The ideal method of examining the coronary arterial tree requires injecting the coronary arteries with a barium-gelatin mixture and studying the vessels in radiographs.3,4 This method is tedious and time consuming, and most medical examiners are not provided with a large staff who have knowledge of basic anatomic landmarks. It is therefore recommended that, instead of barium-gelatin coronary injections, the heart be perfusion fixed with 10% buffered formaldehyde retrograde from the ascending aorta at 100 mm Hg pressure (Figure 184.108.40.206) for at least 1 h.
A specially constructed Lucite plug or a rubber stopper with a central tubing is inserted into the aorta, taking care that the Lucite/rubber plug does not touch the aortic valve. The Lucite plug is attached to tubing that is connected to the perfusion chamber.5 The latter is placed 135 cm above the specimen, and this provides gravity perfusion pressure that is equivalent to 100 mm Hg. As a result, the coronary arteries are fixed in a distended state that approximates the dimensions observed in living patients. Myocardial fixation is also affected, but cardiac chambers are not fixed in a distended state.
Figure 220.127.116.11A Diagram of the right and left epicardial coronary arteries as they arise from the aorta. The four major arteries that must be described in detail are right (RCA), left main (LM), left anterior descending coronary (LAD), and the left circumflex (LC) coronary arteries. Not uncommonly severe coronary (>75% cross-sectional area luminal narrowing) artery disease may effect the smaller branches (IB = intermediate or also called ramus branch, LD = left diagonal, LOM= left obtuse marginal, PDA = posterior descending artery, and RMB = right marginal branch).
This method is fairly simple, does not require sophisticated equipment in order to achieve good fixation, and the heart can be cut immediately after perfusion fixation. If perfusion fixation is impractical, the heart should be fixed for 24 h in 10% formaldehyde (10 parts of formaldehyde to 1 part of specimen) before cutting. Radiography of the heart is recommended in order to determine the extent of coronary and valvular calcification but is not essential; if coronary arteries are heavily calcified, they need to be decalcified prior to cutting at 3 to 4 mm intervals.
The vessels that must be examined in all hearts include the four major epicardial coronary arteries: the left main, the left anterior descending, the left circumflex, and the right coronary arteries. However, it is not unusual to see severe luminal narrowing in smaller branches of the main coronary arteries; left diagonals, left obtuse marginal, ramus (intermediate) branch, and the posterior descending coronary arteries (Figure 18.104.22.168A).
Following fixation and/or decalcification, the coronary arteries are cut transversely at 3 to 4 mm intervals with a sharp scalpel blade by a gentle sawing motion (not by firm pressure) to confirm sites of narrowing and to evaluate the pathologic process (e.g., atherosclerotic plaques, thrombi, dissections) directly. If the coronary arteries are heavily calcified, it is desirable to remove the coronary arteries intact. Following dissection of the vessel from the epicardial surface, each coronary artery is carefully trimmed of excess fat and the intact arterial tree is placed in a container of formic acid for slow decalcification over 12 to 18 h.
Decalcification of isolated segments of vessel may be sufficient for cases in which the coronary arteries are only focally calcified. The areas of maximal narrowing are noted by specifying the degrees of reduction of the cross-sectional area of the lumen (e.g., 0 to 25%, 26 to 50%, 51 to 75%, 76 to 90%, 91 to 99%, and 100%). Most cardiologists agree that, in the absence of other cardiac disease, significant or severe coronary artery narrowing is that exceeding a 75% cross-sectional luminal narrowing. Particular attention should be paid to the left main coronary artery because disease in this vessel is very important clinically but frequently overlooked at autopsy.6
Cross-sections from areas of maximal narrowing from each of the four major epicardial coronary arteries or their branches are selected for histologic examination. Sections of all coronary arteries containing thrombi are taken to aid in determining the type of underlying plaque morphology, i.e., plaque rupture or plaque erosion (ulceration). The site of maximal narrowing must be specified, i.e., proximal, middle, or distal coronary involvement. This is of great medicolegal importance in cases where the patient may have been inadequately examined in the physicians office or emergency room or in the hospital following chest pain. It is the location of the severe narrowing which determines if the patient is operable or not; presence of distal disease signifies non-operability.
Figure 22.214.171.124 Radiograph of epicardial coronary arteries and saphenous vein bypass graft (arrows) to left circumflex (LC) removed at autopsy. Note focal calcification of the native arteries and absence of calcification of the vein graft. A portion of the left anterior coronary artery is surrounded by myocardium (bridged or tunneled coronary artery). Arteries are decalcified prior to sectioning and embedding in paraffin. (From Virmani, R., Ursell, P.C., and Fenoglio, J.J., Examination of the heart, in Virmani, R., Atkinson, J.B., and Fenoglio, J.J., Eds., Cardiovascular Pathology, W.B. Saunders, Philadelphia, 1991, pp 1-20. With permission.)
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