Back to Pacemaker implantation. Each time the heart beats, the heart muscle contracts pulls inwards in preparation for pumping blood around the body. The contractions are triggered by electrical pulses. These are generated by a group of specialised cells known as the sinoatrial node SA node.
As previously discussed, myocardium may be excited by external electrical stimuli that drive the cells to threshold. Stimulation threshold is the minimum amount of energy required to reach threshold and evoke an action potential. The intensity of the electrical stimulus is described by its amplitude measured in volts and duration measured in milliseconds. The amplitude and duration of the pulse must be optimized to ensure depolarization while minimizing battery consumption. Amplitudes are normally below 1. Pacemakers generate a constant voltage V.
Professional Reference articles are designed for health professionals to use. You may find one of our health articles more useful. NICE has issued rapid update guidelines in relation to many of these. This guidance is changing frequently. Unipolar and bipolar pacemakers [ 3 ].
Background: In the treatment of atrioventricular block, dual-chamber cardiac pacing is thought to confer a clinical benefit as compared with single-chamber ventricular pacing, but the supporting evidence is mainly from retrospective studies. Uncertainty persists regarding the true benefits of dual-chamber pacing, particularly in the elderly, in whom it is used less often than in younger patients. Methods: In a multicenter, randomized, parallel-group trial, patients 70 years of age or older who were undergoing their first pacemaker implant for high-grade atrioventricular block were randomly assigned to receive a single-chamber ventricular pacemaker patients or a dual-chamber pacemaker patients.