Model-based assessment of pressure and flow-dependent coronary responses following abrupt pressure drops.

The response of the coronary vasculature to an experimental manoeuvre of step-like decrease of the perfusion pressure has been investigated with a model. The coronary vasculature was simulated using a 'windkessel' scheme. Proximal resistance and compliance were assumed to be pressure-independent. The distal resistance, on the contrary, was controlled by a feed-back loop which accounts for the smooth muscle activation induced by the pressure variation. Three more parameters were introduced, and namely the smooth muscle activation time constant and the pressure-induced and flow-induced gains. The parameter values were assessed by comparing the model predicted coronary flow with the one actually measured in animals.