Gross anatomic relationship between the human left atrial appendage and the left ventricular summit region: implications for catheter ablation of ventricular arrhythmias originating from the left ventricular summit.

PURPOSE: The left ventricular summit (LVS) is a source of difficult-to-treat arrhythmias because of anatomical limitations. The aim of this study was to perform detailed research of the left atrial appendage (LAA) anatomy of cadaveric hearts to analyze their complex anatomy and coverage of the LVS. METHODS AND RESULTS: Eighty human formalin fixed hearts (mean age 44.4 ± 15.5, 27.5% females) were investigated. Each LAA size, type, and its relationship to the LVS were analyzed, as well as possible access sites for mapping/ablating electrode. Four types of LAA were observed over two LVS sites that are either accessible or not. The highest coverage over an inaccessible LVS area was observed in the Broccoli type, followed by the Windsock then the Chicken Wing and finally the Cactus types; over the accessible area of the LVS was observed in the Windsock, then in the Chicken Wing, then in the Cactus, and finally in the Broccoli types. The attainable coverage for electrode access is diminished from 25 to 65% because of the complex pectinate muscles and sharp angles. The highest density of the LAA floor made by pectinate muscles can be found in the Broccoli type (p < 0.005), while the Chicken Wing had the highest number of paper-thin-like pouches. CONCLUSIONS: The LAA appears to be a promising entry for ablation-qualified patients with the LV summit originate arrhythmias. The complex internal structure of the LAA may complicate ablation procedures. More prominent appendages are promising in more extensive mapping areas over the LVS.

Topographical anatomy of the left ventricular summit: implications for invasive procedures.

BACKGROUND: Recent clinical reports have emphasized the clinical significance of the left ventricular summit (LVS), a specific triangular epicardial area, as the source of ventricular arrhythmias where radiofrequency ablation is of great difficulty. MATERIALS AND METHODS: The macroscopic morphology of the LVS has been assessed in 80 autopsied and 48 angio-computed tomography (CT) human hearts. According to Yamada's equation, the size was calculated based on the distance to the first, most prominent septal perforator. RESULTS: The size of the LVS varies from 33.69 to 792.2 mm2, is highly variable, and does not correlate with body mass index, sex, or age in general. The mean size of the LVS was 287.38 ± 144.95 mm2 in autopsied and angio-CT (p = 0.44). LVS is mostly disproportionately bisected by cardiac coronary veins to superior-inaccessible and inferior-accessible areas. The superior aspect dominates over the inferior in both groups (p = 0.04). The relation between superior and inferior groups determines three possible arrangements: the most common type is superior domination (50.2%), then inferior domination (26.6%), and finally, equal distribution (17.2%). In 10.9%, the inferior aspect is absent. Only 16.4% of the LVS were empty, without additional trespassing coronary arteries. CONCLUSIONS: The difference in size and content of the LVS is significant, with no correlation to any variable. The size depends on the anatomy of the most prominent septal perforator artery. The superior, inaccessible aspect dominates, and the LVS is seldom free from additional coronary vessels, thus making this region hazardous for electrophysiological procedures.

Organisation of connections between the zona incerta and the interposed nucleus.

We have examined the organisation of connections between the zona incerta (ZI), a small diencephalic nucleus deriving from the ventral thalamus, and the interposed nucleus (Int) of the cerebellum. Injections of the tracer cholera toxin subunit B were made into either the ZI or Int of Sprague Dawley rats by using stereotaxic coordinates. We have two major findings. First, there is a heavy projection from Int to ZI; there is also a small projection back to Int from ZI. After injections into Int, labelled terminals and cells tend to concentrate within the medial region of each of the cytoarchitectonically defined sectors of ZI. Second, there is an unusual laterality of connectivity between the ZI and the Int. The projection from the Int to the ZI is mainly contralateral, whilst the ZI projection back to the Int is mainly ipsilateral. In conclusion, our results indicate that the Int of the cerebellum provides a rich source of afferents to the ZI, rendering the latter in a key position to integrate information from the Int together with many other types of subcortical information it receives, particularly from the brainstem.