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Left anterior descending artery length in left and right coronary artery dominance

Ilia, Reuben ; Rosenshtein, Gabriel ; Marc Weinstein, Jean ; Cafri, Carlos ; Abu-Ful, Akram ; Gueron, Mosche

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Abstract

Introduction

The left anterior descending artery (LAD) is the vessel with the most constant origin, course and distribution. It is usually divided into proximal, middle and distal segments. Dodge et al. [1] divide the LAD into four segments. The first (proximal) segment extends to the origin of the first septal branch, the second stretches between the first and third septal branches, the third between the third septal branch and the cardiac apex, and the fourth distal to the cardiac apex. This division is important since in 78% of patients the LAD passes all the way around the apex and terminates along the diaphragmatic aspect of the left ventricle. In 22% of patients, however, the LAD fails to reach the diaphragmatic surface, terminating instead at or even before the cardiac apex [2]. Following our observation that long LADs are more commonly demonstrated in patients with left coronary dominance, we compared 100 consecutive angiograms with left coronary dominance [the posterior descending artery (PDA) being supplied by the circumflex artery] with 100 consecutive angiograms with right coronary dominance (the PDA being supplied by the right coronary artery).

Methods

We retrospectively compared 100 consecutive angiograms with left coronary dominance with 100 consecutive angiograms with right coronary dominance. Twenty-two angiograms in which the distal LAD was not adequately visualized had been discarded previously. LADs were categorized into three types: type A, the LAD terminating before the cardiac apex; type B, the LAD reaching the apex but not supplying the inferoapical segment of the left ventricle; and type C, the LAD wrapping around the apex and supplying the inferoapical segment. The LAD typing was also analyzed in relation to gender.

Results

The distribution of LAD types is shown in Table 1

Table 1
Table 1:
Typing of left anterior descending arteries in left and right coronary dominance

. It can be seen that type C LAD is more frequently found in cases of left coronary dominance. This type of LAD was found in women at least as commonly as in men.

Discussion

Stenosis of the LAD is respected by cardiologists and cardiac surgeons because of its distinctive negative influence on morbidity and mortality. However, are all LAD lesions of equal clinical importance? This issue has already been addressed by Ilia [3]. One of the cardinal points to be taken into consideration regarding the anatomical importance of the LAD is its length. When the LAD wraps around the apex, it supplies a larger mass of myocardium than when it is short and terminates before or at the apex of the left ventricle. In this situation, coronary interventions in a stenosed long LAD may have a greater influence than in a short LAD. Our finding that, in left coronary dominance, the LAD usually wraps around the apex means that a lesion in the LAD has a tremendous anatomic importance, whereas a lesion in the left PDA has a relatively minor one. In right coronary dominance, on the other hand, the LAD might be less ‘important’, because the right PDA could supply a greater amount of myocardium. These variations are of paramount importance when considering various methods of angioplasty. We have also demonstrated, unexpectedly, that in women the LAD is usually type C for both dominances. This observation is in contradiction to that of D.B. Effler (cited by Braunwald [4]).

In conclusion, we found that the LAD in left coronary dominance is usually long and wraps around the apex, and believe that angiographic interventions in such cases have important clinical significance.

References

1. Dodge JT Jr, Brown BG , Bolson EL , Dodge HT . Lumen diameter of normal human coronary arteries. Circulation 86: 1992; 232–246.
2. Perlmutt LM , Jay ME , Levin DC . Variations in the blood supply of the left ventricular apex. Invest Radiol 18: 1983; 138–142.
3. Ilia R . Proximal left anterior descending artery stenosis: dangerous or not?. Cathet Cardiovasc Diagn 33: 1994; 101–102.
4. Braunwald E . Heart Disease. New York: W.B. Saunders; 1980. p. 327.
Keywords:

coronary anatomy; coronary dominance; left anterior descending; typing

© 2001 Lippincott Williams & Wilkins, Inc.