Both technology and clinical indications have changed since the first cardiac devices. Choosing the right therapy, or abstaining from it, is the key to good clinical management. Pacemakers effectively reduce symptoms of bradycardia, prevent syncope in patients with sick sinus syndrome, and reduce mortality in high-degree atrioventricular block. Cardiac resynchronization therapy improves symptoms and survival in heart failure patients with reduced ejection fraction and ventricular dyssynchrony. Implantable cardioverter defibrillators terminate life-threatening ventricular arrhythmias and are indicated for the prevention of sudden cardiac death, either as secondary prevention in survivors of ventricular fibrillation or ventricular tachycardia with hemodynamic compromise or as primary prevention due to heart failure with reduced ejection fraction or other miscellaneous diseases. More recently, leadless pacemakers and subcutaneous implantable cardioverter defibrillators have been developed as alternatives in specific conditions. 2
Pacemaker therapyThe medical properties of electricity have been known for some time. The physicians of ancient Rome treated acute gout with electric sea creatures. Alexander von Humboldt tested the theory of electrical conduction in biological tissue on himself. The first artificial pacemaker, powered by a hand-cranked motor, was invented by Albert Hyman in 1932. The first patient to receive an implantable pacemaker, Arne Larsson, had to wait until 1958, when he underwent the procedure at the Karolinska Clinical Indications for Therapeutic Cardiac Devices DOI: http://dx.doi.org/10.5772/intechopen.82463 University Hospital in Stockholm. He outlived both the surgeon Åke Senning and the engineer Rune Elmqvist who developed the system [1].
EtiologyThe most common etiology of bradycardia leading to pacemaker implantation is conduction tissue fibrosis, but there are several others etiologies responsible for slow heart rates according to data from registers, for example the Swedish pacemaker registry [4]. Some of these are reversible, such as infection/inflammation, metabolic conditions, and medications while others are congenital such as third-degree atrioventricular (AV) block associated with maternal systemic lupus erythematosus [5].
Pacing modeA code of four to five letters is used to describe the pacing mode. The first letter indicates where pacing occurs (where A stands for atrium, V for ventricle, and D for dual); the second describes which chamber is sensed. In the third position, the letters I (inhibit), T (trigger), or D (dual) are used to describe in which way the device responds to sensed events. An R in the fourth position means that rate response (increased pacing rate during physical exertion) is active. Finally, a fifth letter is occasionally used to describe where multicenter pacing is employed (A, V, or D) [6].
Rate responseThe purpose of rate response is to increase the heart rate in response to altered demand, and there are different solutions available to achieve this. Act...