Cardio Week 5 - CAD & Ischemia, Atherosclerosis, Ischemic Vessel Disease Flashcards
How do coronary arteries provide nutrients to the heart muscle tissue?
Via perfusion
Rules of fluid dynamics
- Fluids flow from an area of high pressure to low pressure
- Fluids follow the path of least resistance
Major determinants of myocardial blood flow
- Diastolic blood pressure
- Vasomotor tone
- Resistance to flow
What is the primary driving force moving blood into myocardial tissue?
Diastolic blood pressure
What plays a role in determining volume of blood passed along to tissue?
Vasomotor tone
What is resistance to flow commonly caused by?
Atherosclerosis
What does elevations in diastolic pressure indicate?
- More resistance to flow
- The heart has to work harder to pump the blood through the vessels
What does increased resistance cause?
- Increased work load, which increases oxygen demand of the heart
What’s important when talking about myocardial perfusion?
The balance of oxygen supply and demand
What happens when demand exceeds supply of oxygen?
Ischemia or tissue death
What is the outer layer of the arteries and what is its role?
- Adventitia
- The basic support structure or basement membrane
What is the middle layer of the artery and its function?
- Media
- Made up of multiple layers of smooth muscle
- Function is to make adjustments to luminal diameter
What is the inner layer of the artery and its function?
- Intima or endothelial layer
- Arterial endothelium is designed to be selectively permeable to macromolecules of the size of low density lipoproteins
What is most likely to accumulate in the intima?
- Lipoproteins
- Fibrinogen
Atherosclerosis
- Accumulation of material beneath the tunica intima or inner layer of the arterial wall
- Develops in response to endothelial injury
- Advanced plaques are composed of lipid and thrombus
What material does atherosclerosis mostly consist of?
- Macrophage cells
- Debris
- Lipids
- Cholesterol
- Fatty acids
- Calcium
- Variable amount of fibrous connective tissue
What are the development phases of atherosclerosis?
- Atherosis
- Sclerosis
Atherosis
- Fatty streak of lipid-laden macrophages and smooth muscle cells
- Cholesterol permeates the endothelium and deposits between the layers
Sclerosis
- Inability of the blood vessel to be compliant (reduces its compliance) or to adjust the lumen with
- Organization of “fibrous cap” of thrombi
What organs/areas can also be damaged by atherosclerosis?
- Brain (CVA)
- Kidneys (Renal artery; stenosis or atherosclerotic renovacscular disease)
- Lower Extremities (Peripheral vascular disease)
Why are coronary vessels so susceptible?
- Coronary vessels have short branches under high pressure
- Flow is more likely to become turbulent
Risk factors for atherosclerosis
- Smoking
- Poorly controlled diabetes mellitus
- High velocity/turbulent flow
- Hypertension
- Hyperlipidemia
- Systemic inflammation
Major non modifiable cardiovascular disease risk factors
- Heredity
- Increased age
Major modifiable cardiovascular disease risk factors
- Cigarette/tobacco smoking
- Physical inactivity
- High blood pressure (over 140/90)
- High blood cholesterol levels
What is the best predictor for high blood cholesterol levels?
Ratio of total cholesterol to HDL
Total cholesterol - normal, borderline and high
- Normal = < 200 mg/dL
- Borderline = 200 - 239 mg/dL
- High = >/= 240 mg/dL
LDL - normal, borderline, high levels
- Normal = < 130 mg/dL
- Borderline = 130-159 mg/dL
- High = > 160 mg/dL
HDL - Low and Cardioprotective levels
- Low = < 40 mg/dL
- Cardioprotective = > 60 mg/dL
Negative effects of smoking
- Enhances atherosclerosis
- Increased LDL production
- Increased work of the heart - partially by increasing BP
Other risk factors for cardiovascular disease
- Diabetes
- Obesity = BMI >/= 30 kg/m2
- Gender
- Stress
- Diet
What is diabetes mellitus?
- Metabolic disorder - Type 2 DM
- Start with high blood glucose
- Accelerated atherosclerosis
- Inflammatory response
Ischemic vessel disease in the heart
- Angina
- Myocardial infarction
Ischemic vessel disease in the brain
- TIA = Transient ischemic attack
- CVA = Cerebrovascular accident
Ischemic vessel disease in the lower extremities
- Intermittent claudication
- PAD
Causes of vessel narrowing and decreased perfusion
- Atherosclerosis
- Thrombus
- Vasospasm
What is a thrombus?
- Occludes vessel
- Piece breaks off (embolus)
What is a vasospasm?
- Hyperplasia of smooth muscle cells - advanced atherosclerosis, prone to spasm
- Can decrease size of the lumen vessel
Prinzmetal angina
Variant angina associated with ST-segment elevation, at rest, and no associated with any preceding increase in myocardial oxygen demand
Angina definition
Distress/pain of the chest
What causes angina ?
- Classic symptom of ischemic heart conditions
- Secondary to imbalance of coronary oxygen delivery (usually due to decreased blood flow but not always)
- May be due to increased demands of oxygen placed on the heart
- Decreased blood flow
- Anemia
Stable (Typical) Angina
- Caused by fixed atherosclerotic lesion
- Reduces reserve for coronary blood flow
- Not present at rest
- Occurs when oxygen demand is increased
- Reproducible in terms of exertion (intensity and length of time)
- Relieved by rest and administration of nitrates
Unstable Angina
- Implies worsening of atherosclerotic process
- Progressive in terms of - severity of pain, less exertion required to elicit it, may progress to pain at rest
- Considered emergency
- Requires intervention before myocardial infarction occurs
- Typically caused by thrombosis of a coronary plaque
Prinzmetal’s Angina aka Variant Angina
- Caused by coronary vasospasm due to endothelial dysfunction
- More difficult to diagnose due to its unpredictable onset, occurring even at rest (irrespective or cardiac demand)
What is Ergonovine stimulation?
- Used to diagnose suspected prinzmetal angina
- Illicits coronary spasm and makes it occur predictably so they can image and locate it
What is myocardial perfusion - ischemia?
- Sudden cardiac death
- Acute coronary syndrome
- Chronic stable angina
What is acute coronary syndrome (ACS)?
- Unstable angina
- Non ST-segment elevation
- ST-segment elevation
Unstable Angina - EKG, Cardiac Enzymes and Echo
EKG: Normal or ischemia
Cardiac Enzymes: Normal
Echo: Normal EF
Non ST-segment Elevation, Myocardial infarction - EKG, Cardiac Enzymes, Echo
EKG: ST-segment depression
Cardiac Enzymes: Abnormal
Echo: May be abnormal
ST-segment Elevation, Myocardial infarction - EKG, Cardiac Enzymes, Echo
EKG: ST-segment elevation
Cardiac Enzymes: Abnormal
Echo: Abnormal
Right Coronary Artery - Location of Infarct, ECG changes, Common Complications
Location: Inferior
ECG changes: II, III, aVF
Complications: Risk of atrioventricular block and/or arrhythmias, 50% have right ventricular infarct
Left Main - Location of infarct, ECG changes, Common Complications
Location: Anterior and lateral
ECG changes: V1-V6, I, aVL
Complications: Pump dysfunction or failure
Left Anterior Descending (LAD) - Location of infarct, ECG Changes, Common Complications
Location: Anterior
ECG: V1-V4
Complication: Pump dysfunction or failure
Circumflex - Location of Infarct, ECG Changes, Common Complications
Location: Lateral
ECG Changes: V5, V6, aVL, I
Complications: None specific
Typical symptoms of acute coronary syndrome in men
“Elephant sitting on their chest”
- Pain in L side of upper back, neck and arm
- Men < 55 are 6x more likely than women to have MI
Acute coronary syndrome in women
- First sign is typically angina
- Higher risk if had preeclampsia
- Younger women < 55 have higher mortality rates
- Pain low sternum - right below breast, upper middle back, R shoulder, pain mid sternum - right above breast, pain L side of chest
What is the 2nd leading cause of death in women < 55 y/o?
Coronary artery disease
Progression of myocardial necrosis
- Necrosis begins in a small zone of the myocardium beneath the endocardial surface in the center of the ischemic zone
- Area that depends on the occluded vessel for perfusion is the “at risk” myocardium
Non-STEMI diagnosis
- Rupture of coronary plaques —> partial occlusion of coronary artery —> subendocardial wall infarction
Non - STEMI diagnosis - EKG
- ST segment depression
- T wave inversion
Non-STEMI diagnosis - Cardiac enzymes
- Positive
- Troponin T and I
- Creatine kinase - myocardial bound
ST- elevation MI: diagnosis
Rupture of coronary plaques —> thrombus/clot —> total occlusion of a coronary artery —> transmural infarction
ST-elevation MI: Diagnosis - EKG
- ST segment elevation
ST-elevation MI: Diagnosis - Cardiac enzymes
- Elevated cardiac enzymes
- Troponins
Echocardiogram
- Wall motion abnormalities
- Detected in 90-95% of all transmural MIs
- Detected in 80-90% of all subendocardial MIs
- Specificity of 80-90%
