title: Right Pulmonary Artery Distensibility Index (RPAD Index). A field study of an echocardiographic method to detect early development of pulmonary hypertension and its severity even in the absence of regurgitant jets for Doppler evaluation in heartworm-infected dogs.
abstract: Despite the term "heartworm disease" Dirofilaria immitis infection in dogs should be considered a pulmonary arterial disease that might only involve the right heart structures in its late stage. Chronic infection by adult heartworms in dogs results in proliferative endoarteritis leading to progressively increasing pulmonary artery pressure due to reduced elasticity. Elasticity allows the pulmonary arteries to stretch in response to each pulse and helps maintain a relatively constant pressure in the arteries despite the pulsating nature of the blood flow. Pulmonary artery distensibility for both acute and chronic pulmonary hypertension has been investigated in humans using MRI and has been correlated with the severity of hypertension and its outcome and treatment response. The aim of the present study was to investigate whether echocardiographic measurement of the percentage change in diameter of the right pulmonary artery in systole and diastole (distensibility) may be of value in assessing the presence and severity of pulmonary hypertension in heartworm-infected dogs. The Right Pulmonary Artery Distensibility Index (RPAD Index) (which is calculated as the difference in diameter of the right pulmonary artery in systole and diastole) was calculated in healthy and naturally infected heartworm-positive dogs. The right pulmonary artery was chosen because it is usually affected earlier and to a greater degree. Data were obtained from healthy heartworm-free dogs without any clinical, radiographic, or echocardiographic signs of pulmonary hypertension; naturally infected heartworm-positive dogs in different stages of the disease in which pulmonary pressure could be measured by Doppler echocardiography (using tricuspid and or pulmonary regurgitation velocity and pressure gradient); and naturally infected heartworm-positive dogs in different stages of the disease (with or without tricuspid and or pulmonary regurgitation) in which the pulmonary pressure was measured invasively and noninvasively if possible. Results of these evaluations indicated that RPAD Index is a valuable method for early detection of the presence and severity of pulmonary hypertension in heartworm-infected dogs even in the absence of regurgitant jets for Doppler evaluation and that there is a strong correlation between the RPAD Index and the level of pulmonary hypertension.
authors.affiliation: Veterinary Hospital Città di Pavia, viale Cremona 179, 27100 Pavia, Italy. Electronic address: luigivenco@libero.it.
authors.forename: Luigi
authors.initials: L
authors.lastname: Venco
authors.affiliation: United Veterinary Clinic, Carevec, 9000 Varna, Bulgaria.
authors.forename: Liliya
authors.initials: L
authors.lastname: Mihaylova
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 300 West Drake Road, Fort Collins, CO 80523, USA.
authors.forename: June A
authors.initials: JA
authors.lastname: Boon
mesh_terms: D000818:Animals; D004183:Dirofilaria immitis; D004184:Dirofilariasis / Q000000981:diagnostic imaging*; D004283:Dog Diseases / Q000000981:diagnostic imaging*; D004285:Dogs; D004452:Echocardiography / Q000662:veterinary*; D015150:Echocardiography, Doppler / Q000662:veterinary; D005260:Female; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging / Q000662:veterinary*; D008297:Male; D011897:Random Allocation; D012720:Severity of Illness Index
keywords: Arterial elasticity; Dogs; Echocardiography; Heartworm disease; Pulmonary hypertension