Cardiovascular Flashcards
Papers 2015-2019 JVIM, VCNA, JFMS,JVECC
What drugs are used for rate control of Afib?
Beta- blockers (class II)
- Atenolol
- Esmolol
K+ channel blocker (class III)
- Sotolol
- Amiodarone
Ca++ Channel blockers Class IV)
- Diltiazem
And digoxin
VCNA 2017. AFib Pariaut
What options are used for rhythm control of Afib?
Electric cardioversion
Lignocaine Na++ channel blocker ( class 1b) Amiodarone k+ channel blocker (class III)
VCNA 2017. AFib Pariaut
What are the causes of Afib?
Structural heart disease Lone AFib (giant and large breed dogs, structural normal heart with erratic rhythm with significant exercise +/- GA) High vagal tone (shortens the refractory period) Hypothyroidism Anaesthesia/opiates Rapid, large vol pericardial effusion GI disease Vol overload causing atrial stretch
VCNA 2017. AFib Pariaut + ettinger
Diltiazem mechanism of action?
Class IV antiarrhythmic; calcium-channel blocker (like verapamil or nifedipine).
- Inhibits the transmembrane influx of extracellular calcium ions in myocardial cells and vascular smooth muscle but does not alter serum calcium concentrations.
=> inhibit the cardiac and vascular smooth muscle contractility, thereby dilating main systemic and coronary arteries.
=> Decreased Total peripheral resistance, blood pressure, and cardiac afterload - Effects on cardiac conduction.
- slows AV node conduction
- prolongs refractory times.
Diltiazem rarely affects SA node conduction, but in patients with sick sinus syndrome (contraindicated) resting heart rates may be reduced.
Although diltiazem can cause negative inotropic effects, it is rarely of clinical importance (unlike verapamil or nifedipine). Diltiazem apparently does not affect plasma renin, aldosterone, glucose, or insulin concentrations.
Reduction in ventricular response rate is dose dependant.
Risk of hypotension
Plumbs
Sotolol : What is the mechanism of action?
- Non-selective beta-blocker
- Class III antiarrhythmic agent - potassium channel blocker:
selectively inhibiting potassium channels => prolongs repolarization and refractoriness without affecting conduction.
In supraventricular tachycardias, sotalol may be more effective in preventing recurrence of the arrhythmia rather than terminating it.
Plumbs
Where does an AV block originate from?
Conduction abnormalities along the AV nodes, bundle of His/Purkinje system or both.
Santilli JVIM 2016
What are the causes of AV nodal conduction abnormalities in dogs?
- Chronic fibrous or fibrous-fatty replacement of av bundles and branches
- Acute lymphoplasmacytic myocarditis (young dogs - Lev’s disease) with mild fatty-fibrous replacement
- infectious disease (Borrelia burgdorferi, bartonella vinsonii, bacterial endocardititis, parasitic - Trichinella spiraliz
- Immune med disease (MG, SLE)
- Neoplasia
- non-penetrating chest trauma
Santilli JVIM 2016
What proportion of dogs with AV nodal conduction disturbances had unchanged or progressed AV blocks after pacemaker implantation?
87%
Santilli JVIM 2016
In what dogs with AV conduction disturbances should pacemaker be considered the first line treatment?
High second degree AV block
Third degree AV block
2:1 second degree AV block
Santilli JVIM 2016
What proportion of dogs with AV noda conduction disturbances showed regression after pacemaker implantation?
What proportion of these returned to a normal sinus rhythm
13%
67%
consider acute lymphocytic myocarditis as a possible cause for these?
Santilli JVIM 2016
What drug is most effective at reducing progression to CHF or sudden death in Irish Wolfhounds with preclinical DCM, Afib or both?
Pimobendan > digoxin > benazepril
Vollmar JVIM 2016
What is the median time to CHF or sudden death in Irish Wolfhounds with preclinical DCM, Afib or both treated with:
- Pimobendan?
- Digoxin?
- Benazepril?
P: 1991 days (65m or ~5.5years)
D: 1263 days (41m or ~ 3.4 years)
B: 997 days (32m or ~ 2.6 years)
Vollmar JVIM 2016
Is there any evidence for starting pimobendan in preclinical DCM in Irish Wolfhounds?
Yes - Vollmar JVIM 2016 found improved survival and significantly longer to sudden death or CHF in wolfhounds receiving pimobendan preclinical DCM and/or Afib
Vollmar JVIM 2016
For every 10 bpm increase in HR with dogs with Afib, what is the risk of all cause mortality increased by?
35%
Pedro JVIM 2018
What is the median survival time of dogs with AFib and a mean heart rate (measured by Holter)
- <125 bpm
- > 125bpm
<125 bpm = 1037 days
>125 bpm = 105 days
Pedro JVIM 2018
What is a benefit of Holter monitoring of Afib over ECG?
Holter monitoring allows ambulatory montiroing outsite the hospital setting, more accurately representing the dogs normal daily HR flucutations in its usual routine/environment.
ECG tents to over-estimate mean HR compared to Holter recordings in dogs with AFib
Pedro JVIM 2018
What Heart rate target should be aimed for with Holter readings in dogs with Afib?
<125 bpm
Pedro JVIM 2018
What are the options and aims for control of AFib?
Rhythm control: abolish the arrhythmia and restore sinus function:
- Electrical cardioversion
- Lignocaine
- Amiodarone
Rate control: - slow ventricular rate to reduce clinical signs and minimize deteriorationg of ventricular function
- Atenolol
- Esmolol
- Sotolol (mild)
- Diltazem
- Digoxin (mild)
VCNA 2017. AFib Pariaut
What does lignocaine do?
Lidocaine may also have benefit in dogs to terminate supraventricular tachycardia in the presence or absence of an accessory pathway and paroxysmal atrial fibrillation initiated by elevated vagal tone in large breed dogs with normal cardiac function
Class IB antiarrhythmic agent (membrane-stabilizing).
- combines with inactive fast sodium channels, => inhibits recovery after repolarization.
rapid rates of attachment and dissociation to sodium channels in ventricular conducting tissue more so than atrial tissue.
At therapeutic levels, lidocaine causes phase 4 diastolic depolarization attenuation, decreased automaticity, and either a decrease or no change in membrane responsiveness and excitability. These effects will occur at serum levels that will not inhibit the automaticity of the SA node, and will have little effect on AV node conduction or His-Purkinje conduction.
Plumbs
What is the mechanism of action of Atenolol?
What are the effects of Atenolol?
Relatively specific β1-blocker. At higher dosages,β2 blockade can occur.
Effects:
- no intrinsic sympathomimetic activity or membrane-stabilizing activity
- Negative inotropic and chronotropic actions =>
- decreased sinus heart rate,
- slowed AV conduction,
- decreased cardiac output at rest and during exercise,
- decreased myocardial oxygen demand,
- decreased blood pressure,
- inhibition of isoproterenol-induced tachycardia
Plumbs
What is the mechanism of action of Esmolol?
What effects does this drug have?
Class II antiarrhythmic drug.
Short acting beta1-adrenergic receptor blocker
- antiarrhythmic effect is thought to be due to its blockade of adrenergic stimulation of cardiac pacemaker potentials
- no intrinsic sympathomimetic activity or membrane-stabilizing activity
Cardiovascular effects include:
- negative inotropic and chronotropic activity
=> reduced myocardial oxygen demand.
- reduced systolic and diastolic blood pressures
- increases sinus cycle length,
- slows AV node conduction,
- prolongs sinus node recovery time.
Plumbs
What is the mechanism of action of Amiodarone?
Class III
- potassium channel blocker
- also blocks sodium and calcium channels and beta-adrenergic receptors.
Causes:
- prolongation of myocardial cell action-potential duration and refractory period.
Plumbs
What is the mechanism of action of Digoxin?
Suspected:
- increase the availability of Ca++ to myocardial fibers and to inhibit Na+-K+-ATPase with resultant increased intracellular Na+ and reduced K+
This leads to:
- decreased conduction velocity through the atrioventricular (AV) node
- prolonged effective refractory period (ERP).
+/- increase the PR interval, decrease the QT interval, and ST segment depression on ECG.
Plumbs
What are the effects of digoxin?
In patients with a failing heart includes:
- increased myocardial contractility (inotropism) with increased cardiac output;
- increased diuresis with reduction of edema secondary to a decrease in sympathetic tone;
- reduction in heart size, heart rate, blood volume, and pulmonary and venous pressures; and (usually) no net change in myocardial oxygen demand.
What is the mechanism of action of Pimobendan?
Pimobendan is an inodilator, with both positive inotropic and vasodilator effects via inhibition of PDE-3 and increasentracellular calcium sensitivity in the cardiac contractile apparatus.
- decreases heart rate (negative chronotrope)
- Increased contractility without increased myocardial oxygen consumption, as pimobendan does not increase intracellular calcium levels.
Pimobendan’s vasodilator effects are via vascular PDE-III inhibition, +/-
activity against phosphodiesterase V and increase cGMP
Slight antithrombotic activity
Plumbs
What is the best technique to measure HR in dogs with AFib?
24h Holter monitor
VCNA 2017. AFib Pariaut
What are urgent rate control drugs for dogs with AFib?
- Diltazem IV boluse or CRI * risk hypotension
- Esmolol CRi. * less effective.
VCNA 2017. AFib Pariaut
Long term rate control drugs for dogs with AFib?
- Diltazem
+/- Digoxin or Sotolol - Atenolol (cats)
What are the rhythm control strategies for dogs with AFib?
- Lignocaine Bolus (first line for acute termination of vent. tachycardia)
- Amiodarone CRI or oral * allergic reactions or increased ALT
- Synchronised electrical cardioversion.
What is the benefit of using a biphasic shock with cardioverter-defibrilators as opposed to monophasic shocks to convert AFib?
- less energy
- Higher success rates than monophasic shock
What needs to be done before cardioversion can be performed?
- IV access
- Airways management
- Lignocaine for V tachy
- Adropine ofr unexpected bradycardia
- Correct electrolyte impances including Mg
- adequate oxygenation
- GA (no opioids due to effect on vagal tone)
- paddles attached (dorsal recumbency at level of atria not ventricles)
- shock delivered at peak of R wave.
If an electrical cardioversion shock is delivered at the peak of the T-wave, what can occur?
Increased risk of V-Fib
What phase of the ECG should the electrical cardioversioin be synchronised with?
Peak of the R-wave.
How much energy is required for cardioversion?
1-2 J/kg for 1-2 to 10 shocks.
What is the KCNQ1 gene mutation associated with?
Sudden death during exercise due to QT interval prolongation in English springer spaniels. (increased symp stimulation = increased risk)
Single heterozygous base pair mutation from threonine to lysine => change in protein structure to slow and fast outward potassium channels and fast inward sodium channel.
Ware JVIM 2015
What are causes of prolonged QT interval?
- inherited
- Drugs
- Electrolytes disturbances
- toxins
- Infectious
- inflammatory
- autonomic impanance
- metabolic disease.
Ekectrophysioloigcially:
factors that delay repolarization prolong the QT interval including
- reduced outward K+ during phases 2 and 3, esp slow K+ or rapid K+ components => can trigger VPC
- increased inwards NA+ or Ca++ current during depolarization.
Ware JVIM 2015
What does the QT interval represent?
The time of ventricular depolarization and repolarization on the ECG
Ware JVIM 2015
What drugs may be helpful in precenting syncope and sudden death in patients with QT interval prolongation?
Beta blockers - used in people.
Ware JVIM 2015
What are the major complications commonly seen with pacemaker implantation?
- Lead dislodgement
- lead or generator infection
- lead or generator migration
- pacing failure
Ward JVIM 2015
What circumstances have been associated with higher risk of complications with pacemaker implantation?
- At night
- pre-existing structural heart disease
- post-op infections
- previously used generators
- inexperienced operators.
Ware JVIM 2015
What are the most common indications for pacemaker implantation in dogs?
- High grade second degree AV block (3:1 conduction or less)
- third degree AV block
Ware JVIM 2015
What is the inicidence of sudden death in dogs with high grade AV block without pacemaker?
up to 40% within 6 months of diagnosis.
Ware JVIM 2015
Familial boxer ARVC is associated with a deletion in which gene? What is the method of inheritance
Striatin gene. Autosomal dominant.
Meurs VCNA 2017
What treatment is generally used for boxer ARVC?
Sotalol +/- Mexiletine or Amiodarone INI with above \+/- Fish oil If CHF treat as for DCM - pimobendan - ACEi - diuretics - L-Carnitine
Meurs VCNA 2017
What is the most common age of onset for boxer ARVC?
Adult between 5-7 years, however homozygous dogs may present between 1-3 years old.
Meurs VCNA 2017
Striatin gene deletion mutation causes what disease?
ARVC - Boxers
Meurs VCNA 2017
What is Striatin and how does it cause ARVC?
Striatin is localizedin the intercalated disks of cardiac myosytes where it co-localizes to 3 desmosomal proteins. Desmosomes help adhere myocytes in the heart => structural integrity
Abnomal desmosomal adhereance => myocyte death, inflam and replacement with fibrous tissue.
Thus ARVC is a degenerative myocardial disease with RV myocoyte atrophy and fatty infiltration.
Meurs VCNA 2017
What are the different types of ARVC?
- Asymptomatic with occasional VPC
- Tachyarrhythmia and clinical signs such as syncope or exercise intolerance
- Myocardial systolic dysfunction and ventricular dilation +/- CHF. Least common, more likely homozygous form
Meurs VCNA 2017
Are biomarkers useful in detection of ARVC in boxers?
Troponin I: inconsistent but when elevated can correlate with VPC number and grade or complexity of the arrythmia
BNP: only useful in boxers with myocardial dysfunction
Meurs VCNA 2017
ARVC: what is the diagnostic screening criteria for ARVC based on Holter monitoring?
Asymptomatic dog:
0-20 single VPC per 24h = wnl
20-100 VPC per 24h = indeterminate. repeat in 6-12m
100-300 single VPCs per 24h = suspicious
100-300 VPC per 24h with increased complexity (couplets, triplets, V.tach) = likely affected.
300-1000 single VPC per 24h = likely affected
>1000 VPC per 24h = affected, consider treatment
Meurs VCNA 2017
ARVC: What screening tests are recommended?
- Holter monitor
- Genetic test for striatin deletion.
Meurs VCNA 2017
ARVC: what does a negative striatin genetic test mean?
This dog does not carry the Striatin deletion mutation and thus will not develop ARVC because of the striatin deletion but can still develop ARVC or heart disease.
Meurs VCNA 2017
ARVC: What does a positive heterozygous Striatin genetic test mean? What monitoring is recommended? What breeding is recommended?
At risk of developing ventricular arrhythmia and sudden death. Variable expression => only 40-60% of dogs will develop clinical signs.
Recommended monitoring:
- annual Holter monitor after 4 years of age,
- avoid breeding or only breed to negative
Meurs VCNA 2017
ARVC: WHat does a positive homozygous Striatin genetic test mean? What monitoring is recommended? What breeding is recommended?
2 copies of Striatin gene mutation. Most likely to: - develop the disease - develop at younger age. - develop ventricular dilation and systoilci dysfunction stage of the disease
Recomended monitoring:
- annual holter +/- echo from 3 years old.
- do not use for breeding.
Meurs VCNA 2017
What criteria are used for prognostic significance on Holter ECG?
For dogs with structurally normal hearts >50VPC per 24h, polymorphic VPCs and the presence of VTach have been associated with shorter survival times.
Meurs VCNA 2017
ARVC: Are TXR likely to be abnormal?
No unless generalized cardiomegaly and CHF - pulmonay oedema and or pleural effusion.
Meurs VCNA 2017
What echocardiographic finding may be a useful prognostic factor in ARVC?
TAPSE - tricuspid annual plan systolic excursion.
Lower in boxers with >50 VPC per 24h.
Lower TAPSE associated with more severe disease and shorter survival times.
Meurs VCNA 2017
Is echocardiography generally useful in diagnosing ARVC?
Not generally as most myocardial changes are histological only, however may see:
- right ventricular enlargement
- right ventricular dysfunction
- lower TAPSE (tricuspid annual plane systolic excursion)
Meurs VCNA 2017
What are the histological findings of ARVC?
Fibrofattym segmental or diffuse replacement of the right ventricular free wall from the epicardium towards the endocardcium +/- IVS and LVFW.
Meurs VCNA 2017
What Holter findings in an asymptomatic dog would indicate commencing treatment for ARVC?
- Sustained VTach > 30 seconds.
- increased complexity of arrhythmia including frequent couplets, triplets, bigeminy and/or Ront.
- > 1000 VPC
Meurs VCNA 2017
What level of day to day variability has been noted with VPC in affected, untreated boxers with ARVC?
83% change in VPC number from day to day.
Meurs VCNA 2017
ARVC: On post treatment holter monitor, what % reduction in VPCs is aimed for?
80% reduction in VPCs and reduction in complexity
Meurs VCNA 2017
ARVC: What does an increase in symptoms or increase in number of VPCs per 24h on post-treatment Holter monitor suggest?
Proarrhythmogenic effects of medications. must compare to pre-treatment holter.
Meurs VCNA 2017
What are prognostic indicators for boxer ARVC associated with shorter survival times?
- Echo: - left vent systolic dysfunction and TAPSE <15.1mm
- Holter: - increased frequency and complexity of VPCs inc VTach and Polymorphic VPCs
Kaye JVIM 2015
Is TAPSE lower or higher in Boxers with ARVC or dogs with left ventricular dysfunction?
lower
Kaye JVIM 2015
TAPSE ……… mm in boxers with >5o VPC/24h on Holter is associated with ……. cardiac survival times and is an independant predictor of …… irrespective of the presence of CHF, echo evidence of LV systolic dysfunction and Holter detection of VT.
TAPSE <15.1 mm is associated with shorter cardiac survival times and is an independant predictor of time to cardiac death irrespective of the presence of CHF, echo evidence of LV systolic dysfunction and Holter detection of VT.
Kaye JVIM 2015
MMVD: What clinical signs have been identified as negative prognostic indicators?
- cough,
- exercise intolerance,
- decreased appetite,
- breathlessness/difficulty breathing
- syncope
- Mumur > III/VI
- absence/loss of respiratory sinus arrhythmia
lopez-alvarez JVIM 2015
MMVD: What other changes (apart from clinical signs) have been associated with higher risk of CHF?
- increase NT-proBNP
- enlarged heart size
- LA enlargement
lopez-alvarez JVIM 2015
What histopathological changes are seen with MMVD CHF in the lungs?
- Thickened alveola septum (all ISACHC classes)
- Increased Type II pneumocytes (All ISACHC classes)
- Increased heart failure cells (alveolar macrophages with phagocytosed extravasated RBCs) in class III and above.
Lee JVIM 2015
What histopathological changes are seen with MMVD in the left atrium?
Fatty replacement
Inflammatory cell infiltration
fibrosis
secondary to metachic strech and schear stress by regurg jets => inflamm and thus
- Migration of leukocytes (chemotaxis for phagocytosis)
- Formation of scar tissue (fibrosis for healing)
- Fatty replacement (lipomatous metaplasia)
Lee JVIM 2015
What histopathological changes are seen with MMVD in the left ventricle?
- few inflammation related change
- increased cellular hypertrophy secondary to compensatory myocardial hypertrophy,
May effect LVEDd and EF.
Lee JVIM 2015
What are the most common breeds in the UK to be diagnosed with MMVD?
CKCS King Charles Spaniel Chihuahua Whippet Poodle
Mattin JVIM 2015
What are the most common breeds in the UK t be diagnosed with a heart murmur?
CKCS King Charles Spaniel Chihuahua Boxer Whippet
Mattin JVIM 2015
What is the prevalence of MMVD in the UK?
0.35%
Mattin JVIM 2015
What is the prevalence of heart murmur in the UK?
3.54%
Mattin JVIM 2015
Do males or females have higher odds of developing MMVD in the UK?
Males OR 1.40
Mattin JVIM 2015