The Journal of Thoracic and Cardiovascular Surgery, Vol 79, 803-808, Copyright © 1980 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Supply-demand balance of subendocardial muscle: estimation from intramyocardial pressure
M Marzilli, HN Sabbah and PD Stein
The ratio of the dihastolic pressure-time index (DPTI) to the systolic
pressure-time index (SPTI) has been used as a predictor of subendocardial
ischemia. The DPTI is thought to reflect the blood supply to the
subendocardium, and the SPTI is thought to reflect the metabolic needs. In
this study, the supply-demand balance of subendocardial muscle was
evaluated directly from the pressure measured within the subendocardium.
The blood supply to the subendocardial muscle, estimated from the area
between the aortic pressure and the subendocardial pressure in diastole
(3,370 mm Hg sec min-1) (mean +/- SEM) was lower than the DPTI (4,060 mm Hg
sec min-1) (p less than 0.01). The metabolic demand of the subendocardial
muscle, estimated from the area included in the subendocardial pressure
(4,820 mm Hg sec min-1) was higher than the SPTI (2,480 mm Hg sec min-1) (p
less than 0.01). The supply-demand balance, directly estimated from
subendocardial pressure, 0.7, was markedly lower than the simultaneous
DPTI/SPTI ratio, 1.6. In view of the prominent differences between the
supply-demand balance estimated by these two indices, the DPTI/SPTI ratio
as a predictor of subendocardial ischemia may require further evaluation.