| Research Abstract |
The following two studies were conducted to elucidate the cause of ventricular and supraventricular conduction disturbance, known to be lethal complications after intracardiac surgery: 1) a histologic study to clarify the spatial relationship of the atrioventricular(A-V) conduction system, particularly its central portion, with the lower margin of ventricular septal defect (VSD) as well as the attachment of the tricuspid septal leaflet (ATSL) in human cardiac specimens, and 2) an experimental study with the dog to investigate influence of the injured posterior intranodal tract(PINT),namely, a mechanism of supraventricular arrhythmia.
1)Ventricular Conduction Disturbance
Histologic materials were 26 cardiac specimens consisting of normal(5),isolated perimembranous VSD(13) and tetralogy of Fallot(TOF)(8). Results may be summarized as follows: In isolated perimembranous VSD of inlet type , the nonbranching bundle(NBB;the penetrating bundle was omitted from the NBB purposely) lay on the righ
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t ventricular side of the septum and more closely to the lower margin of defect as well as the ATSL, compared with isolated perimembranous VSD of other types or TOF of muscular defect. Both the NBB and ATSL were located about same level in this anomaly.
In TOF of perimembranous defect, the NBB ran more superficially compared with that of muscular defect, and the A-V node and PB were the portion of the A-V conduction system which lay most closely to the ATSL. Such anatomical data well support the clinical fact that conduction disturbance occurred more frequently in isolated perimembranous VSD of inlet type or TOF of perimembranous defect than in those of other types.
2)Supraventricular Conduction Disturbance
Using dogs with dysrhythmia produced experimentally,atrial conduction pattern was investigated by epicardialmapping, and duration of atrial flutter (AF) or fibrillation (af) induced by atrial high-frequency electric stimulation was determined. The same items were investigated in dogs with the PINT incised longitudinally as well as in those with the atrium incised except for the PINT. The results turned out as follows: After incision along the PINT,marked conduction delay was noted at the injured portion,whereas after incision except for the PINT, no remarkable conduction disturbance was found. After incision along the PINT, sustained AF or af was induced in 10 of 22 dogs(AF induced in 7 of them);there was a significant difference(p<0.01) in arrhythmic incidence between both groups. It is inferred that a longitudinal injury along the PINT causes serious ill-effects to intraatrial conduction, which may in turn not infrequently produce(by re-entry mechanism). Less
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