Electrocardiographic characteristics of endurance-trained Alaskan sled dogs

Kenneth W. Hinchcliff From the Departments of Veterinary Clinical Sciences (Hinchcliff) and Veterinary Biosciences (Hamlin), College of Veterinary Medicine, and School of Physical Activity and Educational Services, College of Education (Farris), The Ohio State University, Columbus, OH 43210; Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61801 (Constable); and Iditarod Trail Sled Dog Race Committee, Mile 2.2, Knik Rd, Wasilla, AK 99687 (Schmidt).

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Peter D. Constable From the Departments of Veterinary Clinical Sciences (Hinchcliff) and Veterinary Biosciences (Hamlin), College of Veterinary Medicine, and School of Physical Activity and Educational Services, College of Education (Farris), The Ohio State University, Columbus, OH 43210; Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61801 (Constable); and Iditarod Trail Sled Dog Race Committee, Mile 2.2, Knik Rd, Wasilla, AK 99687 (Schmidt).

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James W. Farris From the Departments of Veterinary Clinical Sciences (Hinchcliff) and Veterinary Biosciences (Hamlin), College of Veterinary Medicine, and School of Physical Activity and Educational Services, College of Education (Farris), The Ohio State University, Columbus, OH 43210; Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61801 (Constable); and Iditarod Trail Sled Dog Race Committee, Mile 2.2, Knik Rd, Wasilla, AK 99687 (Schmidt).

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Karin E. Schmidt From the Departments of Veterinary Clinical Sciences (Hinchcliff) and Veterinary Biosciences (Hamlin), College of Veterinary Medicine, and School of Physical Activity and Educational Services, College of Education (Farris), The Ohio State University, Columbus, OH 43210; Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61801 (Constable); and Iditarod Trail Sled Dog Race Committee, Mile 2.2, Knik Rd, Wasilla, AK 99687 (Schmidt).

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Robert L. Hamlin From the Departments of Veterinary Clinical Sciences (Hinchcliff) and Veterinary Biosciences (Hamlin), College of Veterinary Medicine, and School of Physical Activity and Educational Services, College of Education (Farris), The Ohio State University, Columbus, OH 43210; Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61801 (Constable); and Iditarod Trail Sled Dog Race Committee, Mile 2.2, Knik Rd, Wasilla, AK 99687 (Schmidt).

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Objective

To determine electrocardiographic characteristics of endurance-trained Alaskan sled dogs.

Design

Case series.

Animals

319 Alaskan sled dogs entered to compete in the 1994 Iditarod Trail Sled Dog Race.

Procedure

ECG were recorded while dogs were standing and were analyzed digitally.

Results

Amplitudes of P waves (median, 0.40 mV; fifth to 95th percentile range, 0.11 to 0.61 mV) and R waves in lead II (median, 3.02 mV; fifth to 95th percentile range, 1.49 to 4.40 mV) were high; durations of P waves in lead II (median, 61 milliseconds; fifth to 95th percentile range, 36 to 96 milliseconds), QRS complexes (median, 64 milliseconds; fifth to 95th percentile range, 52 to 80 milliseconds), and QT intervals (median, 236 milliseconds; fifth to 95th percentile range, 208 to 277 milliseconds) were prolonged. Median value for mean axis of ventricular depolarization was 57° (fifth to 95th percentile range, 19 to 90°). Atrial and ventricular premature depolarizations were observed in 3 (0.9%) and 4 (1.3%) of 319 dogs, respectively, and paroxysmal ventricular tachycardia was detected in 1 (0.3%).

Clinical Implications

Results suggest that electrocardiographic characteristics of endurance-trained Alaskan sled dogs differ from those reported for nonsled dogs, probably as a result of effects of endurance training on heart size. Some of these characteristics could be mistaken as evidence of pathologic cardiac hypertrophy. (J Am Vet Med Assoc 1997;211:1138–1141)

Objective

To determine electrocardiographic characteristics of endurance-trained Alaskan sled dogs.

Design

Case series.

Animals

319 Alaskan sled dogs entered to compete in the 1994 Iditarod Trail Sled Dog Race.

Procedure

ECG were recorded while dogs were standing and were analyzed digitally.

Results

Amplitudes of P waves (median, 0.40 mV; fifth to 95th percentile range, 0.11 to 0.61 mV) and R waves in lead II (median, 3.02 mV; fifth to 95th percentile range, 1.49 to 4.40 mV) were high; durations of P waves in lead II (median, 61 milliseconds; fifth to 95th percentile range, 36 to 96 milliseconds), QRS complexes (median, 64 milliseconds; fifth to 95th percentile range, 52 to 80 milliseconds), and QT intervals (median, 236 milliseconds; fifth to 95th percentile range, 208 to 277 milliseconds) were prolonged. Median value for mean axis of ventricular depolarization was 57° (fifth to 95th percentile range, 19 to 90°). Atrial and ventricular premature depolarizations were observed in 3 (0.9%) and 4 (1.3%) of 319 dogs, respectively, and paroxysmal ventricular tachycardia was detected in 1 (0.3%).

Clinical Implications

Results suggest that electrocardiographic characteristics of endurance-trained Alaskan sled dogs differ from those reported for nonsled dogs, probably as a result of effects of endurance training on heart size. Some of these characteristics could be mistaken as evidence of pathologic cardiac hypertrophy. (J Am Vet Med Assoc 1997;211:1138–1141)

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