T he question of what differentiates physiological from pathological cardiac hypertrophy remains one of the most clinically relevant questions in basic cardiovascular research. The answer(s) to this question will have far-ranging importance in the fight against hypertrophic heart disease and failure. In this issue of the JCI, Perrino et al. have used a unique model system to mimic the pathophysiologic effects of an intermittent pressure overload on the heart — in effect, to examine the basic issue of what determines an in vivo pathogenic stimulus (see the related article beginning on page 1547). Their findings clearly show that it is the nature of the inciting stimulus, as opposed to chronicity, that establishes the initial pathogenic response and that a distinct disruption of the β-adrenergic system is centrally involved in the earliest alterations of myocellular physiology. These results suggest both a new paradigm for treatment options in hypertrophic cardiac disease and novel methodologies for further studies.