Type 3 (large PDA) is subdivided into those with (3a) and without (3b) congestive heart failure (CHF). Dogs with Type 3a usu- ally have a reduced exercise capacity, a coarse continuous murmur and thrill over the left thorax, a systolic murmur of mitral regurgitation, bounding pulse due to wide pulse pressure, marked left heart enlarge- ment by six months ofage, a medium to large ductal aneurysm, a significant increase in pUlmonary vascular markings and ECG lead II R waves possibly exceeding 5mV. Surgery is recommended immediately in these cases. Type 3b is characterized by the above signs plus those ofCHF including dyspnea caused by pulmonary edema, cachexia, and possible atrial fibrillation or other arrhythmias. The
pulmonary edema must be resolved as much as possible before surgery is performed. This is accomplished by cage rest, furosemide, supplemental oxygen, an angiotensin con- verting enzyme inhibitor and digitalization