Feasibility of Quantitative Flow Ratio-Derived Pullback Pressure Gradient Index and Its Impact on Diagnostic Performance

Angiography-derived physiological patterns of coronary artery disease: implications with post-stenting physiology and long-term clinical outcomes

BACKGROUND

Physiological patterns of coronary artery disease (CAD) have emerged as potential determinants of functional results of percutaneous coronary interventions (PCI) and of vessel-oriented clinical outcomes (VOCE).

OBJECTIVES

In this study, we evaluated the impact of angiography-derived physiological patterns of CAD on post-PCI functional results and long-term clinical outcomes.

METHODS

Pre-PCI angiography-derived fractional flow reserve (FFR) virtual pullbacks were quantitatively interpreted and used to determine the physiological patterns of CAD. Suboptimal post-PCI physiology was defined as an angiography-derived FFR value ≤ 0.91. The primary endpoint was the occurrence of VOCE at the longest available follow-up.

RESULTS

Six hundred fifteen lesions from 516 patients were stratified into predominantly focal (n = 322, 52.3%) and predominantly diffuse (n = 293, 47.7%). Diffuse pattern of CAD was associated with lower post-PCI angiography-derived FFR values (0.91 ± 0.05 vs. 0.94 ± 0.05; p = 0.001) and larger rate of suboptimal post-PCI physiology (43.0 vs. 22.7%; p = 0.001), as compared to focal CAD. At the median follow-up time of 37 months (33-58), post-PCI suboptimal physiology was related to a higher risk of VOCE (16.2% vs. 7.6%; HR: 2.311; 95% CI 1.410-3.794; p = 0.0009), while no significant difference was noted according to baseline physiological pattern. In diffuse disease, the use of intracoronary imaging was associated with a lower incidence of long-term VOCE (5.1% vs 14.8%; HR: 0.313, 95% CI 0.167-0.614, p = 0.030).

CONCLUSIONS

Suboptimal post-PCI physiology is observed more often in diffusely diseased arteries and it is associated with higher risk of VOCE at follow-up. The use of intravascular imaging might improve clinical outcomes in the setting of diffuse CAD.

Quantitative flow ratio derived pullback pressure gradient and CZT-SPECT measured longitudinal flow gradient for hemodynamically significant coronary artery disease

BACKGROUND

Whether physiological coronary diffuseness assessed by quantitative flow reserve (QFR) pullback pressure gradient (PPG) correlates with longitudinal myocardial blood flow (MBF) gradient and improves diagnostic performances for myocardial ischemia remains unknown.

METHODS AND RESULTS

MBF was measured in mL g-1 min-1 with 99mTc-MIBI CZT-SPECT at rest and stress, corresponding myocardial flow reserve (MFR = MBF stress/MBF rest) and relative flow reserve (RFR = MBF stenotic area/MBF reference) were calculated. Longitudinal MBF gradient was defined as apical and basal left ventricle MBF gradient. △longitudinal MBF gradient was calculated by longitudinal MBF gradient at stress and rest. QFR-PPG was acquired from virtual QFR pullback curve. QFR-PPG significantly correlated with hyperemic longitudinal MBF gradient (r = 0.45, P = 0.007) and △longitudinal MBF gradient (stress-rest) (r = 0.41, P = 0.016). Vessels with lower RFR had lower QFR-PPG (0.72 vs. 0.82, P = 0.002), hyperemic longitudinal MBF gradient (1.14 vs. 2.22, P = 0.003) and △longitudinal MBF gradient (0.50 vs. 1.02, P = 0.003). QFR-PPG, hyperemic longitudinal MBF gradient and △longitudinal MBF gradient showed comparable diagnostic performances for predicting decreased RFR (area under curve [AUC]: 0.82 vs. 0.81 vs. 0.75, P = NS) or QFR (AUC: 0.83 vs. 0.72 vs. 0.80, P = NS). In addition, QFR-PPG and QFR in combination showed incremental value compared with QFR for predicting RFR (AUC = 0.83 vs. 0.73, P = 0.046, net reclassification index = 0.508, P = 0.001).

CONCLUSION

QFR-PPG significantly correlated with longitudinal MBF gradient and △longitudinal MBF gradient when used for physiological coronary diffuseness assessment. All three parameters had high accuracy in predicting RFR or QFR. Adding physiological diffuseness assessment increased accuracy for predicting myocardial ischemia.

Coronary Angiography Upgraded by Imaging Post-Processing: Present and Future Directions

Advances in computer technology and image processing now allow us to obtain from angiographic images a large variety of information on coronary physiology without the use of a guide-wire as a diagnostic information equivalent to FFR and iFR but also information allowing for the performance of a real virtual percutaneous coronary intervention (PCI) and finally the ability to obtain information to optimize the results of PCI. With specific software, it is now possible to have a real upgrading of invasive coronary angiography. In this review, we present the different advances in this field and discuss the future perspectives offered by this technology.

Ischemia With Nonobstructive Coronary Artery Disease: Concept, Assessment, and Management

In daily clinical practice, physicians often encounter patients with angina or those with evidence of myocardial ischemia from noninvasive tests but not having obstructive coronary artery disease. This type of ischemic heart disease is referred to as ischemia with nonobstructive coronary arteries (INOCA). INOCA patients often suffer from recurrent chest pain without adequate management and are associated with poor clinical outcomes. There are several endotypes of INOCA, and each endotype should be treated based on its specific underlying mechanism. Therefore, identifying INOCA and discriminating its underlying mechanisms are important issues and of clinical interest. Invasive physiologic assessment is the first step in the diagnosis of INOCA and discriminating the underlying mechanism; additional provocation tests help physicians identify the vasospastic component in INOCA patients. Comprehensive information acquired from these invasive tests can provide a template for mechanism-specific management for patients with INOCA.

Anatomical and Functional Discrepancy in Diabetic Patients With Intermediate Coronary Lesions - An Intravascular Ultrasound and Quantitative Flow Ratio Study

BACKGROUND

Data regarding the performance of computational fractional flow reserve in patients with diabetes mellitus (DM) remain scarce. This study sought to explore the impact of DM on quantitative flow ratio (QFR) and its association with intravascular ultrasound (IVUS)-derived anatomical references.

METHODS AND RESULTS

IVUS and QFR were retrospectively analyzed in 237 non-diabetic and 93 diabetic patients with 250 and 102 intermediate lesions, respectively. Diabetics were further categorized based on adequate (HbA1c <7.0%: 47 patients with 53 lesions) or poor (HbA1c ≥7.0%: 46 patients with 49 lesions) glycemic control. Lesions with QFR ≤0.8 or minimum lumen area (MLA) ≤4.0 mm2and plaque burden (PB, %) ≥70 were considered functionally or anatomically significant, respectively. PB increased, and MLA decreased stepwise across non-diabetics, diabetics with adequate glycemic control and those with poor glycemic control. In contrast, QFR was similar among the 3 groups. PB correlated significantly with the QFR for lesions in non-diabetics, but not for lesions in diabetics. DM was independently correlated with the functionally non-significant lesions (QFR >0.8) with high-risk IVUS features (MLA ≤4.0 mm2and PB ≥70; OR 2.053, 95% CI: 1.137-3.707, P=0.017). When considering the effect of glycemic control, HbA1c was an independent predictor of anatomical-functional discordance (OR 1.347, 95% CI: 1.089-1.667, P=0.006).

CONCLUSIONS

Anatomical-functional discordance of intermediate coronary lesions assessed by IVUS and QFR is exacerbated in patients with diabetes, especially when glycemia is poorly controlled.

Association of Lipoprotein (a) With Coronary-Computed Tomography Angiography-Assessed High-Risk Coronary Disease Attributes and Cardiovascular Outcomes

BACKGROUND

Lipoprotein(a) [Lp(a)] is a risk factor for cardiovascular events. This study evaluated the relationship between Lp(a) and high-risk attributes by coronary computed tomography angiography as well as their prognostic value.

METHODS

Lp(a) and coronary computed tomography angiography from 377 consecutive patients at Zhongshan Hospital (Shanghai, China) were evaluated. High-risk attributes were defined as high-risk morphological attributes (low attenuation plaque, positive remodeling, napkin-ring sign, spotty calcification, minimum lumen area <4 mm², or plaque burden [ratio between cross-sectional plaque area at the site of maximum stenosis and cross-sectional vessel area] ≥70%); inflammatory attribute represented by fat attenuation index; high-risk physiological attributes [lesion-specific ischemia defined by fractional flow reserve by coronary computed tomography angiography ≤0.8, physiologic diffuseness defined by fractional flow reserve by coronary computed tomography angiography pullback pressure gradient]. Total plaque volume in mm³ was also quantified. Quintiles or binary classification of Lp(a) levels were used to evaluate its relationships with plaque features and clinical outcomes with ANOVA, Cox models, and log-rank tests, as appropriate. The major adverse cardiovascular event included cardiovascular death, nonfatal myocardial infarction, and target vessel revascularization.

RESULTS

Lp(a) was significantly associated with total plaque volume (P=0.004), fat attenuation index (P=0.031), and fractional flow reserve by coronary computed tomography angiography pullback pressure gradient (P=0.038). Patients with a high Lp(a) level had a higher total plaque volume (393.3 mm³ versus 293.9 mm³, P<0.001), lower pullback pressure gradient (0.62 versus 0.69, P=0.023), higher fat attenuation index (-70.5HU versus -73.9HU, P=0.004), and higher incidence of major adverse cardiovascular event (14.5% versus 6.3%, adjusted hazard ratio: 2.52, 95% CI: 1.12-5.63, P=0.025). In a 4-group classification according to Lp(a) and high-risk attributes, patients with high Lp(a) and ≥3 high-risk attributes had the highest risk of major adverse cardiovascular event (25.9%; overall P<0.001). Causal mediation analysis revealed that around 40% of the prognostic effect of Lp(a) was mediated by high-risk attributes.

CONCLUSIONS

Lp(a) level is associated with coronary computed tomography angiography high-risk characteristics, including morphologic, physiologic, and inflammatory attributes as well as major adverse cardiovascular event. This effect is partly mediated by inflammation and vulnerable plaque.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT05323227.

Prognostic Implications of Fractional Flow Reserve After Coronary Stenting: A Systematic Review and Meta-analysis

IMPORTANCE

Fractional flow reserve (FFR) after percutaneous coronary intervention (PCI) is generally considered to reflect residual disease. Yet the clinical relevance of post-PCI FFR after drug-eluting stent (DES) implantation remains unclear.

OBJECTIVE

To evaluate the clinical relevance of post-PCI FFR measurement after DES implantation.

DATA SOURCES

MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials were searched for relevant published articles from inception to June 18, 2022.

STUDY SELECTION

Published articles that reported post-PCI FFR after DES implantation and its association with clinical outcomes were included.

DATA EXTRACTION AND SYNTHESIS

Patient-level data were collected from the corresponding authors of 17 cohorts using a standardized spreadsheet. Meta-estimates for primary and secondary outcomes were analyzed per patient and using mixed-effects Cox proportional hazard regression with registry identifiers included as a random effect. All processes followed the Preferred Reporting Items for Systematic Review and Meta-analysis of Individual Participant Data.

MAIN OUTCOMES AND MEASURES

The primary outcome was target vessel failure (TVF) at 2 years, a composite of cardiac death, target vessel myocardial infarction (TVMI), and target vessel revascularization (TVR). The secondary outcome was a composite of cardiac death or TVMI at 2 years.

RESULTS

Of 2268 articles identified, 29 studies met selection criteria. Of these, 28 articles from 17 cohorts provided data, including a total of 5277 patients with 5869 vessels who underwent FFR measurement after DES implantation. Mean (SD) age was 64.4 (10.1) years and 4141 patients (78.5%) were men. Median (IQR) post-PCI FFR was 0.89 (0.84-0.94) and 690 vessels (11.8%) had a post-PCI FFR of 0.80 or below. The cumulative incidence of TVF was 340 patients (7.2%), with cardiac death or TVMI occurring in 111 patients (2.4%) at 2 years. Lower post-PCI FFR significantly increased the risk of TVF (adjusted hazard ratio [HR] per 0.01 FFR decrease, 1.04; 95% CI, 1.02-1.05; P < .001). The risk of cardiac death or MI also increased inversely with post-PCI FFR (adjusted HR, 1.03; 95% CI, 1.00-1.07, P = .049). These associations were consistent regardless of age, sex, the presence of hypertension or diabetes, and clinical diagnosis.

CONCLUSIONS AND RELEVANCE

Reduced FFR after DES implantation was common and associated with the risks of TVF and of cardiac death or TVMI. These results indicate the prognostic value of post-PCI physiologic assessment after DES implantation.

Prognostic Implications of Quantitative Flow Ratio-Derived Physiological 2-Dimensional Residual Disease Patterns After Stenting

BACKGROUND

Post-percutaneous coronary intervention (PCI) residual disease is associated with clinical outcomes. Nevertheless, the prognostic value of residual disease patterns remains unknown.

OBJECTIVES

This study aimed to evaluate clinical implications of 2-dimensional residual disease patterns after PCI.

METHODS

One thousand six hundred seven vessels that underwent successful PCI were included. Two-dimensional residual disease patterns were determined by visual assessment or the quantitative flow ratio (QFR)-derived pull back pressure gradient index (with a cutoff value of 0.78 to define predominant focal versus diffuse disease) and instantaneous QFR gradient per unit length (with a cutoff value of ≥0.005/mm to define a major gradient). The clinical outcome was the 2-year vessel-oriented composite outcome (VOCO).

RESULTS

Residual disease patterns were classified into 4 groups: predominant focal without and with a major gradient (group 1 [n = 1,058] and group 2 [n = 63], respectively) and predominant diffuse without and with a major gradient (group 3 [n = 318] and group 4 [n = 168], respectively). At 2 years, VOCO was lowest in group 1 (1.4% vs 5.4% in group 2 vs 4.8% in group 3 vs 8.5% in group 4, all P < 0.05), whereas there was no prognostic value for classifications by visual assessment. Physiological residual disease patterns were independently associated with VOCO and showed increased prognostic value when introduced to a model with clinical risk factors only (C index: 0.77 vs. 0.68, P = 0.008; net reclassification improvement: 0.65, P < 0.001; integrated discrimination improvement: 0.020, P < 0.001).

CONCLUSIONS

Objective analysis of post-PCI QFR pull backs using the concept of 2-dimensional residual disease patterns is feasible and superior to visual assessments. The residual disease patterns were independently associated with VOCO at 2 years.

Prognostic Implications of Prestent Pullback Pressure Gradient and Poststent Quantitative Flow Ratio in Patients Undergoing Percutaneous Coronary Intervention

Background

Coronary diffuse disease associates with poor outcomes, but little is known about its role after percutaneous coronary intervention (PCI). We aimed to investigate the prognostic implication of pre‐PCI focal or diffuse disease patterns combined with post‐PCI quantitative flow ratio (QFR).

Methods and Results

Pre‐PCI QFR derived pullback pressure gradient (PPG) (QFR‐PPG) was measured to assess physiological disease patterns for 1685 included vessels; the vessels were classified according to dichotomous pre‐PCI QFR‐PPG and post‐PCI QFR. Vessel‐oriented composite outcome, a composite of vessel‐related ischemia‐driven revascularization, vessel‐related myocardial infarction, or cardiac death at 2 years was compared among these groups. Vessels with low pre‐PCI PPG (3.9% versus 2.0%, hazard ratio [HR], 1.93; 95% CI, 1.08–3.44; P=0.02) or low post‐PCI QFR (9.8% versus 2.7%, HR, 3.78; 95% CI, 1.61–8.87; P=0.001) demonstrated higher vessel‐oriented composite outcome risk after stent implantation. Of note, despite high post‐PCI QFR achieved, vessels with low pre‐PCI QFR‐PPG presented higher risk of vessel‐oriented composite outcome than those with high pre‐PCI QFR‐PPG (3.7% versus 1.8%, HR, 2.03; 95% CI, 1.09–3.76; P=0.03) and pre‐PCI QFR‐PPG demonstrated direct prognostic effect not mediated by post‐PCI QFR. Integration of groups classified by pre‐PCI QFR‐PPG and post‐PCI QFR showed significantly higher discriminant and reclassification abilities than clinical factors (C‐index 0.77 versus 0.72, P=0.03; integrated discrimination improvement 0.93%, P=0.04; net reclassification index 0.33, P=0.02).

Conclusions

Prognostic value of pre‐PCI focal or diffuse disease patterns assessed by QFR‐PPG index was retained even after successful PCI, which is mostly explained by its direct effect that was not mediated by post‐PCI QFR. Integration of both pre‐PCI and post‐PCI physiological information can provide better risk stratification in vessels with stent implantation.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05104580.

Integrated coronary disease burden and patterns to discriminate vessels benefiting from percutaneous coronary intervention

OBJECTIVE

To evaluate the prognostic implications of atherosclerosis functional pattern on ischemia-causing vessels received percutaneous coronary intervention (PCI) or conservative treatment.

BACKGROUND

Quantitative flow ratio (QFR)-derived pullback pressure gradient (PPG) index is recently proposed to characterize atherosclerosis functional pattern, but its prognostic value remains unclear.

METHODS

QFR-derived PPG index was retrospectively calculated in patients from the PANDA III trial. Vessels with low or high PPG treated by PCI or not were compared for the risk of 2-year vessel-oriented composite outcome (VOCO), which was a composite of vessel-related ischemia-driven revascularization, vessel-related myocardial infarction, or cardiac death.

RESULTS

A total of 1444 vessels were included while 94 (6.5%) VOCOs occurred within 2 years. Among physiologically ischemic vessels (QFR ≤ 0.80) treated by PCI, those with low PPG acquired higher VOCO risk than those with high PPG (8.4% vs. 3.8%; adjusted hazard ratio [HR] 2.13, 95% confidence interval [CI] 1.18 to 3.86), and a similar VOCO risk (8.4% vs. 7.8%; adjusted HR 1.11, 95%CI 0.70-1.78) compared to those treated by conservatively. After multiple adjustment, PPG index was an independent predictor for VOCO (HR 1.30, 95% CI 1.05-1.62). The addition of PPG to the model of clinical risk factors substantially improved the predictions of VOCO (C-index 0.67 vs. 0.62, net reclassification index 0.42).

CONCLUSIONS

PCI treatment was associated with improved outcomes in vessels with high PPG, but not for those with low PPG, which acquired similar risk of VOCO compared to vessels treated conservatively. QFR-derived PPG might assist the treatment strategy selection in ischemia-causing vessels.

Physiological Distribution and Local Severity of Coronary Artery Disease and Outcomes After Percutaneous Coronary Intervention

OBJECTIVES

The aim of this study was to evaluate prognostic implications of physiological 2-dimensional disease patterns on the basis of distribution and local severity of coronary atherosclerosis determined by quantitative flow ratio (QFR) virtual pull back.

BACKGROUND

The beneficial effect of percutaneous coronary intervention (PCI) is determined by physiological distribution and local severity of coronary atherosclerosis.

METHODS

The study population included 341 patients who underwent angiographically successful PCI and post-PCI fractional flow reserve (FFR) measurement. Using pre-PCI virtual pull backs of QFR, physiological distribution was determined by pull back pressure gradient index, with a cutoff value of 0.78 to define predominant focal versus diffuse disease. Physiological local severity was assessed by instantaneous QFR gradient per unit length, with a cutoff value of ≥0.025/mm to define a major gradient. Suboptimal post-PCI physiological results were defined as both post-PCI FFR ≤0.85 and percentage FFR increase ≤15%. Clinical outcome was assessed by target vessel failure (TVF) at 2 years.

RESULTS

QFR pull back pressure gradient index was correlated with post-PCI FFR (R = 0.423; P < 0.001), and instantaneous QFR gradient per unit length was correlated with percentage FFR increase (R = 0.370; P < 0.001). Using the 2 QFR-derived indexes, disease patterns were classified into 4 categories: predominant focal disease with and without major gradient (group 1 [n = 150] and group 2 [n = 21], respectively) and predominant diffuse disease with and without major gradient (group 3 [n = 115] and group 4 [n = 55], respectively). Proportions of suboptimal post-PCI physiological results were significantly different according to the 4 disease patterns (18.7%, 23.8%, 22.6%, and 56.4% from group 1 to group 4, respectively; P < 0.001). Cumulative incidence of TVF after PCI was significantly higher in patients with predominant diffuse disease (8.1% in group 3 and 9.9% in group 4 vs 1.4% in group 1 and 0.0% in group 2; overall P = 0.024).

CONCLUSIONS

Both physiological distribution and local severity of coronary atherosclerosis could be characterized without pressure-wire pull backs, which determined post-PCI physiological results. After successful PCI, TVF risk was determined mainly by the physiological distribution of coronary atherosclerosis. (Automated Algorithm Detecting Physiologic Major Stenosis and Its Relationship With Post-PCI Clinical Outcomes [Algorithm-PCI], NCT04304677; Influence of FFR on the Clinical Outcome After Percutaneous Coronary Intervention [PERSPECTIVE], NCT01873560).

Physiologic Assessment after Coronary Stent Implantation

The presence of myocardial ischemia is a prerequisite for the benefit of coronary revascularization. In the cardiac catheterization laboratory, fractional flow reserve and non-hyperemic pressure ratios are used to define the ischemia-causing coronary stenosis, and several randomized studies showed the benefit of physiology-guided coronary revascularization. However, physiology-guided revascularization does not necessarily guarantee the relief of ischemia. Recent studies reported that residual ischemia might exist in up to 15-20% of cases after angiographically successful percutaneous coronary intervention (PCI). Therefore, post-PCI physiologic assessment is necessary for judging the appropriateness of PCI, detecting the lesions that may benefit from additional PCI, and risk stratification after PCI. This review will focus on the current evidence for post-PCI physiologic assessment, how to interpret these findings, and the future perspectives of physiologic assessment after PCI.