A new variation of dual left anterior descending coronary artery

Abstract

A 63-year-old male with past medical history of type II diabetes mellitus, hypertension, hyperlipidemia, stroke, and permanent pacemaker implant for poor chronotropic response to exercise underwent coronary computed tomography angiography (CCTA) for worsening atypical chest pain. The patient had normal myocardial perfusion by nuclear stress testing 3 months prior to this test. A rare variation of dual left anterior descending coronary artery (LAD) was identified by CCTA and subsequent coronary angiography confirmed a dual LAD and revealed no significant stenosis of the coronary arteries. Six types of dual LADs have been previously reported. However, this case showed a short LAD directly originating from the left coronary sinus and long LAD originating from the left main coronary artery. This configuration has not been reported previously in the literature to our knowledge. The short LAD main stem showed an intramyocardial course and provided septal perforators to the basal-mid interventricular septum (IVS) and right ventricular branches. The long LAD provided both diagonal branches and septal perforators to the distal IVS. CCTA in conjunction with coronary angiography played an essential role to characterize this anomaly and awareness of this anomaly merits reducing misinterpretation of coronary angiography for cardiology care providers.

<Learning objective: Dual left anterior descending coronary artery (LAD) is an important coronary anomaly to be aware of by cardiology care providers to avoid misinterpretation of coronary angiography and surgical complications related to coronary interventions. We report a new variation of dual LAD which has not been reported previously and coronary computed tomography angiography helped to characterize this anomaly. Our case further expands anatomical variations of dual LADs.>

Introduction

Coronary anomaly is an important pathology to be evaluated in patients presenting with chest pain since it may cause myocardial ischemia, arrhythmias, and sudden death [1], [2], [3]. Among them, Yamanaka et al. have reported that the prevalence of dual left anterior descending coronary artery (LAD) is 1% in patients undergoing invasive coronary angiography [2]. Spindola-Franco et al. [1] have reported four types of dual LAD and two additional types have been added by other authors [4], [5]. Utilization of coronary computed tomography angiography (CCTA) made detailed anatomical evaluation of dual LADs possible in these more recent reports [4], [5]. Our case demonstrates a short LAD directly originating from the left coronary sinus and its main stem had an intramyocardial course. A long LAD originated from the left main coronary artery (LMCA). This combination of short and long LADs has not been reported in the literature. We emphasize that CCTA played an essential role to determine this anatomy in conjunction with invasive coronary angiography.

Case report

A 63-year-old man with past medical history of type II diabetes mellitus, hypertension, hyperlipidemia, stroke, and permanent pacemaker implant for poor chronotropic response to exercise presented with worsening atypical chest pain. He had normal myocardial perfusion by Thallium²⁰¹ regadenoson stress myocardial perfusion testing 3 months prior to this presentation. Physical examination was normal. Twelve-lead electrocardiograph showed sinus bradycardia at a heart rate of 49 beats per minute, left atrial enlargement, and T wave inversion limited to V1 suggesting normal variant. Echocardiography showed normal global and regional left ventricular systolic function and mild aortic stenosis with a calculated valve area of 1.8 cm². The patient underwent CCTA, which revealed a short LAD originating from the left coronary sinus of Valsalva and a long LAD originating from the LMCA (Fig. 1, Fig. 2). The short LAD main stem showed an intramyocardial course (Fig. 1, panel B and Fig. 2, panel A). The proximal short LAD provided the right ventricular branches before becoming an intramyocardial course (Fig. 1, panel A and Fig. 2, panel B). The long LAD branched from the LMCA (Fig. 1 panel B and Fig. 2, panel C) and provided diagonal branches (Fig. 1, panels A and B). The distal long LAD coursed on the anterior interventricular ventricular sulcus (AIVS). The left circumflex coronary artery (LCX) provided posterior descending coronary artery indicating a left dominant coronary system. A moderate atheromatous plaque was noted in a branch of the short LAD (Fig. 2, panel B) and a mild atheromatous plaque was noted in the long LAD by CCTA (Fig. 2, panel C); thus, coronary angiography was performed to rule out obstructive coronary stenosis. It confirmed a dual LAD system and did not show a significant stenosis in either short LAD or long LAD (Fig. 3). The short LAD provided septal perforators to the basal-mid intraventricular septum (IVS) (Fig. 3, panel A and B) and long LAD provided them to the distal IVS (Fig. 3, panel C) in coronary angiography. In addition, it did not show significant myocardial compression of short LAD during angiography. Medical management was recommended and the patient was treated with aspirin as an additional medication at the outpatient clinic.

Fig. 1.

The volume rendering images of the dual left anterior descending coronary artery (LAD) in coronary computed tomography (CT) angiography are shown. The antero-posterior (AP) view of dual LAD with myocardial contour is shown in panels A and B. The main stem of short LAD (s-LAD) is not seen and only right ventricular branches of s-LAD (black arrow heads) are visualized. The long LAD (l-LAD) is visualized on the epicardial surface. When the CT level was adjusted to remove the myocardial content and a part of left atrial appendage was removed by post-processing in the AP view, the main stem of s-LAD appears (panel B) with right ventricular branches of s-LAD (black arrow heads). This indicates that the main stem of s-LAD is an intramyocardial course. The separate origin between s-LAD and l-LAD from the left coronary sinus is also observed in the panel B. The right anterior oblique view of the heart is shown in panel C. The right coronary artery (RCA) is hypoplastic. LCX, left circumflex coronary artery.

Fig. 2.

The dual left anterior descending coronary artery (LAD) is demonstrated by curved planar reformatted (CPR) images in coronary computed tomography angiography. In panel A, direct occurrence of the main stem of short LAD (s-LAD) from the left coronary sinus of Valsalva (LCS) with an intramyocardial course is shown. In panel B, the epicardial course of right ventricular branches from the s-LAD is shown. A moderate-degree atheromatous plaque is noted (white arrow head). In panel C, the long LAD (l-LAD) stemmed from the left main coronary artery (white arrow, LMCA) is shown. A mild atheromatous plaque was noted in the proximal l-LAD (white arrow head). A separate origin of s-LAD is depicted (black arrow head). The branching of left circumflex coronary artery from the LMCA is noted (black arrow). AR, aortic root; TV, tricuspid valve; RV, right ventricle; LV, left ventricle; IVS, intraventricular septum.

Fig. 3.

Coronary angiography of the dual left anterior descending coronary artery (LAD) is shown. Panels A and B show right (RAO) and left anterior oblique (LAO) views of short LAD (s-LAD), respectively. White arrow heads indicate septal perforators (panel A and B). The black arrows indicate right ventricular branches (panels A and B). Panels C and D show RAO and LAO views of long LAD (l-LAD). The white arrow head indicates septal perforators (panel C). The black arrows indicate diagonal branches (panel D). The white arrow denotes posterior descending coronary artery (panel D). The s-LAD of dual LAD has a separate orifice in the left coronary sinus from left main coronary artery where l-LAD occurs. s-LAD provides right ventricular branches and septal perforators to the basal-mid interventricular septum (IVS). l-LAD provides diagonal branches and septal perforators to the distal IVS. The posterior descending coronary artery arises from the circumflex coronary artery (LCX) indicating a left dominant coronary system.

Discussion

Assessment of coronary anomaly is an important part of evaluation of patients who present with chest pain [1], [2], [3]. Yamanaka et al. have reported that coronary anomalies were noted in 1.3% of 126,595 patients who underwent coronary angiography [2]. A recent study showed that CCTA identified 1.16% incidence of coronary anomalies in 8864 patients who underwent this test [3]. Dual LADs were studied by Spindola-Franco et al. and classified to four types [1]. They show early bifurcation of the LAD into one early terminating branch which remains in the AIVS (short LAD) and a second branch which has a variable course outside the AIVS but returns to the AIVS distally (long LAD) [1]. It is important to be aware of the variations of dual LADs in order to avoid misinterpretation of coronary angiography and surgical complications related to coronary interventions [1], [6], [7], [8]. Spindola-Franco et al. have reported that dual LADs occurred in 1% of patients who underwent coronary angiography [1]. Types I to III are commonly observed and show that the short LAD arises from the proximal LAD with various courses of long LAD [1]. Type IV is unique and rare with a reported incidence of 0.09% in patients who underwent coronary angiography where the short LAD occurs from the LMCA and the long LAD occurs from the right coronary artery [1]. Manchanda et al. have reported a dual LAD which showed the short LAD arising directly from the left coronary sinus and the long LAD from the right coronary sinus (type V) [4]. Yokokawa et al. have reported this rare variation and emphasized that CCTA was useful to correctly diagnose this variation [7]. Maroney et al. reported another variant of dual LAD where the short LAD occurs from the LMCA and the long LAD from the right coronary sinus (type VI) [5]. A variation of type I has been also recently reported in which the short LAD occurs from LMCA instead of LAD itself [6]. In addition, an atypical type of dual LAD which shows two similar size LADs that appeared from LMCA has also been reported [8]. Our case is unique in a sense that the short LAD occurs from the left coronary sinus as in type V; however, the long LAD originates from LMCA which has a different ostium from the short LAD as in types I–III. CCTA depicted that the short LAD main stem in our case had an intramyocardial course. Our case was also clearly different from the case reported by Subban et al. [6] in which the short LAD directly occurred from the left coronary sinus of Valsalva and its intramyocardial course. Due to this unique character, the short LAD could be missed during routine coronary angiography and is more angina-prone due to its intramyocardial course as compared to that case. To our knowledge, this combination of dual LAD has not been reported in the literature and this new variation may show a rare risk of coronary ischemia due to its intramyocardial course as compared with type V.

Utilization of CCTA is advocated for full evaluation of dual LADs [1], [4], [5], [6]. In types IV–VI, the anatomical determination of the course of anomalous long LAD is considered to be clinically important to rule out a high-risk course by CCTA [4], [5]. In our case, CCTA was informative to identify the intramyocardial course of the short LAD as well as assessing both the course and branching of the short and long LAD. Coronary angiography provided valuable information on the degree of stenosis in the segments of dual LAD where atheromatous plaques were noted by CCTA in our case [5].

Long-term prognosis of dual LAD is not well known. For instance, susceptibility to coronary artery disease of this anomaly is of clinical interest because dual LADs provide a different rheology from that of normal coronary anatomy and investigation to assess this in a long-term prospective study is warranted.

Conclusion

We describe a case with unique variation of dual LAD which shows a separate origin of a short LAD directly originating from the left coronary sinus of Valsalva with long LAD originating from LMCA. The short LAD shows an intramyocardial course and provides septal perforators to the basal-mid segments of IVS. The long LAD provides septal perforators to distal segment of IVS and diagonal branches. CCTA in conjunction with coronary angiography played an essential role to determine this coronary anomaly.

Conflict of interest

The authors declare no conflict of interest.