Assessment of systolic and diastolic function in clinically healthy horses using ambulatory acoustic cardiography.

ABSTRACT

BACKGROUND: Assessment of cardiac electromechanical function in horses requires training, experience and specialised equipment and does not allow continuous monitoring over time. OBJECTIVES: The objective of this study was to establish the use of an acoustic ECG monitor (Audicor® ) in healthy horses. It provides noninvasive, examiner-independent, continuous analyses combining ECG and phonocardiography to calculate indices of cardiac mechanical activity and haemodynamics. Device usability was investigated, reference intervals calculated and reproducibility of analyses assessed. STUDY DESIGN: Prospective descriptive study. METHODS: Continuous overnight recordings were obtained in 123 healthy horses. ECG and acoustic cardiography analyses were performed. Electromechanical activating time (EMAT), rate-corrected EMATc, left ventricular systolic time (LVST), rate-corrected LVSTc and intensity and persistence of the third and fourth heart sound (S3, S4) were reported. Associations with age and reproducibility of analyses were assessed. RESULTS: Audicor® recordings of diagnostic quality were obtained in 116 horses, with an artefact-free recording time of 108-1403 h (mean 1021 h). 44.8% of the horses had atrial premature complexes (up to 0.18% of analysed beats), 4.3% had ventricular premature complexes (up to 0.021% of analysed beats). Reference intervals for acoustic cardiography variables were reported. S3 was significantly more often graded ≥5 (scale 0-10) in younger compared to older horses (P = 0.0036, R2  = 0.072). The between-day coefficient of variation ranged from 2.5 to 7.7% for EMAT, EMATc, LVST and LVSTc. MAIN LIMITATIONS: Audicor® algorithms are based on human databases. Horses were deemed clinically healthy without advanced diagnostics. Some data were lost because of technical difficulties, artefacts and noises. CONCLUSIONS: Overnight Audicor® recordings are feasible in horses. Combining ambulatory ECG and phonocardiography allows noninvasive, continuous assessment of variables representing systolic and diastolic cardiac function. ECG rhythm analyses require over-reading by a specialist, but acoustic cardiography variables are based on automated algorithms independent of examiner input. Further studies are required to establish the clinical value of acoustic cardiography in horses.