Cause:Atherosclerotic (85%) including spasm (Nejm 1983;309:220) with superimposed thrombus in 90% of those; emboli (15%—Ann IM 1978;88:155); and now occasionally cocaine-induced spasm when used as anesthesia or as recreational drug (Nejm 1989;321:1557)
Pathophys:Platelet aggregations and thrombi (Nejm 1990;322:1549) on plaque fissures cause thrombosis with or without spasm (Nejm 1991;324:688; 1984;310:1137); or paradoxical vasoconstriction w stress because plaque prevents normal endothelial cell induction of coronary dilatation (Nejm 1991;325:1551)
Increased incidence with h/o:
- Concurrent BCP use incr risk × 2 (Nejm 2001;345:1787)
- Carbon monoxide acute exposures, eg, firefighters; and chronic CS2 exposures, eg, disulfiram (Antabuse) use, rayon manufacturing
- Cholesterol elevations of total and/or LDL, often with presence of an arcus senilis (Nejm 1974;291:1382)
- Cocaine use or withdrawal (Ann IM 1989;111:876; Nejm 1986;315:1438, 1495)
- Coffee, high decaffeinated but not regular coffee intake (Nejm 1990;323:1026); later study finds no incr incidence w either (Jama 1996;275:458)
- Exercise test showing ischemia (Nejm 1983;309:1085)
- Family h/o MIs prematurely (age <55 or 65 yr) (Nejm 1994;330:1041)
- Homocysteine levels >15 µM/L correlate w worse prognosis (Nejm 1997;337:230)
- Hypertension
- Menopause if surgical and patients not placed on estrogen; but no sharp increase in natural menopause
- Sedentary work; in longshoremen, MIs but not CVAs increased, thus not a general ASCVD effect (Nejm 1975;292:545)
- Sexual activity incr risk slightly but not at all if regular, eg 3 ×/wk exercise (Jama 1996;275:1405)
- Smoking increases risk × 3, but risk decreases to normal over 2 yr after stop (Nejm 1985;313:1511), increases risk × 5 if >1 ppd, × 2 if 1-4 cigarettes qd in women (Nejm 1987;317:1303)
- Stress, day to day (Jama 1997;277:1521) but not type A personality? (Nejm 1988;318:65, 110)
- Viral URI in past 2 wk (Ann IM 1985;102:699), or chronicChlamydia pneumoniaeinfections? (Ann IM 1996;125:979, 1992;116:273)
Abdominal adiposity (“Pear shape”) not an independent risk factor (Lancet 2011; 10.1016/S0140-6736(11)60105-0)
Decreased incidence with: exercise, >6 METS >2 h/wk divided tiw-qiw (Nejm 1994;330:1549); fish intake 1-4/mo (Jama 1995;274:1363; Nejm 1995;332:977; 1985;312:1205, 1254); 1-3 alcoholic drinks qd (Nejm 2003;348:109; Ann IM 1991;114:967) in men, vs 2-3/wk in women (Nejm 1995;332:1246); better control of hypertension, cholesterol, etc, in US (Nejm 1985;312:1005, 1053)
Sx: Chest pain (Table 2.2), substernal, in "distribution of a tree," worse supine; diaphoresis, dyspnea; associated with heavy exertion 5-40 × more frequently depending on conditioning state (Nejm 1984;311:874); CNS sx are the presenting sx in 50% of patients over age 60 yr. No recognizable sx ("silent") in ±25%, (Ann IM 2001;135:801; 2001;134:1043), yet prognosis just as bad ([Framingham] Nejm 1984;311:1144) (Table 2.2)
Table 2.2 Value of Specific Components of the Chest Pain History for the Diagnosis of Acute Myocardial Infarction (AMI)
| Pain Descriptor | Reference | No. of Patients | Positive Likelihood
Ratio (95% CI) |
|---|
| Increased likelihood of AMI |
| Radiation to right arm or shoulder | 29 | 770 | 4.7 (1.9-12) |
| Radiation to both arms or shoulders | 14 | 893 | 4.1 (2.5-6.5) |
| Associated with exertion | 14 | 893 | 2.4 (1.5-3.8) |
| Radiation to left arm | 24 | 278 | 2.3 (1.7-3.1) |
| Associated with diaphoresis | 24 | 8426 | 2.0 (1.9-2.2) |
| Associated with nausea or vomiting | 24 | 970 | 1.9 (1.7-2.3) |
| Worse than previous angina or similar to previous MI | 29 | 7734 | 1.8 (1.6-2.0) |
| Described as pressure | 29 | 11504 | 1.3 (1.2-1.5) |
| Described likelihood of AMI |
| Described as pleuritic | 29 | 8822 | 0.2 (0.1-0.3) |
| Described as positional | 29 | 8330 | 0.3 (0.2-0.5) |
| Described as sharp | 29 | 1088 | 0.3 (0.2-0.5) |
| Reproducible with palpation | 29 | 8822 | 0.3 (0.2-0.4) |
| Inframammary location | 31 | 903 | 0.8 (0.7-0.9) |
| Not associated with exertion | 14 | 893 | 0.8 (0.6-0.9) |
Reproduced with permission from Swap DJ and Nagurney JT. J Am Med Assoc 2005;294:2623. Copyright 2005 American Medical Association, all rights reserved.
Si:Pericardial rub on day 2+, usually without ST changes (Nejm 1984;311:1211); S4 gallop; fever <103°F; transient S2 paradoxical split
Right ventricular infarct syndrome(Nejm 1998;338:978; 1994;330:1211): acute inferior MI, Kussmaul's si (paradoxical increases in JVP with inspiration) (Ann IM 1983;99:608), high CVP with low PAPs and PCWPs so all nearly equal, like pericardial tamponade (Nejm 1983;309:39, 551), low cardiac output; occurs in 50% of IWMI pts (Nejm 1993;328:982) but clinically significant in 30% (Nejm 1988;338:978) and nearly 100% of those w CPK levels >2000 IU (J. Sutherland 1/96); reversible w reperfusion rx (Nejm 1998;338:933)
Rectal exam important for guaiac and detection of BPH (Nejm 1969;281:238; 1970;282:167)
15% in hospital mortality before thrombolytics, now 7-10%; 10% of survivors get severe pump failure, another 10% get persistent angina, 10% "flunk" discharge mini-ETT, another 10% "flunk" maximal ETT at 6 wk; remaining 50% do fine (Nejm 1986;314:161)
Prognosis is similar for Q-wave and non-Q-wave infarcts (Am J Med 2000;108:381) although non-Q-wave MIs are followed by more infarcts and angina but are associated w less CHF (Jama 1992;268:1545); is not affected by 1st-degree heart block, PVCs, or Vtach (Ann IM 1992;117:31), RBBB (Ann IM 1972;77:677), or type A personality (Nejm 1985;312:737); better prognosis if preinfarction angina preceded (Nejm 1996;334:7)
Age-adjusted 6 mo survival for women under age 75 yr is 15% worse than for men (Nejm 1999;341:217; 1998;338:8; Jama 1998;280:1405) primarily because they have worse MIs
Concomitant RV infarct increases IWMI mortality from 6% to 30% (Nejm 1993;328:982); mitral regurgitation, when severe, is associated w a 50% 1-yr mortality despite all interventions (Ann IM 1992;117:18)
In elderly, aggressive invasive study and rx does not improve mortality (US vs. Canadian 65+ yr olds—Nejm 1997;336:1500)
Lab:
Chem:Enzymes (Ann IM 1986;105:221):
- CPK and fractions up in 12 h, peak at 2 d, last 4 d; CPK-MB subfractions MB2 and MB1 in 1st 6 h after onset of pain have 95% sens/specif and may be used to send home from ER (Nejm 1994;331:561, 607); total CPK correlates with MI size; may double in MI but still be less than upper limit of normal (Am J Cardiol 1983;51:24); MB band is increased also by increased death and regeneration of skeletal muscle (Ann IM 1981;94:341) and by decreased clearance in myxedema; MM is increased by hypothyroidism, myopathy; BB band is increased by CNS and/or smooth muscle damage (Bull Rheum Dis 1983;33(2):1)
- Troponin I and T levels, especially sens-Trop I, elevate over first 3 h (90% specif) (Nejm 2009;361:849, 858, 913) and stay up for 7-10 d; levels correlate w worse outcomes (Nejm 1996;335:1333, 1342, 1388); also useful perioperatively when surgery may increase CPK (Nejm 1994;330:670). But r/o other nonthrombotic causes (Table 2.3).
- LDH and fx's: isoenzymes 4 and 5 (rapidly migrating) increased, r/o renal and red cell source
- AST (SGOT) up in 24 h, peaks at 2-4 d, lasts up to 7 d
- Malondialdehyde (MDA)-modified LDL >0.85 mg % (Jama 1999;281:1718), 95% sens and specif for unstable angina or MI; combined w troponin I, is 99% sens and specif
- Myeloperoxidase level on adm perhaps (Nejm 2003;349:1595) but has a fairly continuous rise w ischemia likelihood, not the step up of CPK or troponin levels
Noninv Lab:(Ann IM 1989;110:470)
- Echo for mitral regurgitation, aneurysm, ejection fraction estimation, and mural thrombi with 77% sens and 93% specif (Nejm 1982;306:1509)
- EKG (EKG Reading) may show ST elevations (50% sens), duration of elevation correlates with extent of injury (Nejm 1969;280:123), T inversions much less specif (r/o acute cholecystitis—Ann IM 1992;116:218). In RV infarct, ST elevations present in V1, or V3-6R, especially V4R w 80+% sens/specif (Nejm 1993;328:981)
- New RBBB or LBBB indicate occlusion of anterior descending proximal to 1st septal branch (Nejm 1993;328:1036), both worsen prognosis (Ann IM 1998;129:690)
- ETT (Circ 1996;94:2341): estimates prognosis (Nejm 1979;301:341), or more often with thallium (85% sens/specif—Ann IM 1990;113:684, 703); predicts 5-yr survival (Ann IM 1987;106:793)
Table 2.3 Nonthrombotic Causes and Presumed Mechanism for Elevated Cardiac Troponin Level
| Diagnosis | Mechanism |
|---|
| Demand ischemia |
| Sepsis/systemic inflammatory response syndrome | Myocardial depression/supply-demand mismatch |
| Hypotension | Decreased perfusion pressure |
| Hypovolemia | Decreased filling pressure/output |
| Supraventricular tachycardia/atrial fibrillation | Supply-demand mismatch |
| Left ventricular hypertrophy | Subendocardial ischemia |
| Myocardial ischemia |
| Coronary vasospasm | Prolonged ischemia with myonecrosis |
| Intracranial hemorrhage or stroke | Imbalance of autonomic nervous system |
| Ingestion of sympathomimetic agents | Direct adrenergic effects |
| Direct myocardial damage |
| Cardiac contusion | Traumatic |
| Direct current cardioversion | Traumatic |
| Cardiac infiltrative disorders | Myocyte compression |
| Chemotherapy | Cardiac toxicity |
| Myocarditis | Inflammatory |
| Pericarditis | Inflammatory |
| Cardiac transplantation | Inflammatory/immune-mediated |
| Myocardial strain |
| Congestive heart failure | Myocardial wall stretch |
| Pulmonary embolism | Right ventricular stretch |
| Pulmonary hypertension or emphysema | Right ventricular stretch |
| Strenuous exercise | Ventricular stretch |
| Chronic renal insufficiency | Unknown |
Reproduced with permission from Jeremias A, Gibson C. Alternative causes for elevated cardiac troponin levels when acute coronary syndromes are excluded..Ann Int Med 2005;142:786
Rx:
Primary preventive interventions:
- ASA tab qod (Nejm 1992;327:175; 1989;321:129) or qd 75-325 mg (Ann IM 1996;124:292, Med Let 1995;37:14) after angina or MI, or as part of rx of HT (Lancet 1998;351:1755); effect is counteracted by ibuprofen but not acetaminophen, or COX-2s (Nejm 2001;345:1809); helps stroke but not MI risk in women <65 yr (Nejm 2005;352:1293)
Figure 2.1 An electrocardiogram from a patient with an inferior MI and RV infarct; ST-segment elevation is evident in leads II, II, and aVF, with the associated RV MI indicated by Q waves and ST-segment elevation in the right precordial leads.
Reproduced with permission from Kinch JW, Ryan TJ. Current concepts: right ventricular infarction. New Eng J Med 1994;330:1214. Copyright 1994 Mass. Medical Society, all rights reserved.
- Dietary interventions like lowering cholesterol as does American Heart Association diet (BMJ 1992;304:1015) and "Mediterranean diet" (Atherosclerosis). As primary prevention, NNT-5 = 53; as secondary prevention, NNT-5 = 16 (J Fam Pract 1996;42:577)
- Perioperative
-blockers like atenolol 5-10 mg iv per- and postop +50 mg po bid during hospitalization decr risk of cardiac morbidity/mortality by 11% (Nejm 1996;335:1713, 1761) - Smoking cessation decreases risk to baseline in 3 yr (Nejm 1990;322:213); probably ok to use nicotine patch post-MI (Nejm 1996;335:1792)
- Statin rx if 3+ risk factors helps (NNT-3 = 53) even if no hyperlipidemia (Lancet 2003;361:1149)
Secondary preventive interventions (post-MI): above, plus
- -blocker within 24 h of MI and cont'd indefinitely (BMJ 1999;318:1730; Jama 1998;280:623), improves survival even if elderly, low EF, non-Q-wave MI, or have COPD (NNT-2 = 10) (Nejm 1998;339:489—but not an RCT); like metoprolol 5 mg iv q 5 min × 3, then 50 mg po bid × 1 d, then 100 mg bid, or atenolol 50-100 mg po qd, helps prevent recurrent MIs (Circ 1994;90:762; TIMI study—Nejm 1989;320:618); and fatal ventricular arrhythmias; use in elderly as well (Jama 1997;277:115) in post-Q-wave MI, increases survival for 6+ yr (timolol—Nejm 1985;313:1055), all work (Med Let 1982;24:44)
- ACE inhibitors within 24 h of MI (Circ 1998;97:2202) especially if anterior MI, CHF, elevated pulse; and for 6 wk (Lancet 1994;343:1115); cont'd indefinitely if EF <40% (J Am Coll Cardiol 1996;27:337; Ann IM 1994;121:750; Nejm 1992;327:669; 1992;327:629, 685); like captopril 50 mg tid, increases ETT performance and decreases LV size (Nejm 1988;319:80), or ramipril 2.5-5 mg po bid (Lancet 1997;349:1493); prolongs life after MI even if no sx (Med Let 1994;36:69) but only if EF <40% (Nejm 2004;351:2058). ARBs probably equally safe/effective (Nejm 2008;358:1547, 1615) but no benefit using both.
- Statin (HMG CoA) lipid rx post-MI reduces further MIs and mortality (NNT-5 = 30-33—Nejm 1996;335:1001; Lancet 1994;344:1383; or better, NNT-1 = 25—Jama 2001;285:430); rx LDL to <100 mg % (Jama 1997;277:1281, Nejm 1997;336:153) or even lower helps more (Nejm 2004;350:1495); helps in elderly age 65-75 yr too (Ann IM 1998;129:681)
- Fibrate rx of HDL <40 mg %, eg, w gemfibrosil (Nejm 1999;341:410); for MI, NNT-5 = 23 (ACP J Club 2000;132:44)
- In all diabetics, continuous iv insulin × 24 h then qid sc × yrs, improves survival, NNT-1 = 13 (J Am Coll Cardiol 1995;26:57)
of acute MI:
- ASA 325 mg po stat helps survival dramatically (Nejm 1997;336:847)
- Clopidogrel (Plavix) 300 mg × 1 then 75 mg po qd × 6-9 mo; improves outcomes (NNT = 14-33) (Jama 2005;294:1224; Nejm 2005;352:1179) vs. NNT = 122 (ACP J Club 2006;144:58, Lancet 2005;366:1607); avoid concomitant PPI use, which blocks effectiveness (Jama 2009;301:937)
- LMW Heparin along or in combination w other interventions improves outcome (NNT = 75±) even in 3rd world (Jama 2005;293:427)
- Angioplasty (PCTA) of evolving acute MI as acute primary rx w stenting, rather than thrombolysis, preferable if available (Europ Hrt J 2007;28:679; Jama 2006;296:1749; Nejm 2000;343:385; even in elderly—Jama 1999;282:341), in high-volume centers (Nejm 2002;346:957) and community hospitals by stat transfers w abciximab alone or w 1/2 dose thrombolysis (Nejm 2004;291:947, 1000) to cath labs w or w/o surgical backup (Jama 2002;287:1943) if can do w/i 2 h of onset (Lancet 2003;361:13; Nejm 2003;349:733); "ischemia-guided rx" no longer the standard (Lancet 2004;364:1045) even in elderly (>75 yr) (Circ 2004;110:1213); better success in high-volume centers (Nejm 2000;342:1573); helpful even over 12 h out? (Jama 2005;293:2865, 2930). Angioplasty of vessels >3 d after MI of no benefit except perhaps if can’t take life long B-blockers? (Nejm 2006;355:2395, 2475)
- Thrombolysis w streptokinase, TPA, etc (Thrombolytics) helps all pts including those over age 75 yr (Nejm 1992;327:7) although intracranial bleeding risk increases from <0.5% under 65 yr, to 2.5% over 75 yr (Ann IM 1998;129:597), hence still unclear if should use over age 75 yr (Circ 2000;101:2239); if sys BP
175 or dias 100, bleeding risk is double (Ann IM 1996;125:891); use if pain is <6 h duration, or if 6-12 h and STs still elevated (Lancet 1996;348:771, 1993;342:759, 767) or LBBB and good story (Jama 1999;281:714; Ann IM 1998;129:690); does not help ST depressions, which should be rx'd as unstable angina (Anti-Anginal Meds). Give concomitantly or follow either with heparin iv × 1+ d (Nejm 1990;323:1433) + ASA 160 mg po qd + -blocker (Ann IM 1991;115:34). CPK-MB and troponin T levels should rise 5 × at 60 min and 5-10 × at 90 min to indicate reperfusion (90% sens, ~65% specif) (J Am Coll Cardiol 1998;31:1499) - -blocker and ACEI rx as above
- Nitroglycerine, as patch or iv if volume ok especially if cont'd pain, perhaps even if no pain; especially helpful if any element of CHF or if large anterior MI; avoid if recent sildenafil (Viagra) use
- Insulin iv w glucose and KCl no benefit (Jama 2005;293:437, 489)
- Rehab programs probably help (ACP J Club 1999;131:41) over 3 mo if 3 wk post-MI ETT achieves <8 METS (Ann IM 1988;109:650, 671). Get 3-wk post-MI ETT and return to work at 4 wk unless severe ischemia (Ann IM 1992;117:383; Nejm 1992;327:227)
- Statins initiated within 14 days of AMI do not improve outcomes over 1st 4 mo (Jama 2006;295:2046)
- CABG after angiography if low eject fraction (21-49%) and multivessel disease, or left main disease; can do it 1 mo post-MI (Nejm 1982;307:1065)
of complications
- Bradyarrhythmias: rx in IWMI only if pain, PVCs, CHF, or pulse <45/min and unstable, then pace (Nejm 1975;292:572); in anterior MI, pace to prevent 20-40% evolving to complete heart block if anterior MI + RBBB, RBBB + left anterior hemiblock, RBBB + left posterior hemiblock, or LBBB; bifascicular block evolving into trifascicular block during MI needs permanent pacer even if returns to normal later (Mod Concepts Cardiovasc Dis 1976;45:129)
- CHF/shock: dobutamine (Nejm 1980;303:846) + nitroprusside acutely; or early revascularization to improve on 60% mortality (Nejm 1999;341:625); ACE inhibitors as above
- Mural thrombi in anterior MI, prevent with heparin to PTTs ~48 s for 10 d, sc not enough (Nejm 1989;320:352)
- Papillary muscle rupture acutely, surgery sooner not later (Nejm 1996;335:1417)
- Pericarditis should not be rx'd with indomethacin, which can cause spasm (Nejm 1981;305:1171); other NSAIDs better
- RV infarct, increase preload w iv saline, avoid nitrates and diuretics (lower preload), dobutamine drip, nitroprusside drip, sequential pacing, isoproterenol to unload RV (Nejm 1993;328:982)
- Ventricular arrhythmias: amiodarone or implantable defibrillator for sudden death survivors (Circ 1995;91:2195) or perhaps all w EF <30%? (Nejm 2002;346:877, 931) at least for 1st 6 mo (Nejm 2005;352:2638)
- Wall rupture or VSD development, surgery if slow (Nejm 1983;309:539)
- Depression increased following MI (Jama 2006;295:2874)