Spectral Doppler of aortic and carotid blood flow in horses with aortic valve regurgitation.

Abstract

OBJECTIVES: This study aimed to compare two-dimensional, M-mode, color, pulsed-wave Doppler (PWD) and continuous-wave Doppler (CWD) echocardiography, and PWD ultrasonography of the caudal common carotid artery (CCA) in horses with aortic regurgitation (AR). ANIMALS: Warmblood horses without (n&#xa0;=&#xa0;20) and with mild, moderate, and severe AR (n&#xa0;=&#xa0;60) were included in the study. MATERIALS AND METHODS: A retrospective descriptive study focused on cardiac dimensions, aortic and CCA Doppler flow. Non-invasive blood pressure and presence of ventricular arrhythmia were recorded. Groups were compared using analysis of variance, chi-square, Spearman's rho, and Kruskal-Wallis tests. RESULTS: Maximal aortic antegrade flow velocity was higher in horses with moderate and severe AR than in normal horses and higher in those with severe AR than in those with mild AR (P<0.001). Mean (standard deviation) antegrade CCA flow velocities were 0.9 m/s (0.3 m/s) in normal horses and 1.0 m/s (0.2 m/s), 1.2&#xa0;m/s (0.3 m/s), and 1.5 m/s (0.4 m/s) in horses with mild, moderate, and severe AR, respectively. Retrograde mid-to-end diastolic PWD ultrasonography of the common carotid artery (PWD-CCA) flow occurred in horses with moderate (6/20) and severe (13/20) AR. The presence of pathologic retrograde PWD-CCA flow was associated with presence of increased left ventricular dimensions and pulse pressures >60&#xa0;mmHg. The CWD regurgitant jet pressure half-time failed to differentiate between AR severity grades. STUDY LIMITATIONS: The limitations of this study included retrospective design with missing values, AR classification system not validated by longitudinal follow-up, and CCA retrograde velocities <10&#xa0;cm/s not measured. CONCLUSIONS: Pulsed-wave Doppler ultrasonography of the common carotid artery identifies moderate and severe AR in horses with hemodynamic overload. Presence of retrograde PWD-CCA flow was associated with moderate and severe AR and with left ventricular dilation. Quantification of CWD pressure half-time appeared unreliable for AR severity assessment.