Ventricular tachycardia historical perspective


 * Associate Editor-in Chief: Avirup Guha, M.B.B.S.[mailto:avirup.guha@gmail.com]

Overview
A lot of developments has happened over the years on ventricular tachycardia. Throughout history many renowned researchers and health-care professionals have contributed to the understanding, definition, and recognition of VT. It still continues to be one of the most immediately fatal conditions that effects the human heart. The main problem is with the electrical conduction system of the ventricles.

Early Clinical and Experimental Observations

 * The first electrocardiographic description and evidence of Ventricular Tachycardia (VT) was given by Thomas Lewis in 1909. He described a patient with shortness of breath, precordial pain, and dropsy in whom he observed from three to eleven "successive extrasystoles". He deduced from the electrocardiogram, venous pulse recording, and clinical evidence that the rhythm was of ventricular origin.


 * In 1906, Einthoven had recorded ventricular premature beats and ventricular bigeminy using his string galvanometer.


 * In 1906 Gallavardin did landmark work in France in which he found the reason of instability of VT and its ability to convert in Ventricular Fibrillation. He challenged the fact that ventricular tachycardia was no more than a succession of extrasystoles suggesting that although the two phenomena were intimately related, the same mechanism might not be responsible for both.


 * Lewis and Smith did experimentation with dogs by simulating VT by ligating coronary arteries and was able to find characteristics of VT as we have described in the other sections.

Electrocardiographic Features

 * Robinson and Herrmann, in 1921, suggested that coronary occlusion was a frequent cause of ventricular tachycardia and the prognosis in these cases appeared to be poor. They also suggested the most initial criteria for VT classification.


 * That was modified later by Rosenberg as well as Dressler and Roesler who pointed out the occasional occurrence of fusion beats in tracings showing the arrhythmia.


 * Since then we have come a long way in making of the diagnostic criteria better with advent of Esophageal & Venous leads and Invasive Electrophylogic Studies.


 * Holter and colleagues devised radio signal technique for obtaining a longer period of observation of the patient's rhythm. Later in development portable battery-operated electromagnetic tape recording with high-speed analyzing equipment was described by Holter and has been called “Holter Monitor" ever since. This technique has led to discovery, classification and research for treatment of various forms of VT.


 * Direct intracavitary recordings from the human ventricle were reported by Lenegre and Maurice in 1945 and His bundle electrocardiograms were described by Ciraud, Latour, and Puech in 1960.
 * It was only in 1969, however, that a safe, percutaneous method of recording the His bundle electrocardiogram in man was reported. Intracardiac recordings have allowed more precise diagnosis of ventricular tachycardia and have modified the electrocardiographic criteria for diagnosing this arrhythmia.


 * In 1972, Wellens et al. reported the initiation and termination of ventricular tachycardia in patients with prior ventricular tachycardia using critically timed extrastimuli. This ability to initiate and terminate arrhythmias under controlled circumstances, as well as the ability to record from multiple sites within the heart, has allowed rapid advancement in our understanding of cardiac arrhythmias.

Physical Examination

 * Initially Phlebography was very popular amongst scientists for features of VT. Prinzmetal and Kellogg in 1934 concluded that slower, independent A waves might be encountered in two-thirds of cases of VT.


 * Schrire and Vogelpoel discovered that the so-called "cannon" A is encountered in presence of atrioventricular dissociation, but could occur in regular fashion at the same rate in nodal tachycardias.


 * The AV dissociation and its reflection was demonstrated by Wilson et al. in 1964.


 * Levine was the first who noted slight irregularity in cycle length in patients with ventricular tachycardia which was audible with the stethoscope. In 1927, he mentioned variation in intensity of the first heart sound, due to atrioventricular dissociation, and extended these observations in conjunction with Harvey in 1948.


 * Harvey and Corrado demonstrated multiple low-frequency sounds audible in ventricular tachycardia as a differential point.

Prognosis

 * In 1930, Strauss correlated prognosis with the presence or absence of organic heart disease. It was noted that 60% of the cases occurred during the fifth and sixth decade of life, with a male preponderance.


 * Congestive heart failure was present in two-thirds of the patient population and digitalis had been administered before the onset of the tachycardia in half of the patients.
 * Quinidine sulfate was acutely successful in controlling paroxysms in all cases in which it was employed. There were many other case series which had similar findings.


 * Most investigators classified ventricular tachycardia into two forms on the basis of pattern and duration of the arrhythmia. Intermittent ventricular tachycardia was defined as "runs of ventricular tachycardia separated by periods of normal rhythm, the latter often showing ventricular extrasystoles" or "short paroxysms of tachycardia lasting seconds or minutes which ceased spontaneously or were controlled readily in most cases by therapy." Persistent ventricular tachycardia was thereby defined as being of longer duration and without periods of interruption.


 * Several authors found important differences in prognosis between these groups.


 * In all these series, the prognosis in patients with no identified organic heart disease was better than in those patients with abnormal hearts. Paroxysmal ventricular tachycardia in young patients with otherwise apparently healthy hearts was thought by several investigators to run a benign clinical course.


 * With advent of more refined investigations such as cardiac catheterization, echocardiography, and endomyocardial biopsy, anatomic and histologic details were found about “primary electrical disease”.


 * Various investigators attempted to ascribe prognostic significance to morphologic characteristics of ventricular tachycardia. Lundy and McLellan categorized ventricular tachycardia by bundle branch pattern and assumed incorrectly the ventricular origin of the tachycardias from these morphologies.


 * A distinctive form of ventricular tachycardia with beat-to-beat alteration of QRS axis in a single lead has been called “bidirectional” tachycardia and was first described by Schwensen in 1922. He observed its occurrence during atrial fibrillation and linked it to digitalis intoxication.


 * Palmer and White reported its poor prognosis. The studies which followed showed the same finding of poor prognosis with digitalis.

Drug Treatment

 * Scott in 1922 described a patient in whom Quinidine could both terminate and prevent episodes of Ventricular Tachycardia. He also noticed that on discontinuing quinidine ventricular tachycardia recurred. He also hypothesized that quinidine abolished ventricular tachycardia by lengthening the refractory period of the ventricle, thereby preventing early premature ventricular beats.


 * Drury and others demonstrated that quinidine prolonged the refractory period of ventricular muscle in dogs.


 * Levine and Fulton noted that treatment with quinidine could either terminate episodes of ventricular tachycardia or it could cause them.


 * By 1950, Armbrust and Levine had followed a large population of patients and strongly advocated quinidine administration in the acute setting despite the difficulties associated with its use.


 * Procainamide was used to treat ventricular tachycardia in man in 1950 and rapidly achieved widespread use.


 * The first steps toward the development of procainamide had taken place many years earlier. In 1937, Beck and Mantz demonstrated that the topical application of procaine to the epicardium during surgical procedures reduced the occurrence of ventricular extrasystoles.


 * Procaine was limited to use under anesthesia because of its central nervous system toxicity. With further development of newer congeners, procainamide and lidocaine achieved wide clinical use.


 * Lidocaine was synthesized in 1946 and was first used clinically by Southworth and colleagues to prevent ventricular arrhythmias during cardiac catheterization.


 * Other antiarrhythmic drugs quickly followed procainamide and lidocaine. Phenytoin was first used to treat ventricular tachycardia in 1958.


 * In the 1960s a number of other drugs including beta-adrenergic blocking agents, disopyramide, bretylium, mexiletine and amiodarone were reported to be effective in treating ventricular arrhythmias in selected patients.

Cardioversion and Defibrillation

 * Once ventricular tachycardia had accelerated and become less organized, the likelihood of successful termination of the arrhythmia by drugs became more remote. Considerable experimental work had demonstrated the feasibility of using electric shocks to terminate ventricular fibrillation in a variety of experimental situations.


 * Several chance events and experimental procedure had demonstrated the use of this procedure.


 * In 1961, Alexander et al. used alternating current electively for the first time to terminate ventricular tachycardia that could not be stopped by giving antiarrhythmic drugs.


 * Over the subsequent few years, Lown and his colleagues greatly refined and popularized techniques for terminating tachyarrhythmias by electric discharges.


 * Direct current (DC) or capacitor discharge was shown to be safer and more effective than alternating current. Synchronization of the direct current discharge to the R-wave resulted in safer termination of arrhythmias and was called "cardioversion” and was used for different kind of arrhythmias.


 * Ventricular tachycardia could occasionally be terminated by thumping the chest in some patients.


 * Defibrillation even using DC discharge required much higher energies, however. These techniques were quickly accepted around the world and truly revolutionized the treatment of cardiac tachyarrhythmias. Implantable devices capable of sensing and terminating ventricular tachycardia automatically by either defibrillation or cardioversion have come into clinical use.

Overdrive Pacing

 * In 1960, Zoll and associates reported that increasing the heart rate by closed-chest cardiac stimulation had prevented recurrent ventricular tachyarrhythmias. They demonstrated that runs of ventricular fibrillation could be prevented by pacing the heart above a certain critical heart rate.


 * In the same year, Schwedel, Escber. and Furman demonstrated similar short-term benefit from transvenous right ventricular endocardial pacing.


 * Both the above experiments were in patients with heart block. Subsequently, Sowton and colleagues applied a similar technique in patients with ventricular tachycardia and fibrillation but without evidence of heart block.


 * Apparently, pacing prevented episodes of tachyarrhythmia and extrasystoles in these patients. Furthermore, these authors suggested that the combined use of antiarrhythmic drugs and overdrive pacing might be better than the use of either modality alone in some patients.


 * There were many case series and report of the use of overdrive pacing after this. These series are small with a limited follow-up period. Not all reports were favorable and long term outcomes were rarely available. Acute treatment of ventricular arrhythmias by overdrive pacing became accepted as effective in some patients.

Surgical Treatment

 * In 1959 Couch reported on a patient in whom |ventricular aneurysmectomy was successfully performed to prevent recurrent ventricular tachycardia. But the procedure has been associated with poor success rates and surgical mortality of 20-50%.


 * Newer techniques include incising the margins of an aneurysm and excising these, and extensive endocardial scar excision combined with aneurysmectomy.


 * Sympathectomy, myocardial revascularization, and mitral valve replacement have also been tried for VT repair.