Ischemic Heart Disease

what does the left main coronary artery supply

intraventricular septum and anterior wall of left ventricle

what does the circumflex artery supply

posterolateral left ventricle and anterolateral papillary muscle

what does the right coronary artery supply

right ventricle

what does the posterior descending artery supply

posterior and inferior walls of left ventricle

ischemic heart disease

imbalance between myocardial oxygen supply vs demand; caused mostly by atherosclerotic lesions in epicardial coronary arteries and microvascular disease

non-obstructive triggers of ischemic heart disease

increased demand - left ventricular hypertrophy (LVH), increased preload/afterload, tachycardia

decreased supply - anemia, hypoxia, hypotension, vasospams

clinical manifestations of ischemic heart disease

angina (stable, variant, unstable), dyspnea, myocardial infarction, sudden death, chronic ischemic heart disease

symptoms of angina

substernal/precordial chest discomfort, “something sitting on my chest”, can radiate (shoulders, neck, jaw, epigastric)
associated symptoms: dyspnea, nausea, diaphoresis

stable angina

associated with activity, dissipates with rest

printzmetal angina

younger patients, transient vasospam, associated with stimulant drug use (cocaine)
causes: hyperreactivity, ANS dysfunction, endothelial dysfunction, allergy

unstable angina

at rest or increasing in frequency, disruption of plaque, needs urgent intervention

sudden cardiac death

unexpected death, no symptoms or <24 hours after onset of symptoms
causes: coronary artery disease (most common), congenital heart disease in younger patients

mechanism: arrhythmia

chronic ischemic heart disease

ischemic cardiomyopathy, progressive CHF from cumulative ischemic injury, often seen post-MI

Pathogenesis of myocardial infarction

acute plaque change → exposure of contents → platelet activation/microthrombi → vasospasm → coagulation cascade → vessel occlusion

time is muscle - outcome depends on duration, location, severity, collaterals

reversible MI

minutes, decreases contractility, cell swelling, glycogen depletion

irreversible MI

greater than 20-30 minutes of severe ischemia, leads to necrosis

myocardial necrosis

begins subendocardium and progresses transmural; necrosis half thickness in 2-3 hrs and fully transmural by 6 hours; initial sign: membrane disruption and protein leak (biomarkers)

complications of MI

contractile dysfunction: LV failure, RV failure

arrhythmias: bradycardia, AFib, AV block, VFib, ventricular tachycardia

rupture: free wall, septum, papillary muscle

ventricular aneurysm: late complication, leads to thrombus, arrhythmia, HF

mural thrombus: embolic risk

papillary muscle dysfunction

chronic ischemic cardiomyopathy

STEMI

MI from ST elevation, transmural, full thickness of myocardium

NSTEMI

MI from ST depression, subendocardial, partial thickness

type 1 NSTEMI

classic MI due to obstruction

type 2 NSTEMI

from supply-demand mismatch without obstructive lesion

Biomarkers used for MI diagnosis

EKG, troponin (gold standard), CK-MB

best practice for diagnosis of MI

troponin and EKG

troponin

increased 2-4 hours, lasts 7-12 days, sensitive and specific; trend in NSTEMI, false highs in CKD

CK-MB

rises in 4-6 hours, peaks 16-30 hours, not used clinically; false positives in skeletal muscle injury, post-op, hypothyroid, marathoners, chronic renal failure

emergency department tools in risk assessment of MI

HEART score (most common), ED-ACS (sensitive, not specific), TIMI (older, not used)

Long-term tools in risk assessment of MI

Framingham, QRISK, ACC/AHA pooled equations

ACC/AHA 2013 Statin Guidelines

4 groups benefiting most: 1. clinical ASCVD 2. LDL >190 3. age 40-75 with diabetes and LDL 70-189 4. age 40-75 with LDL 70-189 and ASCVD risk >7.5%

total cholesterol

LDL + HDL + (TG/5)

low density lipoprotein (LDL)

bad cholesterol, target of statins; lipoprotein(a) = higher CAD risk

high density lipoprotein (HDL)

good cholesterol; increases with exercise, smoking cessation, omega-3, red wine, purple fruits, weight loss

Triglycerides (TG)

part of lipid panel