Abstract
Dual left anterior descending coronary artery (LAD) is a rare coronary anomaly and is divided into six subgroups in the literature according to the origin and course of the short and long branches of the anomalous artery. We present two distinct cases of dual LAD which are distinguished by two branches of equal length from their counterparts in the literature.
<Learning objective: In our cases a novel dual LAD variant is presented with two main branches of equal length and reaches the cardiac apex. Cardiologists and cardiovascular surgeons should be aware of these variants to avoid misinterpretation of coronary angiography and intraoperative complications.>
Keywords: Coronary angiography, Coronary artery anomalies, Left anterior descending artery, Dual
Introduction
The incidences of coronary artery anomalies change between 0.64% and 1.3% in different coronary angiography series [1]. Despite the right coronary artery (RCA) anomalies that are common, variations of left anterior descending artery (LAD) origin, course, and distribution are less frequent [2]. Dual LAD is a rare coronary anomaly and is divided into six subgroups in the literature according to the origin and courses of the short and long branches of the anomalous artery. We present two distinct cases of dual LAD that are distinguished by two branches of equal length from their counterparts in the literature.
Case report 1
A 78-year-old female patient was admitted to the coronary intensive care unit after intubation with the diagnosis of non-ST elevation myocardial infarction and acute heart failure. She had no cardiovascular risk factor other than hypertension. Blood pressure was 130/80 mmHg and pulse rate was 110/bpm. Cardiac auscultation revealed 2/6 systolic murmur in the apex. Bilateral crepitant rales were the abnormal auscultatory findings on lung examination. There was a 1 mm ST segment depression in V5-6 leads on the electrocardiogram. Chest radiography showed an increased cardiothoracic index and pulmonary edema findings. Echocardiographic examination revealed ejection fraction 36% and moderate to severe mitral regurgitation. Left ventricle diameters were dilated with an end-diastolic diameter 61 mm and end systolic diameter 48 mm. The coronary angiography after clinical stabilization revealed that LAD divided into two main branches after its diagonal branch. The two main branches were extending in parallel on both sides of anterior interventricular sulcus (AIVS), while having equal lengths, giving septal branches and forming each part of distal bifurcation (the so-called “moustache”) together (Fig. 1a, Video 1a). Critical stenotic lesions were observed on the proximal segment of diagonal artery and right branch of dual LAD. Circumflex artery was totally occluded from the proximal segment and a 60% lesion was found at the level of right ventricular branch of RCA (Fig. 1b, Video 1b). Coronary and valve surgery was proposed to the patient. However, the patient refused the surgery.
Fig. 1.
(a) Anterior–posterior cranial view of left coronary angiogram (Case 1). (b) Left anterior oblique view of right coronary angiogram (Case 1).
Case report 2
A 56-year-old male patient was admitted to our department with chest pain. Cardiovascular risk factors were hypertension and hyperlipidemia. His blood pressure was 170/100 mmHg and pulse rate was 90/bpm. Cardiac and respiratory system examination were normal. There was T wave inversion in V3-6 leads on the electrocardiogram. Echocardiographic examination revealed ejection fraction 64% and mild mitral regurgitation. The coronary angiography revealed that LAD divided into two main branches. The two main branches were extending in parallel on both sides of AIVS, while having equal lengths like our first case (Fig. 2a and b, Video 2a and b). There were non-critical plaques. The hypertension was considered as the cause of chest pain. Diltiazem, telmisartan, hydrochlorothiazide, acetylsalicylic acid, and atorvastatin were proposed to the patient as medical treatment.
Fig. 2.
(a) Anterior–posterior cranial view of left coronary angiogram (Case 2). (b) Left anterior oblique view of right coronary angiogram (Case 2).
Discussion
The LAD normally originates from the left main coronary artery, courses in the AIVS toward the cardiac apex, and gives off diagonal branches to the anterior wall of the left ventricle and septal perforators to the interventricular septum. The dual LAD, in which two LADs (a short and a long branch) course and supply different parts of AIVS, is classified as a congenital course anomaly of the coronary tree. The short LAD courses and terminates in the AIVS and does not reach the cardiac apex, whereas the long LAD, which originates either from the left main coronary artery (LMCA) or the RCA, enters the distal part of the AIVS and reaches the cardiac apex [3]. The incidence of dual LAD in otherwise normal hearts has been reported to range from 0.13% to about 1% [2], [4] and most of the patients were asymptomatic [4]. Nevertheless, this anomaly can be found relatively often in patients with congenital heart disease such as tetralogy of Fallot and complete transposition of the great arteries [2].
Spindola-Franco and co-authors [4] provided an angiographic description of the important variants of dual LAD and classified it into four subtypes. In types I, II, and III dual LAD, both the short and long LAD originate from the LMCA or the proximal portion of the LAD. Types I and II are similar to each other. In these types, the long LAD descends on the left ventricular side (type I) or the right ventricular side (type II), of the AIVS, and then reenters the distal AIVS. In type III, the long LAD courses intramyocardially proximally in the ventricular septum, and appears on the epicardial surface in the distal part of the AIVS. In type IV dual LAD, the short LAD originates from the LMCA and the long LAD arises from the RCA. Other than this definition, Manchanda et al. have described a novel variant of dual LAD, which they named type V dual LAD, where the short LAD originates directly from the left coronary sinus, and the long LAD originates directly from the right coronary sinus [5]. Maroney et al. also described a new case where a dual LAD is observed with the short LAD originating from the LMCA and giving rise to the proximal septal perforator arteries and a single large diagonal artery. The long LAD originates from the RCA and traverses to the AIVS via a route underneath the right ventricular outflow tract. The long LAD gives off small septal perforator arteries in its proximal, mid, and distal segments. The authors propose that this is a novel variant dual LAD which they called type VI [6]. Dual LAD is divided into six subgroups in the literature according to the origin and courses of the short and long branches of the anomalous artery (Table 1). In our cases, a novel dual LAD variant is presented with two main branches of equal length and reaches the cardiac apex. To the best of our knowledge this is the first case in literature.
Table 1.
Classification of dual left anterior descending coronary artery [6].
| Type | Long LAD |
Short LAD |
Origin of major diagonal vessels | ||
|---|---|---|---|---|---|
| Origin | Course | Origin | Course | ||
| I | Proximal LAD | Epicardial course on the left ventricular side of the proximal AIVS, reentering the distal AIVS | Proximal LAD | Proximal AIVS | Proximal LAD and/or long LAD |
| II | Proximal LAD | Epicardial course on the right ventricular side of the proximal AIVS, reentering the distal AIVS | Proximal LAD | Proximal AIVS | Proximal LAD |
| III | Proximal LAD | Intramyocardial course in the proximal septum, then either emerging epicardially in the distal AIVS, or terminating intramyocardially as septal perforator arteries | Proximal LAD | Proximal AIVS | Proximal LAD or short LAD |
| IV | RCA | Epicardial free wall course anterior to the infundibulum of the right ventricle traversing to the distal AIVS, or intramyocardial course within the septal crest emerging epicardially in the distal AIVS | LMCA | Proximal AIVS | Short LAD |
| V | RCS | Intramyocardial course within the septal crest emerging epicardially in the distal AIVS | LCS | Proximal AIVS | Short LAD |
| VI | RCA | Underneath the right ventricular outflow tract in the area of the interventricular septum | LMCA | Proximal AIVS | Short LAD |
AIVS, anterior interventricular sulcus; LAD, left anterior descending artery; LCS, left coronary sinus; LMCA, left main coronary artery; RCA, right coronary artery; RCS, right coronary sinus.
It is not clear whether there is a relationship between coronary artery anomalies and coronary atherosclerosis. Even though atherosclerosis is a systemic disease, it is known that certain vessels are more prone to plaque build-ups in the arteries. In arteries in which the flow is nonlaminar, with turbulent shear stress there is a tendency for atherosclerosis. Arteries that have many bifurcations and side branch ostiums (may cause differences in flow properties) are believed to be particularly vulnerable to atherosclerosis [7]. Due to the factors mentioned above, the dual form of the LAD causing an increase in the number of bifurcations can be considered to increase predisposition toward coronary atherosclerosis. However, despite the similarities between the anatomical features of the two cases, the prevalence of atherosclerosis was different. For this reason, it is difficult to be conclusive about whether the dual form of the LAD is a risk factor in atherosclerosis.
In conclusion, we report an unusual type of coronary artery anomaly, dual LAD artery. Cardiologists and cardiovascular surgeons should be aware of these variants to avoid misinterpretation of coronary angiography and intraoperative complications.
Conflict of interest
None of the authors have any conflict of interest that should be declared.
Footnotes
Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jccase.2013.03.009.
Appendix A. Supplementary data
The following are the supplementary data to this article:
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