Impaired cardiac lymph drainage inevitably causes myocardial edema as demonstrated by an increase in water content.34,85 Histological changes include interstitial edema, swelling of myofibrils, myofibrillar derangement, and mitochondrial injury.14,77,87'89 Additionally, there were described subendocardial and myocardial focal hemorrhages following cardiac lymphatic obstruction.89,90 But these were observed only occasionally and have not been confirmed in other studies.77,91 It is conceivable that the ultrastructural changes following insufficient cardiac lymph drainage reduce myocardial performance.
Chronic interstitial edema is well known to cause interstitial fibrosis.92 Accordingly, the left ventricular myocardial collagen concentration was significantly higher in dogs with chronic myocardial edema in response to pulmonary artery banding (see below) than in normal dogs.34 With prolonged cardiac lymphatic obstruction, thickening of the endocardium with increased elastic and fibrous tissue,90'93'94 subendocardial fibrosis and thickened leaflets of the atrioventricular valves77'91 were observed. These fibrotic changes in consequence of chronically impaired cardiac lymph drainage might also adversely affect cardiac function.
The coronary arteries were also reported to be affected by cardiac lymphatic obstruction.95 Subendothelial edema, interstitial and intracellular edema of the tunica media, degeneration of vascular smooth muscle cells, swelling of the adventitial space, and an increased content of collagen have been observed.95 Furthermore, the development of arterio-venous shunts has been described.95 These observations suggest that an inadequate cardiac lymph drainage contributes to the development and progression of coronary artery disease.
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