Reduced isotonic sarcomere shortening in rabbit right ventricular pressure overload hypertrophy.

We found previously that sarcomere shortening was reduced in hypertrophied rabbit right ventricular (RV) trabeculae, even when total isometric force and damaged end compliance were the same as normal. Here we studied isotonic shortening of similar preparations force-clamped with a servomotor. A force clamp holds the length of damaged end compliance constant.

Changes in collagen and elastin in rabbit right-ventricular pressure overload.

Collagen content, the ratio of collagen types I and III and elastin content were measured in 5-6- and 10-12-week-old rabbits with and without right-ventricular pressure overload. Significant and equivalent hypertrophy occurred in both age groups. A 2-day pressure overload caused a fall in collagen concentration below control levels in right-ventricular tissue from the older animals, but no change in the younger ones.

Isotonic muscle and sarcomere shortening in rabbit right ventricular preparations.

Cardiac muscle fibers are suspended within and attached to an elaborate connective tissue matrix that includes numerous compliant interconnections. Myocardial muscle fibers are not branched, but connect at small angles to each other to form a branched array. Therefore, fiber shortening occurs as a vector within a connective tissue framework and individual fiber work may exceed external muscle work.

Sarcomere shortening in pressure overload hypertrophy.

Sarcomere shortening during contraction was measured by using laser diffraction, in thin, rabbit right ventricular (RV) trabeculae from normal hearts (N) (n = 5) and from hearts subjected to RV pressure overload by pulmonary banding (H) (n = 5). Banding resulted in substantial RV hypertrophy after 2 wk. Hypertrophied preparations had the same resting muscle length (H = 3.

Increased active elastic stiffness in tetanized papillary muscles from hypertrophied rabbit hearts.

Studies of skeletal muscle suggest that the ratio of stiffness to tension will increase in the presence of a slower rate of crossbridge head rotation from the attached perpendicular state (non-force generating) to the attached 45 degree angle state (force generating). Maximum shortening velocity is depressed proportionate with adenosinetriphosphatase activity in pressure overload cardiac hypertrophy. The maximum rate of isometric force generation also is less than normal but active isometric force levels are normal.

Decreased auxotonic sarcomere shortening in hypertrophied rabbit myocardium.

Auxotonic sarcomere length change occurs during isometric twitches of isolated cardiac muscle preparations. To assess the amount of internal work in hypertrophied myocardium, we measured auxotonic sarcomere length change during isometric tension development over a range of initial muscle and sarcomere lengths. Hypertrophy was produced by banding the pulmonary artery, which resulted in an increase in the ratio of right ventricular free wall weight to total ventricular weight (normal 0.

Myocardial blood flow and mechanics in volume overload-induced left ventricular hypertrophy in dogs.

Chronic volume overload and subsequent left ventricular hypertrophy (LVH) were produced by a surgical shunt between the left subclavian artery and the left atrial appendage in eight dogs. A sham operation was performed on six control dogs. Analysis of biplane ventriculograms showed no significant differences in ejection fraction, mean wall stress, tension-time index, or stress-time index.