Smith.Ch.30.DiseasesoftheCardiovascularSystem Flashcards
Cardiac output values in resting horse range from
32 to 40L/min
What are methods to determine cardiac output?
Fick method
Doppler echocardiography
dye dilution/ thermodilution/ litium dilution
Where is the most common location of ventricular septal defect in large animals?
perimembranous
VSDs are more common in which equine breeds?
Welsh mountain ponies
Arabian
Standardbred
Quarterhorse
Why do ventricular septal defects occur?
failure of fusion of part of the endocardial cushion and the muscular ventricular septum or failure of fusion of the truncal and conal septa
Describe Eisenmenger complex
defect in which right-sided heart resistance to blood flow causes the shunt associated with VSD to become right to left (rare)
**cyanosis is a distinguishing feature
What size is a VSD (VSD to aortic root ratio) that is unlike to be hemodynamically significant?
less than 0.3
With moderate to large VSDs, horses are at greater risk for developing congestive heart failure sooner. Why?
-simultaneous heart dz or Left sided heart failure d/t chronic volume overload can increase pulmonary vascular resistance
-right ventricle– chronic pressure overload
**comb of pressure and volume overload= greater risk for developing CHF
Which horses with VSDs are at risk for development of CHF early in life and have a shortened life expectancy?
Large defects: >3.5 cm or VSD/aortic ratio of 0.64
peak shunt velocities: <3.5m/s
define patent ductus arteriosus
persistent patency of the vessel that connects pulmonary arterial system to the aorta
(pulmonary artery to aorta)
Why does the ductus arteriosus close?
In response to:
-lowered pulmonary vascular resistance
-increased systemic vascular resistance
-increased blood volume
-increased left ventricular pressure when breathing begins
-placental circulation removed
Clinical signs of a PDA are dependent on:
-length and diameter of the ductus arteriosus
direction of the shunted blood
presence of other cardiac defects
Describe PDA murmur
continuous machinery murmurs
Direction of PDA shunt usually occurs?
left to right
–produces left ventricular volume overload
-pulmonary hypertension & congestion
+/- right sided ventricular hypertrophy
When does switch of PDA shunt occur, to right to left?
When pulmonary resistance equal or exceeds the systemic vascular resistance
When is PDA closure expected in foals?
by 96 hours of age
In a foal with PDA, what is risk for future riding?
b/c of marked dilation of the pulmonary artery– rupture of pulmonary artery is possible
Define tetrology of fallot vs pentalogy of fallot
- biventricular origin (overriding) of aorta)
- Ventricular septal defect
- obstruction of pulmonary arterial flow (pulmonary stenosis)
- secondary right ventricular hypertrophy (d/t obstruction of pulmonary arterial flow)
- atrial septal defect or persistent ductus arteriosus
Pathogenesis of tetralogy/pentology of fallot
abnormal development of the conal septum in the embryonic heart– leads to narrowing of the right ventricular infundibulum (pulmonic stenosis), an inability of the conal septum to participate in closure of the interventricular foramen (VSD) and overriding of the aorta
What is the more common congenital cardiac defects that cause cyanosis in large animals?
tetralogy of fallot
C/s of cyanosis is observed when unoxygenated hemoglobin is reduced to:
<5 g/dL (unoxygenated hemoglobin)
Cyanosis resulting from heart failure or respiratory disease improves with what treatment?
oxygen administration
What is the most common atrial septal defect?
ostium secundum defect– patent foramen ovale PFO) is most frequent
Pathogenesis of persistent foramen ovale
failure of septum primum (valve of foramen ovale)- to become adherent to the crista dividens after birth, when changes in left and right atrial pressures produce functional closure of the formen ovale
In calves, what is the most common defect associated with PDA?
persistent foramen ovale
atrial septal defect murmur
holosystolic crescendo-decrescendo murmur at the left heart base
triscupid valve atresia c/s
cyanosis
crescendo-decrescendo or bandshape holosystolic murmur or pansystolic murmur audible over the rigth and left heart base
tachycardia
tachypnea
weak peripheral pulses
polycythemia (common)
Define persistent truncus arteriosus
one arterial vessel leaves the heart above a VSD
**coronary and pulmonary arteries and aorta arise from this vessel
Pseudotruncus arteriosus definition
presence of a remnant of an atretic pulmonary trunk
**congenital cardiac disease
What are the most common aortic anomalies seen in foals and calves?
dextropositioning or transposition of the aorta
**other anomalies: persistence of the right aortic arch and double aortic arch (may cause esophageal compression)
What is Eisenmenger complex?
Switch in blood flow from right to left side of the heart, to the left to right (results in decreased oxygenation of blood)
Ectopia cordis cervicalis is a relatively common defect in which species?
cattle
What defects are associated with ectopia cordis cervicalis?
defects of the heart, great vessels, neck (torticollis), ribs and sternebrae
Chronic active infection such as what, can predispose animals to the development of bacterial endocarditis or nonvegetative valvulitis?
foot abscesses
rumenitis
reticular abscess
other septic process lead to sustained or recurrent bacteria
What are the most common bacterial isolates from equine and bovine endocarditis cases are:
streptococci
Pasturella or Acitnobacillus spp
Truepuerella pyogenes (formerly Arcabobacterium pyognes)
Lesions of aortic and pulmonic valves can produce what kind of murmurs?
systolic
diastolic (most common in lg animals)
or Both
Aortic regurgitation in horses is most commonly associated with
degenerative valve disease
pulmonary regurgitation in cattle is most commonly associated with
bacterial endocarditis
Describe aortic valve lesion murmurs
holodiastolic
descrescendo
musical murmurs
**can be descrescendo, soft & blowing
water hammer or bounding arterial pulse (assoc w/ sig L ventricular overload
Signs of congestive heart failure in cattle/horses
tachycardia
coughing
respiratory distress
jugular venous distention
subcutaneous edema
ascites
mammary vein distention (cattle)
describe murmur of ruptured chordae tendinae?
radiating musical murmur– distinctive honking quality
*may have band shaped pansystolic murmur
acute onset of respiratory distress with coughing and expectorating foamy pulmonary edema fluid is a relatively consistent feature of what cardiac abnormality?
ruptured chordae tendinae
Describe murmur of mitral valve prolapse
crescendo midsystolic to late systolic or holosystolic murmur with PMI over the mitral valve area
(similar with tricuspid valve prolapse)
Triscupid valve lesions in horses vs cattle are most commonly due to:
cattle: bacterial endocarditis, neoplasia of the right atrium
horse: bacterial endocarditis from septic jugular vein thrombosis
Echo evidence of mitral valve regurgitation
-INC left atrial and left ventircular dimensions
-rounding of left ventricular apex
- pattern of left sided volume overload
+/- INC fractional shortening
-bulging of interatrial septum toward the right
-larger than nomral pulmonary artery (>aortic root)– severe pulmonary hypertension
Tricuspid regurgitation echocardiac evidence
right atrial and right ventricular enlargement with paradoxical septal motion
–> visualizing lesions of endocarditis or neoplasia
aortic regurgitation echocardiographic evidence
left ventricular dilation
increased aortic root diameter
decreased aortic root diameter during diastole evidence of inc severity of aortic regurgitation
INC left ventricular fractional shortening
diastolic fluttering of the septal mitral valve leaflet
high frequency vibrations of the interventricular septum or aortic valve in diastole
–>visualization of valve prolapse, fenestration, healing endocarditis lesions or tears
Besides echocardiographic evidence of bacterial endocarditis, what are other C/s and diagnostics that indicate endocarditis
anemia
neutrophilia (a left shift may be present)
increases serum globulin concen
INC SAA
hyperfibrinogenemia
liver enzymes INC
urinalysis (+/- pyuria or hematuria)
positive blood culture w/ febrile episodes
other lab abnormalities of sepsis
Most horses with mitral valve regurgitation do not develop fulminant pulmonary edema, instead they develop
chronic pulmonary hypertension leading to subtle respiratory signs associated with interstitial pulmonary edema and subsequent development of right-sided CHF
In regards to valvular heart disease in horses, what is the most common valves involved?
Aortic is most commonly effected with degenerative valve changes
**followed by mitral valve, tricuspid valve and pulmonic valve
Jet lesions occur due to
asosciated with high -velocity turbulent regurgitant blood flow
**usually found in the receiving chamber
What lesions can cause moderate to severe valvular regurgitation and are more likely to progress rapidly and warrant a guarded to poor prognosis?
ruptured chordae tedinae
flail valve leaflets
marked valvular thickening
Treatment of endocarditis can ultimately result in?
scarring of the valve leaflet, that leads to progression fo regurgitation and death of animal
When treating cattle for bacterial endocarditis, the antibiotic of choise is?
antibiotic with gram positive coverage
Indication of clopidogrel in treatment of bacterial endocarditis? (in horses)
to prevent platelet adhesion and increased size of the valvular mass
Use of what medicatiosn can be used in cattle to prevent platelet adhesion and increased size of the valvular mass?
aspirin (100 mg/kg/day)
low-dose sodium heparin (subcu 30 to 40 units/kg twice daily)
Horses benefit (as do other spp) from the use of vasodilators in treatment of heart failure, what drug has been shown to be beneficial in horses with treatment of moderate MR or AR?
angiotensin converting enzyme (ACE inhibitors)
**benazepril: 0.5 mg/kg PO once daily
How do effective parasite control measures prevent predisposing causes of valvular heart disease?
trauma to heart valves
microembolism
infarction
**in horses
Define cor pulmonale
refer to the effect of the lung dysfunction on the heart and therefore a secondary form of heart idsease
Pathogenesis of cor pulmonale
pulmonary hypertension that leads to right ventricular hypertrophy–> dilation or failure
What is the primary cause of the cor pulmonale in cattle?
High mountain disease (brisket disease, high-altitude disease)
Pathogenesis of High mountain disease?
hypoxic vasoconstriction from high-altitude dwelling
What disease or factors contribute to the development of High Mountain disease?
pneumonia
lungworm
ingestion of locoweed (Oxytropis and Astragalus spp)
chronic pulmonary disease
What are the primary presenting clinical signs of brisket disease?
subcutaneous edema of the brisket, ventral thorax, submandibular area and occasionally limbs
lethargy
weakness
bulging eyes
diarrhea
collapse
death may occur
tachycardia (with a gallop rhythm, +/- splitting of S2 heart sound
Why would there be splitting of the S2 heart sound in brisket disease?
because pulmonary hypertension may accentuate the separation of the aortic and pulmonic valve closures, producing an audible splitting of the S2
**most notable on inspiration
Horses with clinical signs of cor pulmonale?
RAO–> leading to cor pulmonale
labored breathing
coughing
exercise intolerance
wheezes ausculted bilaterally
Differentials for clinical signs of right sided heart failure
bacterial endocarditis or TR
cardiomyopathy
cardiac lymphosarcoma/ other thoracic neoplasms
traumatic reticulopericarditis
left sided heart fialure
pleuritis or pleural effusion
congenital pulmonic valve stenosis (rare)
The response to hypoxia in brisket disease is dependent on:
amount of smooth mm in the pulmonary arteries
Brisket disease path:
Chronic pulmonary artery hypertension causes
pressure overload in the right ventricle
– responds with increased workload with hypertrophy, dilation or failure (dep on speed of which the condition develops)
Chronic right sided heart failure can lead to what?
diastolic dysfunction of the left ventricle
Why does ingestion of locoweed (oxytropis and Astragulus spp) predispose cattle to right sided heart failure?
Swainsonine
** causes toxic mycoardial damage
Brisket disease is common in cattle, kept over what altittude?
over 6000 feet
In what seasons is high mountain disease most commonly seen?
fall and winter
** due to cold weather exacerbating pulmonary hypertension
Is cor pulmonale reversible in HMD?
Yes–if animal is brought to lower altitudes
When do cattle not have reversible cor pulmonale?
-other lugn disease
- mean PAP of 50 to 55 mm HG
**rare
- once heart failure develops
Selection of breeding stock to prevent HMD?
low or normal PAPs at altitudes above 5000 feet
Define myocarditis
inflammation of the myocardium caused by bacterial, viral or parasitic organism or thromboembolic disease
What are common causes of bacterial myocarditis?
Stpahylococcus aureus
Streptococcus equi
Clostridium chauveoei
Mycobacterium spp
What are known viral causes of myocarditis?
foot and mouth disease
equine infectious anemia
equine viral arteritis
equine influenza
African horse sickness
What are known parasitic causes of myocarditis?
strongylosis
cysticercosis
sarcocystic infection in ruminentas
Define cardiomyopathy
subacute or chronic disease of the ventricular myocardium that occurs without anatomic valvular disease, congenital malformations of the heart or vessels or pulmonary disease
Hypertensive cardiomyopathy ahs been detected in horses associated with what diseases?
chronic renal disease
pain assoc with chronic laminitis
ponies with EMS
Dilated cardiomyopathy is associated with:
-ventricular dilation
increased ventricular mass
decreases systolic function
What known genetic predispositions exist for the development of inherited/genetic cardiomyopathy
- red holstein gene in Holstein Friesan cattle
- curly hair coat in polled herefords and in Japanese black calves
What toxic components can cause cardiomyopathy?
monensin
lasalocid
salinomycin
gossypol
Cassia occidentalis
phalris spp
vit E and selenium deficiency
copper deficiency
excessive molybdenum
high sulfatestes (secondary copper deficiency)
Acer family (plant tox)
rattle snake envenomation
It is difficult to distinguish C/s of myocarditis from what diseases?
colic
respiratory disease
lameness
septicemia
–C/s of myalgia, reluctance to move exercise intolerance
Differentials for causes of dilated cardiomyopathy
- nutritional (Vit E, selenium, copper deficiency)
- toxic: monensin, gossypol, salinomycin, lasalocid, hypoglycin A, Cassia spp., or Phalaris)
- Infectious (viral, bacterial, or parasitic)
- Drug induced
Differential diagnosis for dilated cardiomyopathy?
young– congenital heart defects, cor pulmonale, nutritional myodegeneration
Adults– bacterial endocarditis, cardiac neoplasia, thoracic abscess, pericarditis, pleuritis, diaphragmatic hernia
In an attempt to compensate for the reduced cardiac output, how is circulating fluid volume increased in cardiomyopathy
activation of renin-angiotensin aldosterone system & iNC arterial resistance
What leads to the development of pulmonary edea in heart failure?
reduced cardiac output–> stim renin-angiotensin-aldosterone system– INC arterial resistance
– INC ventricular preload (venous return)
– INC afterload (arterial resistance)
–> causes pulmonary edema & reduced cardiac contractility
Microscopic abnormalities associated with cardiomyopathy
- INC fibrous tissue in interstitium in absence of inflammation (or foci of inflammation
- variation in cross-section of cardiomyocytes
- degeneration of adjacent myocardial fibers
- myocardial vacuolation and degeneration with necrosis and fibrosis
Prompt administration of what drug can be beneficial to survivors of ionphore toxicosis?
administration of Vit E
Why are corticosteroids controversial in treatment of cardiomyopathy?
Possible viral recruidescence if the cause is viral
What are therapeutic strategies used for treatment of dilated cardiomyopathy?
- positive inotropic agents (digoxin)
- diuretics
- vasodilators
- rest
5 +/- removal of pleural or abdominal fluid
When is the use of digoxin contraindicated in the treatment of dilated cardiomyopathy?
monensin toxicosis
Ideally the peak and trough concentration of digoxin should be between:
1 to 2 ng/mL
Before treatment of digoxin therapy what should be addressed int eh patient?
dehydration
acid-base balance
electrolyte abnormalities
When should the dose of digoxin be reduced in patietns?
with elevated creatinine or blood ure anitrogen levels
What diuretic is most commonly used in large animals?
furosemide: 1 mg/kg
Which ACE inhibitor is most effective in horses?
benazepril
Other ace inhibitors: quinapril, ramipril, enalapril
Define pericarditis
inflammation of the pericardium that results in accumulation of fluid or exudate between the visceral and parietal pericardium
Causes of pericarditis in large animals
-penetration of ingested foreign objects or external wounds
-hematogenous spread (septicemia) of infection
-extension of infection from the lung or pleura
-viral infections (equine viral arteritis or equine influenza)
-neoplasia
-Mare reproductive loss syndrome (MRLS) (Actinobacillus spp)
What are the most consistent clinical signs on auscultation with pericarditis?
tachycardia
muffling of heart sounds
absence of lung sounds in ventral thorax
dorsally lung ounds are louder thn normal
Contrast auscultation of pericarditis vs pleuritis?
lung sounds are muffled ventrally (heart sounds are not0
radiation fo heart sounds over a wider aea than normal
Cattle: When auscultated with splashing sounds sometimes referred to as “washing machine murmur or rub”, what does this mean clinically?
- can be attributed to accumulation of gas and fluid in pericardium
**indicative of presence of gas forming (anaerobic organisms)
**grave prognosis
Electrocardiogram abnormalities that are can be seen with pericarditis?
- decreased amplitude of the QRS complexes (<1.5 mV in the base apex lead)
- electrical alternans (altered congifuration fo the P, WRS or T complexes on a regular basis)
- ST segment elevation or slurring
+/- right -axis deviation int eh stanard limb leads
What is the safest site to perofrm a pericardiocentesis?
left fifth (fourth in cattle) intercotal space 2.5 to 10 cm dorsal to teh olecranon, above the level of the lateral thoracic vein
What bacteria is commonly associated with pericarditis and mare reproductive loss syndrome?
Actinobacillus organisms
What are the consequences of pericardial effusion to the heart?
- decreased distensibility (increased ventricular end-diastolic pressure) of the heart
– impairs the hearts ability to fill in diastole
–INC atrial pressure - reduce venous flow or venous return to the heart and diastolic perfusion of the myocardium
–> decreased ventricular contractility, stroke volume and cardiac output
Difference between effusive and constrictive pericarditis
effusive: presence of pericardial fluid causes hemodynamic consequences
**removal of fluid beneficial
constrictive: reduction in ventricular compliance d/t fibrinous or fibrotic involvement of pericardium and epicardium
**removal of fluid not beneficial
Exposure to what was the greatest risk factor for the development of fibrinous pericarditis during the mare reproductive and loss syndrome epidemic?
Eastern tent caterpillars
Traumatic pericarditis is not uncommon in cattle, but occurs in less than what percentage of cattle with traumatic reticuloperitonitis?
less than10%
Treatment of pericarditis in horses
– placement of a large bore indwelling chest tube into the pericardial sac under echocardiographic guidance and drainage and lavage of the pericardial sac
–> with local infusion of antibiotics
Why can diuretics results in worsening heart failure with pericarditis?
Reduce venous return and preload in animals with pericarditis
= compromise to cardiac output & worsening heart failure
Removal of what trees can be beneficial in prevention of exposure to Eastern tent caterpillar?
black cherry trees
What is the most common cardiac tumor in large animls?
lymphosarcoma
Examples of neoplasias that may involve structures adjacent to the heart and may extend to the heart or heart base in horses,
mesotheliomas
melanomas
lipomas
fibrosarcoma
adenocarcinomas
other cacrinomas
squamous cell carcinomas
Lymphosarcoma is the most common cause of cardiac tumors in cattle, which has a predilection site for?
right atrial myocardium
**RV not uncommon, rare: LA or LV
Although more than 50% of cattle in some parts of the United State are infected with BLV, what percentage develop lymphosarcoma?
1 to 4 %
Thymic lympohosarcoma, which is not associated with BLV infections, also involving the heart can occur in what age of cattle?
cattle younger than 30 months of age
The prognosis for survival for cardiac neoplasia?
poor– death expected within 6 months
Control/prevention of cardiac tumors can only be performed for which tumors?
BLV
–> isolation of BLV pos and BLV neg animals
–> use of individual or serialized supplies
–>feeding colostrum from serologically negative cows only
–> frequent testing (at least every 6 months) & isolation of serologically positive animals over 6 months of age)
Define aneurysms
vascular dilations, develop from weakening of the medial elastic coat of blood vessels
Medial weakness of blood vessels seen in aneurysms can be caused by:
progression of intimal atherosclertoic lesions that has enlarged from hemorrhage
calcification
ulceration
thrombus formation
Causes of aneurysms in large animsl
**unknown
trauma (internal or external)
sepsis
parasite migration
degenerative vascular disease
atherosclerosis
aging changes (dilation, elongation and loss of elasticity of blood vessels)
Congenital aneurysms of what structure of the heart have been reported in horses?
sinus of Valsalva
Define thrombosis
formation of a clot that obstructs blood flow in the circulatory system
causes of thrombosis
trauma
venous stasis
catheterization for adminsiterin gmedication or fluids
needle penetration
indwelling acehters
thrombogenic solutions
bacterial contamination
Secondary thrombosis causes:
perivascular inflammation caused by cellulitis, lymphangitis or other source so fbacterial invasion round the blood vessel
Examples of a hypercoagulable states:
dehydration
endotxemia
anemia
hypotension
stress
stasis
Define mebolism
foreign material carried in the bloodstream
In large animals, embolis most commonly occur with:
bacterial endocarditis
thromboplhebitis
omphalophlebitis
parasitic arteritis
Calves with aorto or aortoiliac thrombosis clinical signs?
weakness
lameness
knuckling
paresis
paralysis of the hindlimbs
inability to rise
cold hindlimbs
lacking a femoral pulse
Aortopulmonary rupture and fistulization occur in what breed?
Fresians
What is the most common outcome of aneurysm of a major vessel?
thoughout to be rupture
Unruptured aneurysms may have other complications such as
thrombosis or emoblization o fthe thrombus
In Friesians, rupture of the aorta occurs into the pulmonary artery at what location?
at the level of th eligamentum arteriosum and into the surrounding perivascular stuctures
Spontaneous thromboembolism is commonly associated with?
parasitism in horses
**aorta and cranial mesenteric arteries are the most common sites frequently involved
What are risk factors for catehter associated thrombophlebitis
large intestinal disease
hypoproteinemia
endotoxemia
salmonellosis
fever
diarrhea
localled produced fluids
Arteriosclerosis recognized in cattle is most frequently caused by:
excessive vitamin D3 supplementation
ingestion of calcinogenic plans: Soamum malaxocylon, estrum dirunum or Trisetum flavescens
In horses arteriosclerotic lesions were caused by lesions induced by what organism?
Strongylus vulgarus
Ingestion of calcinogenic plants in horses, results in lesion in what locations?
aorta
Examples of anticoagulant therapy that may be effective in preventing the thrombus formation
clopidogrel: 2 mg/kg PO twice daily
aspirin; 100 mg/kg PO once daily ruminants
sodium heparin: 20 to 40 units/kg SC twice daily
Atrial fibrillation is characterized by
lack of coordinated atrial electrical activity
– caused by an abnormality of impulse conduction that results from multiple small rapid and random reentrant activation of the atria or by one or more discrete rotors
What shortens the action potential duration in atrial myocardial cells, making atrial fibrilation more likely to occur in horses?
high resting vagal tone
Causes of atrial fibrillation
atrial enlargement from atrial myocardial disease
atrioventricular valvular regurgitation
ventricular failure
myocarditis
endocarditis
autnomic nervous system imbalance
electrolyte or acid base distrubances
anesthetic drugs or tranquilzier adminitstration
Define “lone Afib”
no undelrying cardiac disease can befound
Cattle with atrial fibrillation usually have what undelrying disease?
gastrointesitnal disease
Define paroxysmal atrial fribillation
usually lasts no more than 24 to 48 hours abefore spontaneous conversion to sinus thythm occurs
What is a common cause of paroxysmal atrial fibrillation inhorses?
transient potassium depletion associated with administration of furosemide
What supplements are associated with atrial fibrillation in horses?
bicarbonate “milk shakes”- paroxysmal AF
-iatrogenic hyperthyroidism– admin of Thyro L
-supplements containing kelp or ground up shell fish
Describe atrial fibrillation arrhythmias
irregularly irregular
- absent 4th heart sound
Differentiate 2nd degree AV block from atrial fibrillation
Second degree AV block– regularly irregular rhythm, audible fourth heart sound
Atrial fibrillation– regularly irregular, absent 4th heart sound
Most cattle with atrial fibrillation of what underlying acid-base distrubance?
metabolic alkalosis
**experimentally metabolic alkalosis with hypokalemia have results in devleopmetn of Afib
When is cardiac troponin (cTnI) elevated in horses with afib?
acute AF: w/in 4 to 6 hours after onset of Afib
What if cTnI remains elevated in horses with afib?
Activ emyocardial disease shoul dbe suspected
electrocardiogram abnormalities in Afib
irregular R-R interval
QT interval and appaearnce of T wave may vary
pwaves absent (replaced by fibrillation waves)
Echocardiographic image that should be performed to indicate left atrial enlargement
2 chamber: measure in peak systole
**stbd, thgbd: 13.5cm or less
LA to AO ratio in 2D short axis view (provides mroe info on LA enlargement)
Which breeds have the highest incidence of AF?
standardbred
thoroughbred
draft horses
In horses with atrial fibrillation what is the most common valvular lesions?
mitral valve disease
Quinidine in the treatment of atrial fibrillation:
negative inotrope at high dosages
-causes systemic hypotension
-increases ventricular reponse rate
What are possible negative side effects of quinidine?
nasal edema
cutaneous reactions (urticaria or wheals)
laminitis
colic
marked diarrhea
ataxia
Max number of consecutive doses of quinidine to administer?
4 doses
When should therapy with quinidine be discontinued
QRS complex prolongation ( more than 25% of pretreatment value)
fast (>80 to 100 bpm) sustained supraventricular arrhythmia
ventricular rhythm
colic
marked diarrhea
ataxia
nasal edema
laminitis
How often administer a dose of quinidine?
1 dose every 2 hours
What medication can be administered in addition to quinidine to assist in cardioversion from afib to normal sinus rythm?
digoxin (11 microg/kgPO twice daily)
**can be helpful in cases, if conversion has not occurred in 24 to 48 hours
Caveat to combination therapy of digoxin and quinidine?
concurrent admin of digoxin and quinidine results in an increased plasma digoxin concentration
Digoxin can be indicated prior to pretreatment of atrial fibrillation in what circumstance?
When high heart hearts (want < 60 bpm in horses, <100 bpm in cattle before quinidine treatment)
very low FS (<24%) indicative of underlying myocardial disease
If furosemide cannot be removed from therapeutic tx regimen in a horse, what can be added to teh diet to prevent potassium depletion ?
KCL
At exercise, horses with atrial fibrillation heart rate should not exceed?
220 bpm
Define ventricular tachycardia
cardiac arrhythmia characterized by a rapid rhythm originating in teh ventricle
**originates below hte bundle of HIS in specilized conduction system surround the ventircular myocardium or both
Clinical signs associated with ventricular tahycardia
exerciseintolerance
syncope episodes
depression
weakness
colic
resp distress
coughing
ventral edema
pulmonary edema
In cattle ventricular tachycardia occurs most frequently secondary to
sepsis and toxemia
Large pulse waves seen in teh jugular vein are called cannon “a” waves that occur when?
atrium and ventricle contract simultaenously
When are signs of right sided CHF (ventral edema, venous distention) with ventricular tachycardia?
sustained uniform VT and increase in servity the longer duration and mroe rapid the rate of arrhthmias
When are signs of left sided CHF (coughing, expectoration of foamy fluid, respiratory distress) seen in ventricular tachycardia
multiform VT
What clinical signs help distinguish VT from sinus or supraventricular tachycardia?
presence of jugular pulses
bruit de cannon in an animal with rapid rhythm
Diagnosis of VT is made how?
ECG: series of 4 or mor ventricular premature complexes
**VPC may be widened and bizarre or WRS duration and apparent normal
Vtach: morphology of QRS complexes can be described as:
uniform (similar)
vary in morphology (multiform)
What is commonly seen with ventricular tachycardia in association with the atrium?
atrioventricular dissociation
– atrial rate slower than the ventricular rate
– may see fusion and/or capture beats
– VT can be sustained or paroxysmal
What should be considered in horses with acute onset of uniform VT and colic?
rupture of the aortic root at the right sinus of valsalva
What is a mechanism described in exercise induced VT in horses?
sympathetic stimulation (increasing the amplitude of early afterdepolarizations)
What is an important cause of sustained VT?
reetnry in the ventricle
What is though tot be one of the leading causes of sudden cardiac death in horses when other causes of death cannot be found on postmortem examination?
Ventricular tachycardia leading to ventricular fibrillation
Which gender is at increased risk for aortic root and sinus of Valsalva rupture?
males
– usu. middle-aged at time of rupture
VT is more likely seen in large animals of any age with what diseases?
GI disease
horses– following severe hemorrhage
Does slow, uniform VT require treatment?
often resolves or improves significantly with correction of underlying electrolyte or metabolic imbalances w/o requiring antiarrhythmic therapy
Horses with sustained heart rate >120 bpm, uniform VT treatment
antiarrythmic therapy
ECG findings associated with life threatening VT
multiform origin for the ventricula rpremature depolarizations
-torsades de pointes (wdie VT)
-presence of an R wave superimposedon preceding T wave (R on T)
large animal with following C/S treatment recommendation?
-C/S of CHF & hemodynamic collapse
-Heart rate <120 bpm
-Multiform VT (+/- R on T)
treat as cardiovascular emergecy– death from ventricular fibrillation is likely w/o antiarrythmic therapy
What drugs can be used to tx life-threatning VT:
lidocaine
quinidine gluconate
magnesium sulfate
IV procainamide, IV and oral propafenone (refractory VT), IV flecainide
sotalol
