Deferred revascularization in diabetic patient according to combined invasive functional and intravascular imaging data: A case report

BACKGROUND

Invasive functional evaluation by fractional flow reserve (FFR) is considered as a gold standard for the evaluation of intermediate coronary stenosis. However, in patients with diabetes due to accelerated progression of atherosclerosis the outcome may be worse even in the presence of negative functional testing.

CASE SUMMARY

We present a case of 55-year-old male diabetic patient who was admitted for chest pain. Diagnostic coronary angiography disclosed 2 intermediate stenoses of the obtuse marginal branch with no evidence of restenosis on previously implanted stent. Patient undergone invasive functional testing of intermediate lesion with preserved FFR (0.88), low coronary flow reserve (1.2) and very high index of microvascular resistance (84). Due to discrepancy in invasive functional parameters, intravascular imaging with optical coherence tomography showed fibrotic stenoses without signs of thin-sup fibroatheroma. Because of the preserved FFR and no signs of vulnerable plaque, the interventional procedure was deferred and the patient continued with optimal medications.

CONCLUSION

Combined functional and anatomic imaging of intermediate coronary stenosis in diabetic patients represent comprehensive contemporary decision pathway in the management of the patients.

In-vitro validation of coronary physiology assessment with 5 French guiding catheters

BACKGROUND

The trans-radial approach for cardiac catheterization led to an increasing adoption of 5 French (F) catheters. We aim to evaluate reliability and reproducibility of coronary physiology assessment performed with 5F guiding catheter (GC).

METHODS

Physiological measurements were performed in a coronary flow simulator, which provides two pulsatile flows, the baseline and hyperaemic flows. Two screws, positioned proximally and distally to the distal sensor of a pressure-temperature guidewire, were used to determine various combinations of stenoses and distal obstructions, simulating different pathophysiological conditions. For each setting, 5 measurements of fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microvascular resistance (IMR) were performed with 6F and 5F GCs.

RESULTS

A total amount of 190 measurements were performed, 95 with 6F GC and 95 with 5F GC. Minimal differences between 6F and 5F GCs were detected for FFR [0.91 (IQR: 0.87-0.94) and 0.87 (IQR: 0.82-0.92) respectively, p < 0.001] and IMR (16.5 ± 8.8 and 15.4 ± 8.3 respectively, p = 0.001). Mean CFR was comparable between 6F and 5F GCs (3.6 ± 1.1 and 3.5 ± 0.7 respectively, p = 0.38). Misclassification rates were 1.0 %, 1.0 % and 0 % for FFR, CFR and IMR, respectively. According to Passing-Bablok analysis, an excellent agreement between 6F and 5F GCs was demonstrated for FFR and IMR, and a modest agreement for CFR. All measurements with 5F GC showed high reproducibility.

CONCLUSIONS

In our in-vitro model, a complete physiological assessment including FFR, CFR and IMR resulted substantially comparable between 6F and 5F GCs. Further in-vivo analysis is required to support these findings.

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 Influence of Microcirculatory Dysfunction on the Resting Full Cycle Ratio Compared to Fractional Flow Reserve

BACKGROUND

The relation between the resting full cycle ratio (RFR) and fractional flow reserve (FFR) is not fully understood. This study aims to investigate the influence of coronary microvascular dysfunction, assessed by the index of microvascular resistance (IMR), on RFR compared to FFR in patients undergoing functional assessment for coronary stenosis.

MATERIALS AND METHODS

Two-hundred patients with borderline stenosis underwent functional assessment of RFR, FFR, coronary flow reserve (CFR) and IMR. Retriever operator curve analysis was performed to assess the diagnostic value of RFR in patients with (IMR ≥ 24) and (IMR < 24).

RESULTS

Median RFR did not differ significantly in patients with IMR ≥ 24 compared to patients with IMR < 24: 0.89 (interquartile range (IQR) 0.84, 0.95) vs. 0.90 (IQR 0.84, 0.92), p = 0.29). FFR was significantly higher in patients with IMR ≥ 24 compared to patients with IMR < 24: median FFR 0.85 (IQR (0.76, 0.92)) vs. 0.82 (IQR 0.73, 0.86), p = 0.009, and median CFR was significantly lower 1.80 (IQR 1.40, 2.55) vs. 2.70 (IQR 1.80, 3.95), p < 0.001. The diagnostic value of RFR was high (Area under the curve (AUC) 0.89 95 % Confidence Interval: [0.85, 0.93]) and AUC did not differ between patients with IMR ≥ 24 compared to patients with IMR < 24: 0.89 vs. 0.90, p = 0.89. An overall optimal cut off of 0.88 was identified. The cut off did not differ significantly between patients with IMR ≥ 24 compared to patients with IMR < 24: 0.88 vs. 0.90, p = 0.397.

CONCLUSION

In patients with coronary borderline stenosis, the coronary microvascular function did not influence on the cut off values or AUC of RFR compared to FFR.

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.

Design and rationale of the EVOCATION trial: A prospective, randomized, exploratory study comparing the effect of evolocumab on coronary microvascular function after percutaneous coronary intervention in patients with stable coronary artery disease

Percutaneous coronary intervention (PCI) is a standard treatment in patients with stable coronary artery disease (CAD); however, periprocedural myocardial infarction (PMI) remains a common complication of PCI. Aggressive lipid-lowering therapy with statin has shown to reduce the incidence of PMI by preventing coronary microvascular dysfunction. It is unclear whether evolocumab, a potent lipid-lowering agent, could diminish microvascular damage after PCI. The EVOCATION trial (jRCTs051180022) is a multicenter, randomized, open-label, active-controlled, parallel-group, exploratory, investigator-initiated clinical study to evaluate whether pretreatment with evolocumab could decrease the index of microvascular resistance (IMR) after PCI in patients with stable CAD. This study population consists of 100 patients with stable CAD who will undergo PCI and have high low-density lipoprotein cholesterol levels despite administration of maximum tolerated dose of statins for at least 2 weeks. Eligible patients are randomized in a 1:1 ratio to receive either evolocumab 140 mg every 2 weeks in addition to standard of care treatment or standard of care treatment only for 2-6 weeks before PCI. The primary endpoint is IMR after PCI. The EVOCATION trial will evaluate whether pretreatment with evolocumab reduces periprocedural microvascular damage in patients with stable CAD undergoing PCI.

Coronary microvascular dysfunction assessed by continuous intracoronary thermodilution: A comparative study with index of microvascular resistance

BACKGROUND

This study aimed to assess the correlation between the standard of care, the index of microvascular resistance (IMR) versus the novel microvascular resistance (R_micro) and to determine the pathologic cut-off value in a selected population with suspected coronary microvascular dysfunction (CMD).

METHODS

One-hundred and twenty patients with high clinical suspicion of CMD due to ischemic symptoms in the absence of significant epicardial coronary lesions were prospectively included. Following a standardized systematic protocol, coronary flow reserve, IMR, fractional flow reserve, Q and R_micro were measured in the left anterior descending coronary artery using a temperature/pressure sensor-tipped guidewire and a dedicated infusion catheter.

RESULTS

There was a high prevalence of CMD with 50 (42%) patients showing an IMR ≥ 25. Median IMR was 23 [IQR: 14-34] and median R_micro was 464 Woods Units (WU) [IQR: 354-636WU]. ROC analyses identified 500 WU as the optimal R_micro cut-off to identify patients with an IMR ≥ 25, with an area under the ROC curve (C statistic) of 0.83 (95% CI: 0.74 to 0.89, p < 0.0001).

CONCLUSIONS

R_micro derived from continuous intracoronary thermodilution is an accurate index to measure microvascular resistances enabling the invasive diagnostic of CMD.

Index of microvascular resistance and outcomes following intra-coronary thrombolysis with percutaneous intervention in STEMI: a meta-analysis of randomized control trials

Microvascular obstruction following percutaneous coronary intervention (PCI) is highly prevalent and independently associated with adverse clinical outcomes. Microvascular obstruction is determined by index of the microvascular resistance. We performed a systematic review with meta-analysis of all published randomized clinical trials (RCTs) studying the effect of intra-coronary thrombolysis with PCI as compared to standard treatment among patients with ST-segment elevated myocardial infarction. We included 6 RCTs summing up to 947 patients in the final analysis. Intra-coronary thrombolysis resulted in significantly lower index of microvascular resistance [standardized mean difference: - 13.74, 95% confidence interval (CI): - 16.74 to - 10.73, P value < 0.001, I² = 0%]. There was no difference noted in the occurrence of major adverse cardiac events with intra-coronary thrombolysis as compared to standard treatment [Odds ratio:  0.71, 95% CI: 0.46-1.08, P value = 0.11,  I² = 0%]. The absence of heterogeneity deferred us from using dose-response analysis to account for altering dose used across studies. The results of the present meta-analysis highlights the role of intra-coronary thrombolysis in reducing microvascular obstruction. No effect of intra-coronary thrombolysis was noted on the occurrence of major adverse cardiac events.

Coronary microvascular dysfunction in stable ischaemic heart disease (non-obstructive coronary artery disease and obstructive coronary artery disease)

Diffuse and focal epicardial coronary disease and coronary microvascular abnormalities may exist side-by-side. Identifying the contributions of each of these three players in the coronary circulation is a difficult task. Yet identifying coronary microvascular dysfunction (CMD) as an additional player in patients with coronary artery disease (CAD) may provide explanations of why symptoms may persist frequently following and why global coronary flow reserve may be more prognostically important than fractional flow reserve measured in a single vessel before percutaneous coronary intervention. This review focuses on the challenges of identifying the presence of CMD in the context of diffuse non-obstructive CAD and obstructive CAD. Furthermore, it is going to discuss the pathophysiology in this complex situation, examine the clinical context in which the interaction of the three components of disease takes place and finally look at non-invasive diagnostic methods relevant for addressing this question.