Key Points
- To evaluate how coronary capacitance influences instantaneous diastolic pressure-flow relationships and to quantify true coronary zero-flow pressure.
- Formulated a theoretical model of coronary diastolic flow incorporating vascular capacitance.
- Experimentally compared dynamic instantaneous pressure-flow curves with static constant-pressure curves using an external perfusion reservoir during prolonged diastoles in heart-blocked dogs.
- In the presence of coronary vasomotor tone, zero-flow pressure intercepts were significantly higher under dynamic conditions compared to constant-pressure conditions (27.1 ± 6.6 vs. 11.0 ± 3.0 mmHg, P < 0.001).
- Following maximal vasodilation, zero-flow pressure intercepts measured 14.2 ± 4.5 mmHg dynamically and 10.7 ± 2.4 mmHg under constant pressure (P = NS).
- Zero-flow pressure remained constant at approximately 11 mmHg under constant-pressure conditions regardless of vasomotor tone, while dynamic slopes consistently exceeded static slopes.
Structured PICO
PPopulationHeart-blocked dogs
IInterventionConstant pressure perfusion (static) using a reservoir during prolonged diastoles
CComparatorInstantaneous (dynamic) pressure-flow conditions
OOutcomeZero flow pressure intercepts (Pzf)surrogate
Coronary capacitive effects and resistance changes during diastole severely limit the interpretation of instantaneous dynamic pressure-flow relationships, with diastolic coronary perfusion ceasing at about 11 mm Hg independent of coronary tone when capacitive effects are eliminated.