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Variability of Arterial Supply to the Inferior Myocardial Wall

Variability of Arterial Supply to the Inferior Myocardial Wall

Jason Gluck, M.D.,  Dipan Desai, M.D., Ola Akinboboye, M.D.,

Introduction:  Based on the “Standardized Myocardial Segmentation and Nomenclature for Tomographic Imaging of the Heart”(Circulation 2002:105:539-542), the apical inferior, mid inferior and basal inferior walls, segments 4, 10 and 15 respectively, are supplied by the right coronary artery (RCA). .. Consequently, perfusion defects in these segments are attributed to RCA disease.  However defects are often seen in these segments in patients without RCA disease. We hypothesize that the vascular supply of the inferior myocardial segments is variable. The objective of this study was to define anatomically, the coronary supply of the inferior segments of the myocardium using coronary CT angiography (CCTA).

Methods:  We performed a retrospective review of 135 CCTA performed at our center. 
All studies were performed on a Siemens Dual-source 64-slice scanner using standard techniques. Image analysis was performed using Terarecon software. Maximum-intensity projection (MIP) images were analyzed in the frontal plane at the level of the posterior interventricular groove. The inferior wall was measured from the crux to the apex and divided into apical (apical to the papillary muscles), mid (location of papillary muscles), and basal (base to tip of mitral leaflets) thirds. The arteries that supply these segments were identified by using a combination of MIP and multi-planar reformatted images. Image analysis was based on the consensus of 3 observers.

Results:  135 CCTA scans were reviewed.  The population had an average age 56±14 years old, and 62 (46%) were female.  The most common indication for the study was chest pain.

RCA / LAD / LCX / Dual
Apical Inferior / 12(9%) / 112(83%) / 2(1.5%) / 9(6.5%)
Mid inferior / 95(70.3%) / 10(7.5%) / 13(9.6%) / 17(12.6%)
Basal Inferior / 124(92%)/  0(0%) / 8(6%) / 3(2)%

Conclusions: Vascular supply of the inferior myocardial segments is variable. The vessel that anatomically supplies the apical, mid and basal inferior segments is not the RCA in 91%, 30.7% and 8% of individuals respectively. Thus, ascribing defects in these territories to the RCA may be fraught with errors.

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