Gregg phenomenon and gardenhose effect

Under physiologic circumstances, cardiac function determines myocardial oxy gen consumption and consequently coronary perfusion. Surprisingly, in a rev erse direction, improved coronary perfusion also increased myocardial oxyge n consumption and contractile function. This experimental finding, now 40 y ears old, is termed the Gregg phenomenon. Some 10 years later, in experimen ts by Arnold and coworkers, an isolated increase in perfusion pressure impr oved ventricular function. In this context, the term 'gardenhose effect' wa s coined, implying a hydraulic explanation of the Gregg phenomenon. In the following, we attempt to distinguish the Gregg phenomenon from the g ardenhose effect and to critically evaluate them.