Effect of prolonged pressure equalization on final drifting during pressure wire studies

Pressure drifting is a troublesome error in invasive coronary function tests. This study aimed to evaluate the relationship between prolonged and short-time pressure equalizations in pressure drifting. Pressure drifting was defined as the pressure gradient between the mean pressure of the distal wire sensor (Pd) and aortic pressure (Pa) when the wire was withdrawn to the tip of the guiding catheter. Significant drifts 1 and 2 were defined as the absolute values of pressure gradients > 2 and > 3 mmHg, respectively. A logistic regression model was used to evaluate the associations between prolonged pressure equalization and each pressure drifting. The prolonged pressure equalization strategy was associated with a lower incidence of drift 1 than the short-time pressure equalization strategy (6.84% vs. 16.92%, p < 0.05). However, no statistical differences were found in the incidence of drift 2 between the prolonged and short-time pressure equalization strategies (4.27% vs. 7.69%, p = 0.34). In the multivariable regression model, only the prolonged pressure equalization strategy predicted a lower incidence of pressure drift 1. In conclusion, the prolonged pressure equalization strategy was associated with a lower incidence of significant pressure drifting with more stringent thresholds than the short-time pressure equalization strategy.

Fractional flow reserve and non-hyperemic indices: Essential tools for percutaneous coronary interventions

Hemodynamical evaluation of a coronary artery lesion is an important diagnostic step to assess its functional impact. Fractional flow reserve (FFR) received a class IA recommendation from the European Society of Cardiology for the assessment of angiographically moderate stenosis. FFR evaluation of coronary artery disease offers improvement of the therapeutic strategy, deferring unnecessary procedures for lesions with a FFR > 0.8, improving patients' management and clinical outcome. Post intervention, an optimal FFR > 0.9 post stenting should be reached and > 0.8 post drug eluting balloons. Non-hyperemic pressure ratio measurements have been validated in previous studies with a common threshold of 0.89. They might overestimate the hemodynamic significance of some lesions but remain useful whenever hyperemic agents are contraindicated. FFR remains the gold standard reference for invasive assessment of ischemia. We illustrate this review with two cases introducing the possibility to estimate also non-invasively FFR from reconstructed 3-D angiograms by quantitative flow ratio. We conclude introducing a hybrid approach to intermediate lesions (DFR 0.85-0.95) potentially maximizing clinical decision from all measurements.

FFR pressure wire comparative study: piezoresistive versus optical sensor

BACKGROUND

This study aimed to assess the reliability of pressure derived fractional flow reserve (FFR) measurement and the handling performance of the OptoWire Deux with an optical pressure sensor relative to both the PressureWire X and the Verrata Pressure wire with piezoresistive pressure sensors.

METHODS

This single centre study included 80 patients between October 2016 and May 2017 undergoing a diagnostic coronary angiography. The reliability of FFR measurement measured with the OptoWire Deux relative to the PressureWire X and Verrata Pressure wire was assessed by the presence of drift. Drift was defined as a Pd/Pa measurement different from 1.00 ± 0.02 when pulled back after a FFR measurement at the location of the initial equalisation. Handling characteristics for all pressure wires were assessed qualitatively with respect to the PressureWire Aeris.

RESULTS

Ninety-eight measurements in 78 patients were performed; two patients were excluded because the lesion could not be crossed. Very stable and reliable FFR measurements with the optical sensors were registered, relative to the piezoresistive pressure sensors. Drift was found in 11%, 37%, and 33% of the measurements for OptoWire Deux, PressureWire X, and Verrata Pressure wire respectively. The handling performance of the OptoWire Deux was better rated for steerability and torqueability in relation to the standard FFR wire. The handling of the PressureWire X was rated equally good whereas the handling of the Verrata pressure wire was rated inferior in relation to the standard FFR wire.

CONCLUSIONS

In patients undergoing FFR measurement, the OptoWire Deux has a stable and reliable pressure hence FFR measurement with fewer drift events and has good handling characteristics.

Clinical use of physiological lesion assessment using pressure guidewires: an expert consensus document of the Japanese association of cardiovascular intervention and therapeutics-update 2022

Fractional flow reserve and instantaneous wave-free ratio are widely accepted and recommended in Western and Japanese guidelines for appropriate percutaneous coronary intervention. There are, however, many differences in clinical situations between Japan and Western countries. Therefore, the Task Force on coronary physiology of the Japanese Association of Cardiovascular Intervention and Therapeutics (CVIT) has proposed an expert consensus document to summarize current evidence and suggest the practical use of physiological lesion assessment in Japan.

Multicenter clinical evaluation of a piezoresistive-MEMS-sensor rapid-exchange pressure microcatheter system for fractional flow reserve measurement

Objectives

This multicenter, prospective clinical study investigates whether the microelectromechanical‐systems‐(MEMS)‐sensor pressure microcatheter (MEMS‐PMC) is comparable to a conventional pressure wire in fractional flow reserve (FFR) measurement.

Background

As a conventional tool for FFR measurement, pressure wires (PWs) still have some limitations such as suboptimal handling characteristics and unable to maintain the wire position during pullback assessment. Recently, a MEMS‐PMC compatible with any 0.014″ guidewire is developed. Compared with the existing optical‐sensor PMC, this MEMS‐PMC has smaller profiles at both the lesion crossing and sensor packaging areas.

Methods

Two hundred and forty‐two patients with visually 30–70% coronary stenosis were enrolled at four centers. FFR was measured first with the MEMS‐PMC, and then with the PW. The primary endpoint was the Bland–Altman mean bias between the MEMS‐PMC and PW FFR.

Results

From the 224‐patient per‐protocol data, quantitative coronary angiography showed 17.9% and 55.9% vessels had diameter < 2.5 mm and stenosis >50%, respectively. The two systems' mean bias was −0.01 with [−0.08, 0.06] 95% limits‐of‐agreement. Using PW FFR≤0.80 as cutoff, the MEMS‐PMC per‐vessel diagnostic accuracy was 93.4% [95% confidence interval: 89.4–96.3%]. The MEMS‐PMC's success rate was similar to that of PW (97.5 vs. 96.3%, p = .43) with no serious adverse event, and its clinically‐significant (>0.03) drift rate was 43% less (9.5 vs. 16.7%, p = .014).

Conclusions

Our study showed the MEMS‐PMC is safe to use and has a minimal bias equal to the resolution of current FFR systems. Given the MEMS‐PMC's high measurement accuracy and rapid‐exchange nature, it may become an attractive new tool facilitating routine coronary physiology assessment.

Non-invasive procedural planning using computed tomography-derived fractional flow reserve

Objectives

This study aimed to investigate the performance of computed tomography derived fractional flow reserve based interactive planner (FFR_CT planner) to predict the physiological benefits of percutaneous coronary intervention (PCI) as defined by invasive post‐PCI FFR.

Background

Advances in FFR_CT technology have enabled the simulation of hyperemic pressure changes after virtual removal of stenoses.

Methods

In 56 patients (63 vessels) invasive FFR measurements before and after PCI were obtained and FFR_CT was calculated using pre‐PCI coronary CT angiography. Subsequently, FFR_CT and invasive coronary angiography models were aligned allowing virtual removal of coronary stenoses on pre‐PCI FFR_CT models in the same locations as PCI was performed. Relationships between invasive FFR and FFR_CT, between post‐PCI FFR and FFR_CT planner, and between delta FFR and delta FFR_CT were evaluated.

Results

Pre PCI, invasive FFR was 0.65 ± 0.12 and FFR_CT was 0.64 ± 0.13 (p = .34) with a mean difference of 0.015 (95% CI: −0.23–0.26). Post‐PCI invasive FFR was 0.89 ± 0.07 and FFR_CT planner was 0.85 ± 0.07 (p < .001) with a mean difference of 0.040 (95% CI: −0.10–0.18). Delta invasive FFR and delta FFR_CT were 0.23 ± 0.12 and 0.21 ± 0.12 (p = .09) with a mean difference of 0.025 (95% CI: −0.20–0.25). Significant correlations were found between pre‐PCI FFR and FFR_CT (r = 0.53, p < .001), between post‐PCI FFR and FFR_CT planner (r = 0.41, p = .001), and between delta FFR and delta FFR_CT (r = 0.57, p < .001).

Conclusions

The non‐invasive FFR_CT planner tool demonstrated significant albeit modest agreement with post‐PCI FFR and change in FFR values after PCI. The FFR_CT planner tool may hold promise for PCI procedural planning; however, improvement in technology is warranted before clinical application.

Temporal Changes in Coronary Hyperemic and Resting Hemodynamic Indices in Nonculprit Vessels of Patients With ST-Segment Elevation Myocardial Infarction

Importance

Percutaneous coronary intervention (PCI) of nonculprit vessels among patients with ST-segment elevation myocardial infarction (STEMI) is associated with improved clinical outcome compared with culprit vessel-only PCI. Fractional flow reserve (FFR) and coronary flow reserve are hyperemic indices used to guide revascularization. Recently, instantaneous wave-free ratio was introduced as a nonhyperemic alternative to FFR. Whether these indices can be used in the acute setting of STEMI continues to be investigated.

Objective

To assess the value of hemodynamic indices in nonculprit vessels of patients with STEMI from the index event to 1-month follow-up.

Design, Setting, and Participants

This substudy of the Reducing Micro Vascular Dysfunction in Revascularized STEMI Patients by Off-target Properties of Ticagrelor (REDUCE-MVI) randomized clinical trial enrolled 98 patients with STEMI who had an angiographic intermediate stenosis in at least 1 nonculprit vessel. Patient enrollment was between May 1, 2015, and September 19, 2017. After successful primary PCI, nonculprit intracoronary hemodynamic measurements were performed and repeated at 1-month follow-up. Cardiac magnetic resonance imaging was performed from 2 to 7 days and 1 month after primary PCI.

Main Outcomes and Measures

The value of nonculprit instantaneous wave-free ratio, FFR, coronary flow reserve, hyperemic index of microcirculatory resistance, and resting microcirculatory resistance from the index event to 1-month follow-up.

Results

Of 73 patients with STEMI included in the final analysis, 59 (80.8%) were male, with a mean (SD) age of 60.8 (9.9) years. Instantaneous wave-free ratio (SD) did not change significantly (0.93 [0.07] vs 0.94 [0.06]; P = .12) and there was no change in resting distal pressure/aortic pressure (mean [SD], 0.94 [0.06] vs 0.95 [0.06]; P = .25) from the acute moment to 1-month follow-up. The FFR decreased (mean [SD], 0.88 [0.07] vs 0.86 [0.09]; P = .001) whereas coronary flow reserve increased (mean [SD], 2.9 [1.4] vs 4.1 [2.2]; P < .001). Hyperemic index of microcirculatory resistance decreased and resting microcirculatory resistance increased from the acute moment to follow-up. The decrease in distal pressure from rest to hyperemia was smaller at the acute moment vs follow-up (mean [SD], 10.6 [11.2] mm Hg vs 14.1 [14.2] mm Hg; P = .05). This blunted acute hyperemic response correlated with final infarct size (ρ, -0.29; P = .02). The resistive reserve ratio was lower at the acute moment vs follow-up (mean [SD], 3.4 [1.7] vs 5.0 [2.7]; P < .001).

Conclusions and Relevance

In the acute setting of STEMI, nonculprit coronary flow reserve was reduced and FFR was augmented, whereas instantaneous wave-free ratio was not altered. These results may be explained by an increased hyperemic microvascular resistance and a blunted adenosine responsiveness at the acute moment that was associated with infarct size.

Functional classification discordance in intermediate coronary stenoses between fractional flow reserve and angiography-based quantitative flow ratio

Background

Measurement of the contrast-flow quantitative flow ratio (cQFR) is a novel method for rapid computational estimation of fractional flow reserve (FFR). Discordance between FFR and cQFR has not been completely characterised.

Methods

We performed a post-hoc analysis of 504 vessels with angiographically intermediate stenosis in 504 patients who underwent measurement of FFR, coronary flow reserve (CFR), the index of microcirculatory resistance (IMR) and Duke jeopardy score.

Results

In total, 396 (78.6%) and 108 (21.4%) lesions showed concordant and discordant FFR and cQFR functional classifications, respectively. Among lesions with a reduced FFR (FFR+), those with a preserved cQFR (cQFR-) showed significantly lower IMR, shorter mean transit time (Tmn), shorter lesion length (all, p<0.01) and similar CFR and Duke jeopardy scores compared with lesions showing a reduced cQFR (cQFR+). Furthermore, lesions with FFR+ and cQFR- had significantly lower IMR and shorter Tmn compared with lesions showing a preserved FFR (FFR-) and cQFR+. Of note, in cQFR+ lesions, higher IMR lesions were associated with decreased diagnostic accuracy (high-IMR; 63.0% and low-IMR; 75.8%, p<0.01). In contrast, in cQFR- lesions, lower IMR lesions was associated with decreased diagnostic accuracy (high-IMR group; 96.8% and low-IMR group; 80.0%, p<0.01). Notably, in total, 31 territories (6.2%; 'jump out' group) had an FFR above the upper limit of the grey zone (>0.80) and a cQFR below the lower limit (≤0.75). In contrast, five territories (1.0%; 'jump in' group) exhibited opposite results (FFR of ≤0.75 and cQFR of >0.80). The 'jump out' territories showed significantly higher IMR values than 'jump in' territories (p<0.01).

Conclusions

FFR- with cQFR+ is associated with increased microvascular resistance, and FFR+ with cQFR- showed preservation of microvascular function with high coronary flow. Microvascular function affected diagnostic performance of cQFR in relation to functional stenosis significance.

MRI Conditional Actively Tracked Metallic Electrophysiology Catheters and Guidewires With Miniature Tethered Radio-Frequency Traps: Theory, Design, and Validation

OBJECTIVE

Cardiovascular interventional devices typically have long metallic braids or backbones to aid in steerability and pushability. However, electromagnetic coupling of metallic-based cardiovascular interventional devices with the radiofrequency (RF) fields present during Magnetic Resonance Imaging (MRI) can make a device unsafe for use in an MRI scanner. We aimed to develop MRI conditional actively-tracked cardiovascular interventional devices by sufficiently attenuating induced currents on the metallic braid/tube and internal-cabling using miniaturized resonant floating RF traps (MBaluns).

METHOD

MBaluns were designed for placement at multiple locations along a conducting cardiovascular device to prevent the establishment of standing waves and to dissipate RF-induced energy. The MBaluns were constructed with loosely-wound solenoids to be sensitive to transverse magnetic fields created by both surface currents on the device's metallic backbone and common-mode currents on internal cables. Electromagnetic simulations were used to optimize MBalun parameters. Following optimization, two different MBalun designs were applied to MR-actively-tracked metallic guidewires and metallic-braided electrophysiology ablation catheters. Control-devices were constructed without MBaluns. MBalun performance was validated using network-analyzer quantification of current attenuation, electromagnetic Specific-Absorption-Rate (SAR) analysis, thermal tests during high SAR pulse sequences, and MRI-guided cardiovascular navigation in swine.

RESULTS

Electromagnetic SAR simulations resulted in ≈20 dB attenuation at the tip of the wire using six successive MBaluns. Network-analyzer tests confirmed ∼17 dB/MBalun surface-current attenuation. Thermal tests indicated temperature decreases of 5.9 °C in the MBalun-equipped guidewire tip. Both devices allowed rapid vascular navigation resulting from good torquability and MR-Tracking visibility.

CONCLUSION

MBaluns increased device diameter by 20%, relative to conventional devices, providing a spatially-efficient means to prevent heating during MRI.

SIGNIFICANCE

MBaluns allow use of long metallic components, which improves mechanical performance in active MR-guided interventional devices.

Feasibility and safety of jailed-pressure wire technique using durable optical fiber pressure wire for intervention of coronary bifurcation lesions

OBJECTIVES

The objective was to evaluate the safety, feasibility, and accuracy of the jailed-pressure wire technique using a durable optical fiber-based pressure wire with high-pressure dilatation using a non-compliant balloon after main vessel stenting.

BACKGROUND

Fractional flow reserve (FFR) information can help interventionists determine whether they should treat a jailed-side branch (SB). However, re-crossing a pressure wire into a jailed-SB is sometimes technically difficult.

METHODS

Fifty-one consecutive lesions from 48 patients who underwent the jailed-pressure wire technique were retrospectively investigated. The primary endpoint was complication rate and secondary endpoints included success rate of FFR measurement, incidence of wire disruption, and final drift rate. The usability of FFR for percutaneous coronary intervention of coronary bifurcation lesion was also evaluated.

RESULTS

Median age of the patients was 69 years and 80.4% were men. The most frequent underlying disease was stable angina (70.6%) and 68.6% were type B2 lesions. Our main findings were: the procedure was performed successfully in all cases without any complications or wire disruption, FFR could be measured without significant final drift in 95.9% of cases, and FFR measurements helped interventionists determine whether to perform a final kissing balloon dilatation in 49.0% cases.

CONCLUSIONS

The jailed-pressure wire technique using a durable optical fiber-based pressure wire with high-pressure post-dilatation maneuver was safe, feasible, and accurate.

Comprehensive physiological evaluation of epicardial and microvascular coronary domains using vascular conductance and zero flow pressure

AIMS

Assessment of the coronary circulation has been based largely on pressure ratios (epicardial) and resistance (micro-vessels). Simultaneous assessment of epicardial (CEPI) and microvascular conductance (CMICRO) provides an intuitive approach using the same units for both coronary domains and expressing the actual deliverability of blood. The aim of this study was to develop a novel integral method for assessing the functional severity of epicardial and microvascular disease.

METHODS AND RESULTS

We performed intracoronary pressure and Doppler flow velocity measurements in 403 vessels in 261 patients with stable coronary artery disease. Hyperaemic mid-to-late diastolic pressure and flow velocity (PV) relationships were calculated. The slope of the aortic PV indicates the overall conductance and the slope of the distal PV relationship represents CMICRO. The intercept with the x-axis represents zero-flow pressure (Pzf). CEPI was derived from microvascular and overall conductance. Median CEPI was higher compared to CMICRO (4.2 [2.1-8.0] versus 1.3 [1.0-1.7] cm/s/mmHg, p<0.001). CMICRO was independent of stenosis severity (1.3 [1.0-1.7] in FFR ≤0.80 versus 1.4 [1.0-1.8] in FFR >0.8, p=0.797). ROC curves (using FFR and HSR concordant vessels as standard) demonstrated an excellent ability of CEPI to characterise significant stenoses (AUC 0.93). When CEPI<CMICRO, a decrease in flow velocity and coronary pressure (optimal cut-off value 0.97, AUC 0.90) was demonstrated.

CONCLUSIONS

A comprehensive assessment of separate CEPI and CMICRO was feasible. CEPI has a remarkable diagnostic efficiency to detect a clinically relevant stenosis. When CEPI<CMICRO, distal flow and pressure decrease steeply, indicating myocardial ischaemia. CMICRO can be used to explore the severity of microvascular disease.

Technical aspects and limitations of fractional flow reserve measurement

BACKGROUND

The only indication for coronary revascularization is elimination of ischaemia. Invasive hemodynamic methods (fractional flow reserve - FFR and instantaneous wave-free ratio (iFR) are superior to coronary angiography in detection of lesions causing myocardial ischaemia. Current European guidelines for myocardial revascularization recommend using of FFR for detection of functional assessment of lesions severity in category IA and number of these procedures increases. However, routine usage of these methods requires knowledge of technical requirements and limitations.

AIM

The aim of the study is to summarise good clinical practice for FFR and iFR measurements with explanation of possible technical challenges, that are necessary for increasing of measurement accuracy.

CONCLUSIONS

Authors describe frequent technical mistakes and malpractice during invasive assessment of lesion severity in coronary arteries.

Clinical use of physiological lesion assessment using pressure guidewires: an expert consensus document of the Japanese Association of Cardiovascular Intervention and Therapeutics

In this document, the background, concept, and current evidence are briefly summarized. The focus is on the clinical application of physiological lesion assessment from a practical standpoint for facilities that do not have ample experience. Finally, the characteristics of new resting indexes are summarized.

Discordance between pressure drift after wire pullback and intracoronary distal pressure offset affects stenosis physiology appraisal

BACKGROUND

Drift is a well-known issue affecting intracoronary pressure measurements. A small pressure offset at the end of the procedure is generally considered acceptable, while repeat assessment is advised for drift exceeding ±2 mmHg. This practice implies that drift assessed after wire pullback equals that at the time of stenosis appraisal, but this assumption has not been systematically investigated. Our aim was to compare intra-and post-procedural pressure sensor drift and assess benefits of correction for intra-procedural drift and its effect on diagnostic classification.

METHODS

In 70 patients we compared intra- and post-procedural pressure drift for 120 hemodynamic tracings obtained at baseline and throughout the hyperemic response to intracoronary adenosine. Intra-procedural drift was derived from the intercept of the stenosis pressure gradient-velocity relationship. Diagnostic reclassification after correction for intra-procedural drift was assessed for the mean distal-to-aortic pressure ratio at baseline (Pd/Pa) and hyperemia (fractional flow reserve, FFR), and corresponding stenosis resistances.

RESULTS

Post- and intra-procedural drift exceeding the tolerated threshold was observed in 73% and 64% of the hemodynamic tracings, respectively. Discordance in terms of acceptable drift level was present for 42% of the tracings, with avoidable repeat physiological assessment in 25% and unacceptable intra-procedural drift unrecognized at final drift check in 17% of the tracings. Correction for intra-procedural drift caused higher reclassification rates for baseline than hyperemic functional indices.

CONCLUSIONS

Post-procedural pressure drift frequently does not match drift during physiological assessment. Tracing-specific correction for intra-procedural drift can potentially lower the risk of inadvertent diagnostic misclassification and prevent unnecessary repeats.