Introduction

• Uncommon congenital heart disease of cats. As compared to dogs, PDA is is significantly less common.
• Fetal communication between aorta and pulmonary artery fails to close at birth.
• Signs: spectrum from asymptomatic murmur to left congestive heart failure, continuous, waxing and waning - 'machinery murmur' (pathognomonic).
• Diagnosis: signs, ultrasonography.
• Treatment: surgical correction before symptomatic.
• Prognosis: good if corrected, guarded without surgery.

Pathogenesis

Etiology

• Failure of normal ductal muscle development which prevents physiologic or functional closure at birth.

Pathophysiology

• The ductus arteriosus, a normal fetal vessel, fails to close in the first hours or days after birth    →    conduit between the descending aorta and the pulmonary trunk.

Typical

• Pulmonary vascular resistance much lower than systemic vascular resistance so:
  • Left to right shunt (aorta to pulmonary artery)    →     increased flow through pulmonary vasculature    →     increased return to left heart    →     volume overload of left heart    →     chronic left-sided CHF.
  • Dilation and eccentric hypertrophy of left atrium/ventricle can result in mitral regurgitation (MR) due to stretching of the mitral annulus.

Rare

• Right-to-left shunt.
• Pulmonary hypertension    →   due to retention of fetal type pulmonary vasculature and/or massive pulmonary overcirculation with a left-right shunt resulting in reactive hypertension (a left-to-right shunt typical of PDA)    →   pulmonary overcirculation    →   pulmonary hypertension (as Eisenmenger's physiology)    →    right-left shunt.

Diagnosis

Treatment

Prevention

Outcomes