Ischemia Flashcards
Determinants of O2 supply
O2 content (hemoglobin level, O2 saturation)
O2 extraction
Coronary blood flow (perfusion pressure, resistance)
Determinants of O2 demand
Myocardial contractility
Heart rate
Wall stress (BP, ventricular radius, wall thickness)
Myocardial stunning
- ventricular dysfunction that persists after reperfusion despite no irreversible damage and restoration of normal blood flow
- myofilament alteration that involves impaired calcium responsiveness
- repair in 7-14 days
Reperfusion injuries
- stunning
- no reflow
- reperfusion arrhythmias
- fatal reperfusion injury (myocyte cell death)
hibernation
- chronic ischemic tissue can lead to myocytes that are alive but have reduced fxn
- can by improved if blood flow improves
PET scan
- Positron emission tomography
- used to identify conversion to anaerobic metabolism
Acute Coronary Syndrome risk factors
tobacco, DM, dyslipidemia, family hx of CAD, HTN, PAD, renal failure, inflammatory ds, obesity, sedentary lifestyle
Treat stable angina symptoms
- nitrates, calcium channel blockers, B-blockers
- Revascularization-PCI, CABG
Stable angina-prevent adverse events
- lifestyle changes
- aspirin
- statins
- ACE-Is
- Thioenopyridine
- CABG if left main coronary artery ds or 3 vessel ds and decreased LV fxn
EKG
- MI results in changes in the polarity, shape, and amplitude of T wave and ST displacement
- during exercise stress test, may see ST depression or elevation
Exercise stress test
- most common test to dx atherosclerotic coronary artery disease
- horizontal or down sloping depression or elevation of ST segment -> significant, obstructive CAD
- most useful if intermediate pre-test probability
Nuclear stress imaging
- demonstrate regional myocardial blood flow
- intravenous injection of radionuclide tracer taken up by myocardium in proportion to blood flow
echocardiography
determine wall motion/contractility
Intravascular ultrasound
- images arteries
- sensitive method to detect full extent of atherosclerosis
Fractional flow reserve
- define functional significance of a lesion
- pressure transduced distal to lesion is divided by pressure proximal to lesion (healthy=1;
coronary CT angiography
-identifies obstructive plaques and non-obstructive calcifications
invasive coronary angiography
- gold standard for dx atherosclerotic CAD and assessing severity
- inject radio-opaque contrast into arteries and record flow
- demonstrates only lumen of artery and is not sensitive to early, preclinical athero
TIMI variables
- age >65
- Presence of 3+ CAD risk factors
- Prior coronary stenosis of >50%
- ECG ST segment deviation
- 2+ angina episodes in prior 24 hours
- Elevated serum cardiac biomarkers
- use of aspirin in prior 7 days
0-2 TIMI variables
- 4.7-8.3% risk
- stress test
3+ TIMI variables
- 13-41% risk
- invasive cardiac cath
aspirin
- anti-platelet therapy
- irreversibly blocks COX-1 in platelets-can’t metabolize arachidonic acid to thromboxane A2 (promotes platelet aggregation)
P2Y12 receptor blocker
- irreversibly inhibits ADP receptor on platelets
- inhibits GpIIbIIIa complex activation
GpIIb-IIIa inhibitor
-directly prevents fibrinogen cross linking
Anti-thrombins
- unfractionated and low molecular weight heparin, direct thrombin inhibitor, factor Xa inhibitor
- final goal: block thrombin formation
