Myocardial pathology after cardiac venous and lymph flow obstruction in the dog

Abstract

This study, carried out in dogs, was designed to elucidate the effects of cardiac lymphatic and venous obstruction, both separate and combined, on the viability of the myocardium. Specimens were stained with HBFP to demonstrate ischemia. Eleven dogs had venous obstruction, 5 dogs were acute (killed within 24 hours), and 6 dogs were chronic. Sixteen dogs had lymph obstruction, 4 dogs were acute, and 12 dogs were chronic. Twenty dogs had lymph obstruction in addition to venous obstruction, 5 dogs were acute, and 15 dogs were chronic. Nineteen animals served as control animals, 6 dogs were acute, and 13 dogs were chronic. Autopsies excluded all animals with any compromise of the arterial circulation. Large areas of myocardial fibers staining positively with HBFP were seen in acute and chronic experimental dogs from 1 hour to 90 days after operation. No gross or microscopic infarctions were found in the acute or chronic control dogs. Thirty-three per cent of dogs with chronic venous obstruction or chronic lymph obstruction showed gross infarctions without additional microscopic areas of infarction. In dogs with combined venous and lymphatic obstruction, 40 per cent had gross infarctions, whereas 87 per cent had a combination of gross plus microscopically evident infarctions. Thus, interference with the outflow of venous blood and lymph, without interference with the arterial blood supply, can lead to significant myocardial pathology of a type usually associated with a deficit in arterial blood supply. If, as has been postulated, the HBFP stain is specific for ischemic muscle fibers, our results seem to indicate that such a stage of ischemia can persist over a prolonged period of time without progressing to necrosis; or, alternatively, that over the course of time progressively more fibers that are in or near a fibrotic area slowly become ischemic. These findings in dogs provide support for the potential usefulness of myocardial revascularization procedures.