Calf venous compliance in multiple system atrophy

A. Lipp, P. Sandroni, J. Eric Ahlskog, D. M. Maraganore, C. W. Shults, P. A. Low

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

In multiple system atrophy (MSA), increased venous compliance with excessive venous pooling is assumed to be a major contributor to orthostatic hypotension (OH); however, venous compliance has never been assessed in MSA patients. We evaluated the severity and distribution of adrenergic, cardiovagal, and sudomotor failure in 11 patients with probable MSA, 14 age- and sex-matched control subjects, and 8 patients with Parkinson's disease (PD) but not OH. Calf venous compliance, venous filling, and capillary filtration were measured using calf plethysmography. The response to the directly acting α-adrenergic stimulation (10 mg midodrine) on calf venous compliance was additionally evaluated. Contrary to our hypothesis, pressurevolume curves in the legs of MSA patients were flatter than in PD patients (P < 0.05) or controls (P < 0.001); this indicated reduced calf venous compliance in MSA. The MSA group had reduced venous filling compared with control (P < 0.001) or PD subjects (P < 0.001) but had a normal capillary filtration rate (P = 0.73). Direct α-adrenergic stimulation resulted in a slight but significant reduction of calf venous compliance in controls (P = 0.001) and PD subjects (P < 0.001) but not in the MSA group. The compliance change in MSA significantly regressed with autonomic failure (composite autonomic severity scale, r2 = 0.56) but not with parkinsonism (Unified MSA Rating Scale, r2 = 0.12). Our data indicate that MSA patients with chronic OH have reduced, rather than increased, venous compliance in the lower leg. We postulate that chronic venous distension that is associated with OH results in structural remodeling of veins, leading to reduced compliance, a change which may protect patients against orthostatic stress.

Original languageEnglish (US)
Pages (from-to)H260-H265
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume293
Issue number1
DOIs
StatePublished - Jul 2007

Keywords

  • Orthostatic hypotension
  • Vascular capacitance
  • Vasoconstriction
  • Veins

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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