**2. Applying electrical therapy as medicine to treat human disease**

Utilizing electric current to treat human disease is an idea that fascinated humans since antiquity. The electrical discharges produced by torpedo fish were utilized as an efficient natural source for electric shock generation by Hippocrates (460–370 BC), Scribonius Largus, and Galen (129–210 AC). It was prescribed for neurological diseases like headache, arthritis gout pain, and prolapsed anus. In 46 AD Scribonius Largus in his compendium of medical treatments known as *Compositiones* described a novel treatment for headache, where, a living black torpedo is put on the place which is in pain, and results were very encouraging. The electric organ of the electric fish can produce amplitudes ranging from 10 to 860 V with a current of up to 1 A. In cardiac science, electrical stimulation was an attractive choice for incapacitating angina pain. An induction coil with spongetipped electrodes was used in 1853 to successfully treat abnormal heart rhythms and angina. Relief of angina pectoris by electrical stimulation of the carotid-sinus nerves was achieved repeatedly [1]. The introduction of coronary artery bypass shortly after this convert the electrical stimulation procedure to obsolete. The most fascinating and valuable incorporation of electric therapy in medicine was in the arena of treating rhythm disturbances, either in bradycardia or tachycardia management The first pacemaker was implanted in a person in 1958 and the first lithium battery was introduced in 1969. The deleterious hemodynamic effects of the left bundle branch block (LBBB) had been appreciated by many intelligent observers in the cardiac communities. About 30% of heart failure subjects with reduced ejection fraction with wide QRS interval in the electrocardiogram, tend to have worse clinical outcome [2, 3]. In addition, intraventricular conduction delay (IVCD) was observed as a pathological finding with multiple hemodynamic derangements, including reduced pulse pressure, impaired diastolic function, and mitral regurgitation of functional origin [4]. Early attempts to address this pathology which demonstrated favorable acute hemodynamics and mediumterm functional improvements were observed using biventricular pacing [5, 6]. Multisite Stimulation in Cardiomyopathy (MUSTIC) Trial, published in 2001 was the first large trial demonstrating CRT benefits clinically, where three champers are paced, right atrium, right ventricle, and left ventricle. The first CRT device was implanted in the same year. In an attempt to improve the clinical outcome, 10 other prestigious trials were performed. Those 11 clinical trials constitute the determinants and guidelines dictator for CRT practice nowadays. **Table 1** illustrate the details of the inclusion criteria, comparison, and the significant findings of the most influential CRT trials [14]. Nowadays, the cardiac electrical devices communities are investigating methodologies and techniques to improve

*CRT Past, Present, and Future Directions: Toward Intelligent Responders Selection… DOI: http://dx.doi.org/10.5772/intechopen.101608*

CRT outcomes mainly in the non-responders group. The non-LBBB population is classically thought to be out of the selection criteria for CRT. In spite of that, we believe nowadays that 30–50% of these population will benefit from CRT. With this new knowledge, we should convert the necessity of LBBB criteria as lone evidence for ventricular dyssynchrony, an obsolete. In this chapter we are discussing with detail, an innovative diagnostic modalities to hunt the potential responders for CRT. Visionary insight for future speculations will conclude this CRT scientific journey.


**Table 1.** *Major clinical trials.*
