Pulmonary Arterial Hypertension (PHT)

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Sections available in full article Introduction, Presenting signs, Acute presentation, Geographic incidence, Age predisposition, Pathogenesis, Etiology, Predisposing factors, Pathophysiology, Timecourse (incubation, duration), Diagnosis, Presenting problems, Client history, Clinical signs, Diagnostic investigation, Confirmation of diagnosis, Gross autopsy findings, Histopathology findings, Differential diagnosis, Treatment, Initial symptomatic treatment, Monitoring, Subsequent management, Sequelae, Prognosis, Reasons for treatment failure, Sources, Publications, Vetstream contributor(s),
Contributors Dr Mark Oyama DVM DACVIM-Cardiology

Introduction

  • PHT is typically defined as an elevated mean pulmonary artery pressure above 25mmHg (normal=10-15mmHg), and is the result of:
    • Increased pulmonary vascular resistance.
    • Increased pulmonary blood flow.
    • Increased left atrial pressure.
    • Or any combination of the three.
  • Severe PHT can cause right heart failure, tachypnea, exercise intolerance, and syncope.
  • PHT is usually secondary to other disease conditions such as pulmonary thromboembolism Lung: pulmonary thromboembolism , heartworm infestation Canine cardiopulmonary dirofilariasis , chronic respiratory disease, or left-sided heart failure.
  • Treatment of PHT involves addressing the primary cause, supplemental oxygen, and vasodilator therapy.
  • Treatment of severe disease is often unrewarding.

Diagnosis

Clinical signs

  • Dyspnea, tachypnea, harsh lung sounds, inspiratory wheezes, crackles, and snaps, split second heart sound, murmur of tricuspid regurgitation (right apical systolic).
  • Ascites, pleural effusion, jugular pulses, S3 gallop sound.

Diagnosis

Differential diagnosis

  • Respiratory signs due to primary pulmonary disease but without PHT.
  • Right heart failure due to degenerative tricuspid valve disease or pulmonic stenosis.

Sequelae

Prognosis

  • The prognosis in cases of severe PHT with right heart failure is very poor.
  • Most cases at the author's institution die within 4-6 months.
  • Mild or moderate PHT may be successfully managed depending on the underlying cause.

Reasons for treatment failure

  • Refractory signs of right heart failure or weakness, disability from underlying disease process.

Sources

Publications

Refereed papers

  • Johnson L, Boon J & Orton EC (1999) Clinical characteristics of 53 dogs with Doppler-derived evidence of pulmonary hypertension: 1992-1996. J Vet Intern Med 13 (5), 440-447.PubMed
  • Sottiaux J & Franck M (1999) Pulmonary embolism and cor pulmonale in a cat. J Small Anim Pract 40 (2), 88-91.PubMed
  • Gavaghan B J, Lapointe J M & Thomas W P (1998) Acute onset of pulmonary necrotizing arteritis in a dogs with a left to right patent ductus arteriosus. Aust Vet J 76 (12), 786-791.PubMed
  • Glaus T M, Hauser K & Hassig M et al(2003) Non-invasive measurement of the cardiovascular effects of chronic hypoxemia on dogs living at moderately high altitude. Vet Rec 152 (26), 800-803.PubMed
  • Mikhail G W & Prasad S K et al(2004) Clinical and hemodynamic effects of sildenafil in pulmonary hypertension: acute and mid-term effects. Eur Heart J 25 (5), 431-436.PubMed
  • Rawlings C A (1978) Pulmonary vascular response of dogs with heartworm disease. Can J Comp Med 42 (4), 452-459.PubMed
  • Rich S & McLaughlin V V (2003) Endothelin receptor blockers in cardiovascular disease. Circ 108 (18), 2184-2190.PubMed

Other sources of information

  • Johnson LR, Hamlin RL. Recognition and treatment of pulmonary hypertension. In: Current Veterinary Therapy XII: Small Animal Practice. WB Saunders, Philadephia. 1995;887-892.
  • Kittleson MD and Kienle RD. Small Animal Cardiovascular Medicine. 1998. Mosby, St. Louis.
  • Fox PR, Sisson DD, Moise NS, eds. Textbook of Canine and Feline Cardiology , 2nd ed. 1999. WB Saunders, Philadelphia.

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