Coronary microcirculation assessment using functional angiography: Development of a wire-free method applicable to conventional coronary angiograms

Angiography-versus wire-based microvascular resistance index to detect coronary microvascular obstruction associated with ST-segment elevation myocardial infarction

BACKGROUND

Microvascular obstruction (MVO) measured by cardiac magnetic resonance (CMR) after ST-segment elevation myocardial infarction (STEMI) has important prognostic implications. While invasive index of microvascular resistance (IMR) have been shown to predict the occurrence and extent of MVO, the role of the angiography-based microvascular resistance (Angio-IMR) for this purpose remains unknown. The present study aims to perform a head-to-head comparison of wire-based and angiography-derived microcirculatory resistance (IMR and Angio-IMR, respectively) for the detection of MVO.

METHODS

Patients with a first STEMI and multivessel disease underwent CMR for detection of MVO, and angio-IMR and IMR measurements during PPCI and at 30 day follow up, both in STEMI culprit and non-culprit vessels.

RESULTS

58 patients were included (mean age 60.7 ± 9.9 years, 82% male). At the time of PPCI, angio-IMR and IMR exhibited significant correlation (r = 0.70, P < 0.001), and agreement (coefficient of agreement 0.58). Both indices showed good predictive value of MVO [Angio IMR: AUC 0.79 (95% CI: 0.667-0.928); IMR: AUC 0.70 (95% CI: 0.539-0.853); p = 0.15]. Angio-IMR 40 U and IMR 34 U were identified as best cut-offs for prediction of MVO. In non-culprit vessels, angio-IMR and IMR also correlated well (rho = 0.59, p < 0.001), with overall lower mean values compared to culprit vessels (Angio-IMR: 36 vs. 23; IMR: 39 vs. 22, p < 0.001 for both comparisons).

CONCLUSION

Angio-IMR constitutes a valid alternative to wire-based IMR in predicting MVO in STEMI. Angio-IMR and IMR show a good correlation in the acute and subacute STEMI phases, both in culprit and non-culprit vessels.

Microcirculatory dysfunction in hypertrophic cardiomyopathy with chest pain assessed by angiography-derived microcirculatory resistance

Chest pain, a common initial symptom in hypertrophic cardiomyopathy (HCM) patients, is closely linked to myocardial ischemia, despite the absence of significant coronary artery stenosis. This study explored microvascular dysfunction in HCM patients by employing angiography-derived microcirculatory resistance (AMR) as a novel tool for comprehensive assessment. This retrospective analysis included HCM patients with chest pain as the primary symptom and control patients without cardiac hypertrophy during the same period. The AMR was computed through angiography, providing a wire-free and adenosine-free index for evaluating microcirculatory function. Propensity score matching ensured balanced demographics between groups. This study also investigated the correlation between the AMR and clinical outcomes by utilizing echocardiography and follow-up data. After matching, 76 HCM patients and 152 controls were analyzed. While there was no significant difference in the incidence of epicardial coronary stenosis, the AMR of three epicardial coronary arteries was markedly greater in HCM patients. The criterion of an AMR ≥ 250 mmHg*s/m was that 65.7% of HCM patients experienced coronary microvascular dysfunction (CMD). Independent risk factors for CMD included increased left ventricular (LV) wall thickness (OR = 1.209, 95% CI 1.013-1.443, p = 0.036). Furthermore, an AMR_LAD ≥ 250 mmHg*s/m had an increased cumulative risk of the endpoint (log-rank p = 0.023) and was an independent risk factor for the endpoint (HR = 11.64, 95% CI 1.13-120.03, p = 0.039), providing valuable prognostic insights.

A Novel Method for Angiographic Contrast-Based Diagnosis of Stenosis in Coronary Artery Disease: In Vivo and In Vitro Analyses

BACKGROUND

The existing diagnostic methods for coronary artery disease (CAD), such as coronary angiography and fractional flow reserve (FFR), have limitations regarding their invasiveness, cost, and discomfort. We explored a novel diagnostic approach, coronary contrast intensity analysis (CCIA), and conducted a comparative analysis between it and FFR.

METHODS

We used an in vitro coronary-circulation-mimicking system with nine stenosis models representing various stenosis lengths (6, 18, and 30 mm) and degrees (30%, 50%, and 70%). The angiographic brightness values were analyzed for CCIA. The in vivo experiments included 15 patients with a normal sinus rhythm. Coronary angiography was performed, and arterial movement was tracked, enabling CCIA derivation. The CCIA values were compared with the FFR (n = 15) and instantaneous wave-free ratio (iFR; n = 11) measurements.

RESULTS

In vitro FFR showed a consistent trend related to the length and severity of stenosis. The CCIA was related to stenosis but had a weaker correlation with length, except for with 70% stenosis (6 mm: 0.82 ± 0.007, 0.68 ± 0.007, 0.61 ± 0.004; 18 mm: 0.78 ± 0.052, 0.69 ± 0.025, 0.44 ± 0.016; 30 mm: 0.80 ± 0.018, 0.64 ± 0.006, 0.40 ± 0.026 at 30%, 50%, and 70%, respectively). In vitro CCIA and FFR were significantly correlated (R = 0.9442, p < 0.01). The in vivo analysis revealed significant correlations between CCIA and FFR (R = 0.5775, p < 0.05) and the iFR (n = 11, R = 0.7578, p < 0.01).

CONCLUSIONS

CCIA is a promising alternative for diagnosing stenosis in patients with CAD. The initial in vitro validation and in vivo confirmation in patients demonstrate the feasibility of applying CCIA during coronary angiography. Further clinical studies are warranted to fully evaluate the diagnostic accuracy and potential impact of CCIA on CAD management.

Coronary microvascular dysfunction

Coronary microvascular dysfunction (CMD) is a key mechanism underlying ischemic heart disease (IHD), yet its diagnosis and treatment remain challenging. This article presents a comprehensive overview of CMD research, covering its pathogenesis, diagnostic criteria, assessment techniques, risk factors, and therapeutic strategies. Additionally, it highlights the prospects for future CMD research. The article aims at advocating early and effective intervention for CMD and improving the prognosis of IHD.

Ability of the coronary angiography-derived index of microcirculatory resistance to predict microvascular obstruction in patients with ST-segment elevation

Background

The coronary angiography-derived index of microvascular resistance (caIMR) correlates well with the index of microcirculatory resistance (IMR), which predicts microvascular obstruction (MVO). However, the relationship between caIMR and MVO remains unclear.

Aim

To evaluate the predictive ability of caIMR of MVO after ST-segment elevation myocardial infarction (STEMI).

Methods

CaIMR was calculated using computational flow and pressure simulation in patients with STEMI in whom MVO status had been assessed by cardiac magnetic resonance (CMR) after successful primary percutaneous intervention at Peking University First Hospital between December 2016 and August 2019. The clinical, biochemical, echocardiographic, and CMR characteristics were assessed according to MVO status. The predictive value of the clinical parameters and caIMR was evaluated.

Results

Fifty-three eligible patients were divided into an MVO group (n = 32) and a no-MVO group (n = 21). The caIMR tended to be higher in the MVO group (41.6 U vs. 30.1 U; p = 0.136). CaIMR and peak cardiac troponin-I (cTNI) were independent predictors of MVO (per 1-U increment in caIMR: odds ratio [OR] 1.044, 95% confidence interval [CI] 1.004-1.086, p = 0.030; per 1 ng/L increase in peak cTNI: OR 1.018, 95% CI 1.003-1.033, p = 0.022). In receiver-operating characteristic curve analysis, when a cut-off value of 45.17 U was used, caIMR had some ability to predict MVO (area under the curve 0.622, 95% CI 0.478-0.752, p = 0.127).

Conclusions

CaIMR and peak cTNI were independent predictors of short-term MVO in patients with STEMI who had undergone successful primary percutaneous coronary intervention and may help to identify those at high risk of MVO.

Diagnostic and prognostic value of angiography-derived index of microvascular resistance: a systematic review and meta-analysis

Background

The angiography-derived index of microvascular resistance (A-IMR) is a novel tool for diagnosing coronary microvascular dysfunction (CMD) addressing limitation of unavailability. However, the clinical value of A-IMR remains controversial.

Methods

A systematic review and meta-analysis was conducted. PubMed, EMBASE, Cochrane Library and Web of Science were searched for relevant studies. Studies that reported estimates of A-IMR's diagnostic accuracy (with thermodilution-based IMR as the reference test) and/or predictions of adverse cardiovascular events were selected. Pooled sensitivity, specificity, area under the summary receiver operating characteristic curve (sROC) were calculated to measure diagnostic performance; pooled hazard/risk ratio (HR/RR) and 95% confidence interval (95% CI) of major adverse cardiovascular events (MACE) or other independent adverse events were calculated to measure prognostic effect. This study was registered with PROSPERO (CRD42023451884).

Results

A total of 12 diagnostic studies pooling 1,642 vessels and 12 prognostic studies pooling 2,790 individuals were included. A-IMR yielded an area under sROC of 0.93 (95% CI: 0.91, 0.95), a pooled sensitivity of 0.85 (95% CI: 0.79, 0.89) and a pooled specificity of 0.89 (95% CI: 0.83, 0.93) for the diagnosis of CMD. CMD diagnosed using A-IMR was associated with higher risks of MACE (HR, 2.73, 95% CI: 2.16, 3.45), CV death (RR, 2.39, 95% CI: 1.49, 3.82) and heart failure hospitalization (HR, 2.30, 95% CI: 1.53, 3.45).

Conclusion

A-IMR demonstrated high diagnostic accuracy for CMD and showed a strong prognostic capability in predicting the risk of adverse CV outcomes.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023451884, PROSPERO (CRD42023451884).

Comprehensive Angiography-Derived Functional Assessment of Epicardial and Microvascular Coronary Disease. Correlation With Non-invasive Myocardial Stress Imaging

Coronary angiography (CA) is poorly correlated with non-invasive myocardial stress imaging (NSI) and myocardial ischemia is often observed in patients with unobstructed coronary arteries. Moreover, the diagnostic performance of combined epicardial and microcirculatory angiography-derived physiological assessment and its correlation with NSI remains unknown. A total of 917 coronary vessels in 319 patients who underwent both CA and NSI were included in this multicenter observational retrospective analysis. Quantitative flow ratio (QFR) and angiography-derived index of microcirculatory resistance (IMRangio) analyses were performed to estimate coronary epicardial and microcirculatory function respectively. NSI demonstrated evidence of myocardial ischemia in 76% of the cases. IMRangio (36 [22 to 50] vs 29 [21 to 41], p <0.001) was significantly higher and QFR (0.92 [0.78 to 0.99] vs 0.97 [0.91 to 0.99], p <0.001) was significantly lower in vessels subtending ischemic territories. Overall, the diagnostic accuracy of QFR was moderate (area under the curve of receiver operating characteristic [AUCROC] 0.632 [95% confidence interval [CI] 0.589 to 0.674], p <0.0001) but it was higher in patients with normal microcirculatory function (AUCROC = 0.726 [95% CI 0.669 to 0.784], p <0.0001, p Value for AUCROC comparison = 0.009). Combined QFR/IMRangio assessment provided incremental diagnostic performance compared with the evaluation of epicardial or microcirculatory districts in isolation (p Value for AUC comparison <0.0001) and it was able to identify the predominant mechanism of myocardial ischemia in 77% of the patients with positive NSI. Our study suggests the value of a combined angiography-derived assessment of epicardial and microvascular function for the definition of the predominant mechanism of myocardial ischemia in patients with suspected coronary artery disease.

Consensus document on the clinical application of invasive functional coronary angiography from the Japanese Association of Cardiovascular Intervention and Therapeutics

Invasive functional coronary angiography (FCA), an angiography-derived physiological index of the functional significance of coronary obstruction, is a novel physiological assessment tool for coronary obstruction that does not require the utilization of a pressure wire. This technology enables operators to rapidly evaluate the functional relevance of coronary stenoses during and even after angiography while reducing the burden of cost and complication risks related to the pressure wire. FCA can be used for treatment decision-making for revascularization, strategy planning for percutaneous coronary intervention, and procedure optimization. Currently, various software-computing FCAs are available worldwide, with unique features in their computation algorithms and functions. With the emerging application of this novel technology in various clinical scenarios, the Japanese Association of Cardiovascular Intervention and Therapeutics task force was created to outline expert consensus on the clinical use of FCA. This consensus document advocates optimal clinical applications of FCA according to currently available evidence while summarizing the concept, history, limitations, and future perspectives of FCA along with globally available software.

Application of AMR in evaluating microvascular dysfunction after ST-elevation myocardial infarction

BACKGROUND

A guidewire-free angiography-derived microcirculatory resistance (AMR) derived from Quantitative flow ratio (QFR) exhibits good diagnostic accuracy for assessing coronary microvascular dysfunction (CMD), but there are no relevant studies supporting the specific application of AMR in patients with ST-elevation myocardial infarction (STEMI). The study aims to evaluate CMD in patients with STEMI using the AMR index.

METHODS

This study included patients with STEMI who underwent percutaneous coronary intervention (PCI) from June 1, 2020 to September 28, 2021. All patients were divided into two groups: the CMD (n = 215) and non-CMD (n = 291) groups. After matching, there were 382 patients in both groups.1-year follow-up major adverse cardiac events (MACEs) were evaluated.

RESULTS

After matching, the primary endpoint was achieved in 41 patients (10.7%), with 27 and 14 patients in the CMD and non-CMD groups, respectively (HR 1.954 [95% CI 1.025-3.726]; 14.1% versus 7.3%, p = .042). Subgroup analysis revealed that 18 patients (4.7%) were readmitted for heart failure, with 15 and 3 in the CMD and non-CMD groups, respectively (HR 5.082 [95% CI 1.471-17.554]; 7.9% versus 1.6%, p = .010). Post-PCI AMR ≥ 250 was significantly associated with a higher risk of the primary endpoint and was its independent predictor (HR 2.265 [95% CI 1.136-4.515], p = .020).

CONCLUSION

The retrospective use of AMR with a cutoff value of ≥250 after PCI in patients with STEMI can predict a significant difference in the 1-year MACE rates when compared with a propensity score-matched group with normal AMR.

Angiography-based coronary microvascular assessment with and without intracoronary pressure measurements: a systematic review

BACKGROUND

In recent years, several indices have been proposed for quantifying coronary microvascular resistance. We intended to conduct a comprehensive review that systematically evaluates indices of microvascular resistance derived from angiography.

OBJECTIVE

The objective of this study was to identify and analyze angiography-derived indices of microvascular resistance that have been validated against an invasive reference method. We aimed to compare their limits of agreement with their reference methods and explore their advantages and inherent limitations.

METHODS AND RESULTS

We searched PubMed from inception until 2022 for studies on different techniques for quantifying microvascular resistance. Seven studies met the inclusion criteria. Five studies included techniques that applied calculations based solely on invasive angiography, and were validated against invasively measured thermodilution-derived index of microvascular resistance. The remaining two studies combined angiography with invasively measured intracoronary pressure data, and were validated against invasive Doppler measurements. We converted the ± 1.96 standard deviation limits of agreement with the reference method from the seven studies into percentages relative to the cut-off value of the reference method. The lower limits of agreement for angiography-based methods ranged from - 122 to - 60%, while the upper limits ranged from 74 to 135%. The range of the limits of agreement was considerably lower for the two combined angiography- and pressure-based methods, standing at - 52 to 60% and - 25 to 27%.

CONCLUSION

Our findings suggest that combined angiography- and pressure-based methods provide a more reliable assessment of microvascular resistance compared to methods relying solely on angiography. Central illustration. Comparative assessment of image-based methods quantifying microvascular resistance with and without intracoronary pressure measurements. Angiography-based methods rely on angiography alone to calculate the microvascular resistance by utilizing angiographic frame counting to extrapolate coronary flow (Q) and subsequently deriving distal coronary pressure using fluid dynamic equations. Combined angiography- and pressure-based methods utilize invasive intracoronary pressure gradients measured during rest and maximal vasodilation to determine coronary flow in their calculation of microvascular resistance. The combined methods showed more acceptable levels of agreement with their reference methods compared to angiography-based methods alone.

The role of imaging in the selection of patients for HFpEF therapy

Heart failure with preserved ejection fraction (HFpEF) traditionally has been characterized as a form of heart failure without therapeutic options, in particular with a lack of response to the established therapies of heart failure with reduced ejection fraction (HFrEF). However, this is no longer true. Besides physical exercise, risk factor modification, aldosterone blocking agents, and sodium-glucose cotransporter 2 inhibitors, specific therapies are emerging for specific HFpEF etiologies, such as hypertrophic cardiomyopathy or cardiac amyloidosis. This development justifies increased efforts to arrive at specific diagnoses within the umbrella of HFpEF. Cardiac imaging plays by far the largest role in this effort and is discussed in the following review.

Coronary microvascular dysfunction is a hallmark of all subtypes of MINOCA

INTRODUCTION

Myocardial infarction without obstructive coronary artery disease (MINOCA) is a heterogeneous clinical condition presenting with myocardial necrosis not due to an obstruction of a major coronary artery. Recently, a relevant role of coronary microvascular dysfunction (CMD) in the pathogenesis of MINOCA has been suggested; however, data on this are scarce. Particularly, it is unclear if CMD is equally present in all subtypes of MINOCA or differentially identifies one or more of these conditions. Therefore, the aim of this study was to assess CMD in all three coronary vessels of MINOCA patients, relating it with the clinical subtype.

METHODS

We retrospectively assessed coronary microvascular function in all three coronary territories by means of angiography-based index of microvascular resistance (aIMR) in 92 patients (64 with working diagnosis of MINOCA, 28 control patients). To further assess the association of CMD with MINOCA subtypes, MINOCA patients were subdivided according to clinical data in coronary cause (n = 13), takotsubo (n = 13), infiltrative or inflammatory cardiomyopathy (n = 9) or unclear (n = 29).

RESULTS

Patients with working diagnosis of MINOCA showed a significantly elevated average aIMR compared to control patients (30.5 ± 7.6 vs. 22.1 ± 5.9, p < 0.001) as a marker of a relevant CMD; these data were consistent in all vessels. Among MINOCA subtypes, no significant difference in average aIMR could be detected between patients with coronary cause (33.2 ± 6.6), takotsubo cardiomyopathy (29.2 ± 6.9), infiltrative or inflammatory cardiomyopathy (28.1 ± 6.8) or unclear cause (30.6 ± 8.5; p = 0.412). Interestingly, aIMR was significantly elevated in the coronary vessel supplying the diseased myocardium compared with other vessels (31.9 ± 11.4 vs. 27.8 ± 8.2, p = 0.049).

CONCLUSION

Coronary microvascular dysfunction is a hallmark of all MINOCA subtypes. This study adds to the pathophysiological understanding of MINOCA and sheds light into the role of CMD in MINOCA.

Coronary angiography-derived index for assessing microcirculatory resistance in patients with non-obstructed vessels: The FLASH IMR study

BACKGROUND

Assessing index of microcirculatory resistance (IMR) is customarily performed using intracoronary wires fitted with sensors by at least 3 intracoronary injections of 3 to 4 mL of room-temperature saline during sustained hyperemia, which is time- and cost-consuming.

METHODS

The FLASH IMR study is a prospective, multicenter, randomized study to assess the diagnostic performance of coronary angiography-derived IMR (caIMR) in patients with suspected myocardial ischemia with nonobstructive coronary arteries using wire-based IMR as a reference. The caIMR was calculated by an optimized computational fluid dynamics model simulating hemodynamics during diastole based on coronary angiograms. TIMI frame count and aortic pressure were included in computation. caIMR was determined onsite in real time and compared blind to wire-based IMR by an independent core laboratory, using wire-based IMR ≥25 units as indicative of abnormal coronary microcirculatory resistance. The primary endpoint was the diagnostic accuracy of caIMR, using wire-based IMR as a reference, with a pre-specified performance goal of 82%.

RESULTS

A total of 113 patients underwent paired caIMR and wire-based IMR measurements. Order of performance of tests was based on randomization. Diagnostic accuracy, sensitivity, specificity, positive and negative predictive values of caIMR were 93.8% (95% CI: 87.7%-97.5%), 95.1% (95% CI: 83.5%- 99.4%), 93.1% (95% CI: 84.5%-97.7%), 88.6% (95% CI: 75.4%-96.2%) and 97.1% (95% CI: 89.9%-99.7%). The receiver-operating curve for caIMR to diagnose abnormal coronary microcirculatory resistance had area under the curve of 0.963 (95% CI: 0.928-0.999).

CONCLUSIONS

Angiography-based caIMR has a good diagnostic yield with wire-based IMR.

CLINICALTRIALS

GOV IDENTIFIER

NCT05009667.

Coronary Microvascular Disease in Contemporary Clinical Practice

Coronary microvascular disease (CMD) causes myocardial ischemia in a variety of clinical scenarios. Clinical practice guidelines support routine testing for CMD in patients with ischemia with nonobstructive coronary artery disease. Invasive testing to identify CMD requires Doppler or thermodilution measures of flow to determine the coronary flow reserve and measures of microvascular resistance. Acetylcholine coronary reactivity testing identifies concomitant endothelial dysfunction, microvascular spasm, or epicardial coronary spasm. Comprehensive testing may improve symptoms, quality of life, and patient satisfaction by establishing a diagnosis and guiding-targeted medical therapy and lifestyle measures. Beyond ischemia with nonobstructive coronary artery disease, testing for CMD may play a role in patients with acute myocardial infarction, angina following coronary revascularization, heart failure with preserved ejection fraction, Takotsubo syndrome, and after heart transplantation. Additional education and provider awareness of CMD and its role in cardiovascular disease is needed to improve patient-centered outcomes of ischemic heart disease.

Angiography-Derived and Sensor-Wire Methods to Assess Coronary Microvascular Dysfunction in Patients With Acute Myocardial Infarction

ST-segment elevation myocardial infarction (STEMI) treatment with primary percutaneous coronary intervention has dramatically impacted prognosis. However, despite satisfactory angiographic result, occurrence or persistence of coronary microvascular dysfunction after revascularization still affects long-term outcomes. The diagnostic and therapeutic value of understanding the status of coronary microcirculation is gaining attention in the cardiology community. However, current methods to assess microvascular function (namely, cardiac magnetic resonance and invasive wire-based coronary physiology) remain, at least in part, limited by technical and logistic aspects. On the other hand, angiography-based indices of microcirculatory resistance are emerging as valid and user-friendly tools with potential impact on prognostic stratification of patients with STEMI. This review provides an overview about conventional and novel methods to assess coronary microvascular dysfunction in patients with STEMI. The authors also provide a proposed procedural algorithm to facilitate optimal use of wire-based and angiography-based indices in the acute setting of STEMI.

Angiography-derived assessment of coronary microcirculatory resistance in patients with suspected myocardial ischaemia and non-obstructive coronary arteries

BACKGROUND

Myocardial ischaemia with non-obstructive coronary arteries (INOCA) represents a challenging and frequent, but largely underdiagnosed, condition.

AIMS

We aimed to investigate the feasibility and diagnostic value of angiography-derived coronary microcirculatory resistance in patients with INOCA syndrome.

METHODS

This is an investigator-driven, prospective and blinded study. The diagnostic yield of angiography-derived index of coronary microcirculatory resistance (angio-IMR) was investigated against thermodilution-derived IMR (thermo-IMR) in patients with clinically indicated coronary angiography due to suspected myocardial ischaemia and angiographically normal or non-obstructive coronary arteries. The angio-IMR was derived from resting angiograms (contrast-flow angio-IMR [cAngio-IMR]) by an expert analyst blinded to the thermo-IMR. An independent, blinded, physiology core laboratory analysed the raw intracoronary physiology data and provided the final thermo-IMR values.

RESULTS

A total of 104 patients (108 coronary vessels) were analysed after fulfilling predefined inclusion criteria. Most patients were female (67%). Obstructive epicardial disease was angiographically (percent diameter stenosis <50%) and physiologically (fractional flow reserve>0.80) ruled out in all cases. Median thermo-IMR and cAngio-IMR were 16.6 (12.7, 23.0) and 16.8 (12.8, 23.1) units, respectively (median difference -0.31, 95% confidence interval: -1.53 to 1.00; p=0.654). cAngio-IMR showed good correlation (Pearson coefficient 0.76; p<0.001), agreement (mean bias 0.4), discriminatory power (area under the curve from the receiver operator characteristics 0.865; p<0.001) and accuracy (85%), compared to thermo-IMR (≥25 U).

CONCLUSIONS

Evaluating coronary microcirculatory resistance in patients with INOCA syndrome using cAngio-IMR is feasible and accurate. By circumventing the need of coronary instrumentation and hyperaemic drugs, this method may facilitate the assessment of coronary microcirculatory resistance in patients with suspected INOCA.

CLINICALTRIALS

gov: NCT04827498.

Angiography-derived index of microvascular resistance in takotsubo syndrome

Coronary microvascular dysfunction (CMD) has been proposed as a key driver in the etiopathogenesis of Takotsubo syndrome (TTS), likely related to an "adrenergic storm" upon a susceptible microvascular circulation. The aim of our manuscript was to assess CMD in patients with TTS through the computation of the angiography-derived index of microcirculatory resistance (IMR) and its correlation with clinical presentation. Coronary angiograms of 41 consecutive TTS patients were retrospectively analyzed to derive angiography-based indices of CMD. Three indices (NH-IMRangio, AngioIMR and A-IMR) were calculated based on quantitative flow ratio. CMD was defined as an IMRangio value ≥ 25 units. The correlation between CMD and clinical presentation was then assessed. Median age was 76 years, 85.7% were women and mean left ventricular ejection fraction (LVEF) at first echocardiogram was 41.2%. Angiography-derived IMR was higher in left anterior descending artery (LAD) than circumflex and right coronary artery with either NH-IMRangio (53.9 ± 19.8 vs 35.8 ± 15.4 vs 40.8 ± 18.5, p-value < 0.001), AngioIMR (47.2 ± 17.3 vs 31.8 ± 12.2 vs 37.3 ± 13.7, p-value < 0.001) or A-IMR (52.7 ± 19 vs 36.1 ± 14.1 vs 41.8 ± 16.1, p-value < 0.001). All patients presented CMD with angiography-derived IMR ≥ 25 in at least one territory with each formula. Angiography-derived IMR in LAD territory was significantly higher in patients presenting with LVEF impairment (≤ 40%) than in those with preserved ventricular global function (NH-IMRangio: 59.3 ± 18.1 vs 46.3 ± 16.0 p-value = 0.030; AngioIMR: 52.9 ± 17.8 vs 41.4 ± 14.2, p-value = 0.037; A-IMR: 59.2 ± 18.6 vs 46.3 ± 17.0, p-value = 0.035). CMD assessed with angiography-derived IMR is a common finding in TTS and it is inversely correlated with LV function. The available formulas have a substantial superimposable diagnostic performance in assessing coronary microvascular function.

Coronary microvascular dysfunction as assessed by angiography-derived index of microvascular resistance co-localizes with and may explain the presence of ischemia in stress-cardiac magnetic resonance imaging in the absence of coronary artery disease

Introduction

Ischemia with no obstructive coronary disease (INOCA) is a frequent phenomenon in the cath lab. A possible cause is coronary microvascular dysfunction (CMD), which may be assessed by invasive testing with possible complications; therefore, less invasive approaches have emerged, such as the angiography-derived index of microvascular resistance (aIMR). The aim of our study was to investigate the association of single-vessel aIMR as a measure of CMD with areas of INOCA in stress testing.

Methods

We measured aIMR in 286 vessels from 102 patients undergoing both stress cMRI and coronary angiography. Groups were (a) INOCA group (93 vessels, 32 patients); (b) coronary artery disease (CAD) control group (116 vessels, 42 patients) with ischemia due to relevant stenosis; and (c) control group (77 vessels, 28 patients) without ischemia or relevant stenosis.

Results

INOCA patients presented higher mean aIMR (28.3 ± 5.7) compared to both CAD patients (17.4 ± 5.7, p < 0.001) and controls (22.1 ± 5.9, p < 0.001). Furthermore, in INOCA patients aIMR was significantly increased (33.0 ± 8.1 vs. 25.8 ± 6.3, p = 0.021) in vessels with vs. without ischemia. Single vessel aIMR presented a very good diagnostic efficiency in detecting INOCA [AUC 0.865 (0.804-0.925), optimal cut-off 27.1, p < 0.001].

Conclusion

CMD, as assessed by 3-vessel aIMR, co-localizes with and may explain the presence of ischemia in stress-cMRI in INOCA.

Contemporary and future invasive coronary vasomotor function testing and treatment in patients with ischaemia with no obstructive coronary arteries

In the current review, we emphasize the importance of diagnostics and therapy in patients with ischaemia with no obstructive coronary arteries (INOCA). The importance of the diagnostic coronary function test (CFT) procedure is described, including future components including angiography-derived physiology and invasive continuous thermodilution. Furthermore, the main components of treatment are discussed. Future directions include the national registration ensuring a high quality of INOCA care, besides a potential source to improve our understanding of pathophysiology in the various phenotypes of coronary vascular dysfunction, the diagnostic CFT procedure, and treatment.

In Vivo Validation of a Novel Computational Approach to Assess Microcirculatory Resistance Based on a Single Angiographic View

(1) Background: In spite of the undeniable clinical value of the index of microvascular resistance (IMR) in assessing the status of coronary microcirculation, its use globally remains very low. The aim of this study was to validate the novel single-view, pressure-wire- and adenosine-free angiographic microvascular resistance (AMR) index, having the invasive wire-based IMR as a reference standard. (2) Methods: one hundred and sixty-three patients (257 vessels) were investigated with pressure wire-based IMR. Microvascular dysfunction (CMD) was defined by IMR ≥ 25. AMR was independently computed from the diagnostic coronary angiography in a blinded fashion. (3) Results: AMR demonstrated a good correlation (r = 0.83, p < 0.001) and diagnostic performance (AUC 0.94; 95% CI: 0.91 to 0.97) compared with wire-based IMR. The best cutoff value for AMR in determining IMR ≥ 25 was 2.5 mmHg*s/cm. The overall diagnostic accuracy of AMR was 87.2% (95% CI: 83.0% to 91.3%), with a sensitivity of 93.5% (95% CI: 87.0% to 97.3%), a specificity of 82.7% (95% CI: 75.6% to 88.4%), a positive predictive value of 79.4% (95% CI: 71.2% to 86.1%) and a negative predictive value of 94.7% (95% CI: 89.3% to 97.8%). No difference in terms of CMD rate was described among different clinical presentations. (4) Conclusions: AMR derived solely from a single angiographic view is a feasible computational alternative to pressure wire-based IMR, with good diagnostic accuracy in assessing CMD.

Coronary functional assessment in non-obstructive coronary artery disease: Present situation and future direction

Non-obstructive coronary artery disease (CAD), which is defined as coronary stenosis <50%, has been increasingly recognized as an emerging entity in clinical practice. Vasomotion abnormality and coronary microvascular dysfunction are two major mechanisms contributing to the occur of angina with non-obstructive CAD. Although routine coronary functional assessment is limited due to several disadvantages, functional evaluation can help to understand the pathophysiological mechanism and/or to exclude specific etiologies. In this review, we summarized the potential mechanisms involved in ischemia with non-obstructive coronary arteries (INOCA) and myocardial infarction with non-obstructive coronary arteries (MINOCA), the two major form of non-obstructive CAD. Additionally, we reviewed currently available functional assessment indices and their use in non-obstructive CAD. Furthermore, we speculated that novel technique combined anatomic and physiologic parameters might provide more individualized therapeutic choice for patients with non-obstructive CAD.

Angiography derived assessment of the coronary microcirculation: is it ready for prime time?

INTRODUCTION

Non-obstructive coronary arteries (NOCA) are present in 39.7% to 62.4% of patients who undergo elective angiography. Coronary microcirculation (<400 µm) is not visible on angiography therefore functional assessment, invasive or non-invasive plays a prior role to help provide a more personalized diagnosis of angina.

AREA COVERED

In this review, we revise the pathophysiology, clinical importance and invasive assessment of the coronary microcirculation, and discuss angiography-derived indices of microvascular resistance. A comprehensive literature review over four decades is also undertaken.

EXPERT OPINION

The coronary microvasculature plays an important role in flow autoregulation and metabolic regulation. Invasive assessment of microvascular resistance is a validated modality with independent prognostic value, nevertheless, its routine application is hampered by the requirement of intravascular instrumentation and hyperaemic agents. The angiography-derived index of microvascular resistance has emerged as a promising surrogate in pilot studies, however, more data are needed to validate and compare the diagnostic and prognostic accuracy of different equations as well as to illustrate the relationship between angiography-derived parameters for epicardial coronary arteries and those for the microvasculature.

The Coronary Angiography-Derived Index of Microcirculatory Resistance Predicts Left Ventricular Performance Recovery in Patients with ST-Segment Elevation Myocardial Infarction

Objectives

The present study is designed to investigate the impact of coronary angiography-derived index of microcirculatory resistance (caIMR) on left ventricular performance recovery.

Background

IMR has been established as a gold standard for coronary microvascular assessment and a predictor of left ventricular recovery after ST-segment elevation myocardial infarction (STEMI). CaIMR is a novel and accurate alternative of IMR.

Methods

The present study retrospectively included 80 patients with STEMI who underwent primary percutaneous coronary intervention (PCI). We offline performed the post-PCI caIMR analysis of the culprit vessel. Echocardiography was performed within the first 24 hours and at 3 months after the index procedure. Left ventricular recovery was defined as the change in left ventricular ejection fraction (LVEF) more than zero.

Results

The mean age of the patients was 58.0 years with 80.0% male. The average post-PCI caIMR was 43.2. Overall left ventricular recovery was seen in 41 patients. Post-PCI caIMR (OR: 0.948, 95% CI: 0.916–0.981, p = 0.002), left anterior descending as the culprit vessel (OR: 3.605, 95% CI: 1.23–10.567, p = 0.019), and male (OR: 0.254, 95% CI: 0.066–0.979, p = 0.047) were independent predictors of left ventricular recovery at 3 months follow-up. A predictive model was established with the best cutoff value for the prediction of left ventricular recovery 2.33 (sensitivity 0.610, specificity 0.897, and area under the curve 0.765). In patients with a predictive model score less than 2.33, the LVEF increased significantly at 3 months.

Conclusions

The post-PCI caIMR can accurately predict left ventricular functional recovery at 3 months follow-up in patients with STEMI treated by primary PCI, supporting its use in clinical practice.

Angiography-derived versus invasively-determined index of microcirculatory resistance in the assessment of coronary microcirculation: A systematic review and meta-analysis

BACKGROUND

The index of microvascular resistance (IMR) is an established tool to assess the status of coronary microcirculation. However, the need for a pressure wire and hyperemic agents have limited its routine use and have led to the development of angiography-derived pressure-wire-free methods (angiography-derived IMR [IMRAngio]). In this review and meta-analysis, we aim to assess the global diagnosis accuracy of IMRAngio versus IMR.

METHODS

A systematic review of the literature was performed. Studies directly evaluating IMRAngio versus IMR were considered eligible. Pooled values of diagnostic test and summary receiver operator curve were calculated.

RESULTS

Seven studies directly comparing IMRAngio versus IMR were included (687 patients; 807 vessels). Pooled sensitivity, specificity, +likelihood ratio (LR), and -LR were 82%, 83%, 4.5, and 0.26 respectively. Pooled accuracy was 83% while pooled positive predictive value and negative predictive value were 76% and 85%, respectively. Comparable results were obtained when analyzing by clinical scenario (acute and nonacute coronary syndromes).

CONCLUSION

IMRAngio shows a good diagnostic performance for the prediction of abnormal IMR.

Angiography-derived physiology guidance vs usual care in an All-comers PCI population treated with the healing-targeted supreme stent and Ticagrelor monotherapy: PIONEER IV trial design

BACKGROUND

Current ESC guidelines recommend the use of intra-coronary pressure guidewires for functional assessment of intermediate-grade coronary stenoses. Angiography-derived quantitative flow ratio (QFR) is a novel method of assessing these stenoses, and guiding percutaneous coronary intervention (PCI).

METHODS/DESIGN

The PIONEER IV trial is a prospective, all-comers, multi-center trial, which will randomize 2,540 patients in a 1:1 ratio to PCI guided by angiography-derived physiology or usual care, with unrestricted use in both arms of the Healing-Targeted Supreme sirolimus-eluting stent (HT Supreme). The stent's fast, biologically healthy, and robust endothelial coverage allows for short dual-antiplatelet therapy (DAPT); hence the antiplatelet regimen of choice is 1-month DAPT, followed by ticagrelor monotherapy. In the angiography-derived physiology guided arm, lesions will be functionally assessed using on-line QFR, with stenting indicated in lesions with a QFR ≤0.80. Post-stenting, QFR will be repeated in the stented vessel(s), with post-dilatation or additional stenting recommended if the QFR<0.91 distal to the stent, or if the delta QFR (across the stent) is >0.05. Usual care PCI is performed according to standard clinical practice. The primary endpoint is a non-inferiority comparison of the patient-oriented composite endpoint (POCE) of all-cause death, any stroke, any myocardial infarction, or any clinically, and physiologically driven revascularization with a non-inferiority risk-difference margin of 3.2%, at 1-year post-procedure. Clinical follow-up will be up to 3 years.

SUMMARY

The PIONEER IV trial aims to demonstrate non-inferiority of QFR-guided PCI to usual care PCI with respect to POCE at 1-year in patients treated with HT Supreme stents and ticagrelor monotherapy.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov UNIQUE IDENTIFIER: NCT04923191 CLASSIFICATIONS: Interventional Cardiology.

Diagnostic performance and prognostic impact of coronary angiography-based Index of Microcirculatory Resistance assessment: A systematic review and meta-analysis

BACKGROUND

The Index of Microcirculatory Resistance (IMR), measured with a pressure-thermistor tipped coronary guidewire has been established as a gold standard for coronary microvascular assessment. Angiography-based IMR (angio-IMR) is a novel method to derive IMR without intracoronary instrumentation or the need for adenosine.

METHODS

PubMed and Embase databases were systemically searched in November 2021 for studies that measured angio-IMR. The primary outcomes were pooled sensitivity and specificity as well as the area under the curve (AUC) of the summary receiver operating characteristic curve using IMR as a reference standard.

RESULTS

A total of 129 records were initially identified and 8 studies were included in the final analysis. Overall, 1653 lesions were included in this study, of which 733 were in patients presenting with ST-segment elevation myocardial infarction. Angio-IMR yielded high diagnostic performance predicting wire-based IMR with pooled sensitivity = 0.81 (95% confidence interval: 0.76, 0.85), specificity = 0.80 (0.72, 0.86), and AUC = 0.86 (0.82, 0.88), which was similar irrespective of patient presentation. When the clinical outcome was compared between high versus low angio-IMR in patients presenting with myocardial infarction, high angio-IMR predicted an increased risk of major adverse cardiac events (MACE).

CONCLUSION

Our study found that coronary angio-IMR has relatively high diagnostic performance as well as prognostic values predicting MACE, supporting its use in clinical practice.

Coronary Microvascular Dysfunction in Takotsubo Syndrome Assessed by Angiography-Derived Index of Microcirculatory Resistance: A Pressure-Wire-Free Tool

Background: Coronary microvascular dysfunction (CMD) has been proposed as a key mechanism in Takotsubo syndrome (TTS). The non-hyperaemic angiography-derived index of microcirculatory resistance (NH-IMRangio) has been validated as a pressure-wire-free tool for the assessment of coronary microvasculature. We aimed to study the presence of CMD in TTS patients and its association with levels of cardiac biomarkers and systolic dysfunction patterns. Methods: We recruited 181 consecutive patients admitted for TTS who underwent cardiac angiography at a tertiary center from January 2014 to January 2021. CMD was defined as an NH-IMRangio ≥ 25. Plasma levels of NT-proBNP, high-sensitive cardiac troponin T (hs-cTnT) and the left ventricular ejection fraction (LVEF) by echocardiography were measured at admission. Results: Mean age was 75.3 years, 83% were women and median LVEF was 45%. All patients presented CMD (NH-IMRangio ≥ 25) in at least one epicardial coronary artery. The left anterior descending artery (LAD) showed higher median NH-IMRangio values than left circumflex (LCx) and right coronary arteries (RCA) (44.6 vs. 31.3 vs. 36.1, respectively; p < 0.001). NH-IMRangio values differed among ventricular contractility patterns in the LAD and RCA (p = 0.0152 and 0.0189, respectively) with the highest values in the mid-ventricular + apical and mid-ventricular + basal patterns. NT-proBNP levels, but not high-sensitive cardiac troponin T (hs-cTnT), were correlated with both the degree and the extent of CMD in patients with TTS. Lower LVEF was also associated with higher NH-IMRangio values. Conclusions: CMD is highly prevalent in patients admitted for TTS and is associated with both a higher degree of systolic dysfunction and higher BNP levels, but not troponin.

Angiography-based estimation of coronary physiology: A frame is worth a thousand words

Cumulative evidence has shown that coronary revascularization should be guided by functional significance of coronary lesions. Fractional flow reserve (FFR) is the gold standard for assessment of hemodynamic significance of coronary stenosis and FFR-guided percutaneous coronary intervention has improved clinical outcomes in patients with coronary artery disease. However, limitations of FFR such as increased operational time and cost, requirement of pressure wire and adenosine and technical difficulties have led to significant underutilization of the method in clinical practice. In the last few years, several methods of FFR estimation based on coronary angiography images have emerged to overcome invasive FFR limitations. The common elements of the novel indices include a 3D anatomical reconstruction of coronary vessels by angiographic projections and various approaches to fluid dynamics computation. Angiography-derived FFR methods have shown high diagnostic accuracy compared to invasive FFR. Although there are promising results regarding their prognostic role, large randomized trials evaluating clinical outcomes are lacking. The aim of this review is to present currently available angiography-derived FFR indices and highlight their differences, advantages, disadvantages and potential clinical implications.