Systolic flow augmentation in hearts ejecting into a model of stiff aging vasculature: Influence on myocardial perfusion-demand balance

Akio Saeki, Fabio Recchia, David A. Kass

Research output: Contribution to journalArticlepeer-review

Abstract

Age-related arterial stiffening and widening of the pulse pressure elevates ventricular systolic wall stress while it lowers diastolic coronary perfusion pressure. These changes are thought to adversely alter the balance between myocardial work load and blood supply. To test this hypothesis, the native compliant thoracic aorta was surgically bypassed by a stiff tube in reflex-blocked anesthetized dogs. Ventricular outflow was directed into either native aorta or the bypass; the latter resulting in an increase in arterial pulse pressure from 37.8 to 107.5 mm Hg (P<.001), with minimal change in mean pressure and flow. Cardiac work load was assessed by pressure- volume area (PVA), which combines external and internal left ventricular work and is linearly related to myocardial oxygen consumption (MV̇O2), and by MV̇O2 itself. Regional phasic and mean coronary flow were measured in the left anterior descending coronary artery, and global flow was assessed by radiolabeled microspheres. Myocardial supply-demand balance was assessed by comparing flow at matched PVA or MV̇O2, flow-PVA relations, and endocardial-to-epicardial flow ratios. When blood flow was directed into the stiff bypass tube, peak systolic pressure, wall stress, and PVA all rose nearly 50%, yet diastolic perfusion pressure fell by 20 mm Hg (all P<.01). Rather than being compromised, however, mean coronary flow rose by 34%, maintaining the same endocardial-to-epicardial flow ratio (≃1.1). Flow augmentation persisted when data were compared at matched work load (PVA or MV̇O2) and mean arterial pressure, as well as over a range of work loads (P<.001 from ANCOVA of flow-PVA relations). The increased flow resulted from enhanced systolic perfusion, which nearly equaled diastolic flow when ejection passed into the stiff bypass. These data counter the notion that cardiac coupling with a stiff arterial system (as with aging) necessarily compromises myocardial flow versus metabolic demand. However, the data highlight a greater role of systolic flow under such conditions and also raise the novel suggestion that enhanced pulsatility of the arterial pressure waveform may itself augment coronary perfusion.

Original languageEnglish (US)
Pages (from-to)132-141
Number of pages10
JournalCirculation research
Volume76
Issue number1
DOIs
StatePublished - Jan 1995

Keywords

  • aging
  • arterial compliance
  • coronary flow
  • pressure-volume area
  • systolic hypertension

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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