Retrospective Evaluation of Synchronous Diaphragmatic Flutter in Horses: 37 Cases (2004-2022)

To describe the clinical presentation of horses with synchronous diaphragmatic flutter (SDF) and identify clinical and laboratory variables associated with survival.

Retrospective study from January 2004 to September 2022.

Five large animal referral hospitals in the United States.

Thirty-seven horses of various breeds and ages presenting with clinical signs of SDF, excluding animals participating in an endurance competition. All horses were >1 year of age.

None.

Variables recorded and analyzed included signalment, clinical and laboratory data, treatments, and outcome. SDF was seen with gastrointestinal disease in 35% (13/37) of horses. The survival for horses with SDF was 78.4% (29/37). Nonsurvivors had a higher heart rate (78 ± 15/min) than survivors (58 ± 17/min; p = 0.01). Nonsurviving horses were more likely than surviving horses to have had nasogastric reflux (odds ratio: 16.8; 95% confidence interval: 1.9-222.8). Compared with survivors, nonsurvivors had a lower sodium concentration (131 ± 7 mmol/L [131 ± 7 mEq/L]) and bicarbonate concentration (22.7 ± 2.8 mmol/L [22.7 ± 2.8 mEq/L]). Nonsurvivors had higher lactate concentration (7.1 ± 3.9 mmol/L [64 ± 35.1 mg/dL]), glucose concentration (20 [13.3-29] mmol/L; 378 [239-522] mg/dL), and gamma-glutamyltransferase activity (51 [27-687] U/L). In horses that had ionized calcium concentration measured, 13 of 18 (72%) had a concentration <1.3 mmol/L (5.2 mg/dL).

SDF in horses is seen concurrently with gastrointestinal and other diseases, and not all horses present with hypocalcemia. The survival for nonendurance horses with SDF was 78%. Nonsurvival was associated with increased heart rate, the presence of nasogastric reflux, and a variety of laboratory abnormalities.