Final answer:
The statement is True. An idioventricular rhythm occurs as a backup mechanism when the sinoatrial node and junctional pacemakers fail, allowing the heart to continue pumping blood.
Step-by-step explanation:
True or False: Idioventricular rhythms occur when the sinoatrial and junctional pacemakers fail to initiate an impulse. This statement is True. The normal rhythm of the heart, known as the sinus rhythm, is governed by the sinoatrial node. When the sinoatrial node and any possible secondary pacemakers (like the atrioventricular node) fail, the heart's backup system takes over, leading to an idioventricular rhythm. This rhythm originates within the ventricles and is significantly slower than the normal sinus rhythm and lacks coordination with the atria. An idioventricular rhythm is a safety mechanism that ensures the heart continues to pump blood, albeit less efficiently, during a failure of the higher centers of cardiac rhythm regulation.