ABSTRACT
Background
The coronary atrial circulation is the network of vessels that supply blood to the atria, originating from the left circumflex and right coronary arteries. Current descriptions of this arterial system are based on anatomical studies with a limited number of patients, predominantly male. In addition, there is a lack of consensus its angiographic nomenclature.
Aims
This study aimed to evaluate the anatomical variations of coronary atrial branches (CAB) and investigate sex‐related differences in their distribution.
Methods
Consecutive patients with ST‐elevation myocardial infarction who underwent primary PCI at a tertiary center between 2004 and 2013 were included. Angiographic anatomy of all visible CAB on index coronary angiography was systematically evaluated following a stepwise method, including type of branch; coronary artery of origin; segment of origin, branch course, and atrial dominancy. Specific differences between both sexes were analyzed.
Results
A total of 998 patients (age 61 ± 12, 79% male) were included. The sinus node artery was the dominant CAB in 916 (93%), originating in 37% from distal coronary segments. Different CAB anatomical patterns were identified in both sexes. Compared to females, males presented a higher prevalence of left‐sided CAB (left circumflex CAB 459 [58%] vs. 96 [45%], p < 0.001; sigma‐shaped CAB 267 [30%] vs. 39 [21%], p = 0.003) and of a left‐balanced atrial circulation pattern‐defined as the presence of at least two CAB originating from the LCx, with one of them being the dominant CAB—245 (31%) versus 45 (21%), p = 0.005.
Conclusions
This study provides a systematic approach to the angiographic evaluation of CAB. Sex‐related phenotypical differences of CAB distribution were found, with males presenting a higher presence of left‐sided CAB and a left‐balanced atrial circulation pattern.
Keywords: atrial coronary arteries, coronary artery anatomy, coronary artery disease
Abbreviations
- CAB
coronary atrial branch
- CAD
coronary artery disease
- LAD
left anterior descending
- LCx
left circumflex coronary artery
- MI
myocardial infarction
- PCI
percutaneous coronary intervention
- RCA
right coronary artery
- SNA
sinus node artery
- STEMI
ST‐segment elevation myocardial infarction
1. Introduction
The coronary atrial circulation, often overlooked, comprises a network of coronary vessels that supply blood to the atria. These vessels originate from the right coronary artery (RCA) and from the left circumflex artery (LCx). The first coronary atrial branch (CAB), described in 1907, was the sinus node artery (SNA), coinciding with the description of the autonomic nervous system structure. Traditionally, it has been stated that the SNA predominantly arises (2/3 of cases) from the RCA, and the remainder from the left coronary circulation, with infrequent descriptions of bilateral supply [1, 2]. This vessel has been described as an individualized anatomical entity, usually being considered the most proximal vessel originating from a given coronary artery [1, 2].
Modern descriptions of the atrial arterial system still rely on anatomical studies conducted contemporarily to the original description of the first CAB. These studies had a limited sample size and predominantly involved male subjects, possible neglecting variations between sexes [1, 2, 3].
The relevance of CABs was initially tied to the need for their preservation during cardiac surgery to avoid postoperative supraventricular cardiac arrythmias [1, 2]. Recently, atrial ischemia and coronary artery disease (CAD) affecting the atrial circulation have been strongly related to the development of atrial fibrillation and other atrial arrythmias, contributing to a poor overall patient prognosis [1, 4, 5]. Additionally, several studies have also underscored the impact of atrial branch occlusion during acute myocardial infarction (MI) and its relationship with future arrhythmic events and deleterious atrial remodeling [6, 7, 8].
Recognizing the clinical importance of CABs and their inherent variability emphasizes the necessity of establishing a standardized nomenclature and classification system to facilitate their comprehensive characterization. This effort will help consolidate existing knowledge and promote uniform and representative research in this field, which has been described as understudied since its initial characterization [1, 2, 3].
With this study, we aim to provide a reproducible and systematic angiographic characterization of CABs, involving a cohort of patients presenting with acute MI who underwent emergent coronary angiography. Furthermore, we analyzed the presence of specific anatomical patterns of CAB in both sexes [3, 6].
2. Methods
2.1. Study Population
The study population has been previously described [7, 8]. Briefly, patients with ST‐elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (PCI) at the Leiden University Medical Center between 2004 and 2013 were considered for inclusion. Of them, only those in which the culprit lesion was located either at the RCA or the LCx, vessels from which all CAB originate, were included for the purpose of a previous study [7]. Exclusion criteria comprised previous coronary artery bypass grafting and absence/uninterpretable coronary angiograms from the index procedure. The intervention was performed according to current guidelines at the time and patients were followed up according to the institutional care track for STEMI [9]. The study protocol was carried out in accordance with the ethical principles for medical research involving human subjects established by the Declaration of Helsinki. The institutional review board approved this retrospective analysis of clinically acquired data and waived the need for patient written informed consent.
2.2. Angiographic Evaluation
All coronary angiograms performed during the index procedure were retrospectively evaluated by two experienced interventional cardiologists. Coronary angiograms were obtained in a protocolized fashion, which included, at least four standard angiographic projections for the left coronary artery (left anterior oblique 30°–45°—cranial 25°–35°; left anterior oblique 40°–50°—caudal 25°–40°; right anterior oblique 30°–45°—caudal 30°–40° and right anterior oblique 30°–40°—cranial 35°–45°) and, at least, three projections for the RCA (left anterior oblique 45°–60°; left anterior oblique 45°–60°—cranial 35°–45°and right anterior oblique 30°–45°). Image intensification was used at discretion of the operator. The dominant coronary artery was defined as the artery giving off the posterior descending artery, characterized as left (when supplied by the LCx), right (when supplied by the RCA), or codominant (posterior descending artery arising from the RCA and large posterolateral branch arising from the Lcx or both RCA and LCx branching off a posterior descending artery. Coronary artery segments were defined according to established frameworks [10].
2.3. CABs Systematic Characterization
The angiographic anatomy of all visible CAB was systematically evaluated following a stepwise method: (1) type of CAB; (2) coronary artery of origin; (3) coronary segment of origin; (4) CAB development and course. Both baseline and final coronary angiograms, after completion of the PCI procedure, were thoroughly evaluated following to this method to prevent the overlooking of CABs either due to proximal occlusion of the donor vessel or resulting from stent implantation (e.g., ostial occlusion, no‐reflow phenomenon, etc.).
2.3.1. CAB Definitions
The SNA was defined as the artery supplying the sinoatrial node, regardless of the coronary artery of origin, contrary to previous descriptions [3, 6]. This option was adopted with the understanding that the SNA does not necessarily have to be the most proximal CAB emerging from a given coronary artery, and that several of described CABs can function as the SNA for any given patient. Criteria for angiographic identification of the SNA were (1) a vessel extending to the region of the right atrium‐superior vena cava junction and (2) a distal branching system encircling the superior vena cava, either in a clockwise/counterclockwise manner, or bifurcated in two branches [11]. The right anterior and right intermediate atrial branches were defined as well‐defined atrial branches arising from the proximal or mid segment of the RCA. Minor RCA atrial branches were defined as small caliber atrial branches emerging from the RCA along the atrioventricular groove supplying the right atrial wall. The atrioventricular node artery was defined as the branch supplying the atrioventricular node area [3, 6]. The left anterior atrial branch was defined as a CAB arising from the proximal LCx and coursing upward along the left atrium [3, 6]. The s‐shaped atrial branch was defined as a CAB arising from the LCx and coursing along the posterolateral wall of the left atrium [6, 12]. The left circumflex atrial branch was defined as a CAB arising either from the LCx or other atrial branch (frequently the s‐shaped atrial branch) coursing along the lower margin of the left atrium [3, 6]. A schematic representation of the CAB is provided in Figure 1 with angiographic examples in Figure 2 [6].
Figure 1.
Schematic representation of fluoroscopic anatomy of coronary atrial branches. All the aforementioned coronary atrial branches, except for the atrioventricular node artery, may supply the sinoatrial node. When they do, they are referred to as the sinus node artery for that particular patient. [Color figure can be viewed at wileyonlinelibrary.com]
Figure 2.
Angiographic examples of the coronary atrial branches types. Panel A: right anterior atrial branch (arrow). Panel B: right intermediate atrial branch. Panel C: minor right atrial branch. Panel D: atrioventricular node branch. Panel E: left anterior atrial branch. Panel F: left circumflex atrial branch. Panel G: sigma‐shaped atrial branch. [Color figure can be viewed at wileyonlinelibrary.com]
2.3.2. Coronary Atrial Dominance, Concordant Atrial/Ventricular Dominance, and Left‐Balanced Atrial Circulation
The dominant CAB was defined as the most developed CAB, irrespective of the type, based on visual estimation. Coronary atrial dominance, a concept previously described, was classified as right or left based on the coronary vessel (either RCA or LCx) giving rise to the dominant CAB [7]. Concordant atrial/ventricular dominance was considered when the dominant CAB emerged from the dominant coronary artery. A left‐balanced atrial circulation was defined by the presence of at least two CAB originating from the LCx, with one of them being the dominant CAB (Figure 3).
Figure 3.
Concordant coronary dominancy and left‐balanced atrial coronary system. Panel A: Concordant right dominancy: dominant right coronary artery (the posterior descending artery is marked with arrow heads), providing the dominant atrial branch, which is this case is the proximal sinoatrial branch acting as the sinus node artery (yellow head). Panel B: Concordant left dominancy: dominant left circumflex (posterior descending artery is marked with arrow heads), giving rise to the dominant atrial branch, which is this case is the sigma‐shaped atrial branch. Panel C: Left‐balanced coronary atrial system, in which a dominant left anterior atrial branch (yellow arrow), a sigma‐shaped branch (arrow heads), and a left circumflex atrial branch (asterisk) emerge from the left circumflex coronary artery. [Color figure can be viewed at wileyonlinelibrary.com]
2.4. Statistical Analysis
Continuous variables are presented as either means ± standard deviation or medians with interquartile range, as appropriate. Differences between continuous variables were assessed with the use of the unpaired Student t test for normally distributed variables and the Mann–Whitney U test for nonnormally distributed variables. Categorical variables were reported as frequencies and percentages and were analyzed using the χ 2 or Fischer exact test. All tests were two‐sided, and a p < 0.05 was considered statistically significant. Data were analyzed using Stata Statistical Software Package, Version 17.0 (StataCorp LP, College Station, Texas, USA).
3. Results
Within the cohort of 2604 patients referred for emergent coronary angiography due to STEMI, 998 patients (age 61 ± 12, 79% males) met the inclusion criteria, forming the study group. The main angiographic characteristics are detailed in Table 1. The analysis included a sex‐based division to explore potential anatomical differences.
Table 1.
Angiographic characterization of the coronary atrial circulation according to sex.
| Overall (N = 998) | Males (N = 785) | Females (N = 213) | p value | |
|---|---|---|---|---|
| Coronary dominance, n (%) | ||||
| Right dominance | 857 (96%) | 679 (96%) | 178 (95%) | 0.327 |
| Left dominance | 34 (4%) | 25 (3%) | 9 (5%) | |
| Co‐dominance | 6 (1%) | 6 (1%) | 0 (0%) | |
| Dominant CAB type, n (%) | ||||
| Sinus node artery | 916 (93%) | 724 (93%) | 192 (93%) | 0.912 |
| Others | 65 (7%) | 51 (7%) | 14 (7%) | |
| Dominant CAB vessel of origin, n (%) | ||||
| RCA | 543 (55%) | 420 (54%) | 123 (58%) | 0.228 |
| LCx | 451 (45%) | 363 (46%) | 88 (42%) | |
| Left‐balanced atrial circulation, n(%) | 290 (29%) | 245 (31%) | 45 (21%) | 0.005 |
| Concordant atrial/ventricular coronary dominance, n(%) | 482 (48%) | 378 (48%) | 104 (49%) | 0.827 |
| Sinus node artery features | ||||
| Originating from RCA, n (%) | 580 (59%) | 446 (57%) | 134 (64%) | 0.098 |
| Right anterior atrial branch | 342 (38%) | 264 (37%) | 78 (41%) | 0.262 |
| Right intermediate atrial branch | 174 (19%) | 134 (19%) | 40 (21%) | 0.443 |
| Posterolateral branch | 7 (1%) | 7 (1%) | 0 (0%) | 0.173 |
| Originating from LCx, n (%) | 441 (41%) | 334 (43%) | 77 (36%) | 0.098 |
| Left anterior branch | 229 (25%) | 179 (25%) | 50 (27%) | 0.676 |
| Sigma‐shaped branch | 149 (17%) | 129 (18%) | 20 (11%) | 0.014 |
| AV‐node artery features | ||||
| Originating from RCA, n (%) | 853 (94%) | 665 (94%) | 188 (95%) | 0.683 |
| Segment 3 | 58 (6%) | 48 (7%) | 10 (5%) | 0.370 |
| Segment 4 | 102 (11%) | 82 (12%) | 20 (19%) | 0.544 |
| Segment 16 | 691 (77%) | 533 (76%) | 158 (80%) | 0.230 |
| Originating from LCx, n (%) | 51 (6%) | 41 (6%) | 10 (5%) | 0.683 |
| Segment 14 | 22 (2%) | 17 (2%) | 5 (3%) | 0.929 |
| Segment 15 | 17 (2%) | 13 (2%) | 4 (2%) | 0.847 |
| Types of Atrial Branches, n (%) | ||||
| Minor right atrial arteries | 348 (35%) | 291 (37%) | 54 (27%) | 0.006 |
| Left anterior LCx atrial branch | 478 (48%) | 374 (48%) | 104 (48%) | 0.771 |
| Left circumflex atrial branch | 555 (56%) | 459 (58%) | 96 (45%) | < 0.001 |
| Sigma‐shaped LCx artery, | 267 (30%) | 228 (32%) | 39 (21%) | 0.003 |
Note: Values may not be added to the total in cases of marginal missing data.
Abbreviations: AV—atrioventricular; CAB—Coronary artery branch; CAC—coronary atrial circulation; LAD—left anterior descending coronary artery; LCx—Left circumflex coronary artery; RCA—Right coronary artery; SNA—Sinus node artery.
3.1. Coronary Dominance and CAB Characteristics
Right coronary dominance was observed in 857 (96%) patients, with equal distribution across genders. In addition, the SNA was predominantly the dominant CAB, arising equally from the RCA and the LCx. Concordant atrial/ventricular dominance was noted in 48% of patients, without any significant differences between sexes.
3.2. Sinus Node CAB Specific Features
The SNA originated from the RCA in 580 (59%) and from the LCx in 441 (41%) cases, with a slightly higher tendency for RCA origin in females (64% vs. 56%) and LCx origin in males (43% vs. 36%), though not statistically significant. The most common CAB acting as the SNA was the right anterior atrial branch (38%), followed by the left anterior atrial branch (25%). Interestingly, in 37% of cases, the SNA originated from a CAB emerging from nonproximal coronary segments (including a right intermediate atrial branch, posterolateral branch from the RCA, or a sigma‐shaped branch from the LCx).
The distribution of SNA types (Figure 4) was consistent between genders, except for the sigma‐shaped branch from the LCx, which was more commonly observed in males (18% vs. 10%; p = 0.014).
Figure 4.
Angiographic anatomical variants of the sinus node artery. Panel A: Right proximal sinoatrial branch (arrow) arising from the proximal right coronary artery (RCA). Panel B: Right intermediate sinoatrial branch (arrow) arising from the mid‐RCA branch. Panel C: atrial branch emerging from the distal posterolateral artery from the RCA (arrow). Panel D: left anterior atrial branch (arrow) arising from the proximal left circumflex artery (LCx). Panel E: sigma‐shaped atrial branch arising emerging from the LCx. [Color figure can be viewed at wileyonlinelibrary.com]
3.3. Other CAB Anatomic Features
The AV‐node artery originated predominantly from the RCA (96%), specifically from the proximal right posterolateral branch (77%), with no significant sex‐based differences. In addition, minor right atrial branches were identified in 35% of patients, with a higher prevalence in males (37% vs. 27%, p = 0.006).
3.4. Gender Differences in Atrial Circulation Patterns
Males had a statistically higher prevalence of left‐sided CABs compared to females. Specifically, the left circumflex atrial branch was present in 58% males versus 45% females (p < 0.001), and the sigma‐shaped atrial branch 30% males versus 21% females (p = 0.003). However, the left anterior circumflex artery distribution was consistent across genders.
A left‐balanced atrial circulation was present in 39% of the entire cohort, and was more common in males than in females (31% vs. 21%, p < 0.005), with no significant differences in dominant CAB type or atrial dominance.
4. Discussion
The main findings of the present study are (1) a systematic evaluation of the CAB angiographic anatomy results in the identification of six well‐defined CAB subtypes: right anterior atrial branch, right intermediate atrial branch, AV‐node artery, left anterior atrial branch, LCx atrial branch, and sigma‐shaped atrial branch; (2) the most common dominant CAB is the SNA; (3) the most frequent CAB acting as the SNA is the right anterior atrial branch, accounting for 38% of the cases; (4) the SNA emerged from nonproximal coronary segments in 37% of cases; (5) Concordant atrial and ventricular dominance was present in < 50% of the cases; (6) there are gender‐specific differences in atrial circulation patterns, with males presenting more often left‐sided CAB and a left‐balanced atrial circulation.
Our study introduces a comprehensive and reproducible method for the angiographic evaluation of CAB. This systematic approach allows for detailed analyses of the coronary artery of origin, segment of origin, branch course, and atrial dominancy. The recent description of the clinical relevance of the coronary atrial circulation in several scenarios underscore the importance of a detailed and systematic evaluation to understand the anatomy of CAB, which has been understudied until now [6, 7, 8]. This method not only improves the homogeneity of CAG identification and nomenclature, but also facilitates the comparison of CAB anatomy across different populations and studies.
In the present study, the dominant CAB was the SNA in the majority of cases (93%), with a significant proportion of them (37%) originating from distal coronary segments (in four cases even originating from the posterolateral branch of the RCA). These findings contrast with traditional anatomical descriptions, which attribute the SNA to proximal coronary segments exclusively [13, 14]. We found as well significant interpatient variability in SNA types, identifying five possible branches functioning as the SNA, three originating from the RCA and two from the LCx. It is important to highlight that the blood supply to the sinus node area can be provided by different anatomical subtypes of atrial arteries, whose origins can also vary. Therefore, we believe that the nomenclature should include additional information about the specific subtype of atrial artery performing this function. There are potential clinical implications supporting this proposal. First, as demonstrated in this study, the SNA artery (regardless of its origin) is the dominant CAB in 93% of cases. It has been shown that alterations in coronary flow in the dominant CAB (responsible for supplying a larger area of atrial myocardium) in patients with STEMI are associated with adverse anatomical and functional remodeling of the left atrium [8, 15, 16, 17]. Second, recognizing these anatomical variants is crucial for various interventional or surgical procedures, where damage to this artery could impact the anatomical and functional integrity of the atrium. Some of these procedures include atrial fibrillation ablation, cardiac surgeries with access through the right atrium, or mitral surgery via septal access [18, 19].
Our analysis revealed significant sex‐related differences in CAB anatomical patterns. Males exhibited a higher prevalence of left‐sided CAB and a left‐balanced atrial circulation pattern. Specifically, males presented more often a left circumflex CAB and a sigma‐shaped LCx CAB. Of note, atrial branch dominancy was concordant with coronary dominancy only in half of the cases, a lack of correlation that is consistent between sexes. The potential clinical implications of these findings are yet to be elucidated, but awareness of these anatomical differences can play an important role in, for instance, minimizing complications related to atrial blood supply disruption during cardiac surgery or cardiac ablation procedures for the treatment of atrial arrhythmias. The identified sex‐related phenotypical differences in CAB distribution have significant implications for future research and clinical practice. These differences should be considered in the design and analysis of future studies investigating CAB and related CADs.
Several limitations should be acknowledged. The retrospective nature of the study and the predominance of male subjects may limit the generalizability of the findings. Additionally, patients with STEMI not involving the left anterior descending artery were not included in the original cohort, which could introduce selection bias. Up to 11% of the patients had a prior MI, potentially leading to previously chronically occluded atrial branches in either the past or index procedure. This may theoretically prevent a complete angiographic evaluation of the CAB. Although this cohort is the most representative described to date, there is still a need to include more female participants in future studies, as they constituted only 21% of the included participants.
5. Conclusions
The presented study introduces a systematic approach to evaluating CAB. The SNA is the most common dominant CAB, often originating from distal coronary segments. Males exhibit a higher prevalence of left‐sided CAB and a left‐balanced atrial circulation pattern, emphasizing the importance of sex‐specific anatomical considerations.
Conflicts of Interest
The Department of Cardiology of the Leiden University Medical Center unrestricted research grants from Abbott Vascular, Bayer, Bioventrix, Biotronik, Boston Scientific, Edwards Lifesciences, GE Healthcare, and Medtronic. Dr. JM. Montero‐Cabezas received speaker fees from Penumbra Inc. and research funds from Shockwave Medical. All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.