TRANSITION FROM COMPENSATORY HYPERTROPHY TO DILATED, FAILING LEFT-VENTRICLES IN DAHL SALT-SENSITIVE RATS

To establish an experimental model for studying a specific transitional stage from compensatory hypertrophy to heart failure, we studied the pathophysiology of the left ventricle (LV) in Dahl salt-sensitive (DS) rats fed a high-salt diet. DS rats fed an 8% NaCl diet after the age of 6 wk developed concentric LV hypertrophy at 11 wk, followed by marked LV dilatation at 15-20 wk. During the latter stage, the DS rats showed labored respiration with LV global hypokinesis. All the DS rats died within 1 wk by massive pulmonary congestion. The dissected left ventricles revealed chamber dilatation and a marked increase in mass without myocardial necrosis. In contrast, corresponding Dahl salt-resistant (DR) rats fed the same diet showed neither mortality nor any of these pathological changes. The in vivo LV end-systolic pressure-volume relationship shifted to the right with a less steep slope in the failing DS rats compared with that in age-matched DR rats. Isometric contractions of LV papillary muscles isolated from these DS rats showed reduced tension development in the failing stage, but normal tension development in the hypertrophied stage. In conclusion, the DS rat fed a high-salt diet is a useful model showing rapidly developing congestive heart failure, in which the transition from compensatory hypertrophy to decompensatory dilatation of LV is easily and consistently manifested.