Evaluation of intermediate coronary stenosis with intravascular ultrasound and fractional flow reserve: Its use and abuse

Long-term outcomes of fractional flow reserve-guided vs. angiography-guided percutaneous coronary intervention in contemporary practice

AIMS

Fractional flow reserve (FFR) is the reference standard for the assessment of the functional significance of coronary artery stenoses, but is underutilized in daily clinical practice. We aimed to study long-term outcomes of FFR-guided percutaneous coronary intervention (PCI) in the general clinical practice.

METHODS AND RESULTS

In this retrospective study, consecutive patients (n = 7358), referred for PCI at the Mayo Clinic between October 2002 and December 2009, were divided in two groups: those undergoing PCI without (PCI-only, n = 6268) or with FFR measurements (FFR-guided, n = 1090). The latter group was further classified as the FFR-Perform group (n = 369) if followed by PCI, and the FFR-Defer group (n = 721) if PCI was deferred. Clinical events were compared during a median follow-up of 50.9 months. The Kaplan-Meier fraction of major adverse cardiac events at 7 years was 57.0% in the PCI-only vs. 50.0% in the FFR-guided group (P = 0.016). Patients with FFR-guided interventions had a non-significantly lower rate of death or myocardial infarction compared with those with angiography-guided interventions [hazard ratio (HR): 0.85, 95% CI: 0.71-1.01, P = 0.06]; the FFR-guided deferred-PCI strategy was independently associated with reduced rate of myocardial infarction (HR: 0.46, 95% CI: 0.26-0.82, P = 0.008). After excluding patients with FFR of 0.75-0.80 and deferring PCI, the use of FFR was significantly associated with reduced rate of death or myocardial infarction (HR: 0.80, 95% CI: 0.66-0.96, P = 0.02).

CONCLUSION

In the contemporary practice, an FFR-guided treatment strategy is associated with a favourable long-term outcome. The current study supports the use of the FFR for decision-making in patients undergoing cardiac catheterization.

Morphometric assessment of coronary stenosis relevance with optical coherence tomography: a comparison with fractional flow reserve and intravascular ultrasound

OBJECTIVES

The study sought to assess the diagnostic efficiency of optical coherence tomography (OCT) in identifying hemodynamically severe coronary stenoses as determined by fractional flow reserve (FFR). Concomitant OCT and intravascular ultrasound (IVUS) area measurements were performed in a subgroup of patients to compare the diagnostic efficiency of both techniques.

BACKGROUND

The value of OCT to determine stenosis severity remains unsettled.

METHODS

Sixty-one stenoses with intermediate angiographic severity were studied in 56 patients. Stenoses were labeled as severe if FFR ≤0.80. OCT interrogation was performed in all cases, with concomitant IVUS imaging in 47 cases.

RESULTS

Angiographic stenosis severity was 50.9 ± 8% diameter stenosis with 1.28 ± 0.3 mm minimal lumen diameter. FFR was ≤0.80 in 28 (45.9%) stenoses. An overall moderate diagnostic efficiency of OCT was found (area under the curve [AUC]: 0.74; 95% confidence interval [CI]: 0.61 to 0.84), with sensitivity/specificity of 82%/63% associated with an optimal cutoff value of 1.95 mm(2). Comparison of the results in patients with simultaneous IVUS and OCT imaging revealed no significant differences in the diagnostic efficiency of OCT (AUC: 0.70; 95% CI: 0.55 to 0.83) and IVUS (AUC. 0.63; 95% CI: 0.47 to 0.77; p = 0.19). Sensitivity/specificity for IVUS was 67%/65% for an optimal cutoff value of 2.36 mm(2). In the subgroup of small vessels (reference diameter <3 mm) OCT showed a significantly better diagnostic efficiency (AUC: 0.77; 95% CI: 0.60 to 0.89) than IVUS (AUC: 0.63; 95% CI: 0.46 to 0.78) to identify functionally significant stenoses (p = 0.04).

CONCLUSIONS

OCT has a moderate diagnostic efficiency in identifying hemodynamically severe coronary stenoses. Although OCT seems slightly superior to IVUS for this purpose (particularly in vessels <3 mm), its low specificity precludes its use as a substitute of FFR for functional stenosis assessment.

Usefulness of minimal luminal coronary area determined by intravascular ultrasound to predict functional significance in stable and unstable angina pectoris

Little is known about the intravascular ultrasound (IVUS) minimal lumen area (MLA) criteria and their accuracy in lesion subsets assorted according to vessel type, lesion location, vessel size, and clinical settings. We therefore assessed the accuracy of subgroup-specific cut-off values in predicting fractional flow reserve (FFR) <0.80. In total 692 consecutive patients with 784 coronary lesions were assessed by IVUS and FFR before intervention. All patients had ≥1 target vessel with a de novo lesion (30% to 90% diameter stenosis). For prediction of FFR <0.80 in the group overall, the best cut-off value of MLA was 2.4 mm(2) (sensitivity 84% and specificity 63%). Overall diagnostic accuracy was only 69%. In the subgroup analysis, the MLA cutoff was 2.4 mm(2) for the left anterior descending coronary artery, 1.6 mm(2) for the left circumflex coronary artery, and 2.4 mm(2) for the right coronary artery. By lesion location, the optimal cutoff was 2.6 mm(2) for proximal, 2.3 mm(2) for mid, and 1.9 mm(2) for distal segments. Furthermore, the cutoffs were 3.2 mm(2) in lesions with a larger RLD >3.5 mm and 1.9 mm(2) in lesions with a smaller RLD <2.75 mm. Nevertheless, diagnostic accuracies of all subgroup-specific criteria were <80%. In conclusion, because IVUS-measured MLA is only 1 of many factors affecting coronary flow hemodynamics, even subgroup-specific criteria were inaccurate in identifying ischemia-inducible stenosis. In conclusion, direct functional assessment is therefore essential in guiding treatment strategies for coronary lesions.

Correlation between fractional flow reserve and intravascular ultrasound lumen area in intermediate coronary artery stenosis

AIMS

Fractional flow reserve (FFR) of <0.8 or 0.75 is currently used to guide revascularisation in lesions with intermediate coronary stenosis. We assessed whether there is an intravascular ultrasound (IVUS) measurement that can reliably be used to predict when patients should undergo intervention.

METHODS AND RESULTS

The analysis included 92 intermediate lesions (84 patients) located in vessel diameters >2.5 mm. Positive FFR was considered present at <0.8 and 0.75. IVUS minimum lumen area (MLA) was correlated to the FFR findings in intermediate lesions with 40-70% stenosis. The mean FFR value was 0.89 ± 0.08. Twenty-four patients (26.1%) had FFR <0.8; 17 (18.5%) <0.75. Positive correlations between FFR and IVUS measurements included MLA (r = 0.34, p<0.001), minimum lumen diameter (MLD) (r=0.31, p=0.004), lesion length (r=-0.5, p<0.001), and area stenosis (r=-0.31, p=0.01). There was no significant correlation between FFR and quantitative coronary angiography in MLD (r=0.19, p=0.06), diameter stenosis (r=0.08, p=0.4), or lesion length (r=-0.14, p=0.17). A receiver operating characteristic curve identified MLA <2.8 mm2 (sensitivity 79.7%, specificity 80.3%) as the best threshold value for FFR <0.75; and MLA <3.2 mm2 as best for FFR <0.8 (sensitivity 69.2%, specificity 68.3%).

CONCLUSIONS

Anatomic measurements of intermediate coronary lesions obtained by IVUS show a moderate correlation to FFR values, although they differ according to vessel size. IVUS MLA may be used as an alternative to FFR when assessing the need for intervention in intermediate coronary lesion. Vessel size, however, should always be taken into account.

Coronary physiology in the cath lab: beyond the basics

The adoption of invasive coronary physiologic lesion assessment before percutaneous coronary intervention has become routine in many catheterization laboratories. In the last decade, numerous studies have demonstrated favorable outcomes for revascularization decisions based on in-lab coronary physiology in many patients. The use of coronary physiology in the laboratory has been identified as a class IIa recommendation for patients in whom the clinical presentation and supporting data are too inconclusive to make an objective decision regarding treatment. This article reviews pertinent concepts and studies of the more complex applications of translesional pressure measurements for optimal patient outcomes.

Validation of intravascular ultrasound-derived parameters with fractional flow reserve for assessment of coronary stenosis severity

BACKGROUND

We assessed optimal intravascular ultrasound (IVUS) criteria for predicting functional significance of intermediate coronary lesions.

METHODS AND RESULTS

Overall, 201 patients with 236 coronary lesions underwent IVUS and invasive physiological assessment before intervention. Fractional flow reserve (FFR) was measured at maximal hyperemia induced by intravenous adenosine infusion. FFR <0.80 at maximum hyperemia was seen in 49 (21%) of the overall 236 lesions. The independent determinants of FFR were minimal lumen area (MLA; β=0.020; 95% confidence interval [CI], 0.008 to 0.031; P=0.032), plaque burden (β=-0.002; 95% CI, -0.003 to 0.001; P=0.001), lesion length with a lumen area <3.0 mm(2) (β=-0.003; 95% CI, -0.005 to -0.001; P=0.005), and left anterior descending artery location (β=-0.035; 95% CI, -0.055 to -0.016; P=0.001). The best cutoff value (with a maximal accuracy) of the MLA to predict FFR <0.80 was <2.4 mm(2), with a diagnostic accuracy of 68% (90% sensitivity, 60% specificity, and area under the curve=0.800; 95% CI, 0.742 to 0.848; P<0.001). The cutoff value of plaque burden to predict FFR <0.80 was ≥79% (69% sensitivity, 72% specificity, and area under the curve=0.756; 95% CI, 0.696 to 0.810; P<0.001). The cutoff value of lesion length with a lumen area <3.0 mm(2) was 3.1 mm (84%sensitivity, 63%specificity, and area under the curve=0.765; 95% CI, 0.706 to 0.818; P<0.001). Among 117 lesions with an MLA ≥2.4 mm(2), 112 (96%) had an FFR ≥0.80,; and all but 1 showed FFR ≥0.75. Conversely, 44 (37%) lesions with an MLA <2.4 mm(2) had an FFR <0.80.

CONCLUSIONS

IVUS-derived MLA ≥2.4 mm(2) may be useful to exclude FFR <0.80, but poor specificity limits its value for physiological assessment of lesions with MLA <2.4 mm(2). Thus, FFR or stress tests may be necessary to accurately identify ischemia-inducible intermediate stenoses.

Usefulness of the fractional flow reserve derived by intracoronary pressure wire for evaluating angiographically intermediate lesions in acute coronary syndrome

INTRODUCTION AND OBJECTIVES

In contrast to findings in stable ischemic heart disease, in acute coronary syndrome (ACS), measurement of the fractional flow reserve (FFR) using an intracoronary pressure wire has not been shown to be useful for evaluating angiographically equivocal coronary lesions. The aim of this study was to analyze outcomes at 1 year in ACS patients with lesions that were classed as intermediate on coronary angiography and which were not nonrevascularized because of the FFR value determined by intracoronary pressure wire.

METHODS

The observational study involved a cohort of patients admitted for ACS who had intermediate lesions on coronary angiography that were not revascularized because the FFR was >0.75. Functional studies were not carried out if there was angiographic evidence of instability. All-cause mortality, non-fatal myocardial infarction, revascularization of the target lesion and readmission for cardiac causes in the first year of the study were recorded.

RESULTS

The study included 106 patients with 127 lesions that were not revascularized because the FFR was >0.75. Their mean age was 69.9+/-10 years, 92 (86.8%) had non-ST-elevation ACS, the mean angiographic stenosis was 40.5+/-7.8%, and the mean FFR was 0.88+/-0.06. There were no complications during the procedure. The follow-up rate at 1 year was 95.1%. Events observed at 1 year were: 2 deaths (total mortality 1.9%), 0 fatal acute myocardial infarctions, 1 (0.9%) target lesion revascularization and 5 (4.7%) readmissions for cardiac causes.

CONCLUSIONS

Once lesions with clear angiographic signs of instability are excluded, intracoronary pressure wire measurement could be useful in ACS patients for avoiding unnecessary revascularization of angiographically intermediate coronary lesions.