Resolution of caval syndrome during initial hemodynamic stabilization in dogs with heartworm disease

Abstract

ObjectiveTo report on the spontaneous resolution of caval syndrome in 5 dogs selected for their response to medical stabilization prior to scheduled heartworm extraction.Series summaryFive dogs with heartworm caval syndrome were treated with sildenafil, fluid, and supplemental oxygen therapy. Moreover, 4 of 5 dogs were also administered pimobendan to achieve hemodynamic stabilization in preparation for percutaneous heartworm extraction. Spontaneous heartworm migration back into the pulmonary arteries was detected from 2 h to 5 days after treatment initiation.Unique information providedUnanticipated spontaneous resolution of caval syndrome was documented in a low number of dogs after initiation of a patient stabilization protocol aiming at improving right ventricular hemodynamics and reducing pulmonary artery pressure prior to scheduled heartworm extraction. At this time, it is unknown if intervention to improve the hemodynamic status of the animal prior to heartworm extraction improves procedure outcome, and which factors contributed to the migration of the heartworms back into the pulmonary arteries in these selected cases. Therefore, this approach cannot be recommended in place of current recommendations for treatment of caval syndrome.

Intracardiac heartworms in dogs: Clinical and echocardiographic characteristics in 72 cases (2010‐2019)

“…42,47,48 Migration of worms from the right heart back into the pulmonary arteries occurs after induction of anesthesia for heartworm extraction and with stabilization prior to heartworm extraction, and is associated with the administration of pimobendan and sildenafil. 1,41,49 Nine dogs in our study had intracardiac heartworms at presentation despite receiving phosphodiesterase inhibitors (eg, pimobendan, sildenafil), similar to a previous report. 1 Pimobendan and sildenafil have vasodilatory effects through phosphodiesterase inhibition, while pimobendan also is a positive inotrope able to increase cardiac output.…”

“…Dogs with severe heartworm disease that do not have evidence of hemolysis (including pigmenturia) can have clinical signs attributed to PH and right heart failure. 8,20,41 All dogs with a murmur and ascites in this study had evidence of PH, a finding that has been previously reported. 42 Dogs with intracardiac heartworms with low worm burdens that do not have active hemolysis might benefit from medical therapy as opposed to manual extraction.…”

“…Parasitic embolism contributes to increased pulmonary artery pressures in heartworm disease 42,47,48 . Migration of worms from the right heart back into the pulmonary arteries occurs after induction of anesthesia for heartworm extraction and with stabilization prior to heartworm extraction, and is associated with the administration of pimobendan and sildenafil 1,41,49 . Nine dogs in our study had intracardiac heartworms at presentation despite receiving phosphodiesterase inhibitors (eg, pimobendan, sildenafil), similar to a previous report 1 .…”

“…Dogs with low worm burdens were unlikely to have pigmenturia in our study and in two dogs, intracardiac heartworms were incidentally found during work up of right heart failure and suspected PH. Dogs with severe heartworm disease that do not have evidence of hemolysis (including pigmenturia) can have clinical signs attributed to PH and right heart failure 8,20,41 . All dogs with a murmur and ascites in this study had evidence of PH, a finding that has been previously reported 42 .…”

The wedge sign: A possible lung ultrasound sign for pulmonary thromboembolism

“…LUS and the global FAST a approach including thoracic FAST echocardiography views are most often performed with the patient standing and can be done with minimal distress and handling 32,35–37,41 . Interestingly, the transient and possibly complete resolution of caval syndrome in case 2 has been recently described in dogs being treated with pimobendan and other supportive measures 42 …”