The length of the left main coronary artery has been measured in IOO coronary cineangiograms and in IOO postmortem hearts. The results indicate that an early bifurcation of the left main coronary artery is very much more common than previously suspected. The risks of aortic valve operation in cases with an early bifurcation are discussed.One of the advances in aortic valve surgery has been perfusion of the coronary arteries by direct cannulation during valve replacement. It has been suggested (Furlong et al., 1972) that a short left main coronary artery or a wide angle between its two main branches may result in underperfusion of the left circumflex artery or less commonly the left anterior descending artery. In such cases with an early bifurcation of the left main coronary artery the coronary cannula may selectively perfuse one main branch and to a greater or lesser degree occlude the other. Thus, a portion of myocardium remains underperfused throughout the bypass and infarction may result. The incidence of short left main coronary artery was therefore determined (a) in ioo coronary cineangiograms and (b) in ioo postmortem specimens with normal hearts. MethodsThe ioo coronary cineangiograms were carried out in the cardiac department at St. Thomas' Hospital, using Judkins or Sones techniques. The orifice of the main coronary artery could usually be visualized by spill-back of contrast medium during selective injection. The distance between this point and the bifurcation of the left main coronary artery was measured in a single frame of the left selective coronary cineangiogram in the right anterior oblique position. Errors of magnification were corrected by photographing a perforated metal ruler (i cm perforations) at midchest level and adjusting the coronary artery measurement to this standard. In 6 cases, measurement of the left main coronary artery was technically impossible either because the vessel overlay some radio-opaque structure in this projection, or else because of very severe aortic regurgitation which caused the spill-back to be rapidly diluted with nonopaque blood. In one case the circumflex artery arose from the right coronary artery. Thus a total of I07 consecutive cases was examined.The postmortem hearts of normal size were obtained from Ioo consecutive necropsies performed at St. George's Hospital (by M.J.D.) on cases of accidental death. The hearts were removed from the chest and fixed in formal saline. The length of the left main coronary artery (x) was measured as shown in Fig. i.The volume of the fixed ventricle was then assessed by filling the cavity with glass beads and measuring the displacement of the beads. No volume exceeded 200 ml. The left ventricular wall including the interventricular septum was then dissected from the rest of the heart and weighed. All fell within the normal range (120-200 g). ResultsThe lengths of the left main coronary arteries measured in the coronary cineangiographs are shown in FIG. i Diagram illustrating the measurements of the left main coronary artery a...
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