Significance of His bundle recordings with short H-V intervals

Escape rhythm and paroxysmal tachyarrhythmia originating from the right bundle

A rare phenomenon of escape rhythm and paroxysmal tachycardia originating in the right bundle branch, in a young female without any organic heart disease, is presented.

Paroxysmal fascicular tachycardia and ventricular tachycardia due to mechanical stimulation by a mitral valve prosthesis

Electrophysiologic studies were performed in a woman who had two varieties of paroxysmal wide QRS tachycardia after mitral valve replacement with a Starr-Edwards prosthesis. One tachycardia originated in the left anterior fascicle; QRS complexes were 100 ms wide and resembled right bundle branch block with left posterior fascicular block, and a His bundle potential preceded each QRS by an interval of 20 ms (compared with 50 ms during sinus rhythm). The other tachycardia originated in the left ventricle. Clinical and echocardiographic observations suggested that the tachycardias were caused by mechanical stimulation of the interventricular septum by the mitral prosthesis.

Paroxysmal fascicular tachycardia: electrophysiologic characteristics and treatment by catheter ablation

A 69 year old man with ischemic heart disease underwent electrophysiologic evaluation for paroxysmal wide QRS tachycardia, the configuration of which was identical to that recorded during sinus rhythm, that is, right bundle branch block, left anterior fascicular block and anterior myocardial infarction. Electrocardiographic recordings during tachycardia showed atrioventricular dissociation and His bundle activation occurring 5 ms after the onset of the QRS complex recorded on the surface electrocardiogram, consistent with a left posterior fascicular tachycardia. All traditional therapeutic attempts failed to prevent frequent recurrences of tachycardia, which was finally ablated by three 300 J shocks delivered through an electrode catheter positioned in the posterobasal region of the left ventricular septum.

Effects of lignocaine on bidirectional tachycardia and on digitalis-induced atrial tachycardia with block

Most recent studies discussing tachycardias with alternating QRS polarity have referred to those known as torsade de pointes. This report, in contrast, deals with bidirectional tachycardia and the effects of lignocaine on 10 patients with this arrhythmia. Three of the patients also had digitalis-induced atrial tachycardia with block. In one patient, a single bolus of lignocaine was followed (five minutes later) by ventricular fibrillation, but the other nine patients received two boluses of 75 mg followed by a drip infusion of 3 mg/min. The drug terminated the episodes of atrial tachycardia with block and bidirectional tachycardia in all patients thus treated. Whereas the abolition of the bidirectional tachycardia was permanent in the seven patients with digitalis intoxication, it recurred after stopping the drip infusion in the two patients without digitalis toxicity. It is concluded that lignocaine can be useful in the treatment of digitalis-induced bidirectional tachycardia and atrial tachycardia with block. From this study no conclusions can be drawn, however, as to whether lignocaine is superior to other class I or class IV agents.

Mobitz II atrioventricular block due to infra-Hisian block and bundle branch extrasystoles

An asymptomatic elderly male presented with complete right bundle branch block, left anterior fascicular block and Mobitz Type II second degree atrioventricular block. In addition, he was noted to have ventricular premature systoles. Electrophysiologic studies demonstrated two apparently different mechanisms for the second degree A-V block--infra-Hisian block and A-V block due to bundle branch extrasystoles arising in the affected right bundle branch. Concealed conduction of the bundle branch extrasystoles as the proximate cause of infra-Hisian block could not be excluded. However, both forms of A-V block were evidently dependent upon significant distal conduction system disease; this consideration was felt to warrant permanent pacemaker implantation.

The Wolff-Parkinson-White syndrome: the value of the HIS bundle electrogram,

The HIS bundle electrogram has led to the aquisition of additional information on the physiology of the WPW syndrome and has become a useful technique for its diagnosis. The findings on the HBE and their interpretation in WPW are reviewed.

[Clinical value of His bundle electrography (author's transl)]

Methodical problems, indication and clinical implication of His bundle electrography are discussed. In 200 successive patients undergoing His bundle electrography and atrial stimulation the indication was as follows: Intraventricular conduction defects in 24%, A-V block in 21%, sick sinus syndrome in 20%, preexcitation in 17%, and complex arrhythmias in the remaining cases. In 38% of the patients did the HBE prove to be of help by providing information not available after analysis of the surface ECG. In 22% this technique contributed essentially to the management of these patients. In spite of dificiencies of our knowledge of the basic mechanisms, specific therapy, and prognosis of various arrhythmias His bundle electrography is clinically useful in selected patients. Therefore, this method has become a routinely used clinical tool.

Intermittent parasystole--mechanism of protection

Analysis of ten cases of intermittent ventricular parasystole suggested temporary loss of protection of the parasystolic focus resulting in discharge and "resetting" of the parasystole by sinus or other supraventricular beats. Parasystolic centers appear to be protected from supraventricular and other ventricular ectopic impulses early in their cycle by their refractory periods, and late in the cycle by diastolic depolarization. Between these two areas of protection is a period of "susceptibility" during which supraventricular beats can discharge the parasystolic focus. This phenomenon accounted for fixed coupling of the first parasystolic beat of a series to a preceding sinus beat. Under certain conditions all parasystolic beats may have such fixed coupling, a new and previously unconsidered mechanism for parasystole with fixed coupling.

In one case of intermittent ventricular parasystole, the parasystole was shown to originate in the posterior fascicle of the left bundle branch on the basis of the shape of the standard electrocardiogram and by His bundle recordings. These parasystolic impulses produced a compensatory pause regardless of whether their discharge was manifest or concealed, and thus imitated a second degree (Type II) atrioventricular (A-V) block. This represents the first description of completely blocked atrial impulses resulting from concealed parasystolic beats arising within the ventricular conduction system.

Conduction intervals and conduction velocity in the human cardiac conduction system. Studies during open-heart surgery

Specialized fiber electrograms were recorded in 64 patients during open-heart surgery. Intervals were measured from the proximal His bundle, distal His bundle, and right and left bundle branches to the earliest QRS deflection in the limb lead ECG (pH-Q, dH-Q, RB-Q, and LB-Q interval, respectively). There was an increase of pH-Q intervals with increasing age such that at age 3 months the normal range of pH-Q interval was 13-27 msec, while at 14 years of age it was 32-54 msec. For patients 15 years of age and older, the normal range of pH-Q interval was 35-54 msec, similar to that reported by several investigators using catheter technic and suggesting that most His bundle electrograms recorded by catheter technic in fact record from the proximal His bundle. The dH-Q interval varied from 18 to 35 msec, the RB-Q interval from 18 to 30 msec, and the LB-Q interval from 20 to 39 msec. These normal ranges of RB-Q and LB-Q intervals are greater than previously reported. Overlaps existed between the normal range of pH-O and dH-Q or LB-Q intervals, dH-Q and RB-Q or LB-Q intervals and, at least in children, the pH-Q and RB-Q intervals. Thus the timing of a specialized fiber electrogram does not necessarily reflect its anatomic location. AV nodal electrograms were not recorded although the recording sites included the known anatomic location of the AV node. Conduction velocity in the His bundle was determined and averaged 1.5 m/sec (range 1.3-1.7 m/sec).

Ventricular tachycardia with narrow QRS complexes (left posterior fascicular tachycardia)

Ectopic atrial, A-V junctional, and ventricular tachycardias in man have been associated with digitalis medication. Recently it has become possible to distinguish various locations of pacemakers within the specialized conduction system of the ventricles on the basis of the form of the QRS complexes in the standard electrocardiogram. Tachycardias originating in the left bundle branch and documented by right, left, and His bundle recordings have been produced in animals given excessive digitalis. We have noted a similar tachycardia in a patient with ischemic heart disease receiving digitalis during hypokalemia. The QRS complexes were 0.10 sec in duration and by contour suggested an ectopic focus located in the posterior fascicle of the left bundle; His bundle recordings were consistent with this diagnosis. As the ectopic rhythm became synchronized with a slightly irregular sinus rhythm, bidirectional depolarization of the His bundle with fusion His potentials could be demonstrated.