Application of an electrocardiography device (iECG) for heart rhythm analysis after exercise in Thoroughbred horses

AliveCor is a smartphone electrocardiography device (iECG) providing automated heart rate (HR) and rhythm determination. Atrial fibrillation (AF) in horses often is paroxysmal and rapid ECG acquisition is needed for diagnostic confirmation. iECGs were collected post-race from 15 horses with AF and 64 horses in sinus rhythm (SR). Results of manual assessment were compared to 3 commercial algorithms for HR and rhythm. Agreement between manually derived HR (HR_M ) and HR derived by the AliveECG Vet (HR_VET ) and Kardia version-1 (K_V1 HR) and Kardia advanced (K_ADV HR) algorithms was quantified by the Bland-Altman limits of agreement test. Agreement between manual rhythm classification and K_V1 and K_ADV algorithms for AF and SR was calculated by the Kappa statistical coefficient. The agreement (bias, 95% limits), between HR_M and HR_VET was 7.1 BPM (-29 to 43) in AF and -4.2 BPM (-38 to 30) in SR, between HR_M and K_V1 HR, was -0.3 BPM (-31 to 30) in AF and 0.2 BPM (-3 to 4) in SR, and between HR_M and K_ADV HR was 7.0 BPM (-29 to 43) in AF and 0.2 BPM (-3.9 to 4.2) in SR. Agreement between manual rhythm classification and K_V1 was 0.36 (0.13-0.59), and K_ADV was 0.84 (0.68-0.99). Sensitivity and specificity for identification of AF and SR of the K_V1 algorithm were 60, 100% and 83, 100%, respectively, and of K_ADV was 87, 100% and 93, 100% respectively. The Kardia algorithms improved precision for HR determination in SR but not AF. The advanced algorithm accurately distinguished between AF and SR. The iECG is suitable for recording episodes of AF following exercise.