Effect of N‐Butylscopolammonium Bromide and Metamizol Sodium on Heart Rate, Blood Pressure, and Echocardiographic Measurements in Warmblood Horses With Aortic and Mitral Valve Regurgitation

ABSTRACT Background Administration of N‐butylscopolammonium bromide (NBB) with metamizol sodium (NBBM) causes tachycardia and hypertension, and has been associated with accentuated cardiac murmurs. Objectives To evaluate the effect of a pharmacological challenge using NBBM on valvular regurgitation and cardiac murmurs in horses with aortic (AR) and mitral valve regurgitation (MR). Animals Twenty Warmblood horses with AR and 20 with MR. Methods Cardiac auscultation and two‐dimensional (2D), M‐mode, color flow, pulsed wave Doppler flow, and tissue Doppler echocardiography were performed with simultaneous ECG recording and non‐invasive blood pressure measurements during rest and pharmacological challenge using 0.2 mg/kg NBB and 25 mg/kg metamizol sodium. Cardiac dimensions and functional parameters were assessed. Regurgitant jet size was subjectively evaluated, and jet area was measured. Data at rest and during pharmacological challenge were compared using repeated measures analysis or related samples Wilcoxon signed rank test. p‐values were adjusted using the Benjamini‐Hochberg method. Results Compared with rest, pharmacological challenge resulted in decreased atrial and ventricular dimensions and increased aortic and pulmonary dimensions (PBHa ≤ 0.02). Left ventricular end‐diastolic diameter decreased in horses with AR (PBHa < 0.02) but not in horses with MR. Pharmacological challenge resulted in increased median cardiac murmur intensity (PBHa = 0.03 and PBHa < 0.02) and jet area (PBHa ≤ 0.02 and PBHa = 0.03) in horses with AR and MR, respectively. Conclusions and Clinical Importance Pharmacological challenge with NBBM affects cardiac chamber sizes, regurgitant jet, and cardiac murmur intensity in horses with AR and MR. Influences on heart rate and blood pressure should be considered during longitudinal follow‐up examinations.