Chapter 21 Marini Acute Coronary Syndromes

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SECTION II • Medical and Surgical Crises

vasopressors is necessary before and after surgery in most of these patients. In patients with STEMI presenting late (>12 to 24 hours) and in the need for CABG, it may be advisable to wait for a few days to a week before surgery, especially if they are not showing any signs of acute ischemia and are relatively stable hemodynamically. The sur- gical mortality in stabilized STEMI patients is lower than in those who undergo emergent sur- gery within the first 24 hours of infarction. • In patients needing emergent CABG, use of Gp2b/3a receptor antagonist and clopidogrel before surgery will increase risk of bleeding. These agents must be stopped as soon as the decision to operate on these patients is made. Cautious dosing of heparin based on ACT while going on bypass pump may also reduce the risk of bleeding in these patients, many of whom would have also received Gp2b/3a receptor antagonists. For patients who have received abciximab and/or clopidogrel, infusion of 6 to 12 units of platelets while coming off pump will serve to reduce post- operative bleeding. Medical Treatment after Reperfusion Therapy 1. Antiplatelet Therapy: Aspirin (81 to 162 mg/d) should be given indefinitely to all patients with history of MI or CAD. Clopidogrel is routinely given for all those who receive stents for a dura- tion of 6 to 12 months or longer. 2. Angiotensin-Converting Enzyme Inhibi- tors: ACEIs favorably influence ventricu- lar remodeling after AMI, thereby reducing the risk of dilated cardiomyopathy, CHF, and death. The benefits of ACEI therapy in post-MI patients have been shown in several large tri- als, including GISSI-3 and ISIS-4. The great- est benefits have been observed in patients at highest risk (e.g., patients with large anterior wall infarctions, patients who are older than 70 years of age, and women). Ideally, an oral ACEI is started within 48 hours of the onset of the infarction in those who have been sta- bilized. Intravenous dosing and use of “loading doses” are not only unnecessary but may prove harmful. Several examples of potential ACEI regimens are presented in Table 21-5. Con- traindications to ACE therapy include known hypersensitivity, cardiogenic shock, renal fail- ure, and bilateral renal artery stenosis. Renal insufficiency is not a contraindication for ACEI

Table 21-5.  ACEI Regimens Captopril  6.25 mg p.o., followed 2 hours later by  12.5 mg p.o., followed 12 hours later by  25 mg p.o., then  50 mg p.o. b.i.d Lisinopril  5 mg p.o. daily for 2 days, then  10 mg p.o. daily Enalapril  2.5 mg p.o. b.i.d. titrated upward to  10 mg p.o. b.i.d. as tolerated Ramipril  2.5 mg p.o. b.i.d. for 2 days, then  5 mg p.o. b.i.d

therapy, but one should monitor creatinine and potassium closely. In patients at low risk, there may not be any benefit beyond the first 3 to 6 months of an AMI. By contrast, high-risk patients (such as those with ejection fraction below 40%, overt heart failure, or clinical evi- dence of a large infarction) benefit from long- term (potentially permanent) therapy. As a mat- ter of practicality, virtually all tolerant patients with MI started on an ACEI continue the medication indefinitely. Large trials have failed to substantiate fears that ACEI could worsen outcome by precipitating hypotension. 3. Angiotensin II Receptor Blocker Antago- nists (e.g., alsartan or candesartan) often can be used instead of ACEI in post-AMI patients who are intolerant to ACEI and have LVEF less than 40% and/or CHF. 4. β -Blockers: When well tolerated, β -blockers reduce risk of recurrent MI and sudden death in patients with previous MI. They also may help prevent adverse LV remodeling after an MI (along with ACEI therapy) and risk of ven- tricular arrhythmias. Long-term β -blocker ther- apy, typically with either metoprolol or ateno- lol ( β 1 receptor antagonists), is recommended. Carvedilol is considered preferable for patients with severe LV dysfunction and heart fail- ure. In this patient population, this agent has been shown to significantly reduce mortality. Far more expensive than metoprolol or ateno- lol, carvedilol blocks β 1 -, β 2 -, and α -receptors and has also been shown to have antioxidant