iFR

Ambiguous lesion with iFR compared with FFR and IVUS

49 year gentleman was admitted due to atypical chest pain. He had a history of acute myocardial infarction and got a PCI 10 years ago. The cardiac enzyme was normal at admission. Echo showed hypokinesia of basal to mid inferior and basal inferolateral LV wall with LVEF 58%. The result of coronary angiography was left main coronary disease and three vessel disease, and the previous stent of RCA was patent with insignificant luminal narrowing probably due to neo-atherosclerosis. The lesion which was located at distal LM-pLAD (Figure 1A & B, Supplementary video 1A & B) was not clear, and we evaluate iFR to confirm the functional significance. And additional FFR and IVUS were performed to make a comparison with iFR.
The value of iFR was significant decreased (0.89) (Figure 2).The result of iFR was confirmed again with FFR. The value of FFR was 0.63 at dLAD and 0.66 at pLAD (Figure 3). As a result of iFR and FFR, we recommended two options for him with PCI and bypass surgery. However, he wanted to get a PCI. IVUS was used to guide LM PCI. The ostium of left circumflex artery showed no disease, and the measured minimal lumen area of pLAD was 2.3 mm² and distal LM was 4.35 mm² by IVUS. (Figure 4, Supplementary video 2). We used Orsiro stent 4.0x15mm using stent crossover and final kissing balloon technique, and confirmed the stent expansion and strut apposition with IVUS. Minimal stent area was 8.3 mm² at LAD ostium,13.6 mm² at distal LM. All three modalities were relatively well correlated to assess the functional significance of this ambiguous lesion.

Figure 1A & B. Coronary angiography

Supplementary video 1A & B.

Figure 2. iFR

Figure 3. FFR

Figure 4. Intravascular ultrasound

Supplementary video 2.

Take home message

The iFR is an index based on resting coronary pressure measurement during diastole. Two randomized controlled trials showed that the instantaneous wave-free ratio (iFR), a resting coronary physiological index, is noninferior to fractional flow reserve(FFR) for guiding revascularization. And the highly linear relationship between P_d/P_a and iFR reported in many studies. The resting distal to aortic coronary pressure (P_d/P_a) measured at rest is another adenosine-free index widely available in the cardiac catheterization laboratory. iFR showed some advantages and disadvantage over FFR, however, iFR is simple to use and excellent agreement with P_d/P_a, suggesting that it could be applied clinically in a similar fashion.

JACC 2017;70:2105-13.

References

N.P. Johnson, R.L. Kirkeeide, K.N. Asrress, et al.Does the instantaneous wave-free ratio approximate the fractional flow reserve? J Am Coll Cardiol, 61 (2013), pp. 1428-1435

A. Jeremias, A. Maehara, P. Genereux, et al. Multicenter core laboratory comparison of the instantaneous wave-free ratio and resting Pd/Pa with fractional flow reserve: the RESOLVE study. J Am Coll Cardiol, 2014;63:1253-61.

M. Gotberg, E.H. Christiansen, I.J. Gudmundsdottir, et al. Instantaneous wave-free ratio versus fractional flow reserve to guide PCI. N Engl J Med, 2017;376:1813-23.

Kobayashi Y, Johnson NP, Zimmermann FM, et al. Agreement of the Resting Distal to Aortic Coronary Pressure With the Instantaneous Wave-Free Ratio. JACC 2017;70:2105-13.