Handwritten Video lecture on Myocardial Infarction/Angina for the USMLE Step 2. Will be covering Pathogensis, Clinical Signs and Symptoms, ECG and Diagnosis as well as Management
Coronary Artery Disease occurs when there is an imbalance between oxygen supply of the heart with the oxygen demands of the heart.
ETIOLOGY/CAUSES
Decreased Oxygen supply - Atherosclerosis, Prinzmetal Angina, Arterial Thrombi, Coronary Emboli, Aortitis, Dissection
Increased Oxygen Demand - Hypertrophy, Catecholamines, Tachycardia
RISK FACTORS
Modifiable - LDL and HDL, Hypertension, Diabetes, Obesity, Smoking
Non-Modifiable - Family History, Male, Greater than 64 years old
CLINICAL SIGNS AND SYMPTOMS
Pain - tightness, squeezing, knot in chest, heavy weight, toothache and jaw ache, lump in the throat. Exacerbated with exertion and recumbency, sleeping. Percipitated by heavy meal, cold, sexual activity. Radiation to epigastric, shoulders down to fingers, lower jaw, subscapular space in the back. Relieved with nitroglycerin, rest. Usually occurs in the early morning due to increase sympathetic acitivity and platelet aggregation
Angina Equivalent - dyspnea, nausea, fatigue. Usually seen in elderly and diabetic.
PHYSICAL EXAMINATION
Tachycardia and hypertensive due to pain.
Auscultation may show S3/S4 or paradoxical S2 split.
Levine's Sign will show clenched fist on the chest.
ECG Findings
Subendocardial ischemia shows ST Depression or T wave inversion.
Transmural Infarct shows ST Elevation or hyperacute T wave.
Pathological Q wave develops along with R wave depression. Usually takes a few hours to develop.
After a few days there is a much deeper Q wave and t wave inversion.
CARDIAC BIOMARKERS
Troponin T and Troponin I are more specific than CKMB. Troponin peaks at 12 hours and last for weeks. CKMB rises in a 2-3 hours and goes down in 2-3 days.
STRESS ECG
Patient walks on treadmills while being monitored by ECG until reach 85 percent of maximum heart rate. Positive if symptoamtic, ECG changes, drop in blood pressure, ventricular tachycardia.
ECHO
Shows wall function and may show akinesia or hypokinesia. Used for patients with chronic angina, prior MI, pathologic Q wave and Heart Failure
Electron Beam CT
Calculate Calcium to calculate aggetson score which is prognostic
Coronary Angiography
Detects which arteries is occluded.
MANAGEMENT
First 10 minutes - Check for hemodynamic stability. Ask for recent bleeding neurological condition, and aortic dissection. Use of cocaine or Ergotamine (prinzmetal angina). Determine if RV or LV Infarction. Initial treatment consists of aspirin, clopidogrel, B-blocker, ACE Inhibitor, Statin, and Morphine. Nitroglycerin. Oxygen is only given if saturation is less than 94 percent.
CLASSIFICATION
STABLE ANGINA - Pain only at rest. Patient should be stress ECG or Echo. If positive than perform angiography. Minimize risk factors by decreasing LDL, increasing HDL, statins, beta-blockers
ACUTE CORONARY SYNDROME - Constant Pain
UNSTABLE ANGINA - No elevation of cardiac markers and No ST Elevation. Anti-coagulate, B-Blockers, Nitroglycerin.
TIMI SCORE -
Age greater than 65, Markers, ECG Changes, Risk Factors, Ischemia in 24 hours, CAD, Aspirin in last 7 days. Score of 0-4 is low risk and can be treated medically. 5-7 shoudl undergo cathetrization.
NSTEMI - No ST elevation, but positive cardiac biomarkers
STEMI
These patients require PCI within 90 minutes. Especially if high risk. If symptoms greater than 24 hours, than fibrinolysis is ineffective because clot is too strong.
FIBRINOLYSIS - not preffered due to high bleeding risk. Use aleteplate, tenecteplase. Only indicated if PCI is unavailable. If fibrinolysis doesn't work than must do rescue PCI.
CORONARY ARTERY BYPASS GRAFT - Done after complicated PCI, Left main Artery involvement or three vessels involved. Severely LV ejection fraction. Or complications such as septal rupture, papillary muscle rupture and aneurysm.
NON-ACUTE MANAGEMENT
Continue anti-platelets - aspirin, clopidogrel
Nitrates - prophylactic
Anti-coagulants - risk of emboli
Increase ambulation