Histopathologic exploration of intra-hisian conduction disturbances.
BACKGROUND
The length of the His bundle and the precise location of injury responsible for split His potentials have not been fully established in patients with intra-Hisian block. We conducted an autopsy study comparing histologic findings in intra-Hisian block versus control hearts.


RESULTS
We studied hearts from 4 intra-Hisian block patients (age 66 to 93 years, mean 79.5) and hearts from 14 patients without AV conduction abnormalities (control). All intra-Hisian block patients underwent electrophysiologic evaluation; 3 patients demonstrated intra-Hisian block and 1 showed no His potential. Autopsies were performed when each patient died. After the heart was fixed in formaldehyde, the AV septal junctional area was removed en bloc and serially sectioned into 7-microm thick slices. For study purposes, we considered the three segments of the His bundle separately: the penetrating bundle, the nonbranching bundle, and the branching bundle. The actual length of each segment was calculated from the number of respective serial sections, and the lesion was reconstructed within the conduction axis. Intra-Hisian block hearts were heavier than control hearts (mean weight 389 vs 301 g; P < 0.05). The lesion was situated in the nonbranching bundle in 3 hearts and in the penetrating bundle in 1 heart. Mean compact node length was 3.8 mm in intra-Hisian block hearts and 3.3 mm in control hearts. The penetrating bundle was 2.1 and 2.1 mm, the nonbranching bundle was 3.5 and 1.9 mm, and the branching bundle was 4.5 and 4.6 mm in intra-Hisian block and control hearts, respectively.


CONCLUSIONS
Most lesions were observed in the nonbranching bundle adjacent to the junction between the central fibrous body and ventricular septum. This segment was longer in intra-Hisian block hearts than in control hearts.
Matsuyama
Taka-Aki
TA
Second Department of Pathology, Showa University School of Medicine, Tokyo, Japan. zan42100@nifty.com
Inoue
Shin
S
Kobayashi
Youichi
Y
Saito
Tsukasa
T
Tanno
Kaoru
K
Sakai
Tetsuo
T
Otsuka
Toshihiko
T
Shiokawa
Akira
A
Katagiri
Takashi
T
Ota
Hidekazu
H
D000368:Aged; D000369:Aged, 80 and over; D002036:Bundle of His / Q000473:pathology*; D002037:Bundle-Branch Block / Q000209:etiology / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male