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Retrograde CTO recanalization of RCA SVG from the contralateral LAD SVG: “Coast to coast” revascularization with FFR in between

The University of Arkansas group, headed by Drs. Uretsky and Sachdeva have previously presented their experience with retrograde chronic total occlusion (CTO) revascularization [1] and now shows us another remarkable CTO procedure [2], traversing a left anterior descending (LAD) apical collateral (grade 3) via an LAD saphenous vein graft (SVG) to revascularize the RCA SVG and posterior descending artery (PDA). In addition to going ‘‘coast to coast’’ across the heart, they also used a pressure wire to examine the collateral physiology and fractional flow reserve (FFR). The case report warrants our attention for several reasons. Firstly, working through an SVG-LAD-apical collateral vessel to revascularize distant myocardial beds amazes us for its overall implications to coronary artery revascularization. Using the retrograde CTO approach operators can successfully recanalize vessels that previously were thought untreatable by PCI, expanding the PCI population to include patients with non-functional SVGs due to distal anastomosis occlusion. Of course this technical tour de force is not without risk, one of which is noted in their report of STEMI following CTO recanalization [1]. Secondly, this case shows us the unique physiologic conditions existing in newly accessed, long standing collaterally supplied myocardial beds. For example, with the pressure wire positioned through the LAD collateral to the native PDA before opening the RCA SVG, the collateral pressure was about 55 mm Hg with the resting distal/aortic pressure (Pd/Pa) ratio of 0.45 and with 36 mcg of adenosine in each graft, FFR was 0.35 (SVG LAD) and 0.42 (SVG RCA). After stenting the RCA SVG, re-pressurization increased resting RCA pressure to 85 mm Hg, resting Pd/Pa to 0.92 with FFR of 0.79 coupled with an excellent angiographic and, ultimately clinical result. On a technical note, the coronary occlusion pressure >30 mm Hg suggests robust collateral supply. A resting Pd/Pa ratio of 0.45, of course, is well below the ischemic FFR threshold and in normal practice does not need adenosine to check FFR. It is interesting that IC adenosine decreased the Pd/Pa further but only marginally, as we would expect when vasodilatory reserve is nearly exhausted. Studies of collateral physiology during PCI demonstrate that resting coronary occlusion pressure of >30 mm Hg is associated with prevention of ischemia through acutely recruited collaterals. A pressurederived collateral flow index (CFI, [Pw 2 Pcvp]/[Pa 2 Pcvp], where Pw represents coronary wedge pressure, Pcvp central venous pressure, and Pa mean aortic blood pressure) <0.25 is associated with poorly developed collaterals and well-grown collateral vessels with CFI > 0.25 and protection from provocable ischemia. In addition, the magnitude of collateral supply is associated with major ischemic events and counter-intuitively, the risk PCI restenosis [3–5]. Based on the collateral pressure measurements, the long standing collateral supply in this patient [2] should have been sufficient to prevent significant ischemia. The comparative validation was unfortunately lacking since a NSTEMI without stress testing was the scenario that brought the patient to the cath lab. Nonetheless, after CTO revascularization, the improvement in the antegrade perfusion increased resting and hyperemic pressure (FFR) ratios and will likely provide the patient with a marked increase in exertional activity and hopefully durable freedom from ischemic sequelae. In concert with this case was their first report of the use of pressure wire in retrograde CTO [1]. In that