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Histopathologic exploration of intra-hisian conduction disturbances
Taka-Aki Matsuyama1, Shin Inoue, Youichi Kobayashi
1Second Department of Pathology, Showa University School of Medicine, Tokyo, Japan. zan42100@nifty.com
Insights
In intra-Hisian block, lesions causing split His potentials are primarily located in the nonbranching bundle. This segment, crucial for cardiac conduction, was found to be longer in affected hearts.
Area of Science:
- Cardiovascular pathology
- Cardiac electrophysiology
- Histopathology
Background:
- Intra-Hisian block causes split His potentials, but lesion location and His bundle length remain unclear.
- Autopsy study comparing histologic findings in intra-Hisian block versus control hearts.
Observation:
- Hearts from 4 intra-Hisian block patients and 14 controls were analyzed.
- Serial sectioning and reconstruction of the His bundle segments (penetrating, nonbranching, branching).
- Lesions were located in the nonbranching bundle (3 hearts) or penetrating bundle (1 heart).
Findings:
- The nonbranching bundle segment was significantly longer in intra-Hisian block hearts (3.5 mm) compared to controls (1.9 mm).
- Lesions were predominantly found in the nonbranching bundle near the central fibrous body-ventricular septum junction.
- Intra-Hisian block hearts were heavier than control hearts (389g vs 301g).
Implications:
- Identifies the nonbranching bundle as a key site for lesions causing intra-Hisian block.
- Provides anatomical insights into the pathogenesis of split His potentials.
- May inform future diagnostic and therapeutic strategies for conduction abnormalities.
Introduction:
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.
Methods And 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.
Conclusion:
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.