Author + information
- Paolo Angelini, MD⁎ ()
- ↵⁎Department of Cardiology, Texas Heart Institute, 6624 Fannin, Suite 2780, Houston, Texas 77030
I read with special interest the recent study by Pedra et al. (1) on intravascular ultrasound (IVUS) imaging of the coronary arteries after switch operation for transposition of the great arteries. Given my long-term interest in coronary congenital anomalies and their IVUS imaging, I was quite curious to know the findings at one of the most experienced centers in the Jatene operation. I was especially impressed by two conclusions made by the investigators: 1) the finding of only one case of ostial stenosis out of 37 ostia, and 2) the benign nature of the described pathologic findings (6.4% mean arterial obstruction or intimal thickening). Such findings, as reported, should be placed in some context.
First, the IVUS-studied population may not be a representative sample of the whole series of patients who underwent the switch operation. Especially, their exclusion criteria for switch procedure and for IVUS study should be discussed in more detail. The cases of postoperative sudden death and myocardial infarction should also be an intrinsic part of the consideration. The same investigators report that in two of their cases, IVUS could not be performed because of technical difficulties (1). In how many others was the IVUS study not even attempted because of similar technical problems? The fact is that coronary ostial anomalies and the anomalies of the proximal coronary course, jointly with acquired compression, torsion, and stretching, are the most likely and ominous coronary findings expected in such patients (2) and not likely the coronary atherosclerotic changes. I am not sure the researchers were fully aware of such pathologies and of their IVUS manifestations.
To give an example, their Figure 5 (1) illustrates typical findings in ectopic coronary arteries, with an intramural (aortic) course (3,4), Figure 5A illustrates an intramural (intussuscepted) coronary segment, with typical coronary hypoplasia (its circumference is much smaller than the one of a more distal segment, as seen in Figure 5B), with an elliptical cross section as compared to the more distal circular one (Fig. 5B). In similar cases, real-time cross-sectional IVUS imaging consistently shows systolic lateral compression (phasic in nature) of variable degree, which may further increase with increased cardiac output (and/or stroke volume) (3,4). Such IVUS imaging (Fig. 5A) does not correspond to the ostium, as noted in the legend, but to a more distal segment inside the wall of the aorta: an injection of saline/microbubbles in the aorta by the guiding catheter at the aortic root would have made it more obvious. The ostium in such cases is expected to be tangential, with a typical half-moon appearance on IVUS (3,4).
The aforementioned issue of hypoplasia is a fundamental one in such context, because it appears that intramural coronary arteries do not grow as normal with ageing during the first 20 years of life (this is different from the so-called Glacov phenomenon, associated with later atherosclerosis). Incidentally, our IVUS finding in similar patients carrying intussuscepted coronary arteries (currently, more than 30 cases at our institution) suggests that these coronary segments are protected both for atherosclerotic buildup and calcifications (which is quite obvious while studying older diabetic patients) (3,4).
The reported intimal thickening of 6.4 ± 5.7% of the vessel’s lumen (1) may not actually be due to atherosclerosis, but to self-limited fibrous scarring related to surgery, as suggested by the fact that it does not progress with years of follow up.
We encourage Pedra et al. (1) and other investigators of such delicate subject to study all of their postoperative patients with IVUS (and not only the technically easy ones), while being aware of the afore-mentioned methodological issues. In particular, ectopic vessels with tangential origin frequently cause great difficulties of cannulation, but they are the most important cases to be studied! The issue of the normal size of a coronary artery (and of the diagnosis of hypoplasia) is a basic one. We have conceded the difficulty of such evaluation, while establishing the normal reference lumen in cases of intussuscepted coronary arteries in adults, by assuming that the distal vessel has generally normal cross section (3,4).
- American College of Cardiology Foundation