Editorial Br J: first published as 10.1136/hrt.33.5.633 on 1 September 1971. Downloaded from

British HeartJournal, I971, 33, 633-638. His bundle electrograms

Charles S. Smithen' and Edgar Sowton

Since the recording of the first human electro- base of the atrial septum in the middle of the tri- cardiogram by Wailer in I889 the science of cuspid valve area where a sharp rapid biphasic has developed and ad- or triphasic deflection should appear between the vanced but has been limited the P and QRS complexes of a standard electrocardio- rapidly, by gram recorded simultaneously. The recording of inability to record electrical activity from this His potential is safe and is usually obtained specialized areas of the heart. A significant about 5 minutes after the catheter is placed in the contribution was made by Alanis, Gonzailez, femoral vein. The P-His interval, measured from and L6pez in 1958 when they recorded His the beginning of the P wave to the beginning of bundle potentials in the isolated perfused the His potential, represents conduction through dog heart using fine needle electrodes placed the and ; and the along the atrioventricular groove. The first His-Q interval, measured from the beginning of His potentials to be recorded in humans the His potential to the beginning of the QRS were described by Giraud, Puech, and complex, represents intraventricular conduction copyright. Latour and later (Fig. i). The generally recognized normal values (i960), by Watson, Emslie- for P-His interval are 80 to 140 msec and for Smith, and Lowe (I967). However, it was left His-Q interval are 35 to 55 msec. to Scherlag and associates (I969) to develop a simple and safe electrode catheter technique Validity of measurement for the consistent of electrical recording po- As there are several possible sites for recording tentials from the His bundle site in man. This electrical http://heart.bmj.com/ technique was later extended to the recording activity during the PR interval, proof of atrioventricular nodal and right bundle- that this rapid deflection represents His branch potentials (Damato et al., i969a) and bundle activity is imperative. By performing has resulted in an extensive investigation of several interventions in isolated perfused dog the specialized conduction tissue in normal , Alanis et al. (1958) were able to validate and abnormal circumstances. As a result cer- their measurements. Crushing of the SA node tain age-old concepts have now been proved resulted in His bundle activity followed by correct or have had to be ventricular activity without any correspond- modified, and in par- on September 25, 2021 by guest. Protected ticular the traditional criteria for interpreta- ing atrial potential. Production of complete tion of many dysrhythmias have been shown resulted in atrial activity followed to be inadequate. by a constantly related His potential with an independent ventricular potential. Man- Catheter technique oeuvres such as atrial stimulation, vagal In order to record the His bundle potential a bi- stimulation, acetylcholine and epinephrine polar or multipolar electrode catheter is intro- injection, or the production of asphyxia duced percutaneously into the femoral vein and appropriately modified the P-His interval under fluoroscopic control positioned across the without affecting the His-Q interval. into the right . The In man validation of the His bundle poten- proximal terminals of the electrode catheter are tial is more difficult. The position of the re- attached to an electrocardiograph amplifier and cording electrode is at the established ana- used either as a unipolar or bipolar system. His tomical position of the bundle of His. During bundle activity is best recorded at high frequency several successive cardiac cycles the configura- settings of 4O to 5OO cps at a paper speed of ioo or 200 mm/second. The position of the recording tion of the potential should not vary signifi- electrode is then adjusted until it is stable at the cantly, and the distance from the P wave should not vary by more than 5 msec. This 1 Address: Department of , Guy's Hospital, configuration and relation to the P wave has London. been validated by direct placement of the 1 634 Smithen and Sowton Br Heart J: first published as 10.1136/hrt.33.5.633 on 1 September 1971. Downloaded from

P-right bundle-branch interval is also pro- 801min longed with atrial pacing. The right bundle potential is normally about I0 msec in dura- tion and appears closer to the QRS complex, whereas the His potential is I5 to 20 msec in duration and appears closer to the P wave. However, if only one potential is recorded it H. B. E. *I*$# I is difficult to say for certain where it is re- corded from. Narula, Scherlag, and Samet (I97od), by pacing at the site of the electri- cal activity, were able to distinguish these two potentials. Pacing the right bundle- branch resulted in left bundle-branch block, whereas pacing the bundle of His caused no change in the QRS configuration. The pacing stimulus to QRS interval was the same as the His-Q interval recorded during sinus rhythm. Thus, for absolute separation of the His bundle and right bundle-branch potentials, LEAD 2 pacing at the recording site appears necessary. During the past few years it has become apparent largely from histological studies that the aetiology of complete atrioventricular block is usually due to pathology in the main bundle-branches rather than in the atrio- ventricular node (Lenegre, I964; Lepeschkin, copyright. 'HF"

and not those in the atrioventricular node. Sandler (I966) may be extremely misleading http://heart.bmj.com/ The site ofheart block in patients with acute particularly in the absence of P waves as myocardial infarction was recently studied by occurs in atrial fibrillation. A His bundle Rosen and associates (197ob). In patients with recording will conveniently allow this distinc- diaphragmatic myocardial infarctions, the tion because ventricular ectopics will not be block was found to be proximal to the His preceded by a His deflection whereas aberrant potential, while in anterior myocardial infarc- beats will, the His-Q interval being the same tions the block was distal. Since go per cent as for the normal complexes. Recently a

of the time the right coronary artery supplies patient presented to us with atrial fibrillation, on September 25, 2021 by guest. Protected the atrioventricular node, it is not surprising on large doses of digitalis. The standard elec- to find that the block occurring with diaphrag- trocardiogram (Fig. 2) revealed several wide matic infarcts, usually due to right coronary QRS complexes which were felt to be ven-

FIG. 2 Rhythm strip (lead VI) of a patient with coronary artery disease taking digitalis (see text). Atrial fibrillation is present. The wide QRS complexes were interpreted as ven- tricular ectopic beats, but aberrantly conducted supraventricular complexes could not be excluded. 636 Smithen and Sowton Br Heart J: first published as 10.1136/hrt.33.5.633 on 1 September 1971. Downloaded from tricular ectopics, and the clinical impression studied by Goldreyer and Bigger (I97I) in 5 was that of digitalis toxicity. However, a His patients with episodes of paroxysmal supra- bundle electrogram revealed that each wide ventricular tachycardia. In all 5 patients His QRS complex was preceded by a His poten- bundle potentials were recorded during tachy- tial and the His-Q interval was the same in all cardia. Every episode of tachycardia was complexes (Fig. 3). Because of this, digitalis initiated by an atrial premature depolarization was continued rather than stopped, diuretics with prolonged conduction from atrium to were introduced, and shortly thereafter the His bundle. However, in 2 patients a pre- aberrant beats disappeared. mature depolarization induced supraventricu- The distinction between supraventricular lar tachycardia but failed to propagate across tachycardia with aberration and ventricular the entire atrioventricular node to stimulate tachycardia can also be different. His bundle the bundle of His. Since His bundle depolar- recording can be of value in this situation by ization was not required for supraventricular recording His potentials in front of QRS tachycardia initiation, it can be inferred that complexes in supraventricular dysrhythmias the site of re-entry in these patients was and not in ventricular dysrhythmias. within the atrioventricular node. By recording from the specialized conduc- His bundle electrograms have proved useful tion system, Damato and Lau (I969) have in the study ofthe genesis ofWolff-Parkinson- been able to show that middle and low 'nodal' White syndrome. In 2 cases, Castellanos and rhythms usually arise from the bundle of His. co-workers (1970) were able to show ventricu- During these 'His bundle rhythms', a single lar activation which preceded a His potential, His deflection and no nodal deflection pre- suggesting that ventricular pre-excitation was cedes each QRS complex. The His-Q interval due to a bypass of the His bundle. The same during tachycardia is the same as that during group also demonstrated that during supra- sinus rhythm. Retrograde conduction from ventricular tachycardia in Wolff-Parkinson- the His bundle through the atrioventricular White syndrome antegrade conduction con- node to the atrium has been shown, and in sistently occurred through the His bundle some cases nodal and His activity are inde- whereas retrograde conduction did not (Cas- copyright. pendent ofeach other, while His and ventricu- tillo and Castellanos, I970). They concluded lar deflections have a constant relation. that the reciprocating tachycardias in this Paroxysmal supraventricular tachycardia syndrome were probably a result of two separ- has been shown recently to be usually caused ate anatomical communications, but re-entry by re-entry in the atrioventricular conduction within the atrioventricular node was not system (Bigger and Goldreyer, I970; Gettes excluded. and Yoshonis, 1970). The site of re-entry was http://heart.bmj.com/

FIG. 3 His bundle recording during the rhythm seen in Fig. 2. A His bundle potential precedes each QRS complex regardless of configuration. The His-Q interval is 50 msec. The second andfourth complexes are normally conducted and the first and third complexes are abnormal. Paper speed is IOO mm/sec (see text). on September 25, 2021 by guest. Protected

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U.C.G. , F His bundle electrograms 637 Br Heart J: first published as 10.1136/hrt.33.5.633 on 1 September 1971. Downloaded from

Drug studies bundle electrograms in man one of the most One of the more important applications of useful tools to become available to cardio- His bundle electrograms has been the study of logical investigators and clinicians in recent the effect of certain cardiac drugs on atrio- years. ventricular conduction in man. With this technique it has been possible to show that References isoprenaline and shorten atrioventri- atropine Alanis, J., Gonzilez, H., and L6pez, E. (I958). The cular nodal conduction (Damato et al., I969b) electrical activity of the bundle of His. J7ournal of and digitalis prolongs it (Damato and Lau, Physiology, 142, 127. I970). None of these drugs affect intraven- Bigger, J. T., Jr., and Goldreyer, B. N. (I970). The tricular conduction. We studied the effect of mechanism of supraventricular tachycardia. Circu- lation, 42, 673. certain beta-adrenergic blocking agents on Castellanos, A., Jr., Chapunoff, E., Castillo, C., May- atrioventricular conduction using bundle of tin, 0., and Lemberg, L. (I970). His bundle elec- His recordings (Smithen, Balcon, and Sowton, trograms in two cases of Wolff-Parkinson-White I97I). Propranolol, in doses within the known (pre-excitation) syndrome. Circulation, 41, 399. Castillo, C. A., and Castellanos, A., Jr. (I970). His therapeutic range, produced a significant bundle recordings in patients with reciprocating increase in atrioventricular nodal conduction tachycardias and Wolff-Parkinson-White syndrome. of up tO I7 per cent without affecting intra- Circulation, 42, 27I. ventricular conduction. Dextropropranolol Damato, A. N., and Lau, S. H. (I969). His bundle rhythm. Circulation, 40, 527. produced a much smaller but still statistically Damato, A. N., and Lau, S. H. (1970). Clinical value significant change in the P-His interval with- of the electrogram of the conduction system. Pro- out affecting the His-Q interval and practolol gress in Cardiovascular Disease, 13, II9. produced no significant effect on either inter- Damato, A. N., Lau, S. H., Berkowitz, W. D., Rosen, K. M., and Lisi, K. R. (I969a). Recording of val in the doses used. specialized conducting fibers (A-V nodal, His The effects of lignocaine and procainamide bundle, and right bundle branch) in man using an on atrioventricular conduction have been electrode catheter technic. Circulation, 39, 435. studied by Rosen et al. (I97oa). In the usual Damato, A. N., Lau, S. H., Helfant, R. H., Stein, E., copyright. Berkowitz, W. D., and Cohen, S. I. (I969b). Study clinical doses lignocaine had no effect on of atrioventricular conduction in man using elec- atrioventricular and intraventricular conduc- trode catheter recordings of His bundle activity. tion whereas procainamide usually prolonged Circulation, 39, 287. both these intervals. Damato, A. N., Lau, S. H., Helfant, R., Stein, E., Patton, R. D., Scherlag, B. J., and Berkowitz, W. D. (I969c). A study of heart block in man using Future developments His bundle recordings. Circulation, 39, 297. http://heart.bmj.com/ Gettes, L. S., and Yoshonis, K. F. (I970). Rapidly Though a great deal of information has recurring supraventricular tachycardia: a manifes- already been obtained, application of this tation of reciprocating tachycardia and an indica- technique will help solve new problems in the tion for propranolol therapy. Circulation, 41, 689. Giraud, G., Puech, P., and Latour, H. (I960). future. The recording of left bundle-branch L'activite electrique physiologique du noeud de potentials (Narula et al., 197ob; Lau, Bobb, Tawara et du faisceau de His chez l'homme. and Damato, 1970) along with His bundle, Bulletin de l'Acadbmie Nationale de Midecine, I44, atrioventricular node, and right bundle- 363. Goldreyer, B. N., and Bigger, J. T., Jr. (I971). Site on September 25, 2021 by guest. Protected branch potentials will provide better under- of reentry in paroxysmal supraventricular tachy- standing of the normal and abnormal activa- cardia in man. Circulation, 43, I5. tion process. The problems of ventricular pre- Hoffman, B. F., Cranefield, P. F., Stuckey, J. H., and F excitation and re-entry mechanisms, and the Bagdonas, A. A. (I960). Electrical activity during effect of new the P-R interval. Circulation Research, 8, I200. pharmacological agents on atrio- Langendorf, R., and Pick, A. (I968). Atrioventricular ventricular conduction can be studied. In block, type II (Mobitz) - Its nature and clinical addition to this type of information relating significance. Circulation, 38, 8I9. to tachydysrhythmias, there are several ques- Lau, S. H., Bobb, G. A., and Damato, A. N. (1970). tions slow under Catheter recording and validation of left bundle- concerning rhythms active branch potentials in intact dogs. Circulation, 42, investigation. Do patients with sinus node 375. disease have abnormalities of atrioventricular Lau, S. H., Damato, A. N., Berkowitz, W. D., and or intraventricular conduction? Do patients Patton, R. D. (I969). A study of atrioventricular with bundle-branch block have conduction conduction in atrial fibrillation and flutter in man using His bundle recordings. Circulation, 40, 7I. defects in the other bundle-branch ? Will it be Lenegre, J. (1964). Etiology and pathology of bilateral possible to predict which patients with bi- bundle-branch block in relation to complete heart lateral bundle-branch disease will develop block. Progress in Cardiovascular Disease, 6, 409. complete heart block and when? Lepeschkin, E. (I964). The electrocardiographic diag- nosis of bilateral bundle-branch block in relation to The answers to these and other questions heart block. Progress in Cardiovascular Disease, 6, will undoubtedly make the recording of His 445. 638 Smithen and Sowton Br Heart J: first published as 10.1136/hrt.33.5.633 on 1 September 1971. Downloaded from

Marriott, H. J. L., and Sandler, I. A. (I966). Criteria, Rosen, K. M., Loeb, H. S., Chuquimia, R., Sinno, old and new, for differentiating between ectopic M. Z., Rahimtoola, S. H., and Gunnar, R. M. ventricular beats and aberrant ventricular conduc- (I97ob). Site of heart block in acute myocardial tion in the presence of atrial fibrillation. Progress in infarction. Circulation, 42, 925. Cardiovascular Disease, 9, i8. Rosen, K. M. Rahimtoola, S. H., and Gunnar, R. M. Narula, 0. S., Cohen, L. S., Samet, P., Lister, J. W., (I970c). Pseudo A-V block secondary to premature Scherlag, B., and Hildner, F. J. (197oa). Localiza- nonpropagated His bundle depolarizations: docu- tion ofA-V conduction defects in man by recording mentation by His bundle electrocardiography. of the His bundle electrogram. American Journal Circulation, 42, 367. of Cardiology, 25, 228. Scherlag, B. J., Lau, S. H., Helfant, R. H., Berkowitz, Narula, 0. S., Javier, R. P., Samet, P., and Maramba, W. D., Stein, E., and Damato, A. N. (I969). L. C. (I97ob). Significance of His and left bundle Catheter technique for recording His bundle recordings from the left heart in man. Circulation, activity in man. Circulation, 39, 13. 42, 385. Smithen, C. S., Balcon, R., and Sowton, E. (I97I). Narula, 0. S., and Samet, P. (1970). Wenckebach and Use of bundle of His potentials to assess changes in Mobitz type II A-V block due to block within the atrioventricular conduction produced by a series His bundle and . Circulation, 41, of beta-adrenergic blocking agents. British Heart 947. Journal. In the press. Narula, 0. S., Scherlag, B. J., Javier, R. P., Hildner, Smithen, C., and Sowton, E. (I97I). Analysis of F. J., and Samet, P. (I970c). Analysis of the A-V heart block and by bundle of His conduction defect in complete heart block utilizing electrograms. In Proceedings ofthe British Cardiac His bundle electrograms. Circulation, 41, 437. Society. British Heart Journal, 33, 607. Narula, 0. S., Scherlag, B. J., and Samet, P. (I97od). Watanabe, Y., and Dreifus, L. S. (1967). Second Pervenous pacing of the specialized conducting degree atrioventricular block. Cardiovascular Re- system in man: His bundle and A-V nodal stimu- search, I, I50. lation. Circulation, 41, 77. Watson, H., Emslie-Smith, D., and Lowe, K. G. Rosen, K. M., Lau, S. H., Weiss, M. B., and Damato, (I967). The intracardiac electrocardiogram of A. N. (I97oa). The effect of lidocaine on atrioven- human atrioventricular conducting tissue. American tricular and intraventricular conduction in man. Heart Journal, 74, 66. American Journal of Cardiology, 25, I. copyright. http://heart.bmj.com/ on September 25, 2021 by guest. Protected