Non-ST-elevation myocardial infarction
Background
-CAD kills more Americans each year than any other dz
-Study w/ 400,000 pts w/ confirmed MI showed 33% had NO CP on presentation to ED!! (esp older, female, dm and chf)
-5% of NSTEMI will develop cardiogenic shock (60% mort!)
-Non-diagnostic ECG helpful to risk stratify, pts w/ confirmed MI but nl ECG had only 50% mort in house of pts w/ diagnostic ECGs (circulation,2002)
-Pt age >65 w/ MI and anemia had 33% reduction in 30 day mort if transfused to keep HCT >30 (NEJM 10/01)
-Clear link has been established between quantity of troponin and risk of death (tpi not up in CRI)
Diagnosis
- ACS (clinical evidence of ischemia)= UA, NSTEMI (UA sx w/ postive enzymes) and STEMI
- Angina is considered Unstable with 1 or more:
1) occurs for the 1st time
2) occurs at rest
3) accelerating frequency or severity
- ECG is key, but is entirely normal in 8% of all confirmed MI's; normal or non-specific in 50% UA/NSTEMI; but accuracy improves with prior ECG & serial tracings
- Intensity of Rx should be based on likelihood that a pts Sx are d/t an acute coronary thombosis
TIMI RISK STRATIFICATION SCORE
- 1 point for each
- Age ≥65 years
- Presence of at least three risk factors for CHD
- Prior coronary stenosis of ≥50 percent
- Presence of ST segment deviation on admission ECG
- At least two anginal episodes in prior 24 hours
- Elevated serum cardiac biomarkers
- Use of aspirin in prior seven days
- Likelihood of mortality, new or recurrent MI, or require revascularization at 14 days
- Score of 0/1 - 4.7 percent
- Score of 2 - 8.3 percent
- Score of 3 - 13.2 percent
- Score of 4 - 19.9 percent
- Score of 5 - 26.2 percent
- Score of 6/7 - 40.9 percent
Treatment
1) Anti-ischemia
a) Oxygen
- ACC recs O2 for sats <90% (evidence indeterminant)
b) Nitrates
- no mortality benifit
- dilates coronary arts, decr preload, slight decr afterload. theoretically leads to decr O2 demand of heart.
- use of viagra within 24 hr can lead to profound and prolonged vasodilation and death!
- B-block to avoid reflex tachy.
c) B-Blockers
-Goal HR is 50-60.
- Contraindicated if HR<50 or SBP<90, acute CHF or pr >240ms
-(Decr progression from UA to MI by 13%(jama 10/88))
- decr inotropic and chronotropic response to catechols, thus decr O2 consumption.
- Decr progression from UA to MI by 13%(jama 10/88)
- Contraindicated if HR<50 or SBP<90, acute CHF or pr>240ms.
- use dilt or verap if cant use b-block (nifedipine clearly harmful)
- no IV BB in ED, PO within 24 H
d) ACE Inhibitor
- start short-acting (captopril) within 24 hours of admission
- reduces RR of 30 day mort by 7% (circulation 6/98)
- those w/ recent MI (esp ant) and LVdysf(x) benefit most.
e) Transfusion
- transfuse to keep Hb >10 (NEJM 10/01; 33% reduction in 30 day mort)
f) MSO4
- may use if pain after 3 doses of NTG.
- reduces pain and theoretically can decr HR and SBP and O2 demand
- use associated with higher mortality in MI pts (and cause of higher mortality in CHF exacerbation pts)
2) Antiplatelet
(plaque rupture=exposed endothelium=platelets=thrombus)
a) ASA
-rec dose is 160-325mg chewed.
-reduces death from MI from 12.5-6.4% (circualtion 10/02)
- inhibits COX-1, reducing thromboxane A2
- should be used in all ACS unless contraindicated (far better than any new drugs we have)!! (circualtion 10/02).
b) Clopidogrel (plavix, 300mg po then 75qd)
- in addition to ASA
-used over ticlopidine b/c faster onset & less s/e (ttp,aplastic anemia etc).
-mortality benifit with NSTEMI
- ADP antagonist, noncompet inhibits platelet adp receptor.
- main risk and contraind is bleeding (stop 7days before cabg)
- CURE trial showed decr in CV death, MI or stroke from 11.5% to 9.3% w/ this drug.
c) GPIIb/IIIa(-) = Integrillin (eptifibatide)
- blocks this receptor on platelet.
- oral forms incr mort!!!
- high-risk pts benefit most.
- Integrillin (eptifibatide) studied in PURSUIT trial, found 30 day death or MI decr from 15.7% to 14.2%.
- incr ICH not seen w/ use.
- benefit if early pci is planned, and ? to no benefit if PCI not planned
- reserved (if no pci) for positive tpi or isch/ecg changes despite asa, lovenox, b-block etc.
3) Antithombotics
(in 2002 ACC/AHA mgt of UA/NSTEMI includes class1A evidence to anticoagulate w/ heparin or lovenox along w/ asa +/- plavix)
a) Heparin vs. Lovenox
-class1A evidence to anticoagulate w/ heparin or lovenox along w/ asa
+/- plavix in NSTEMI
i) Unfractionated Heparin
-Bolus 60-70u/kg (max 5000), followed by infusion of 12-15u/kg/hr (max 1000/hr), w/ goal ptt 45-75s
-activates antithrombin which prevents thrombus propagation but does NOT cause lysis
-Hirudin is approved only for pts w/ HIT.
ii) LMWH: enoxaparin (lovenox)
-1mg/kg sc BID
-safer (20% decr in death,MI or urgent revasc w/ LMWH vs UFH)
-AHA recomends for mod & high risk UA/NSTEMI unless CABG w/in 24hrs
-adjust for CrCl<30ml and extremes of weight
- No needd to monitor labs!
-ESSENCE showed 20% decr in death, MI or urgent revasc w/ LMWH vs UFH.
- Thrombolytics in the case of UA/NSTEMI have been shown to increase the risk of MI, with no benefit, and all the risks of TNK!
4) Angiography, if
- Hemodynamic instability or cardiogenic shock
- Severe left ventricular dysfunction or heart failure
- Recurrent or persistent rest angina despite intensive medical therapy
- New or worsening mitral regurgitation or new ventricular septal defect
- Sustained ventricular arrhythmias
5) Early (within 24hr) referral for angiography
- TIMI risk score greater than 2
- New or presumably new ST segment depression
- Elevated cardiac enzymes
- Prior PCI within six months or prior CABG
- Recurrent angina or ischemia at rest or with low level activity despite intensive antiischemic therapy
- LVEF <40 percent
See Also
Cards: Cocaine CP
Source
Adapted from Pani, Donaldson, Lampe, EM Practice, UpToDate