A new smartphone-based digital stethoscope featuring phonocardiography and electrocardiography in adult horses

Smartphone-based technology is increasingly used in veterinary medicine as a complementary tool for cardiac auscultation and ECG recording. This prospective observational study evaluates a digital stethoscope (DS) that consists of simultaneous phonocardiographic and one-lead ECG recording (dECG) in adult horses, comparing it with auscultation using a conventional stethoscope (CS) and reference base-apex ECG (rECG). A total of 104 horses underwent cardiac auscultation using CSs and DSs to detect arrhythmias and murmurs. Audio and dECG were acquired using the DS. The rECG tracings were also recorded. All ECG tracings were blindly evaluated for interpretability, measurements, and diagnosis. The Shapiro-Wilk test was used to assess the data distribution. Weighted Cohen's κ and Bland Altman plot analysis were applied to verify the agreement between reference vs. smartphone-based methods. Almost perfect agreement was found in detecting murmurs and/or arrhythmias between auscultation with the CS and DS, and between CS auscultation and re-listening to DS audio. Perfect agreement was observed between re-listening to DS audio and DS auscultation and in detecting murmur timing between CS and DS auscultation. Almost perfect agreement was found between rECG and dECG in detecting bradycardia, tachycardia, or normal heart rate (HR) and for P-wave polarity. The lack of variability with both methods for QRS polarity prevented statistical analyses from being performed. Fair agreement was found in the assessment of the presence of artifact. In conclusion, the DS reliably detected heart murmurs and arrhythmias through direct auscultation and re-listening to recordings, and accurately evaluated HR, wave and interval measurements, P-wave and QRS-complex polarities in adult horses.