CVT Cardiology Flashcards
Which deficiency can be seen in cats with DCM?
Taurine deficiency (not as common now)
Which breeds in dogs have been noted to have taurine deficiency related DCM?
American cocker spaniel, Newfoundland, Goldens
Which supplement showed an increased survival in humans with DCM?
L-carnitine (role in long chain FA metabolism and energy production - Lots in heart)
No controlled studies in dogs
What supplement should be offered to all dogs with DCM (esp Boxers)?
L-carnitine (role in long chain FA metabolism and energy production - Lots in heart)
No controlled studies in dogs
Has an imbalance btwn oxidant and antioxidants been noted in dogs with DCM and CVD?
Yes! JVIM 2005
What is an antioxidant and has a role in energy production that could be consider for supplementation in dogs with cardiac disease?
Coenzyme Q10
What is an important component of diet in animals with cardiac disease?
Na restriction (based on level of their disease) - Should be <50 mg/100kcal
What is neurocardiogenic (Vasodepressor) Syncope?
“reflex-mediated syncope o Incompletely understood adrenergic-stimulated baroreceptor reflex mechanism = inappropriate stimulation of baroreceptor reflex
o Sympathetic surge = “empty ventricle syndrome” = vagal stimulation to brainstem from ventricular mechanoreceptors = sympathetic withdrawal = vasodilation and bradycardia
o Usually follows fight, flight, fright, startle
What is considered the #1 cause of syncope across all ages and breeds?
AV Block
What is considered the #1 cause of syncope in older Schnauzers, WHWT, Cockers?
SSS
What is considered a common cause of syncope in MR dogs?
Neurocardiogenic (Warning sign of high preload, rarely fatal)
What are the 2 main diseases that can predispose to situational relfex-mediated syncope?
Advanced MVDD and pulmonary hypertension
What is the #1 cause of syncope in cats?
AV block (neurocardiogenic and SSS rare)
What is essential in the diagnosis of syncope?
Documenting the heart rate with Holter during event
Name 4 metabolic causes of syncope.
- Hypoglycemia
- Endocrine (Addison’s)
- Hypoxia
- Anemia
What is the definition of systemic hypertension?
Systolic BP > 160 mmHg
What is the sensitivity and specificity of blood pressure readings when BP > 160 mmHg?
o Oscillometric and Doppler methods have only 53-71% sensitivity and 85-88% sensitivity in detecting BP > 160mmHg
Name the top 3 diseases in cats that result in hypertension.
§ #1 CKD: 20-65% (probably more like 20-30%)
§ Hyperthyroid: 10-86% (probably more like 10-30%)
§ Diabetes: prevalence of SHT poorly documented
What is important to remember about Sight hounds and blood pressure?
Sighthounds have BP 15 mmHg higher than other dogs
Name the target organs that are damaged with hypertension.
- Kidneys: Esp > 160 mmHg risk of glomerular and tubulointerstitial changes
- Ocular: Esp > 180 mmHg retinal/intraocular hemorrhage, vascular toruosity, retinal detachement
- Brain: Esp > 180 mmHg seizures, mentation change, vestibular dz
How long did it take for systemic hypertension to result in cardaic hypertrophy in dogs?
About 12 wks
What happens with the blood pressure cuff is too small?
cannot occlude artery so measured pressure HIGHER than actual pressure
What happens with the blood pressure cuff is too large?
occludes artery too soon so measured pressure LOWER than actual pressure
What is the ideal cuff size?
40% circumference of limb
Why do most animals (and humans) need multiple medications to control BP?
o May occur b/c need to directly vasodilate (amlodipine) AND limit ability of compensatory mechanisms to adjust to medication-induced changes (ACE-I)
What is the major concern of using Ca2+ channel blockers alone?
preferential dilation of renal afferent arterioles = increased intraglomerular pressure and can cause glomerular damage; ACE-I can protect glomerulus
What is the step wise apporach for chosing hypertension control in dogs?
□ ACE-I: decrease in BP 10%, limit proteinuria; can start SID and go up to BID if needed
□ Amlodipine: start SID, go to BID if needed; long half-life in dogs = evaluate after 1 week
□ Refractory HT: search again for underlying causes; consider hydralazine, prazosin, spironolactone, diuretics (proceed carefully and add each one step-wise with close BP monitoring; no good data on multi-drug plans in animals
Name 3 indications for pacing in dogs.
SSS, AB block, atrial standstill
What are the most common type of pacing?
transvenous, single-lead, single-chamber ventricular pacing (VVI)
What does VVI stand for in pacing?
ventricle is paced, ventricle is sensed, and the pacemaker inhibits itself in response to detection of native electrical activity
What are 4 parameters that can be adjusted in a pacemarker?
o Pulse Width: Duration of the pacemaker discharge in miliseconds
o Amplitude: Intensity of the pacemaker discharge in volts
o Sensitivity: Ability of the system to detect native electrical activity in the atria or ventricle
Refractory Period: Duration of time following a sensed or paced event that all activity is ignored by the pacemaker
What is a potential risk if your sensing and timing of discharge are off?
Ventricular fibrillation
What percentage of dogs had complications during pacemarker implanation?
About 55%
What is the most common complication with pacemarker implantation?
10% Overall dislodgement rate = Loss of sensing or pacing
What percentage of dogs got an infection of their pacemarker?
About 5 %
What percetnage of dogs are still alive at 3 years after placement of a pacemarker?
About 50%
What is rate responsive ventricular pacing?
§ Uses an activity sensor that attempts to match the paced heart rate with the patient’s activity (accelerometer, minute-ventilation sensor, thermometer, gravitation sensor or QT-interval sensor)
What is dual lead, dual chamber pacing?
(most commonly used in people) § Uses a second pacing lead within the right auricular appendage. This senses and paces the atrium, then stimulating a timed ventricular depolarization afterward via the right ventricle.
§ Retains AV synchrony.
What is pacemarker syndrome?
When atrial contribution to cardiac output and contraction of atria against closed AV valve - Leading to weakness, dyspnea, heart failure
What type of pacing is more physiologic and why?
Dual chamber pacing - It preserves syncrhony btwn atria and ventricles
What is SVT?
Rapid rhythms originating in the atria or using the atria or AV junction above the bundle of His as a component of the tachycardia circuit.
What is the purpose of a vagal maneuvers?
increase vagal toneàslowed sinus node discharge, prolonged AV conduction and refractoriness.
§ If an SVT abruptly terminates in response, possibilities are AV nodal re-entrant tachycardia, orthodromic AV reciprocating tachycardia, or sinus nodal re-entrant tachycardia. Lack of response doesn’t rule these out.
If blood pressure is compromised by SVT and patient does not repond to vagal maneuver, what can be tried?
Diltiazem (Slows AV node conduction and prolongs AV refractory period)
Esmolol (Short acting selective B1 blocker)
Procainamide (prolonges refractory period of ventricules)
Name 4 drugs that can work on the SA node.
- Beta Blockers
- Calcium channel blockers
- Digitalis
- Class III (K+ channel blocker)
Name6 drugs that can work on the AV node.
- Digoxin
- Beta Blockers
- Calcium Channel Blocker
- Class III (K+ channel blocker)
- Class IC (Na+ channel blocker)
- Adenosine
What can occur with persistent tachyarrhythmia?
Structural and electrical remodeling
What are 3 indications that you should treat ventricle arrhythmias?
- Clinical signs (hypotension = weakness, lethargy, exercise intolerance, syncope)
- tachycardiomyopathy
- Harbor the risk of death
In general which is worse, polymorphic VPCs or monmorphic?
Polymorphoric (except in Boxer with ARVC)
What is the frequency that R on T can result in V fib/sudden death in dogs?
Unknown!
What if German Shepherd VT?
young dogs (death 15-52 weeks); sudden death in 15% of affected dogs; rapid polymorphic VT; usually survive if make it to 2 years; mechanism thought to be triggered activity from early and delayed after depolarizations (don’t know how sustained VT or Vfib occur); death associated with changes in autonomic tone (sleep, early morning excitement)
What are 2 electrolyte abnormalities that should be considered if Vt not responding to lidocaine?
Hypokalemia and hypomagnesemia
If lidocaine fails for Vtach what other options are there?
Procainamide
Amiodaraone
PO sotalol, meiletine
What is the most common cause of arrhythmia in cats?
Associated with primary cardiac disease (generally do NOT present for CS related to arrhythmia (incidental)
What are the most common arrhythmias in cats?
BBB or LAFB (48.2%)
VPC (34%)
SVT (24%)
Av Block (12%)
What are the most common causes of 1st degree AV block in cats?
Digoxin toxicity, high vagal tone, structural heart diseases, no clinical significance
What are the most common causes of 2nd degree AV block in cats?
Cardiomyopathy, conduction, or alpha 2 agonists
Need pacemarked it clinical
What are the most common causes of 3rd degree AV block in cats?
Older cat (> 11 yrs) 0 Cardiomyopathy, infiltraive dz, other structural heart dz, hyper T4, idiopathic (conduction system degeneration) Need to treat with pacemaker if escape rate
What should you try first for VT in cats?
Beta blocker (IV - Propranolon or esmolol; PO - atenolol)
What does ST segment elevation suggest?
Myocardial hypoxia
What is cardioversion?
external transthoracic delivery of a DC current shock for restoration of sinus rhythm in patients with ventricular or SV tachyarrhythmias
When is a shock delivered to avoid inducing V fib?
Shock synchronized to R wave of QRS complex
What is cardioversion the most effective at treating?
Impulse re-entry (Afib, Aflutter, AV node re-entry, AV reciprocating tachycardias w/ accessory conduction, and Vtach)
How does cardioversion work?
shock simultaneously depolarizes all excitable myocardium and prolongs refractoriness = interrupts re-entrant circuits and establishes electrical homogeneity, terminating re-entry
When should cardioversion be considered?
Any tachycardia producing hypotension or CHF which does not respond to medical management
What is PDA and what does it stand for?
Patent ductus arteriosus
persistence of fetal ductus arteriosis = communication between descending aorta and MPA
What is the most common signalment of PDA?
Female (3:1) - Not in all breeds
What is the most common arrhythmia associated with PDA?
A-fib
What is the treatment for PDA?
Ductus closure ASAP! Surgical ligation or vascular occulsion
What is the standard vascular occluder for PDAs?
Amplatz canine ductal occluder
Which is better for PDA treatment, sx or catheter-based occlusion?
No difference in mortality
More major complicatons with sx and more minor complications with catheter based
What is a ventricular septal defect?
Hole in IVS allowing communication btwn RV/LV (present at birth)
Which spp are VSD more common in?
Cats
Which breeds get VSD?
WHWT, Lakeland terriers, English bulldogs, English springer spaniels (inherited)
What does a VSD result in?
Left to right shunt = Left sided volume overload
If a VSD results in excessive pulmonary overcirculation what can occur?
Development of pulmonary hypertension = Eisenmenger’s physiology
RV pressure overload = Promotes bidirectional or Right to left shunting (opposite from original direction)
Name 4 conditions that can results in right to left shunting.
§ Eisenmenger’s physiology (pulmonary hypertension reversing a left to right shunt)
§ Tetralogy of Fallot: VSD complicated by RVOTO and RV hypetrophy; right-to-left shunting predominates = hypoexemia, polycythemia
§ Double-chamber right ventricle: fibromuscular reaction and proliferation in RV = midventricular obstruction just distal to VSD (may close the VSD) = high pressures in proximal chamber = concentric hypertrophy of proximal chamber
§ Concurrent VSD and severe PS
How would Eisenmenger’s physiology appear on CXR?
o Eisenmenger’s physiology: MPA enlarged but remainder of pulmonary arteries small
What is the typical murmur for VSD?
“Blowing” Systolic murmur at right sternal border
What are CS that can results with right to left shunting?
Exercise intolerance, hypoxemia, polycythemia
What are 2 options to treat polycythemia?
Phlebotomy (to 62-65%)
Hydroxyura (bone marrow suppression)
Name 3 breeds that get pulmonic stenosis.
terriers, English bulldogs, Samoyeds, Chihuahuas, miniature Schnauzers, Labs, mastiffs, Chows, Newfoundlands, Basset hounds, Cockers; inherited in Beagles
What are the 3 types of pulmonic stenosis?
Subvalvular, valvular, supravalvular
What is a potential risk in certain breeds with pulmonic stenosis? Which breeds are affects?
· Anomalous left coronary artery (Bulldogs, Boxers):
o Single large coronary artery originates from right aortic sinus = divides into left/right
o Left coronary artery encircles MPA below valve = subvalvar obstruction
What is the most common murmur with pulmonic stenosis?
o Systolic murmur with PMI at left heart base; harsh ejection-quality crescendo-decrescendo
With moderate to severe pulmonic stenosis what would you see on CXR?
o Moderate to severe: RV enlargement, post-stenotic MPA dilation (DV > lateral)
Based on color doppler, velocity across pulmonary stenosis what are the grades?
§ PG = 4v2
§ Mild: up to 40-50mmHg
§ Moderate: 40-80 (or 100)mmHg
§ Severe: >80 (or 100) mmHg
What is potential medical treatment for pulmonic stenosis?
Treat CHF if present
Atenolol
What is the preferred treatment for pulmonic stenosis?
Balloon valvuloplasty
When should balloon valvuloplasty be considered for pulmonic stenosis?
o Should be performed ASAP = waiting only causes more RV hypertrophy
o Complication: “suicide right ventricle” = dynamic infundibular stenosis can become more severe following ballooning = increase in RV pressure as hypertrophied infundibulum creates subvalvar obstruction that can be worse than valvular obstruction)
o Bulldogs/Boxers with anomalous left coronary artery: ballooning can cause rupture of MPA and sudden death; can try less aggressive dilation, or surgical conduit around stenosis
What are potential major complications with balloon valvuloplasty?
o Major complications (rare): cardiac perforation, rupture of MPA, suicide RV, fatal arrhythmias
What are potential minor complications with balloon valvuloplasty?
Minor complications (more common): damaged TV, RBBB, temporary arrhythmias, hemorrhage from vascular access sites
Why can pressure gradients be higher following balloon valvuloplasty?
o PG may be higher after procedure vs. during (pulmonary valve leaflets can swell and cause increased obstruction; also, awake dogs have higher SV than anesthetized)
What is the long term prognosis for pulmonic stenosis if balloon valvuloplasty is performed?
Excellent (normal lifespans)
What is subaortic stenosis?
Fibrous lesion that partially or completely encircles subvalvular outflow tract
Which breeds get subaortic stenosis?
Newfoundlands (heritable; polygenic or autosomal dominant); GSD, Boxer, Golden, Rottweiler
What is important to consider about the pathogenesis of subaortic stenosis?
o Not present at birth; develops early in life (begins within 3 weeks) d/t morphologic abnormalities in LVOT that increase shear stress and induce proliferation of cells in LVOT; may progress for first 12mo
What are common complications with subarotic stenosis?
§ Severe: sudden death, arrhythmias (within 2-3 years)
§ Mild-moderate: infective endocarditis, CHF
What is the classic murmur for subarotic stenosis?
Left basilar systolic murmur
What can you feel in the pulses of animal with subaortic stenosis?
o Arterial pulses tardum and parvum (weak and late-rising)
Besides LV hypertrophy what can be seen on ECG for patient with subarotic stenosis?
ST segment depression suggests myocardial ischemia = Based on increased pressure gradient resulting in narrowed coronary vessles = myocardial ischemia
What can be seen on CXR in animals with subaortic stenosis?
post-stenotic dilation of ascending aorta
What is the primary diagnostic criterion for SAS on echo?
Peak Ao velocity is primary diagnostic criterion for SAS
§ Most think that >2.25m/s is definitely mild SAS; between 1.9-2.25m/s is grey zone
Which breed has a relative aortic stenosis and what is this?
Healthy Boxers: >50% have soft basilar ejection murmurs; those with murmurs have higher aortic velocities than dogs without murmurs = may be breed-related variance in outflow tract anatomic
What are the treatment options for SAS based on degree?
o Mild/moderate: not treated; generally have few complications and live normal lifespans
o Severe: often die suddenly from ventricular arrhythmias, but no good treatment option
Is there a benefit of balloon valvuloplasty in dogs with SAS?
NO! Not compared to atenolol alone
§ Presumed benefit of atenolol: decrease myocardial O2 demand (negative inotrope and chronotrope); improve myocardial perfusion during diastole; blunts SNS-instigated reflex-mediated syncope; may reduce arrhythmias?
What are the gradients for SAS grades?
§ Mild: 80mmHg
§ Pressure gradient is flow-dependent = depends on CSA and stroke volume (SNS activation will worsen apparent stenosis)
What is tricupsid valve dysplasia?
congenital malformation of right AV valve apparatus caused by abnormal tissue undermining of the RV during embryogenesis o Variety of abnormalities
§ Thickened, shortened, or elongated leaflets
§ Shortened or absent chordae tendinate
§ Abnormal papillary muscles
What is Ebstein’s anomaly?
Seen in animals that get tricspid dysplasia! congenital defect where origins of tricuspid leaflets are apically displaced into RV; may be associated with leaflet dysplasia; rare in vetmed
Which breeds get tricuspid valve dysplasia?
Labs (inheirted), Boxers, Goldens, Irish setters, Great Danes, GSD
What ECG abnormality is seen on 2/3 dogs with tricuspid valve dysplasia?
o Splintered QRS in 2/3 of dogs (mechanism unknown; may be ventricular fibrosis, RBB conduction disturbances, accessory pathway conduction) Atrial arrhythmias (APCs, AT, A flutter, Afib)
What is seen on CXR with tricuspid valve dysplasia?
o Right heart enlargement
o HUGE RA but normal MPA
What is treatment for tricupsid valve dysplasia?
o Instituted once R-CHF develops
o Furosemide, ACE-I, abdominocentesis, low Na+ diet, +/- pimobendan?
o Atrial fibrillation: digoxin, diltiazem
Balloon Valvuloplasty - reported twice was horrible!
What is the prognosis for dogs with tricuspid valve dysplasia?
depends on severity o Mild: may have normal lifespans
o Severe: R-CHF within a few years, though may survive >6yrs with treatment
What may be considered the #1 congenital cardiac abnormality in cats?
Mitral valve dysplasia
Which dogs breed get mitral valve dysplasia?
Great Danes, GSD, bull terriers, Goldens, Newfoundlands, Dalmatians, mastiffs
How is heart failure different from shock?
inability of the heart to maintain CO sufficient to meet tissue perfusion needs given adequate venous pressures (as distinguished from shock that has impaired venous return)
What happens during heart failure?
o Decreased CO and BP à trigger compensatory systems to maintain basal BP and target organ blood flow
§ SNS stimulation of heart
§ Vasoconstriction and redistribution of blood flow (SNS, RAAS, vasopressin, vascular endothelial systems)
§ Na+/water retention (RAAS, vasopressin, inhibition of natriuretic hormones)
o Chronic stimulation of control mechanisms à chronic states of vasoconstriction, Na+ retention, mediators of inflammation and tissue growth; heart remodeling (activation of fetal-gene programs, myocyte apoptosis, interstitial and replacement fibrosis)
What are the most common causes of heart failure in dogs?
MVD, DCM, pericardial disease, or HWD/PHT
What is the most common acquired heart disease in dogs?
Chronic valvular dz, Overall incidence > 40%
In which breed is chronic valvular disease considered to be genetic?
CKCS
Chronic valvular disease has generally been considered a non-inflammatory myxomatous vlave degeneration but newer evidence suggests what?
Role of serotonin, C-reactive protein, inflammatory cytokines, serotonin-transforming growth factor
What is the pathophysiology of chronic valvular disease?
valvular thickening → valvular regurgitation → dilation and hypertrophy of atria/ventricles → compensatory mechanisms (SNS, RAAS) to prevent CHF o CHF occurs when volume overload overwhelming, chordal rupture, or LV myocardial failure
o L-CHF can lead to PHT → R-CHF
Which sex is more effected by chronic valvular disease?
Males> females
What is known about treatment of asymptomatic dogs with chronic valvular disease with ACE-I?
Controversial (SVEP vs VETPROOF trials) - Generally only for moderate to severe cardiomegaly
What are the 3 mainstays for at home management of CHF?
Furosemide
ACE-I
Pimobendan