Table 1. List of approaches to the LVS and possible ablation coverage in the individual regions.
Approach to LVS | Reachable LVS Region | References |
Right ventricular outflow track | Septal margin, right aspect of LVS accessible area, lower right septal summit | [12,70] |
Pulmonary trunk/left pulmonary artery | Septal margin, right aspect of LVS inaccessible area, higher right septal summit | [6,73] |
Aorta–left sinus of Valsalva/left coronary cusp | Septal summit, apex of LVS, aortic–mitral continuity | [70,71,73,75,88] |
Aorta–L-R inter leaflet trigon | Septal summit, apex of LVS | [17,71,75,89] |
Left atrial appendage | Mitral margin of LVS, accessible and inaccessible area (depends on the morphology and coverage of appendage) | [68,70,83] |
Great cardiac vein/anterior interventricular vein | Mitral margin of LVS, between accessible and inaccessible areas (depends on the course of venous system) | [8,33,51,72,86,88,89] |
Epicardial–subxiphoid access | Accessible area of LVS from septal to mitral margin | [8,38,51,70,72,73,89] |
The overview of publications focusing on ablations of ventricular arrhythmias arising from the LVS region with reported success and complication rates of procedures is presented in Table 2.
Table 2. Reported success and complication rates of LVS ventricular arrhythmia ablation procedures.
Study | LVS Access (if Specified) | Total Number of Cases | Number of Successful Cases | Number of Complications |
Obel, 2006 [33] | TotalGCV | 5 | 5 | 0 |
Daniels, 2006 [72] | Total | 11 | 11 | 0 |
GCV | 9 |
Epi | 2 |
Yamada, 2008 [75] | Total | 44 | 44 | 1 |
LCC | 24 |
RCC | 14 |
NCC | 1 |
R-L ILT | 5 |
Kumagai, 2008 [73] | Total | 45 | 40 | 0 |
AMC | 3 |
MA | 8 |
LCC/RCC | 32 |
Epi | 2 |
Sacher, 2010 [85] | TotalEpi | 136 | 64 | 8 |
Yamada, 2010 [8] | Total | 27 | 22 | 0 |
GCV | 14 |
Epi | 4 |
Frankel, 2014 [12] | RVOT | 2 | 2 | 0 |
Santangeli, 2015 [38] | TotalEpi | 23 | 5 | no data |
Yamada, 2015 [86] | Total | 64 | 58(only inaccesabile area failure) | 0 |
GCV | 36 |
AMC | 28 |
Marai, 2016 [71] | Total | 10 | 10 | 0 |
R-L ILT | 5 |
AIV-GCV | 1 |
NCC | 1 |
LCC | 2 |
RCC | 1 |
Hayashi, 2017 [70] | Total | 12 | 7 | 0 |
RVOT | 7 |
LCC | 1 |
AIV | 2 |
Epi | 2 |
Yamada, 2017 [87] | not specified | 229 | 212 | no data |
Komatsu, 2018 [51] | Total | 31 | | |
GVC | 14 | 10 | 1 |
other | 17 | 17 | 0 |
Benhayon, 2018 [68] | LAA | 1 | 1 | 0 |
Yakubov, 2018 [70] | LAA | 1 | 1 | 0 |
Candemir, 2019 [88] | not specified | 21 | 15 | 0 |
Liao, 2020 [17] | R-L ILT | 20 | 16 | 0 |
Igarashi, 2020 [83] | not specified | 18 | 16 | 3 |
Chung, 2020 [89] | Total | 238 | 199 | 7 |
GCV | 91 |
EPI | 6 |
RL ILT | 139 |
RL ILT = right–left interleaflet region, GCV = great cardiac vein, Epi = epicardial approach, RVOT = right ventricular outflow track, AMC = aortic–mitral continuity, LCC = left coronary cusp, NCC = noncoronary cusp, RCC = right coronary cusp, AIV = anterior interventricular vein, MA = mitral annulus.
10. Septal Summit/Septal Aspect of the LVS
Next to the LVS concept, the second idea of the so-called “septal summit” was proposed. The septal summit is the most superior part of the interventricular septum, located near the LVS septal margin, more toward the pulmonary trunk. The septal summit extends from the ventriculo-aortic junction down to the first dominant septal perforator (Figure 1). The structures neighboring the septal summit are the right–left interleaflet trigon from the top, the left pulmonary sinus from the right aspect and the anterior interventricular groove’s content from the lateral side. Above the apex of the LVS (under the left coronary artery), the septal summit corresponds with aortic–mitral continuity.
In contrast to the LVS, the septal summit cannot be reached from the left coronary aortic cusp, the left ventricular endocardial aspect or the left atrial appendage. It is worth emphasizing that the septal summit is central to the parasternal long-axis view in transthoracic heart ultrasound examination [90]. The above-mentioned right–left interleaflet trigon is adjacent to the mid-posterior septal aspect of the right ventricular outflow tract [91]. Within the septal summit, the conus vein and posterior veins of the cone, also known as communicating veins, can be present (Figure 4A) [51].
11. Conclusions
Providing systematic and comprehensive anatomical descriptions and proper terminology in the LVS region may facilitate the exchanging of information among anatomists and electrophysiologists, increasing knowledge of this cardiac region. We postulate that the most dominant septal perforator (not the first septal perforator) should characterize the LVS definition. Abundant epicardial adipose tissue overlying the LVS myocardium may affect arrhythmogenic processes and electrophysiological procedures within the LVS region. The LVS is divided into two clinically significant regions: accessible and inaccessible areas. Rich arterial and venous coronary vasculature and a relatively dense network of cardiac autonomic nerve fibers are present within the LVS boundaries. Although the approach to the LVS may be challenging, it may be executed indirectly using the surrounding structures. Further research on LVS morphology and physiology should increase the safety and effectiveness of invasive electrophysiological procedures performed within this region of the human heart.