Sukhjinder Nijjer

Classification performance of instantaneous wave-free ratio (iFR) and fractional flow reserve in a clinical population of intermediate coronary stenoses: results of the ADVISE registry

AIMSnTo evaluate the classification agreement between instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) in patients with angiographic intermediate coronary stenoses.nnnMETHODS AND RESULTSnThree hundred and twelve patients (339 stenoses) with angiographically intermediate stenoses were included in this international clinical registry. The iFR was calculated using fully automated algorithms. The receiver operating characteristic (ROC) curve was used to identify the iFR optimal cut-point corresponding to FFR 0.8. The classification agreement of coronary stenoses as significant or non-significant was established between iFR and FFR and between repeated FFR measurements for each 0.05 quantile of FFR values, from 0.2 to 1. Close agreement was observed between iFR and FFR (area under ROC curve= 86%). The optimal iFR cut-off (for an FFR of 0.80) was 0.89. After adjustment for the intrinsic variability of FFR, the classification agreement (accuracy) between iFR and FFR was 94%. Amongst the stenoses classified as non-significant by iFR (>0.89) and as significant by FFR (≤0.8), 81% had associated FFR values located within the FFR grey-zone (0.75-0.8) and 41% within the 0.79-0.80 FFR range.nnnCONCLUSIONSnIn a population of intermediate coronary stenoses, the classification agreement between iFR and FFR is excellent and similar to that of repeated FFR measurements in the same sample. Vasodilator-independent assessment of intermediate stenosis seems applicable and may foster adoption of coronary physiology in the catheterisation laboratory.

Fractional Flow Reserve–Guided Revascularization: Practical Implications of a Diagnostic Gray Zone and Measurement Variability on Clinical Decisions

OBJECTIVESnThis study sought to evaluate the effects of fractional flow reserve (FFR) measurement variability on FFR-guided treatment strategy.nnnBACKGROUNDnCurrent appropriateness guidelines recommend the utilization of FFR to guide coronary revascularization based on a fixed cut-off of 0.8. This rigid approach does not take into account the intrinsic biological variability of a single FFR result and the clinical judgment of experienced interventional cardiologists. [corrected].nnnMETHODSnFFR reproducibility data from the landmark Deferral Versus Performance of PTCA in Patients Without Documented Ischemia (DEFER) trial was analyzed (two repeated FFR measurements in the same lesion, 10 min apart) and the standard deviation of the difference (SDD) between repeated measurements was calculated. The measurement certainty (probability that the FFR-guided revascularization strategy will not change if the test is repeated 10 min later) was subsequently established across the whole range of FFR values, from 0.2 to 1.nnnRESULTSnOutside the [0.75 to 0.85] FFR range, measurement certainty of a single FFR result is >95%. However, closer to its cut-off, certainty falls to less than 80% within 0.77 to 0.83, reaching a nadir of 50% around 0.8. In clinical practice, that means that each time a single FFR value falls between 0.75 and 0.85, there is a chance that the FFR-derived revascularization recommendation will change if the measurement is repeated 10 min later, with this chance increasing the closer the FFR result is to 0.8.nnnCONCLUSIONSnA measurement FFR gray-zone is found between 0.75 and 0.85]. Therefore, clinicians should make revascularization decisions based on broadened clinical judgment when a single FFR result falls within this uncertainty zone, particularly between 0.77 and 0.83, when measurement certainty falls to less than 80%.

Maximal expansion capacity with current DES platforms: a critical factor for stent selection in the treatment of left main bifurcations?

AIMSnLeft main stenting is increasingly performed and often involves deployment of a single stent across vessels with marked disparity in diameters. Knowing stent expansion capacity is critical to ensure adequate strut apposition after post-dilatation of the stent has been performed. Coronary stents are usually manufactured in only two or three different model designs with each design having a different maximal expansion capacity. Information about the different workhorse designs and their maximal achievable diameter is not commonly provided by manufacturers but, in the absence of this critically important information, stents implanted in segments with major changes in vessel diameter have the potential to become grossly overstretched and to remain incompletely apposed.nnnMETHODS AND RESULTSnWe examined the differences in workhorse designs of six commercially available drug-eluting stents (DES): the PROMUS Element, Taxus Liberté, XIENCE Prime, Resolute Integrity, BioMatrix Flex and Cypher Select stents. Using micro-computed tomography, we tested oversizing capabilities above nominal pressures for the different workhorse designs of the six DES using 4.0, 5.0 and 6.0 mm post-dilatation balloons inflated to 14 atmospheres. MLD could be increased significantly in all stents, only restricted by workhorse design limitations. Minimal inner lumen diameter (MLD) achieved after two successive 6.0 mm post-dilatations of the largest design (4.0 mm stent) was 5.7 mm for the Element, 5.6 mm for the XIENCE Prime, 6.0 mm for the Taxus, 5.4 mm for the Resolute Integrity, 5.9 mm for the BioMatrix and 5.8 mm for the Cypher stent. Significant deformations were observed during stent oversizing with large changes in terms of cell opening and crowns expansion. These are affected by design structure and reveal important differences among all stents tested. Such extensive deformations may alter the functional ability of an individual stent to scaffold a lesion and prevent restenosis.nnnCONCLUSIONSnStent selection based on stent model design may be critical, particularly for treatment of large artery and left main bifurcations where overexpansion is normally required to optimise results and ensure full expansion of the stent.

Location of side branch access critically affects results in bifurcation stenting: Insights from bench modeling and computational flow simulation

BACKGROUNDnThe aim of this study was to evaluate the impact of stent design and side branch access on final strut apposition during bifurcation stenting.nnnMETHODS AND RESULTSnA series of 6 different commercially available Drug Eluting Stents (DES) (n=42) were deployed in an identical model of a coronary bifurcation. Kissing Balloon (KB) optimization was performed after either proximal or distal recrossing of the guidewire and results were analyzed by micro-Computed-Tomography. Stent design only had a minor impact on side branch lumen area free of stent struts. Similar rate of strut malapposition was observed within the bifurcation when a consistent KB optimization protocol and an optimal distal recrossing of the wire to reaccess the side branch (SB) are followed. Conversely, proximal instead of distal cell recrossing toward the side branch produced a significant lower area of the side branch lumen free of struts than an optimal distal recrossing (60.3±7.1% versus 81.1±8.0%, p<0.0001), as well as a higher rate of strut malapposed toward the SB ostium (40.6±6.0% versus 26.0±5.7%, p=0.0005).nnnCONCLUSIONSnOptimal cell recrossing of the guidewire may be critical to ensure successful stent optimization in bifurcation PCI.

Improvement in coronary haemodynamics after percutaneous coronary intervention: assessment using instantaneous wave-free ratio

Objective To determine whether the instantaneous wave-free ratio (iFR) can detect improvement in stenosis significance after percutaneous coronary intervention (PCI) and compare this with fractional flow reserve (FFR) and whole cycle Pd/Pa. Design A prospective observational study was undertaken in elective patients scheduled for PCI with FFR ≤0.80. Intracoronary pressures were measured at rest and during adenosine-mediated vasodilatation, before and after PCI. iFR, Pd/Pa and FFR values were calculated using the validated fully automated algorithms. Setting Coronary catheter laboratories in two UK centres and one in the USA. Patients 120 coronary stenoses in 112 patients were assessed. The mean age was 63±10u2005years, while 84% were male; 39% smokers; 33% with diabetes. Mean diameter stenosis was 68±16% by quantitative coronary angiography. Results Pre-PCI, mean FFR was 0.66±0.14, mean iFR was 0.75±0.21 and mean Pd/Pa 0.83±0.16. PCI increased all indices significantly (FFR 0.89±0.07, p<0.001; iFR 0.94±0.05, p<0.001; Pd/Pa 0.96±0.04, p<0.001). The change in iFR after intervention (0.20±0.21) was similar to ΔFFR 0.22±0.15 (p=0.25). ΔFFR and ΔiFR were significantly larger than resting ΔPd/Pa (0.13±0.16, both p<0.001). Similar incremental changes occurred in patients with a higher prevalence of risk factors for microcirculatory disease such as diabetes and hypertension. Conclusions iFR and FFR detect the changes in coronary haemodynamics elicited by PCI. FFR and iFR have a significantly larger dynamic range than resting Pd/Pa. iFR might be used to objectively document improvement in coronary haemodynamics following PCI in a similar manner to FFR.

Guidelines in cardiac clinical practice: evaluation of their methodological quality using the AGREE II instrument

Although clinical guidelines have an influential role in healthcare practice, their development process and the evidence they cite has been subject to criticism. This study evaluates the quality of guidelines in cardiac clinical practice by examining how they adhere to validated methodological standards in guideline development. A structured review of cardiac clinical practice guidelines published in seven cardiovascular journals between January 2001 and May 2011 was performed. The AGREE II assessment tool was used by two researchers to evaluate guideline quality. A total of 101 guidelines were identified. Assessment of guidelines using AGREE II found methodological quality to be highly variable (median score, 58.70%; range, 45.34–76.40%). ‘Scope and purpose’ (median score, 86.1%) and ‘clarity of development’ (median score, 83.3 %) were the two domains within AGREE II that received the highest scores. Applicability (median score, 20.80%; range, 4.20–54.20%) and editorial independence (median score, 33.30%; range, 0–62.50%) had the lowest scores. There is considerable variability in the quality of cardiac clinical practice guidelines and this has not improved over the last 10 years. Incorporating validated guideline assessment tools, such as AGREE II, may improve the quality of guidelines.

How should I treat a patient with typical angina, typical angiography, negative FFR?

BACKGROUNDnA 63-year-old man was referred for cardiac catheterisation for typical angina. At angiography, high-grade stenosis of the first diagonal branch, of the proximal circumflex and of an intermediate branch was found. After treatment of the diagonal branch, fractional flow reserve of the circumflex and intermediate branch was negative, but symptoms persisted.nnnINVESTIGATIONnPhysical examination, laboratory test, stress echocardiography, fractional flow reserve, coronary flow reserve.nnnDIAGNOSISnComplex interaction between epicardial stenosis and microvascular hyporeactivity.nnnMANAGEMENTnStenting.

Method for Percutaneously Introducing, and Removing, Anatomical Stenosis of Predetermined Severity In Vivo: The “Stenotic Stent”

Current in vivo models of arterial lesions often lead to unpredictable results in terms of lesion anatomy and hemodynamical significance. This study aimed to evaluate the impact of coronary stenosis using a novel in vivo adjustable stenosis model capable of mimicking advanced human coronary lesions. We developed a series of balloon expandable covered coronary stents with a central restriction, mimicking different intermediate to severe stenosis, and implanted them percutaneously in coronary arteries of eight healthy hybrid Landrace pigs. Optical coherence tomography (OCT) pullbacks and fractional flow reserve (FFR) were acquired along the artery after implantation of the stenotic stents for precise evaluation of anatomy and functional impact. Diameter and area stenosis after deployment of the stenosis implant were, on average, respectively, 54.1u2009±u20095.9 and 78.4u2009±u20095.8xa0% and average FFR value was 0.83 (SD 0.13). There was a low correlation between FFR and MLA evaluated by OCT (ru2009=u20090.02, pu2009=u20090.94), improved with percentage area stenosis (ru2009=u2009−0.55, pu2009=u20090.12), or OCT volumetric evaluation of the stenosis taking into account not only the MLA but also the length of the lesion (ru2009=u2009−0.78, pu2009=u20090.01). This study presents a method and proof of concept for percutaneously introducing, and removing, anatomical stenosis of predetermined severity in vivo. Such in vivo model may be used to create and evaluate the impact of focal stenoses on physiological parameters such as FFR.

INSTANTANEOUS WAVE-FREE RATIO (IFR) CAN DETECT IMPROVEMENT IN CORONARY HAEMODYNAMICS AFTER PCI

The instantaneous wave–Free Ratio (iFR), a pressure–only adenosine–free index of coronary stenosis severity, has been evaluated as a diagnostic tool in the ADVISE trial and registry. However, it is unknown whether iFR can detect improvement in stenosis significance immediately after