Cardio

Question 1

What does the ausculation reveal with AF ?

Answer 1

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

Question 2

What does the ECG reveal with AF ?

Answer 2

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

Question 3

What does the ECG reveal during exercise with AF ?

Answer 3

• 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

Question 4

Which horses should be treated for cardioversion ?

Answer 4

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

Question 5

When horses should be treated for cardioversion ?

Answer 5

• 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

Question 6

How to realise cardioversion ?

Answer 6

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

Question 7

What are the mechanisms of action of Quinidine sulfate ?

Answer 7

• 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

Question 8

What are the side effects of Quinidine sulfate ?

Answer 8

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

Question 9

What are the clinical efficacy of flecainide for cardioversion ?

Answer 9

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

Question 10

What are the clinical efficacy of amiodarone for cardioversion ?

Answer 10

• 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

Question 11

What are the clinical efficacy of TVEC for cardioversion ?

Answer 11

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

Question 12

What are the negative prognostic indicators following the cardioversion ?

Answer 12

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

Question 13

What are the risk factors for AF recurrence ?

Answer 13

• 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

Question 14

Which blood parameters are associated with higher grade arrhythmias during peak exercise ?

Answer 14

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

Question 15

Is a horse with paroxysmal AF at greater risk of recurrence?

Answer 15

Thoroughbreds are at increased risk of recurrent AF after both paroxysmal and persistent episodes compared to 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

Question 16

Which of these factors may predispose horses with atrial fibrillation to develop EIPH during exercise?
A. Increased left atrial pressure
B. Decrease in myocardial contractility
C. Increased circulating volume
D. Increased cardiac output

Answer 16

Which of these factors may predispose horses with atrial fibrillation to develop EIPH during exercise?
A. Increased left atrial pressure
B. Decrease in myocardial contractility
C. Increased circulating volume
D. Increased cardiac output

Associations between postrace atrial fibrillation and measures of performance, racing history and airway disease in horses | Nath, Laura C. Elliott, Adrian Gerche, Andre La Weir, Joe Forbes, Grace, | JOURNAL OF VETERINARY INTERNAL MEDICINE 2023

Question 17

Horses with AF can have :
A. Increased frequency and severity of EIPH and low prevalence of clinically important tracheal mucus accumulation (TMA)
B. Increased severity of EIPH and high prevalence of clinically important TMA
C. Decreased severity of EIPH and high prevalence of clinically important TMA
D. Decreased severity of EIPH and low prevalence of clinically important TMA

Answer 17

Horses with AF can have :
A. Increased frequency and severity of EIPH and low prevalence of clinically important tracheal mucus accumulation (TMA)
B. Increased severity of EIPH and high prevalence of clinically important TMA
C. Decreased severity of EIPH and high prevalence of clinically important TMA
D. Decreased severity of EIPH and low prevalence of clinically important TMA

Associations between postrace atrial fibrillation and measures of performance, racing history and airway disease in horses | Nath, Laura C. Elliott, Adrian Gerche, Andre La Weir, Joe Forbes, Grace, | JOURNAL OF VETERINARY INTERNAL MEDICINE 2023

Question 18

Based on a study examining atrial fibrillation (AF) in racehorses, which of the following statements is correct?

A) Horses with AF had lower career earnings before the event compared to horses performing as expected (TE).
B) The volume of exercise was a significant factor contributing to AF in racehorses.
C) Horses with AF were more likely to have a higher grade of exercise-induced pulmonary hemorrhage (EIPH) compared to horses with poor performance but without AF (PP).
D) Age was not a significant factor when comparing horses with AF to those performing to expectation (TE).

Answer 18

Based on a study examining atrial fibrillation (AF) in racehorses, which of the following statements is correct?

A) Horses with AF had lower career earnings before the event compared to horses performing as expected (TE).
B) The volume of exercise was a significant factor contributing to AF in racehorses.
C) Horses with AF were more likely to have a higher grade of exercise-induced pulmonary hemorrhage (EIPH) compared to horses with poor performance but without AF (PP).
D) Age was not a significant factor when comparing horses with AF to those performing to expectation (TE).

Associations between postrace atrial fibrillation and measures of performance, racing history and airway disease in horses | Nath, Laura C. Elliott, Adrian Gerche, Andre La Weir, Joe Forbes, Grace, | JOURNAL OF VETERINARY INTERNAL MEDICINE 2023

Question 19

Which of these pathological arrhythmias have been found during swimming and active recovery?

A. AF and supraventricular premature depolarization
B. Supraventricular premature depolarization and ventricular premature depolarisation
C. Ventricular tachycardia and supraventricular premature depolarization
D. Ventricular tachycardia and ventricular premature depolarisation

Answer 19

B. Supraventricular premature depolarization and ventricular premature depolarisation

Frequency of cardiac arrhythmias in horses during straight and untethered swimming Emma Santosuosso | Florent David | Shannon Massie | Silvio A. Filho |Persephone McCrae | Sarah Johnson | Renaud Leguillette, EQUINE VET EDUC, 2022

Question 20

Which of these are considered proarrhythmogenic factors during swimming?
A. Apneic breathing, facial immersion, hypotension
B. Apneic breathing, facial immersion, diving exercise
C. Tachypnea, facial immersion, hypertension
D. Tachypnea, hypertension, stress

Answer 20

B. Apneic breathing, facial immersion, diving exercise

Frequency of cardiac arrhythmias in horses during straight and untethered swimming Emma Santosuosso | Florent David | Shannon Massie | Silvio A. Filho |Persephone McCrae | Sarah Johnson | Renaud Leguillette, EQUINE VET EDUC, 2022

Question 21

Which of the following statements is correct regarding the breathing strategy and upper respiratory tract (URT) behavior in swimming horses, as observed in a prospective study?

A) Horses showed URT collapse both during swimming and overground exercise.
B) Horses exhibited a complete collapse of the URT, including the external nares, nasopharynx, and rima glottidis, during apnoea while swimming.
C) Locomotor-respiratory coupling was observed during both swimming and overground exercise.
D) Post-swim plasma lactate levels were lower than pre-swim levels, indicating minimal exertion during swimming.

Answer 21

B) Horses exhibited a complete collapse of the URT, including the external nares, nasopharynx, and rima glottidis, during apnoea while swimming.

Frequency of cardiac arrhythmias in horses during straight and untethered swimming Emma Santosuosso | Florent David | Shannon Massie | Silvio A. Filho |Persephone McCrae | Sarah Johnson | Renaud Leguillette, EQUINE VET EDUC, 2022

Question 22

What is the most appropriate definition of accelerated idioventricular rhythms in horses?
A. Persistent or intermittent tachycardia with HR ranging from 50 to 100 beats/min, often abates at exercise or with sympathetic stimulation.
B. Persistent tachycardia with HR > 100 beats/min, often abates at exercise or with sympathetic stimulation.
C. Irregular rhythm with HR > 100 beats/min, often it doesn’t disappear at exercise or with sympathetic stimulation.
D. Regular rhythm with HR < 100 beats/min, often abates at exercise or with sympathetic stimulation.

Answer 22

A. Persistent or intermittent tachycardia with HR ranging from 50 to 100 beats/min, often abates at exercise or with sympathetic stimulation.

Diagnosis and management of accelerated idioventricular rhythms in horses Elizabeth Williams Louie1 | Katharyn J. Mitchell, EquinE Veterinary Journal, 2023

Question 23

Which of the following could be an adequate treatment in the case of accelerated idioventricular rhythms that does not resolve spontaneously?

A. Sodium and calcium channel blockers (lidocaine/lignocainehydrochloride) and beta blocker
B. Sodium and calcium channel blockers (lidocaine/lignocainehydrochloride) and magnesium sulphate.
C. Potassium channel blocker (amiodarone) and magnesium sulfate.
D. Calcium channel blocker (diltiazemil) and magnesium sulfate.

Answer 23

B. Sodium and calcium channel blockers (lidocaine/lignocainehydrochloride) and magnesium sulphate.

Diagnosis and management of accelerated idioventricular rhythms in horses Elizabeth Williams Louie1 | Katharyn J. Mitchell, EquinE Veterinary Journal, 2023

Question 24

What are the most prevalent arrhythmias during the race : APC or VPC ?
When arrhythmias are the most prevalent : during or after the race ?

Answer 24

During the race, 92% of horses had arrhythmias (81% APC ; 33% VPC).
During active-recovery, 58% of horses had arrhythmias (56% APC ; 15% VPC)

Prevalence of cardiac arrhythmias and R-R interval variation in healthy
Thoroughbred horses during of cial Chuckwagon races and recovery
Vet J 2021

Question 25

What is the maximal R-R variation reported during the race ?
* 15 %
* 25 %
* 35 %
* 45 %

Answer 25

What is the maximal R-R variation reported during the race ?
* 15 %
* 25 %
* 35 %
45 %
And 40% during the active recovery

Prevalence of cardiac arrhythmias and R-R interval variation in healthy
Thoroughbred horses during of cial Chuckwagon races and recovery
Vet J 2021

Question 26

What is the goal of Implantable loop recorders ? In which anatomical location ?

Answer 26

This study indicates that ILRs can be used for detection of PAF episodes and could be a useful ECG tool for horses presenting with poor performance.
During submaximal exercise only the sixth left intercostal space position was able to record ECG signals of diagnostic quality. No position yielded diagnostic signals at maximum exercise due to artefacts.

Implantable loop recorders can detect paroxysmal atrial
fibrillation in Standardbred racehorses with intermittent poor
performance
evj 2021
Detection of atrial fibrillation with implantable loop recorders in horses
Technical notes - evj 2021

Question 27

What is the impact of URT obstructions on the cardiac rythm of racehorses ?

Answer 27

Exercise-associated upper respiratory tract obstructions increase the risk of rhythm disturbances.

Exercise-associated rhythm disturbances in poorly performing Thoroughbreds: risk factors and association with racing performance
evj 2021

Question 28

What factor could be used to predict complex ventricular arrhythmias during recovery ?

Answer 28

The maximum average HR during peak exercise was an excellent predicter for complex ventricular arrhythmias during recovery.

Cardiac arrhythmias in poorly performing Standardbred and Norwegian–Swedish Coldblooded trotters undergoing high-speed treadmill testing
Vet J 2021

Question 29

Which procedural factors should be considered for TVEC ?

Answer 29

Catheter type, previous AF episode, tricuspid regurgitation, and body weight were significantly correlated with cumulative amount of energy delivered.
Both horse and procedural factors should be considered when assessing treatment options and prognosis in horses with AF.

Transvenous electrical cardioversion of atrial fibrillation in horses: Horse and procedural factors correlated with success and recurrence
JVIM 2022

Question 30

Which sex seems to be predisposed to reccurrence after TVEC ?

Answer 30

Stallions (RR 3.05)

Transvenous electrical cardioversion of atrial fibrillation in horses: Horse and procedural factors correlated with success and recurrence
JVIM 2022

Question 31

Where is located the focal source of AT in most horses, using electro-anatomical mapping ?

Answer 31

In 8 out of 9 horses, AT originated from a localized macro-reentrant circuit (n= 5) or a focal source (n= 3) located at the transition between the right atrium and the caudal vena cava.
The source of right atrial AT in horses was safely treated by radiofrequency catheter ablation.

Detection of the origin of atrial tachycardia by 3D electro-anatomical mapping and treatment by radiofrequency catheter ablation in horses
jvim 2022

Question 32

What is the difference between the atrial fibrillatory cycle length and atrial fibrillatory rate ?

Answer 32

Atrial remodelling → shortening of the atrial effective refractory period (aERP) and thus shortening of atrial fibrillatory cycle length (AFCL). Can be measured invasively with a catheter placed in the atrium.
The atrial fibrillatory rate (AFR) measures the number of fibrillations (f waves) per minute (fpm) and is inversely correlated with AFCL. The AFR can be measured noninvasively from surface ECG recordings.

Atrial fibrillatory rate as predictor of recurrence of atrial fibrillation in horses treated medically or with electrical cardioversion
jvim 2022

Question 33

How atrial fibrillatory rate can be useful for AF horses ?

Answer 33

High AFR is associated with failure of quinidine cardioversion and AF recurrence after successful TVEC.

Atrial fibrillatory rate as predictor of recurrence of atrial fibrillation in horses treated medically or with electrical cardioversion
jvim 2022

Question 34

What changes in cardiorespiratory parameters are observed during peak exercise in AF horse?

Answer 34

• Lower maximum velocity
• Higher HR
• More abnormal QRS complexes
• EIPH (horses with AF had increased frequency and severity of EIPH)

Atrial fibrillation as a risk factor for exercise-induced pulmonary haemorrhage following a standardised exercise test
evj 2023
Associations between postrace atrial fibrillation and measures
of performance, racing history and airway disease in horses
jvim 2023

Question 35

What is the impact of arrhythmias on HR variability parameters during exercise ?

Answer 35

The presence of arrhythmia increased HRV in submaximal and strenous exercise, and recovery (RMSSD and SDRR).
Lameness decreased HRV during submaximal exercise.

Heart rate variability during high-speed treadmill exercise and recovery in Thoroughbred racehorses presented for poor performance
evj 2023

Question 36

What are the differences in type and frequency of arrhythmias recorded during training vs racing ?

Answer 36

None.
The total number of arrhythmias was repeatable between training and racing, but the reliability of arrhythmia type was poor to moderate.
Race-simulated training elicits the same physiological response as competition in Chuckwagon horses.

Training vs. racing: A comparison of arrhythmias and the repeatability of
findings in Thoroughbred Chuckwagon racehorses
Vet J 2023

Question 37

Why pulmonary veins can play a role in AF of horses (and humans) ?

Answer 37

Conductive tissue with gap junctions and adrenergic and non-adrenergic nerve fibres is present within the entire myocardial sleeve in all pulmonary vein ostia.

Morphological and histological investigation of the conduction system in the equine atrial muscle sleeve of pulmonary veins
evj 2024

Question 38

During the cross-country phase of eventing, what is related with premature depolarisations nb and complexity ?
A- The duration of exercise
B- Upper levels of eventing and respiratory rate
C- The amount of time the HR > 199 bpm and upper levels of eventing
D- Event duration and history of collapse

Answer 38

C- The amount of time the HR > 199 bpm and upper levels of eventing

Premature depolarisations in horses competing in United States Eventing Association and Fédération Equestre Internationale-sanctioned 3-day events
evj 2024

Question 39

Which structures have myocardial sleeves that could be a potential trigger for initiation and perpetuation of AT and AF?

Answer 39

Caudal vena cava and pulmonary veins
Isolation of these myocardial sleeves by radiofrequency catheter ablation may be an effective treatment for these arrhythmias.

Successful caudal vena cava and pulmonary vein isolation in healthy horses using 3D electro-anatomical mapping and a contact force-guided ablation system
evj 2024

Question 40

Which drugs have been used before and during TVEC to prevent recurrence ?

Answer 40

• Sotalol : prolonged QT interval, which entails potential risks combined with anesthesic drugs. No longer used in Ghent.
• Amiodarone : should only be used before or during TVEC in case of unsucceessful cardioversion or high risk of recurrence, and preferably in the absence of sotalol co-treatment. Hypotension.

Anti-arrhythmic drugs before, during and after transvenous electrical cardioversion of atrial fibrillation in horses: Weighing the benefits and risks (Clinical commentary)
eve 2024

Question 41

Which drugs have been used after TVEC to prevent recurrence ?

Answer 41

• Sotalol
• Amiodarone
• Propafenone
• Phenytoin

Anti-arrhythmic drugs before, during and after transvenous electrical cardioversion of atrial fibrillation in horses: Weighing the benefits and risks (Clinical commentary)
eve 2024

Question 42

What was the primary method used to accurately locate the accessory pathway (AP) in the horse treated for ventricular pre-excitation?

A) 12-lead electrocardiogram (ECG) only
B) Echocardiography
C) Three-dimensional electro-anatomical mapping (3D EAM)
D) Continuous 24-hour ECG monitoring

Answer 42

Correct Answer: C) Three-dimensional electro-anatomical mapping (3D EAM)

Justification:
The correct answer is C) Three-dimensional electro-anatomical mapping (3D EAM), as it was the primary tool that enabled precise localization of the AP by identifying the earliest site of ventricular activation, which is essential for targeting the correct location during ablation. The text states, “3-dimensional electro-anatomical mapping (3D EAM) and RFCA, using the CARTO 3 System…were used to identify and treat the AP” and “This procedure identified an AP at the right cranial free wall between the right atrium and right ventricle”​

Three-dimensional electro-anatomical mappingand radiofrequency ablation as a novel treatment foratrioventricular accessory pathway in a horse: A case report 2022

Question 43

In the first successful high-density 3D electroanatomical mapping of the right atrium in standing horses, which of the following was used as a positional reference during the procedure?

A. The left atrium
B. A 10-pole catheter in the caudal vena cava
C. The P-wave on the surface ECG
D. The sinoatrial node

Answer 43

Correct Answer: B. A 10-pole catheter in the caudal vena cava

Justification:

Option A is incorrect: The study focused on mapping the right atrium, not the left atrium.
Option B is correct: A 10-pole catheter was placed in the caudal vena cava to serve as a positional reference during the mapping procedure.
Option C is incorrect: The P-wave on the surface ECG was used as a timing reference, not a positional reference.
Option D is incorrect: The sinoatrial node was one of the areas mapped, but it was not used as a positional reference.

First catheter-based high-density endocardial 3D electroanatomical mapping of the right atrium in standing horses 2020

Question 44

In the study of ultra-high-density 3D electro-anatomical mapping in horses, which chamber required additional tools, such as a deflectable sheath, to successfully complete mapping?

A. Right atrium
B. Left atrium
C. Right ventricle
D. Left ventricle

Answer 44

Correct Answer: B. Left atrium

Justification:

Option A is incorrect: There was no mention of the right atrium requiring additional tools for mapping.
Option B is correct: The study noted that the left atrium was the most challenging chamber to map, requiring the use of a deflectable sheath.
Option C is incorrect: The right ventricle did not require additional tools according to the study.
Option D is incorrect: The left ventricle was mapped successfully, but there was no mention of extra tools needed for it.

More info :Mild elevations in cardiac troponin I were observed post-procedure, indicating some myocardial stress.

Three dimensional ultra-high-density electro-anatomical cardiac mapping in horses: methodology 2020