Patient with Coronary Artery Disease/Acute Coronary Syndrome Flashcards
What causes myocardial ischemia?
Myocardial O2 demands are greater than supply
How does myocardial ischemia differ from myocardial infarction?
Ischemia - inadequate oxygen supply to meet demands
Infarction - irreversible necrosis of myocardium that results from prolonged ischemia
What factors determine myocardial oxygen supply?
Coronary blood flow
What factors determine myocardial oxygen demand?
Heart rate
Contractility
Wall tension (proportional to pressure and volume)
What are the events of the myocardial ischemic cascade,?
Ischemia
Switch from aerobic to anaerobic metabolism
Relaxation abnormalities (energy dependent process)
Contraction abnormalities (energy dependent process)
ECG ST changes
Angina
What are the clinical presentations that result from myocardial ischemia?
Chronic stable angina
Prinzmetal’s (variant) angina
Acute coronary syndrome
Describe the character and location of chronic stable angina
“Visceral” deep discomfort, touches sternum
What precipitates and relieves chronic stable angina?
Precipitates: stress (emotional or exertional)
Relieved by: stopping the stress
What is the most common cause of typical effort-related angina?
Fixed atherosclerotic lesion narrows a coronary artery (O2 demands > O2 supply)
What are the major risk factors for coronary artery disease?
Hypercholesterolemia Hypertension Smoking Diabetes Age Family history
What are the 3 clinical characteristics of Prinzmetal’s angina?
Spontaneous (rest) pain
Transient ST segment elevation
Absence of effort pain/not induced by exertion
What is the cause of Prinzmetal’s angina?
Coronary artery spasm
What is the treatment of Prinzmetal’s angina?
Nitrates or Calcium channel blockers
What are the three subgroups of acute coronary syndrome (acute myocardial ischemia)?
STE MI
NSTE MI
Unstable angina
Which of the three presentations of acute coronary syndrome have actual myocardial tissue death?
STEMI
NSTEMI
Tissue death makes it a myocardial infarction, otherwise is termed unstable angina.
What is the common cause of acute coronary syndromes?
Atherosclerotic plaque rupture, thrombus formation, and coronary occlusion
What are typical symptoms of acute coronary syndrome?
Chest pain at rest
Levine’s sign (fist to chest)
Diaphoresis (sweating)
Which type of MI (STEMI or NSTEMI) has greater coronary vessel occlusion?
STEMI (red thrombus is more occlusive and longer lasting than white thrombus)
What type of thrombus typically causes NSTEMI/unstable angina?
White thrombus
What causes a white thrombus to form?
Released collagen causes platelet aggregation
What type of thrombus typically causes STEMI?
Red thrombus
What causes a red thrombus to form?
Released tissue factor causes red blood cells and fibrin to aggregate
How do women present with acute coronary syndrome?
Atypical: Shoulder or neck pain, dyspnea, fatigue
What does ST segment depression indicate?
Subendocardial ischemia (inner wall) Transient
What does ST segment elevation indicate?
Transmural ischemia or infarction
What does pathologic Q wave indicate?
Prior infarction
Which EKG leads will indicate involvement of inferior wall of the heart and which coronary artery does this suggest?
2, 3, avF
right coronary artery (RCA)
Which EKG leads will indicate involvement of lateral wall of the heart and which coronary artery does this suggest?
1, avL, V6
left circumflex coronary artery
Which EKG leads will indicate involvement of anterior wall of the heart and which coronary artery does this suggest?
V2-V5
left anterior descending (LAD) coronary artery
What cardiac enzymes are released upon acute myocardial cell death?
Myoglobin
Creatine kinase
Creatine kinase-MB
Troponin T & I
Which cardiac enzyme is most sensitive and specific in making a diagnosis of MI and why?
Troponin
Because it stays in circulation for 7-10 days, can tell if patient had an event recently
What qualifies as a positive EKG exercise stress test?
ST segment depression of 1 mm or more
What are high risk markers during an EKG exercise stress test?
Early onset low HR (7 min)
Large amount of ST depression (>2 mm)
Multiple leads involved - suggest large area of ischemia
Hypotension - if BP does not go up when exercising, indicates large area of ischemia (walls can’t contract, stroke volume goes down)
What should you do if a patient exhibits high risk markers during an EKG exercise stress test?
Take them to the cath lab for revascularization
What does a transient cold spot indicate in a nuclear exercise test?
Ischemia
What does a fixed cold spot indicate in a nuclear exercise test?
Infarction
How can you pharmacologically do a stress test?
Dobutamine (beta1 agonist - increase BP and HR)
Adenosine (arteriolar vasodilation - increased flow to normoxic areas)
What does a transient abnormality during an exercise echo indicate?
Ischemia
What does a fixed abnormality during an exercise echo indicate?
Infarction
What are two revascularization techniques?
PCI (percutaneous coronary intervention) = angioplasty +/- stent
CABG (coronary artery bypass graft)
- Usually done with saphenous vein or internal mammary artery (IMA is better)
What drug is the cornerstone of therapy for coronary artery disease?
Nitrates
How do nitrates help in coronary artery disease?
Cause peripheral venous dilation –> blood pooling in legs –> decrease in ventricular volume (preload) –> decrease wall tension –> decrease O2 demands
Can also increase subendocardial flow
What are side effects of nitrates?
Headache
Hypotension
Reflex tachycardia
Tolerance
What should you do when patient gets syncope due to decreased BP after taking nitrates?
Raise legs to get blood back to head
How do beta blockers help in coronary artery disease?
Decrease HR
Also decrease contractility and wall tension
What are side effects of beta blockers?
Fatigue
Heart failure
Excessive bradycardia
Bronchoconstriction
When should you use calcium blockers for coronary artery disease?
When other drugs (nitrates and beta blockers) don’t work
What clinical presentation of acute myocardial ischemia are calcium blockers especially helpful for?
Prinzmetal’s angina
What is the most important medication in coronary artery disease?
Aspirin
What is the “wavefront” phenomenon of necrosis?
The longer a vessel is occluded, the more necrosis of myocardium
Inner endocardium is most vulnerable and necrosis will begin there and spread out to the epicardium
When are fibrinolytics indicated?
Angina with ST segment elevation within 12 hours of onset
Angina with Left bundle branch block (LBBB - cannot interpret ST segment) within 12 hours of onset
Should you use fibrinolytics with NSTEMI or unstable angina?
No
When should you give fibrinolytics before going to the cath lab to revascularize?
If time to cath lab is >90 minutes
