Venous Anatomy of the Left Ventricular Summit: Therapeutic Implications for Ethanol Infusion

Abstract

Background:

Venous ethanol ablation (VEA) is effective for left ventricular summit (LVS) arrhythmias. The LVS venous anatomy is poorly understood and has inconsistent nomenclature.

Objective:

Delineate the LVS venous anatomy by selective venography and 3D mapping during VEA and by venous-phase coronary computed tomographic angiography (vCTA).

Methods:

We analyzed: 1) LVS venograms and 3D maps of 53 patients undergoing VEA, and 3) 3D reconstructions of 52 vCTAs, tracing LVS veins.

Results:

Angiography identified the following LVS veins: 1) LV annular branch of the great cardiac vein (GCV) (19/53), 2) septal (rightward) branches of the anterior ventricular vein (AIV, 53/53), and 3) diagonal branches of the AIV 51/53. Collateral connections between LVS veins and outflow, conus, and retroaortic veins were common. VEA was delivered to target arrhythmias in 38/53 septal, 6/53 annular, and 2/53 diagonal veins. vCTA identified LVS veins (range 1 to 5), in a similar distribution. The GCV-AIV transition could either form an angle close to the left main artery bifurcation (n=16, 88°±13°) or cut diagonally (n=36, 133°±12°), p ≤0.001. Twenty-one patients had LV annular vein. In 28 patients only septal LVS veins were visualized in vCTA, in 2 patients only diagonal veins and in 22 patients both septal and diagonal veins were seen. In 39 patients the LVS veins reached the outflow tracts and their vicinity.

Conclusion:

We provide a systematic atlas and nomenclature of LV summit veins related to arrhythymogenic substrates. vCTA can be useful for noninvasive evaluation of LV summit veins prior to ethanol ablation.

Introduction

The left ventricular (LV) summit (LVS) is the most septal and superior aspect of the the left ventricular outflow tract (LVOT), bound superiorly and anteriorly by the left main coronary artery (LMCA) bifurcation and laterally by the great cardiac vein (GCV).^1–3 Arrhythmias arising in LVS pose a challenge to ablation, since catheter manipulation to reach the LVS can be difficult, and the proximity to the LMCA and its branches can generate risk of catastrophic damage. Intramural branches of the coronary venous system (CVS) offer a unique opportunity of reaching LVS arrhythmogenic foci, and retrograde coronary venous ethanol ablation (VEA) can effectively treat LVS ventricular arrhythmias (VA).^4–6 Successful VEA requires a comprehensive appreciation of the morphological arrangement of cardiac veins.⁷ The number and location of coronary tributaries varies and their size and course are also notoriously diverse.⁸ Previous studies have used computed tomography (CT)^{9, 10} to describe the relationship between the coronary venous and arterial systems and the main tributaries of the coronary sinus (CS), however, the epicardial and intramural branches of LVS tributaries have not been studied in detail. LVS vein nomenclature is often imprecise and inconsistent, as LVS veins are referred to as “communicating veins” or “septal perforators”,^11–13 without discriminating their relationship to neighboring structures such as the mitral annulus, the aortic root, the right (RVOT) and LVOT. We have accumulated substantial experience in VEA,⁶ during which a detailed appreciation of the anatomic variations of the LVS’s venous return has been generated. Here, we describe the coronary tributaries that drain the LVS and their 3D relations with neighboring structures in patients undergoing VEA using intraprocedural venograms and CT, and provide a detailed understanding of the LVS venous return that is critical for VEA’s reproducibility.

Methods

Procedural and imaging data were collected under an Institutional Review Board-approved protocol. All patients provided informed consent for the procedures.

Angiographic LVS venous anatomy

We analyzed the angiographic anatomy of LVS veins in 53 patients undergoing LVS VEA. Some (42) of the patients analyzed have been included in a previous series⁶ that focused on clinical outcomes.

All patients had ventricular arrhythmias from LVS. Fourty seven of fifty three (89%) had premature ventricular complexes (PVCs) and 6/53 (11%) had ventricular tachycardia (VT). The procedural workflow has been previously described.⁶ Briefly, after mapping the RV and LV with multipolar catheters using CARTO 3D mapping (Biosense-Webster, Irvine, CA) The CS was engaged with a sheath (Preface, Biosense-Webster) and the anterior interventricular vein (AIV) was mapped. An angioplasty guide catheter (LIMA or JR4) was advanced over the distal CS and contrast injection was delivered in multiple fluoroscopic projections, aiming to delineate intramural branches near the earliest signal as mapped in the AIV. We mapped LVS veins with a micro-electrode catheter (EPStar, Baylis, Toronto, Canada), and projected its position in the 3D CARTO maps. Balloon occlusion venograms were performed in those veins targeted for VEA.

CT LVS venous anatomy

A total of 52 patients who underwent venous-phase coronary computed tomographic angiography (CTA) were analyzed using syngo.via® (Siemens Medical Solutions, Forchheim, Germany) software.

CT protocol

CTA images were acquired using 192-slice 3^rd generation DSCT scanner (SOMATOM force, Siemens).¹² Prospective ECG-gated sequential acquisition was performed during end-systole (absolute delay x-458 ms delay) and mid-diastole (relative delay of 60–75%) or ECG-gated helical acquisition for patients with BMI ≥35 kg/m2 or with atrial fibrillation. Scans were performed using a single inspiratory breath hold. Iodixanol (Visipaque 320 mg/mL, GE Healthcare, Chicago, IL, USA) was administered into an antecubital vein. A volume of 80 to 100 mL at a flow rate of 4 mL/s was used for the image acquisition followed by 100 mL of normal saline. Acquisition was peformed during the (delayed) venous phase for optimization of vein opacification with contrast.

Volume-rendered images were created from CTA images of the coronary venous system and were analyzed. Visible LVS tributary branch veins were manually traced and counted by creating a new segmentation object for the venous system using the region growing function of Syngo.via® (Siemens). A septal LVS vein was defined as a GCV or AIV tributary branch that drains the LVS region medially (rightward) to the GCV/AIV and a diagonal LVS vein was a GCV or AIV tributary branch that drains the LVS region laterally (leftward) to the GCV/AIV. Vein angulations seen in the LVS region were also measured.

Statistical analysis

Continuous variables are expressed as mean±SD or median and interquartile ranges (P25, P75) [range] shown in parenthesis, as appropriate according to the data distribution. Paired Student t test or Wilcoxon signed rank sum test using SigmaStat 3.1 (Systat Software Inc., San Jose, CA) were used accordingly. Categorical variables are displayed as numbers and percentages. P<0.05 was considered statistically significant.

Data that support the findings of this study are available from the corresponding author upon request.

Results

Angiographic LVS venous anatomy

Baseline characteristics of the study population

Fifty three patients that were considered for VEA, aged 61±15 years, 57% men, were included (See online supplement). The presenting ventricular arrythmia was PVCs in 47 patients (89%) and VT in 6 (11%).

Venous anatomy

Although the anatomical variability was substantial, there was a consistent pattern of possible venous drainage. These veins were best visualized in left anterior oblique (LAO, 30–45°), steep caudal (40–50°) fluoroscopy projection -analogous to the “spider view” used in coronary arteriography. We analyzed the angiographic anatomy of all 53 patients considered for LVS VEA and correlated vein location with the mapped geometry of the AIV, LVOT, and RVOT on CARTO maps. Starting from the GCV, the LVS veins included: (Figure 1-schematic).

Figure 1. Schematic LVS veins.

a, angled GCV-AIV junction. b, non-angled GCV-AIV junction. LAO caudal is best to display sequence of LVS veins, while RAO foreshortens LV annular vein. LVS veins are labeled. Ao_L, Ao_R, Ao_N, left, right and non-coronary aortic cusp. PV, pulmonary valve. See text for details.

1. LV annular (LVA) vein. The LVA was present in 19/53 (36%) venograms. Defined as a branch of the GCV arising before the GVC-AIV junction, in the mitral annulus and traveling towards the septum, ending in the aorto-mitral continuity (Figure 2). The LVA communicated with atrial branches, and branches posterior to the aortic root. LVA communicated via collateral flow with the LVS septal veins in 11/19 (58%) patients (Figure 3). In the left anterior oblique projection, the LVA vein coursed more septal than the AIV, towards the aorto-mitral continuity, giving posterior branches to the left atrium and anterior branches toward the AIV septal vein, which overlapped in this projection (Figure 3f). In the right anterior oblique projection, the LVA was completely foreshortened (Figure 3) and overlapping the GCV, and only its retroaortic/atrial branches or collaterals to AIV septals were visible (Figure 3g). LVA cannulation with multielectrode catheters would typically contain atrial and ventricular signals (hence the “annular” denomination, Figure 3c). The LVA contained arrhythmogenic substrate and was targeted for ethanol infusion in a minority (6/53, 11%) of cases, with acute success in all 6 cases. Examples of LVA are shown in Figure 2, and LVA vein branching and correlation with 3D geometry of neighboring structures are shown in Figure 3. See Video 1 online.

2. LVS septal veins. Defined as branches of the AIV that ran rightward and intramural to the interventricular groove. LV septal veins coud arise as high as the GVC-AIV junction, and there were typically more than one. Figure 4 shows examples illustrating their variability. A prior report labeled some LVS septal as LVS “communicating vein”, a denomination that also included LVA veins.¹¹ LVS septal veins run rightward and also deep in the septum (true “perforators”, see Figure 3f). LVS septal veins arising at the GCV-AIV junction could connect with retroaortic branches and contain atrial signals, analogous to LVA veins, or with branches posterior to the RV outflow between the RVOT and LVOT. Figure 5 shows examples of two LVS septal veins illustrating their 3D relationships with neighboring structures: the first LVS septal had atrial and ventricular signals and was retroaortic (Figure 5a–e), whereas the second LVS septal ran anterior to the aorta and posterior to the RVOT (Figure 5f–l). More commonly, all LVS septals were located anterior to the aortic root (Figure 6) and not retroaortic (which was typical of LVA veins). LVS septals were present in all 53 venograms. The LVS septal was targeted for ethanol infusion in 38/53 cases, with success in 37/38 (97%) cases. In one case, optimal signals were recorded from the proximal portion of the LVS vein, and RF ablation was performed by proximity, guiding the ablation catheter to the earliest site in the LVS vein (Figure 6). See Video 2 online.

3. LVS diagonal veins. Defined as branches of the AIV that ran leftward to the interventricular groove. Diagnonals can arise as high as the GCV-AIV junction. This was present in 51/53 (96%) venograms. Figure 4l and 4m show examples. Despite the near consistent presence of LVS diagonal veins, they seldom harbored signals targeted for VEA. LVS diagnonal veins were targeted with success for ethanol infusion in 2 cases.

4. Collateral flow. LVS veins had commonly communicating with collateral flow with one another. LVA communicated with LVS septal veins in 11/19 (58%). LVS septal vein 1 and 2 also communicated with each other in 25/53 (47%). See Figure 3, 4i, 6 and Supplemental Figure 1.

5. Branches beyond LVS: retroaortic branches to right atrium and conus branches. Retroartic branches of either LVA veins or proximal LVS septal veins arising close to the GCV-AIV junction could extend posterior to the aorta connect with veins draining in the right atrium. Typically LVS septal ran anterior to the aorta and posterior to the right ventricular outflow tract (RVOT), but a RVOT conus vein, anterior to the RVOT was seen in 7/53 cases (Supplemental Figure 1).

Figure 2. LVS annular (LVA) vein examples.

a-l, examples of LVA shown in left anterior oblique, steep caudal projection. LVA arises from the GCV before the GCV-AIV transition, runs toward the septum, underneath the GCV-AIV junction, towards the aorto-mitral continuity (see aortic valve prosthesis in a).

Figure 3. Branching and 3D location of LVA vein.

a-d, LVA cannulated with an octapolar catheter, in left anterior oblique steep caudal (LAOc) projection (a,b). c, In right anterior oblique (RAO) projection, the LVA is foreshortened and basal, and contains atrial and ventricular signals (inset). d, Incorporating LVA to the 3D map, LVA wraps around the mitral valve in LAO (left) and posterior to the aorta in LAO cranial view (right). See Video 1 online. e-h, nonselective (e₁, f₁,g₁, h₁) vs selective LVA venograms. Selective LVA venograms show retroaortic branches and collaterals to septal branches of the AIV, both seen in LAOc (e₂, f₂, g₂) and RAO projections (e₃, g₃).

Figure 4. LVS septal and diagonal veins.

a-k, Septal branches arise at the GCV-AIV junction (S1) and in the proximal AIV (S2). Typically more than one septal branch exist, with common collateral flow between them. In RAO (g₂), septal veins are foreshortened compared to LAO. l-m, diagonal veins arising from the proximal AIV (l, shown in anteroposterior cranial view (APc), or from the GCV-AIV junction (m). Abbreviations as in Figure 3.

Figure 5. 3D location of proximal GCV-AIV LVS septal veins.

a, Octapolar catheter in first septal (S1), showing atrial and ventricular signals (consecutive, proximal-to-distal septal bipolar signals SEPp-SEPd in the inset). b, PentaRay® catheter via retroaortic approach showing apparent overlap with octapolar. c-e, Venogram and catheter positioning of S1 in RAO showing a posterior course relative to aorta, confirmed by 3D map from a left lateral view (e). f-l, Cannulation of second septal (S2). Octapolar catheter in S2 (g) shows no atrial signals (inset) and an early signal in SEPd, which was targeted with ethanol. In RAO, octapolar catheter is foreshortened (h), but 3D map shows its course anterior to the aorta. k-l, selective venogram and balloon cannulation of S2. Abbreviations as in previous figures. See Video 2 online.

Figure 6. 3D location of AIV septal veins.

a, RAO view of AIV venogram showing 2 septal branches with a collateral communication between them. b, Octapolar catheter cannulation of the first septal (S1). c, Consecutive proximal-to-distal bipolar signals from octapolar catheter (Sp to Sd) from S1 show atrial and ventricular electrograms. d, Octapolar catheter cannulation of the second septal (S2). e, Bipolar signals from S2 show earliest activation in the proximal electrodes (*), not targeted with venous ethanol but by radiofrequency ablation by proximity, given that venous ethanol cannot be constrained to the proximal portion of a large vein. f, Ablation catheter targeting endocardial site closest to earliest activation site. g-h, S1 location relative to LVOT in 3D maps. i-j, S2 location relative to LVOT in 3D maps. k-l, ablation catheter location in 3D map and intracardiac echocardiography.

CT LVS venous anatomy

Baseline characteristics of the study population

Fifty two patients, aged 66±10 years, 50% men, were included (Online supplement describes patient characteristics).

Venous anatomy

The GCV and proximal AIV were the major tributary veins seen draining the LVS region (Figures 7 and 8). Septal veins originated within the LVS region or the proximal interventricular septum before the first septal branches of the left anterior descending artery (LAD), coursed superiorly and laterally before draining in the GCV or proximal AIV (Figure 8a, b, c and d, Supplemental figure 2), with a short epicardial course. Diagonal veins originated in the lateral LVS region leftward to the AIV, coursed epicardially and medially and drained in the AIV or GCV-AIV junction (Figure 8d, Supplemental figure 2 a, d and e).

Figure 7. GCV-AIV transition angle.

As the great cardiac vein (GCV) transitions from the annulus to become the anterior interventricular vein (AIV) in the interventricular groove, a complex 3D angle is formed. a, in the lateral plane, after the GCV reaches the most septal annulus in the proximity of the left main coronary artery bifurcation, it turns upward as the left ventricle widens from the annulus to its mid portion (yellow square). b, in the frontal plane view, the GCV-AIV angle is seen as an abrupt change in direction from the annulus to the interventricular groove (yellow square). Variations existed in the presence and sharpness of the angle. Sharp angulations would render catheter cannulation of the AIV difficult. As measured in the frontal plane, we dichotomized GCV-AIV angulations as < or > than 100°.

Figure 8. Volume-rendered projections and superior-inferior vCTA images showing examples of LVS veins.

a-d, examples of volume-rendered LV annular, septal (from GCV and from AIV), and diagonal veins in the LVS. e, number of septal and/or diagonal LVS veins seen in patients. f, examples of CCTA images showing septal veins reaching the outflow tracts.

There was significant variability in the characteristics of the GCV-AIV transition region. The GCV could either reach the proximity of the left main coronary artery (LMCA) bifurcation and make an abrupt angle there, to become the AIV, or could cut diagonally in a more gradual transition. The GCV-AIV angle could be measured in two planes. From a left lateral view, as the GCV wraps around the mitral annulus as a basal structure, it goes deep towards the LMCA, and makes an angle upward towards the LV anterior wall. (Figure 7a). This angulation could be seen in 41 of 52 patients (79%) and could be seen in either a left lateral (or steep LAO) view or posteroanterior view, and it measured 133°±14° (Figure 7a). From a frontal plane, the GCV-AIV angulation was present in all 52 patients (Figure 7b and c) and could be visualized best in an superior view (Figure 7b). In 16 of these 52 patients (31%), this angle was closer to the left main coronary artery (LMCA) bifurcation, and measured 88°±13° (Figure 7b first panel and second panel, top 2 images). In 36 of the 52 patients (69%) the angle was further away from the bifurcation and a smaller angulation was formed, angulation 133°±12°, p≤0.001 (Figure 7B third panel and second panel, bottom 2 images).

These angles had fluoroscopic correlates, best visualized in the LAO caudal projection (see Figure 4e and 4k -examples of angled GCV-AIV junction-, versus Figure 2h and 2k -non angled).

The number of veins visualized draining the LVS region in each patient varied. However, in all patients at least one LVS branch was present (Figure 8a, b, c and d). Overall, tributary branches from both GCV and proximal AIV drain the LVS, and were either septal, diagonal or both, 2.3±1.2 veins (range 1 to 5). In 22 of 52 (42%) patients both septal and diagonal LVS veins were visualized draining the LVS, in 28 of 52 (54%) patients only septal veins and in 2 of 52 (4%) patients only diagonal veins were seen (Figure 8e, first panel). Septal LVS veins were more commonly visualized than diagonal veins, 50 of 52 vs 24 of 52 patients. The overall number of septal veins seen was 1.7±0.8 veins (range 1 to 4). Twenty three of 50 (46%) patients had 1 septal, 21 of 50 (42%) had 2 septals, 4 of 50 (0.06%) had 3 septals and 2 of 50 (0.04%) had 4 septals (Figure 8e, second panel). The overall number of diagonal veins seen was 1.5±0.5 veins (range 1 to 2) (Figure 8d). In 39 of 52 (75%) patients, some septal veins were seen reaching the outflow tracts, LVOT and RVOT, and adjacent area (Figure 8f). In 20 of 39 (51%) patients veins reached the lateral LVOT, in 9 of 39 (23%) patients veins reached the posterior wall of the RVOT, in 7 of 39 (7%) patients the region between the RVOT and LVOT and in 3 of 39 (8%) patients veins reached the region posterior to the LVOT (analogous to retroaortic veins described above, Figures 8a and b).

A LVA vein was seen in 21 of 50 (42%) patients. The LV annular vein (LVA) drains in the GCV and runs along the mitral annulus all the way to the aortomitral continuity (Figure 8a, Supplemental figure 2f and h).

Discussion

In this study, we used a systematic approach to define LVS veins angiographically in several fluoroscopic projections, combined them with 3D maps of the underlying RVOT, LVOT, aorta and AIV, to display LVS veins in their 3D context. Key findings include: 1) a consistent sequence of veins draining the LVS: annular, septal veins, and diagonal veins; 2) common intervenous communications between LVS veins; 3) presence of retroartic, atrial, retropulmonary vein drainage; 4) a range of GCV-AIV angles that have relevance to ease of cannulation of the AIV; 5) pre-procedure venous-phased CTA can provide valuable information of the individual anatomy.

Ventricular arrythmias arising in the LVS are one of the most technically challenging ones to treat. Patients often undergo multiple procedures and the incidence of recurrence is high. VEA is safe and offers a significant long-term effective treatment for patients with recurrent VAs.¹⁴ A detailed understanding of the venous anatomy of the LVS is critical for VEA to be successful and reproducible, and the 3-dimensional course of LVS veins and its venographic correlates are particularly challenging. This is the first study where a detailed description of the LVS venous return is done using intraprocedural venograms and CTA. Previous studies have described the human coronary venous return and their local anatomic correlates using either whole human hearts or imaging studies but the LVS area, particularly its venous drainage, was not included.^{8–10, 15–17} Despite the variability, we found common anatomical patterns among patients that are useful to know and will aid in the successful execution of LVS VEA.

The relevance of LAO caudal projection

Angiographic images of LVS veins are challenging due to foreshortening and overlap. Most previous reports contain RAO views,^11–13 which are adequate for LVS septal veins arising from the AIV, but RAO foreshortens the GCV as it wraps around the mitral annulus towards the LVS, as well as LVA vein. While RAO is useful to assess retroaortic vs retropulmonary vein courses, it has limited utility for vein selection. The LAO caudal is uniquely suited to display all LVS veins in their totality. The caudal angulation has to be steep enough to display the AIV in an elongated fashion. It is only then that the full spectrum of LVS veins can be displayed at once.

GCV-AIV transition

Angulations in the GCV-AIV transition have previously been measured.⁹ For the electrophysiologist attempting to reach the LVS area through the GCV or AIV this is important because a steep angle at the GCV-AIV transition difficults cannulation with large or stiff multipolar catheters. In our experience, sharply angled GCV-AIV transitions can make cannulation with a DecaNav (Biosense-Webster) catheter difficult, and advancement of a sub-selector LIMA or JR4 into the proximal AIV can be unstable and counterproductive when trying to direct their tip towards septal branches.

LVA vein

Previous reports have not specifcally discrimated LVA vein from LV septal veins, and labeled both collectively as “LV communicating vein”¹¹ or “septal perforators”. Although there is considerable anatomical variability and overlap, it is important to clearly differentiate the LVA vein as one that arises from the GCV at the mitral annulus, before reaching the interventricular groove. Its course towards the aortomitral continuity makes it the only LVS vein that could a priori be used to target arrhythmias from this region. Because it is relatively larger than other LVS veins, it is also relatively easier to cannulate. However, only 6/53 patients had LVA veins targeted for VEA, since it more commonly contained atrial signals and atrial branches (towards the anterior left atrial wall, as we had previously described¹⁸). When correlated with neighboring structures, the LVA had a coursed posterior to the LVOT and had retroaortic collaterals.

Septal LVS veins

LVS septal veins were the most commonly used veins for VEA. When arising at the GCV-AIV junction, the first septal could contain atrial signals and have a retroaortic directionality, overlapping characteristics with the LVA vein. Most commony, the LVS septal had a course that filled the space anterior and septal to the LMCA, and between the GCV-AIV angle and the underlying LVS muscle before becoming strictly “perforators” as previously reported.^{12, 13} Veins in the space between LVOT and RVOT were usually tributaries of the LVS septals. Given their location, they were the most common targeted vein for VEA, which makes understanding their anatomy crucial for reproducibility of the technique.

Value of vCTA

Although not routinely performed, we show that major branches of the GCV-AIV and their angulation can be outlined preprocedurally with vCTA.

Study limitations

This study did not fully characterize the coronary venous system using CTA as it has previously been done.^{9, 10} We focused on the tributary branches of the coronary venous system that drain the LVS area. Intraprocedural rotational angiography was not performed. Multipolar signals were collected from LVS veins with a 2F catheter; while we did not encounter complications from it, other tools such as Visionwire® (Biotronik, Lake Oswego, OR) can be used as well.

Conclusion

A comprehensive atlas of LVS veins is provided, along with descriptions of the significant anatomical variability, and the relationships between LVS veins and neighboring structures including the aorta, right ventricular outflow tract, and coronary arteries. Previously vague or ambiguous nomenclature is clarified, and the potential value of pre-procedure vCTA is shown.