Cardio Flashcards
What does the ausculation reveal with AF ?
Auscultation reveals an irregularly irregular rhythm with absence of the fourth heart sound due to the lack of active atrial contraction.
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
What does the ECG reveal with AF ?
The surface ECG typically shows an irregularly irregular rhythm with normal QRS morphology, the absence of P waves and the presence of coarse or fine undulations of the isoelectric line (fibrillation “f” waves).
The HR at rest is normal in horses in which no underlying cardiac abnormalities are detected.
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
What does the ECG reveal during exercise with AF ?
- The HR increases disproportionally during exercise or stress, as the HR variability.
- ECG during exercise can detect abnormal QRS complexes or R-on-T-like phenomenon due to aberrant conduction and/or ventricular premature depolarisations
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
Which horses should be treated for cardioversion ?
Aim at cardioversion of the abnormal rhythm to sinus rhythm.
* Especially recommended in competition and racehorses (high intensity exercise)
* Not recommended in horses without clinical signs, performing low intensity exercise and not presenting abnormal ventricular responses (conflicting)
* Not recommended in horses with severe underlying heart disease or congestive HF, as the risk of recurrence is very high
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
When horses should be treated for cardioversion ?
- Cardioversion should not be performed within the first few days after onset of AF, as the arrhythmia might be paroxysmal.
- After the first few days, treatment should not be delayed since the electrical, contractile and structural remodelling during AF makes the arrhythmia more stable and more difficult to treat.
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
How to realise cardioversion ?
Pharmacological cardioversion :
* quinidine sulphate administered orally, with an overall success rate ∼ 80%
* flecainide, amiodarone or novel atrial specific compounds.
Transvenous electrical cardioversion (TVEC), with a success rate of >95%.
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
What are the mechanisms of action of Quinidine sulfate ?
- Quinidine sulphate is a class 1A antiarrhythmic drug, which mainly blocks the sodium channels and to a lesser extent various potassium channels. As a result, the action potential duration is prolonged and the myocardial brillation threshold is increased.
- Anticholinergic effects → atrioventricular nodal conduction increases, which results in an increased ventricular response rate during treatment.
- Overall success rate ∼ 80%
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
What are the side effects of Quinidine sulfate ?
Reported in ∼ 45% of treated horses with 1% mortality
Cardiac side effects :
* Supraventricular or ventricular tachycardia, which may require cessation of the therapy. Digoxin can slow down the AV nodal conduction.
* Hypotension through a negative inotropic effect and alpha-adrenergic blockade
* Pro-arrhythmic properties → QRS and QT prolongation. Stop TT if QRS > 25%
* Torsade de pointes, collapse, sudden death
Non-cardiac side effects :
* Nasal edema, depression, mild tachycardia (< 120 bpm)
* Colic, diarrhea, weakness, ataxia, laminitis
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
What are the clinical efficacy of flecainide for cardioversion ?
Flecainide is a potent sodium channel blocker. Rate of cardioversion ∼ 41% with dangerous ventricular arrhythmias and sudden deaths reported.
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
What are the clinical efficacy of amiodarone for cardioversion ?
- Amiodarone is a multichannel blocker affecting sodium, calcium and several potassium channels as well as having a beta-blocking effect.
- Overall success rate for cardioversion ∼ 58%
- Adverse effects such as temporary hindlimb weakness and diarrhea
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
What are the clinical efficacy of TVEC for cardioversion ?
Very high success rate (>95%), even in horses with a prior unsuccessful pharmacological treatment attempt.
Successful in horses with focal or macro-re-entrant atrial tachycardia (AT)
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
What are the negative prognostic indicators following the cardioversion ?
During the days after cardioversion → presence of atrial premature depolarisations and short runs atrial tachycardia assoc. with recurrence.
One study found APD ≧ 25 during 24h ECG recording at 5 days post TVEC → sign assoc. with AF recurrence within 1 year.
Also found LA active fractional area change ≦ 9.6% and lower body weight at 5 days post TVEC → sign assoc. with AF recurrence within 1 year.
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
Atrial premature depolarisations five days post electrical cardioversion are related to atrial fibrillation recurrence risk in horses
evj 2020
What are the risk factors for AF recurrence ?
- Longer AF duration
- Larger atrial size +/- fibrosis
- Atrial electrophysiological remodelling
- Previous unsuccessful TT attempt
- Mitral regurgitation
- Shortened AF cycle length (AFCL) or increased AF rate
Atrial brillation in horses Part 2: Diagnosis, treatment and prognosis
Vet J 2021
Which blood parameters are associated with higher grade arrhythmias during peak exercise ?
Both partial pressure of arterial CO2 (PaCO2) and lactate were significantly associated with arrhythmias occurring at peak exercise, but not immediately post-exercise. As PaCO2 and lactate increased, arrhythmia severity increased.
Hypercapnia and hyperlactatemia were positively associated with higher-grade arrhythmias during peak exercise in horses during poor performance evaluation on a high-speed treadmill
Vet J 2020
Is a horse with paroxysmal AF at greater risk of recurrence?
Thoroughbreds are at increased risk of recurrent AF after both paroxysmal and persistent episodes than for horses with no previous episode, but the duration of time between episodes varies widely.
Median duration between episodes was 343 days (range, 34-1065).
Recurrence was seen in 64% of horses previously treated for persistent AF, which was higher than recurrence in horses with paroxysmal AF (23%).
Incidence, recurrence, and outcome of postrace atrial fibrillation in Thoroughbred horses
JVIM 2021
