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Supernormal contractility in primary hypertension without left ventricular hypertrophy
G de Simone1, L Di Lorenzo, G Costantino
1Institute of Internal Medicine and Metabolic Diseases, 2nd Medical School, University of Naples, Italy.
Insights
Hypertension may initially enhance heart contractility through a supernormal inotropic state, a compensatory mechanism before left ventricular hypertrophy develops. This adaptation helps maintain systolic function under increased wall stress.
Area of Science:
- Cardiology
- Physiology
- Echocardiography
Background:
- Primary hypertension can lead to left ventricular hypertrophy (LVH).
- Early detection of systolic function changes is crucial for understanding hypertensive heart disease progression.
- Assessing contractility independent of hypertrophy is key to understanding adaptation.
Purpose of the Study:
- To evaluate systolic function and contractility in uncomplicated primary hypertension before compensatory hypertrophy.
- To determine if hypertensive subjects exhibit altered inotropic states compared to normotensive controls.
- To investigate the relationship between early cardiac adaptation and left ventricular mass.
Main Methods:
- Two-dimensional targeted M-mode echocardiography in 43 hypertensive and 54 normotensive subjects.
- Calculation of peak systolic pressure to end-systolic dimension ratio for left ventricular performance.
- Generation of hypertrophy-independent indices of inotropic state using posterior wall thickness or cross-sectional area.
Main Results:
- Hypertensive subjects showed normal fractional shortening despite increased end-systolic stress.
- Systolic pressure/dimension ratio and hypertrophy-independent inotropic indices were elevated in hypertensives.
- A subgroup of hypertensive subjects exhibited a 'supernormal' inotropic state with high contractility and inadequate hypertrophy.
Conclusions:
- A supernormal inotropic state may represent an early adaptive mechanism in hypertension.
- This adaptation helps maintain systolic ventricular performance against elevated wall stress.
- Early contractility changes occur before the development of significant left ventricular hypertrophy.
Abstract:
Forty-three subjects with uncomplicated primary hypertension and without echocardiographic left ventricular hypertrophy and 54 normotensive volunteers were studied by two-dimensional targeted M-mode echocardiography to evaluate systolic function and contractility before the development of compensatory hypertrophy. The ratio of peak systolic pressure to end-systolic dimension was used to assess left ventricular performance and was divided for either posterior wall thickness or cross-sectional area to generate hypertrophy-independent indices of inotropic state. Fractional shortening was normal in the hypertensive group, despite the increase in end-systolic stress. Systolic pressure/dimension ratio was higher in hypertensive subjects (p less than 0.001), as were hypertrophy-independent indices of inotropic state (p less than 0.005), which were inversely correlated to left ventricular mass (p less than 0.001). Values in 11 hypertensive subjects were above the upper confidence limit of the normal shortening/stress relation, which provides a load-independent measure of inotropic state. They showed high hypertrophy-independent indices of inotropic state (p less than 0.01), while the other hypertensive subjects did not. High fractional shortening, wall stress, and systolic pressure (p less than 0.01) were found in the subgroup with supernormal performance, while left ventricular mass was not different from that of other subgroups, depicting inadequate left ventricular hypertrophy. The duration of hypertension was the same in the subgroups. Supernormal inotropic state could be considered one form of primary adaptation to high wall stress that serves to maintain systolic ventricular performance.