Читать книгу Interventional Cardiology - Группа авторов - Страница 191

A number of other non‐hyperemic pressure ratios have been developed and they show a very strong and close relationship to iFR [74]. The diastolic pressure ratio (dPR) equals the resting ratio of the mean diastolic pressure distal to the stenosis to the mean diastolic aortic pressure. A number of iterations exist and it is numerically equivalent to iFR [75] Diastolic hyperemia‐free ratio (DFR) calculates the ratio of Pd/Pa over five beats when Pa is less than the average of Pa across a heart‐beat (ie. When the Pa is falling). This index has limited data to date. The resting full‐cycle ratio (RFR) seeks the lowest instantaneous Pd/Pa ratio within the entire cardiac cycle. RFR has a strong relationship to iFR. In some cases, this value appears to be calculated during systole, particularly in the right coronary artery [76]. The significance of this unclear. For dPR, DFR and RFR, the same threshold for revascularization has been established (0.89). Pullback approaches are under development. To date, none of the novel indices have outcome data but have been utilized in clinical practice according to their availability and numerical equivalence to iFR, which has outcome data from multiple studies and has been accepted into Guidelines.

Resting whole Pd/Pa has also been assessed and has comparable capacity to assess ischemia compared to FFR using a threshold of 0.92 [77,78]. However, Pd/Pa has a limited dynamic range to assess stenoses, has lower reproducibility and a higher susceptibility to wire drift. The addition of contrast to generate sub‐maximal hyperemia extends the accuracy of resting Pd/Pa and has a threshold of 0.83. This index cannot, however, be used for pullback assessment and there will be crosstalk between stenoses.