ACUTE CORONARY SYNDROMES Acute MI and Unstable Angina

1、acute coronary syndromes: acute mi and unstable angina tintinalli chapter 50 september 20, 2005 acute coronary syndrome (acs) nischemic heart disease accounts for 500,000 deaths annually in the u.s. ncad and myocardial ischemia contribute to 5 million er visits yearly for chest pain n15% of pts with

2、 chest pain will have acute mi and 25-30% will have unstable angina acs na term used to describe pts with acute cp and other symptoms of myocardial ischemia nduring the initial exam, often not possible to determine whether permanent damage to the myocardium has occurred only in retrospect after seri

3、al ecgs or cardiac markers can the distinction b/w ami or ua be made pathophysiology nacs is caused by secondary reduction in myocardial blood flow due to coronary arterial spasm disruption of atherosclerotic plaques platelet aggregation or thrombus formation at site of atherosclerotic lesion thromb

4、us formation natherosclerotic plaque formation occurs through repetitive injury to vessel wall nwhen plaque ruptures, potent thrombogenic substances are exposed to platelets nthese platelets respond by adhesion, activation, and aggregation thus initiating thrombus formation in the coronary vessels n

5、the extent of o2 deprivation and thus clinical presentation of acs depend on the limitation of o2 delivery by thrombus adhering to fixed, fissured, or eroded plaques stable angina nischemia occurs only when activity induces o2 demands beyond the supply restrictions imposed by a partially occluded co

6、ronary vessel noccurs at a relatively fixed and predictable point and changes slowly over time natherosclerotic plaque has not ruptured thus there is little superimposed thrombus acs natherosclerotic plaque rupture and platelet-rich thrombus develop ndegree and duration of o2 supply- demand mismatch

7、 determines whether reversible myocardial ischemia w/o necrosis (unstable angina) or myocardial ischemia w/ necrosis (myocardial infarction) clinical features nmain symptom of ischemic heart disease is chest pain need to characterize its severity, location, radiation, duration, and quality ask about

8、 associated symptoms: n/v, diaphoresis, dyspnea, lightheadedness, syncope, palpitations nreproducible chest wall tenderness is not uncommon npatients with acs may complain of easy fatigability nusually an ami is accompanied by more prolonged and severe chest discomfort and more prominent associated

9、symptoms angina pectoris nexercise, stress, or cold environment classically precipitates angina nduration of symptoms typically nanterior - nanterolateral - nqs deflections in v1-v3, possibly v4 nrs defection in v1, q waves v2-4 or decr in amplitude of initial r wave in v1-v4 nq waves in v4-6, i, av

10、l ecg criteria and ami nlateral - ninferior - ninferolateral - ntrue posterior - nright ventricular - nq waves in i, avl nq waves ii, iii, avf nq waves ii, iii, avf, and v5-v6 ninitial r waves in v1-v2 0,04s and r/s ratio 1 nq waves ii, iii, avf may take months to resorb ndressler syndrome post ami

11、syndrome occurs 2 to 10 weeks after ami pts presents with chest pain, fever, and pleuropericarditis right ventricular infarction nusually seen as a complication of an inferior infarction approximately 30% of inferior wall mi involve the rv npresence of rv infarction is associated with significant in

12、crease in mortality and cardiovascular complications other complications nleft ventricular thrombus formation narterial embolization nvenous thrombus npulmonary embolism npostinfarction angina ninfarct extension *these are diagnoses to think about when a pt presents to the er after recent discharge

13、from the hospital postprocedure chest pain npts who present with symptoms of acs shortly after angioplasty or stent placement should be assumed to have abrupt vessel closure nsubacute thrombotic occlusion after stent placement occurs in approximately 4% of pts 2 to 14 days after procedure this less

14、common than closure after angioplasty npts with chest pain syndromes after cabg may have abrupt vessel closure symptoms of recurrent ischemia can be confused with post-ami pericarditis disposition nall patients with acute chest pain need to be evaluated for the possibility of acs pts are admitted to

15、 appropriate level of care depending on their risks nresults of prior cardiac catheterization are very useful for risk stratification cardiac cath results pts with previously documented minimal stenosis (25%) or normal coronary arteriograms have excellent long-term prognosis more than 90% of these p

16、ts are free from mi 10 yrs later a recent cardiac cath (within last 2 yrs) with normal or minimally diseased vessels almost eliminates the possibility of acs due to atherosclerosis doesnt eliminate vasospasm or small vessel dz stress tests results nwhen pts complete all stages of the stess protocol,

17、 have no ecg changes and normal imaging studies, exercise testing can r/o acute ischemic syndromes with sensitivities b/w 80- 90% nif all criteria are not met, stress test have poor sensitivity questions? n1. which of the following is false about new rbbb? a. occurs in 2% of ami pts b. occurs most c

18、ommonly with inferior wall mi c. often leads to complete av block d. associated with increased mortality questions? n2. true or false: inferior wall mi can result from occlusion of left circumflex a. or rca n3. true or false: left ventricular free wall rupture occurs in 10% of ami fatalities usually 3-4 weeks after initial infarct questions? n4. true or false: b type natriuretic peptide has a high specificity in diagnosing chf n5. true or false: reproducible chest wall pain rules out acs. nanswers: b, true, false, false,