Ultrastructure of Right Ventricular Myocardium Subjected to Acute Pressure Load

Abstract

Background: Ultrastructural data on acute right ventricular pressure load in pigs are rare. Materials and Methods: In control (n = 7) and banding groups (n = 6), right ventricular pressure (micromanometry) and function (sonomicrometry) were measured. Right ventricular pressure was increased 2.5-fold in the banding group by pulmonary artery constriction. Right ventricular biopsies were taken at baseline and after 6 h and processed for electron microscopy. Parameters of cellular injury were determined stereologically. Three perfusion-fixed hearts were investigated qualitatively in each group. Results: Stereology revealed an increase in the sarcoplasmic volume fraction and the cellular edema index in the banding group (p < 0.05). Mitochondrial surface-to-volume ratio and volume fraction did not show significant alterations. Subendocardial edema and small amounts of severely injured myocytes were observed in the perfusion-fixed hearts after banding. Ultrastructure was normal in controls. After an initial increase, the right ventricular work index declined progressively in the banding group but remained unchanged in controls. Conclusions: Ultrastructural alterations resulting from acute right ventricular pressure load were characterized by edema of subendocardial myocytes and single cell necrosis. Focal adrenergic overstimulation and mechanical stress are probably more relevant in the pathogenesis of these lesions than ischemia.

Ultrastructure - myocardium - pulmonary embolism - right heart failure

References

• 1 Machida K, Rapaport E. Left ventricular function in experimental pulmonary embolism.  Jpn Heart J. 1971;  12 221-232
• 2 Zwissler B. Impaired right ventricular function.  Anesthesist. 2000;  49 788-808
• 3 Cuenoud H F, Joris J, Majno G. Ultrastructure of the myocardium after pulmonary embolism.  Am J Pathol. 1978;  92 421-441
• 4 Stringer B MJ, Wynford-Thomas D, Williams E D. Physical randomization of tissue architecture: an alternative of systematic sampling.  J Microsc. 1982;  126 179-182
• 5 Weibel E R. Stereological Methods. Practical Methods for Biological Morphometry. New York; Academic Press 1979
• 6 DiBona D R, Powell W J. Quantitative correlation between cell swelling and necrosis in myocardial ischemia in dogs.  Circ Res. 1980;  47 653-665
• 7 Schaper J, Meiser E, Stämmler G. Ultrastructural morphometric analysis of myocardium from dogs, rats, hamsters, mice and from human hearts.  Circ Res. 1985;  56 377-391
• 8 Schaper J, Hehrlein F, Schlepper M, Thiedemann K-J. Ultrastructural alterations during ischemia and reperfusion in human hearts during cardiac surgery.  J Mol Cell Cardiol. 1977;  9 175-189
• 9 Taylor I M, Shaikh N A, Downar E. Ultrastructural changes of ischemic injury due to coronary artery occlusion in the porcine heart.  J Mol Cell Cardiol. 1984;  16 79-94
• 10 Sage M D, Jennings R B. Myocyte swelling and plasmalemmal integrity during early experimental myocardial ischemia in vivo.  Scanning Microsc. 1988;  2 477-484
• 11 Hayat M A. Principles and Techniques of Electron Microscopy. Biological Applications. 4th ed. Cambridge; Cambridge University Press 2000
• 12 Schmiedl A, Schnabel Ph A, Mall G. et al . The surface-to-volume ratio of mitochondria, a suitable parameter for evaluating mitochondrial swelling.  Virchows Arch [A]. 1990;  416 305-315
• 13 Schmiedl A, Schnabel Ph A, Richter J. Cellular edema and alterations in metabolite content in the ischemic and reperfused canine heart following different forms of cardiac arrest.  Path Res Pract. 1996;  192 1163-1178
• 14 Ohno M, Takemura G, Ohno A. et al . “Apoptotic” myocytes in infarct area in rabbit hearts may be oncotic myocytes with DNA fragmentation.  Circulation. 1998;  98 1422-1430
• 15 Khullar M, Datta B N, Wahi P L, Chakravarti R N. Catecholamine-induced experimental cardiomyopathy - a histopathological, histochemical and ultrastructural study.  Indian Heart J. 1989;  41 307-313
• 16 Jiang J P, Downing S E. Catecholamine cardiomyopathy: review and analysis of pathogenetic mechanisms.  Yale J Biol Med. 1990;  63 581-591
• 17 Yunge L, Bruneval P, Cokay M S. et al . I. Perturbation of the sarcolemmal membrane in isoproterenol-induced myocardial injury of the rat. Permeability and freeze-fracture studies in vivo and in vitro.  Am J Pathol. 1989;  134 171-185
• 18 Stenzl W, Walter G, Rehak P, Metzler H, Tscheliessnig K H, Dacar D. Myocardial changes in acute pulmonary artery embolism - an experimental study.  Fortschr Med. 1984;  102 221-224
• 19 Riedl F, Stenzl W, Tscheliessnig K H, Herman W, Dacar D, Metzler H. Morphologic and functional myocardial changes in experimental pulmonary artery embolism.  Wien Med Wochenschr. 1983;  133 365-366