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Sinoatrial node artery arising from posterolateral branch of right coronary artery: definition by screening consecutive 1500 coronary angiographies/Sag koroner arter posterolateral dalindan cikan sinoatriyal nod arteri: Ardisik 1500 koroner anjiyografi taramasi ile tanimlama.

ABSTRACT

Objective: Sinoatrial node (SAN) artery originates from proximal segment of right coronary artery (RCA) or from left circumflex artery. Sinoatrial node artery artery originating from posterolateral (PL) branch of RCA is very rare. Only several cases have been reported. The study was performed to seek the frequency of this variation, evaluate clinical relevance, and describe electrocardiographic, angiographic characteristics of patients.

Methods: Consecutive 1500 coronary angiography were screened to detect specifically SAN artery originating from PL branch of RCA. Patients with this variation were followed-up for one year regarding the arrhythmic events.

Results: The origin of SAN artery was proximal RCA in 1280 (85%), circumflex artery in 208 (14%), and PL branch of RCA in 12 (0.8%) patients (8 male, 4 female, mean age 64 [+ or -] 9 years). There was no history of arrhythmia in all patients. One patient presented with atrioventricular block. Indications of angiography were stable angina in 5, unstable angina in 5, and acute myocardial infarction in 2 patients. The patient with inferior myocardial infarction due to RCA total occlusion did not develop bradycardia or conduction defect. In four patients (33%) there was another artery originating from proximal RCA, ending at same territory with the variant artery suggesting dual blood supply. During one-year follow-up none of the patients experienced arrhythmic event.

Conclusions: Sinoatrial node artery originating from distal RCA is very rare. This variation, even in patients with severe RCA disease is not associated with severe arrhythmia. Dual blood supply may be a protective factor in this subgroup of patients from arrhythmic events. To be aware of the origin and course of variant SAN artery may provide safe approach to interventional cardiologist and cardiac surgeon during percutaneous and surgical coronary and atrial interventions. (Anadolu Kardiyol Derg 2009; 9: 481-5)

Key words: Sinoatrial node artery, coronary artery disease, coronary angiography

OZET

Amac: Sinoatriyal nod (SAN) arteri sag koroner arter (SKA) proksimal segmenti ya da sol sirkumfleks arterden cikar. Sag koroner arterin posterolateral dalindan (PL) cikan SAN arteri oldukca nadirdir. Bu gune kadar sadece bir kac olguda saptanmistir. Arastirma bu varyasyonun sikligini saptamak, klinik onemini degerlendirmek ve bu varyasyona sahip hastalarin elektrokardiyografik, anjiyografik ozelliklerini tanimlamak amaciyla planlanmistir.

Yontemler: Ardisik 1500 koroner anjiyografi ozellikle SKA PL dalindan cikan SAN arterini tespit etmek amaciyla tarandi. Bu varyasyona sahip hastalar aritmik olaylar acisindan bir yil takip edildi.

Bulgular: Sinoatriyal nod arteri cikis noktasi 1280 hastada (%85) proksimal SKA, 208 hastada (%14) sirkumfleks arter ve 12 hastada (%0.8) SKA PL dali olarak saptandi (8 erkek, 4 kadin, ort yas 64 [+ or -] 9 yil). Hastalarin hicbirinde daha once aritmi hikayesi yoktu. Bir hastada AV tam blok mevcuttu. Koroner anjiyografi endikasyonlari 5 hastada kararli angina, 5 hastada kararsiz angina ve 2 hastada akut miyokard infarktusuydu. Sag koroner arteri tam tikali olan alt duvar infarktuslu hastada bradikardi ya da ileti kusuru gelismedi. Dort hastada (%33) proksimal SKAden cikan, varyant SAN ile ayni bolgede sonlanan ve bu nedenle ikili kanlanmayi dusunduren ikinci bir arter mevcuttu. Bir yillik takiplerde hicbir hastada aritmik olay gelismedi.

Sonuc: Sag koroner arter distal segmentinden cikan SAN arteri oldukca nadirdir. Bu varyasyon ciddi SKA darligi olanlarda dahi ciddi aritmi ile beraber degildir. Ikili kanlanma bu alt grupta aritmik olaylardan koruyucu bir faktor olabilir. Sinuatriyal nod arterinin cikis noktasi ve seyrinin farkinda olmak girisimsel kardiyologlara ve kalp cerrahlarina perkutan koroner girisimler, aritmi tedavileri ve cerrahi atriyal islemlerde guvenli bir yaklasim saglayabilir. (Anadolu Kardiyol Derg 2009; 9:481-5)

Anahtar kelimeler: Sinoatriyal nod arteri, koroner arter hastaligi, koroner anjiyografi

Introduction

The origin, course, and number of the arteries ending in sinus node region are crucial during percutaneous coronary intervention as well as percutaneous or surgical atrial interventions. Anatomic variations in origin and blood supply pattern (e.g. single-dual supply) may also be related to various atrial, sinoatrial arrhythmias associated with coronary artery disease. Coronary angiography and postmortem studies have shown that the sinoatrial node (SAN) artery originates from proximal segment of the right coronary artery (RCA) in the majority (51-59%) of the patients, and from the left circumflex artery (35-42%) or from both in the remaining small part (1-6). In a necropsy study, classical anatomic dissection of 150 hearts has showed that SAN artery was most frequently a large atrial branch of the RCA (63%), arising at a mean distance of 1.2 cm (range 0.2-2.2 cm) from its beginning (7). Similarly in a computed tomography study SAN artery was originating from the proximal 40 mm of the RCA in 67 of 102 patients and from the proximal 35 mm of the left circumflex artery in 28 patients, and dual blood supply to the SAN has seen in six patients (8). Only several cases of SAN artery originating from distal RCA have been reported (8, 9). Coincidental observation of an artery originating from posterolateral (PL) branch of RCA and ending in the territory of sinus node in two patients led us to screen coronary angiographies in order to detect the frequency and clinical significance of this variation. Demographic, clinical, and angiographic characteristics of patients having variant SAN artery origin from PL branch of RCA were evaluated.

Methods

The study was performed as retrospective analysis of coronary angiographies and prospective clinical follow-ups of patients with variant artery. Two experienced cardiologists screened 1500 consecutive coronary angiographies, specifically to seek out the variant origin of SAN artery. Left anterior oblique (LAO) view with 60 degrees angle and right anterior oblique (RAO) view with 30 degrees angle have been used for imaging RCA. Left anterior oblique view with cranial angle has also been used as needed. Totally 12 patients with variant SAN artery have been detected. Demographic, clinical, electrocardiographic, and angiographic characteristics of the patients who have abnormal origin of SAN artery were recorded. Patients were followed-up every four months for one year concerning the cardiac and rhythmic events. The longer-term follow-ups are still continuing. The study was approved by the Institutional Review Board, and informed consents were received from patients.

Results

The origin of SAN artery was RCA in 1280 (85%), circumflex artery in 208 (14%), and PL branch of RCA in 12 patients (8 male, 4 female, mean age 64 [+ or -] 9 years). Accordingly, the frequency of this variation was 0.8% (12/1500). Demographic and clinical characteristics and angiographic images of the patients are presented in Table 1 and Figure 1-3. The patients were predominantly male (66%). There was no history of syncope, near syncope, dizziness, and palpitation during resting or exercise in all cases, except patient 11 who presented with acute coronary syndrome associated with atrioventricular (AV) complete block. He was admitted to hospital with AV complete block necessitating temporary pacemaker implantation. Right coronary artery was not the responsible artery for AV block since it had no any critical stenosis. Family histories of all patients were unremarkable regarding the sudden death, syncope, severe bradycardia, and permanent pacemaker implantation. The indications of coronary angiography were stable angina and/or positive treadmill test in 5 patients, unstable angina in 5, and acute myocardial infarction in 2 patients. Patient 5 presented with anterior myocardial infarction, and patient 9 with inferior myocardial infarction. Right coronary artery was totally occluded at midportion in the latter one, and even though there was no antegrade blood flow the rhythm was sinus rhythm with a rate of 60/min. In four patients coronary angiography revealed normal coronary arteries (patients 1, 3, 7, 12), and myocardial bridge in patient 3. One of these patients with normal coronary artery (patient 7) had also hypertrophic obstructive cardiomyopathy with an outflow tract gradient of 60 mmHg. Patient 8 had a patent left anterior descending artery stent that had been implanted 2 years ago.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

All cases were followed-up by outpatient clinic visits and electrocardiogram (ECG) recordings every four months for one year (mean follow-up 14 [+ or -] 2 months) and none of the patients showed any clinical or electrocardiographic manifestation of sinus node dysfunction, conduction abnormality, bradycardia, or arrhythmia. The anatomic course of the variant artery was similar in all patients except patient 7. In this patient, the course of variant artery initially was laterally in LAO view, and posterior in RAO view instead of towards high right atrium. The patient also had a second artery originating from the midportion of RCA ending at the same region with variant SAN artery. In four patients (33%) there was another smaller artery originating from proximal part of RCA, ending at the same territory with variant artery suggesting a dual blood supply (Fig. 4).

Discussion

The frequency of variant SAN artery arising from PL artery was found to be very rare (0.8%) with the current study. Interestingly, there were no any acute arrhythmic and clinical deleterious effects of this variant during presentation or long-term follow-ups. Almost all patients were in sinus rhythm without any sinoatrial arrhythmia.

With the advent of new percutaneous and surgical techniques used in the treatment of coronary artery disease, and supraventricular bradi-tachy-arrhythmias including atrial fibrillation, awareness of origin and routes of the atrial branches, particularly the sinoatrial nodal branches of coronary tree, have assumed great importance (10-12). Only a few cases of SAN artery originating from distal RCA have been described previously (8,9). Hutchinson (9) showed that in one of the 40 autopsy cases the SAN artery arose from the terminal part of the RCA, passed over the postero-lateral surface of the left atrium, between the left pulmonary veins and the left auricular appendage, and over the superior surface of the left atrium to the superior vena cava. Similarly, in a recent computerized tomography (CT) angiography study S-shaped SAN artery originating from the RCA distal to the origin of the PL artery has been detected in one of the 244 patients (0.4%) (8). Interestingly, in both cases this artery was coursing posteriorly around the posterior aspect of the coronary sinus and left atrium and then anteriorly, terminating precavally to supply the SAN.

These arteries initially might be thought as collateral vessels by any cardiologist, and possibly for this reason had not been reported frequently. However, these could not be collateral vessels because all of them originate exactly from the same site, follow identical route, and end almost at the same location consistent with sinus node region. There might be relation between coronary artery disease involving RCA proximal to origin of this artery, and atrial arrhythmias including sinus bradycardia, sinoatrial block, sick sinus syndrome, and even atrial fibrillation. However, for the time being, direct relationship could not be established according to findings of our study. Since only a small part of the study group had coronary artery disease, and most of the lesions were not flow limiting any comments on the relation between coronary artery disease and arrhythmia will be incorrect. Longer term follow-up with progression of coronary artery disease in those patients will show whether there is a relationship between coronary artery disease and atrial arrhythmias.

[FIGURE 4 OMITTED]

In four patients there was another smaller artery originating from the proximal part of the RCA ending at the same location where the variant SAN artery ends. It seems that, most likely due to dual blood supply and adequate flow compensation to the sinoatrial node through the second artery, complete occlusion of RCA did not result in sinoatrial block or severe bradycardia. Sinoatrial node artery artery frequently has been described as a solitary artery originating from RCA, or circumflex branch of the left coronary artery and/or from the trunk of the left coronary artery (1, 9, 10, 13). However, plausible existence of two branches in up to 11% of cases has been reported (14-16). In two recent studies, several branches (two or more branches) at much higher frequencies up to 54% of cases among Japanese individuals have been shown (11,12). Interestingly, in a Brazilian study (17), the frequency of two sinoatrial nodal branches has been found to be very low (6%) which suggests a variation associated with ethnic group origin.

This variant branch from the PL artery is most consistent with the SAN artery based its anatomic course on angiogram. However, without histopathological examination, it is obviously difficult to claim this artery is the SAN artery, or the sole artery supplying the sinoatrial node. It could also be right atrial or conal artery, yet the course and the high right atrial location of the distal end were similar to the normal end of SAN artery with normal origin. Unless necropsy examination is performed, this cannot be confirmed. Unfortunately, necropsy studies generally have been performed on limited number patients. For instance in a relatively large autopsy study which examined 150 hearts, there was no any patient having SAN artery originating from PL (7). This is likely due to the small number of cases and uncommon occurrence of this variation as described in our study. However, selective coronary angiography may also fail to show the aortic origin of primary or synchronous SAN arteries with two or three projections of coronary angiography in identifying precise arterial supply of an atrial structure without distinct fluoroscopic landmarks, especially representing sinus node. Multi-detector CT is a potential new modality to detect this kind of variations more accurately. Few investigators have studied the anatomy of the SAN with noninvasive imaging modalities (8, 18, 19). The visualization rate of SAN artery by using 64-slice and dual source computed tomography was quite high (91% and 95% respectively) in these CT angiography studies (18,19).

Several cases have been reported in which the SAN artery does not arise in the right aortic sinus (20) or originates in a bronchial artery or directly from the internal thoracic artery (21). Sinoatrial node artery originating from the proximal part of the left main trunk have also been reported (13, 22-24).

There are difficulties in describing anomalous, variant, aberrant, or accessory coronary artery because of considerable heterogeneity of coronary vasculature. The terms anomalous or abnormal are used to define any variant form observed in less than 1% of the general population (5). Because of blood supply to sinoatrial node via this variant artery is carried out in a physiologically normal appearance without any functional, structural or ECG abnormality, we preferred to use the term of variant for this artery instead of abnormal, even though its frequency actually less than 1%.

Study limitations

The relatively short follow-up period (one year) is one of the limitations of the study. Slow progression of the coronary artery disease may not cause RCA occlusion during one year follow-up, and eventually arrhythmia. Certainly longer term follow-up of these patients or new patients with coronary artery disease associated variant SNA artery will explain the clinical relevance of this anomaly more accurately.

Conclusion

To be aware of the origin and course of SAN artery may provide a safe approach to interventional cardiologist and cardiac surgeon during cardiac interventions. Cardiac surgeons especially should be careful because compensation for the single SAN artery is not possible in the case of its being cut or occluded. Acute coronary syndromes associated with even mid or distal RCA occlusion may result in severe rhythm disorders related to sinus node. Similarly, during RCA percutaneous interventions, distal embolization of plaque components after balloon inflation and stent implantation may cause sinus node dysfunction, severe bradycardia, which are mostly expected to occur during proximal RCA interventions as a consequence of plaque shifting into a proximally located SAN artery. Fortunately, it seems that if exists, dual or multiple blood supply can prevent catastrophic consequences including severe bradycardia and cardiac arrest during complete RCA occlusion in patients with this variant artery. Besides the dual or multiple blood supply there is also hierarchy of spontaneous depolarizing cells in sinoatrial node, accordingly total occlusion of this artery would not inevitably be expected to lead to significant bradycardia, unless other concurrent pathologic process underway. This systematic study specifically seeking the variant origin of SAN artery from PL branch of RCA by screening 1500 patients revealed relatively high frequency when considering nonexistence of any previous similar study in the literature. We can speculate on the reasons of this finding as the variant artery actually had been observed by many cardiologists but assumed as collateral artery, or this variant could be exclusive for Turkish population suggesting an ethnic variation. Studies on different populations designed particularly to seek this artery will certainly reveal the true causes.

References

(1.) James TN. Anatomy of the coronary arteries. New York; Paul B. Hoeber:1961.

(2.) Baroldi, G. and Scomazzoni, G. The collaterals of the coronary arteries in normal and pathological hearts. Circ Res 1956; 4: 223-9.

(3.) Caetano, A. G and Lopes, A.C. Critical analysis of the clinical and surgical importance of the variations in the origin of sino-atrial node artery of the human heart. Rev Assoc Med Brass 1995; 41: 94-102.

(4.) DiDio LJ, Lopes AC, Caetano AC, Prates JC. Variations of the origin of the artery of the sinoatrial node in normal human hearts. Surg Radiol Anat 1995; 17:19-26.

(5.) Angelini P, Villason S, Chan AV, Diez JG. Normal and anomalous coronary arteries in humans. In: Angelini P, editor. Coronary Artery Anomalies. A Comprehensive Approach. Philadelphia; Lippincot Williams & Wilkins: 1999. p. 27-79.

(6.) Kyriakidis M, Vyssoulis G, Barbetseas J, Toutouzas P A clinical angiographic study of the arterial blood supply to the sinus node. Chest 1988; 94: 1054-7.

(7.) Pejkovic B, Krajne I, Anderhuber F, Kosutic D. Anatomical aspects of the arterial blood supply to the sinoatrial and atrioventricular nodes of the human heart. J Int Med Res 2008; 36: 691-8.

(8.) Saremi F, Abolhoda A, Ashikyan 0, Milliken JC, Narula J, Gurudevan SV, et al. Arterial supply to sinuatrial and atrioventricular nodes: imaging with multidetector CT. Radiology 2008; 246: 99-10.

(9.) Hutchinson ME. A study of the atrial arteries in man. J Anat 1978; 125: 39-64.

(10.) Sow ML, Ndoye JM, Lo A. The artery of the sinoatrial node: anatomic considerations based on 45 injection-dissections of the heart. Surg Radiol Anat 1996; 18:103-9.

(11.) Futami C, Tanuma K, Tanuma Y, Saito T. The arterial blood supply of the conducting system in normal human hearts. Surg Radiol Anat 2003; 25: 42-9.

(12.) Kawashima T, Sasaki H. The morphological significance of the human sinoatrial nodal branch (artery). Heart Vessels 2003; 18:213-9.

(13.) Nerantzis CE, Gavrielatos G, Lefkidis CA, Koutsaftis PN. A secret pathway of the sinus node artery. Forensic Sci Int 2009; 186: e25-6.

(14.) Romhilt DW, Hackel DB. Origin of blood supply to sinoauricular and atrioventricular node. Am Heart J 1968; 75: 279-808.

(15.) Busquet j, Fontan F, Anderson RH, Ho SY, Davies MJ. The surgical significance of the atrial branches of the coronary arteries. Int J Cardiol 1984; 6: 223-34.

(16.) Hadziselimovic H. Vascularization of the conducting system in the human heart. Acta Anat 1978; 102:105-10.

(17.) Ortale JR, Paganoti Cde F, Marchiori GF Anatomical variations in the human sinoatrial nodal artery. Clinics 2006; 61: 551-8.

(18.) Cademartiri F La Grutta L, Malago R, Alberghina E Meijboom WB, Pugliese E et al. Prevalence of anatomical variants and coronary anomalies in 543 consecutive patients studied with 64-slice CT coronary angiography. Eur Radiol 2008; 18: 781-91.

(19.) Zhang LJ, Wang YZ, Huang W, Chen P, Zhou CS, Lu GM. Anatomical investigation of the sinus node artery using dual-source computed tomography. Circ J 2008; 72:1615-20.

(20.) Kennel AJ, Titus JL. The vasculature of human sinus node. Mayo Clin Proc, 1972; 47: 556-61.

(21.) McAlpine WA. Heart and coronary arteries. Berlin; Springer Verlag: 1975.

(22.) Berna G, Montorsi R Anomalous origin of the sinus node artery from the left main trunk: a potential cause of iatrogenic hypokinetic arrhythmia. Cardiologia 1998; 43: 89-91.

(23.) Kandalaft N, Ro JH, Weiss MB, Herman MV. Anomalous origin of the sinus nodal artery from left main artery. Cathet Cardiovasc Diagn 1991; 23: 202-4.

(24.) Holdaway B, Hernandez E, Mohanty PK, Topaz 0. Anomalous sinus node artery originating from the left main coronary artery. Am Heart J 1996; 132: 449-51.

Arda Sanli Okmen, Ertan Okmen

Department of Cardiovascular Surgery, Siyami Ersek Thoracic and Cardiovascular Surgery Center, Istanbul, Turkey

Address for Correspondence/Yazisma Adresi: Ertan Okmen, MD, Department of Cardiovascular Surgery, Siyami Ersek Thoracic and Cardiovascular Surgery Center, Istanbul, Turkey

Phone: +90 262 678 50 86 Fax: +90 262 654 05 38 E-mail: ertanokmen@hotmail.com
Table 1. Demographic, clinical, electrocardiographic, and
angiographic characteristics of the patients

Patient   Age   Sex   Clinical Presentation           ECG

1         60     M        Stable angina               NSR
2         73     M        Stable angina               NSR
3         71     F        Stable angina               NSR
4         73     M        Stable angina               NSR
5         64     M         Anterior MI           ST elevation
6         58     M            USAP                    NSR
7         72     F            USAP            Atrial fibrillation
8         43     M        Stable angina         Incomplete RBBB
9         65     M         Inferior Ml           ST elevation
10        70     F            USAP                    NSR
11        68     M         ACS+Syncope         AV complete block
12        55     F        Stable angina               NSR

Patient   Coronary Angiography

1                  NCA
2         Non-critical stenosis
3            LAD bridge, NCA
4         LAD moderate stenosis
5             LAD occlusion
6         CX moderate stenosis
7               NCA, HOCM
8           Patent LAD stent
9             RCA occlusion
10        Non-critical stenosis
11        Non-critical stenosis
12                 NCA

ACS--acute coronary syndrome, ECG--electrocardiogram, HOCM--
hypertrophic obstructive cardiomyopathy, LAD--left anterior
descending artery, Ml--myocardial infarction, NCA--normal coronary
arteries, NSR--normal sinus rhythm, RBBB--right bundle branch block,
RCA--right coronary artery, USAP--unstable angina pectoris
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Title Annotation:Original Investigation/Ozgun Arastirma
Author:Okmen, Arda Sanli; Okmen, Ertan
Publication:The Anatolian Journal of Cardiology (Anadolu Kardiyoloji Dergisi)
Date:Dec 1, 2009
Words:3533
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