Stretching cardiac tissue may cause deterioration of electrophysiologic properties. To quantitate changes, false tendons (FT) and thin papillary muscles or ventricular trabeculae (VM) were isolated in tissue bath (36°C), and resting length (L) was progressively increased. Resting tension (RT), measured after stress relaxation and corrected for cross sectional area, was plotted against changes in L to determine the L-RT relationships. At each increment of L, the tissue was stimulated at 60/min., and transmembrane action potentials (TMP) analyzed. Data averaged from 30 FTs and 24 VMs demonstrated that FTs were more compliant, requiring a greater increase in L to reach a given RT than did VMs. For both VM and FT, RTs less than 2 gm/mm2 had no influence on TMPs, independent of the L increase. When RT was raised to 2 to 4 gm/mm2, electrical properties changed in most preparations, but reversed within 60 min. At RTs between 4 and 25 gm/mm2, electrical changes became irreversible. RT as an independent variable was the major determinant influencing electrical changes. Thus, the difference in compliance between canine FT and VM results in FTs having a greater resistance to the adverse electrical effects of a measured amount of stretch.
|Original language||English (US)|
|Pages (from-to)||No. 974|
|State||Published - Jan 1 1975|
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