[Role of myocardial contractile status and relaxation in ventricular dysfunction during the transition of heart hypertrophy to failure].

Purpose: To investigate the participation of contractile state and relaxation in cardiac muscle dysfunction during the transition from stable hypertrophy to cardiac decompensation in aging spontaneously hypertensive rats (SHR).
Methods: Isolated left ventricular papillary muscle function was studied in SHR with heart failure (SHR-F), in age-matched SHR without evidence of heart failure (SHR-NF), and in nonhypertensive controls Wistar-Kyoto rats (WKY). Muscles were analysed in isometric and isotonic contractions in Krebs-Henseleit solution with calcium concentration of 1.25 mM at 28 degrees C.
Results: Papillary muscles from SHR-F and SHR-NF demonstrated decreased active tension development and shortening velocity relative to normotensive WKY (p < 0.05). SHR-F and SHR-NF did not differ. Compared with SHR-NF and WKY, muscle passive stiffness was increased in the failing SHR (p < 0.05 versus WKY and SHR-NF). This parameter did not differ between SHR-NF and WKY (p > 0.05).
Conclusion: These data suggest that the progression from stable hypertrophy to heart failure is associated with changes in the passive stiffness and is not related to depression of myocardial contractile function.