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Cardiovascular structural adaptation drives primary hypertension by increasing precapillary resistance. Effective antihypertensive therapy requires sustained pressure reduction for structural regression, targeting myogenic activity in resistance vessels.
Area of Science:
- Cardiovascular Physiology
- Hypertension Pathophysiology
Background:
- Cardiovascular structural adaptation is a normal process.
- This adaptation significantly impacts hemodynamics, contributing to primary hypertension.
- Elevated systemic precapillary resistance is a key factor in hypertension development.
Purpose of the Study:
- To review cardiovascular structural adaptation in hypertension.
- To explain the hemodynamic importance of structural changes.
- To discuss therapeutic implications for chronic hypertension.
Main Methods:
- Review of existing literature on cardiovascular structure and function.
- Analysis of hemodynamic principles in hypertension.
- Discussion of physiological-haemodynamic factors influencing therapeutic targets.
Main Results:
- Chronic hypertension involves structural 'upward resetting' of hemodynamic equilibrium.
- Antihypertensive therapy must achieve sub-normal activity for normalization.
- Structural regression is essential but challenging due to long-term changes.
- Myogenic activity in precapillary resistance vessels is a primary target.
Conclusions:
- Established hypertension is driven by raised precapillary resistance via structural autoregulation.
- Therapeutic strategies should target myogenic activity, particularly calcium ion influx.
- Effective treatment requires sustained pressure reduction to allow structural reversal.
Abstract:
A review of the general nature of cardiovascular structural adaptation and how this per se normal process becomes of key haemodynamic importance for the development of primary hypertension, particularly with respect to the gradual elevation of systemic precapillary resistance is presented. Because of the structural 'upward resetting' of the haemodynamic equilibrium, antihypertensive therapy in reality faces a far more formidable task in chronic hypertension than merely 'normalising' a supposedly raised vascular smooth muscle activity or/and cardiac output. Rather, it must bring about sub-normal activity levels to normalise the arterial pressure level, and only when such a pressure lowering has been sustained enough to allow for structural regression towards normal dimensions is a true normalisation achieved. However, the process of structural regression takes time and is complicated by the fact that the often long duration of the high-pressure state has led to structural changes which can be quite difficult to reverse. Finally, physiological-haemodynamic reasons are discussed which direct pharmacological interferences preferentially towards the pronounced myogenic activity of the precapillary resistance vessels, which both in normo- and hypertension is by far the most dominating element behind resting smooth muscle activity in these vessels and is, moreover, especially dependent on influx of external calcium ions. As the raised precapillary resistance (by means of 'structural autoregulation') represents the key element behind the pressure rise in established hypertension, such a pharmacological interference is directed towards the proper haemodynamic site and would not directly interfere with the neurohormonal integrative control of the circulation.