Load-dependent period-doubling bifurcations in the heart of the anaesthetized pig

The onset of period-doubling behaviour in cardiac physiology is often associated with pathological states and an adverse prognosis. Changes in myocardial loading frequently accompany cardiac disease, and there is growing evidence that they may be important in the genesis of cardiac arrhythmias. This study investigates the effect of changes in myocardial loading on period-doubling bifurcations of mechanical activity in the heart of the anaesthetized pig. Changes in loading can both produce and abolish period-doubling bifurcations in the mechanical behaviour of the heart. The dual effect of changes in loading may reflect the movement of the system around a bifurcation point.