Origin of the sinoatrial and atrioventricular nodal arteries in South Indians: an angiographic study

Abstracts

FUNDAMENTO: Estudar o suprimento arterial do sistema condutor e sua correlação com a dominância das artérias coronárias em população do sul da Índia. OBJETIVO: Determinar angiograficamente as origens da artéria do nó sinoatrial (AnSA) e artéria do nó atrioventricular (AnAV) em indianos. MÉTODOS: O ESTudo incluiu 300 pacientes consecutivos (114 do sexo feminino e 186 do sexo masculino; idade média, 55 anos), habitantes da região costeira ao sul da Índia, submetidos a cineangiocoronariografia devido a sintomas como dor no peito, angina pectoris ou teste ergométrico positivo. As angiografias incluíram ambas as artérias coronárias (direita e esquerda) em posição oblíqua anterior direita e esquerda. A origem da AnSA e AnAV a partir das artérias coronárias foi observada e correlacionada à dominância arterial. RESULTADOS: O nó SA (sinoatrial) recebeu suprimento pela artéria coronária direita (ACD) em 53% dos casos, pelo ramo circunflexo (Cx) da artéria coronária esquerda (ACE) em 42,66% dos casos, e em 4,33% dos casos esse nó foi irrigado por ambas as artérias coronárias. O nó AV (atrioventricular) também recebeu suprimento sanguíneo com mais frequência da ACD (72,33% dos casos) do que do ramo Cx da ACE (27,66%). Surpreendentemente, em nenhum caso este nó recebeu suprimento de ambas as artérias coronárias. CONCLUSÃO: Os Resultados do presente estudo podem auxiliar os cirurgiões cardíacos, sobretudo em cirurgias relacionadas a valvopatias, devido à franca proximidade entre os ramos nodais e o complexo valvar.

Artérias coronárias; nó sinoatrial; nó atrioventricular; angiografia

FUNDAMENTO: Estudiar el suministro arterial del sistema conductor y su correlación con la dominancia de las arterias coronarias en población del Sur de la India. OBJETIVO: Determinar angiográficamente los orígenes de la arteria del nódulo sinusal (AnSA) y la arteria del nódulo atrioventricular (AnAV) en indios. MÉTODOS: El estudio incluyó 300 pacientes consecutivos (114 del sexo femenino y 186 del sexo masculino; edad promedio, 55 años), habitantes de la región costera al Sur de la India, sometidos a cineangiocoronariografía debido a síntomas como dolor en el pecho, angina pectoris o test ergométrico positivo. Las angiografías incluyeron ambas arterias coronarias (derecha e izquierda) en posición oblicua anterior derecha e izquierda. El origen de la AnSA y AnAV a partir de las arterias coronarias se observó y se correlacionó con la dominancia arterial. RESULTADOS: El nódulo SA (sinusal) recibió suministro por la arteria coronaria derecha (ACD) en el 53% de los casos, por la rama circunfleja (Cx) de la arteria coronaria izquierda (ACI) en el 42,66% de los casos, y en el 4,33% de los casos este nódulo fue irrigado por ambas arterias coronarias. El nódulo AV (atrioventricular) también recibió suministro sanguíneo con más frecuencia de la ACD (72,33% de los casos) que la rama Cx de la ACI (27,66%). Sorprendentemente, en ningún caso este nódulo recibió suministro de ambas arterias coronarias. CONCLUSIÓN: Los resultados del presente estudio pueden auxiliar a los cirujanos cardíacos, sobre todo en cirugías relacionadas a valvulopatías, debido a la franca proximidad entre las ramas nodales y el complejo valvular.

Arterias coronarias; nódulo sinusal; nódulo atrioventricular; angiografía

ORIGINAL ARTICLE

^IDepartamento de Anatomia - Centro de Ciências Básicas, Kasturba Medical College, Bejai, Mangalore, Karnataka - India

^IIDepartamento de Anatomia - Father Muller Medical College, Father Muller Road, Kankanady, Mangalore, Índia

^IIIDepartamento de Fisiologia - Centro de Ciências Básicas, Kasturba Medical College, Bejai, Mangalore, Karnataka - India

Mailing address

SUMMARY

BACKGROUND: To study the arterial supply of the conducting system and its correlation with the dominance of the coronary arteries in the South Indian population.

OBJECTIVE: To determine angiographically the origins of the sinoatrial nodal artery (SAna) and atrioventricular nodal artery (AVna) in Indians.

METHODS: The study included 300 consecutive patients (114 females, 186 males; mean age, 55 years) living in the southern coastal region of India, who underwent coronary angiography either for the symptoms of chest pain, angina pectoris or positive Treadmill Test. The angiograms contained both coronary arteries (right and left) in the right and left anterior oblique position. The origin of SAna and AVna from the coronary arteries was observed and correlated with the arterial dominance.

RESULTS: The SA (sinoatrial) node was supplied by the right coronary artery (RCA) in 53% of the cases, by the circumflex (Cx) branch of left coronary artery (LCA) in 42.66%, and by both coronary arteries in 4.33% of cases. The AV (atrioventricular) node was also more often supplied by the RCA (72.33% of cases) than by the Cx branch of the LCA (27.66%), and surprisingly in none of the cases was this node supplied by both coronary arteries.

CONCLUSION: The results of the present study may help cardiac surgeons, particularly in surgeries related to certain valvular disorders, due to the proximity of the nodal branches to the valve complex.

Key words: Coronary vessels; sinoatrial node; atrioventricular node; angiography.

Introduction

Anterior atrial branches of the RCA are arranged in anterior, lateral and posterior groups to supply the corresponding surfaces of the right atrium. One important atrial branch is the SA nodal artery which is usually the second branch of the RCA and supplies the SA node in 65% of the cases; in the remaining 35%, the SA node is supplied by a branch of the Cx artery¹. According to April, SAna also arises from Kugel's artery (when an atrial branch of the circumflex communicates with the similar branch of the right coronary artery, such an anastomotic branch is called Kugel's artery)². The arterial supply of the AV node arose in 80% of the hearts from the RCA in the posterior atrioventricular sulcus at a point just beyond the origin of the posterior interventricular artery. In 20% of the hearts the AV node arose from the terminal part of the Cx at the crux of the heart [1]. The study on the arterial supply of the SA node will benefit clinical knowledge and surgical procedures as well as methods of cardiac examination and treatment. Proper precautions should be taken to preserve the main arterial supply to the SA node during surgery³.

Sokolov and Varegin⁴, Krupa⁵, DiDio et al⁶, Sow et al⁷ and Onciu et al⁸ studied the origin of SAna. Krupa⁹, Sow et al¹⁰, Arid et al¹¹ studied the origin of AVna. Hutchinson¹, Vieweg et al¹², Futami et al¹³ studied the origin of both SAna and AVna. We studied the origin of both SAna and AVna and also the coronary dominance with the help of coronary arteriography.

The aim of the present study was to identify the origin of SAna and AVna from different coronary arteries and to determine the correlation of both arteries above with the artery of dominance. In this study, angiographic analysis of the coronary arteries was the preferred method of study as it is most commonly used in today's clinical setting and such a study would be of more clinical significance than studies done on cadaver hearts.

Methods

The present study included 300 consecutive patients (114 females, 186 males; mean age, 55 years) living in the southern costal region of India, who underwent coronary angiography either for the symptoms of chest pain, angina pectoris or positive Treadmill Test at Kasturba Medical College, Mangalore, India. The coronary angiograms selected were recorded on CDs. These were then studied using Cardiac SoftView (a software program to read coronary angiogram). The angiograms contained both coronary arteries (right and left) in various views, but to visualize the AVna and the SAna from either of the two coronary arteries, the preferred projections that were used here were the left anterior oblique view of the right coronary artery and the right anterior oblique view of the left coronary artery. The SAna when arising from the RCA can be recognized as its second branch after the conus artery that runs dorsally and extends over the upper portion of the atrial septum to terminate in the region of the ostium of the superior vena cava after arching laterally in front of the later. When the SAna is supplied by the circumflex branch of the LCA it passes to the right over the left auricle and reaches the SA node after encircling the superior vena cava.

The AVna is usually seen as a branch of the dominant artery. The artery arises from the crux, and is said to be a branch of the first posterior interventricular artery. It is consistent with the inverted U turn that is seen at the crux in the case of the RCA and a smooth curve seen at the crux in the case of the circumflex branch of the left coronary artery.

The following parameters were chosen for the study:

(i) Origin of the posterior interventricular artery to determine the coronary dominance.

(ii) The origin of SAna and AVna from the coronary arteries.

(iii) The origin of the nodal arteries were then correlated with dominance

These parameters were then tabulated and analyzed.

Results

In the present study, 161 (53.66%) of our 300 patients had a right dominant coronary arterial system (posterior descending artery originating from the right coronary artery), 67 (22.33%) had a left dominant coronary arterial system (posterior descending artery originating from the left circumflex), and 72 (24%) showed codominance. The SA node was supplied by the RCA [Fig. 1] more frequently (53% of cases) than by the Cx branch of LCA [Fig. 2] (42.66%), and in 4.33% of the cases this node was supplied by both coronary arteries. The AV node was supplied by the RCA (72.33% of the cases) [Fig. 3] more frequently than by the Cx branch of the LCA (27.66%) [Fig. 4], and surprisingly in none of the cases was this node supplied by both coronary arteries [Table 1]. It was found that (i) in 35% of the cases both the SA and AV nodal arteries originated from the RCA, (ii) in 11% of the cases both the SA and AV nodal arteries originated from the Cx branch of LCA, and (iii) in 54% of the cases both the SA and AV nodal arteries originated from different coronary arteries [Table 2]. The AV nodal artery was a branch of the dominant artery in 71.66% of the cases [Table 3] in comparison to the SA nodal artery which was a branch of the dominant artery only in 36% of the cases [Table 4].The source of arterial supply of the SA node and AV node, as found by various authors and in the present study, is shown in Table 5.

Discussion

Hutchinson found that in 50% of the hearts, both the SA and AV nodes were supplied by branches of the right coronary artery. In 7%, both were supplied by branches from the left coronary artery¹.

The SAna of the coronary arteries is anatomically regarded as a significant artery since it is used as a landmark to identify the SA node, in addition to its clinical significance. Berdajs et al¹⁴ reported that the SAna crosses the superior posterior border of the interatrial septum in 54% of the cases. From these data they concluded that the risk for intraoperative damage to the sinus node artery during the superior transseptal approach to the mitral valve is high¹⁴. Berdajs et al¹⁵ studied the AVna by coronary angiogram; they found that the SAna originated from the RCA in 73% of the examined cases, and from the LCA in 27% of the cases. The left AVna was closely related to the mitral valve attachment, especially at the area of the left proximal part of the posterior leaflet. By comparing their data with the available literature, they reported that there is a high risk of intraoperative damage to the left AVna during manipulation of the mitral valve annulus fibrosus¹⁵. In the present study, only in 27.66% of the cases did the AVna originate from the LCA. In addition to being an excellent guide to the location of the sinoatrial node, the topic investigated demands further study due to its application in cardiac surgery³.

Nerantzis et al¹⁶ observed that the SAna played a major role in the blood supply of the atrial myocardium and atrial septum in the majority of the cases (59%). In 37% of the cases, the vessel supplying the SA node was not the main continuation of the SA nodal artery. In 22% of the cases, the SAna supplied the entire atrial myocardium, and in 19% the SAna supplied the right atrium and part of the atrial septum¹⁶.

A study by Bokeriya et al¹⁷ on the variations of the SAna and AVna showed 14 different variations of the SAna with regard to its connections with the anterior atrial sulcus and orifices of the superior vena cava, and they also identified 6 variants of the AVna with regard to its connections with the interventricular septum. The importance of these variations was stressed because any surgery on these arteries could damage the surrounding structures¹⁷.

Krupa⁵ published a study on SAna in human hearts, where he observed that the SAna arose as the anterior, intermediate and posterior atrial branches of both the RCA and LCA. In 51.7% of the hearts, the SAna forms an arterial circle at the base of the superior vena cava⁵. The origin of the SAna from the proximal portion or trunk of the LCA, was less frequent (12%±3.2) than from the Cx (30%±4.5) and neither sex nor race influenced the origin of Sana⁶.

Sow et al⁷ studied the SA node artery by injection-dissection and found that it was a solitary artery in 88.89% of cases and double in 11.11%, and the artery of origin was not influenced by coronary dominance. However, in the present study the AVna was a branch of the dominant artery in 71.66% of the cases. When it came from the RCA, the course of SAna varied greatly in relation to the site of origin - from either the atrial artery or from one of its collateral branches. When it came from the Cx its course was relatively uniform. These findings are especially important during certain stages of cardiac surgeries like atriotomies, surgical repair of valvular disorders and congenital malformations, which expose the SAna⁷. The origin of the SAna from both coronary arteries in our study (4.33%) was much less frequent than in the study conducted by Futami et al¹³, but the frequency of RCA origin of the AVna found by Futami et al¹³ was quite similar to that of the present study (72.33%). Not even in a single occasion did the AVna originate from both coronary arteries in the present study, in comparison to the 10% of cases found by Futami et al¹³.

Sokolov and Varegin⁴ investigated 60 heart preparations to observe the variation in the SAna. They reported that large atrial branches of RCA or LCA usually supply the SA node and showed some variations in the site of origin from the RCA and LCA. The SAna may arise from the right intermediate or right posterior atrial branches. In the LCA variant it can arise from the anterior left, posterior left or intermediate left atrial branches⁴. Abuin and Nieponice¹⁸ studied the origin of AVna in 20 hearts. They found that in 40% of these hearts Kugel's artery was supplying the AV node. The right descending superior artery supplied the AV node in 70% of the cases. These findings may be of major significance both in cardiology and in cardiovascular surgery¹⁸. Arid et al¹¹ aimed at studying the anatomical characteristics of the major arterial source of the AV node of 40 hearts by various anatomical and radiological techniques but they could only obtain results from 23 of them. They concluded that the most common atrial source of the AV node (21/23) was the RCA, but numerous variations in origin and topography were found¹¹.

Kyriakidis et al¹⁹ mentioned that the knowledge of the course of the arteries irrigating the sinus node is important for a better understanding of the cardiac physiology and from a surgical point of view. They studied the arterial blood supply to the sinus node area in 309 consecutive patients undergoing coronary arteriography. Of the sinus node arteries arising from the right coronary artery - the right sinus node arteries, the majority (179) arose proximally 1 to 3 cm from the aortic ostium, passed across the anteromedial wall of the right atrium, and penetrated the atrial septum below the interatrial bundle. In 87 of the 119 patients in whom the SAna arose from the left Cx, it arose from the proximal portion of the left Cx and coursed through the anterior branch of the interatrial muscle bundle and then through the bundle itself¹⁹.

Conclusion

In our study, the origin of the SAna was mainly from the RCA (53%) and LCA (42.66%); only in 4.33% cases was the SAna supplied by both coronary arteries. The AVna originated either from the RCA (72.33%) or from the Cx branch of LCA (27.66%). However, more angiographic studies of coronary arteries in different races should be performed to provide conclusive data on the origin of the SAna and AVna. The results of the present study may help cardiac surgeons, particularly during surgical correction of certain valvular disorders and congenital malformations of the coronary arteries.

Potential Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Sources of Funding

There were no external funding sources for this study.

Study Association

This study is not associated with any post-graduation program.

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Origin of the sinoatrial and atrioventricular nodal arteries in South Indians: an angiographic study

Lakshmi Ramanathan^I; Prakash Shetty^II; Soubhagya R. Nayak^I; Ashwin Krishnamurthy^I; Ganesh K. Chettiar^I; Annamalai Chockalingam^III

Publication Dates

• Publication in this collection
  20 July 2009
• Date of issue
  May 2009

History

• Received
  02 Jan 2008
• Reviewed
  14 Mar 2008
• Accepted
  14 Mar 2008