The Cardiac Patient

Question 1

In a shelter population, non-selected and apparently healthy, what is the prevalence of congenital heart disease in both dogs and cats?

Answer 1

Reported at approximately 1 in 1000 dogs and cats [ 0.13% in dogs and 0.14% in cats]

Question 2

For a young & juvenile patient, aside from congenital conditions, what other cardiovascular diseases have been reported?

Answer 2

1. Dilated cardiomyopathy (DCM), such as in a Portuguese water dog which has been reported to be autosomal recessive.
2. Myocarditis

Question 3

What are some of the most commonly reported infectious etiologies reported to induce myocarditis, particularly in the young patient?

Answer 3

parvovirus, distemper virus, toxoplasma, neospora, spirochetes such as borrelia (Lymes disease), leptospirosis, and bartonella (cat scratch fever), and trypanosoma cruzi (Chagas disease).

Question 4

Describe how a young patient diagnosed with myocarditis: (1) typically presents (e.g. clinical signs and features) and (2) if they survive, what echocardiogram features they display?

Answer 4

(1) presents as heart failure with marked arrhythmias.

(2) If they survive, they may present with a scarred, hypofunctional heart which has a “DCM phenotype”.

Question 5

For the adult animal population, why are most heart diseases likely to present as acquired?

Answer 5

The short answer relates to “age-dependent penetrance”.

In other words, there is an underlying genetic substrate or predisposition, but compounding components related to epigenetics (e.g. other genes, environment, lifestyle, etc) increase the likelihood of that genotype being expressed.

Question 6

In the REVEAL study by Fox et al. 2018, what is the median age in cats diagnosed with HCM?

Answer 6

According to the study, the median age of cats diagnosed with HCM is approximately 5 - 7 years of age. This means that 50% of the cats are older (30% were >10 years of age) and 50% were younger.

Question 7

In the paper, “Prevalence of DCM in Doberman Pinschers in Various Age Groups” by Wess et al 2010, what is the reported age of this breed to be diagnosed with DCM?

Answer 7

According to the study, the prevalence of DCM in Doberman Pinschers is up to 6-years of age (e.g. <12%), but raises to >44% after 6+ years.

Question 8

In the presumptive diagnosis of an acquired or congenital cardiac condition, what auscultation principles can be applied to suggest one or the other?

Answer 8

Most acquired cardiomyopathies present with a systolic, left apical murmur in dogs and a sternal murmur in cats.

However, if a diastolic, right-sided or basilar murmur is appreciated, congenital disease is considered more likely.

Question 9

In the paper entitled, “Prevalence of and Risk Factors of degenerative MMVD in dogs attending primary care veterinary practices in England” by Mattin et al. 2015, what is the median age on onset of diagnosis with myxomatous mitral valve disease (MMVD)?

Answer 9

Mattin and colleagues report a diagnosis in dogs around 9.5 years.

Question 10

In Stage A MMVD breeds, such as the Cavalier King Charles Spaniel, what is the reported prevalence in this breed to develop MMVD according to Darke 1987?

Answer 10

The study reported that CKCS first reported murmurs present in around half of the dogs over 4-years old, which increased to 100% of the population at age 10-years of more.

Question 11

With regards to gender, which gender group (male or female) has a higher predisposition in the development of cardiac diseases?

Answer 11

Almost all heart disease has a male sex predisposition.

Question 12

According to the REVEAL study Fox et al 2018 in the population of 1,730 cats with feline HCM, what is the reported proportion of affected MALE cats to develop HCM?

Answer 12

71% of affected cats with HCM are male.

To note, testosterone concentration is unlikely to be the primary factor because most cats are neutered at the time of becoming sexually mature.

Question 13

What is the reported percentage of MALE dogs in the development of DCM?

Answer 13

60% of dogs with DCM are male.

Question 14

What is the reported prevalence of the congenital cardiac condition, patent ductus arteriosus (PDA), with regards to gender?

Answer 14

Female sex predisposition to PDA is widely acknowledged, with around 3:1 (F:M) developing this congenital disease.

Question 15

With regards to the Doberman Pinscher, DCM and gender, how do males typically die? What about females?

Answer 15

Male Doberman Pinschers diagnosed with overt DCM and heart failure

Female Doberman Pinschers diagnosed with DCM die suddenly, presumable to ventricular arrhythmias.

Question 16

What other cardiac condition has been reported to be proportionally higher in females than males?

Answer 16

Sick sinus syndrome.

Question 17

What is the most commonly reported congenital heart condition reported in dogs and what specific group of dogs report a higher frequency of this disease?

Answer 17

Pulmonic stenosis

It is common in brachycephalic breeds, but may also be diagnosed in the Cocker Spaniel and Terrier breeds

Question 18

For conditions such as (sub)aortic stenosis, what breeds and size of dogs are typically reported?

Answer 18

SAS/AS tends to be diagnosed in larger breed dogs, but occasionally is identified in brachycephalic dogs.

Its worth noting that valvular aortic stenosis is much less common than SAS and seems to be almost exclusively described in the Bull terrier and Boxer Breeds.

Question 19

What congenital heart condition is likely to be diagnosed in a non-pedigree dog?

Answer 19

PDA.

Question 20

What dog breeds are overrepresented for the development of a VSD?

Answer 20

Labrador retrievers, GSDs, and French bulldogs.

Question 21

What dog breeds are overrepresented for the development of Tetralogy of Fallot?

Answer 21

Beagles, Basenji, Keeshonds and French bulldogs.

Question 22

What dog breeds are overrepresented for the development of tricuspid valve dysplasia?

Answer 22

Golden Retrievers, Labrador Retrievers

Question 23

What dog breeds are overrepresented for the development of mitral valve dysplasia?

Answer 23

Bull terrier and springer spaniel.

Question 24

What cat breed is overrepresented for the development of both: pericardio-peritoneal diaphragmatic hernias and VSDs?

Answer 24

Persians.

Question 25

For myxomatous mitral valve disease (MMVD), what breeds are commonly diagnosed?

Answer 25

Small breed dogs, most commonly toy breeds, spaniels and terriers.

Question 26

In the retrospective study by Martin et al. 2009 of 369 dogs diagnosed with DCM, what are the most commonly recognized breeds to develop the cardiomyopathy?

Answer 26

Doberman Pinschers, Boxers, and Great Danes were the most commonly diagnosed breed, followed by the Cocker Spaniel. Additional commonly affected breeds include Irish wolfhounds, Scottish Deerhounds, and Newfoundlands.

Question 27

What is the gene identified for the development of DCM in Dobermans in the USA?

Answer 27

The PDK-4 gene.

Question 28

What breeds are more commonly affected by Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)?

Answer 28

Boxers and English Bulldogs.

In this disease fibrofatty infiltrates are present predominantly within the right ventricle, but not entirely exclusively, causing myocardial dysfunction and substrate for ventricular arrhythmias.

Question 29

In the United States, what particular mutated proteins have been implicated for the development of ARVC in Boxers?

Answer 29

A desmosomal protein called Striatin. Homozygous dogs are more likely to develop a DCM-phenotype, which chamber dilation and systolic dysfunction (Muers et al 2013) over dogs that are heterozygous carriers.

Additionally, autoantibodies to a protein called Desmoglein-2 were associated with the development of ARVC in humans and dogs.

Question 30

What are some unique features of ARVC in the English Bulldog?

Answer 30

ARVC in the English bulldog seems to be primarily localized to an area of the right ventricular outflow tract, causing aneurysmal dilation of this region on echo. Affected dogs are OLDER and there is a 3:1 MALE-to-female ratio in this breed.

Question 31

In cats, familial HCM has been reported in Sphynx, Bengal, British shorthair, and Norwegian Forest cats, all of which have what similar 3 traits?

Answer 31

(1) autosomal dominant inheritance pattern
(2) age-dependent penetrance
(3) male-sex bias

Question 32

In the Maine coon, what gene mutation encoding for HCM is present on what protein?

Answer 32

A breed-specific mutation in Maine coon cats, the A13P mutation is present on the sarcomere protein, myosin binding protein C3 (MYBPC3).

Question 33

Aside for the genetic mutation, what is the other cause for the predisposition of HCM in the Maine coon?

Answer 33

Maine coons demonstrate a phenomenon called incomplete dominance, where being heterozygous for the mutation seems to cause the disease is a proportion of cats but being homozygous for disease tends to have a worse expression.

Again, males and age-dependent penetrance are modifying factors to the disease.

Question 34

In the Ragdoll, what gene mutation encoding for HCM is present on what protein?

Answer 34

The R820W mutation is present on the sarcomere protein, myosin binding protein C3 (MYBPC3).

Question 35

What additional potential modifier gene present on a non-sarcomeric protein has been implicated in the development of HCM in Ragdolls?

Answer 35

Ragdolls homozygous for a polymorphism of the angiotensin converting-enzyme (ACE) receptor has greater left ventricular wall thickness than cats heterozygous or negative for this polymorphism.

Question 36

What nutritional deficiency has been implicated in the development of DCM in Golden retrievers and Newfoundland dogs?

Answer 36

Taurine.

Question 37

How does taurine deficiency in cats?

Answer 37

Taurine is an essential amino acid that cannot be manufactured from L-methionine like it is in dogs, thereby diets have to be rich in this amino acid.

In recent years, taurine deficient DCM in cats is almost exclusively diagnosed in those fed a non-commercial or home cooked diet.

Question 38

True or False. Mitral valve disease is most commonly diagnosed in large breed dogs.

Answer 38

False.

Question 38

True or False. Arrhythmogenic right ventricular cardiomyopathy is known to be a heritable in boxer.

Answer 38

True.

Question 39

True or False. DCM is commonly diagnosed in Great Danes.

Answer 39

True.

Question 40

Cough receptors located cranial to the carina respond to what kind of stimuli?

Answer 40

Mechanical (mechanoreceptors) and chemical (chemoreceptors) stimuli.

Question 41

Cough receptors located distal to the carina respond to what kind of stimuli?

Answer 41

Chemical (chemoreceptors) stimuli.

Question 42

The Expiratory reflex is defined as a strong expiratory push, often followed by a terminal retching sound. What stimuli (mechanical/chemical/both) activates the expiratory reflex and why?

Answer 42

The expiratory reflex is associated with mechanical stimuli of the more cranial receptors (cranial to the carina) and has evolved to push obstructions forward and out of the respiratory tract.

Question 43

The Deep “True” Cough is defined as a deep inspiration followed by a forced expulsion against a closed glottis which rapidly expels air from the respiratory tract. What stimuli (mechanical/chemical/both) activates the deep cough and why?

Answer 43

The deep cough is associated with chemical stimuli (e.g, smoke, allergens) of the deep cough receptors. This is evolved to clear the respiratory tract of airborne noxious stimuli.

Question 44

Describe the pathophysiology of a cough reflex?

Answer 44

Afferent pathways travel via the vagus nerve to the cough center located within the **medulla oblongata*, which are located adjacent to the centers which regulate normal cardiorespiratory function. This cough center is under high control from nuclei in the upper brain stem and pons. Efferent nerves from the medulla then travel via the vagus, phrenic and spinal motor nerves to the inspiratory and expiratory musculature.

Question 45

Does heart disease, notably left-sided failure, cause coughing?

Answer 45

Short answer: No.

Long answer: When considering the anatomic location of pulmonary edema, first beginning within the interstitial space (perivascular) and eventually extending into the alveolar space, we can see that there are no cough receptors present within that area.

Additionally, edema eventually would have to manage to extend to the first cough receptors located within the lowest bronchi and these receptors ONLY respond to chemical signaling, therefore would NOT respond to the mechanical stimulation for the airway fluid.

Ultimately, for pulmonary edema to produce a cough, the accumulation of fluid would have to be so severe that it would cause to alveoli, bronchioles, lower bronchi to be filled with fluid to the point that it reaches the level of the principle bronchi and trachea for the activation of mechanoreceptors to respond. This would thereby generate an expiratory reflex. In this case, the pulmonary edema would have incredibly severe.

Question 46

In the paper, “Bronchomalacia in Dogs with Myxomatous Mitral valve disease degeneration” by Singh et al 2012, small breed dogs that presented with chronic coughing episodes concluded what findings?

Answer 46

Small breed dogs that presented with a chronic coughing commonly have concurrent airway disease (e.g., both dynamic airway collapse and chronic bronchitis) BUT that left atrial dilatation is NOT the cause of airway collapse in all dogs.

Question 47

In the paper, “Risk factors for Coughing with Naturally Acquired Myxomatous Mitral Valve Disease” by Ferasin et al 2013, dogs with mitral valve disease were reviewed, along with concurrent imaging findings correlating with history, presenting clinical signs and other clinical data. What did they conclude with regards to left atrial enlargement and radiographic findings?

Answer 47

Ferasin and colleagues 2013 were able to conclude that coughing was associated with left atrial dilatation/enlargement and the presence of a radiographic bronchial pattern. This concept supports the idea that BOTH lower airway pathology and atrial enlargement are the processes which activate cough receptors in dogs with MMVD, NOT the presence of pulmonary edema.

Question 48

What are some possible reasons that pulmonary edema may elicit coughing?

Answer 48

Severe mechanisms have be speculated:

1. Changes to air way mucus fluidity (increased water content being carried away via the mucocilliary escalator) causes increased airway inflammation
2. High left atrial pressure can cause bronchial compression, which relieves after treatment.
3. Furosemide has mild bronchodilatory effects alleviating the bronchoconstriction and inflammation associated with airway disease.
4. Sudden increase in cardiac stretch activates pericardial cough receptors

Question 49

What is a normal sleeping respiratory rate?

Answer 49

Some publications suggest a sleeping respiratory rate <30 breaths per minute is considered normal in cats and dogs.

Question 50

How would you classify an abdominal push during expiration?

Answer 50

An abdominal push during expiration is typically indicative of lower airway disease

Question 51

How would you classify an abdominal motion in the opposite direction to the thoracic wall motion

Answer 51

An abdominal motion in the opposite direction to the thoracic wall motion, also known as “paradoxical breathing” indicates respiratory fatigue – where respiratory muscles are tired from the effort of breathing and abdominal muscles have had to be recruited to help ventilate the lungs.

This ultimately suggests that patient is unstable and prone to further deterioration.

Question 52

When we use the term “collapse” in veterinary medicine, various differentials may be implicated in this clinical sign. Can you list some?

Answer 52

1. Syncope
2. Seizure
3. Weakness
4. Ataxia
5. Neuromuscular disorder
6. Refusal to exercise.

Question 53

What pertinent information could be provided to us, as clinicians, that could help classify between the various differentials of collapse? List 2.

Answer 53

1. timeline of the event
2. association with recent events (e.g., exercise, respiratory signs, food intake, etc)

Question 54

Through the concept of neurocardiogenic syncope, when a patient is at rest and is suddenly excited which subsequently results in a collapse, describe the physiologic events that happened:

Answer 54

Whilst at rest (increased parasympathetic tone), the animal has a resting venous return.

Upon stimulation (sympathetic tone), the heart rate increases and there is now excessive ventricular motion which subsequently activates the mechanoreceptors present with the ventricles. As these specific receptors moderate ventricular loading conditions, they act to promote bradycardia and hypotension.

Therefore, from rest with decreased venous return to stimulation of the ventricular mechanoreceptors, ultimately “EMPTY VENTRICLE SYNDROME” occurs promoting bradycardia and hypotension leading to collapse (neurocardiogenic syncope).

Question 55

What are some typical features of syncope, which contrast to a seizure?

Answer 55

1. Association with excitement
2. Absent pre-episodic abnormalities/No preictal phase
3. Collapse with a flaccid posture.
4. A period of unresponsiveness with eyes open or glazed
5. rapid recovery to normal WITHOUT abnormal behavior reported later in that day

Question 56

What are differentials associated with syncope outside of the cardiovascular and/or respiratory systems?

Answer 56

1. reflex-mediated/vaso-vagal
2. Systemic or metabolic conditions, notably insulinomas or pheochromocytomas

Question 57

List history points or clinical findings that are NOT suggestive of cardiovascular disease.

Answer 57

The following are responsible for collapsing episodes that are caused by neurological,, neuromuscular or musculoskeletal disease:

1. Jaw clamping
2. Salivation
3. Nystagmus
4. Pre-episodic abnormalities
5. prolonged recovery
6. Concurrent or persistent behavioral abnormalities
7. Concurrent or persistent gait abnormalities

Question 58

List two useful history points that can distinguish syncopal vs. seizure:

Answer 58

1. Every seizure will follow an almost identical pattern of activity.
2. Epileptiform seizures are often associated with periods of rest or waking up from sleep.

Question 59

What are some useful history points, with regards to identifying exercise intolerance?

Answer 59

1. Duration of exercise or distance covered.
2. Frequency of exercise
3. On lead vs. off-lead exercise
4. Intensity of exercise

Question 60

Where are pure mechanoreceptors-type cough receptors located?

Larynx and nasopharynx
Carina and bronchi
Pericardium and diaphragm
Alveoli and pleural space

Answer 60

Where are pure mechanoreceptors-type cough receptors located?

Larynx and nasopharynx
Carina and bronchi
Pericardium and diaphragm
Alveoli and pleural space

Question 61

A 9-year-old female neutered Cavalier King Charles Spaniel presents with a history of chronic cough and the owner monitored sleeping respiratory rate is 28 breaths per minute. You are aware of a longstanding heart murmur. What differential do you consider likely?

Pulmonary oedema
Chronic bronchitis
Large pleural effusion
Interstitial fibrosis

Answer 61

A 9-year-old female neutered Cavalier King Charles Spaniel presents with a history of chronic cough and the owner monitored sleeping respiratory rate is 28 breaths per minute. You are aware of a longstanding heart murmur. What differential do you consider likely?

Pulmonary oedema
Chronic bronchitis
Large pleural effusion
Interstitial fibrosis

Question 62

A dog presents with episodes of falling over associated with exertion. The owner is uncertain about consciousness during the episode, but describe the following: no pre- or post- event behaviour changes; a duration of 1-2 minutes; and an unusual gait prior to falling. Which group of disorders seems most likely?

Neuromuscular
Cardiovascular
Respiratory
Neurological

Answer 62

A dog presents with episodes of falling over associated with exertion. The owner is uncertain about consciousness during the episode, but describe the following: no pre- or post- event behaviour changes; a duration of 1-2 minutes; and an unusual gait prior to falling. Which group of disorders seems most likely?

Neuromuscular
Cardiovascular
Respiratory
Neurological

Question 63

Describe the usefulness of the hepato-jugular reflex in the physical examination.

Answer 63

one observer looks at the jugular veins whilst another puts pressure on the liver – usually by gently increasing the pressure of palpation on the cranial abdomen. Here, we are effectively pushing blood cranial from the liver and into the thorax. In a normal heart, the blood will be taken into the ventricle and pulmonary circulation without incident, so the volume of blood in the cranial vena cava – and thus the jugular veins – will not increase. So, normal animals experience liver palpation without jugular distension. In an animal where the right heart is failing, there is no capacity to deal with the increase in venous return from the liver – here, the jugular veins distend upon palpation of the abdomen; a positive hepato-jugular reflux.