This in turn may allow us-greater specificity in the selection of the proper therapy for the patient with abnormalities of cardiac rhythm.
The purpose of this study was to analyzed A-V conduction in patient with normal P-R interval and to define more precisely the areas of delay or block in conduction disturbances and various arrythmias by means of the technique of His bundle recording.
The His bundle electrograms were recorded , with tripolar electrode catheter in 52 patients in Cardiac Laboratory in Severance Hospital fromj. January 1975 to June 1976.
This study consisted 33 patients with normal atrioventricular conductind 19 patients with various conduction disturbances and arrythmias. All patients except four with normal heart had underlying congenital and acquired heart diseases.
A) Normal A-V conduction time in children and adults.
In 11 children aged 2 to 15 years with a mean age of 8.9 years P-A interval ranged from 25 to 45 msec with a mean±SE of 32±2.2; A-H from 50 to 100 cosec with a mean of 65±5.2, and H-V from
30 to 45:msec with a mean of 36 ±1.4. In 22 adults aged 16 to 59 years with a mean age of 27.3 years P-A interval ranged from 25 to 50 msec with a mean of 34±1.6, A-H from 65 to 110 msec with a mean of 83±3.0, and H-V from 20 to 50 msec with a mean of 41±1.9. The P-A, A-H, and H-V intervals did not differ statistically between children and adults.
B) Various conduction disturbances and arrythmias.
1) In 7 patients with first degree A-V block the P-A and H-V intervals were normal but the prolonged A-H intervals were 142, 170, 175,140, 210, 345 and 505 msec, respectively.
2) In a patient with second degree A-V block (Mobitz type I) His bundle electrograms showed progressive lengthening of A-H intervals with P waves blocked proximal to the His bundle recording site (not followed by H potentials).
3) In two patients with complete heart block His bundle recordings demonstrated P waves not followed by conducted H Although considerable knowledge about cardiac conduction has been accumulated through the study of external electrocardiogram, the most apparent limitation of this method is that activity of the conductive system itself is not recorded. Scherlag and coworkers introduced a simple technique for recording the electrical activity of the His bundle in th, human heart. With the developments of a simple catheter technique for recording of His bundle electrogram it has become possible to subdivide the previously silent P-R interval into three subintervals, P-A, A-H, and H-V intervals. The P-A, A-H, and H-V intervals are, respectively, measures of intra-atrial (from high to low right atrium), atrioventricular nodal, and intraventricular (distal His bundle and bundle branches) conduction. His bundle recording contributes to understanding the electrophysiological mechanisms underlying atrioventricular and intraventricular conduction disturbances. The sites of conduction delay or block are anatomically and electrophysiologically localized asbeing proximal in,or distal to the His bundle. potentials while QRS complex block might be proximal to the His bundle.
4) His bundle recordings were obtained in five
patients of atrial fibrillation. In 4 patients a single His bundle potential preceded each QRS complex and H-V interval were constant from beat to beat during atrial fibrillation. In two patients right bundle potential (RB) was recorded. RB-V intervals were 20 and 15 msec, respectively, which were shorter than normal H-V interval.
5) His bundle electrograms were recorded in 2 patients of WPW syndrome with paroxymal atrial tachycardia (PAT) which were type A and type B, respectively. In all 2 patients A-H intervals were same as A-B intervals. When episodes of PAT occurred delta waves (δ) disappeared, with prolongation of A-H intervals.
6) In one patient with junctional tachycardia His bundle recording did not demonstrate A potential. When episodes of atrial tachycardia disappeared the A potential appeared.
7) His bundle electrogram was recorded in a patient with junctional rhythm (ventricular rate: 43/min). The A potential was not demonstrated while QRS complexes were preceded by H potentials.
8) Atrial pacing was performed in 1 patient. A-V nodal conduction time (A-H interval increased as the pace rate increased. But the H-V interval remained constant.
|