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Cardiovascular findings in ponies with equine metabolic syndrome

Natalie HeliczerSwiss Institute of Equine Medicine, Department of Veterinary Clinical Science and Veterinary Physiology, Vetsuisse Faculty, University of Bern and Agroscope, Bern CH-3012, Switzerland.

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Vinzenz GerberSwiss Institute of Equine Medicine, Department of Veterinary Clinical Science and Veterinary Physiology, Vetsuisse Faculty, University of Bern and Agroscope, Bern CH-3012, Switzerland.

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Rupert BruckmaierSwiss Institute of Equine Medicine, Department of Veterinary Clinical Science and Veterinary Physiology, Vetsuisse Faculty, University of Bern and Agroscope, Bern CH-3012, Switzerland.

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Johannes H. van der KolkSwiss Institute of Equine Medicine, Department of Veterinary Clinical Science and Veterinary Physiology, Vetsuisse Faculty, University of Bern and Agroscope, Bern CH-3012, Switzerland.

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Cristobal Navas de SolisSwiss Institute of Equine Medicine, Department of Veterinary Clinical Science and Veterinary Physiology, Vetsuisse Faculty, University of Bern and Agroscope, Bern CH-3012, Switzerland.

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Abstract

OBJECTIVE To determine whether hypertension, high sympathetic tone, resting and exercising arrhythmias, and echocardiographic changes consistent with hypertensive cardiomyopathy were associated with equine metabolic syndrome (EMS) in ponies.

DESIGN Prospective case-control study.

ANIMALS 19 privately owned ponies with a diagnosis of EMS (history of laminitis, body condition score ≥ 7/9, cresty neck score ≥ 3/5, and abnormal oral sugar test result; cases) and 20 healthy control ponies.

PROCEDURES Heart rate (HR), noninvasively measured arterial blood pressure (BP), markers of autonomic tone (splenic volume and HR variability), 24-hour and exercising ECGs, and echocardiograms were compared between cases and controls.

RESULTS Compared with controls, cases had a higher mean ± SD HR (44.5 ± 7.5 beats/min vs 38.6 ± 6.8 beats/min) and median mean left ventricular wall thickness (2.0 cm vs 1.8 cm). No differences were identified between groups in BP, splenic volume, HR variability, and number of premature complexes in ECGs. Mean wall thickness was correlated with BP (r = 0.54), high-frequency power (r = −0.71), and ratio of low-to high-frequency power (φ = 0.66). Relative wall thickness was correlated with serum insulin concentration (r = 0.71).

CONCLUSIONS AND CLINICAL RELEVANCE Ponies with EMS had myocardial hypertrophy that was correlated with insulin response to an oral sugar test, sympathetic and parasympathetic tone, and BP. The heterogeneity and limited sample size of this preliminary study should be considered when drawing conclusions. Cardiovascular changes associated with this syndrome deserve further attention.

Abstract

OBJECTIVE To determine whether hypertension, high sympathetic tone, resting and exercising arrhythmias, and echocardiographic changes consistent with hypertensive cardiomyopathy were associated with equine metabolic syndrome (EMS) in ponies.

DESIGN Prospective case-control study.

ANIMALS 19 privately owned ponies with a diagnosis of EMS (history of laminitis, body condition score ≥ 7/9, cresty neck score ≥ 3/5, and abnormal oral sugar test result; cases) and 20 healthy control ponies.

PROCEDURES Heart rate (HR), noninvasively measured arterial blood pressure (BP), markers of autonomic tone (splenic volume and HR variability), 24-hour and exercising ECGs, and echocardiograms were compared between cases and controls.

RESULTS Compared with controls, cases had a higher mean ± SD HR (44.5 ± 7.5 beats/min vs 38.6 ± 6.8 beats/min) and median mean left ventricular wall thickness (2.0 cm vs 1.8 cm). No differences were identified between groups in BP, splenic volume, HR variability, and number of premature complexes in ECGs. Mean wall thickness was correlated with BP (r = 0.54), high-frequency power (r = −0.71), and ratio of low-to high-frequency power (φ = 0.66). Relative wall thickness was correlated with serum insulin concentration (r = 0.71).

CONCLUSIONS AND CLINICAL RELEVANCE Ponies with EMS had myocardial hypertrophy that was correlated with insulin response to an oral sugar test, sympathetic and parasympathetic tone, and BP. The heterogeneity and limited sample size of this preliminary study should be considered when drawing conclusions. Cardiovascular changes associated with this syndrome deserve further attention.

Contributor Notes

Address correspondence to Dr. Navas de Solis (crisnavasdes@gmail.com).

Dr. Navas de Solis’ present address is Texas Veterinary Medical Center, Texas A&M University, College Station, TX 77843.