Flashcards in CVPR 312 Cardiac Pathophysiology / Lecture 2 / Ischemic Heart Disease Deck (123):
Ischemic Heart Disease (IHD) is Characterized by changes in the cardiac muscle that occur when ?
Coronary arterial oxygen supply is inadequate to meet myocardial metabolic demands.
Coronary sinus SvO2 =
Inadequate blood supply (circulation) to a local area due to blockage of the blood vessels to the area.
An oxygen deficiency in body tissues
Absence of oxygen
a bluish skin tint caused by inadequate oxygenation of the bloodstream.
Myocardial Ischemia (MI) can be du to the following 2 things?
- Acute coronary thrombosis
- Coronary atherosclerosis
Most Common cause of death in the industrialized world
- 500,000 die annually
- 12 million affected in US
Risk Factors for Myocardial Ischemia
Hyperlipidemia …Cholesterol (LDL)
Most frequent cause of coronary blood flow and myocardial ischemia ?
Coronary vasoconstriction / spasm Typically occurs at or near plaque and ?
Coronary emboli often results from ?
thrombi from LV or prosthetic valves
MAP < 45-55 mmHg = loss of coronary autoreg
In the precence of CAD pressure even higher than ___ may be needed to prevent ischemia.
Causes of Myocardial Ischemia (cont.)
- Aortic Valve stenosis
- Hypertrophic cardiomyopathy
- Inflammatory dz of coronary arteries
- Congenital anomalies of the coronary circulation
- Extremely raid heart rate
Imbalance between O2 Sypply & O2 demand
Predisposes patients to ?
- Myocardial ischemia
- Ventricular dysfunction
- Electrical Instability
- Possible death from dysrhythmias or heart failure
At rest the myocardium extracts about ___________ of the O2 from coronary arterial blood
Consequently, any increased O2 demand must be met by
increases in blood flow
In the myocardial oxygen supply - demand balance patients may develop myocardial ischemia if:
1.) Myocardial oxygen supply falls short of demand
2.) Myocardial oxygen demand exceeds supply
In regards to the coronary arterial blood supply, the
LEFT coronary artery supplies what?
Anterior & Lateral portions of the LV
In regards to the coronary arterial blood supply, the
RIGHT coronary artery supplies what?
RV & posterior LV
(80-90% of people)
% of Coronary venous blood that comes from the LV to the Coronary Sinus ?
75% of total
From the RV to the > ________ > RA
anterior cardiac vein
_____ _____ empty directly into all chambers (very small amount)
Normal coronary blood flow at rest?
4 - 5 %
Normal coronary blood flow
- Phasic in nature esp. in LV
- Low flow during systole (compression)
- High flow during diastole (relazed state)
Normal coronary artery structure starting from the outside.
Chest pain caused by fleeting deficiency in oxygen delivery to myocardium
Drug treatment of Angina Pectoris
- Nitroglycerin = vasodilator
- Beta blockers = block sympathetic beta adernergic
The degree of coronary intraluminal obstruction correlates with anginal presentation. If strenuous exercise or strong emotion = chest pain (clasical angina), then we can conclude what ?
Intraluminal Obstruction of > 50%
The degree of coronary intraluminal obstruction correlates with anginal presentation. If the patient often has angina at rest, then we can conclude what?
Intraluminal Obstruction of > 80%
Coronary vasospasm (no CAD) occurs typically at rest (morning hours)
Compensatory mechanisms for O2 supply/demand mismatch
- Coronary arteriolar vasodilation
- Coronary collateral circulation
- Anerobic metabolism
What is the primary controller of Coronary arteriolar vasodilation:
Blood flow is regulated by local arteriolar
What is the major factor that controls coronary blood flow?
What percentage of oxygen is removed as it goes through the heart?
Coronary blood flow is directly proportional to ?
If there is a small occlusion in coronary blood flow, what happens?
collateral flow may double to affected area over several days.
If there is a GRADUAL occlusion in coronary blood flow, what happens?
Collaterals develop progressively with the disease.
What happens when sclerotic process overwhelms the collateral capacity?
Under resting conditions, cardiac muscle normally consumes ____ ____ to supply most of its energy instead of carbohydrates .
What % of energy is derived from fatty acids?
Under what conditions must cardiac metabolism call on glycolysis mechanisms for energy ?
Under ANAEROBIC or ISCHEMIC conditions.
Glycolysis consumes large amounts of ____ _____ and at the same time forms large amounts of LACTIC ACID in the cardiac tissue ?
What is one of the causes of cardiac pain under cardiac ischemic conditions?
LACTIC ACID build up in the cardiac tissue
Vagal stimulation by Acetylcholine causes what DIRECT effect?
Indirect stimulation is a far more important role. Sympathetic Stimulation causes what?
↑Contractility = ↑ metabolic demand > sets off local blood flow regulatory mechanisms for DILATING
Sympathetic Stimulats and their receptors ?
a & b receptors
Vagal stimulation with its release of acetylcholine poduces:
> ↓ Cardiac Oxygen Consumption
= Indirectly constrict the coronary arteries
Typical Angina evoked by:
- Cold/heat exposure
- Sexual Intercourse
Relieved by Rest
- Reproducible and Predictable in onset
- No relationship to exertion
- New onset of typical angina
- Increasing in insensity or occurs at rest
Type of Angina that varies in symptoms ?
ECG Evaluation of an MI ?
- ST may be elevated or depressed
- T waves may be tall
ECHO Evaluation of an MI ?
Wall motion abnormalities
Thallium Scan Evaluation of an MI ?
Absence of thallium “cold spot” MI
Lab Evaluation of an MI ?
Creatine Kinase (CK-MB) 30 – 220 U/L.
Lactate dehydrogenase (LDH) 100 - 220 U/L
Myoglobin (Mb) 30 – 90 µg/mL
Leading cause of death in industrialized countries?
Ischemic heart disease leads to what
-Sudden Cardiac Death
-Chronic Heart Failure
Natural changes in the following:
- CONNECTIVE TISSUE
- DIAMETER of ARTERY.
pathologic phenomenon occurring in the following:
- femoral arteries
Narrowing and hardening of the arteries leads to imbalance between what?
Supply and Demand which leads to ISCHEMIA.
Ischemic Heart Disease is a result of what
How is Ischemia detected?
- Symptoms (angina)
- ECG (indirectly)
Cross Section of an artery on how atherosclerosis develops, starting from the inside?
- Internal Elastic Tissue
- Smooth Muscle Cells
- External Elastic Tissue
- Connective Tissue
Inflammatory response is the result of
proliferation of tissue within the arterial wall which may result in obstruction of blood flow.
What are the causes of atherosclerosis?
↑ BP - turbulent blood flow
- tobacco smoke
- glycosylated substances
Response to injury hypothesis ?
Endothelium is injured > Platelets & monocytes adhere to endothelium > Release growth factors.
Monocytes become Macrophages & take up LDL & SMC's.
Smooth muscle proliferation & migrate from medial to intimal layer.
Migration to the intima smooth muscles with lipids form fatty streaks AKA ?
Fibromuscular layer with cholesterol core ?
Atherosclerosis affects what vessels?
Intermediate and Large arteries
Fatty lesions that develop on the inside surface of the artery.
Results of atheromatous plaques ?
↓ Lummen Size
↓ Blood Flow
How do atheromatous plaques begin?
they begin by deposition of cholesterol crystals in the intima and smooth muscle.
Minimal intrusion into vessel lumen ?
Artherosclerosis can result in ?
- Hypertensive Heart Disease
- Coronary Artery Occlusion
- ↑ cholesterol
- ↑ LDL
Muscle cells die after
1 hour of ischemia
↑ in Cardiac Output results mostly from ?
Circulatory response to exercise challenge causes an increase in arterial pressure by ?
- Vasoconstriction of arterioles
- ↑ contractility of the heart
- ↑ filling pressures
A MASS Sympathetic discharge causes what ?
↑ Arterial pressure
↑ in rate & strength = ↑ Cardiac Output
Muscle walls of veins are contracted = ↑ venous return / preload.
SVR formula ?
80 X (MAP-RAP)
Platelet aggregation and thrombus formation is secondary to what ?
Coronary vasospasm can lead to what ?
Rupture of plaque
What can cause a vasospasm ?
Area of the myocardium that is affected as a result of an MI?
The percentage of heart attacks that are fatal?
Neutorphils that cause tissue damage are activated by ?
Lack of O2
Damaged myocardial tissue is replaced by what ?
Often the origin of infarct moves from endocardium to epicardium. This is know as what?
Subendocardial myocardial infarction
Decreased cardiac output causes death because ?
- Systolic Stretch
- Cardiogenic Shock
Daming of venous blood causes death because?
- It increases capillary hydrostatic pressures
- Leads to Edema and Congestion
Fibrillation can cause death and is most often the result of what?
- Depletion of K+
- Injury Current
- Sympathetic reflexes
- Abnormal conduction pathways
Hemodynamic alterations can be a result of?
- anesthesia induced hypotension
Ischemic Heart Diseases that are Non-Atherosclerotic ?
- Traumatic injury
- Kawasaki Disease
- Cocaine-Induced Vasospasm
Treatments of CAD
- Clot dissolving drugs
- Shock for fibrillation
- Angioplasty / Stents
- Coronary Bypass on CPB or Op-CAB
- Heart Transplant
CAD patients tend to be
Hypovolemic with increased SVR
CPB Considerations: Hypovolemia
When anesthesia removes vosoconstriction during induction, what is needed?
Keep track of how much crystalloid is given before bypass; check HCT just before going on CPB if concerned.
- Volume Expansion
The lower the EF (<40%), the greater the likelihood of the patient to be in CHF, therefore the patient may be ?
- Normal or hypervolemic
CPB Considerations: ECG
Be alert for any ectopic or Eschemic changes. When going on CPB, be especially observant for
- ST Elevations
- Bradycardia (no vent yet)
- PA Pressures
The change from pusitile pressure to non - pulsitile pressure decreases the following:
- Surgical manipulation
Increase flow and pressure to optimize flow to coronaries.
With myocardial protection in mind what should be considered with a patient that has AI?
Should retrograde carioplegia be considered ?
- Suction with LV Vent
- Depends on the extent and location of legions.
Why is the time during cross-clamp removal so critical ?
- We want to prevent distention of the heart
Mortality risk of a redo CABG?
Risk of entering a patant IMA graft during sternotomy approaches what percentile?
Blood flow in muscles during strenuous exercise can increase by how much ?
Rate of blood flow through the muscles is ?
Intermittent during contraction due to mechanical compression of the vessels.
Capillaries open (vasodilate) during exercise do to ?
Decreased O2 in the tissues.
Drop in Oxygen content in muscle tissues causes what ?
Local arteriolar dilation
Sympathetic vasoconstrictor nerves secrete
Adrenal glands secrete
norepi (a) and Epi (B)
Vasodilation is due to:
- ↓ O2 in the tissues
- Lactic Acid
Sympathetic vasoconstrictor nerves secrete the following?
Norepinephrine at their nerve endings
When the Sympathetic vasoconstrictor nerves are maximally activated, they can secrete enough norepinephrine to cause what?
Decrease in blood flow through the resting muscles to as little as 1/2 to 1/3 of the normal flow.
Mass Sympathetic discharge causes what ?
- Increase in Arterial Pressure
- Increase in C.O.
Increase in Arterial Pressure causes what ?
- Vasoconstriction of arterioles
- Increased contractility of the heart
- Increased filling pressures
During Mass Sympathetic discharge, the heart is stimulated which causes what?
- Increased HR
- Increased in contractility
During Mass Sympathetic discharge, the arterioles of the PVS are strongly contracted which causes what ?
- Active muscles are strongly dilated
- No vasoconstriction in coronary & cerebral circulation
During Mass Sympathetic discharge, the muscle walls of the veins are contracted which causes what ?
- Increase in venous return / preload