Acute coronary syndrome
- 1 Etiology/causes
- 2 Classification
- 3 Diagnosis
- 4 Treatment
- 5 Prognosis
- 6 References
In medicine and cardiology, acute coronary syndrome (ACS) is a collection of signs and symptoms due to inadequate oxygenation of the heart muscle, the myocardium, usually due to coronary artery disease. ACS includes myocardial infarction ("heart attack") and angina.
Pain relief and proper oxygenation is the core of ACS treatment. When the root causie is angina, the temporary cause of ischemia should be reversed. For myocardial infarction, more vigorous interventions are appropriate if they can prevent damage to myocardium.
Rupture seems more likely to occur during the morning hours. Rupture may be precipited by inflammation from non-cardiac infections. Rupture may be triggered by vigorous exercise among individuals who do not ordinarily do vigorous exercise.
Approximately 15% of NSTEMI and 2% of STEMI patients have no obstruction of coronary vessels and in about half of these patients, spasm can be induced of a coronary artery.
The role of emotional stress was supported in a study of the incidence of coronary events in the Munich area during the 2006 FIFA World Cup Football (soccer) championship. The incidence of coronary events was higher during the match, especially for people who had pre-existing coronary disease. Similar findings have been reported in Los Angeles, California during the American Super Bowl. Stress, via increases in unhealthy behaviors, was also identified as more important than hypertension or C-reactive protein level in predicting coronary events.
Stress-induced (takotsubo) cardiomyopathy
|Electrocardiogram||Serum biomarkers||Typical appearance of culprit vessel at angioscopy|
|Unstable angina||"ST-segment depression or prominent T-wave inversion"||Normal|| Nonocclusive grayish-white thrombus|
| Non-ST segment elevation myocardial infarction
|"ST-segment depression or prominent T-wave inversion"||Elevated|| Primary NSTEMI: Nonocclusive grayish-white thrombus|
Secondary NSTEMI: no thrombus
| ST segment elevation myocardial infarction
|ST-segment elevation||Elevated|| Occlusive reddish thrombus |
|Q-wave myocardial infarction||Q-waves||Elevated|| Occlusive reddish thrombus |
Unstable angina is defined as "precordial pain at rest, which may precede a myocardial infarction".
A myocardial infarction is defined as "gross necrosis of the myocardium, as a result of interruption of the blood supply to the area". It is usually caused by occlusion of an epicardial coronary artery.
Non-ST segment elevation myocardial infarction (NSTEMI)
ST segment elevation myocardial infarction (STEMI)
History and physical examination
A helpful finding is exact reproduction of chest pain upon palpating the chest. In a patient whose other findings also suggest a non-cardiac course of their chest pain, this finding can help rule out coronary disease.
The electrocardiogram is a key part of decision making. For example, the presence of ST changes and Q-waves determines therapy.
A normal electrocardiogram has been reported not to exclude acute coronary syndrome, even when the electrocardiogram is taken during pain. Although this study defined unstable angina as either a coronary stenosis or positive stress test and so likely includes patients without true acute coronary syndrome as defined by the American Heart Association, the study was still not able to show that a normal electrocardiogram helped exclude a NSTEMI.
Isolated abnormalities of T-waves also confers worse prognosis.
Computed tomographic cardiac angiography
Clinical prediction rules
The Thrombolysis in Myocardial Infarction risk score for unstable angina or non-ST elevation myocardial infarction is a clinical prediction rule that may detect patients with chest pain who are at increased risk of acute coronary syndrome
A second clinical prediction rule, the Acute Cardiac Ischemia Time-Insensitive Predictive Instrument (ACI-TIPI) can help diagnose patients with chest pain and has been shown to improve medical care in a randomized controlled trial. The ACI-TIPI was studied up through 1993 before troponin assays were widely available and thus does not incorporate the troponin. However, the ACI-TIPI should retain its ability to use the medical history and the EKG to decide who should be observed for serial troponin levels. It is unclear why this role is not recognized by the ACC/AHA guidelines. One reason may be that the ACI-TIPI is patented.
Another clinical prediction rule is the Vancouver Chest Pain Rule. In an independent validation study, "a lower sensitivity and higher specificity when applying the Vancouver Chest Pain Rule...as compared to the original study.". 
Patients without contraindication should receive anticoagulation with unfractionated heparin. The risk of bleeding can be estimated with a clinical prediction rule (http://www.crusadebleedingscore.org/).
Unstable angina or NSTEMI
Platelet ADP receptor blockers
Thienopyridine ADP blockers such as clopidogrel, ticlopidine, and the prodrug prasugrel may help especially for patients undergoing percutaneous coronary intervention (PCI). Ticagrelor may be better than clopidogrel for some patients.
Glycoprotein IIb/IIIa inhibitors
Percutaneous transluminal coronary angioplasty
Among patients with unstable angina or NSTEMI and without ST-segment elevation (but may have other EKG evidence of ischemia such as ST-segment depression of ≥1 mm or transient ST-segment elevation or T-wave inversion of >3 mm) may benefit from early invasive management (percutaneous transluminal coronary angioplasty) if:
- Thrombolysis in Myocardial Infarction (TIMI) risk score of 3 or more, elevated myocardial enzymes, or elderly patients according to the TACTICS randomized controlled trial.
- A GRACE risk score is more than 140 according to the TIMACS randomized controlled trial.
Three clinical prediction rules can help prognosticate with similar ability:
- GRACE Risk Score
- The Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) risk model
- Thrombolysis in Myocardial Infarction (TIMI) risk score
These rules can help estimate prognosis and guide decisions.
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