Myocardial fluid balance in dogs with naturally acquired heartworm infection

Randolph H. Stewart Michael E. DeBakey Institute, Texas A&M University, College Station, TX 77843; and the Center for Microvascular and Lymphatic Studies, The University of Texas Medical School, Houston, TX 77030.

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 DVM, PhD
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Karen Uray Michael E. DeBakey Institute, Texas A&M University, College Station, TX 77843; and the Center for Microvascular and Lymphatic Studies, The University of Texas Medical School, Houston, TX 77030.

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Charles S. Cox Michael E. DeBakey Institute, Texas A&M University, College Station, TX 77843; and the Center for Microvascular and Lymphatic Studies, The University of Texas Medical School, Houston, TX 77030.

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Glen A. Laine Michael E. DeBakey Institute, Texas A&M University, College Station, TX 77843; and the Center for Microvascular and Lymphatic Studies, The University of Texas Medical School, Houston, TX 77030.

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DOI:
https://doi.org/10.2460/ajvr.69.3.356
Volume/Issue:
Volume 69: Issue 3
Online Publication Date:
01 Mar 2008
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Abstract

Objective—To determine the effect of naturally acquired heartworm (Dirofilaria immitis) infection on myocardial fluid balance as indicated by myocardial water content and the dynamics of transepicardial fluid flow.

Animals—7 dogs infected with adult heartworms and 8 dogs free of heartworm infection.

Procedures—Infected dogs had heartworms in the right ventricle, pulmonary artery, or both but no evidence of cardiovascular disease on physical examination. A hemispheric capsule was attached to the epicardial surface of all dogs for determination of transepicardial fluid dynamics and permeability of the epicardium to water and protein. Myocardial water content and hydroxyproline content were assessed at necropsy.

Results—Myocardial water content was significantly lower in heartworm-infected dogs. No differences in myocardial hydroxyproline content, transepicardial fluid flow, or epicardial water or protein permeability were detected.

Conclusions and Clinical Relevance—Heartworm infection significantly altered myocardial fluid balance in dogs, possibly because of a change in the myocardial interstitial pressure-volume relationship. These changes may be associated with increased vulnerability to cardiovascular stressors in heartworm-infected dogs.

Abstract

Objective—To determine the effect of naturally acquired heartworm (Dirofilaria immitis) infection on myocardial fluid balance as indicated by myocardial water content and the dynamics of transepicardial fluid flow.

Animals—7 dogs infected with adult heartworms and 8 dogs free of heartworm infection.

Procedures—Infected dogs had heartworms in the right ventricle, pulmonary artery, or both but no evidence of cardiovascular disease on physical examination. A hemispheric capsule was attached to the epicardial surface of all dogs for determination of transepicardial fluid dynamics and permeability of the epicardium to water and protein. Myocardial water content and hydroxyproline content were assessed at necropsy.

Results—Myocardial water content was significantly lower in heartworm-infected dogs. No differences in myocardial hydroxyproline content, transepicardial fluid flow, or epicardial water or protein permeability were detected.

Conclusions and Clinical Relevance—Heartworm infection significantly altered myocardial fluid balance in dogs, possibly because of a change in the myocardial interstitial pressure-volume relationship. These changes may be associated with increased vulnerability to cardiovascular stressors in heartworm-infected dogs.

Contributor Notes

Supported by National Heart, Lung, and Blood Institute grants HL-36115, HL-01999, and HL-077566 and the American Heart Association.

Address correspondence to Dr. Stewart.
Cover American Journal of Veterinary Research
American Journal of Veterinary Research
Publication Date:
01 Mar 2008
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