Abstract
Equine cardiovascular structures and function are routinely assessed by transthoracic echocardiography. Recently, investigators have described the echocardiographic visualization of equine pulmonary vein ostia. In companion animals, the right pulmonary vein (RPV) to right pulmonary artery (RPA) ratio has been used as an index to estimate the severity of cardiac diseases resulting in left ventricular volume overload. We sought to assess the feasibility of measuring RPV and RPA dimensions, and sought to provide various previously examined RPV and RPA variables in clinically healthy horses that could be used to assess cardiopulmonary disease status. Echocardiographic examination was prospectively performed in 70 healthy horses. The RPV and RPA were visualized using a modified right parasternal long-axis view and maximum and minimum diameters of both vessels were measured from 2D guided M-mode traces. The aortic diameter (Ao) was measured from the right parasternal short-axis view in early diastole. These measurements were then used to produce various ratio indices. RPV and RPA were imaged in all 70 horses. Median of the minimum and maximum RPV/RPA was 0.51 and 0.60, respectively. Median fractional dimensional change of vessels was 33% for RPV and 22% for RPA. The medians of the minimum and maximum RPV/Ao and RPA/Ao were 0.18, 0.28, 0.35 and 0.46, respectively. No relationships between either bodyweight or heart rate and any of the vein or artery variables were identified (maximum r2 = 0.04). Inter- and intra-observer measurement variability was very good for all RPV and RPA measurements. Measuring of RPV and RPA diameters using M-mode transthoracic echocardiography is feasible in healthy horses. Further studies of these variables in horses with cardiac diseases are needed to determine the clinical applicability and utility.
Highlights
Equine cardiovascular structures and function are routinely assessed by transthoracic echocardiography [1,2]; left atrial (LA) and left ventricular diameters can provide useful information in horses with atrial fibrillation, aortic insufficiency and mitral regurgitation [1,2,3].Recently, investigators have described the echocardiographic visualization of equine pulmonary vein ostia [4,5]
Measuring of right pulmonary vein (RPV) and right pulmonary artery ostium (RPA) diameters using M-mode transthoracic echocardiography is feasible in healthy horses
To conserve nomenclature that has been adopted in companion animals, we refer to the third pulmonary venous ostium as the right pulmonary vein (RPV) throughout the remainder of this manuscript, as this ostium receives blood from the largest part of the right lung [4,5], and is analogous to the right pulmonary vein in dogs and cats [6,7,8]
Summary
Equine cardiovascular structures and function are routinely assessed by transthoracic echocardiography [1,2]; left atrial (LA) and left ventricular diameters can provide useful information in horses with atrial fibrillation, aortic insufficiency and mitral regurgitation [1,2,3].Recently, investigators have described the echocardiographic visualization of equine pulmonary vein ostia [4,5]. Investigators have evaluated the right pulmonary vein ostium (RPV) and right pulmonary artery ostium (RPA) in dogs and cats as an echocardiographic index for estimating severity of canine myxomatous mitral valve disease [6,7] and feline cardiomyopathies [8], and for identifying pulmonary hypertension in dogs [9,10]. These studies demonstrated that the RPV/RPA ratio, obtained from a modified right parasternal long axis view, imperfectly discriminated dogs with congestive heart failure from dogs with subclinical mitral valve disease [7,11]. Whether similar vascular ratios would provide additional information in equine cardiac disease remains unknown
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