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RUSVM LAM1 > Cardiovascular > Flashcards

Cardiovascular Flashcards

1
Q

Where should you see a normal jugular pulse in a horse?

A

Lower third of the neck, when head in upright position

Will migrate towards upper neck when head is down

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2
Q

If a jugular pulse is seen lower/distal to where the vessel is being occluded, where the segment should be drained, is a sign of??

A

Regurgitation into and or from RA

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3
Q

The cardiac silhouette is located between the _________ intercostal spaces

A

2-6 th

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4
Q

T/F: it is normal to hear more than two heart sounds in a horse

A

True

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5
Q

The first heart sound “lub” is associated with what function of the heart?

A

Closure of AV valves

Initial movement of the ventricles and opening of semilunar valves

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6
Q

The second heart sound “dub” is associated with what function of the heart?

A

Closure of semilunar valves

Some due to opening of AV valves, can be split in horse

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7
Q

The third heart sound “ahh” is due to what function of the heart?

A

End of rapid filling phase

-deceleration of rapid filling

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8
Q

The fourth heart sounds “ba” is due to what function of the heart?

A

Atrial contraction

Heard most in resting horses where PR interval > 0.28sec

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9
Q

What are the PMI for cardiac valves?

A

Mitral - left 5th ICS, halfway/midway between elbow and shoulder
Aortic - left 4th ICS, just below point of shoulder
Pulmonary - left 3rd ICS, just cranial and ventral to aortic PMI

Tricuspid - 3-4th ICS, halfway/midway between shoulder and elbow

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10
Q

What are possible causes of diminished/absent cardiac sounds?

A

Increased tissue density

Pericarditis, pulmonary consolidation, diaphragmatic hernia

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11
Q

Radiating cardiac sounds indicated?

A

Pleural effusion of consolidation

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12
Q

What is the normal heart rate for a horse at rest?

A

26-44bpm

A more fit racehorse can have a lower HR (26-36)
Sedentary/older will have 40-44bpm

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13
Q

What is the preferred method of evaluating he equine heart?

A

Ultrasonography-echocardiography

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14
Q

What cardiac enzyme, when elevated, indicates cardiac muscle disease/compromise?

A

Cardiac troponin I

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15
Q

What are the general differentials for an arrhythmia?

A

Pathological arrhythmia of primary or secondary cause (drug/toxin )
Primary cardiac disease —> myocardial or valvular involvement
Metabolic abnormalities
—> electrolyte : potassium and calcium
—> acid base balance
—> autonomic system imbalance

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16
Q

What is a dysarrythmia?

A

Abnormality of impulse generation, conduction, or both

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17
Q

The ability of the SA node to initiate action potentials spontaneously is called??

A

Automaticity

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18
Q

Changes in automaticity can result in dysrhythmia, what can cause these changes?

A

Alterations of nervous system tone (eg increased vagal tone)

  • > most commonly results in sinus tachycardia/bradycardia
  • > control HR and rhythm in response to arterial BP

Alterations in electrolyte status
-> presence of drug or disease

Enhanced automaticity
-> ectopic foci

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19
Q

What are the two types of ectopic foci ?

A

Spontaneous impulse generation from a discrete site

Triggered arrhythmias
—> caused by one or more impulses from outside the ectopic focus
—> exacerbated by fast HR and can be very irregular

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20
Q

What feature of the equine heart allows re-entry of impulses leading to abnormal condition?

A

Large heart size

Can be random or ordered r-entry —> likely cause of atrial and ventricular fibrillation

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21
Q

Activation of the parasympathetic system decreases heart rate how??

A

Affects membrane potential of pacemaker cells of SA and AV node

Hyperpolarize the AV node and reduce transmission
PSNS predominates during rest in the horse

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22
Q

Where are the leads placed when doing an ECG on a horse?

A

Lead 1 - Base to apex

Positive (black) on left thorax at ICS 5 at the level of the elbow (apex beat)
Negative (white) in the right jugular furrow 2/3 from ramus IV mandible
Ground (red) any point remote from the heart

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23
Q

How does a typical ECG output appear in a horse??

A

P is usually positive- often bifid
Ta wave (atrial repolarization) -> negative deflection after the P
QRS usually negative
Large positive T wave

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24
Q

Horse with bradycardia but cyclic arrhythmia

RR intervals vary cyclically?

A

Sinus arrhythmia

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25
Q

Sinus bradycardia (HR<28) in the horse is usually the result of?

A

Vagal tone : waxing and waning of vagal tone with respiration

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26
Q

Arrhythmias with regular variations in rhythm?

A

AV block

Sinoatrial block or arrest

27
Q

What is the most common manifestation of high vagal tone in the normal horse?

A

Second degree Mobitz type I - AV block (gradual increase from S4 and S1 before beat is dropped)

Generally physiological and will resolve with increased sympathetic tone (jogging horse)

28
Q

T/F: a Mobitz type II AV block is always pathological

A

True

29
Q

ECG

P waves are not followed by QRS
Gradual prolongation of PR before dropped

A

Second degree AV block - Mobitz type I

30
Q

ECG

P waves not followed by QRS
Fixed PR interval

A

2nd degree AV block - Mobitz type II

31
Q

ECG

Complete AV dissociation
Rapid regular P waves with normal configuration
QRS complex is wide and bizarre with T waves oriented in opposite direction

A

Third degree AV block

32
Q

What is the treatment and prognosis for third degree AV block?

A

Requires electrical pacing

Grave

33
Q

T/F: high resting vagal tone is likely to be the cause of sinoatrial block/arrest

A

False

34
Q

How can you determine if an arrhythmia is due to high vagal tone vs pathological?

A

If due to high vagal (PSNS) —> you can increase the SNS tone by jogging or scaring patient and the arrhythmia should disappear

35
Q

What is the most common PATHOLOGICAL arrhythmia in the horse?

A

Atrial fibrillation (AF)

36
Q

Why are horses predisposed to development of atrial fibrillation in NORMAL atrial tissue???

A

Large syncytium of atrial cells (large atrial mass)

Relative inhomogeneity of atrial refractories associated with underling vagal tone: enhances chances of re-entry

37
Q

How do horses with Afib usually present?

A

Racehorse with

  • exercise intolerance
  • tachypnea
  • EIPH (exercise induced pulmonary hemorrhage)
  • CHF
  • collapse
  • myopathy, colic
38
Q

What are the two forms of atrial fibrillation?

A

Paroxysmal - occurs during race and can disappear with deceleration of the HR (possible associated to transited potassium depletion)

Sustained

39
Q

ECG

Baseline fibrillation waves
QRST with normal morphology but irregularly spaced
No P waves

A

Atrial fibrillation

40
Q

How can you diagnose Afib?

A

Auscultation: irregularly irregular rhythm, absent S4
Variable pulse strength due to irregular time interval between each beat

Cardiac troponin if there is cardiac injury

ECG- fibrillation waves with no P valves and irregularly spaced QRST

41
Q

Horse in Afib..
HR>60bpm

What is your treatment?

A

Digoxin and Qunidine

42
Q

Horse in Afib
HR<60bpm and a normal echo

What is your treatment? ?

A

Quinidine only

43
Q

Horse in Afib
HR <60bpm
Echo shows abnormalities

Treatment?

A

Digoxin and quinidine

Quinidine is tachyarrythmogenic
Digoxin slows HR

44
Q

If the duration of Afib is longer than 72hrs, which formulation of Qunidine should you use?

A

Oral formulation

Less than this, can use the IV formulation

45
Q

What is the MOA of quinidine?

A

Sodium channel blocker

  • > increase myocardial refractory period
  • > decreased conduction velocity

also vasolytic and peripheral vasodilator

46
Q

What are the toxic effects of using digoxin with Qunidine??

A

Qunidine is highly protein bound, can displace digoxin and increase incidence of digoxin toxicity

—> prolonged QRS interval

47
Q

What are signs of Qunidine toxicity?

A

GIT signs
Neurological behavior

Cardiac signs: widening of QRS and 25% prolonged interval

Idiosyncratic rxn: supraventricular tachycardia

48
Q

How can Qunidine toxicity be treated?

A

Digoxin
Sodium bicarbonate (promote Qunidine binding)
MgSO4 (for cardiotoxicity)

49
Q

How would you treat a superventricular tachycardia due to quinidine treatment for Afib?

A

HR> 200bpm —> therapy immediately required
Digoxin and bicarb

If poor pressure then give phenylephrine
If HR remains high you can administer propranolol

50
Q

To avoid an idiosyncratic reaction to quinidine, how will you initially dose your horse?

A

Give 5mg test dose

If there is no rxn give 20-22mg/kg every 2 hours until converted

51
Q

When should you stop quinidine therapy?

A

Once converted
OR
If toxic side effects present OR after 4-6 treatments at 2 hr intervals

52
Q

Before beginning treatment with Qunidine, we want to check what electrolyte status?

A

potassium

—> low potassium can lead to Afib (seen in horses given furosemide pre-race for EIPH or oral bicarb )

53
Q

What are some alternative therapies to quinidine and digoxin for treatment of Afib?

A

Transvenous electrocardioversion (TVEC)
Flecaninide (10% success rate)
Amiodarone (58% success rate)

54
Q

What is the prognosis for a horse with a Afib of <4months duration and no other cardiac disease?

A

100% conventions and low recurrence (25%)

55
Q

What is the prognosis for horses with HR<60bpm with Afib duration <4months, and low grade murmur?

A

95% conversion

25% recurrence

56
Q

What is the recurrence rate for horses with Afib lasting longer than 4months?

A

60% recurrence rate

57
Q

What are possible etiologies associated with development of VPC or VTs?

A 
Myocarditis, myocardial necrosis or fibrosis 
Bacterial endocarditis 
Autonomic nervous system abnormalities 
Electrolyte or metabolic disturbances 
Anesthesia
Sepsis/endotoxemia
Toxic myocardial injury
58
Q

What clinical signs are associated with ventricular tachycardia?

A

Exercise intolerance, can lead to syncope
Repaid HR with regular/irregular rhythm

HR can be as high as 300bpm

59
Q

Auscultation
Rapid regular rhythm with varying intensity

Jugular pulse deficits
Syncope

Dx?

A

Ventricular tachycardia

60
Q

When is treatment for VT indicated?

A

If causing clinical signs while at rest

Rate excessively high (>120bpm)
Rhythm multiform: ectopic ventricular compels originates from more than one focus, irregular R-R
R on T complexes detected

61
Q

What is the treatment for VT ?

A

Lidocaine

-administered IV

62
Q

What side effects can lidocaine cause in the horse?

A

Hyperexcitability and seizure

63
Q

What therapy can be used for refractory VT?

A

Propafenone

64
Q

What rhythms are associated with electrical instability and can result in Vfib or cardiac arrest?

A

Mutiform VT
R on T
Tornadoes de pointes

RUSVM LAM1 (17 decks)

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