Case Studies In Small Animal

Cardiovascular Medicine

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Follow-up Ishihara

Case 33

Heartworm Removal

A: Transesophageal echocardiogram showing worms  B: Flexible alligator forceps in right pulmonary artery


C: Flexible alligator forceps in left pulmonary artery     D: Heartworm extraction via jugular vein


E: Heartworm after extraction                                              F: TEE showing no worms after extraction


G: Eight heartworms - 6 females (in circle) and 2 males (bottom)

For this process, Fisher was anesthetized and transesophageal echocardiography (TEE) was performed. The right branch of the pulmonary artery was always seen best with this device and live heartworms could be visualized (A). The right jugular vein was then exposed via a surgical cutdown. An Ishihara heartworm retrieval forceps was advanced through the right heart while watching the forceps and the cardiac structures using fluoroscopy. The forceps can be seen on the next page ("Ishihara'). They are specially made so that the operator can bend the tip. This facilitates the process of guiding the catheter around the bend in the apex of the right ventricle and out into the main pulmonary artery. From here the catheter was advanced straight forward into the left branch of the pulmonary artery (C) and at other times was bent again to go into the right branch (B). In Fisher's case the forceps catheter was advanced from the jugular vein and ultimately into both branches numerous times. Each time the jaws of the forceps were opened and advanced as far as possible to facilitate worm entrapment. Seven of these excursions resulted in successful worm retrieval for a total of eight worms (D and E). Success probably occurred one in five times. As can be seen in the bottom figure, of the eight worms retrieved, six were larger females and two were smaller males (G). Six heartworms were removed from the right pulmonary artery branch. At the end the forceps were advanced into the right branch 10 times in a row without worm retrieval. Another TEE was performed after this and no heartworms could be visualized (F).

Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.