L-48 Ischemic Heart Disease And Myocardial Infarction Flashcards
What is ischemic heart disease
Broad term encompassing several closely related syndromes caused by Myocardial ischemia
Most frequent cause of IHD
Obstruction in a main coronary artery
Atherosclerosis
Zone most vulnerable to ischemia
Subendocardium
Causes of ischemic heart disease
Impaired O2 supply due to: ▪️Coronary narrowing Atherosclerotic lesion Spasm ▪️impaired coronary filling(in diastole) affected by: Dec Diastolic time as in tachycardia Dec filling pressure as in hypotension ▪️impaired O2 carrying capacity(in anaemia)
Increased myocardial demand: inc pumping which inv cardiac work Cardiac work inc heart rate Work load Bp
What is angina pectoris
Chest pain due to ischemia of heart muscle caused by obstruction or spasm of coronary arteries
Character and site of angina pectoris
Character: constricting and tight oppressive crushing
Site:starts in center behind sternum or on left side on front chest and spread out to shoulder arm and left side of jaw
Describe stable angina
Develops on exertion Resolves at rest Lasts about 5 mins Insidious onset Stimulation of sympathetic and vagal afferent nerves
Describe unstable angina
Occurs at rest or during minimal exertion
Severe lasts longer than 10 mins
Either of:
New onset
Crescendo pattern
Thrombosis in a vulnerable plaque without complete obstruction
Describe spastic angina
Prinzmetal angina Occurs at rest Cyclic vasospasm due to contraction of vascular SM Symptoms are unrelated to exertion More in young women
What is MI
Follows complete interruption of blood flow to an area of myocardium
Causes of MI
▪️Rupture of an atherosclerotic plaque+ thrombosis and vasospam
▪️Completely occluding lumen of critical major epicardial blood vessel
▪️Infarction occurs downstream from occluded blood vessel
Outcome of complete coronary occulsion
Depends on the severity and duration of Flow deprivation
Within 60 seconds:
Severe ischemia leading to ATP depletion and loss of contractile function
Complete deprivation of blood flow for 20 to 30 minutes leading to irreversible myocardial injury
What does Distribution of necrosis depend on
Collateral perfusion
Location of occlusion within vessel
Vessel involved
Duration of ischemia
Pattern of infarct in LAD
50% of cases
Infarcts in anterior wall of left ventricle
ECG changes in anterior chest leads (V1-V3)
Occlusion of this artery may cause sudden death
Pattern of infarct: right coronary artery
30% of cases
In inferior wall and posterior septum
ECG changes in leads II, III and aVF
Pattern of infarcts:circumflex artery
20% of cases
In lateral wall
ECG changes in leads I, aVL and lateral chest leads (V4-V6)
What chamber do nearly all transmural MIs affect
Left ventricle
If in right ventricle then posterior inferior left ventricle is affected
Describe subendocardial MIs
Limited to inner 30% to 50% of ventrivle
Due to lysis of a thrombotic occlusion before full thickness infarction
Result in NSTEMI
Describe transmural MIs
Involves full thickness of ventricular wall
Due to atherosclerosis and acute plaque change with thrombosis
STEMI
Morphology of heart in less than 12 hours
Usually inapparent
Morphology in 12-24 hrs
Dead myocytes become hyperesinophyllic with loss of nuclei
(Coagulative necrosis)
Grossly:pale
Morphology in 24-72 hrs
Neutrophils infiltrate necrotic tissue
Grossly: lesions become more defined,yellow and softened
Morphology in 3 to 7 days
Dead myocytes are digested by macrophages
7-10 days morphology
Granulation tissue replaced necrotic tissue
