Pressure-overloaded hypertrophy of the left ventricle (LV) was produced by coarctation of the ascending aorta in 7 dogs. The overall mean weight of the left ventricle (LVW) was 7.86±1.49 (S.D.) g/kg body weight; (normal, 5.99±0.70 g/kg:
p<0.05). After potassium arrest, pressure-volume (
P-V) relationships were examined with the left ventricles isolated from the normals and from the dogs of left ventricular hypertrophy (LVH-dogs). In both groups, the
P-V relationships could be expressed by an equation
ΔV =a-be-cP throughout the range of filling pressure of 2.5 to 35 cmH
2O, where
ΔV was the actual volume change of LV,
P intraventri-cular pressure, and
a, b and
c constants. A sensitive index of LV stiffness, the half-inflation pressure (
h), was defined as In (2
b/a)/c. In hypertrophied hearts, h was 10.5±0.7cmH
2O; (normal, 8.0±0.4 cmH
2O;
p<0.001). The ratio of
LVW to
LVVp=h (the left ventricular volume at
h) in hypertrophy, which was related to the
LV chamber geometry, was 3.1±0.6 in contrast with the normal value of 2.0±0.3. The development of concentric hypertrophy was thus demonstrated. Moreover,
h was closely correlated with
LVW/LVVp=h in both the normals and the LVH-dogs (
r=0.83;
p<0.01). On the other hand, an index of LV wall stiffness
h/LVW/LVVp=h was relatively constant. Therefore, the increase of LV stiffness in the LVH-dogs was attributed to the change in chamber geometry.
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