Diseases of the Heart and Lungs Lecture

Heart chambers

• Right atrium

• Right ventricle

• Left atrium

• Left ventricle

Heart valves

• Tricuspid valve (right atrioventricular valve)

• Pulmonic valve (semilunar valve)

• Mitral valve (left atrioventricular valve)

• Aortic valve (semilunar valve)

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Artery

Brings blood away from the heart

Vein

Brings blood into the heart

Lung pathway of air

1. External nares

2. Nasal cavity

3. Nasopharynx

4. Laryngopharynx

5. Larynx

6. Trachea

7. Bronchi

8. Bronchioles

9. Alveoli

Gas Exchange

• Dependent on pressure gradients

• Blood gas barrier

• Majority of gas exchange occurs at thin portion of barrier

Blood gas barrier

The cells and cell products across which gasses must diffuse between the alveolar and capillary compartments

Majority of gas exchange occurs at thin portion of the barrier:

Type I pneumocyte —> the fused basement membrane of the pneumocyte —> pulmonary capillary endothelium

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Heart disease

Any abnormal condition that damages the heart

• The “cause”

Heart failure

The inability to provide optimal oxygen and nutrient blood supply to the body

• The “result” of heart disease

Degenerative valve disease

• Chronic degeneration of the heart valves leading the valvular insufficiency

• Common signalment: “old small breed dogs”

• All 4 valves can be affected but the mitral valve (left atrioventricular valve) is most commonly affected

Common signalment of Degenerative Valve Disease

• “Old small breed dogs”

• Prevalence and severity increases with age

• King Charles Cavalier Spaniel is overrepresented

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What results from mitral valve insufficiency caused by Degenerative Mitral Valve Disease (DMVD)?

Mitral valve insufficiency results in volume overload of the left atrium, leading to atrial enlargement, pulmonary congestion, and eventually congestive heart failure.

Degenerative Mitral Valve Disease (DMVD) Regurgitation

• Blood abnormally leaks backwards into the left atrium through the abnormal mitral valve during systole (ventricular contraction)

  • Normally during systole, valve closure seals atria closed and blood will ONLY flow out the ventricles into the aorta This condition leads to backflow into the left atrium due to improper valve function, causing stretching and potential heart failure.

Systole remembering

Squeeze out the blood

Heart Enlargement

• Due to increased force needed to push out sufficient blood

• Due to congestion of blood in atria

Congestive heart failure

Due to increased pressure in the left atrium leading to increased pressure in the pulmonary capillaries leading to pulmonary edema

Pulmonary edema

Accumulation of fluid in the lung alveoli due to increased pressure

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DMVD clinical presentation

• No clinical signs

• Murmur on physical exam

• Cough

• Respiratory distress

• Syncope

• Weakness, exercise intolerance, weight loss

Murmur on PE

Left apical systolic murmur

Left apical systolic murmur

a heart sound detected on auscultation, commonly associated with conditions like mitral regurgitation. It typically occurs between the first and second heart sounds.

Cough in DMVD clinical presentation due to

• Airway compression from enlarged left atrium

• Pulmonary edema

• Unrelated tracheal and bronchial collapse

Pulmonary edema

a condition characterized by excess fluid in the lungs, leading to difficulty in breathing and reduced oxygen exchange. It can be caused by heart failure, pneumonia, or exposure to high altitudes.

Unrelated tracheal and bronchial collapse

a condition where the trachea and bronchi collapse due to loss of structural support, potentially leading to airway obstruction and respiratory distress.

DMVD diagnosis

• Chest radiographs

• Echocardiography

• Staging the DMVD

Echocardiography

a diagnostic imaging technique that uses ultrasound to create images of the heart, allowing for evaluation of cardiac function, structure, and blood flow.

DMVD Treatment

• Pimobendan

• Furosemide

Pimobendan

Inodilator - increases contractility of the heart and promotes vasodilation

Fursosemide

Loop diuretic

Loop diuretic

A class of medications that inhibit sodium and chloride reabsorption in the loop of Henle in the kidneys, leading to increased urine production and decreased fluid retention.

Vasodilation

The widening of blood vessels due to the relaxation of vascular smooth muscle, which decreases vascular resistance and increases blood flow.

Most common fline heart disease

Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy common signalment

• 4 months - 15 years

• Inherited in some cta breeds such as main coons

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Hypertrophic Cardiomyopathy can be a secondary disease to

• Hyperthyroidism

• Hypertension

• Myocarditis

• Acromegaly

Hyperthyroidism

a condition where the thyroid gland produces excessive amounts of thyroid hormones, leading to increased metabolism and various systemic effects.

Hypertension

a condition characterized by persistently elevated blood pressure, which can lead to serious health complications such as heart disease and stroke.

Myocarditis

inflammation of the heart muscle, often caused by viral infections, autoimmune diseases, or reactions to medications, which can affect the heart's ability to pump blood.

Acromegaly

a hormonal disorder that results from an excess of growth hormone, usually caused by a benign tumor in the pituitary gland, leading to abnormal growth of bones and tissues.

Primary secondary disease to Hypertrophic Cardiomyopathy

A ventricular muscle disease

Hypertrophy of ventricular muscle leads to:

No dilation and decreased compliance of the ventricle —> insufficient diastole (ventricular filling)

Diastole remembering

Dilated ventricles

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Hypertrophic Cardiomyopathy clinical presentation

• No clinical signs

• Dyspnea and tachypnea

  • Pulmonary edema

• Anorexia and vomiting

• “Saddle Thrombus”

Dyspnea

shortness of breath or difficulty breathing, often associated with conditions like heart failure or lung disease.

Tachypnea

abnormally rapid breathing, typically over 20 breaths per minute, often due to respiratory or cardiovascular issues.

Pulmonary edema

Due to dyspnea and tachypnea

Anorexia in animals

is a decreased appetite or food intake in animals, often indicative of underlying health issues or stress.

“Saddle Thrombus”

• Due to common sequelae of thromboembolism formation at the caudal bifurcation of the aorta

• Very painful and poor prognosis

Signs of “Saddle Thrombus”

Posterior paresis/paralysis, absence of femoral pulses, cyanosis of paw pads, hypothermia

Posterior paresis/paralysis

is a condition characterized by weakness or loss of movement in the hind limbs, typically caused by spinal or nerve injuries.

Femoral pulses

are the palpable pulses felt at the femoral artery in the groin area, indicating blood flow to the hind limbs.

Sequelae of thromboembolism formation

can include tissue ischemia, organ dysfunction, or necrosis due to obstruction of blood flow following an embolic event.

Caudal bifurcation of the aorta

is the point where the abdominal aorta divides into the left and right common iliac arteries, supplying blood to the lower limbs.

Cyanosis of paw pads

is a bluish discoloration of the paw pads due to inadequate oxygenation of the blood, often indicating systemic or local issues affecting circulation or respiratory function.

Hypertrophic Cardiomyopathy Diagnosis

• Chest radiographs

• Echocardiography

Echocardiography

is an ultrasound imaging technique used to assess the structure and function of the heart, including chamber size, wall motion, and valve function.

Hypertrophic Cardiomyopathy treatment

• Furosemide

• Anti-thrombotic

• Pimobendan - off label in cats

Furosemide

is a diuretic medication commonly used to reduce fluid accumulation and manage heart failure by promoting urine production.

Anti-thrombotic

is a medication that helps prevent blood clots by inhibiting platelet aggregation or anticoagulation.

Pimobendan - off label in cats

is a medication used to improve heart function in cats with heart failure. It has inotropic and vasodilatory effects, enhancing cardiac contractility.

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Feline Asthma

Type I hypersensitivity to aerosolized allergens (allergic reaction)

• Reversible bronchoconstriction due to mast cell degranulation

Bronchoconstriction

is the narrowing of the airways in the lungs, often due to inflammation or allergic reactions, leading to difficulties in breathing.

Mast cell degranulation

is the release of histamine and other mediators from mast cells, which plays a critical role in allergic reactions and inflammation, contributing to bronchoconstriction.

Common signalment of Feline Asthma

• Young adult cats

• Siamese cats overrepresented

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Feline Asthma clinical signs

• Cough, expiratory wheeze, tachypnea

• Acute (emergency) or chronic

Tachypnea

Rapid breathing, often seen in respiratory distress. It can indicate a variety of underlying conditions, including asthma.

Chronic medical

conditions that persist over long periods, often requiring ongoing management and treatment to control symptoms and prevent complications.

Feline Asthma Diagnosis

• Clinical presentation + PE findings

• Thoracic radiographs

  • Bronchial pattern

• Airway cytology show eosinophilic inflammation

Airway cytology

is a laboratory technique used to examine cells from the airways, helping to identify inflammatory processes such as eosinophilic inflammation in conditions like asthma.

Eosinophilic inflammation

is an inflammatory response characterized by an increased number of eosinophils, often associated with allergic reactions or asthma.

Feline Asthma Treatment

• Reduce environmental allergens

• Anti-inflammatories

• Albuterol inhalers

Albuterol inhalers as treatment of Feline Asthma

• Only used in asthmatic crisis

  • Long term can cause chronic airway inflammation

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Brachycephalic

Smushed faced animals such as: English or french bulldogs, pugs, Boston terriers, Shih tzus, Persians

Brachycephalic Obstructive Airway Syndrome (BOAS) anatomic abnormalities

• Nasal stenosis

• Hypertrophied nasal turbinates

• Long and thick soft palate

• Macroglossia

• Hypoplastic trachea - narrow

• GI abnormalities

• + acquired abnormalities due to increased negative pressure

Nasal stenosis

Collapsed nasal opening

Hypertrophied nasal turbinates

Enlarged bone structures in the nasal cavity that can obstruct airflow.

Macroglossia

Abnormally large tongue that can obstruct the airway.

Physiological consequences of BOAS

• Decreased anatomical limit of inspiration

• Decreased thermoregulation

• Inability to achieve deep sleep

Inspiration

The process of inhaling air into the lungs, allowing for gas exchange of oxygen and carbon dioxide. It is essential for respiratory function.

Thermoregulation

The process by which the body maintains its core internal temperature within a narrow, safe range despite external temperature variations.

Decreased thermoregulation due to

Inability to move air fast enough when panting

Inability to achieve deep sleep due to

Airway obstruction when pharyngeal muscles relax (sleep apnea)

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Emergency stabilization of upper airway obstruction in brachycephalic

O - Oxygen therapy

S - Sedation

C - Cooling

E - Endotracheal intubation

Endotracheal intubation

A medical procedure in which a tube is inserted into the trachea to maintain an open airway and facilitate breathing, often used in emergencies or during surgery.

Many diff surgical options both temporary and permanent can be elected for BOAS:

Depends on pet, surgeon, and client

Heartworm

• A parasite nematode/roundworm

• Transmitted via mosquito vector to mammalian host

• Larval form gets injected into host —→ turns adult

Heartworm females and mosquitoes

• Adult female heartworms produce microfilaria which will circulate in host

• New mosquitos can become infected by ingesting microfilaria

Microfilaria

• The larval form of heartworms found in the bloodstream of infected animals.

• Essential for the transmission of heartworm disease between hosts.

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Heartworm in Dogs

• Primary insult is damage of pulmonary arteries and lung caused by adult heartworms