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Surgical Meeting

Cardiorespiratory focus

Carlos F. Agudelo

VFU – Brno

Cardiac arrhythmias

Carlos F. Agudelo

VFU – Brno

The arrhythmia

Importance

-Decrease in cardiac output: hypotension a decreased tissue and coronary perfusion

-Sign of extra-cardiac disease (trauma, inflammation, cancer)

-Sudden death

The arrhythmia

- Signalement

-Breed:

WHWT, Springer Spaniel, Boxer, Doberman, etc.

-Colour

- History

Exercise intolerance

Dyspnoea

Palpitations

Fanting episodes

Long term cardiac disease (drugs)

Trauma

Inflammation

Cancer (therapy)

- Clinical

Hypotension

Pale MM

Irregular heart beats

Pulse deficit

Sudden death

The arrhythmia

Ventricular arrhythmia

-Cardiomyopathy

-Myocarditis / endocarditis

-Myocardial hypoxia

-Congenital heart disease

-Digitalis intoxication

-Electrolytic abnormalities

-Hypothermia

-Systemic disease

Supraventricular arrhythmia

-Enlargement of the atria

-Myocarditis / endocarditis

-Ongoing heart disease

-Ischemic foci in the atria

-Drugs (digitalis, anesthetics)

-Abnormal AV pathways

-Systemic disease

The arrhythmia

Diagnosis

ECG Holter–event recorders

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The arrhythmia

Diagnosis

Atropine SC, IM, IV: 0.02–0.04 mg/kg

The arrhythmia

Classification according to…

1-Rhythm

2-Origin and transmission

3-Time interval

4-Frequency

5-Aetiology

…Rhythm

-Bradyarrhythmia vs. tachyarrhythmia

a) Sinus bradycardia - PQRST-

-trained individuals

-Increase vagal stimulation

…Rhythm

b) Sinus block - arrest

…Rhythm

c) Atrioventricular (AV) block

1st degree AV block

2nd degree AV block

M1

…Rhythm

2nd degree AV block

M2

3rd degree AV block

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…Rhythm

Tachycardia

a) Sinus tachycardia

…Rhythm

b) Atrial tachycardia

c) Ventricular tachycardia

…Origin and transmission

a) Supraventricular

Atrial premature complexes

Atrial fibrillation

…Origin and transmission

b) Nodal – junctional – escape complexes

Nodal complex

Nodal rytmus

…Origin and transmission

c) Ventricular Ventricular tachycardia Slow vent. tachycardia (accelerated idioventricular rhythm) Idioventricular rhythm

…Time interval…

-Premature

-Escape (after pauses)

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…Frequency

-Isolated

-Paroxismal

-Persistent

…pathology…

- Physiologic = sinus arrhythmia

…pathology…

b) Primary disease = DCM

…pathology…

-ARVD

…pathology…

c) Secondary – trauma / abdominal disease / hypoxic situations / neoplasia / drugs

Therapy

-Not only heart disease…

-Based on the history, clinical findings (auscultation, pulse palpation), blood pressure, laboratory findings, and others

-Each antiarrhythmic drug has also pro-arryhthmic effects

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Therapy

Supraventricular arrhythmias

-Physiologic or compensatory…be aware

-Vagal manoeuvre or thump

-Pharmacological intervention

Therapy

Supraventricular arrhythmias: APC, SVT, AF

-Acute onset of congestive heart failure

-Goal at home: dogs 120-150 beats/min; cats 200 beats/min.

-Some cases of pre-clinical DCM: β-blockers? Cardioversion?

Therapy

Supraventricular arrhythmias – acute management

-Diltiazem 0.25 mg/kg IV bolus over 2 minutes. Repeat bolus at 15 minute intervals until conversion (max. dose of 0.75 mg/kg).

-Verapamil 0.05 mg/kg slow IV bolus. Repeat boluses up to a total dose of 0.15 mg/kg.

-Esmolol (incremental doses of 0.05 to 0.1 mg/kg q 5 min up to a maximum dose of 0.5 mg/kg).

Therapy

AF – chronic therapy

- Digoxin – Dogs: 0,005-0,01mg/kg PO. SID-BID (dogs >20kg: 0,22 mg/m2). Maximal dose in Dobermans is 0.25 mg BID.

- Digoxin – Cats 0.0035 to 0.0055 mg/kg SID PO. ¼ tablet 0.125 mg (0.0312 mg/cat) PO in a 2-3 kg = ¼ q48h; 4-5 kg = ¼ SID; 6 kg or > = ¼ BID.

Levels are measured after 1 week of therapy (0.5-2 ng/ml). Watch out digoxin toxicity (about 15% of cases) and renal disease (decrease dose by 30-50%).

PLUS

- Diltiazem: dogs: 1-1.5 mg/kg PO, BID-TID, cats 7.5-15 mg/cat PO SID, BID

- ß-blockers (atenolol or metoprolol)

Therapy

AF – chronic therapy

-Cases with normal thoracic radiographs and echocardiogram = conversion back to sinus rhythm.

Quinidine: 6-11 mg/kg IM, PO, QID.

PLUS

Diltiazem or sotalol may convert atrial fibrillation to sinus rhythm in some dogs.

Amiodarone ?

Therapy Isolated VPCs.

-Treat ?

Dogs: No, however be aware of breed predisposition

Cats: Further investigate

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Therapy

Ventricular trigeminy – duplets and triplets.

Treat ? +/-

Yes: clinical signs or recent or known cardiac disease (predisposition)

No: without findings and normal heart frequency. Further investigation

Therapy

Monomorphic slow ventricular tachycardia (<180 beats/min) – ventricular bigeminity.

Treat ?

Yes: digoxin, clinical signs or recent or known cardiac disease (predisposition)

Therapy

Polymorphic ventricular tachycardia.

Treat ?

Yes

-Several locations. Be aware of worsening at any moment

Therapy

Ventricular tachycardia (heart frequence higher than 200 beats/min)

Yes

-Risk for sudden death

Therapy

Persistent ventricular tachycardia

Yes

-General myocardial dysfunction

-Sudden death

-Secondary pathology

Therapy

Ventricular tachycardia

-Lidocain: bolus 2,2 mg/kg slow IV. Max. 4 applications (total 8,8 mg/kg). Continue CRI (40-75[100] μg/kg/min)

-If ineffective = combination of different antiarrhythmic drugs

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Therapy

Ventricular tachycardia

If ineffective…

β-blockers

Esmolol: Bolus 50-100 μg/kg IV up to 500 μg/kg. Continue CRI 50-200 μg/kg/min (Tilley et al 2010).

Amiodarone: Bolus 3-5 mg/kg IV. Continue CRI 20-150 μg/kg/min (Ware et al 2011).

Therapy

*Ventricular tachycardia – chronic oral therapy

Metoprolol: 0,2-0,5 mg/kg BID

Amiodarone: 8 to 15 mg/kg BID for 7 days, then 5 to 10 mg/kg BID

Sotalol: 1-3,5 mg/kg PO, BID.

Atenolol: 0.75-1.5 mg/kg BID alone or in combination with mexiletinem (5-8 mg/kg BID-TID).

Therapy

Ventricular Fibrillation

-Immediate electrical defibrillation

-Drug therapy alone (virtually ineffective)

*Intravenous amiodarone (3-5 mg/kg) and magnesium (0.15-0.3 mEq/kg)

*Low doses of epinephrine

Therapy

Bradyarrhyhtmia.

Low probability of pacemaker implantation…

-sinus bradycardia,

-sinus arrest or block

-1st degree and some cases of 2nd AV blocks

Therapy

Bradyarrhyhtmia.

High probability of pacemaker implantation…

-Advanced 2nd AV block

-3rd AV block

-Sick sinus syndrome

Therapy

Bradyarrhyhtmia

-Negative = (no reaction) = pacemaker implantation

-Positive or limited pacemaker implantation

-primary problem

Salbutamol: 0,05 mg/kg PO, BID

Aminophillyn: 5-10 mg/kg PO, TID-QID (extended release)

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Questions?