[Discordance between fractional flow reserve and nonhyperemic index with a fiber-optic pressure wire. READI EPIC-14]

Abstract

Introduction and objectives:: Functional assessment of coronary stenosis severity with the piezo-electric sensor pressure wire has shown a discrepancy of up to 20% between hyperemic and nonhyperemic indexes. No data are available with fiber-optic pressure wires. The aim of this study was to evaluate the incidence and factors related to the diagnostic discordance between these indexes with a fiber-optic pressure wire. Secondary aims were to assess diagnostic reproducibility in 2 consecutive measurements of fractional flow reserve (FFR) and diastolic pressure ratio (dPR) and evaluate the drift rate.

Methods:: We conducted a prospective, observational multicenter study in patients undergoing functional assessment with a fiber-optic pressure wire. We took 2 consecutive measurements of the dPR (cutoff point 0.89) and FFR (cut-off point 0.80) in each lesion analyzed. The diagnostic correlation between 2 measurements with the same technique and between the 2 techniques (dPR and FFR) was assessed. Clinical and angiographic factors associated with discordance (FFR−/dPR+ and FFR+/dPR−) between the 2 techniques were analyzed.

Results:: We included 428 cases of stenosis (361 patients). Diagnostic reproducibility was 95.8% for the dPR, with a correlation coefficient between the 2 measurements (dPR1 and dPR2) of 0.974 (P < .0001). For FFR, the diagnostic reproducibility was 94.9% with a correlation coefficient (FFR1 and FFR2) of 0.942 (P < .0001). The diagnostic discordance was 18.2% (FFR+/dPR− 8.2% and FFR−/dPR+ 10%). Among the variables analyzed, the factors significantly associated with FFR−/dPR+ discordance in the multivariate analysis were hypertension and intracoronary adenosine. The only factors significantly associated with FFR+/dPR− discordance were age < 75 years and stenosis > 60%. The drift rate was 5.7%.

Conclusions:: Although FFR and dPR measurements with a fiber-optic pressure wire have excellent reproducibility and a low drift rate, the discordance rate remains similar to those in previous studies with a piezo-electric pressure wire. FFR−/dPR+ discordance is associated with intracoronary adenosine and hypertension. FFR+/dPR− discordance is related to age < 75 years old and stenosis > 60%.

Keywords: Coronary physiology; Discordance; Drift; Fractional flow reserve; Nonhyperemic index.

Figure 1. Correlation coefficient and histogram of the differences between the 2 dPR and FFR measurements. dPR, diastolic pressure ratio; FFR, fractional flow reserve; SD, standard deviation.

Figure 2. Distribution of lesions according to FFR and dPR, with the rate of concordant and discordant measurements. dPR, diastolic pressure ratio; FFR, fractional flow reserve.

Figure 3. Probability of diagnostic discordance between FFR and dPR. The probability of discordance is close to 50% around the FFR cutoff point of 0.80 and decreases as it moves away from this point. Empirical model (bar chart) and model proposed by Petraco et al. (in grey). dPR, diastolic pressure ratio; FFR, fractional flow reserve.

Figura 1. Coeficiente de correlación e histograma de las diferencias de las dos mediciones de dPR y RFF. DE: desviación estándar; dPR: diastolic pressure ratio; RFF: reserva fraccional de flujo.

Figura 2. Distribución de las lesiones según la RFF y la dPR, con el porcentaje de mediciones concordantes y discordantes. dPR: diastolic pressure ratio; RFF: reserva fraccional de flujo.

Figura 3. Probabilidad de discordancia diagnóstica entre la RFF y la dPR. La probabilidad de discordancia es cercana al 50% en torno al punto de corte de RFF 0,80, y disminuye según se aleja de este. Modelo empírico (diagrama de barras) y modelo propuesto por Petraco et al. (en gris). dPR: diastolic pressure ratio; RFF: reserva fraccional de flujo.