Computed Tomographic Measurement of the Main Pulmonary Artery to Aortic Diameter Ratio in Healthy Dogs: A Comparison to Echocardiographically Derived Ratios

Abstract

Indicators of pulmonary hypertension in dogs examined with thoracic computed tomography (CT) are not well established in the veterinary literature. In humans, the main pulmonary artery to aortic diameter ratio (MPA:Ao) measured via CT, has been shown to be more sensitive than echocardiographic variables for predicting presence and severity of pulmonary hypertension, in some cases. In veterinary literature, the MPA:Ao has been determined echocardiographically to have an upper limit of about 1:1. Measurement of this ratio has not been described in dogs using CT. The objectives of this cross-sectional, prospective study were to compare echocardiographic measurement of MPA:Ao with that obtained via CT, determine if measurement of MPA:Ao via CT is repeatable and reproducible, and determine the effect of respiration and contrast administration on the measurement of MPA:Ao via CT. Ten healthy dogs without pulmonary hypertension were anesthetized to undergo thoracic CT using three protocols and echocardiography. The MPA:Ao was measured three times by three observers for each of the three CT protocols and compared to echocardiographic measurements. The mean MPA:Ao measured among all observers and CT protocols was 1.108 ± 0.152 (SD). The effect of CT scan protocol on MPA:Ao significantly differed among the three methods (P = 0.0014), where expiratory scans had lower MPA:Ao than inspiratory scans. The ratio measured on inspiratory CT scans consistently overestimated MPA:Ao when compared to echocardiography (bias = 0.226). Findings did not support the echocardiographically derived upper limit of MPA:Ao as an upper limit for determination of main pulmonary arterial enlargement on CT.

Joint virtual issue on recent advances in veterinary cardiac imaging

“…Computed tomography in particular has been used for a detailed global assessment of thoracic structures beyond the heart, to determine secondary cardiac effects from thoracic changes, and to evaluate sequelae to cardiac disease and extracardiac vascular anomalies, allowing for accurate diagnosis and treatment planning . In contrast, MRI is currently predominantly used for cardiovascular assessment .…”

“…28 Although ECG gating is routinely used in human patients for evaluation of the coronary arteries, the use of computed tomographic angiography for depiction of the coronary arteries in Bulldogs has been demonstrated without ECG gating, 30 making the technique available to a wider community because not all scanners are able to be equipped with ECG gating and the installation of the necessary softand hardware can be cost prohibitive.Computed tomography in particular has been used for a detailed global assessment of thoracic structures beyond the heart, to determine secondary cardiac effects from thoracic changes, and to evaluate sequelae to cardiac disease and extracardiac vascular anomalies, allowing for accurate diagnosis and treatment planning. [24][25][26]31 In contrast, MRI is currently predominantly used for cardiovascular assessment. 32 Advanced image postprocessing and analysis software that allows generation of subjective numeric parameters for cardiac as well as pulmonary vascular assessment has found initial use in veterinary applications.…”

“…Computed tomography in particular has been used for a detailed global assessment of thoracic structures beyond the heart, to determine secondary cardiac effects from thoracic changes, and to evaluate sequelae to cardiac disease and extracardiac vascular anomalies, allowing for accurate diagnosis and treatment planning. [24][25][26]31 In contrast, MRI is currently predominantly used for cardiovascular assessment. 32 Advanced image postprocessing and analysis software that allows generation of subjective numeric parameters for cardiac as well as pulmonary vascular assessment has found initial use in veterinary applications.…”

Joint virtual issue on recent advances in veterinary cardiac imaging

“…Computed tomography in particular has been used for a detailed global assessment of thoracic structures beyond the heart, to determine secondary cardiac effects from thoracic changes, and to evaluate sequelae to cardiac disease and extracardiac vascular anomalies, allowing for accurate diagnosis and treatment planning. [24][25][26]31 In contrast, MRI is currently predominantly used for cardiovascular assessment. 32 Advanced image postprocessing and analysis software that allows generation of subjective numeric parameters for cardiac as well as pulmonary vascular assessment has found initial use in veterinary applications.…”

“…The effect of different drug protocols may alter the functional or anatomical variables determined from CT and MRI examinations and has therefore been the subject of several publications [21][22][23]. Similarly, cross-modality correlation and the need for establishment of reference values has prompted several publications,[23][24][25][26] including the first cross sectional study published in VRU in 2005 by MacDonald et al using MRI to quality left ventricular mass compared to echocardiography in cats. 27 Exact timing of the image acquisition in relation to the contrast medium highlighting the vascular bed of interest for angiography studies generally requires a power injector; specific bolus tracking software allows patient specific timing of the image acquisition that has been addressed in a review article.…”