CTO

Chronic total coronary occlusion and contra-lateral Fractional Flow Reserve

A non-smoking 62 yo man with uncomplicated carotid atheroma and CAD familial history presented with effort dyspnea NYHA2 since 6 months. Rest ECG was normal and stress test showed 1.5 mm ST shift for 120 W and 140 bpm. Left ventricule ejection fraction was 62% by TEE. Angiogram showed chronic occlusion at the second RCA segment (Figure 1) and mild ostial LAD stenosis (Figure 2 red arrow, video 1 suppl). Rentrop grade 2 collaterals were observed from LAD to distal RCA (Figure 2 white arrows, video 1 suppl). FFR was used to stratify revascularization strategy and was measured in mid-LAD at 0.80 (Figure 2). It was decided to attempt RCA CTO and recanalization was obtained with a 38 mm X 2.5 mm DES (Figure 3, video). LAD collaterals became no more visible (figure 4, video) and mid-LAD FFR was remeasured then at 0.88. Under OMT, at last follow-up 3 years later, the patient was asymptomatic with normal stress test.

• Pathophysiological analysis: Before RCA recanalization, LAD with mild proximal stenosis had to vascularize LAD myocardial mass AND, as a result of collaterals, part or totality of RCA myocardial mass (1). Non significant proximal stenosis was then able to limit supranormal LAD flow as LAD diameter was physiologicaly calibrated for LAD myocardial mass only. Relieving vascularization of the extra RCA mass enabled unrestricted flow to LAD, explaining final near-normal FFR. This phenomenon is especially visible when donor vessel is predominant and when angiographic stenosis increases (2).
• Take home message: FFR is related to myocardial ischemic mass. Myocardial ischemic mass is a key point to integrate in therapeutic strategies in the cathlab

References

1. Leone AM, De Caterina AR, Basile E et al. Influence of the amount of myocardium subtended by a stenosis on fractional flow reserve. Circ Cardiovasc Interv. 2013;6(1):29-36.
2. Ladwiniec A, Cunnington MS, Rossington J et al. Collateral donor artery physiology and the influence of a chronic total occlusion on fractional flow reserve. Circ Cardiovasc Interv. 2015;8(4):e002219.

Figure 1: chronic mid RCA occlusion

Figure 2: LAD with mild proximal stenosis (red arrow) and collaterals towards distal RCA (white arrows). Simultaneous Fractional Flow Reserve measured in mid-LAD

Figure 3: recanalization of RCA with 38 mm x 2.5 mm DES

Figure 4: LAD angiogram after RCA recanalization with disappearance of collaterals. Simultaneous Fractional Flow Reserve measured in mid-LAD

Video supplement 1, 2