Sports Med Papers

Question 1

What are the max heart rate values in exercising horses and does it decrease through training?

Answer 1

maximal values of HR in the region of 210–240 beats/min (Vincent et al. 2006).

Training does not alter the horse’s maximal HR (HRmax). However, the speed at which HRmax is reached does increase with training

Although HRmax itself does not change with training, the speed at which a specific HR is reached does increase with training.

Question 2

Is there an association between heart size and race performance

Answer 2

scientific evidence has confirmed associations of

left ventricular size with

• maximal oxygen capacity (VO_ 2 max) and
• race performance

(Young et al. 2002, 2005; Buhl et al. 2005).

Question 3

Are elite athletes less prone to heart disease?

Answer 3

There is increasing evidence of cardiac damage in athletes undertaking extreme exercise and this may explain why elite human athletes (Maron 2003; La Gerche 2013), dogs (Bharati et al. 1997) and horses (Kiryu et al. 1999; Young 2013) may be more susceptible to arrhythmias and sudden cardiac death (SCD).

Question 4

typical hert rates for diff exercise levels

Answer 4

Walk 60–80

Trot 80–120

Canter 120–180

Gallop >180

Question 5

What is characteristic for recovery of the heart rate after exercise?

Answer 5

Heart rate recovery decreases in a bi-exponential manner (Rugh et al. 1992) (Fig 1).

Recovery is usually very rapid in the first minute after cessation of exercise, followed by a slower decline towards resting levels.

conflicting evidence if the speed of recovery is related to fittness of the horse

Question 6

Most common reason for abnormally high peak or maximal HR during exercise

Answer 6

: the most common condition causing supraphysiological HRs (>250 beats/min) is atrial fibrillation (paroxysmal or sustained).

Question 7

Interpretation of T waves in exercise testing

Answer 7

T waves are very labile and change in size and polarity with alterations in HR and sympathetic tone. Consequently analysis of their changes during exercise has no clinical value.

. An increase in T wave amplitude is seen during exercise and, as HRs progressively increase, the P waves disappear into the preceding T waves

Question 8

Describe the waves on this ECG

Answer 8

Electrocardiography recording in the immediate recovery period. The heart rate is now slowing and P waves become increasingly visible on the edge of the T waves (red arrow).

normally its is hidden within the T wave (large positive wave)

Question 9

What can you see in this ECG

etiology?

Answer 9

Sinus arrhythmia: A phasic increase and decrease in the PP interval is seen (Figs 7 and 8).

In contrast to other species, sinus arrhythmia is not associated with ventilation in horses. It is most commonly seen in the immediate recovery period after moderate or strenuous exercise particularly if the horse is brought back to halt or walk very quickly. In this context, the rhythm probably reflects nonlinear return of parasympathetic influence.

Question 10

normal regularly irregular rhythms in the horse

Answer 10

Sinus block: The normal sinus impulse is blocked at the sinus node resulting in a regular pause that is twice the preceding PP interval

Second degree atrioventricular block: The ECG shows an isolated P wave that is not associated with a QRS complex because the impulse is blocked at the atrioventricular (AV) node

Question 11

what does this ECG show?

Answer 11

Electrocardiogram obtained in the immediate post exercise period showing second degree atrioventricular block. There are 3 consecutive nonconducted P waves (red arrows).

Question 12

What does this ECG show?

Answer 12

Electrocardiogram from a collapsing horse that had paroxysmal atrial fibrillation during exercise. The RR interval is irregular, no P waves are visible and F waves can be seen in the longer RR intervals.

Question 13

When does atrial fib typically occur?

Answer 13

Atrial fibrillation can be

• sustained or
• paroxysmal.

irregularly irregular RR intervals, the absence of P waves and presence of F waves.

onset of paroxysmal atrial fibrillation is typically during or immediately after strenuous exercise (Fig 13), generally, most horses revert spontaneously back to sinus rhythm within 24–48 h. However, horses have spontaneously reverted as long as 1 week after the onset of paroxysmal atrial fibrillation.

Question 14

What does this ECG show?

Answer 14

A supraventricular premature complex. The QRS is of similar morphology as the normal complexes. As supraventricular premature complexes are similar to the normal QRS they are more easily missed. The 2 electrocardiography traces above are identical but the second image also has the computer generated electrocardiography analysis marks. The red line highlights the premature complex. Equipment with this facility aids recognition of supraventricular complexes. The numbers show instantaneous heart rate.

Question 15

characteristics of a supraventricular premature complex

what is supraventricular tachycardia?

Answer 15

also known as atrial premature complex: early beat originating from the atrial myocardium.

• difference in P wave morphology sometimes (As the premature complex does not originate from the sinus node):
  
  • P wave hidden in the preceding QRS complex
  • premature P waves blocked at the AV node (through strong vagal influence)
• morphology of the QRS complex is the same as that of sinus beats (differentiation between SVPCs and ventricular premature complexes (VPCs).
• changes in the QRS somteimes:
  
  • If the P wave of the premature complex coincides with the preceding QRS or T wave, this may cause a slight change in the configuration of the QRS or T.
  • Also, for very closely coupled beats, the QRS of the premature beat can on occasion be taller than the sinus complexes (Broux et al. 2013);
• noncompensatory pause. less useful in horses for differentiating SPVCs and VPCs because on many occasions the sinus node resumes at a slower rate.
• Supraventricular (atrial) tachycardia is defined as a run of 4 or more SVPC

Question 16

What does this ECG show?

Answer 16

Ventricular premature complexes can occur as isolated beats, couplets or triplets (Fig 17). Four or more consecutive VPCs are termed ventricular tachycardia

Question 17

What does this ECG show?

Answer 17

post exercise ecg with two obvious VPC (red) and two smaller ones (blue)

Question 19

Ventricular premature complex

Answer 19

VPC is an early beat that originates from the ventricular myocardium or conducting system and the QRS morphology typically differs from that of sinus beats (higher amplitude/longer duration/abnormal morphology)

presence of a compensatory pause is not truly diagnostic for VPCs. (dont rely on it)

no P waves

Question 20

Prevalence of arrhythmias during exercise

Answer 20

Supraventricular premature contractions are the most common arrhythmias detected during exercise. They are more commonly observed during the warm up phase (Ryan et al. 2005) but have been reported to occur in 10–50% of Thoroughbreds and Standardbred racehorses during strenuous exercise – either in training, racing or on the treadmill

Isolated VPCs have also been reported, albeit less commonly, in 3–4.5% of racehorses during strenuous exercise

Question 21

Prevalence of arrhythmias after exercise

Answer 21

Arrhythmias have been more commonly identified during the immediate post exercise period than during the exercise period itself.

In one study of healthy Thoroughbred racehorses during training 15% had second degree AV block and at least 28% had sinus arrhythmia in the post exercise period. Approximately 8% had VPCs or SVPCs in the post exercise period, and couplets, triplets and paroxysms were observed (Ryan et al. 2005). Similarly, following strenuous treadmill exercise 31% of horses had VPCs and 15% had SVPCs in the immediate recovery period.

Question 22

Effect of arrhythmias on athletic performance

Answer 22

A reduction in cardiac output is the primary mechanism through which a cardiac arrhythmia might affect athletic performance.

Atrial fib has an effect on performance

nobody is sure about SVPCs and VPCs

Question 23

Which arrythmias are associated with Risk of collapse/ Sudden cardiac death

Answer 23

Ventricular arrhythmias are assumed to be the primary cause of SCD in horses

Horses with SVPCs do not appear to be at increased risk of collapse or SCD. However, it is thought that frequent SVPCs during or after exercise are a risk factor for atrial fibrillation (Hiraga and Kubo 1999). In rare cases, horses with atrial fibrillation may collapse or die during exercise. This has been reported in horses with both sustained (Deem and Fregin 1982; Lyle et al. 2010) and paroxysmal AF

Question 24

What is max oxygen consumption and how is related to exercise?

Answer 24

defined as the point where no further increase in VO_ 2 is elicited despite further increases in speed

In horses, maximal oxygen consumption has been shown to be correlated with speed in Thoroughbreds

a higher VO_ 2max has been found in superior Standardbred racehorses compared with slower performing horses

Question 25

There are two main approaches to the assessment of blood lactate in exercise testing

And what is the cutoff value for aerobic exercise?

Answer 25

1. calculation of the velocity at which a lactate concentration of 4 mmol/l is achieved (VLa4) in order to make an assessment of the aerobic capacity and hence performance potential of an individual.

In horses, most disciplines, including ‘sprint’ races over five furlongs, are predominantly aerobic in nature (Eaton et

Several studies have shown that a high VLa4 value is associated with superior performance in Standardbred racehorses (Courouce et al. 1997; Leleu et al. 2005; Lindner 2010). Repeated measures of VLa4 during a training program are also useful for monitoring fitness

2. second approach is to use lactate measurements as a marker of anaerobic capacity. In human athletes, the use of post exercise lactate concentration has been used as an indicator of anaerobic capacity and higher peak lactate concentrations are an indicator of superior sprinting ability. (not much work done in horses)

Question 27

change in arterial blood gases during exercise

Answer 27

Little change in arterial blood gases occurs during walk and trot but at canter PaO2 decreases to approximately 80–85 mmHg and during strenuous exercise may decrease to 65–70 mmHg, whilst PaCO2 increases to 50– 55 mmHg

Question 28

This study examined the association between riding speed and elimination in Fédération Equestre Internationale (FEI) endurance events.

35000 horses

Answer 28

loop = individual stages

Faster riding speeds, especially during loops 1 and 2, were associated with deleterious outcomes. Furthermore, sudden drops in riding speed during loop 3 were associated with an increased likelihood of elimination.

Question 29

Fédération Equestre Internationale endurance events: Risk factors for failure to qualify outcomes at the level of the horse, ride and rider

Answer 29

h increased likelihood of failure to qualify due to lameness included age of horse 9 years, male horse, male rider, field size 61 horses and if the ride was held in region group II (Northern and Eastern Europe)

Question 30

Prevalence of adverse events and their effect on completion of high speed treadmill exercise tests at a single institution (2000–2015)

Answer 30

infrequent

The majority of horses presenting for HSTM evaluation underwent exercise testing (900/1003; 90%). Eight-hundred and seven (90%) exercise tests were completed. Adverse events occurred in 136 (15%) HSTM exercise tests of which 97 (71%) did not impact ability to complete HSTM testing. Adverse events significantly but variably decreased the likelihood of HSTM exercise test completion. Sixty-six percent of incomplete exercise tests were prematurely terminated due to poor performance abnormalities during which diagnosis of poor performance cause(s) was still achieved.

Question 31

Effect of induced chronic atrial fibrillation on exercise performance in 9 Standardbred trotters

Answer 31

Atrial fibrillation resulted in a significant reduction in performance, an increase in HR and development of abnormal QRS complexes during exercise, which may be a risk factor for collapse or sudden cardiac death.

Question 32

Cobalt chloride (CoCl2) is administered to racehorses to enhance performance. The purpose of this study was to evaluate the clinical, cardiovascular, and endocrine effects of parenterally administered CoCl2

Answer 32

The degree of hypertension and arrhythmia observed after IV CoCl2 administration raises animal welfare and human safety concerns.

Question 33

Race performance following epiglottic entrapment surgery in Thoroughbred yearlings

66

Answer 33

Thoroughbred racehorses treated in their yearling year for epiglottic entrapment had no differences in performance variables compared to their untreated cohort. Epiglottic entrapment with abnormal right arytenoid movement might decrease odds of racing post-operatively.