Case Of the Month

Cyanosis

“Tiny Bubbles” & veterinary medicine from the inside out:
Reverse PDA & Reverse VSD evidenced by a bubble study comprises the July, 2011 SonoPath case of the month. The patient was referred by Penninsula VH & imaging performed by English Bay Ultrasound Service; Doug Casey DVM, DABVP, Vancouver, B.C. Canada. Interpretation & support by Lindquist & Modler of SonoPath.com

Sonogram: Fadara examined at Penninsula VH. Imaging performed by English Bay Ultrasound Service; Doug Casey DVM, DABVP, Vancouver, B.C. Canada.

History: A 6-year-old FS Shiht-Zu Dog presented for exercise intolerance and cyanosis under stress. The clinical exam was otherwise unremarkable. A slight right and left sided murmur was auscultated. Right sided cardiomegaly was noted on radiographs.

Outcome

The patient was referred to a university cardiologist and passed away prior to potentially high risk interventional therapy could be attempted.

Comments

(Modler): Dogs can sometimes have a cyanotic tongue during exercise without having cardiac or circulatory compromise. This can simply be found out by measuring the PCV (is elevated in patients with R-L-shunt). There is a general rule that covers about 90% of exercise intolerance cases with cyanosis: Young cyanotic dogs usually have a cardiocirculatory shunt from R to L Middle aged dogs can have either point 1. Or 3. Old cyanotic dogs usually have pulmonary disease (can also be pulmonary edema) Cyanosis that is noted only on the tongue and occurs during exercise, not causing collapse or breakdown, is most likely not of cardiac origin. Dogs obviously have the possibility to recirculate blood within the tongue thus extracting all the oxygen from the blood. This cyanosis is not noted on the conjunctival membranes or gingival and lasts only during exercise. Note that dogs having a R-L shunt do not always have a noticeable heart murmur! Sometimes it is inconstant and very slight – or – if there is a very large shunt with R-L shunt there is no heart murmur present.

Clinical Differential Diagnosis

(Modler FTA für Kleintiere – Cardiology):

Differentials for heart murmur and cyanosis of cardiac origin are:

VSD with Eisenmenger´s syndrome (R-L shunt)
VSD with bidirectional shunt
PDA with bidirectional shunt
PDA with R-L shunt
VSD combined with pulmonic stenosis
Tetralogy of Fallot
Differentials for heart murmur and cyanosis due to pulmonary disesase are:
Pulmonary pathology causing pulmonary hypertension with tricuspid and concomitant mitral regurgitation (small breed dog)

Sonographic Differential Diagnosis

Right ventricular hypertrophy, reverse PDA/AP window. Small membranous ventricular septal defect with bidirectional flow.

Image Interpretation

(Lindquist DMV, DABVP and Modler FTA für Kleintiere – Cardiology)