Aim: to study changes in the volumes of muscle, fat, and connective tissue in postmortem issue samples (autoptates) from diaphragm, right ventricle, lower limb (gastrocnemius muscle), as well as morphological changes of the diaphragm muscular structure in patients with different functional classes of heart failure (HF), and to compare them with some intravital parameters of external respiration (with maximal inspiratory pressure and its amplitude simultaneously measured by ultrasound method in particular).
Materials and methods: Autoptates of the diaphragm muscle, right ventricle, lower limb (n=39) from 20 men and 19 women (with in vivo diagnosis CHF NYHA functional class (FC) I-IV, hypertension, ischemic heart disease) were examined within 24 hours after the fatal outcome. Light optical microscopy was used to assess the percentages of muscle, connective, adipose tissue, numbers of fibroblasts, and collagen fibers. Spirometric measurements, measurement of respiratory muscles strength, and examination of the diaphragm contractile function were performed by echolocation 56.7±11.9 days before death.
Results: In patients of all NYHA FCs most pronounced changes of volume of muscle tissue were observed in the right ventricle and diaphragm, while less pronounced - in the gastrocnemius muscle. The increase in the volume of adipose tissue in patients with I-III FC CHF was most pronounced in the right ventricle and diaphragm, and less pronounced - in the gastrocnemius muscle. The greatest increase in the adipose tissue volume was recorded in the diaphragm of patients with IV FC. Changes of connective tissue volume did not follow linear dependence. The largest "leap-like" increase in the volume of connective tissue occurred in the diaphragm of patients with III FC, what significantly outstripped this process in peripheral muscles and right ventricular myocardium. There was stable relationship between structure of tissue of the diaphragm, maximal inspiratory thickness of diaphragmatic muscle, and maximal inspiratory pressure. This relation (correlation) was positive for pairs muscle tissue volume - muscle thickness and muscle tissue volume - inspiratory pressure, and negative for pairs connective tissue volume - muscle thickness, connective tissue volume - inspiratory pressure, adipose tissue volume - inspiratory pressure (r>0.85, p<0.01 for all these correlations).
Conclusion: Morphofunctional changes in the diaphragm are caused by progressive decrease in the content of muscle tissue, increases of volumes of adipose and connective tissues. These changes correlate with the CHF FC, maximal inspiratory thickness of diaphragmatic muscle, and maximal inspiratory pressure. Severity of these morphological changes is maximal in patients with FC III CHF.