L22 Flashcards
Define myocardial ischemia
O2 demand > O2 supply to heart muscle
Define myocardial infarction
Thrombosis due to rupture of atherosclerotic plaque
3 factors that determine heart O2 demand
- HR
- Contractility
- Wall tension - P and volume
Name the 6 steps of the ischemic cascade
- ↓O2 to heart muscle
- Switch to anaerobic metabolism
- Relaxation abnormalities - diastole
- Contraction abnormalities - systole
- ST changes to EKG
- Angina
Myocardial ischemia might present as angina. What are the 3 types of angina?
- Chronic, stable = angina pectoris
- Variant = prinzmetal’s
- Unstable (this is also under the umbrella of acute coronary syndrome)
Symptoms of stable angina
Visceral, deep pain
Self described around the sternum
“Elephant on my chest”
Provocation & palliation of stable angina
Onset: stress - physical or emotional
Relieved by stopping stress
Stable angina is usually due to…
Atherosclerosis
Existing block leads to less BF during activity –> stress induced pain
Remember the 6 risk factors for atherosclerosis
- High cholesterol
- HTN
- Smoking
- Diabetes
- Age
- Family history CHD
EKG for stable angina
ST depression when episodic
Describe variant angina
- Presentation
- EKG changes
Spontaneous chest pain - at rest
EKG = transient ST elevation
Cause variant angina + treat
Coronary artery spasm
Treat w/ nitrates or CaCBs
What are the 3 conditions under the umbrella term “acute coronary syndrome”?
= conditions that result of plaque rupture and some de 1. NSTEMI 2. STEMI NSTEMI and STEMI are both types of MI 3. Unstable angina
What is STEMI
MI w/ ST elevation
Transmural infarct = through entire myocardial thickness
Usually result of complete occlusion of that area’s blood supply
What is NSTEMI
Non-ST elevated MI
May see ST depression
Subendocardial infarction = less invasive
Presentation of acute coronary syndromes
- Crushing chest pain at rest
- Gripping chest = Levine sign
- Sweating
What is a white thrombus? What kind of occlusion does it cause?
Platelet clot
Partially occlusive - b/c platelets, think soft!
Causes unstable angina or NSTEMI
What is a red thrombus? What kind of occlusion does it cause?
Fibrin clot
Complete occlusion - big hard clot
Causes STEMI
How do women present with MI?
Atypically:
Shoulder/neck pain
Dyspnea
Fatigue
Tests to diagnose MI for pt presenting with chest pain
- Resting EKG - if clean get exercise EKG to bring out perfusion issues
- Troponin levels
+/- Coronary arteriogram
What EKG finding indicates prior MI?
Q wave
Dip before the QRS
= No electrical activity somewhere = dead tissue
If you see a Q wave in leads 2, 3, avF - which coronary artery is affected?
RCA
What are concerning findings for exercise test:
- HR onset
- Recovery: late vs early
- ST changes?
- Hypo or hypertension?
HIGH RISK RESULTS: - Early onset bradycardia - Late recovery - over 7 mins - ST depression - Hypotension Findings for AGGRESSIVE APPROACH
What is a cold spot on myocardial perfusion tests? Findings for ischemic vs infarcted tissue?
Cold spot = not taking up radioisotope b/c no BF = ischemic area
Ischemic = transient cold spot
Infarcted tissue = fixed cold spot
2 drugs for pharm stress test
Dobutamine - B1 agonist - increases contractility
Regadenoson = adenosine receptor agonist (duh!) = arteriolar dilation
What are findings on echo for ischemia vs infarction?
Ischemia = transient abnormality
Infarction = fixed
Same as perfusion, different test
Treat CAD
- Revascularize
- PCI = angioplasty +/- stent
- CABG - Meds
- Nitrates = vasodilators
- BBs
- Ca CBs
GOALS reduce O2 consumption of myocardium
Vessels that can be used for CABG
Saphenous vein graft
Internal mammary artery
Describe nitrate mechanism
Dilation veins»_space; arteries
Pool blood in circulation
Decrease preload
Describe nitrate effects on heart
Vasodilate coronary arteries to increase subendocardial flow (to possibly ischemic areas)
Less wall tension/pressure because decrease preload
Net: increased HR and contractility
SE nitrates
Headache - drop BF to brain as blood pools peripherally
Hypotension - SO much venous pooling
Why do we give BB for MI?
Decreases mortaility
Why do we give BB for angina pectoris?
↓HR and contractility
Net ↓O2 consumption
Which BBs are cardio specific?
B1s A-M blockers aka B1s are the 1st 1/2 alphabet Acebutolol Atenolol Betaxolol Carvedilol Esmolol Lavetalol Metroprolol
SEs BBs
Fatigue HF Excessive bradycardia Worsen diabetic control Bronchoconstriction
Which type of angina are Ca CBs helpful with?
Variable
Mechanism of CaCBs for ACS therapy
Both vasodilators
Non-DHPs - ↓HR
DHPs - ↓BP
Most important CAD med
Aspirin
Is immediate opening of the occlusion more significant for MIs w/ elevated or depressed ST segments?
STEMI
Indicates complete occlusion - get back profusion ASAP
Should you give fibrinolytics or go to the cath lab?
Under 90 mins - cath lab
Otherwise fibrinolytics
