Related Experiment Videos
Mechanical and non-mechanical factors in hypertensive hypertrophy, their clinical roles
Y Sugishita1, K Iida, K Yukisada
1Department of Internal Medicine, University of Tsukuba, Ibaraki, Japan.
Insights
Mechanical and non-mechanical factors influence hypertensive heart disease. Non-mechanical factors, like beta-adrenergic receptor function, significantly impact myocardial function and clinical outcomes in patients with hypertension.
Area of Science:
- Cardiology
- Internal Medicine
- Physiology
Background:
- Essential hypertension can lead to left ventricular (LV) hypertrophy.
- Understanding the interplay of mechanical and non-mechanical factors is crucial for managing hypertensive heart disease.
- Cardiomyopathies like hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) provide comparative models for studying myocardial adaptation.
Purpose of the Study:
- To investigate the roles of mechanical (e.g., end-systolic wall stress) and non-mechanical factors in hypertensive cardiac hypertrophy.
- To assess the inotropic response to isoproterenol and its correlation with hypertrophy and wall stress.
- To evaluate the impact of antihypertensive treatment on cardiac structure and function.
Main Methods:
- Echocardiography was used to assess left ventricular (LV) structure and function in 125 hypertensive patients, 20 with HCM, and 20 with DCM.
- Hypertensive patients were categorized based on LV hypertrophy and end-systolic wall stress (ESS).
- Inotropic response was measured by the change in fractional shortening (FS) corrected for ESS (delta FS/delta ESS) following isoproterenol infusion.
Main Results:
- The inotropic response (delta FS/delta ESS) varied significantly across groups, being higher in patients with subnormal ESS (HI) and HCM compared to those with normal ESS and severe hypertrophy (HIIB), DCM, and dilated groups.
- Antihypertensive treatment led to a significant decrease in LV mass in most hypertensive subgroups, except for the HI group.
- These findings suggest a complex regulation of the hypertensive heart involving both mechanical load and intrinsic myocardial properties.
Conclusions:
- Hypertensive cardiac hypertrophy is modulated by a combination of mechanical and non-mechanical factors.
- Non-mechanical factors, such as beta-adrenergic receptor function, play a significant role in determining the clinical presentation and progression of hypertensive heart disease.
- The diverse responses observed highlight the heterogeneity of myocardial adaptation in response to chronic pressure overload.
Abstract:
To investigate the clinical roles of mechanical and non-mechanical factors in hypertensive hypertrophy, 125 patients with essential hypertension, 20 with hypertrophic cardiomyopathy (HCM) and 20 with dilated cardiomyopathy (DCM), were studied using echocardiography. The hypertensive patients were separated into 3 groups: those with left ventricular (LV) hypertrophy (H), those without hypertrophy (H(-)) and those with dilatation (D). Group H patients were separated into 3 subgroups: those with subnormal LV end-systolic wall stress (ESS) (HI), those with normal ESS and mild hypertrophy (HIIA), and those with normal ESS and severe hypertrophy (HIIB). The inotropic response to isoproterenol infusion (0.02 microgram/kg/min for 5 min) was measured by the increase of fractional shortening (FS) corrected for the decrease of ESS (delta FS/delta ESS). After antihypertensive treatment for 4.4 +/- 1.7 years, echocardiography was repeated. delta FS/delta ESS was significantly larger in HI and HCM than in HIIA, was significantly larger in HIIA than in HIIB in which it was significantly larger than in D and DCM. After the treatment, LV mass decreased significantly except in HI. In conclusion, hypertensive hearts are regulated by mechanical and non-mechanical factors. Non-mechanical factors, for example the function of beta-adrenergic receptors in myocardium, have a variety of influences on myocardium, causing a broad spectrum of clinical features and courses.