急性心筋梗塞の伝導障害におけるヒス束心電図について

Nine out of 55 patients with acute myocardial infarction needed temporary cardiac pacing. His bundle electrograms were examined in these nine patients (one with anteroseptal and eight with inferior or infero-posterior wall infarction) at the time of pacing catheter insersion and/or of withdrawal. The changes of AH and HV intervals in relation to the patient's status, and the relation of the pattern of His bundle electrogram to the presence or absence of Adams-Stokes syndrome, to heart failure and to the hospital mortality were investigated.<br>The initial mean AH interval was much prolonged (complete AH block in one case, and the others mean value was 221.0 ± 66.5 msec) but the second examination revealed marked improvement in AH interval (111.3 ± 266.6msec). This finding was especially true in the inferior wall infarction group. The mean value of HV intervals in the first examination was 49.2 ± 14.6 msec and that of the second examination was 60.8 ± 14.2 msec. One patient with inferior wall infarction and prolonged HV interval of 75 msec on the initial examination, showed only slight improvement in HV interval of 70 msec at the time of pacing catheter withdrawal. Another patient, who initially had normal HV interval of 50 msec, showed HV interval prolongation to 63 msec on the second examination. These findings showed that no significant improvement would be expected on HV interval.<br>Three of the nine patients experienced Adams-Stokes syndrome. One patient with anteroseptal wall infarction, who experienced syncope due to high degree A-V block onlyduring the attack of an angina pectoris, showed no abnormality on His bundle electrogram examined at an angina free period. The other two patients with inferior wall infarctions had definite HV block; the HV intervals were 70 and 75 msec respectively. This suggests that even in the case of inferior wall infarction, syncope due to HV block can occur with appreciable frequency.<br>Seven patients had signs of heart failure, and all three of the patients with HV block were included in this group. The number of deaths during the admission was four, but none died due to conduction disturbance alone. And no relation was found between the pattern of His bundle electrogram and the hospital mortality.<br>This data suggest the followings:<br>1) AH block may be transient but HV block is usually not.<br>2) Even in the cases of inferior wall infarction complicated by A-V block with Wenckebach period, prophylactic pacing will be needed to prevent a syncope due to sudden onset of severe HV block.<br>3) Patients with HV block are usually included in the heart failure group.<br>4) His bundle electrogram at the time of pacing catheter withdrawal is very beneficial in evaluating the prognosis and in determining the indication of permanent pacing.