Echocardiographic Evaluation of Right Ventricular Systolic Function in Dogs with Intracardiac Heartworm Infection

Heartworm disease (HWD) is a common mosquito-borne disease in dogs primarily caused by Dirofilaria immitis. Adult heartworms typically reside in the pulmonary arteries (PA), causing endothelial damage. Echocardiogrphy enables the confirmation of HW, the presence of HW in the PA or right heart, as well as the evaluation the right ventricular (RV) structure and function. A total of 36 dogs visiting Jeonbuk National University Veterinary Medical Teaching Hospital were retrospectively analyzed and divided 3 groups; Group 1 (HW-free, n = 12), Group 2 (HW residing in PA, n = 15), and Group 3 (intracardiac HW, n = 9), based on HW screening tests and echocardiographic examinations. The patients were assessed using RV systolic function indices including fractional area change normalized for body weight (FACn), tricuspid annular plane systolic excursion normalized for body weight (TAPSEn), and systolic myocardial velocity of the lateral tricuspid annulus (RV S’). Analysis of the echocardiographic values, confirmed that FACn and TAPSEn were significantly lower in Group 3 compared to the other groups. The values of RV S’ did not differ significantly between groups. In conclusion, it was confirmed that FACn and TAPSEn are significantly decreased in dogs with intracardiac HW, suggesting that the presence of intracardiac HW alters RV systolic function. Despite several limitations and the relatively small scale, further investigation of these RV systolic function indices, particularly FAC and TAPSE, is warranted in dogs with intracardiac heartworms.