The past thirty years have witnessed the birth, growth, and evolution of clinical electrophysiology from a field whose initial goals were the understanding of arrhythmia
mechanisms to one of significant therapeutic impact. The development and refinement of implantable devices and catheter ablation have made non-pharmacologic
therapy a treatment of choice for most arrhythmias encountered in clinical practice.
The historical route to present-day patch clamping started with the
scientific recognition that electrical phenomena are part of animal physiology.
This bioelectricity was demonstrated in the nineteenth century in
frogs, where muscle movements could be evoked by applying electrical
stimuli to the animal. The recording of inherent electrical activity can be
charted by the development of increasingly sophisticated electrodes.
The concept of rate-modulated (rate-responsive, rate-adaptive) pacemakers is to move beyond simple backup pacing for bradycardias to helping a patient adapt to physiologic stress with an increase in heart rate, even if the patient's intrinsic sinus node normally would not allow this to occur. The development of dual-chamber pacemakers allows a patient to increase the heart rate if he or she is in sinus rhythm and sinus function is intact. Many patients, however, have sick sinus syndrome that prevents normal physiologic sinus node response to exercise, stress, or chronic atrial fibrillation.