Stable Ischemic Heart disease Pathophysiology Flashcards
What is ischemic heart disease caused by?
Caused by an obstructive atherosclerotic plaque in at least one of the coronary vessels that vascularize the heart
- causes reduced myocardial oxygen supply
Differentiate between Chronic stable angina CSA and Acute coronary syndrome ACS
Cause?
Sx?
CSA
- Caused by stable plaque
- Sx: occasional upon exertion, stable pattern of chest pain
ACS
- caused by VULNERABLE plaque –> ruptures
- Sx: ACUTE impairment of myocardial blood supply
What is prinzmetal’s Angina caused by?
Cardiac pain NOT caused by an evident cardiac lesion
- related to dec O2 supply due to coronary vasopasm
What is angina (ischemic heart disease) a result of?
an imbalance between myocardial oxygen supply and demand
What factors affect SUPPLY of myocardial oxygen?
- Coronary blood flow (vasodilation)
- Oxygen extraction (ability of tissue to extract O2)
- Oxygen availability (O2 saturation, Hgb concentration)
What factors affect DEMAND of myocardial oxygen? (3)
Heart rate
Contractility (digoxin, ccb)
Systolic wall tension (afterload, resistance to overcome to get blood out of heart)
What is PREload? What is it related to?
How much the heart is stretched at the end of the diastole
- related to the sacromere length of the smooth muscle at the end of diastole
What 4 factors is preload related to?
- sacromere LENGTH
- Left ventricular end RADIUS
- LVE VOLUME
- LVE PRESSURE
at lower preload volume what happens to stroke volume? At higher preload?
low preload volume = Inc Stroke volume
high preload volume = no effect on stroke volume
What does the frank-starling mechanism state? What is the “normal” operating point?
Increased venous return increases LVEDPressure and volume, thereby increases PRELOAD
this results in inc stroke volume (SV)
LVEDpressure 8 mmHg and SV 70 mL/beat
Define afterload. Another name?
Pressure that must be overcome for heart to eject blood
- AKA systolic wall tension
- closely related to Aortic pressure
What is the Law of Laplace equation relationship
- Afterload (wall stress) is proportional to pressure/radius
- Afterload is inversely related to hypertrophy (wall thickness)
What occurs to afterload and O2 demand when preload is increased?
Inc preload = inc afterload = inc O2 demand
What occurs to afterload and O2 demand when wall thickness (hypertrophy) increases?
Inc hypertrophy = dec afterload = dec O2 demand
What occurs to afterload and O2 demand when ventricular dilation occurs?
Dec wall thickness = Inc Afterload = Inc O2 demand
How does athersclerotic lesions affect blood flow in exercise. Explain the difference vs healthy patient
Healthy (left)
- At rest: R2 is able to perfuse the heart adequately
- In exercise: small dilation in R2 -> to maintain perfusion to the heart
Stenosis/plaque present (right)
- At rest: blockage causes R2 to dilate at rest (to keep up normal perfusion)
- In exercise: R2 is already dilated to the max (no way to further reduce resistance)
- High demand -> supply cannot increase further -> ischemia
What is the most causes of Ischemic Heart Disease
Atherosclerotic cardiovascular disease
When do symptoms of exertional angina show?
When 50% of lumen has plaque (stenosis)
If the plaque ruptures/thrombosis occurs what is it called?
Unstable angina/ MI
- Acute coronary syndrome
Is symptom severity (i.e more limitation) equal worse outcomes? What kind of test was it done on
Yes
- observational results (associative relationship but still significant)
What are risk factors for CVD? (6)
- Smoking
- Inc BP
- DM
- Inc Age
- Inc Cholesterol (LDL)
- dec HDL
What are predisposing factors for CVD
- Obesity
- physical inactivity
- Family history
- Ethnic characteristics
- Psychosocial factors
What are symptoms of IHD
Duration?
Location?
Characteristics?
Cause?
Relieved by?
ECG changes?
Heavy weight on chest
- squeezing, pressure, heaviness, weight, vise-like aching, burning, tightness
Duration? 0.5-30 min
Location? Sternum
Characteristics?
- Radiates to shoulder, neck, jaw, inner arm, epigastrium (occur without chest component), band-like discomfort
Cause? By effort/exercise
Relieved by? Nitroglycerin
ECG changes? ST-depression, T-inversion
What do Atypical, noncardiac symptoms of angina look like? More common in females
Onset?
How long it lasts?
Relieved by?
Pain
- pleuritic, sharp, pricking, knife-like, pulsating, lancinating ,choking
Chest wall
- positional, tender to touch, radiation patterns highly variable
Random onset
Lasts seconds, minutes, hours, or all day
Variable response to NTG
