[Gregg phenomenon and garden hose effect].

Under physiologic circumstances, cardiac function determines myocardial oxygen consumption and consequently coronary perfusion. Surprisingly, in a reverse direction, improved coronary perfusion also increased myocardial oxygen consumption and contractile function. This experimental finding, now 40 years old, is termed the Gregg phenomenon. Some 10 years later, in experiments by Arnold and co-workers, an isolated increase in perfusion pressure improved ventricular function. In this context, the term 'gardenhose effect' was coined, implying a hydraulic explanation of the Gregg phenomenon. In the following, we attempt to distinguish the Gregg phenomenon from the gardenhose effect and to critically evaluate them.