Pulmonary Hypertension (PH) in Dogs (NAVLE Notes)
Pulmonary hypertension (PH) is a condition characterized by elevated pulmonary artery pressure, often secondary to other diseases. It frequently leads to exercise intolerance and respiratory distress in middle-aged to older dogs.
Classic Case
- Typical Signs:
- Respiratory: Cough, respiratory distress, syncope.
- Cardiovascular: Exercise intolerance, lethargy, and ascites.
- Auscultation:
- Normal or with variable murmurs (mitral or tricuspid valve).
- Split second heart sounds.
- Pulmonary crackles on lung auscultation.
Diagnosis
- Possible Etiologies:
- Mitral Valve Regurgitation: Chronic increased left heart pressures.
- Chronic Hypoxia: Secondary to right-to-left shunts or chronic respiratory disease.
- Heartworm Disease: Can directly increase pulmonary pressures.
- Thoracic Radiography:
- Cardiomegaly.
- Pulmonary artery dilation, tortuous pulmonary arteries.
- Dilated caudal vena cava.
- Pulmonary patterns that may be interstitial, alveolar, or bronchiolar.
- Echocardiography:
- Right ventricular hypertrophy.
- High-velocity tricuspid valve regurgitation.
- Flattened interventricular septum or paradoxical septal motion (indicates high right heart pressures).
- Varying degrees of right atrial and ventricular dilation.
Treatment
- Treat Underlying Disease: Primary focus if identifiable.
- Oxygen Therapy: For acute decompensation.
- Medications:
- Pimobendan: Inodilator, helpful for PH secondary to heart disease.
- Sildenafil: Phosphodiesterase inhibitor, reduces pulmonary artery pressure.
Key Points
- Prognosis:
- Guarded to poor, depending on the treatability of the underlying cause and response to specific PH therapy.
- Response to Therapy:
- Pimobendan and sildenafil may improve clinical signs, but prognosis remains limited if the underlying cause persists.
NAVLE-Style Practice Questions on Pulmonary Hypertension
Question 1
A 10-year-old mixed-breed dog presents with a chronic cough, exercise intolerance, and occasional syncope. Radiographs reveal right heart enlargement and pulmonary artery dilation. Echocardiography shows right ventricular hypertrophy and high-velocity tricuspid valve regurgitation. What is the most likely diagnosis?
- A) Mitral valve disease
- B) Pulmonary hypertension
- C) Left-sided heart failure
- D) Dilated cardiomyopathy
Correct Answer: B
Explanation: The signs and echocardiographic findings of right heart enlargement, pulmonary artery dilation, right ventricular hypertrophy, and tricuspid valve regurgitation are indicative of pulmonary hypertension.
Question 2
A middle-aged Labrador is diagnosed with pulmonary hypertension. Which medication would be recommended to help lower pulmonary artery pressure?
- A) Furosemide
- B) Pimobendan
- C) Atenolol
- D) Enalapril
Correct Answer: B
Explanation: Pimobendan, an inodilator, is used to reduce pulmonary artery pressure in cases of pulmonary hypertension. Furosemide and enalapril target fluid overload and afterload, respectively, and atenolol is primarily a beta-blocker.
Question 3
An older dog with a history of chronic respiratory disease is diagnosed with secondary pulmonary hypertension. Which of the following is the most likely finding on thoracic radiography?
- A) Normal pulmonary vasculature
- B) Enlarged pulmonary arteries
- C) Mitral valve prolapse
- D) Left atrial dilation
Correct Answer: B
Explanation: Chronic respiratory disease can lead to pulmonary hypertension, characterized by enlarged pulmonary arteries. Left atrial dilation and mitral valve prolapse are not directly associated with pulmonary hypertension secondary to respiratory disease.
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