Sander K, Casey B, Hansen J, Sander M, Gant NF, Cunningham G,
Victor RG
Sympathetic overactivity in pregnancy induced
hypertension
11th Scientific Meeting, American Society of Hypertension
Am J Hypert
(Apr) 9:10A 1996
Pregnancy-induced hypertension (PIH) is a serious problem for both the
mother and the developing fetus. Numerous investigations into the
pathogenesis of this syndrome have failed to elucidate the etiology.
However, it is known that this form of hypertension is associated with
an increase in peripheral resistance and is not volume-dependent. It
is important to note that treatment of this problem continues to be
difficult in part because side effects of potent antihypertensives
cause major potential health risks to the fetus. As a result few
antihypertensive agents are used, the most commonly used agent being
à-methyldopa, a peripheral sympatholytic agent that is widely used in
pregnancy to treat hypertension.
Sander et al have examined the role of increased sympathetic nerve
traffic as a contributing factor in the pathogenesis of PIH. They
measured muscle sympathetic nerve activity (MSNA) and regional
vascular resistance in 11 normotensive pregnant women and 6 with PIH.
Groups were matched for maternal age and gestational week. Mean
arterial pressure was increased in PIH (mean 96 vs 76 mmHg). Both
muscle sympathetic nerve activity and regional vascular resistance
were markedly increased in PIH as compared to normotensives.
Comment: The authors conclude that these data support the
notion that sympathetic overactivity is present in PIH patients. It
seems reasonable that this increase in sympathetic activity
contributes to elevated blood pressure in PIH. It is also noteworthy
that this finding is consistent with the effect of à-methyldopa on
blood pressure in PIH. Because the authors had not yet done
post-partum measurements it is not known whether this phenomenon is
reversible. However, since PIH is a reversible condition, it seems
likely that this would be the case as the authors predict. If this
turns out to be true, studies designed to further elucidate the
mechanisms of PIH coupled with the development of safe
antihypertensives perhaps aimed at reducing peripheral sympathetic
tone may be useful for safely managing PIH patients during the course
of their pregnancy. This would be welcomed by all clinicians who care
for these patients.
(Robert D. Toto, M.D., University of Texas Southwestern Medical
Center)
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11th Scientific Meeting, American Society of Hypertension
H: Pathophysiology :
Sympathetic nervous system
H: Special problems :
Women