and who have no symptoms of ischemia with physical activity. In part, this effect may result from the increased use of internal mammary arterial grafts in the past decade. Case Variation 1.6.8. The patient had a CABG 10 years ago. ◆ ◆ The benefit of CABG is less clear in patients who have had a coronary revascularization procedure more than 5 years prior. With saphenous vein bypass, the graft occlusion rates are 15% at 1 year after CABG, 25% at 5 years, and 45% at 10 years. A stress test should be performed to determine whether this patient has reversible ischemia. Case Variation 1.6.9. The patient had a percutaneous transluminal coronary angioplasty (PTCA) 2 years ago. ◆ ◆ The incidence of coronary restenosis after PTCA is 25%–35% at 6 months, so a cardiac evaluation with a stress test would be recommended. Case Variation 1.6.10. The patient had a PTCA 2 days ago. ◆ ◆ Noncardiac surgery should probably be delayed for several weeks following coronary angioplasty , if feasible, because the risk of coronary thrombosis is increased during the first month postsurgery. The recent PTCA may induce a procoagulant state that might be detri- mental to a fresh arterial intervention. The presence of a drug-eluting stent may require an antiplatelet drug, which can affect coagulation during surgery. Case Variation 1.6.11. The patient has angina on moderate exertion and uses nitroglycerin. ◆ ◆ Because this patient displays evidence of coronary artery disease, coronary angiography would be appropriate to determine the extent of disease and whether PTCA or coronary artery revascularization is indicated. Case Variation 1.6.12. The patient’s ECG shows six premature ventricular contractions (PVCs) per minute. ◆ ◆ Early studies by Goldman and coworkers in the 1970s showed that preoperative ECGs with more than five PVCs per minute were associated with increased cardiac mortality. Later studies reported that these findings do not necessarily indicate a high likelihood of intraop- erative or postoperative ventricular tachycardia. More likely, the cardiac risk of arrhythmia is related to underlying ventricular dysfunction . A stress test and an echocardiogram to evaluate left ventricular function and check for underlying cardiac disease would be appro- priate. Prophylactic antiarrhythmic therapy has not proved beneficial. Case Variation 1.6.13. The patient’s ECG indicates atrial fibrillation. ◆ ◆ If patients have no previous diagnosis of atrial fibrillation, an underlying cause such as coronary artery disease, CHF, or valvular heart disease must be sought. Heart rate must be well controlled, and therapy may involve cardioversion to normal sinus rhythm or beta-blockers to control heart rate. Both cardioversion and chronic atrial fibrillation may require anticoagulation to minimize the risk of embolization. Therapeutic decisions must be made in conjunction with a cardiologist and the surgery planned around them. Oral anticoagulants may also need to be used postoperatively. SAMPLE