NAVLE Cardiovascular

Feline Congenital Cardiac Abnormalities Study Guide

Congenital heart disease (CHD) in cats is relatively uncommon, with a prevalence of approximately 0.1-0.2% of the feline population and accounting for about 8% of cats diagnosed with heart disease.
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Overview and Clinical Importance

Congenital heart disease (CHD) in cats is relatively uncommon, with a prevalence of approximately 0.1-0.2% of the feline population and accounting for about 8% of cats diagnosed with heart disease. Unlike acquired cardiomyopathies, these defects are present from birth and result from abnormal cardiac development during gestation.

The most common indication of CHD in kittens is detection of a heart murmur at the first vaccination visit. Understanding feline congenital cardiac abnormalities is essential for NAVLE success, as these conditions require accurate diagnosis and appropriate management decisions.

Defect Percentage Shunt Type
Ventricular Septal Defect (VSD) 46-50% L to R (acyanotic)
Tricuspid Valve Dysplasia 9-11% Regurgitation
Pulmonic Stenosis 6-10% Obstruction
Atrial Septal Defect (ASD) 9-10% L to R (acyanotic)
Aortic Stenosis 8-9% Obstruction
Mitral Valve Dysplasia 8-9% Regurgitation
Tetralogy of Fallot 5-6% R to L (cyanotic)
Patent Ductus Arteriosus 3-5% L to R (acyanotic)

Prevalence of Feline Congenital Heart Defects

High-YieldUnlike dogs where PDA is the most common congenital defect, VSD is the most common in cats (46-50%). Remember this species difference for the NAVLE!
Left-to-Right PDA (Typical) Right-to-Left (Reverse) PDA
Often asymptomatic initially Exercise intolerance Stunted growth Respiratory distress (CHF) Continuous or systolic murmur Bounding femoral pulses Precordial thrill (left base) Differential cyanosis (hindlimbs) Exercise intolerance/collapse Hindlimb weakness Polycythemia Soft or absent murmur Split S2 heart sound Normal-sized heart on radiographs

Patent Ductus Arteriosus (PDA)

Embryology and Pathophysiology

The ductus arteriosus is a normal fetal blood vessel derived from the sixth aortic arch that connects the pulmonary artery to the descending aorta. In utero, it allows blood to bypass the non-functioning fetal lungs by shunting blood from the pulmonary artery directly into the systemic circulation.

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