ACSRuleOut

Chest pain / ACS rule-out · complete reference · all trials · full doses + brand names · Full Card

Symptoms / Associated Sx

• Typical ACS: substernal pressure, squeezing, or tightness ± radiation to left arm, jaw, neck, or back; associated diaphoresis, nausea, dyspnea; onset at rest or with exertion; duration >20 minutes not relieved by nitroglycerin (NTG) or rest suggests STEMI/NSTEMI rather than stable angina

• Atypical presentations (up to 30% of ACS — critically important to recognize): isolated dyspnea; fatigue; epigastric pain/nausea/vomiting; jaw pain; syncope; new HF; occurring disproportionately in elderly (>75), women, diabetics, and CKD patients — these groups are undertriaged

• High-risk features requiring immediate evaluation regardless of HEART score: diaphoresis with chest symptoms; hemodynamic instability (SBP <90, cool/diaphoretic); new ECG changes; radiation to both arms or jaw; syncope/near-syncope with chest symptoms

• Reproducible chest wall tenderness: present in ~7% of confirmed ACS — does NOT exclude ACS; do NOT use reproducibility alone to rule out; ECG + troponin required in all patients regardless of exam findings

• Stent thrombosis: CP within 30 days of PCI in ANY territory → immediate cath lab activation regardless of ECG or troponin results — zero tolerance approach

Neg

• Pt denies STE ≥1 mm in ≥2 contiguous leads or STEMI equivalents (new LBBB + Sgarbossa criteria ≥5 points; de Winter T-waves; posterior STEMI pattern V1–V3 ST↓ with V7–V9 STE ≥0.5 mm; aVR STE ≥1 mm + 8-lead ST↓) — these mandate immediate cath lab activation; exit ACS rule-out algorithm entirely

• Pt denies tearing/ripping quality chest pain radiating to the back between shoulder blades + BP differential >20 mmHg between arms + widened mediastinum on CXR — argues against aortic dissection (CTA chest/abdomen/pelvis BEFORE any anticoag, thrombolytics, or heparin; RCA ostium dissection mimics inferior STEMI — never give thrombolytics without ruling out dissection)

• Pt denies sharp pleuritic chest pain worsening with inspiration/lying flat and relieved by leaning forward + audible pericardial friction rub + diffuse saddle ST elevation in multiple leads without territorial reciprocal changes — argues against pericarditis (pericarditis: PR depression; no focal WMA on echo; no territorial ECG distribution; troponin may be mildly elevated in myopericarditis)

• Pt denies pleuritic chest pain + acute dyspnea + tachycardia + hypoxia + signs of DVT (unilateral leg swelling/tenderness) — argues against PE (PE: RV strain on ECG [S1Q3T3]; RV dilation on echo — not LV; CT-PA confirms; troponin elevated from RV wall stress, not ischemia)

• Pt denies biphasic or deep symmetric T-wave inversions in V2–V3 in the pain-FREE state (Wellens syndrome — critical proximal LAD stenosis; troponin may be normal; stress test CONTRAINDICATED → risk of anterior STEMI during test; requires urgent cardiology + cath)

Social History (SHx)

• Prior CAD, MI, PCI, CABG (stent type — BMS vs DES; date; vessel treated; CP within 30 days of PCI = stent thrombosis until proven otherwise → cath lab immediately; prior cath results — anatomy determines likelihood of ischemia); tobacco (current/former/pack-years — strongest modifiable CAD RF)

• HTN, hyperlipidemia, DM, obesity, cocaine/stimulant use, family history of premature CAD (first-degree relative: M <55 years, F <65 years — independent RF); current medications (antiplatelet/anticoag — missed doses? DAPT timing post-PCI)

• HEART score history component: known CAD with stenosis >50% = +2 (highest risk history item regardless of other HEART components)

Main Etiology

• Type 1 MI (plaque rupture/erosion → platelet aggregation → acute coronary thrombus → partial or complete coronary occlusion): most common ACS mechanism; NSTEMI = partial occlusion or with collaterals; STEMI = complete occlusion without collaterals

• Type 2 MI (supply/demand mismatch without plaque rupture — see Type2MI card): most common MI type in hospitalized non-cardiac patients; DAPT NOT indicated unless cath confirms obstructive CAD

• SCAD (spontaneous coronary artery dissection): young women, peripartum, fibromuscular dysplasia; avoid thrombolytics (↑dissection propagation); conservative management preferred; cath only if hemodynamically unstable

• MINOCA (MI with non-obstructive coronary arteries): normal cath with troponin elevation; mandatory cardiac MRI within 1 week (myocarditis vs Takotsubo vs true ischemic MINOCA); do NOT reflexively load DAPT — etiology determines management

• Non-ischemic chest pain: GERD/esophageal spasm; musculoskeletal (costochondritis/Tietze syndrome); anxiety/hyperventilation; pleuritis; herpes zoster (burning dermatomal distribution)

RF

• Traditional Framingham: tobacco (strongest modifiable — ↑ACS risk 2–4×), HTN, hyperlipidemia (LDL >190 = very high risk), DM, age (M ≥45, F ≥55), family hx premature CAD (M <55, F <65), obesity (BMI >30)

• Non-traditional: CKD (eGFR <60 = CAD risk equivalent), RA/SLE/HIV (chronic inflammation → accelerated atherosclerosis), OSA (untreated → HTN + inflammation), cocaine/stimulants (coronary vasospasm + thrombosis), Lp(a) elevation (>50 mg/dL = independent high-risk RF), PCOS, preeclampsia history

• HEART score RF component: ≥3 traditional risk factors OR known atherosclerotic disease = +2 points; 1–2 RF = +1; none = 0

Data

• ECG ≤10 minutes (Class I) (12-lead MANDATORY: STEMI criteria → cath lab; ST↓ ≥0.5 mm or T-wave inversions = high-risk NSTEMI; Wellens syndrome [biphasic Type A or deep symmetric Type B TWI in V2–V3 in pain-free state = critical LAD stenosis — do NOT stress test]; de Winter T-waves [upsloping ST↓ + tall peaked T-waves V1–V4 = LAD occlusion — treat as STEMI equivalent]; aVR STE ≥1 mm + diffuse ST↓ in ≥8 leads = left main or proximal LAD occlusion; normal ECG in 6% of NSTEMI — does NOT exclude)

• hs-cTn (high-sensitivity cardiac troponin) 0h + 1h (ESC 0/1h rapid rule-out algorithm — assay-specific cutoffs: Siemens ADVIA Centaur hs-cTnI: rule-out 0h <5 ng/L + Δ1h <4 ng/L; rule-in 0h >52 ng/L OR Δ1h >6 ng/L; Roche Elecsys hs-cTnT has DIFFERENT validated cutoffs — ALWAYS verify your institution's specific assay and cutoffs; applying wrong cutoffs = false rule-outs → missed MIs; sensitivity >98.5% for MI ≥3h after symptom onset)

• Standard troponin 0h + 3h (if hs-cTn unavailable) (single negative troponin at <3h from symptom onset is INSUFFICIENT to exclude ACS — troponin peaks 6–24h post-MI; must have ≥2 draws ≥3h apart; a common error leading to premature discharge)

• HEART Score — calculate at presentation (History [H]: 0/1/2 points; ECG [E]: 0/1/2 points; Age [A]: 0/1/2 points; Risk factors [R]: 0/1/2 points; Troponin [T]: 0/1/2 points; Maximum 10 points; 0–3 = low risk [MACE 1.7% at 6 weeks]; 4–6 = moderate [12%]; 7–10 = high [65%]; HEART Pathway RCT: ↓hospitalization 20% with MACE outcomes equivalent to standard care)

• CXR (portable) (widened mediastinum >8 cm — dissection; pulmonary edema — HF decompensation as ACS trigger or complication; pneumothorax; cardiomegaly; pleural effusion)

• BMP (Cr — contrast nephropathy risk stratification; glucose — hyperglycemia ↑post-MI mortality; K+ arrhythmia risk; Na+ — prognosis if HF)

• CTCA (CT coronary angiography) (preferred anatomic rule-out in low-intermediate risk with negative troponins; PROMISE 2015: CTCA equivalent to functional testing for safety in stable chest pain; SCOT-HEART 2018: CTCA ↓fatal MI 2.3% vs 3.9% [NNT 62] at 5 years via ↑statin/aspirin prescribing; HR <65 required [premedicate metoprolol tartrate (Lopressor) 50 mg PO 1h prior if HR >65]; CACS ≥400 = ↑false-positive risk; Cr ≤1.5; no known CAD; no contrast allergy)

• Coronary artery calcium score (CACS) (CACS = 0 → very low 10-year MACE risk [<1%]; useful for intermediate-risk patients without ongoing symptoms; CACS >400 → high-risk; does not assess unstable plaque)

DDx

STEMI (STE ≥1 mm ≥2 leads or STEMI equivalent — cath lab immediately; exit algorithm) · NSTEMI (troponin rise/fall + ischemic sx; HEART ≥4; see NSTEMI card; DAPT + anticoag + cardiology) · Type 2 MI (clear systemic precipitant — treat precipitant; DAPT only if cath confirms obstructive CAD; see Type2MI card) · Aortic dissection (tearing back pain + BP differential — CTA before ANY anticoag or thrombolytics; RCA ostium dissection mimics inferior STEMI) · PE (pleuritic CP + hypoxia + tachycardia + RV dilation on echo — CT-PA) · Pericarditis (diffuse saddle ST↑ + PR↓ + pleuritic + friction rub — no territorial reciprocal changes; troponin mildly ↑ in myopericarditis) · MINOCA (troponin + normal coronaries on cath — cardiac MRI within 1 week mandatory; myocarditis vs Takotsubo vs ischemic MINOCA) · GERD/esophageal spasm (burning + postprandial + antacid response — diagnosis of exclusion after ACS definitively excluded) · MSK/costochondritis (reproducible with palpation — ECG + troponin required first; never diagnose by tenderness alone)

Home Meds

• Give immediately if ACS suspected: aspirin (Bayer/Ecotrin) 325 mg PO chewed ×1 (irreversible COX-1 inhibition → ↓thromboxane A2 → ↓platelet aggregation; do NOT await troponin result; give in triage); hold P2Y12 (clopidogrel [Plavix]/ticagrelor [Brilinta]/prasugrel [Effient]) until anatomy confirmed by cath — CABG in 5–10% of NSTEMI patients (requires P2Y12 washout 5–7 days before CABG)

• Continue: all cardiac medications (BB, ACEi/ARB, statins — do NOT hold); existing anticoagulants (discuss timing with cardiology)

• Hold: NSAIDs (ibuprofen [Advil]/naproxen [Aleve]/celecoxib [Celebrex] — avoid indefinitely post-ACS; ↑CV events); metformin (Glucophage) if Cr elevated or contrast planned (restart 48h post-contrast if Cr stable); PDE5 inhibitors (sildenafil [Viagra]/tadalafil [Cialis]) if nitroglycerin (NTG) planned (severe hypotension; hold ×24h for sildenafil, ×48h for tadalafil)

Plan

• Immediate triage (first 10 minutes):

  • ECG ≤10 min — print and interpret immediately; if STEMI or equivalent → activate cath lab, exit this algorithm

  • IV access ×2; continuous telemetry; O2 only if SpO2 <90% (avoid routine O2 — ↑oxidative stress in normoxic patients)

  • Aspirin (Bayer) 325 mg PO chewed ×1 immediately if ACS suspected — before troponin results

  • HEART score calculation from triage data

  • Hold P2Y12 agents until anatomy confirmed — CABG washout requirement

• ESC 0/1h hs-cTn rapid algorithm (validated hs-cTn assay ONLY):

  • Rule-out pathway: 0h <5 ng/L + Δ1h <4 ng/L + HEART ≤3 + no high-risk features → safe discharge (NPV >99.5%; outperforms standard 3h protocol)

  • Rule-in pathway: 0h >52 ng/L OR Δ1h >6 ng/L → NSTEMI (start NSTEMI management; cardiology consult immediately)

  • Observe pathway: neither rule-in nor rule-out at 1h → 3h draw (intermediate zone)

  • CRITICAL: cutoffs above are for Siemens ADVIA Centaur hs-cTnI; Roche Elecsys hs-cTnT and Abbott ARCHITECT hs-cTnI have different validated cutoffs — verify your lab's assay before applying any algorithm

• Standard troponin 0h + 3h (if hs-cTn unavailable): draw at 0h and 3h; single negative at <3h from onset is INSUFFICIENT; troponin peaks 6–24h post-MI; some ACS patients with very early presentation have negative troponin at 3h — extend observation and repeat at 6h if high clinical suspicion

• HEART score-based disposition:

  • HEART 0–3 + negative serial troponins: low risk (MACE 1.7% at 6 weeks; HEART Pathway trial: ↓hospitalization 20% with equivalent safety) → discharge + outpatient CTCA or functional stress testing within 1–2 weeks + cardiology f/u 72h

  • HEART 4–6: admit to telemetry/chest pain unit; serial troponin per protocol; serial ECG with any symptom recurrence; cardiology consult for any rising troponin or ECG change

  • HEART ≥7: high risk — admit + early invasive cardiology strategy; consider urgent cath within 2–24h

• High-risk ECG patterns requiring urgent action (do NOT observe):

  • Wellens syndrome (biphasic [Type A] or deep symmetric [Type B] TWI V2–V3 in pain-free state) → critical proximal LAD stenosis; troponin may be normal; DO NOT perform stress test; urgent cardiology + cath

  • de Winter T-waves (upsloping ST↓ V1–V4 + tall symmetric peaked T-waves) → LAD occlusion equivalent; treat as STEMI; cath lab

  • aVR STE ≥1 mm + diffuse ST↓ ≥8 leads → left main or proximal LAD equivalent → urgent cath

  • New LBBB in ACS context → apply Sgarbossa criteria (concordant STE ≥1 mm = +5; concordant ST↓ V1–V3 ≥1 mm = +3; discordant STE ≥5 mm = +2; ≥5 = STEMI equivalent)

• CTCA (preferred anatomic rule-out): PROMISE 2015 (CTCA vs functional testing — equivalent safety outcomes over 2 years in stable chest pain); SCOT-HEART 2018 (CTCA ↓fatal MI 2.3% vs 3.9% at 5 years [NNT 62] via early statin/aspirin prescribing in subclinical CAD); indications: HEART 0–3 + negative serial troponins + no high-risk ECG features + HR <65 (metoprolol [Lopressor] 50 mg PO 1h prior if HR >65) + Cr ≤1.5 + no significant contrast allergy; CTCA showing non-obstructive CAD (20–50% stenosis) → accelerate preventive therapy (statin + aspirin)

• Stent thrombosis protocol: CP within 30 days of PCI in any coronary territory → immediate cath lab activation regardless of ECG changes or troponin level; zero tolerance — stent thrombosis carries 20–40% mortality; every minute of delay worsens outcome

• MINOCA management (normal coronaries + troponin): cardiac MRI within 1 week mandatory (identifies: myocarditis [LGE in non-ischemic subepicardial pattern]; Takotsubo [apical ballooning with microvascular obstruction]; true ischemic MINOCA [subendocardial LGE in ischemic pattern → vasospasm/embolism/plaque erosion]); do NOT reflexively load DAPT; etiology determines management

• PT/OT eval and treat — early ambulation once ACS excluded or hemodynamically stabilized; fall risk assessment; functional capacity assessment if admitted

• Trend: troponin per protocol (0/1h hs-cTn or 0/3/6h standard); ECG with every symptom recurrence; continuous telemetry during observation; repeat HEART score if troponin rises; glucose monitoring if DM

• Escalation triggers: recurrent CP + any dynamic ECG changes → NSTEMI protocol immediately regardless of initial troponin · troponin rising on any draw → admit + urgent cardiology consult · Wellens/de Winter pattern identified → urgent cath — NEVER stress test · hemodynamic instability (SBP <90 + diaphoresis + new ECG changes) → CCU + activate cath lab · stent thrombosis suspected (CP <30 days post-PCI) → cath lab immediately · CTCA showing significant stenosis (≥70%) → cardiology for stress testing or direct cath referral

• Safe discharge checklist: HEART ≤3 + hs-cTn rule-out criteria met OR ≥2 serial standard troponins negative ≥3h apart + no ongoing symptoms at discharge + no high-risk ECG features; aspirin (Bayer) 81 mg PO daily if not already on; atorvastatin (Lipitor) 40–80 mg PO daily if LDL >70 mg/dL + ≥1 CV RF; outpatient CTCA or stress test within 1–2 weeks; cardiology f/u within 72h; clear return precautions: CP recurrence + diaphoresis + radiation to arm/jaw + syncope + worsening dyspnea → return immediately; nitroglycerin (NTG SL) 0.4 mg SL q5 min ×3 PRN if prior ACS diagnosis

⚠ Red Flags

• STEMI or STEMI equivalent (de Winter T-waves, Sgarbossa ≥5, posterior STEMI, aVR STE + 8-lead ST↓) → cath lab activation immediately — every minute of door-to-balloon delay ↑mortality; no waiting for troponin results

• Wellens syndrome (biphasic or deep symmetric TWI V2–V3 in pain-free state) → critical proximal LAD stenosis; ECG during pain shows STE; troponin may be normal; stress test is contraindicated (risk of anterior STEMI on treadmill); urgent cardiology + cath

• Aortic dissection masquerading as ACS (tearing back pain + BP differential + widened mediastinum) → CTA BEFORE any anticoag, thrombolytics, or heparin; RCA ostium dissection mimics inferior STEMI — if thrombolytics given → massive hemorrhage + death

• Stent thrombosis (CP within 30 days of PCI) → cath lab immediately regardless of ECG or troponin; 20–40% mortality with delayed reperfusion; zero tolerance for watchful waiting

• Single negative troponin at <3h from symptom onset used to discharge → troponin peaks 6–24h post-MI; 10–15% of MIs have negative troponin at 3h from onset; always confirm 2 negative draws ≥3h apart OR validated hs-cTn 0/1h algorithm

• Applying hs-cTn 0/1h cutoffs to a standard (conventional) troponin assay → false rule-outs → missed MIs; verify which assay your institution uses before applying any algorithm

• SCAD (spontaneous coronary artery dissection) in young women/peripartum + ACS → avoid thrombolytics (propagate dissection); conservative management preferred if stable; cath approach carefully to avoid iatrogenic propagation

Senior IM Resident Pearls

• HEART score: HEART 0–3 + negative serial troponins = MACE 1.7% at 6 weeks → safe discharge; HEART Pathway RCT (2016, NEJM): ↓hospitalization 20% vs standard care with identical 30-day MACE; calculate at every chest pain triage; document score in chart

• hs-cTn assay specificity — the most dangerous trap in ACS rule-out: ESC 0/1h algorithm cutoffs (0h <5 ng/L + Δ1h <4 ng/L) are validated for Siemens ADVIA Centaur hs-cTnI; Roche Elecsys hs-cTnT and Abbott ARCHITECT hs-cTnI have completely different validated cutoffs; applying wrong cutoffs to wrong assay = false rule-out → missed MI → patient death; ALWAYS confirm your institution's assay before applying cutoffs

• Wellens syndrome — never stress test: biphasic (Type A) or deep symmetric (Type B) TWI in V2–V3 in pain-free state = critical proximal LAD stenosis; ECG during pain shows STE (these patients often present pain-free); troponin may be completely normal; exercise stress test contraindicated — risk of anterior STEMI during test; pattern indicates plaque instability, not ischemia; urgent cardiology + cath

• PROMISE (2015, NEJM) + SCOT-HEART (2018, NEJM): CTCA equivalent to functional testing for safety in stable chest pain (PROMISE); CTCA ↓fatal MI at 5 years via identifying subclinical CAD → ↑statin/aspirin prescribing (SCOT-HEART; 2.3% vs 3.9% fatal MI; NNT 62); CTCA is preferred anatomic rule-out in appropriate low-intermediate risk patients

• Single negative troponin at <3h is never sufficient: troponin peaks 6–24h post-MI; 10–15% of MIs have normal troponin at 3h from onset; always require 2 serial troponins ≥3h apart OR validated hs-cTn 0/1h algorithm to safely exclude; the most common premature discharge error in chest pain evaluation

• Stent thrombosis zero-tolerance protocol: any CP within 30 days of PCI → cath lab; do not obtain serial troponins, stress tests, or CTCA; every minute of coronary occlusion post-PCI = 1.9 million cardiomyocytes lost; 20–40% mortality; activate cath lab while taking history

• Common mistake — diagnosing MSK based on reproducible chest wall tenderness: ~7% of confirmed ACS patients have reproducible chest wall tenderness; this finding has no negative predictive value for ACS; always obtain ECG + serial troponin before attributing chest pain to musculoskeletal cause; labeling ACS as MSK = missed STEMI/NSTEMI

• Common mistake — giving thrombolytics for inferior STEMI without considering dissection: RCA ostium involvement in aortic dissection produces classic inferior STEMI pattern on ECG; thrombolytics in dissection = catastrophic hemorrhage; brief clinical assessment (tearing quality, BP differential, widened mediastinum) before activating STEMI protocol in inferior MI; if any suspicion of dissection → CTA first