Non-ST-elevation myocardial infarction
Background
- 33% with confirmed MI have no chest pain on presentation (especially older, female, DM, CHF)
- 5% of NSTEMI will develop Cardiogenic Shock (60% mortality)
- Age >65 with MI and anemia had 33% reduction in 30 day mort if transfused to keep HCT >30
- Association between quantity of troponin and risk of death
- NSTEMI includes Type 2 -Type 5 biomarker elevations
Types of Myocardial Infarction
- Type 1: Ischemic myocardial necrosis due to plaque rupture ( ACS)
- Type 2: Ischemic myocardial necrosis due to supply-demand mismatch, e.g. coronary spasm, embolism, low or high blood pressures, anemia, or arrhythmias.
- Type 3: sudden cardiac death (no cTr values)
- Type 4: procedure related, post PCI or stent thrombosis ( cTr > 5X Decision Level).
- Type 5: post CABG (cTr > 10X Decision Level).
Clinical Features
Risk of ACS
Clinical factors that increase likelihood of ACS/AMI:[1][2]
- Chest pain radiating to both arms > R arm > L arm
- Chest pain associated with diaphoresis
- Chest pain associated with nausea/vomiting
- Chest pain with exertion
Clinical factors that decrease likelihood of ACS/AMI:[3]
- Pleuritic chest pain
- Positional chest pain
- Sharp, stabbing chest pain
- Chest pain reproducible with palpation
Gender differences in ACS
- Women with ACS:
- Less likely to be treated with guideline-directed medical therapies[4]
- Less likely to undergo cardiac catheterization[4]
- Less likely to receive timely reperfusion therapy[4]
- More likely to report fatigue, dyspnea, indigestion, nausea or vomiting, palpitations, or weakness,[4] although some studies have found fewer differences in presentation[5]
- More likely to delay presentation[4]
- Men with ACS:
- More likely to report central chest pain
Factors associated with delayed presentation[4]
- Female sex
- Older age
- Black or Hispanic race
- Low educational achievement
- Low socioeconomic status
Differential Diagnosis
Chest pain
Critical
- Acute coronary syndromes (ACS)
- Aortic dissection
- Cardiac tamponade
- Coronary artery dissection
- Esophageal perforation (Boerhhaave's syndrome)
- Pulmonary embolism
- Tension pneumothorax
Emergent
- Cholecystitis
- Cocaine-associated chest pain
- Mediastinitis
- Myocardial rupture
- Myocarditis
- Pancreatitis
- Pericarditis
- Pneumothorax
Nonemergent
- Aortic stenosis
- Arthritis
- Asthma exacerbation
- Biliary colic
- Costochondritis
- Esophageal spasm
- Gastroesophageal reflux disease
- Herpes zoster / Postherpetic Neuralgia
- Hypertrophic cardiomyopathy
- Hyperventilation
- Mitral valve prolapse
- Panic attack
- Peptic ulcer disease
- Pleuritis
- Pneumomediastinum
- Pneumonia
- Rib fracture
- Stable angina
- Thoracic outlet syndrome
- Valvular heart disease
- Muscle sprain
- Psychologic / Somatic Chest Pain
- Spinal Root Compression
- Tumor
Evaluation
- Non-STEMI ECG + positive troponin
- CK-MB and myoglobin are not helpful[6]
- Angiography indicated for:
- Recurrent angina/ischemia with or with out symptoms of CHF
- Elevated troponins
- New or presumably new ST-segment depression
- High-risk findings on noninvasive stress testing
- Depressed LV function
- Hemodynamic instability
- Sustained V-tach
- PCI within previous 6 mo
- Prior CABG
Management
- Dual antiplatelet therapy and antithrombotic therapy is mainstay of treatment
- Medical management vs cath determined by level of risk for future cardiovascular events
Antiplatelet
- Aspirin
- Recommended dose is 325mg chewed
- Reduces death from MI by 12.5 → 6.4%
- Should be used in all ACS unless contraindicated (eg Anaphylaxis)
- In pts with true ASA allergies, substitute Clopidogrel[7]
- Clopidogrel (see drug link for specific age and indication-related dosages)
- Give in addition to ASA
- Mortality benefit with NSTEMI (CURE trial: Decrease in cardiovascular death, MI or stroke by 9.3-11.5%)
- Main risk and contraindication is bleeding
- GPIIb/IIIa Inhibitors
- Eptifibatide, abciximab, tirofiban
- Benefit only for patients undergoing PCI
- Administer at time of PCI, not in the ED
Antithrombotics
- Give heparin or enoxaparin along with ASA (Class 1A evidence)
- Enoxaparin (Lovenox)
- 1mg/kg subq BID
- AHA recommends for moderate & high risk Unstable angina/NSTEMI unless CABG within 24hr
- Safer than UFH
- ESSENCE trial showed 20% decrease in death, MI or urgent revascularization with LMWH
- Adjust for CrCl<30ml and extremes of weight
- No need to monitor labs
- Unfractionated Heparin
- Bolus 60-70u/kg (max 5000) followed by infusion of 12-15u/kg/hr (max 1000/hr), goal ptt 45-75s
- Consider if patient likely to undergo PCI/CABG within 24hr of admission or in setting of renal failure
- Hirudin
- Approved only for patients with HIT
Other
- Oxygen
- Use only if SpO2 <90%
- Nitrates (decrease preload)
- Administer sublingual NTG every 5 min x3 for continuing ischemic pain and then assess need for IV NTG (AHA ACA Level I)
- Use cautiously in inferior MI or if on sildenafil
- Not shown to decrease MACE
- Analgesia
- β-blockers
- Start PO dose within 24 hours (Do not give IV β-blocker in ED (AHA ACA Level III: Harm))
- Goal HR is 50-60
- Contraindicated if HR<50 or SBP<90, acute CHF, low flow state, or PR>240ms
- Decreases inotropic and chronotropic response to catecholamines
- Use diltiazem if cannot use beta-blocker (nifedipine clearly harmful)
- ACE inhibitor
- Start short-acting (captopril) within 24 hours of admission
- Reduces RR of 30 day mortality by 7%
- Those with recent MI (especially anterior) and LV dysfunction benefit most
- Transfusion
- Transfuse to keep hemoglobin >10
- Thrombolytics
- Not indicated (only useful for STEMI)
Disposition
- Admit
Prognosis
NSTEMI TIMI Score[8]
- Used to estimate percent risk of all-cause mortality, new/recurrent MI, or need for revascularization at 14 days
- Age >65 yrs (1 point)
- Three or more risk factors for coronary artery disease: (1 point)
- family history of coronary artery disease
- hypertension
- hypercholesterolaemia
- diabetes
- current smoker
- Use of aspirin in the past 7 days (1 point)
- Significant coronary stenosis (stenosis >50%) (1 point)
- Severe angina (e.g., >2 angina events in past 24 h or persisting discomfort) (1 point)
- ST-segment deviation of ≥0.05 mV on first ECG (1 point)
- Increased troponin and/or creatine kinase-MB blood tests (1 point)
points | % risk of mortality, MI, or need for revascularization |
---|---|
0 | 5% |
1 | 5% |
2 | 8% |
3 | 13% |
4 | 20% |
5 | 26% |
6 | 41% |
See Also
- Unstable Angina - NSTEMI Guidelines
- Acute coronary syndrome (main)
- ST-segment elevation myocardial infarction (STEMI)
- Unstable angina
- Cocaine-associated chest pain
External Links
References
- ↑ Body R, Carley S, Wibberley C, et al. The value of symptoms and signs in the emergent diagnosis of acute coronary syndromes. Resuscitation. 2010;81(3):281–286. PMID: 20036454
- ↑ Panju AA, Hemmelgarn BR, Guyatt GH, et al. The rational clinical examination. Is this patient having a myocardial infarction? JAMA. 1998;280(14):1256–1263. PMID: 9786377
- ↑ Swap CJ, Nagurney JT. Value and limitations of chest pain history in the evaluation of patients with suspected acute coronary syndromes. JAMA. 2005;294(20):2623–2629. PMID: 16304077
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Mehta LS, et al. Acute myocardial infarction in women: A scientific statement from the American Heart Association. Circulation. 2016; 133:916-947.
- ↑ Gimenez MR, et al. Sex-specific chest pain characteristics in the early diagnosis of acute myocardial infarction. JAMA Intern Med. 2014; 174(2):241-249.
- ↑ AHA ACA - NSTEMI ACS Guidelines 2014View Online
- ↑ CAPRIE Steering Committee.. A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee. Lancet. 1996 Nov 16;348(9038):1329-39.
- ↑ Antman, Elliot et al. The TIMI Risk Score for Unstable Angina/Non–ST Elevation MI A Method for Prognostication and Therapeutic Decision Making. JAMA. 2000;284(7):835-842. doi:10.1001/jama.284.7.835. PDF