2019.Iss1.clinical cardiology Flashcards
equine acquired valvular disease
degenerative valve disease is common on which valves in horses?
aortic
mitral valves
equine acquired valvular disease
what are recognized risk factors for equine aortic regurgitation?
male sex
increasing age
equine acquired valvular disease
describe aortic valve regurgitation murmur
-descrescendo holodiastolic murmur
-can be musical in character
-loudest over the aortic valve, on left, right or both sides of thorax
equine acquired valvular disease
What factors are associated with eexrcise intolerance or death within 2 years of identifying aortic regurge?
-abnormal pulse quality
-pulse pressure >60 mmHg measured at coccygeal artery
-supraventricular premature depolarizations occurring at a rate of greater than 1 per hour
equine acquired valvular disease
Using pulse pressure to assess aortic regurge severity, what differentiated mild-moderate from severe?
severe >67 mmgHg
equine acquired valvular disease
using echocardiography to assess aortic regurgitation is based on what parameters?
- regurgitant jet size
- subjective assessment of left ventricular size & shape
- M-mode measurement of internal diameter of left ventricle in diastole
Others: high-frequency vibrations on mitral valve, aortic vale or septum; early closure of the mitral valve; dilation of the aortic root; and increased fractional shortening
equine acquired valvular disease
describe mitral valve regurgitation murmur
-systolic murmur
-loudest over mitral valve on the left (radiates in caudodorsal direction)
equine acquired valvular disease
mitral valve regurgitation is classified as mild with what characteristics:
-no left atrial enlargement
-color flow doppler echo demonstrates 1 or 2 thin regurgitant jets (whose height is subjectively no more than 1/3 of the height of the left atrium
equine acquired valvular disease
what are characteristics of severe mitral valve regurgitation?
-left atrial, left ventricular & pulmonary artery dilation
–> lead to pulmonary a rupture, affected horses will show signs of CHF at rest
equine acquired valvular disease
infective endocarditis, what is the most common site of infection?
mitral valve
equine acquired valvular disease
which bacteria have been reported in cases of infectious endocarditis in horses?
Pasteurella/Actinbobacillus sp.
Pseudomonas spp
Rhodococcus spp
equine acquired valvular disease
prior to treating infectious endocarditis, what is recommended?
3 serial blood cultures at 1 hour intervals
equine acquired valvular disease
what is the most common site of ruptured chordae tendineae?
mitral valve
equine acquired valvular disease
horses with ruptured chordeae tendinae will develop signs of acute left-sided heart failure, such as:
coughing
foamy nasal discharge
moist crackles on auscultation of the lung
sudden death
equine acquired valvular disease
describe the murmur associated with a ruptured chordeae tendinae
honking or musical murmur
flail of affected valve visualized on echo
Cardiovascular Response to Exercise and Training, Exercise Testing in Horses
when assessing poor performance, what are some parameters that are recommended
-historical questionnaires
-lameness examinations
-exercise electrocardiograms (ECG)
-echocardiograms
-respiratory sampling
-dynamic upper airway endoscopy
-measurement of laboratory values (lactate, SAA CK, electrolytes, cardiac troponins [cTn]
Cardiovascular Response to Exercise and Training, Exercise Testing in Horses
what are common diseases detected during exercise tests?
-lameness
-IAD/equine asthma
-upper airway obstruction
-myopathies
-exercising arrythmias
**less commonly detected: myocardial dysfunction, electrolyte abnormalities, neurologic disease
Cardiovascular causes of poor performance & exercise intolerance & assessment of safety in the equine athlete
List bradyarrhythmias that are a normal finding, as long as a sympathetic stimulation restores sinus rhythm at an appropriate heart rate
sinus bradycardia
sinus block
second-degree atrioventricular block
Cardiac therapeutics in horses
What is the drug of choice for pharmacologic cardioversion of atrial fibrillation?
quinidine
Cardiac therapeutics in horses
what is the MOA of class 1 antiarrhythmic agents?
block voltage-gated sodium channels
**slow the propagation of action potentials
Cardiac therapeutics in horses
Class 1a antiarrhythmic agents are recommended for use against which arrythmias?
supraventricular & ventricular tachyarrhythmias
Cardiac therapeutics in horses
which drugs belong to class 1a antiarrythmics
quinidine
procainamide
Cardiac therapeutics in horses
Which medications belong to the class 1b anti-arrythmics?
lidocaine
phenytoin
tocainide
mexilitine
what is the MOA of class 1 c antiarrythmics?
inhibitors of fast sodium channels
Cardiac therapeutics in horses
which drugs belong to the class 1c antiarrythmics?
flecainide
propafenone
Cardiac therapeutics in horses
What is the MOA of class 2 anti-arrythmics?
beta-adrenocreceptor antagonists (beta blockers)
** prolong phase 4 of the cardiac action potential, suppress SA pacemaker activity & AV nodal conduction
**SLOW HEART RATE
Cardiac therapeutics in horses
which medications belong to class II anti-arrythmics?
propranolol
sotalol
atenolol
esmolol
Cardiac therapeutics in horses
What is the MOA of class III anti-arrythmics?
suppress inward potassium current
**prolonging phase 3 of the action potential & refractory period
Cardiac therapeutics in horses
Which drugs belong to the class III anti-arrythmics?
amiodarone
Cardiac therapeutics in horses
What is the MOA of class IV antiarrhythmic agnts?
ca channel blockers
**act on phase 2 of the cardiac action potential
Cardiac therapeutics in horses
Magnesium sulfate can be effective in terminating what arrhythmia?
refractory ventricular arrhythmias
*reduces the occurrence of ventricular ectopy & VT in humans
Cardiac therapeutics in horses
What is the indication for anticholinergic drugs (atropine, glycopyrrolate)?
controlling vagal-mediate bradyarrhythmias
Cardiac therapeutics in horses
Which drugs are anti-cholinergics?
atropine
glycopyrrolate
butylscopolamine
What makes up stroke volume?
-amount of blood ejected from the left ventricle in early cardiac cycle
-cardiac contractility
-preload (end-diastolic LV volume)
-afterload (ventricular wall tension, largely influenced by systemic blood pressure)
Cardiac therapeutics in horses
Which drugs reduce preload in the treatment of CHF?
diuretics
Cardiac therapeutics in horses
What is the MOA of furosemide?
loop diuretic that inhibits the reabsorption of electrolytes in the thick ascending loop of Hnelse
**results in increased excretion of Na, Cl, K and water
Cardiac therapeutics in horses
Potassium-sparing diuretics can be dividing into what 2 categories?
- amioloride– inhibit sodium-selective channels in the late distal convoluted tubules & cortical collecting duct
- potassium sparing diuretics: inhibitors of type 1 mineralocorticoid receptors & act as aldosterone antagonists (spironolactone)
Cardiac therapeutics in horses
What is the MOA of thiazide diuretics?
inhibit sodium/chloride symporter in the renal epithelial cell of the distal convoluted tubule
**increases loss of sodium, chloride & water
**excessive sodium & fluid in the distal nephron enhances the secretion of potassium & hydrogen ions
Cardiac therapeutics in horses
what are drugs that reduce afterload in the the treatment of CHF?
-renin-angiotensin-aldosterone system inhibitors (ACE inhibitors)– spironolactone
Cardiac therapeutics in horses
Describe positive ionotropes
increase the force of myocardial contraction by increasing intracellular calcium concentrations or by sensitizing the myocardium to the effects of calcium
Cardiac therapeutics in horses
What is the MOA of cardiac glycosides (Digoxin) as a cardiac therapeutic?
inhibition of Na/K ATPase –> positive ionotropic effect
Cardiac therapeutics in horses
Tacchyarrhythmias occur in hypokalemia for what reason?
inhibition of Na/K atpase exacerbates the hypopolarization of the mycoardium
Cardiac therapeutics in horses
What positive ionotrope can be used in horses with pathologic bradyarrythmias?
dobutamine
** INC HR, Beta1-adrenergic effects
Cardiac therapeutics in horses
What is the MOA of phenylephrine?
vasopressor
**increasing peripheral blood pressure w/o increasing cardiac output
**alpha-1 receptor agonist
**does not work on the heart
Cardiac monitoring in horses
what is a major determinant of afterload?
blood pressure
Cardiac monitoring in horses
what is blood pressure the product of?
CO (cardiac output) and SVR (stroke volume)
Cardiac monitoring in horses
What does a central venous pressure >15 mmHg indicate?
patient is fluid overloaded or in a cardiogenic shock
Cardiac monitoring in horses
List methods used to measure cardiac output:
pulmonary thermodilution
transpulmonary thermodilution
lithium dilution
U/S velocity dilution
Ficks principle
Rebreathing CO2
Pulse contour analysis
echocardiogram
Cardiac arrhythmias in horses
atrial premature depolarizations often have no negative impact on performance, but especially in large horses, may predispose to…
atrial fibrillation
Cardiac arrhythmias in horses
For pathologic arrhythmias, one should investigate what sources?
- cardiac: acquired valvular disease, congenital deformations, myocardial damage, pericarditis & endocarditis
- noncardiac dz: electrolyte & acid-base disturbances, hypoxemia, endotxemia, toxic causes
Cardiac arrhythmias in horses
define atrial tachycardia
more than 3 atrial premature depolarizations
Cardiac arrhythmias in horses
What is the recommendation for treatment for APDs
**thought that the apds originate from dzed or inflammatory myocardium
–resting period or low-level exercise period
– steroid treatment
Cardiac arrhythmias in horses
Describe atrial fibrillation characteristics on ecg
-replacement of p waves by fibrillation waves
-irregular RR intervals w/ normal QRS morphology
Cardiac arrhythmias in horses
What are indicators that increase the risk for collapse or even fatal ventricular arrhythmia during exercise, in a horse with atrial fibrillation?
-abnormal QRS morphology
-R on T phenomenon
-high maximal heart rates (>220 bpm) during regular exercise
Cardiac arrhythmias in horses
List non-cardiac and cardiac adverse effects of quinidine administration in horses:
Noncardiac: nasal edema, depression, colic, diarrhea & laminitis
Cardiac: hypotension, QRS & QT prolongation, supraventricular & ventricular tachycardia (VT), Torsade de pointes, collapse & death
Cardiac arrhythmias in horses
IN case of quinidine toxicity, what can be administered?
IV sodium bicarbonate administration (1 mEq/kg) lower the free QS plasma ocncentrations
Cardiac arrhythmias in horses
What medication is recommended for digoxin toxicity?
phenytoin
Cardiac arrhythmias in horses
what are clinical signs associated with third degree AV block?
stress or exercise does not affect ventricular rate
-exercise intolerant
-numerous episodes of collapse
Cardiac arrhythmias in horses
What is this arrhythmia?
third-degree AV block resulted in atrioventricular dissociation and a slow & junctional) escape rhythm at rate of 25 bpm
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
What are the consequences of pericarditis leading to pericardial effusion?
-reduced ventricular filling
-diastolic dysfunction
= impaired venous return to the right heart
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
Describe the 3 different types of pericarditis.
- Effusive: pericardial inflammation resulting in fluid accumulation w/in pericardial sac
- fibrinous: accumulation of fibrin in the pericardium, with or w/o free fluid
- Constrictive: fibrotic & thickened, resulting in cardiac compression
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
As part of mare reproductive loss syndrome, what is the the most commonly identified bacterial isolate?
Actinobacillus spp.
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
what are neoplastic causes of pericarditis in horses?
lymphoma (most common)
mesothelioma, hemangiosarcoma
intra- or extrapericarial mass compressing the heart
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
Why are diuretics contraindicated in pericarditis?
b/c ventricular filling is impaired & cardiac function highly dependent on increased filling pressures
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
what is the prognosis for pericarditis?
idiopathic= good
bacterial/neoplasia= guarded to poor
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
List parasitic causes of myocardial diseases:
strongylus vulgaris– statistically assoc with focal ischaemic lesions in myocardium
onchocerca
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
List nutritional causes of myocardial disease in horses
-Vit E & selenium def: whit emm disease (predom in foals in selenium def areas
-copper def/molybdenum tox
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
List toxins & drugs as a cause of myocardial disease in horses.
-snake venom: rattlesnake, viper
-ionophores: monensin, lasalocid, salinomycin
-Plants containing cardiac glycosides: digitalis spp (foxglov), taxus pp (yew), Nerium oleander), Adonis aestivalis (summer pheasant’s eye), Lilly of the vallley, Rhododendron
-other plants: malva parviflora (marshmallow), atypical myopathy/seasonal pasture myopathy caused by ingestion of hypoglycin-A from seeds of maple trees (Acer spp)
-Cantharidin (blister beetle)
-sodium flouroacetetate rodenticides
-heavy metals
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
which breed is predisposed to aortic rupture? (with or w/o formation fo a pseudoaneurysm and/or aortopulmonary fistula)
fresians
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
If horses survive the acute phase of aortopulmonary fistulas assoc with aortic rupture proximal to the ligamentum arteriosum, what C/s can be seen:
-recurrent colic
-increased rectal tempreature
-tachycardia
-respiratory signs
–> right-sided congestive heart failure develops
Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses
What are predisposing factor to pulmonary artery rupture?
-long standing pulmonary hypertension
–> caused by LCHF, left to right shunting with pulmonary artery dilation
Equine Congenital Heart Disease
List diagnostic findings in horses with ventricular septal defects that suggest an unfavorable prognosis.
Equine Congenital Heart Disease
In foals with large ventricular septal defects, what are potential clinical findings
-C/S of heart failure or pulmonary overicrculation
-Thoracic radiographs: congestion
Equine Congenital Heart Disease
The arterial duct is a normal structure in the fetus that allow the diversion of blood away from the lung, by what time period is it closed in the horse postpartum?
3 days post partum
d/t increased O2 tension
Equine Congenital Heart Disease
Describe the murmur of a persistent ductus arteriosus.
continuous, machinery-type murmur at the left heart base
Equine Congenital Heart Disease
What are the 4 components of the tetralogy of fallot?
- right ventricular outflow tract obstruction
- right ventricular hypertrophy
- ventricular septal defect
- overriding aorta
Equine Congenital Heart Disease
Describe what a double outlet right ventricle malformation is.
-both great vessels arise entirely or predominantly from the right ventricle
**cyanosis related to insufficient pulmonary flow and heart failure assoc with left-to-right shunting
Equine Congenital Heart Disease
How do vascular ring anomalies present?
pediatric animals with dysphagia or stridor
**rare reports in horses
Equine Electrocardiography
Describe the phases of the cardiac action potential.
Equine Electrocardiography
Describe how the ECG electrodes are placed.
