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Innovation in interventional cardiology

DFR: a new resting index

Boston Scientific has introduced a new resting index called the diastolic hyperemia-free ratio (DFR) that is comparable to iFR (instantaneous wave-free ratio) values, as demonstrated in the analysis of 893 waveform tracings from 833 patients in the VERIFY 21 and CONTRAST2 studies.

DFR values are equivalent to iFR. In fact, DFR has a diagnostic accuracy of 98%, with a sensitivity of 96% and specificity of 99%.

The main advantages of DFR are that it does not require an ECG signal, it incorporates 5 heartbeats, it is not necessary to identify the dicrotic notch of the pressure wave, and it uses mean arterial pressure, as well as the diastolic wave-free period.

The cutoff value is 0.89, independently of the diastolic period considered (30%, 65%, or 90% of diastole).

Alongside this advance is the new software added to the Polaris multimodality guidance system. The FFR Link system connects to the control panel via Bluetooth connection, to integrate the new DFR values.

Another technological advance that will be included in the Polaris control panel is the smart minimum FFR (smFFR) algorithm: this system excludes all artefacts from the fractional flow reserve (FFR) study. These artefacts commonly occur when the hemostasis valve is opened, when flushing with physiological saline or when the guidewire is withdrawn, affecting the accuracy of the values. The system has been developed based on algorithms validated by the University of Texas.

1. Hennigan B, Olroyd KG, Berry C, et al. Discordance Between Resting and Hyperemic Indices of Coronary Stenosis Severity. The VERIFY 2 Study (A Comparative Study of Resting Coronary Pressure Gradient, Instantaneous Wave-Free Ratio and Fractional Flow Reserve in an Unselected Population Referred for Invasive Angiography). Circ Cardiovasc Interv. 2016;9. pii: e004016.

2. Nishi T, Johnson NP, De Bruyne B, et al. Influence of Contrast Media Dose and Osmolality on the Diagnostic Performance of Contrast Fractional Flow Reserve. Circ Cardiovasc Interv. 2017;10. pii: e004985. doi: 10.1161/CIRCINTERVENTIONS.117.004985.

Keywords: Coronary pressure wire.