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Ann Thorac Surg 1996;61:1874-1875
© 1996 The Society of Thoracic Surgeons
Heart Institute Good Samaritan Hospital 1225 Wilshire Blvd Los Angeles Ca 90017
To the Editor:
Blood flow via myocardial sinusoids was invoked to explain the results of the Vineberg procedure and has recently been postulated as the mechanism of supplying blood to ischemic myocardium after transmural channels have been made using laser energy-so-called transmural revascularization. In their recent article in the Surgical Heritage series, Tsang and Chiu [1] clearly unmasked the phantom of blood flow via myocardial sinusoids. Although they acknowledged that there may be other reasons why the Vineberg procedure might work, the main focus of the article was to expose the myth of myocardial sinusoids. It is important to note, however, that the absence of sinusoids in no way invalidates either the Vineberg procedure or transmural revascularization. To emphasize this point, I would like to expand on the other potential mechanisms briefly mentioned by Tsang and Chiu.
Although Vineberg [2] stated in his 1982 book that intramyocardial sinusoid spaces were part of the coronary circulation, he also found that side branches grew from the internal mammary artery to join with the surrounding myocardial arterioles. This new growth was documented by corrosion casting of the vessels rather than the ``sinusoids.'' It should also be noted that retrospective examination of the ``Vineberg literature'' has suggested that success was achieved because the internal mammary artery could arborize and communicate with the native circulation [3]. In addition, a series of articles by Unger and colleagues [4, 5] have described internal mammary artery implantation in canine hearts with subsequent angiogenesis and flow of blood to the tissue, even though both the left anterior descending artery and left circumflex coronary artery were totally occluded by ameroid constrictors. These investigators also found that administration of heparin, a known stimulant of angiogenesis, augmented the magnitude of collateral flow via the internal mammary artery [5]. Similarly, the growth of new vessels connecting needle-made [6] and laser-made myocardial channels [7] to the existing circulation has been demonstrated in animal experiments, which may explain the benefits derived from the ``modern'' procedure of transmural revascularization.
Thus, although the original proponents of both the Vineberg procedure and transmural revascularization mistakenly invoked the sinusoid theory of blood supply, there is now evidence that both methods can supply blood to ischemic myocardium via the growth of vascular connections rather than via the mythical sinusoids.
References
The Montreal General Hospital McGill University 1650 Cedar Ave Rm C9.169 Montreal Pq H3g 1a4 Canada
To the Editor
We agree with Dr Whittaker that angiogenesis rather than the preexisting run-off known as the sinusoidal system is responsible for any myocardial revascularization after both the Vineberg operation and the newer transmural revascularization procedures. As we stated in our article, if transmural revascularization eventually proves to be effective, it may be so in spite of the absence of myocardial sinusoids.
At present, the long-term patency of transmural revascularization channels created either by needle or laser remains controversial. A number of mechanisms for angiogenesis after transmural revascularization, including those discussed by Dr Whittaker, have been proposed. With such advances, we are also beginning to better understand the mechanisms underlying the pioneering work of Dr Vineberg.
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