Pocket Medicine

CARDIOLOGY

ACUTE CORONARY SYNDROMES

Ddx (causes of myocardial ischemia/infarction other than atherosclerotic plaque rupture)

•  Nonatherosclerotic coronary artery disease

Spasm: Prinzmetal’s variant, cocaine-induced (6% of CP + cocaine use r/i for MI)

Dissection: spontaneous (vasculitis, CTD, pregnancy), aortic dissection with retrograde extension (usually involving RCA → IMI) or mechanical (catheter, surgery, trauma)

Embolism: endocarditis, prosthetic valve, mural thrombus, AF, myxoma; thrombosis

Vasculitis: Kawasaki syndrome, Takayasu arteritis, PAN, Churg-Strauss, SLE, RA

Congenital: anomalous origin from aorta or PA, myocardial bridge (intramural segment)

•  Fixed CAD but ↑ myocardial O2 demand (eg, ↑ HR, anemia, AS) → “demand” ischemia

•  Myocarditis; Takatsubo/stress CMP; toxic CMP; cardiac contusion

Clinical manifestations ( JAMA 2005;294:2623)

•  Typical angina: retrosternal pressure/pain/tightness ± radiation to neck, jaw or arms

precip. by exertion, relieved by rest or NTG; in ACS, new-onset, crescendo or at rest

•  Associated symptoms: dyspnea, diaphoresis, N/V, palpitations or lightheadedness

•  Many MIs (~20% in older series) are initially unrecognized b/c silent or atypical sx

Physical exam

•  Signs of ischemia: S4, new MR murmur 2° pap. muscle dysfxn, paradoxical S2, diaphoresis

•  Signs of heart failure: ↑ JVP, crackles in lung fields,  S3, HoTN, cool extremities

•  Signs of other areas of atherosclerotic disease: carotid or femoral bruits, ↓ distal pulses

Diagnostic studies

•  ECG: ST ↓/↑, TWI, new LBBB, hyperacute Tw. Qw/PRWP may suggest prior MI, ∴ CAD ✓ ECG w/in 10 min of presentation, with any Δ in sx and at 6–12 h; compare w/ baseline

dx of STEMI if old LBBB: ≥1 mm STE concordant w/ QRS (Se 73%, Sp 92%), STD ≥1 mm V1–V3 (Se 25%, Sp 96%) or STE ≥5 mm discordant w/ QRS (Se 31%, Sp 92%)

•  Cardiac biomarkers (Tn preferred, or CK-MB): ✓ Tn at baseline & 3–6 h after sx onset; a rise to >99th %ile in approp. clinical setting dx of MI (see “Chest Pain”); nb, in Pts w/ ACS & ↓ CrCl, ↑ Tn still portends poor prognosis (NEJM 2002;346:2047)

•  If low prob, stress testCT angio or rest perfusion imaging to r/o CAD (see “Chest Pain”)

•  TTE (new wall motion abnl) suggestive of ACS; coronary angio gold standard for CAD

Prinzmetal’s (variant) angina

•  Coronary spasm → transient STE usually w/o MI (but MI, AVB, VT can occur)

•  Pts usually young, smokers, ± other vasospastic disorders (eg, migraines, Raynaud’s)

•  Angiography → nonobstructive CAD, focal spasm w/ hyperventilation, acetylcholine

•  Treatment: high-dose CCB, nitrates (+SL NTG prn), ? a-blockers; d/c smoking

•  Cocaine-induced vasospasm: use CCB, nitrates, ASA; ? avoid bB, but data weak and labetalol appears safe (Archives 2010;170:874; Circ 2011;123:2022)

Approach to triage

•  If hx and initial ECG & biomarkers non-dx, repeat ECG & biomarkers 3–6 h later

•  If remain nl and low likelihood of ACS, search for alternative causes of chest pain

•  If remain nl, have ruled out MI, but if suspicion for ACS based on hx, then still need to r/o UA w/ stress test to assess for inducible ischemia (or CTA to r/o CAD);

if low risk (age ≤70;  prior CAD, CVD, PAD;  rest angina) can do as outPt w/in 72 h (0% mortality, <0.5% MI, Ann Emerg Med 2006;47:427)

if not low risk, admit and initiate Rx for possible ACS and consider stress test or cath

Coronary angiography (Circ 2007;116:e148 & 2012;126:875)

•  Conservative strategy = selective angiography. Medical Rx with pre-d/c stress test; angio only if recurrent ischemia or strongly  ETT. Indicated for: low TIMI risk score, Pt or physician preference in absence of high-risk features, low-risk women (JAMA 2008;300:71).

•  Invasive strategy = routine angiography w/in 72 h

Immediate (w/in 2 h) if: refractory/recurrent ischemia, hemodynamic or electrical instability

Early (w/in 24 h) if Tn, ST Δ, TRS ≥3, GRACE risk score >140 (NEJM 2009;360:2165)

Delayed (ie, acceptable anytime w/in 72 h) if: diabetes, EF <40%, GFR <60, post-MI angina, PCI w/in 6 mo, prior CABG or high-risk stress results

32% ↓ rehosp for ACS, nonsignif 16% ↓ MI, no Δ in mortality c/w cons. (JAMA 2008;300:71)

↑ peri-PCI MI counterbalanced by ↓↓ in spont. MI

Mortality benefit seen in some studies, likely only if cons. strategy w/ low rate of angio

Figure 1-2 Approach to UA/NSTEMI

STEMI

Requisite STE (at J point)

•  ≥2 contiguous leads w/ ≥1 mm (except for V2–V3: ≥2 mm in  and ≥1.5 mm in )

•  New or presumed new LBBB

Reperfusion (“time is muscle”)

•  Immediate reperfusion (ie, opening occluded culprit coronary artery) is critical

•  In PCI-capable hospital, goal should be primary PCI w/in 90 min of 1st medical contact

•  In non-PCI-capable hospital, consider transfer to PCI-capable hospital (see below), o/w fibrinolytic therapy w/in 30 min of hospital presentation

•  Do not let decision regarding method of reperfusion delay time to reperfusion

Primary PCI (NEJM 2007;356:47)

•  Indic: STE + sx <12 h; ongoing ischemia 12–24 h after sx onset; shock regardless of time

•  Superior to lysis: 27% ↓ death, 65% ↓ reMI, 54% ↓ stroke, 95% ↓ ICH (Lancet 2003;361:13)

•  Thrombus aspiration during angio prior to stenting ↓ mortality (Lancet 2008;371:1915)

•  Do not intervene on nonculprit lesions; risk stratify w/ imaging stress (Circ 2011;124:e574)

•  Transfer to center for 1° PCI may also be superior to lysis (NEJM 2003;349:733), see below

Fibrinolysis

•  Indic: STE/LBBB + sx <12 h; benefit if sx >12 h less clear; reasonable if persist. sx & STE

•  Mortality ↓ ~20% in anterior MI or LBBB and ~10% in IMI c/w  reperfusion Rx

•  Prehospital lysis (ie, ambulance): further 17% ↓ in mortality ( JAMA 2000;283:2686)

•  ~1% risk of ICH; high-risk groups include elderly (~2% if >75 y), women, low wt

•  Although age not contraindic., ↑ risk of ICH in elderly (>75 y) makes PCI more attractive

Nonprimary PCI

•  Facilitated PCI: upstream lytic, GPI or GPI + ½ dose lytic before PCI offers no benefit

•  Rescue PCI if shock, unstable, failed reperfusion or persistent sx (NEJM 2005;353:2758)

•  Routine angio ± PCI w/in 24 h of successful lysis: ↓ D/MI/revasc (Lancet 2004;364:1045) and w/in 6 h ↓ reMI, recurrent ischemia, & HF compared to w/in 2 wk (NEJM 2009;360:2705);

∴ if lysed at non-PCI capable hospital, consider transfer to PCI-capable hospital ASAP esp. if high-risk presentation (eg, anterior MI, inferior MI w/ low EF or RV infarct, extensive STE or LBBB, HF, ↓ BP or ↑ HR)

•  Late PCI (median day 8) of occluded infarct-related artery: no benefit (NEJM 2006;355:2395)

LV failure (~25%)

•  Diurese to achieve PCWP 15–20 → ↓ pulmonary edema, ↓ myocardial O2 demand

•  ↓ Afterload → ↑ stroke volume & CO, ↓ myocardial O2 demand

can use IV NTG or nitroprusside (risk of coronary steal) → short-acting ACEI

•  Inotropes if HF despite diuresis & ↓ afterload; use dopamine, dobutamine or milrinone

•  Cardiogenic shock (~7%) = MAP <60 mmHg, CI <2 L/min/m2, PCWP >18 mmHg; inotropes, mech support [eg, VAD, IABP (trial w/o benefit NEJM 2012;367:1287)] to keep CI >2; pressors to keep MAP >60; if not done already, coronary revasc (NEJM 1999;341:625)

IMI complications (Circ 1990;81:401; NEJM 1994;330:1211; JACC 2003;41:1273)

•  Heart block (~20%, occurs because RCA typically supplies AV node)

40% on present., 20% w/in 24 h, rest by 72 h; high-grade AVB can develop abruptly

Rx: atropine, epi, aminophylline (100 mg/min × 2.5 min), temp wire

•  RV infarct (30–50%, but only ½ of those clinically signif). HoTN; ↑ JVP,  Kussmaul’s; 1 mm STE in V4R; RA/PCWP ≥0.8; RV dysfxn on TTE; prox RCA occl.

Rx: optimize preload (RA goal 10–14, BHJ 1990;63:98); ↑ contractility (dobutamine); maintain AV synchrony (pacing as necessary); reperfusion (NEJM 1998;338:933); mechanical support (IABP or RVAD); pulmonary vasodilators (eg, inhaled NO)

Mechanical complications (incid. <1% for each; typically occur a few days post-MI)

•  Free wall rupture: ↑ risk w/ lysis, large MI, ↑ age, , HTN; p/w PEA or hypoTN, pericardial sx, tamponade; Rx: volume resusc., ? pericardiocentesis, inotropes, surgery

•  VSD: large MI in elderly; AMI → apical VSD, IMI → basal septum; 90% w/ harsh murmur ±

thrill (NEJM 2002;347:1426); Rx: diuretics, vasodil., inotropes, IABP, surgery, perc. closure

•  Papillary muscle rupture: more common after inf MI (PM pap. muscle supplied by PDA alone) than ant MI (AL pap. muscle supplied by diags & OMs); 50% w/ new murmur, rarely a thrill, ↑ v wave in PCWP tracing; asymmetric pulmonary edema. Rx: diuretics, vasodilators, IABP, surgery.

Arrhythmias post-MI

•  Treat as per ACLS for unstable or symptomatic bradycardias & tachycardias

•  AF (10–16% incidence): β-blocker or amio, ± digoxin (particularly if HF), heparin

•  VT/VF: lido or amio × 6–24 h, then reassess; ↑ βB as tol., replete K & Mg, r/o ischemia;

early monomorphic (<48 h post-MI) does not carry bad prognosis

•  Accelerated idioventricular rhythm (AIVR): slow VT (<100 bpm), often seen after

successful reperfusion; typically self-terminates and does not require treatment

•  May consider backup transcutaneous pacing (TP) if: 2° AVB type I, BBB

•  Backup TP or initiate transvenous pacing if: 2° AVB type II; BBB + AVB

•  Transvenous pacing (TV) if: 3° AVB; new BBB + 2° AVB type II; alternating LBBB/RBBB (can bridge w/ TP until TV, which is best accomplished under fluoroscopic guidance)

Prognosis

•  In registries, in-hospital mortality is 6% w/ reperfusion Rx (lytic or PCI) and ~20% w/o

•  Predictors of mortality: age, time to Rx, anterior MI or LBBB, heart failure (Circ 2000;102:2031)

PREDISCHARGE CHECKLIST AND LONG-TERM POST-ACS MANAGEMENT

Risk stratification

•  Stress test if anatomy undefined; consider stress if signif residual CAD post-PCI of culprit

•  Assess LVEF prior to d/c; EF ↑ ~6% in STEMI over 6 mo ( JACC 2007;50:149)

Medications (barring contraindications)

•  Aspirin: 81 mg daily

•  P2Y12 inhib (eg, clopi, prasugrel or ticagrelor): ≥12 mo if stent (min 1 mo after BMS); some PPIs interfere w/ biotransformation of clopi and ∴ plt inhibition, but no convincing impact on clinical outcomes (Lancet 2009;374:989; NEJM 2010;363:1909); use w/PPIs if h/o GIB or multiple GIB risk factors ( JACC 2010;56:2051)

•  β-blocker: 23% ↓ mortality after MI

•  Statin: high-intensity lipid-lowering (eg, atorvastatin 80 mg, NEJM 2004;350:1495)

•  ACEI: lifelong if HF, ↓ EF, HTN, DM; 4–6 wk or at least until hosp. d/c in all STEMI

? long-term benefit in CAD w/o HF (NEJM 2000;342:145 & 2004;351:2058; Lancet 2003;362:782)

•  Aldosterone antag: 15% ↓ death if EF <40% & either DM or s/s of HF (NEJM 2003;348:1309)

•  Nitrates: standing if symptomatic; SL NTG prn for all

•  Oral anticoagulants: if warfarin needed in addition to ASA/clopi (eg,  AF or LV thrombus), target INR 2–2.5. ? stop ASA if at high bleeding risk on triple Rx (Lancet 2013;381:1107). Low-dose rivaroxaban (2.5 mg bid) in addition to ASA & clopi → 16% ↓ D/MI/stroke and 32% ↓ all-cause death, but ↑ major bleeding and ICH (NEJM 2012;366:9).

ICD (NEJM 2008;359:2245)

•  If sust. VT/VF >2 d post-MI not due to reversible ischemia

•  Indicated in 1° prevention of SCD if post-MI w/ EF ≤30–40% (NYHA II–III) or ≤30–35% (NYHA I); need to wait ≥40 d after MI (NEJM 2004;351:2481 & 2009;361:1427)

Risk factors and lifestyle modifications (Circ 2011;124:2458)

•  Low chol. (<200 mg/d) & fat (<7% saturated) diet; LDL goal <70 mg/dL; ? Ω;-3 FA

•  BP <140/90 mmHg; smoking cessation

•  If diabetic, tailor HbA1c goal based on Pt (avoid TZDs if HF)

•  Exercise (30–60 min 5–7 ×/wk); cardiac rehab; BMI goal 18.5–24.9 kg/m2

•  Influenza vaccination (Circ 2006;114:1549); screen for depression