Type 1 (small PDA) is characterized by an
asymptomatic left to right shunt with a high
frequency continuous murmur heard only at
the high left heart base. The heart rate and
pulse quality are normal in these dogs and a
precordial thrill is faint or not present at the
left heart base. Radiographs and electrocardiography (ECG) are normal in these dogs,
even at two years. Surgery is recommended,
but not urgent.