Key Points
- Determine the dynamic adjustment rate of coronary resistance following abrupt changes in heart rate and perfusion under constant pressure versus constant flow conditions.
- Perfused the left main coronary artery of anesthetized dogs under either constant pressure (CP) or constant flow (CF).
- Recorded beat-to-beat arterial pressure and flow to derive steady-state coronary resistance.
- Quantified the rate of vascular response using t50, defined as the time needed to reach half of the total vascular adjustment.
- Dilating response t50 under CP was 5.5 ± 0.4 s for increased heart rate and 5.5 ± 0.1 s for decreased perfusion, compared with 9.3 ± 0.9 s and 9.7 ± 1.6 s under CF.
- Constricting response t50 under CP was 6.6 ± 0.5 s for decreased heart rate and 6.2 ± 0.2 s for increased perfusion, compared with 12.2 ± 1.5 s and 10.8 ± 2.2 s under CF.
- Coronary regulatory adjustments occurred faster in dogs than in goats, and dogs lacked the directional sensitivity to perfusion shifts previously observed in goats.
Structured PICO
PPopulationAnesthetized dogs
IInterventionStep change in heart rate (HR) and in perfusion (left main coronary artery perfused at constant pressure or constant flow)
OOutcomeRate of change of pressure-to-flow ratio (t50)surrogate
Coronary regulatory responses to heart rate and perfusion changes in dogs are faster than in goats and lack the directional sensitivity observed in goats.