Ischemic Heart Disease Flashcards
Three ways a heart might have inadequate O2 delivery (broad)
Decreased Perfusion
Other oxygenation causes
Inadequate O2 secondary to increased demand
Causes of decreased perfusion of the heart (5)
Progressive stenosis Thromboembolus Vasospasm Vasculitis Hypovolemia
Non-perfusion oxygenation issues (5)
Anemia CO Congenital Heart Disease Asphyxia Lung Disease
Once stenosis reaches _____%, there is a decreased ability to meet the demand
75%
severe/fatal usually requires a 70% reduction in diameter
Where is the most severe narrowing typically?
The proximal 2cm
Thrombus formation usually results from
rupture or fissure of plaque with platelet aggregation, release of thromboxane
Vasospasm is associated with…
Adrenergic stimulation, local factors (NO, endothelin, platelet factors), HTN/Platelet Activity
Two types of coronary vessels
Epicardial (Conductance Vessels – get athero)
Intramyocardial (Resistance Vessels - autoregulation and flow)
How does hypoxia kill muscle cells
Switch to anerobic glycolysis, lactate buildup, lowered pH, impaired membrane fxn lets K leak and Na in
Injury becomes permanent after…
20-40 minutes
Irreversible Injury to the heart…whats that like
Necrosis and permanent loss of functional myocardium
What is acute ischemic heart disease
blockage of flow in a coronary vessel leads an entire region of myocardium to become necrotic (MI)
What is chronic ischemic heart disease
Ischemia leading to loss f individual myocytes and diffuse fibrosis, resulting in myocarfial dysfunction and eventually heart failure
Morphology of reversible injury
Stunned Myocytes
Mitochondrial swelling, Relaxation of myofibrils, distortion of cristae
Morphology of irreversible injury (in chronic)
Chronic loss of myocytes, esp. in subendocardial
Coagulative necrosis + Apoptosis
Area becomes fibrotic
Subendocardial band of infarcted myo at watershed
Morphology of acute ischemia (MI) - Gross
Early – Pallor with hyperemic border
3-7 days: hyperemic border with central, yellow-brown softening. Possibly hemorrhage.
Eventual replacement w/ red-brown, depressed, scarred area.
Eventually gray and fiber like
Phases of color of a post-MI heart
White–> Yellow Brown –> Red-Brown –> Gray
Morphology of acute ischemia (MI) – Microscopic
Necrosis of Myocytes
Inflammation, Infiltration w/ Inflamm cells
Clean up of necrotic debris
Replacement of myocardium w/ scar tissue
Morphology of reperfusion injury?
Presence of contraction bands in damaged myocytes.
Two main symptoms of cardiac ischemia?
Chest Pain + Diaphoresis
Describe the chest pain of an MI
Crushing Pain over sternum
Radiates to left arm/back
NOT sharp or fluctuating
Describe MI diaphoresis
Shortness of Breath, Sweating, Nausea
Three serum enzymes associated with ischemic heart
Troponin I/T
Creatinine kinase (MB isoenzyme)
Lactic dehydrogenase
Whats the deal with troponin?
Cardio specific/Sensitive
Increase w/ CMB, elevated up to 7 days
Most sensitive/specific
Whats the deal w/ CK-MB
Highly specific and sensitive
Peaks at 12-24 hrs. Down quickly after.
Indicator of repeat infarct
Whats the deal with lactic dehydrogenase
Indicator of tissue damage that rises form 24h to 3-6 days. Stays up for weeks.
Nonspecific and basically useless.
Aside from symptoms and enzymes, how else might you diagnose an MI
EKG
Leukocytosis + Elevated ESR
The triad of symptoms associated with ischemic heart disease…
Systemic HTN
LVH
CAD
Most important clinical correlation with ischemic heart?
atherosclerosis
Difference between Stable, Unstable, and Prinzmetal’s angina
S – Relieves with rest+nitro
U – Not relieved with rest+mitro
P – Caused by vasospasm (ex. from cocaine)
How do chronic heart disease patients tend to present?>
History of angina/MI in last 5-10 years
Cardiac decompensation from slow myocardial atrophy
Pathophysiology of Chronic ischemic heart disease?
Progressive injury resulting in eventual CHF
Diffuse atherosclerosis w/ myocardial fibrosis + patchy scars
Most MIs are precipitated by…
Rupture of atherosclerotic plaque and thrombus formation
Sometimes from thromboemboli
Characteristic unique histological feature of MI
Inflammation delayed by 24-48 hours
MI sign at first few hours…
Acute Cell Injury –> Necrosis
First visual sign of inflammation?
Edema occurs at margin within first 24 hours
Hallmarks of coagulative necrosis
Loss of nuclei and hypereosinophilic fibers
In the 2-4 days following the day of MI….
Neutrophils migrate into necrotic area, cellular infiltrate becomes prominent
Afterwards macrophages get in
What’s going on with the heart 4-5 days following MI
Highest risk of rupture
Early complications of MI
Dysfunctional Heart Muscle
Arrythmia
Extensions of Infarct
Late complications of MI (5)
Aneurysm/Dilation Ventricular Rupture Mural Thrombus Pericardial effusion/Pericarditis Papillary Muscle Infarct with Mitral Insufficiency
How does ischemia show up on an EKG?
Inverted T Wave
Displacement of ST
Transient ST depression suggests…
subendocardial ischemia
Transient ST elevation suggests…
Transmural ischemia
Whats unique about an EKG after infarction?
Q waves/Loss of R waves
ST changes
Q wave, non-Q infarction
Angiography perfusion study indicated in…
Chronic Stable or Unstable Angina (symptoms despite therapy)
Patients w/ troublesome symptoms that occlude diagnosis
Patients with severe ischemia
Treatment of Angina
Lifestyle changes/Treat risk factors
Treat underlying conditions
Drugs – Nitrates, b-blockers, calcium channel blockers
Prevent thrombosis – aspirin, platelet adhesion blockers
Treatment of MI
Diagnose+Increase oxygenation
Aspirin
Anti-arrythmics
Reestablish bloodflow (Angiography, PCI, Fibrinolysis)
Fibrinolysis is most effective in…
the first 30 minutes
