Cardiology Flashcards
Cardiac myocytes lack
plasticity
(limited ability to respond to stress)
Mature cardiac muscle response to injury
- healing is by fibrosis
- Atrophy-reversible
- Hypertrophy-reversible
- Degeneration-sublethal
- Necrosis-lethal
Histopath of heart
unlikely to result in specific dx
Heart failure
- endpoint rather than specific disease
- dec myocardial contractility
- decreased compliance (fibrosis)
- dysrythmias/arrythmias
Endocardium
- Innermost layer of heart
- lines
- ventricles
- atria: thicker in atria than ventricles (can look white grossly)
- extends over chordae tendinae
Vascular supply of the heart
- left and right coronary artery arising from aorta
Epicardium
- outermost layer contiguous at cardiac base with pericardium
- entire inner surface of pericardial cavity lined by mesothelium
Systematic examination of the heart
Follow normal blood flow
RA - RV - MPA - LA - LV - aorta
Routine sections for histopath (2)
- papillary muscle
- mitral valve
Artifacts
- Post mortem clots: red ‘currant jelly’ clots not attached to endocardium
- Chicken fat clots in horses
- Red staining endocardium: RBC lysis (hemoglobin imbibition)
- Euthaniasia solution after a cardiac stick
SA node
AV node
R and L bundle branches
- junction of cranial vena cava and RA (free wall)
- bundle of HIs: beneal septal leaflet of right AV valve w/in interventricular septum
- ramify over ventricle as purkinje fiber: subendocardial
Cardiac compensation
- dilation
- hypertrophy
- inc heart rate
- inc in peripheral resistance
- inc in blood volume
- redistribution of blood flow
*failure of compensation: decompensation (heart failure)
DIlation
- structural compensation
- maintains connections and architecture
- stretching of myofibers
- often degenerative
- result of chronic overload
hypertrophy
- structural compensation
- inc in mass not cell number
- results from pressure overload
Mechanical compensation
- inc HR
- inc peripheral resistance
- inc in blood volume
- redistribution of blood flow
- baroreceptors: look for pressure drops and compensate with VOLUME
- not pumping well, poor pressures
- shunting
Cardiac hypertrophy
- compensatory mechanism that requires
- time
- healthy myocardium
- adequate myocardial nutrition/oxygenation
Causes of Right ventricular hypertrophy
- pulmonary hypertension
- congenital abnormalities
- tricuspid (Right AV) incompetence
- mechanical obstruction: dirofilarisis
Cor pulmonale
- right ventricular hypertrophy from long-term pulmonary hypertension
Causes of Left ventricular hypertrophy
- systemic hypertension
- renal dz
- congenital abnormalities
- aortic stenosis
- mitral incompetence
- Endocrine disease
- hyperthyroidism
- acromegaly
Clinical Syndromes of Cardiac Decompression
- Cardiac Syncope; acute cardiac failure
- Congestive Heart Failure; chronic loss of pumping ability
Cardiac Syncope; acute cardiac failure
- Arrythmias, massive necrosis, v-fib, heart block
- extreme changes in blood pressure and heart rate
- symptoms - collapse, loss of consciousness
Congestive Heart Failure; chronic loss of pumping ability
- Clinical sign and not a disease
- Forward failure: decrease flow to peripheral tissue
- Backward failure: Accumulation behind the failing chamber
Cycle of cardiac decompensation
- Cardiac Decompensation: Hypoxia
- renal: inc renin release (RAAS)
- renal: stimulates erythropoesis (EPO)
- polycythemia -> in blood viscosity
- Aldosterone release inc sodium and water retention
- Plasma volume inc Hypervolemia and edema
- Result: failing heart must pump more, thicker fluid
Aldosterone release increases….
- Sodium and water retention
Syndromes of cardiac decompensation
- Congestive heart failure
- Left Heart Failure
- Right Heart Failure
Right Heart Failure
Causes
- Valvular insufficiency
- Tricuspid (right AV) valve
- Pulmonary valve
- Pulmonary hypertension
- obstruction of forward flow
- Cardiomyopathy
Right Heart Failure
Sequelae
- Hepatic Congestion (nutmeg liver, hepatomegaly)
- splenomegaly
- Ascites (more common in dogs)
- Hydrothorax (more common in cats)
- Pleural and pericardial effusion
Left Heart Failure
Causes
- Myocardial loss of contractility
- myocarditis
- cardiomyopathy
- Valvular insufficiency
- mitral (Left AV) valve
- aortic valve
- Congenital defects
- PDA
Left Heart Failure
Sequelae
- Pulmonary congestion
- Pulmonary edema
- Pulmonary Fibrosis (will cause hypertension)
Top ddx for cardiac disease in dogs
- Endocardiosis
- Congenital disease
- DCM
- Hemopericardium
Top ddx for cardiac disease in cats
- HCM
- DCM
- Hyperthyroidism associated hypertrophy
- Congenital disease
Problem oriented approach
- D: Degenerative
- A: Anomaly (Congenital)
- M: Metabolic
- N: Neoplastic, Nutritional
- I: Inflammatory, Infectious, Immune-mediated
- T: Trauma, Toxicity
- V: Vascular
Patent Ductus Arteriosus
- RV and LV hypertrophy
- L -> shunt usually
- LA dilation
- R -> L shunt if severe -> cyanosis
- Dilation of PA and aorta, jet lesions in pulmonary artery
Aortic Stenosis
3 types
- Valvular
- Subvalvular
- Supravalvular
Subvalvular aortic stenosis
- concentric hypertrophy LV
- Fibrous endocardial thickening
- Post stenotic dilation aorta with jet lesions
- Myocardial necrosis
- subaortic stenotic ring
Pulmonic Stenosis
Sequelae
- Right ventricular hypertrophy
- Post stenotic dilation of pulmonary artery
- Muscular hypertrophy of RV outflow tract can complicate stenosis
Valvular dysplasia
- Malformation of valve leaflets
- leaflets may be attached to the septum
- common in cats and labrador retrievers
Septal Defects
- VSD most common
- Pulmonary hypertension from blood shunting from Left to Right
- right ventricular hypertrophy
- inc in pulmonary hypertension can lead to eventual compensatory right to left shunting
Ventricular septal defects
- Can be assoc with other cardiac defects
- Can occur either high or low (high more typical)
- Left to right shunt -> pulmonary hypertension
- Severe cases reverse shunting -> cyanosis
Tetrology of Fallot
- Pulmonary Stenosis
- Dextroaorta
- High Ventricular Septal Defect
- Right Ventricular Hypertrophy
Abnormalities of Aortic Arch
- Persistent right aortic arch
- Double aortic arch
- anomalous subclavian arteries
