Canine Congenital Heart Abnormalities – NAVLE Study Guide

Overview and Clinical Importance

Congenital heart disease (CHD) refers to structural cardiovascular abnormalities present at birth that result from abnormal embryonic development. In dogs, the prevalence of CHD is estimated at less than 1%, yet these conditions represent a significant portion of cardiac cases seen in puppies and young dogs. Early detection through recognition of heart murmurs during routine puppy examinations is critical, as many of these conditions are correctable with interventional or surgical treatment when identified early.

The five most common congenital heart defects in dogs, in order of prevalence, are: patent ductus arteriosus (PDA), pulmonic stenosis (PS), subaortic stenosis (SAS), ventricular septal defect (VSD), and tetralogy of Fallot (TOF). Regional differences exist in prevalence, with PDA being most common in North America while aortic stenosis may predominate in some European countries.

Embryology and Pathophysiology

Understanding the embryologic development of the heart is essential for comprehending how congenital defects arise. The heart develops from the cardiogenic mesoderm and undergoes complex folding, septation, and remodeling processes. Defects can occur due to genetic factors, environmental influences, infectious agents, toxicological exposure, or nutritional deficiencies during critical developmental windows.