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Abstract

Objective—To determine the feasibility for use of a 6- minute walk test (6-MWT) in dogs with congestive heart failure (CHF) and document that the distance walked in 6 minutes decreases when a dog has CHF.

Animals—16 young mature male hound-crossbred dogs weighing between 25 and 37 kg.

Procedure—An unobstructed path (22.73 m) was measured in a hallway. Each dog was walked on a leash for 6 minutes; each dog was allowed to set its own pace. At the end of 6 minutes (as measured by use of a stopwatch), the total distance walked was measured. Heart rate (HR) obtained by auscultation and mean systemic arterial pressure (MAP) obtained by oscillometry were recorded before and after the 6- MWT. Heart failure was induced by use of rapid ventricular pacing. Mean of the distance walked, HR, and MAP before and after the 6-MWT were compared between the control period and after dogs developed induced CHF.

Results—Dogs with CHF had a significant increase in resting HR, significant decrease in MAP, and a significant decrease in the distance walked in 6 minutes. The MAP increased slightly after exercise during the control period but decreased slightly after exercise during the CHF period. Fractional shortening decreased significantly when dogs had CHF.

Conclusions and Clinical Relevance—Analysis of these results indicated that the distance walked in 6 minutes decreased significantly when a dog had CHF. The 6-MWT requires little time, space, or equipment and may replace the treadmill exercise test. ( Am J Vet Res 2004;65:311–313)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe neuroendocrine responses that develop in dogs subjected to prolonged periods of ventricular pacing.

Animals—14 adult male hound-type dogs.

Procedure—Samples were obtained and neuroendocrine responses measured before (baseline) and after 3 periods of ventricular pacing. A pacemaker was used to induce heart rates of 180, 200, and 220 beats/min (BPM). Each heart rate was maintained for 3 weeks before increasing to the next rate. Atrial natriuretic peptide, antidiuretic hormone, aldosterone, norepinephrine, epinephrine, and dopamine concentrations and plasma renin activity were measured. Severity of left ventricular compromise was estimated.

Results—Shortening fraction decreased significantly with increasing heart rates (mean ± SE, 35.5 ± 1.4, 25.0 ± 1.4, 19.5 ± 1.9, and 12.2 ± 2.3 for baseline, 180 BPM, 200 BPM, and 220 BPM, respectively). Atrial natriuretic peptide concentrations increased significantly at 180 BPM (44.1 ± 3.0 pg/mL) and 200 BPM (54.8 ± 5.5 pg/mL), compared with baseline concentration (36.8 ± 2.6 pg/mL). Dopamine concentration increased significantly at 200 BPM (70.4 ± 10.4 pg/mL), compared with baseline concentration (44.2 ± 7.3 pg/mL). Norepinephrine concentrations increased significantly from baseline concentration (451 ± 46.2 pg/mL) to 678 ± 69.8, 856 ± 99.6, and 1,003 ± 267.6 pg/mL at 180, 200, and 220 BPM, respectively.

Conclusions and Clinical Relevance—Dogs subjected to ventricular pacing for 9 weeks developed neuroendocrine responses similar to those that develop in humans with more chronic heart failure and, except for epinephrine concentrations, similar to those for dogs subjected to ventricular pacing for < 6 weeks. (Am J Vet Res 2002;63:1413–1417)

Full access
in American Journal of Veterinary Research