Article ID: CJ-15-1195
Background: Fractional flow reserve (FFR) is an important physiological measure of intermediate coronary artery stenosis. Pressure signal drift (PD) is widely recognized but has largely been ignored in FFR measurements. We sought to determine the effect of PD on FFR-derived decision-making.
Methods and Results: We analyzed 1,218 FFR measurements for intermediate stenosis in 940 patients, in which the pullback maneuver confirmed PD ≤3 mmHg. The primary objectives were to determine the frequency and magnitude of PD and its effect on decision-making on the basis of an FFR cutoff of 0.80. In all, 479 (39.3%) measurements showed PD. PD was significantly associated with age, hypertension, reference diameter, left anterior descending artery lesion location, and read-out FFR values. Classification discordance between read-out and PD-corrected FFR values was detected in 44 (3.6%) measurements in total and in 9.2% of PD cases. The decision changed from FFR ≤0.80 to FFR >0.80 in 40 (3.3%) and vice versa in 4 (0.3%) measurements. PD showed no effect on decision-making when the FFR read-out value was ≤0.76 or ≥0.83.
Conclusions: PD is not uncommon, and its effect on FFR-based decision-making was not negligible in the range between 0.77 and 0.82 where reclassification occurred in 18.7% of FFR measurements.
Fractional flow reserve (FFR) is an important physiological measure that is accepted and used as the reference standard to assess the functional significance of epicardial coronary artery stenosis. FFR is particularly useful for assessing intermediate stenosis, for which angiography has limited efficacy in identifying the lesions responsible for inducing myocardial ischemia. Accumulating evidence supports the superiority of FFR-guided percutaneous coronary intervention (PCI).1–7 For optimal guidance, care should be taken to record precise pressure measurements and interpretation.7–10 To be implemented as a potential core laboratory technique, standardization of data acquisition technique and interpretation is imperative. Furthermore, when FFR or another index is used for guiding revascularization, the reproducibility or biological variability (test-retest or intrinsic variability) should be taken into consideration. Using data from the DEFER trial,11 it was reported that certainty falls to <80% when the first FFR measure is within a range of 0.77–0.83 and a second test is performed 10 min later.12 Thus, the probability that the FFR-guided revascularization strategy will change, if the test result is within this range and the retest is performed 10 min later, exceeds 20%. This analysis likely included the effects caused by both biological variability and equipment-derived reproducibility or errors such as inappropriate pressure acquisition caused by damping or ventricularization of the guiding catheter, PD, or insufficient preparation of the pressure line. Sensor pressure signal drift (PD: the pressure drift calculated by mean aortic pressure (Pa) minus mean distal coronary pressure (Pd) obtained at the completion of the pressure wire transducer pullback maneuver) during measurement is a matter of concern for determining pressure indices. Wire-related PD has been widely recognized but largely ignored (ie, its effect on FFR-based decision-making has not been systematically evaluated). A recent multicenter core laboratory analysis study13 and prospective international multicenter study14 evaluated the efficacy of iFR compared with FFR, but excluded data for PD defined as FFR ≤0.97 or ≥1.03, or <0.98 or >1.02, respectively, after pullback of the pressure wire transducer into the guiding catheter. Traditionally, experts recommend that minimal PD (<5 mmHg) should be taken into account in the calculation of the final FFR measurement, and that the measurement should be repeated when the difference is >5 mmHg.15 However, PD of 1 mmHg is roughly estimated to result in a 0.01 change in FFR measurement, and may have an effect on decision-making when FFR read-out values are close to the cutoff value. We hypothesized that PD significantly effects FFR measurement, particularly when the FFR read-out is close to an FFR cutoff value of 0.80. Therefore, the purpose of the present study was to determine the frequency and distribution of PD, and to evaluate the effect of PD on FFR-derived revascularization decision-making by comparing the read-out FFR value and the corrected FFR value on the basis of an FFR cutoff of 0.80. We further assessed if PD is associated with any lesion-, patient-, or system-related factors.
Editorial p ????
From pooled data of the institutional FFR registry listing pressure and ECG tracings between May 2011 and February 2015, including 2,018 FFR measurements in 1,545 patients referred for diagnostic or therapeutic catheterization, we selected 1,326 eligible lesions from 1,022 patients with angiographic stenosis between 30% and 80% by visual estimation and according to the following exclusion criteria. Quantitative analyses of angiograms were performed and screened by an independent operator (T.M.) blinded to the clinical and FFR measurements using standard methodology with a CMS-MEDIS system (Medis Medical Imaging Systems, Leiden, The Netherlands). The scanned segment was selected at the operator’s discretion after the diagnostic angiogram was obtained. Exclusion criteria included a history of coronary artery bypass surgery, extremely tortuous coronary arteries, severely calcified arteries, acute coronary syndrome, occluded coronary arteries, left main disease, coronary ostial stenosis, congestive heart failure, significant arrhythmia, renal insufficiency (creatinine >1.5 mg/dl), in-stent restenotic lesions, lesions located at the side branch, or an absolute contraindication to adenosine. Cardiovascular medications were not withheld before the study. In the present study, the analysis was limited to the FFR measurements obtained according to the institutional standard protocol for hyperemia induction by way of intravenous infusion of adenosine (140 μg·kg–1·min–1) or adenosine 50-triphosphate (ATP) (150 μg·kg–1·min–1) via a central vein. We also excluded FFR measurements in which no pullback maneuver to check PD was performed after FFR determination. Currently, there is no standardized protocol for correcting or interpreting PD. Because the manufacturer’s specification reports that the acceptable pressure error range is 3%, we analyzed FFR measurements arbitrarily limited to those with PD ≤3 mmHg in the present study and repeated measurements were not included. Our institutional standard protocol recommends a repeated FFR measurement when PD ≥4 mmHg, whereas the final decision to repeat measurement is at the operator’s discretion. PD ≥4 mmHg was observed in 144 lesions of 135 patients and excluded from the analysis. FFR was calculated as a corrected value of Pd/Pa after correction of Pd by pressure drift. The study was approved by the local ethics committee and conformed to the Declaration of Helsinki statement on research involving human subjects. Informed consent was given by all participants after a complete explanation of the protocol and potential risks.
Cardiac Catheterization and Hemodynamic MeasurementsFor FFR measurement, a RadiAnalyzer Xpress instrument with a PressureWire Certus (St. Jude Medical, Uppsala, MN, USA) was used to measure the distal coronary pressure. During the study period, a manufacturer device update (from G7 to G8) occurred in June 2013; the effect of the update on PD was also evaluated. The clinical cutoff point was defined as 0.80.16 All patients received a bolus of heparin (5,000 IU) before the procedure. An intracoronary bolus of nitroglycerin (0.2 mg) was administered at the beginning of the procedure. After catheterization via the radial artery using a 5- or 6-F system, each patient underwent standard selective coronary and left ventricular (LV) angiography for the assessment of coronary anatomy and LV volume and contractility. Following angiography, a guiding catheter was introduced, after which the pressure wire was introduced, zeroed, and equalized to the catheter-tip pressure before crossing the lesion. Correct equalization was confirmed during a 20-s acquisition. Afterward, the pressure sensor was positioned 9–10 cm distal to the ostium of the studied artery across the index stenosis. Baseline pressures were recorded for at least 20 s after the guiding catheter was flushed with saline to eliminate blood and contrast media. Thereafter, FFR measurement was performed during hyperemia. Because the distance of the pressure sensor of the guidewire from the guiding catheter tip is a potential source of error for analyzing PD, care was taken to maintain the sensor position during the measurement. Next, the distance from the ostium of the artery to the sensor position was determined by fastening a torque device to the advanced wire at the hub of the Y-connector and then measuring the length of wire pulled out of the catheter to position the sensor at the ostium of the vessel. PD was determined when the pressure sensor reached the tip of the guiding catheter during hyperemia, and a mean Pd-Pa PD ≤3 mmHg was confirmed and documented. The institutional standard protocol mandated repeat assessment if PD was ≥4 mmHg. In the present study, FFR measurements obtained by repeated acquisition because of this PD criterion were excluded. The distance of the pressure sensor-tipped guidewire from the guide catheter tip was documented in all cases by pullback length (cm). All pressure and ECG tracings of the console and the multichannel ECG recorder included in the catheterization laboratory’s monitoring system (RMC-4000 Cardio Master with EP amplifier system JB400G; Nihon Koden, Tokyo, Japan) were submitted to the in-hospital core cardiac physiology and morphological analysis laboratory, which is operated independently by expert medical engineers and cardiologists. Waveform tracings with phase adjustments meeting the following criteria were excluded from the analysis: loss of pressure signal at any point during the measurement phase (apart from saline flush injection); significant arrhythmia, including atrial fibrillation, that might preclude appropriate waveform analysis; and bradycardia with a heart rate <50 beats/min or tachycardia >120 beats/min, suggestive of catheter-damped Pa recording; or inappropriate Pd waveform quality. Analyzed FFR data were compared with the original read-out values determined by the catheterization laboratory; a consensus reading was agreed upon by 2 expert physicians if there were discordant values.
Statistical AnalysisSPSS version 22.0 (IBM Corp, Armonk, NY, USA) was used for baseline descriptive analyses. The normality of the data was verified using the Kolmogorov-Smirnov test. Categorical data were expressed as absolute frequencies and percentages and were compared using the χ2 or Fisher’s exact test, as appropriate. Continuous values showing a normal distribution were expressed as mean±standard deviation, and the difference between 2 groups was tested using Student’s t-test. Non-normally distributed values were expressed as median (interquartile range: IQR) and compared using Mann-Whitney U test. FFR data were divided into 2 groups on the basis of the presence or absence of PD, and comparisons were made between these groups. FFR data were corrected by PD and original read-out FFR values and corrected FFR values were compared. Linear regression analysis was also performed to examine the relationship between the 2 sets of FFR values. The correlation coefficient (R) and standard error of estimate were determined. Agreement between the 2 FFR values was evaluated by Bland-Altman plots with 95% limits of agreement. Univariate and multivariate logistic regression analyses were used to assess the predictors of the presence of PD. We included the variables with P<0.20 by univariate analysis for multivariate analysis where we performed a backward stepwise procedure. The analysis was performed on a per-lesion basis. P<0.05 was considered significant.
From the 1,326 eligible lesions with intermediate stenosis and a pullback PD ≤3 mmHg, 108 lesions were excluded from the final analysis. The most common reasons for exclusion were insufficient waveform quality (n=58), inadequate pullback maneuver to check PD (n=29), or the performance of repeated FFR measurements irrespective of PD within 3 mmHg (n=11), leaving 1,218 FFR measurements from 940 patients in the final analysis.
In total, 70.7% of patients had FFR values in the range of 0.60–0.90. Figure 1 shows the frequency and distribution of the read-out and PD-corrected FFR values. PD was observed in 39.3% (479/1,218) of total measurements (Figure 2). Of the measurements with PD, mean FFR change by PD correction was +0.02 (interquartile range +0.01–0.03). The baseline patient and lesion characteristics are shown in Table 1. The mean transducer distance from the tip of the guiding catheter was 9.3±1.7 cm. There was no difference in this distance irrespective of the presence or absence of PD (Table 1). Figure 3A depicts the significant linear relationship between read-out FFR values and PD-corrected FFR values, and Figure 3B depicts the Bland-Altman plot, which indicates an overall significantly positive bias of 0.007 (95% confidence interval [CI]: 0.006–0.008) from the read-out FFR value by the PD correction. The results of univariate and multivariate logistic regression analyses for the presence of PD are provided in Table 2. In the multivariate analysis, the presence of hypertension (odds ratio [OR], 0.71; 95% CI, 0.51–0.98; P=0.04), read-out FFR (OR, 0.14; 95% CI, 0.03–0.58; P=0.007), and Certus G8 (OR, 1.41; 95% CI, 1.04–1.91; P=0.03) remained independent predictors of the presence of PD. These analyses indicate that PD is not merely a random chance error, but rather a lesion-, patient-, and system-related error. Classification discordance between the read-out and PD-corrected FFR values was detected in 44 (3.6%) measurements in total and in 9.2% of the measurements with PD. The decision changed from FFR ≤0.80 to FFR >0.80 in 40 (3.3%) and vice versa in 4 (0.3%) measurements. The relative frequency that revascularization will change if the read-out FFR value is corrected by PD is shown in Figure 4. A nadir of 41% is reached around 0.79–0.80 if a binary threshold of 0.80 is used. When FFR values were between 0.77 and 0.82, the classification changed in 18.7% (44/235) of lesions. No decision change was expected by the PD correction when the FFR read-out value was <0.76 or >0.83. In the present cohort, 40 (3.3%) of all measurements were reclassified from the outside to inside of the gray zone after PD correction, and vice vasa in 22 measurements (1.8%). We further analyzed the prevalence that a value corrected by PD resulted in reclassification across the borders of the so-called gray zone, indicated as 0.76–0.79. No measurements moved from FFR <0.75 to FFR >0.80 or vice versa by PD correction in the present study cohort.
Frequency and distribution plot of the read-out and PD-corrected FFR values. In all, 70.7% of patients showed FFR values in the range between 0.60 and 0.90. FFR, fractional flow reserve; PD, pressure signal drift.
Frequency and distribution plot of pressure signal drift (PD), which was observed in 39.3% (479/1,218) of the total measurements.
| Total (n=1,218) |
PD=0 (n=739) |
PD±3 (n=479) |
P value | |
|---|---|---|---|---|
| Age, years | 67.0±10.1 | 67.5±10.0 | 66.3±10.3 | 0.04 |
| Male, n (%) | 997 (81.9) | 607 (82.1) | 390 (81.4) | 0.76 |
| Body mass index (kg/m2) | 24.5±3.4 | 24.5±3.3 | 24.5±3.6 | 0.92 |
| Hypertension, n (%) | 862 (70.8) | 540 (73.1) | 322 (67.2) | 0.03 |
| Hyperlipidemia, n (%) | 619 (50.8) | 382 (51.7) | 237 (49.5) | 0.48 |
| Diabetes, n (%) | 435 (35.7) | 263 (35.6) | 172 (35.9) | 0.95 |
| Current smoking, n (%) | 295 (24.2) | 190 (25.7) | 105 (21.9) | 0.13 |
| Family history, n (%) | 161 (13.2) | 88 (11.9) | 73 (15.2) | 0.10 |
| LVEF, % | 63.0 [56.0–69.0] |
63.0 [55.8–69.0] |
63.0 [58.0–68.0] |
0.52 |
| Agatston score | 148.0 [53.0–308.6] |
151.0 [55.3–312.7] |
127.4 [53.0–306.4] |
0.94 |
| QCA | ||||
| MLD, mm | 1.55 [1.26–1.87] |
1.57 [1.26–1.86] |
1.53 [1.25–1.90] |
0.73 |
| RVD, mm | 2.81 [2.42–3.23] |
2.86 [2.45–3.25] |
2.73 [2.37–3.20] |
0.03 |
| DS, % | 43.6±14.7 | 44.3±14.8 | 42.6±14.4 | 0.13 |
| Lesion length, mm | 11.3 [8.3–15.7] |
11.4 [8.5–16.2] |
11.1 [8.1–14.9] |
0.17 |
| AHA/ACC lesion classification | 0.88 | |||
| A, n (%) | 152 (19.5) | 89 (19.3) | 63 (19.7) | |
| B1, n (%) | 324 (41.5) | 196 (42.4) | 128 (40.1) | |
| B2, n (%) | 219 (28.0) | 129 (27.9) | 90 (28.2) | |
| C, n (%) | 86 (11.0) | 48 (10.4) | 38 (11.9) | |
| Pa, mmHg | 84.5±14.2 | 85.0±14.6 | 83.9±13.6 | 0.18 |
| Pd, mmHg | 70.1±15.5 | 70.7±16.0 | 69.1±14.6 | 0.07 |
| Read-out FFR | 0.85 [0.77–0.91] |
0.85 [0.78–0.91] |
0.83 [0.77–0.90] |
0.02 |
| PD-corrected FFR | 0.85 [0.78–0.91] |
0.85 [0.78–0.91] |
0.85 [0.79–0.91] |
0.48 |
| Pullback length, cm | 9.3±1.7 | 9.3±1.8 | 9.4±1.7 | 0.22 |
| LAD, n (%) | 647 (53.1) | 373 (50.5) | 274 (57.2) | 0.02 |
| Vessel | 0.02 | |||
| LAD, n (%) | 647 (53.1) | 373 (50.5) | 274 (57.2) | |
| LCX, n (%) | 228 (18.7) | 155 (21.0) | 73 (15.2) | |
| RCA, n (%) | 309 (25.4) | 186 (25.2) | 123 (25.7) | |
| Other, n (%) | 34 (2.8) | 25 (3.4) | 9 (1.9) | |
| Multivessel disease, n (%) | 756 (62.1) | 462 (62.5) | 294 (61.4) | 0.72 |
| PressureWire update | 0.048 | |||
| Certus G7, n (%) | 648 (56.6) | 398 (61.4) | 250 (38.6) | |
| Certus G8, n (%) | 496 (43.4) | 275 (55.4) | 221 (44.6) | |
AHA/ACC, American Heart Association/American College of Cardiology; DS, diameter stenosis; FFR, fractional flow reserve; LAD, left anterior descending coronary artery; LCX, left circumflex coronary artery; LVEF, left ventricular ejection fraction; MLD, minimal luminal diameter; Pa, proximal aortic pressure; Pd, distal coronary pressure; PD, pressure signal drift; QCA, quantitative coronary analysis; RCA, right coronary artery; RVD, reference vessel diameter.
Linear regression plots (A) comparing read-out FFR values and PD-corrected FFR values. The corresponding Bland-Altman plot (B) of differences against means for read-out FFR values and PD-corrected FFR values. The mean bias is represented by the solid blue line; the 95% confidence interval (CI) is represented by the dotted red line. There is an indication of an overall significantly positive bias of 0.007 (95% CI: 0.006–0.008) by the PD correction. The 95% limits of agreement ranged from –0.022 to 0.036. FFR, fractional flow reserve; PD, pressure signal drift; SEE, standard error of estimate.
| OR [95% CI] | P value | |
|---|---|---|
| Univariate | ||
| Age | 0.99 [0.98–1.00] | 0.04 |
| Male | 0.95 [0.71–1.28] | 0.75 |
| Body mass index | 1.00 [0.97–1.03] | 0.92 |
| Hypertension | 0.76 [0.59–0.97] | 0.03 |
| Hyperlipidemia | 0.92 [0.73–1.15] | 0.45 |
| Diabetes | 1.01 [0.80–1.29] | 0.91 |
| Current smoking | 0.94 [0.82–1.07] | 0.36 |
| Family history | 1.33 [0.95–1.86] | 0.09 |
| LVEF | 1.01 [1.00–1.02] | 0.13 |
| Agatston score | 1.00 [1.00–1.00] | 0.95 |
| MLD | 1.03 [0.79–1.34] | 0.82 |
| RVD | 0.84 [0.67–1.05] | 0.12 |
| DS | 0.99 [0.98–1.00] | 0.13 |
| Lesion length | 0.99 [0.97–1.01] | 0.34 |
| AHA/ACC lesion classification | 1.04 [0.89–1.21] | 0.67 |
| Pa | 0.99 [0.99–1.00] | 0.18 |
| Pd | 0.99 [0.99–1.00] | 0.07 |
| Read-out FFR | 0.52 [0.19–1.41] | 0.20 |
| PD-corrected FFR | 2.13 [0.76–5.95] | 0.15 |
| Pullback length | 0.87 [0.70–1.09] | 0.24 |
| LAD | 1.31 [1.03–1.66] | 0.02 |
| Vessel | 0.90 [0.79–1.02] | 0.08 |
| Multivessel disease | 0.92 [0.80–1.06] | 0.28 |
| PressureWire update: Certus G8 | 1.28 [1.01–1.62] | 0.04 |
| Multivariate | ||
| Hypertension | 0.71 [0.51–0.98] | 0.04 |
| Read-out FFR | 0.14 [0.03–0.58] | 0.007 |
| PressureWire update: Certus G8 | 1.41 [1.04–1.91] | 0.03 |
CI, confidence interval; OR, odds ratio. Other abbreviations as in Table 1.
Relative frequency of decision change by PD correction according to the read-out FFR values. When the FFR read-out value was <0.76 or >0.83, no decision change was expected by the PD correction. For FFR values between 0.77 and 0.82, reclassification occurred in 18.7% of all measures. Of all measurements, 1.5% of FFR values were reclassified across the border of 0.75, and the classification was changed in 3.6% across a cutoff of 0.80. There was no measurement that was reclassified beyond the “gray zone” defined as 0.76–0.79. CI, confidence interval; FFR, fractional flow reserve; PD, pressure signal drift.
Our major findings are as follows: (1) PD was observed in 39.3% (479/1,218) of the total measurements; (2) PD contributed to a positive bias in total, and FFR values increased after PD correction for the studied system; (3) PD presented as not merely a random error but as a lesion-, patient-, or system-related (device-specific) issue; (4) the classification decision changed for 3.6% of cases in total and in 9.2% of FFR measurements with PD; (5) when the FFR read-out value was <0.76 or >0.83, no decision change was expected with the PD correction. For FFR values between 0.77 and 0.82, in contrast, the classification changed in 18.7% of cases and reached a nadir of >40% around a read-out FFR value between 0.79 and 0.80; and (6) no classification change was observed from FFR <0.75 to FFR >0.80 or vice versa by PD correction.
FFR is a validated and accurate measure of the physiological significance of coronary stenosis in stable epicardial coronary artery disease.1–3,11,17 In contrast to many other indices measured in the catheterization laboratory, FFR is independent of factors influencing the basal flow condition. Moreover, variability is reportedly low and extremely reproducible,1,12,18 which strengthens the applicability of FFR to clinical judgment of revascularization by validated cutoff.19,20 Consequently, the use of FFR for the assessment of the functional severity of coronary intermediate stenosis has been incorporated into coronary revascularization guidelines, which currently recommend its clinical use based on a fixed 0.80 cutoff.21–23
Given the binomial assessment by a single index, FFR measurement requires standardized data acquisition and consideration of potential errors, including PD. However, there are no guidelines for managing PD in FFR determination, which is closely relevant to clinical judgment in catheterization laboratories. The present study revealed that the agreement between the read-out and the corrected FFR values decreased around 80% for FFR read-out values between 0.77 and 0.82, which indicates that a clinical decision in a non-negligible population may be affected by PD. To our best knowledge, this is the first study evaluating the effect of PD on decision-making in a large study population. Our findings contribute to an understanding of the clinical significance of PD and its effect on revascularization decisions. In addition, PD was associated with low FFR values, which may represent complex lesion morphology compromising wire handling and requiring a long time to pass the lesion. Our study also suggests that PD is significantly associated with the pressure measurement system (positive bias by SJM was shown in the present study) or even the version of the system (the newer version is more susceptible to the occurrence of PD). Discordant decisions can arise from both bias and imprecision. Our results indicate that device-specific factors may also contribute to a significant bias in revascularization decision-making.
Clinical populations of FFR indication are formed predominantly by intermediate lesions with FFR values showing a unimodal concentration close to the cutoff value of 0.80. Measurement error can have an important effect on clinical decision-making regarding revascularization, particularly in cases near the decision cutoff, and affect the classification of patients for therapeutic management. Given that these invasive physiological indices are primarily indicated for the evaluation of patients with stable angina pectoris (the decision regarding revascularization may not have a significant effect on mortality rate3,24 in these patients), sound clinical judgment should inform the final decision. Treatment should not proceed based on a single FFR measure, but rather should embrace a wider judgment that takes into account the character of symptoms, results of noninvasive tests of the extent of ischemia, and whether a pullback pressure gradient is focal or diffuse, particularly when FFR values are close to the cutoff value. Furthermore, we should bear in mind that most classification errors are likely to occur in this zone, whereas patients with FFR within this range present a relatively low rate of major adverse cardiac events, even if revascularization is deferred.11
Study LimitationsThe present study has several strengths and limitations. Using a strict study methodology, the data were collected retrospectively from patients with intermediate stenosis in a daily clinical setting at a single center. Analyses of the angiograms, ECGs, and pressure waveforms were performed at an independent in-hospital laboratory in a blinded fashion, but not by a core laboratory. There are 2 major commercially available pressure wire systems (the PressureWire Certus FFR Measurement System and the Volcano Wave Wire [Volcano Inc, Rancho Cordova, CA, USA]). Both systems measure intracoronary pressure using a dedicated solid-state (electronic) sensor mounted on a 0.014-inch (0.33-mm) floppy-tipped guidewire. The present study evaluated PD using the St. Jude Medical Inc. device, but there are no data available regarding the Volcano system and its effect on decision-making. The present study included measurements with PD from –3 to +3 mmHg. Therefore, PD >4 mmHg was not taken into account, which precluded the determination of an appropriate cutoff PD to require repeat measurements. Moreover, validation of FFR correction by PD obtained at the time of the pullback maneuver has not been established. PD may occur after FFR measurements during the pullback maneuver, or the actual PD might be greater during FFR determination. This may raise concern about the present study design, which evaluated PD by comparing read-out values and PD-corrected values, but this is an inevitable drawback of the current FFR measurement system. Lastly, there is no consensus regarding the PD threshold for repeat FFR measurements.
Because of PD in the studied FFR system, 3.6% of clinical decisions changed when a binary threshold of 0.80 was used, and 1.5% of decisions changed by the threshold of 0.75, whereas no decision change was expected from >0.80 to <0.75 or vice versa across the “gray zone”. For the specific subgroup of lesions with a read-out FFR value between 0.77 and 0.82, decision uncertainty can be up to 18%. Care should be taken when making revascularization decisions based on a single FFR result in this uncertainty zone. Our results showed that comprehensive assessment should be exercised when making a decision for revascularization based on a binary threshold that is potentially affected by PD. Standardized handling of PD should be advocated while taking device-specific bias into consideration.
None.
