British Heart Journal, 1975, 37, 583-592. Atrioventricular conduction in patients with clinical indications for transvenous cardiac pacing1 Stafford I. Cohen, L. Kent Smith, Julian M. Aoresty, Panagiotis Voukydis, and Eugene Morkin From the Cardiac Unit, Department of Medicine, Beth Israel Hospital and Harvard Medical School, Boston, Massachusetts, U.S.A. Eighty patients with clinical indications for cardiac pacing had atrioventricular conduction analysed by His bundle study. The indicationsfor cardiac pacing included high grade atrioventricular block, sick sinus node syndrome without tachycardia, bradycardia-tachycardia syndrome, unstable bilateral bundle-branch block, and uncontrolled ventricular irritability. Complete heart block, Wenckebach block (Mobitz I), and 2:i block were notedproximal and distal to the His bundle. Mobitz II block only occurred distal to the His bundle. Ofspecial interest were the high incidence ofdistal conduction abnormalities by His bundle analysis (40/80, 5o%), the re-establishment ofnormal atrio- ventricular conduction in acutely ill patients with recent evidence of heart block, and the high incidence of intraventricular conduction disturbances on standard electrocardiogram (48/8o, 60%). Intensive study of atrioventricular conduction by occurring electrophysiological data in this large His bundle analysis has been performed in a variety group of patients in clinical need of pacemakers of patient populations. In many instances studies constitutes the substance of this report. The data were electively undertaken in patients who had should be representative of the cardiac conduction never been threatened by a compromising cardiac abnormalities which present in a general hospital. arrhythmia. In addition, abnormalities of atrio- ventricular conduction were frequently achieved by Subjects and methods pacemaker-induced acceleration of the atrial rate. Atrioventricular conduction was studied in 8o patients The purpose of this study was to characterize atrio- referred for temporary or permanent cardiac pacing. ventricular conduction in a group of patients who Temporary transvenous pacing was performed via the had clinical indications for a cardiac pacemaker. transfemoral route with a No. 5 bipolar catheter. The ring electrodes were 2 mm in width and spaced I cm Atrioventricular conduction was analysed by His apart. His bundle electrograms were obtained by stan- bundle electrogram in 80 patients who were referred dard methods and were recorded on an 8-channel for transvenous cardiac pacing. The clinical indi- Electronics for Medicine oscilloscope recorder. Acutely cations for cardiac pacing included third degree ill patients had temporary pacemakers inserted and block, second degree block, sick sinus node syn- electrophysiological study conducted in the cardiac drome without tachycardia, bradycardia-tachycardia catheterization laboratory or the intensive care unit. syndrome, unstable bilateral bundle-branch block, Study in the latter area was facilitated by the use of a and uncontrolled ventricular irritability. Data per- fluoroscopic bed and image intensifier. All permanent taining to atrioventricular conduction were obtained pacemakers were implanted in the cardiac catheteriza- during the course of transfemoral venous pace- tion laboratory. Patients who required permanent pace- maker revision or replacement had a No. 5 bipolar maker insertion. The characteristics of atrioven- temporary transfemoral catheter positioned for electrical tricular conduction were noted as well as standard control during the procedure. electrocardiographic evidence of remote or current Bipolar electrograms were obtained by standard intraventricular conduction disturbances. methods which defined atrial excitation (A), His bundle The presentation of the analysis of the naturally excitation (H), and ventricular excitation (V) (Scherlag et al., I969, I970; Damato et al., I969; Damato and Received 28 October I974. Lau, 1970; Scherlag, Samet, and Helfant, I972). His ISupported in part by a training grant from the National bundle electrograms were validated either by an increase Heart and Lung Institute. in the AH interval during spontaneous or induced atrial 584 Cohen, Smith, Aoresty, Voukydis, and Morkin TABLE I TABLE I (Cont'd) Case Sex Age His bundle electrogram Case Sex Age His bundle electrogram No. AH (ms) HV (ms) No. AH (ms) HV (ms) Third degree block: absent at study Sick sinus syndrome: without tachycardia-cont'd I M 55 55 95 55 F 79 II2 56 2 F 84 IIO 45 56 M 83 I50 55 3 F 84 I30 35 57 F 78 170 46 4 F 74 250 47 58 M 76 I85 47 5 M 8i 93 IOO, Mobitz I 59 M 8o II5 40 6 F 75 66 5i, Mobitz I 60 M 86 I26 43 7 F 7I I50 35 6i F 73 i60 58 8 M 63 I22 II4 62 F 8i I73 62 9 F 85 I25 40 63 M 70 88 45 IO M 56 62 47 II M 69 I50 38 Bradycardia-tachycardia syndrome 12 F 74 70 68 64 F 70 82 34 I3 M 65 I35 65 65 F 72 120 57 66 F 72 I60 38 Third degree block: present at study 67 M 8i 80 35 I4 F 8i 95 68 F 73 134 66 I5 F 84 100 i6 M 8i 200 Bilateral bundle-branch block 17 M 83 - 69 M 86 258 66 i8 M 74 87 70 M 78 I40 80 I9 F 75 66 7I M 75 I97 54 20 M 77 72 M 83 I05 42 2I M 80 I30 73 M 85 IOO 46 22 M 76 I27 74 F 63 94 35 23 M 73 II5 75 M 72 98 49 24 M 76 88 76 M 6i I06 40 25 F 77 130 77 M 6i 95 54 26 M 70 27 F 75 Control of ventricular ectopia 28 F 74 78 F 78 io8 58 29 M 68 92 79 M 76 i6o 35 30 M 86 80 M 78 I05 40 31 M 6i 145 Second degree block: absent at study 32 M 60 125 70 premature beats (Scherlag et al., I969) or by His bundle 33 F 86 I05 I40 pacing (Scherlag et al., 1972; Narula, Scherlag, and 34 F 79 120 40 Samet, 1970b). The AH interval generally delineated F 35 84 125 atrioventricular node conduction time, the normal range Second degree block: present at study of which is 50 to 120 ms. Measurements were made 36 M 68 ioi 67, 2:I from the onset of the A wave to the first clear deflection 37 M 86 253, Mobitz I 49 of the H wave. Prolongation of atrioventricular node 38 F 80 232, Mobitz I 45 conduction time was defined as first degree block of the 39 F 83 145,2:1 4I atrioventricular node. 40 M 77 102 75, 2:1 The HV interval delineated His-Purkinje conduction 41 F 80 87 87, 2:I time, the normal range of which was taken as 35 to 54 ms 42 F 8o 148 53, 2:I (Kuppersmith, Krongrad, and Waldo, I973). Measure- 43 F 79 I20,2:I 53 44 M 7I 62 57, Mobitz II ments were made from the first clear deflection of the H 45 M 6i 66 77, Mobitz I wave to the earliest onset of ventricular excitation pre- 46 F 84 88 75, Mobitz I senting in one of several sampled standard electro- 47 F 84 99 80, Mobitz I cardiographic leads or the bipolar electrograms (V 48 F 65 ioi IIO, Mobitz I wave). The HV interval is one measurement of con- 49 M 43 120, Mobitz I 58 duction through the distal specialized conduction system. 50 M 66 375, Mobitz I 47 Prolongation of the HV interval was defined as first Sick sinus syndrome: without tachycardia degree block of the intraventricular conduction system. were 5I M 64 87 34 All available electrocardiograms reviewed for 52 M 72 150 40 evidence of intraventricular conduction abnormality in 53 F 73 94 35 the bundle-branch system. Abnormal conduction in the 54 F 69 123 38 right bundle-branch, left bundle-branch, anterior divi- sion of the left bundle-branch, and posterior division of Atrioventricular conduction in patients with clinical indications for transvenous cardiac pacing 585 TABLE 2 Group No. of Normal I0 block 20 block 30 block patients atrioven- tricular AVN IVC AVN IVC AVN IVC conduction Mobitz I 30 block absent at study I3 2 5 2 2 2) (2 30 block present at study i8 6 7 5) (5 Sick sinus syndrome I3 4 5 I 3) (3 Bradycardia-tachycardia 5 2 I I syndrome Bilateral bundle-branch block 9 6 I 23 -(2 Suppression of ventricular 3 I I I ectopia Group No of Normal I° block 2° block 2:I block patients atrioven- tricular AVN IVC AVN IVC AVN IVC conduction Mobitz Mobitz Mobitz Mobitz I II I II 2° block absent at study 4 I I 2) (2 20 block present at study 15 3 4 I 2 3 I) ( )-( This symbol indicates more than one abnormality. The number of patients with the combined abnormality are noted by the number on the open ends of the symbol. AVN = Atrioventricular node, IVC = Intraventricular conduction. the left bundle-branch, respectively, result in right study (Fig. I and 2). First degree block of the atrio- bundle-branch block, left bundle-branch block, left axis ventricular node was present in 5 patients. First deviation, and right axis deviation (Rosenbaum, Elizari, degree block in the distal conduction system was and Lazzari, I970; Cohen et al., I968). Combined dis- present in 2 patients. Combined first degree block turbances in more than one conducting pathway can be in the atrioventricular node as well as in the distal recognized by combinations ofthese features. was 2 The 80 patients had an average age of 75 years, with specialized conduction system present in the 44 men averaging 72 years and the 36 women aver- patients. Wenckebach phenomenon (Mobitz I block) aging 77 years. The patients were grouped as follows: was present in the distal conducting system in 2 transient third degree block absent at study (I3), third patients.