Acute Coronary Syndrome (ACS) consists of spectrum of illness which includes:
- Unstable angina
- NSTEMI or Acute Non Q web MI
- Acute MI
Conventionally ACS refers to UA and NSTEMI
- Plaque rupture → Platelet adhesion to expose collagen in coronary arteries → Activation of platelets → Platelet aggregation → thrombus formation → ACS
- Coronary spasm → Decreased Myocardial circulation → ACS
Stable and Unstable Plaque are the 2 forms of plaque in pathogenesis of ACS.
- Stable Plaque are more hemodynamically significant and produces reversible MI. It usually manifest as chronic stable angina.
- Unstable Plaque are hemodynamically insignificant, angiographically unimpressive and prone to rupture causing occlusive thrombus and development of MI.
Most AC event develop upon atheromatous plaque.
- Rest Angina- occurs without any exertion or provocation and genreally lasts for 20 minutes or longer.
- Increasing Angina- means ‘ Distinctly more frequent ,longer duration and /or decreased threshold’ in a patient with previously diagnosed Angina.
- Severity increases by 1 or more CCS class atleast upto CCS class III.
- NSTEMI differs from UA in severity and both may be indistinguishable at presentation. Ischemia can be severe enough to damage the myocardium though Cardiac markers may not be raised upto several hours of onset of pain. Only 1/4 of these patients will develop Acute Q wave MI.
ECG/ EKG – ECG must be done within 10 minutes of arrival in ER of all suspected cases. ECG must be repeated as per required and when pain recurrs. 0.05mV of ST segment change in limb leads and 0.1 mV in other leads are significant. T wave changes may be seen. A normal ECG does not rule out ACS completely.
- CKMB, more specific CKMB1 and 2. CKMB2 : CKMB1 ratio >1.5 or CKMB2 level >1 U/L suggest Myocardial injury. rise within 4 hours after MI, peak at 18-24 hours, and subside over 3-4 days. CKMB levels within reference range does not exclude myocardial necrosis.
- Troponin I and T are equally sensitive and indicates focal necrosis. No CKMB but raised Trop levels in Angina suggests microinfarctions.
- Myoglobin- negative results are helpful.
- LDH is a late marker.
Other Biochemical Markers- CRP, IL-6,sCD40 ligand, myeloperoxidase, pregnancy-associated plasma protein-A, choline, placental growth factor, cystatin C, fatty acid binding protein etc have been suggested.
- Chest X-Ray- pulmonary edema, aneurysms.
- ECHO- limited value, detects wall motion abnormalities. LVH and Valvular HD may be detected.
- Recent advances include CT coronary angiography and CT coronary artery calcium scoring.
- Technetium-99m (99mTc) tetrofosmin single-photon emission computed tomography (SPECT)
Coronary Angiography Video Animation-