293 Ischemic Heart Disease Flashcards
Condition in which there is an inadequate supply of blood and oxygen to a portion of the myocardium
Ischemic Heart Disease (IHD)
Occurs due to imbalance between myocardial oxygen supply and demand
IHD
Most common cause of myocardial ischemia
Atherosclerotic disease of epicardial coronary artery/-ies
Most common, serious, chronic, life-threathening illness in US
IHD
Factors associated with emergence of IHD
- Genetic
- High fat and energy rich diet
- Smoking
4 Sedentary lifestyle
Powerful risk factors for IHD
- Obesity
- Insulin resistance
- Type 2 Diabetes mellitus
Major determinants of myocardial oxygen demand (MVO2)
- Heart rate
- Myocardial contractility
- Myocardial wall tension (stress)
Determines the oxygen-carrying capacity of the blood
- Inspired level of oxygen
- Pulmonary function
- Hemoglobin concentration and function
Requirement to have adequate supply of oxygen to myocardium
- Satisfactory level of oxygen-carrying capacity of the blood
- Adequate level of coronary blood flow
Blood flow through the coronary arteries in what phase of cardiac cycle
Diastole
Arteries responsible for the total coronary resistance to flow
- large epicardial arteries (Resistance 1 = R1)
- prearteriolar vessels R2
- arteriolar and intramyocardial capillary vessels R3
Major determinant of coronary resistance
R2 and R3
What dominates and controls the normal coronary circulation?
OXYGEN requirement of the heart
Mechanism of myocardial ischemia in severe left ventricular hypertrophy (due to aortic stenosis)
- Myocardial oxygen demands markedly increased
2. Coronary blood flow may be limited
T or F: Extremely severe anemia can cause myocardial ischemia.
False.
Rarely cause myocardial ischemia BY ITSELF but may lower threshold for ischemia in patients with moderate coronary obstruction
Abnormal constriction or failure of normal dilation of the coronary resistance vessels can cause ischemia, producing angina. What condition is this?
Microvascular angina
Major site of atherosclerotic disease
Epicardial coronary arteries
Major risk factors for ATHEROSCLEROSIS
- High LDL
- Low HDL
- Cigarette smoking
- Hypertension
- Diabetes mellitus
Normal function of vascular endothelium
- Local control of vascular tone
- Maintenance of antithrombotic surface
- Control of inflammatory cell adhesion and diapedesis
Effects of dysfunctional vascular endothelium
- Inappropriate constriction
- Luminal thrombus formation
- Abnormal interactions between blood cells (monocytes, platelets)
- Activated vascular endothelium (proinflammatory and prothrombotic)
Collection of fat, smooth muscle cells, fibroblasts and intercellular matrix
Atherosclerotic plaque
State of diabetics which make them vulnerable to atherosclerosis
HYPERcoagulability and
HYPOfibrinolysis
Site of predilection for atherosclerotic plaques to develop
Sites of increased turbulence in coronary flow (e.g. branch points)
Reduction in diameter of epicardial artery by what percentage causes limitation of ability to increase flow to meet increased myocardial demand
50%
Reduction in diameter of epicardial artery by what percentage causes reduced blood flow at rest and cause myocardial ischemia at rest or with minimal stress
80%
2 processes that occur when a plaque is exposed in the blood after rupture or erosion
- Platelets are activated and aggregate
- Coagulation cascade is activated = deposition of fibrin strands
Product: Thrombus
Mechanism of myocardial ischemia
Thrombus (platelet aggregates + fibrin strands) traps RBC and reduce coronary blood flow = clinical manifestations of ischemia
T or F: Collateral vessels when formed can provide sufficient blood flow to sustain the myocardium at rest and during conditions of increased demand
False
Can sustain myocardium at rest BUT NOT during conditions of increased demand
Duration of time that the damages of total occlusion are reversible
Less than or equal to 20 minutes
More than that, it is permanent with subsequent myocardial necrosis
A common presenting manifestation of IHD
Sudden death
Patients with IHD presenting with cardiomegaly and heart failure
Ischemic cardiomyopathy
T or F: In ischemic cardiomyopathy, patients can have no symptoms before the development of heart failure
True
This is the asymptomatic phase of IHD
T or F: In IHD, once you have entered the symptomatic phase, reverting back to asymptomatic stage will be impossible.
False
Patient may revert from symptomatic to asymptomatic or even die suddenly
The sign describing angina as squeezing, central, substernal discomfort and placing a clenched fist over the sternum
Levine’s sign
T or F: Chest discomfort in angina can also radiate to the trapezius muscles
False
Myocardial ischemic discomfort DOES NOT radiate to trapezium muscles; pattern is more typical of PERICARDITIS