The Journal of Thoracic and Cardiovascular Surgery, Vol 82, 216-220, Copyright © 1981 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
The effect of altitude-induced hypoxia on regional myocardial blood flow
DP Jones, R Damiano, JL Cox and WG Wolfe
Mechanical obstruction of the pulmonary artery causes an increase in right
ventricular myocardial blood flow (MBF) proportional to the increased work
load. This study was done to assess the response of MBF to hypoxia in the
absence of mechanical obstruction of the right heart. The effects of
hypoxia on cardiac performance and regional MBF were studied in ten awake,
unanesthetized dogs at 4,600 m (15,000 feet). Intracardiac pressures and
pulmonary artery (PA) and thoracic aorta blood gases were recorded daily,
initially at sea level and subsequently at 3,000 m and 4,500 m altitude.
Regional MBF was measured on days 1 (control), 3, and 5 by use of 8 to 10
mu radioactive tracer microspheres, followed by postmortem assessment of
subepicardial and subendocardial flow patterns in the left ventricle (LV),
septum, and right ventricle (RV) (4,600 m). The results indicate that: (1)
RV and PA pressures increase linearly with increasing degrees of hypoxia,
(2) MBF increases in both the RV and LV with increasing degrees of hypoxia
and elevated right-sided pressures, without increased systemic pressure,
and (3) the transmural distribution of MBF is unaltered in both the BV and
LV with altitude-induced hypoxia. These findings are distinctly different
from those in which right-sided pressures are elevated secondary to
mechanical obstruction of the PA in the absence of hypoxia.
