History of Electrophysiology

From the desk of Secretary- IHRS
Heartfelt thanks to special friends Dr Pawan Suri, Dr Deepak Padmanabhan, Dr Avinash Verma, Dr Suchit Majumdar, Dr Shunmuga Sundaram for all their help and contributions toward IHRS website.

Cardiac electrophysiology is the science of understanding the electrical system of heart and at the same time diagnosing and treating the dysrhythmias. Although foundation for the study of arrhythmias and clinical electrophysiology was laid by Chinese pulse theory way back in 5th century BC, the most significant breakthrough in this field has occurred in twentieth century only. The initial phase of exploration evolved into diagnostic field only, although therapeutic interventions were relatively modest. The past decade has witnessed a virtual explosion in invasive electrophysiology with increasing reliance on non-pharmacologic therapies. It has evolved from the off-shoot, largely of theoretical interest to one of the major super-specialities of modern cardiology.

The human electrocardiogram, that forms the basis of electrophysiology, was first recorded in 1897, but with analysis of the site of origin and mechanism of cardiac arrhythmias using programmed electric stimulation and intracardiac activation mapping, his bundle electrogram was recorded in 1969, considered to be a major breakthrough in the field. In early 1970’s more sophisticated diagnostic electrophysiological techniques were developed to electrically map arrhythmias and guide their drug treatment or surgical ablation as per requirement. The surgical treatment proliferated in 1970’s and 1980’s with overall excellent results, however, because of associated morbidity and mortality, it was ultimately replaced by DC energy catheter ablation in 1981 and further by radiofrequency catheter ablation in 1990. The ablation therapy is now an established and definitive treatment for symptomatic SVT’s, unifocal atrial tachycardia, atrial flutter, idiopathic ventricular tachycardia and atrial fibrillation. The most common energy source used during ablation is the high energy current, however, alternative sources like cryoablation, microwave, high frequency ultrasound and laser are also being considered in specific cases. The face of radiofrequency ablation has markedly changed with the advent of 3D mapping system and future is remote or robotic catheter ablations, that will not only reduce radiation exposure but increase precision.

The treatment of bradyarrhthmias has also revolutionised over the last six decades. The first pacemaker was implanted in a 43 year old male in Sweden in 1958 and who till his survival upto 88 years of age needed 26 replacements. Initially pacemaker implantation started as a modality to improve survival, but as the pacemaker technology progressed into 21st century, the developments are no longer solely about reducing mortality but improving morbidity as well. The journey began with the single chamber fixed rate pacemaker to the current dual chamber pacemakers that are relatively more physiological, rate responsive, have sensitive sensors like accelerometers that reflect activity more accurately. The pacemaker technology has also seen advancements in the form of better tracking, wireless remote monitoring, longer battery life, MRI compatibility and more recently transcatheter- delivered leadless pacemakers and His bundle pacing (conduction system pacing).

The role of electrophysiology has extended beyond treating arrhythmias to the management of chronic heart failure and survivors of sudden cardiac death. An implantable cardioverter defibrillator (ICD) has revolutionised the treatment of patients at risk for sudden cardiac death due to ventricular tachyarrhythmia and has definitely shown a mortality benefit in many studies. Similarly, biventricular pacing has been the next physiological pacemaker which has resulted in improvements in exercise tolerance, ventricular performance, decrease in hospitalizations and death in patients of chronic heart failure with persistent symptoms and conduction disturbance.

The innovations will continue as new technologies are introduced and new technologies are driven based upon the patient safety. Despite continued progress in intracardiac electrophysiology, the future in the field appears to lie outside the heart such as body surface mapping, epicardial gene therapy to cardiac ganglia as a method of preventing atrial fibrillation, stopping VT storm and greater use of 3D advanced visualization.