Direct HR: 100 bpm
Heart rhythm: Regular
Intensity of heart sound: Normal, obscured by continuous heart murmur, grade V/VI
Extra sounds – clicks or gallops: None
Precordial palpation: A palpable thrill is present at the left cranial thorax.

The CEG considers the following differential diagnosis as most likely (and why): The most likely differential based on the history and physical examination is a patent ductus arteriosus (PDA). A murmur grade V out of VI is almost certainly not functional and a structural defect is likely. Subvalvar aortic stenosis and pulmonary valve stenosis both result in a systolic heart murmur at the left heart base; pulmonary valve stenosis is typically associated with a normal arterial pulse, while subvalvar aortic stenosis commonly causes a weak, or hypokinetic arterial pulse. However, if the aortic stenosis is associated with concurrent aortic insufficiency pulse quality may be increased. Ventricular septal defect usually results in a loud systolic murmur on the right thorax. However, a diastolic murmur may also be apparent if the aortic root prolapses into the defect and causes moderate or severe aortic valve insufficiency. The most likely cause of both the continuous heart murmur and an increased arterial pulse is PDA.

The CEG considers the following diagnostic tests as the highest priority:In an asymptomatic dog with probable congenital heart disease, the best confirmatory test will be an echocardiogram including Doppler studies. Prior to an echocardiogram, thoracic radiographs are reasonable to provide supportive evidence of the likely defect and to evaluate for the presence/absence of congestive heart failure. If an arrhythmia is auscultated, an electrocardiogram is also indicated. However, neither thoracic radiographs nor electrocardiography are specific for congenital heart disease. Bloodwork is reasonable to evaluate general health, but is not useful to reach a diagnosis. Although not well studied in puppies, NT-proBNP is likely to be elevated if cardiac enlargement is present but, again, is not specific for a given condition. A blood pressure measurement is not required for diagnosis, but may provide valuable information regarding general cardiovascular status.

RADIOGRAPHIC INTERPRETATION Findings: Three views of the thorax are available for interpretation.  The trachea is deviated dorsally toward the spine and there is prominence of the cardiac silhouette at the 4 to 6 o’clock position on the ventrodorsal view consistent with left ventricular enlargement.  There is a bulge at the caudodorsal border of the cardiac silhouette consistent with left atrial enlargement.  The aortic arch appears dilated.  The pulmonary veins and pulmonary arteries are mildly dilated, most evident to the caudal lung fields on the ventrodorsal view.  There is reduced abdominal serosal detail compatible with age or abdominal effusion. Conclusions:   Left-sided cardiomegaly with dilation of pulmonary arteries and veins. Compatible with left-to-right shunting congenital heart defect.  No evidence of congestive heart failure.

THE CEG RECOMMENDS:
Nora underwent femoral arterial catheterization and interventional occlusion of her patent arterial duct (PDA). Briefly, the right femoral artery was catheterized and fluoroscopy was used to guide a Canine Duct Occluder (nickel-titanium device) into the PDA. Angiography confirmed complete closure and Nora was discharged the next day with resolution of her heart murmur and no flow through PDA apparent on repeat echocardiography. Surgical ligation would also have been appropriate; the decision to pursue surgery or catheter-based occlusion relates to operator preference and local options/success rates. Based on a study of 520 dogs with PDA (Saunders, 2014), dogs that did not undergo closure of the duct had a 17 times greater risk of death compared to those that underwent closure. Those that did have closure of their PDA generally had an excellent outcome, though those with concurrent congenital heart disease or clinical signs before closure had worse outcomes.

1. Saunders AB, Gordon SG, Boggess MM, Miller MW. Long-term outcome in dogs with patent ductus arteriosus: 520 cases (1994-2009). J Vet Intern Med. 2014 Mar-Apr;28(2):401-10.