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Large artery function and alterations in hypertension
1F.H. Manhès Hospital Centre, Fleury-Mérogis, France.
Insights
Hypertension impairs arterial hemodynamics, with aging increasing arterial stiffness and pulse pressure. Certain antihypertensive drugs effectively reduce arterial stiffness and reverse left ventricular hypertrophy.
Area of Science:
- Cardiovascular Physiology
- Hypertension Research
- Gerontology
Background:
- Hypertension is characterized by impaired arterial hemodynamics, involving fluctuations in blood pressure.
- Arterial hemodynamics are influenced by ventricular ejection, arterial distensibility, and wave reflections.
- Aging leads to stiffening of large arteries, decreasing distensibility and increasing pulse pressure amplitude.
Purpose of the Study:
- To explore the impact of aging on large arteries and its consequences.
- To investigate the effects of antihypertensive drugs on arterial distensibility and left ventricular hypertrophy.
Main Methods:
- Analysis of arterial distensibility (Di = delta D/delta P x D) in relation to aging.
- Evaluation of pulse pressure mechanisms, including incident and reflected pressure waves.
- Assessment of antihypertensive drug effects on arterial stiffness and left ventricular hypertrophy.
Main Results:
- Arterial stiffening with age increases systolic pressure and decreases diastolic pressure, raising pulse pressure.
- In older individuals, reflected waves exacerbate central systolic pressure, negatively impacting left ventricular function.
- Angiotensin converting enzyme inhibitors and calcium antagonists reduce arterial stiffness and promote regression of left ventricular hypertrophy.
Conclusions:
- Aging-induced arterial stiffening contributes to adverse cardiovascular changes, including left ventricular hypertrophy.
- Specific antihypertensive medications offer benefits beyond blood pressure reduction by improving arterial properties.
Abstract:
HYPERTENSION AND ARTERIAL HEMODYNAMICS: One of the characteristics of hypertension is an impairment in arterial hemodynamics. Any definition of hypertension has to take account of oscillatory fluctuations during the cardiac cycle, that is, fluctuations in systolic and diastolic blood pressure around mean arterial pressure. These fluctuations are determined by ventricular ejection, arterial distensibility and the timing of arterial wave reflections. EFFECTS OF AGING ON LARGE ARTERIES: Larger arteries stiffen progressively with age, due to medial and intimal thickening. This alteration can be described as a decrease in arterial distensibility (Di = delta D/delta P x D, where D is the diameter of the artery and P is the blood pressure). The most obvious consequence of arterial stiffening is an increase in the amplitude of pulse pressure, caused by an increase in systolic pressure and a decrease in diastolic pressure. Two mechanisms underlie this increase in pulse pressure: a higher incident pressure wave generated by the left ventricle into a stiffened aorta and an increase in the velocity of the pressure wave traveling forward and back in the arterial tree. In young subjects, the reflected wave causes an increase in the early diastolic wave, but in older people the reflected wave is summed with a late systolic wave, causing a dramatic increase in central systolic pressure. These phenomena affect left ventricular function adversely, increasing myocardial oxygen consumption and tending to decrease coronary blood flow. Furthermore, the increased systolic blood pressure induces left ventricular hypertrophy. EFFECTS OF ANTIHYPERTENSIVE DRUGS: Although all classes of antihypertensive drugs can reduce blood pressure, only some can decrease arterial distensibility. Angiotensin converting enzyme inhibitors and calcium antagonists have been shown to decrease the stiffness of conduit arteries and dilate peripheral arteries. This may account for the superiority of these drugs in regressing left ventricular hypertrophy.