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

A case of heat stroke with significantly elevated troponin and dynamic ECG changes: Myocardial infarction or Myocardial injury?

We describe an 82-year-old man who was taken to our emergency department after being found unconscious. His electrocardiogram (ECG) showed ST-segment elevation in leads V4-V6 and cardiac troponin I (cTnI) was abnormally elevated. In addition to ECG and cTnI changes, this patient was combined with unconsciousness, high fever, abnormal liver function, acute renal failure, and rhabdomyolysis. The initial diagnosis was heat stroke, so cooling measures were initiated immediately, but a concurrent myocardial infarction was suspected. Meanwhile, emergency coronary angiography was performed, but no severe coronary stenosis or thrombosis was found. We first evaluated quantitative flow ratio (QFR) and coronary angiography-derived index of microvascular resistance (ca-IMR) in patients with heat stroke. Ca-IMR was 260 mmHg*s/m in the left circumflex artery, indicating the presence of coronary microvascular dysfunction (CMD). After several days of treatment, the patient recovered from multiple organ damage. Therefore, ECG and troponin results should be interpreted carefully in patients with high fever and coma during high temperature seasons.

The pressure-derived microvascular resistance reserve and its correlation to Doppler MRR measurement-a proof of concept study

Background

Microvascular resistance reserve (MRR) is a recently introduced specific index of coronary microcirculation. MRR calculation can utilize parameters deriving from coronary flow reserve (CFR) assessment, provided that intracoronary pressure data are also available. The previously proposed pressure-bounded CFR (CFRpb) defines the possible CFR interval on the basis of resting and hyperemic pressure gradients in the epicardial vessel, however, its correlation to the Doppler wire measurement was reported to be rather poor without the correction for hydrostatic pressure.

Purpose

We aimed to determine the pressure-bounded coronary MRR interval with hydrostatic pressure correction according to the previously established equations of CFRpb adapted for the MRR concept. Furthermore, we also aimed to design a prediction model using the actual MRR value within the pressure-bounded interval and validate the results against the gold-standard Doppler wire technique.

Methods

Hydrostatic pressure between the tip of the catheter and the sensor of the pressure wire was calculated by height difference measurement from a lateral angiographic view. In the derivation cohort the pressure-bounded MRR interval (between MRRpbmin and MRRpbmax) was determined solely from hydrostatic pressure-corrected intracoronary pressure data. The actual MRR was calculated by simple hemodynamic equations incorporating the anatomical data of the three-dimensionally reconstructed coronary artery (MRRp-3D). These results were analyzed by regression analyses to find relations between the MRRpb bounds and the actual MRRp-3D.

Results

In the derivation cohort of 23 measurements, linear regression analysis showed a tight relation between MRRpbmax and MRRp-3D (r 2 = 0.74, p < 0.0001). Using this relation (MRRp-3D = 1.04 + 0.51 × MRRpbmax), the linear prediction of the MRR was tested in the validation cohort of 19 measurements against the gold standard Doppler wire technique. A significant correlation was found between the linearly predicted and the measured values (r = 0.54, p = 0.01). If the area stenosis (AS%) was included to a quadratic prediction model, the correlation was improved (r = 0.63, p = 0.004).

Conclusions

The MRR can be predicted reliably to assess microvascular function by our simple model. After the correction for hydrostatic pressure error, the pressure data during routine FFR measurement provides a simultaneous physiological assessment of the macro- and microvasculature.

The association between O2-pulse slope ratio and functional severity of coronary stenosis: A combined cardiopulmonary exercise testing and quantitative flow ratio study

Background

The role of cardiopulmonary exercise testing (CPET) parameters in evaluating the functional severity of coronary disease remains unclear. The aim of this study was to quantify the O2-pulse morphology and investigate its relevance in predicting the functional severity of coronary stenosis, using Murray law-based quantitative flow ratio (μQFR) as the reference.

Methods

CPET and μQFR were analyzed in 138 patients with stable coronary artery disease (CAD). The O2-pulse morphology was quantified through calculating the O2-pulse slope ratio. The presence of O2-pulse plateau was defined according to the best cutoff value of O2-pulse slope ratio for predicting μQFR ≤ 0.8.

Results

The optimal cutoff value of O2-pulse slope ratio for predicting μQFR ≤ 0.8 was 0.4, with area under the curve (AUC) of 0.632 (95 % CI: 0.505-0.759, p = 0.032). The total discordance rate between O2-pulse slope ratio and μQFR was 27.5 %, with 13 patients (9.4 %) being classified as mismatch (O2-pulse slope ratio > 0.4 and μQFR ≤ 0.8) and 25 patients being classified as reverse-mismatch (O2-pulse slope ratio ≤ 0.4 and μQFR > 0.8). Angiography-derived microvascular resistance was independently associated with mismatch (OR 0.07; 95 % CI: 0.01-0.38, p = 0.002) and reverse-mismatch (OR 9.76; 95 % CI: 1.47-64.82, p = 0.018).

Conclusion

Our findings demonstrate the potential of the CPET-derived O2-pulse slope ratio for assessing myocardial ischemia in stable CAD patients.

Angiographic microvascular resistance in patients with obstructive hypertrophic cardiomyopathy

BACKGROUND

Coronary microvascular dysfunction (CMD) is an important feature of obstructive hypertrophic cardiomyopathy (oHCM). Angiographic microvascular resistance (AMR) offers a potent means for assessing CMD. This study sought to evaluate the prognostic value of CMD burden calculated by AMR among oHCM patients.

METHODS

We retrospectively screened all patients diagnosed with oHCM from Fuwai Hospital between January 2017 and November 2021. Off-line AMR assessments were performed for all 3 major coronary vessels by the independent imaging core laboratory. Patients were followed every 6 months post discharge via office visit or telephone contacts. The primary outcome was major adverse cardiovascular events (MACE), including all-cause death, and unplanned rehospitalization for heart failure.

RESULTS

A total of 342 patients presented with oHCM diseases enrolled in the present analyses. Mean age was 49.7, 57.6 % were men, mean 3-vessel AMR was 6.9. At a median follow-up of 18 months, high capability of 3-vessel AMR in predicting MACE was identified (AUC: 0.70) with the best cut-off value of 7.04. The primary endpoint of MACE was significantly higher in high microvascular resistance group (3-vessel AMR ≥ 7.04) as compared with low microvascular resistance group (56.5 % vs. 16.5 %; HR: 5.13; 95 % CI: 2.46-10.7; p < 0.001), which was mainly driven by the significantly higher risk of heart failure events in high microvascular resistance group. Additionally, 3-vessel AMR (HR: 4.37; 95 % CI: 1.99-9.58; p < 0.001), and age (per 1 year increase, HR: 1.03; 95 % CI: 1.01-1.06; p = 0.02) were independently associated with MACE.

CONCLUSION

The present retrospective study demonstrated that the novel angiography-based AMR was a useful tool for CMD evaluation among patients with oHCM. High microvascular resistance as identified by 3-vessel AMR (≥7.04) was associated with worse prognosis.

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).

Association between the insufficient improvement of the quantitative flow ratio and worsening outcomes in ST-segment elevated myocardial infarction: a multicentre prospective cohort study

Background

Improved coronary physiological function after percutaneous coronary intervention (PCI) has been shown to improve prognosis in stable ischaemic heart disease, but has not yet been explored in ST-segment elevated myocardial infarction (STEMI). The study sought to determine whether an improvement in the quantitative flow ratio (QFR) could improve the prognosis of STEMI patients undergoing primary PCI.

Methods

Patients diagnosed with STEMI who were receiving primary PCI were recruited for the study. Those with thrombolysis in myocardial infarction (TIMI) flow <2 after wiring were excluded. The ΔQFR was calculated using the following formula: ΔQFR = post-PCI QFR - pre-stent QFR. The primary endpoint was the composite event, including recurrent myocardial infarction (MI) and acute heart failure (AHF).

Results

In total, 515 STEMI patients with a median follow-up of 364 days were enrolled in the study. Based on the cut-off value from the receiver operator characteristic (ROC) curve, the patients were divided into the following two groups: the lower ΔQFR group (≤0.25, N=332); and the normal ΔQFR group (>0.25, N=183). Patients with a lower ΔQFR had a relatively higher rate of MI/AHF (10.5% vs. 4.4%, P=0.019) and AHF (7.2% vs. 2.7%, P=0.044). A lower ΔQFR was significantly associated with a higher incidence of MI/AHF [hazard ratio (HR) =2.962, 95% confidence interval (CI): 1.358-6.459, P=0.006, respectively] after adjusting for potential confounders. Pre-stent angiographic microvascular resistance [odds ratio (OR) =1.027, 95% CI: 1.022-1.033, P<0.001] and the stent-to-vessel diameter ratio <1.13 (OR =1.766, 95% CI: 1.027-3.071, P=0.04) were independent predictors of a lower ΔQFR.

Conclusions

An insufficient improvement in the QFR contributes to worsening outcomes and might be a useful tool for risk stratification in STEMI.

Impact of post-dilatation on post-procedural physiology, microcirculatory resistance, and target vessel failure in STEMI patients undergoing PPCI: A single-center experience

BACKGROUND

Suboptimal stent deployment is frequently observed in ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PPCI). This study sought to investigate whether these patients could benefit from post-dilatation with respect to post-procedural physiology, microcirculatory resistance, and long-term clinical outcomes.

METHODS

This was a retrospective study of consecutive STEMI patients who underwent successful stent implantation during PPCI from February 2016 to November 2021. Post-procedural physiology and microcirculatory resistance were assessed by Murray law-based quantitative flow ratio (μQFR) and angiographic microcirculatory resistance (AMR), respectively. The primary outcome was target vessel failure (TVF), a composite of cardiac death, target vessel-oriented myocardial infarction, and clinically driven target vessel revascularization.

RESULTS

A total of 671 patients (671 culprit vessels) were included. Post-dilatation was selectively performed in 430 (64.1%) culprit vessels, resulting in a 0.02 (interquartile range: 0.00-0.05, p < 0.001) increase in post-procedural μQFR but no significant impact on AMR. During a median follow-up of 2.8 years (interquartile range: 1.4-3.0 years), TVF occurred in 47 (7.0%) patients. Post-dilatation demonstrated a trend toward a reduction in TVF (5.3% vs. 10.0%; adjusted hazard ratio: 0.60, 95% confidence interval: 0.33-1.09, p = 0.094), mainly driven by a lower incidence of clinically driven target vessel revascularization (1.6% vs. 4.1%; adjusted hazard ratio: 0.32, 95% confidence interval: 0.11-0.90, p = 0.030).

CONCLUSIONS

In STEMI patients undergoing PPCI, selective post-dilatation was associated with improved post-procedural physiological results and a trend toward less TVF events without aggravating microcirculatory resistance.

Effect of hemoglobin A1c management levels on coronary physiology evaluated by quantitative flow ratio in patients who underwent percutaneous coronary intervention

AIMS/INTRODUCTION

The coronary physiology and prognosis of patients with different hemoglobin A1c (HbA1c) levels after percutaneous coronary intervention (PCI) are currently unknown. The aim of this study was to assess the effect of different levels of HbA1c control on coronary physiology in patients who underwent PCI for coronary heart disease combined with type 2 diabetes mellitus by quantitative flow ratio (QFR).

MATERIALS AND METHODS

Patients who successfully underwent PCI and completed 1-year coronary angiographic follow up were enrolled, clinical data were collected, and QFR at immediate and 1-year follow up after PCI was retrospectively analyzed. A total of 257 patients (361 vessels) were finally enrolled and divided into the hemoglobin A1c (HbA1c)-compliance group (103 patients, 138 vessels) and non-HbA1c-compliance group (154 patients, 223 vessels) according to the HbA1c cut-off value of 7%. We compared the results of QFR analysis and clinical outcomes between the two groups.

RESULTS

At 1-year follow up after PCI, the QFR was significantly higher (0.94 ± 0.07 vs 0.92 ± 0.10, P = 0.019) and declined less (0.014 ± 0.066 vs 0.033 ± 0.095, P = 0.029) in the HbA1c-compliance group. Meanwhile, the incidence of physiological restenosis was lower in the HbA1c-compliance group (2.9% vs 8.5%, P = 0.034). Additionally, the target vessel revascularization rate was lower in the HbA1c-compliance group (6.8% vs 16.9%, P = 0.018). Furthermore, HbA1c ≥7% (OR 2.113, 95% confidence interval 1.081-4.128, P = 0.029) and QFR decline (OR 2.215, 95% confidence interval 1.147-4.277, P = 0.018) were independent risk factors for target vessel revascularization.

CONCLUSION

Patients with well-controlled HbA1c levels have better coronary physiological benefits and the incidence of adverse clinical outcome events might be reduced.

Diagnostic value of angiography-derived index of microcirculatory resistance (AMR) for coronary microcirculatory dysfunction (CMD) and its prognostic significance in patients with chronic coronary syndromes in the smoking population

This study aims to analyze the prognostic significance of angiographic microvascular resistance (AMR) derived from functional coronary angiography in diagnosing coronary microvascular dysfunction (CMD) among patients with chronic coronary syndrome (CCS), particularly focusing on the prognostic significance of CMD in smokers. Additionally, this study assesses the prognostic significance of the diagnostic accuracy of the AMR index for CMD in CCS patients within the smoking population. Seventy-five CCS patients were studied for IMR measurement between June 2018 and December 2020, classified into CMD and non-CMD groups. Pearson correlation analyzed AMR and IMR relationship, while ROC curves determined AMR's predictive value for CMD with optimal cutoff value. An additional 223 CCS patients were included for AMR measurements. The study's primary endpoint was MACE occurrence, followed up through telephone calls. COX one-way analysis and Kaplan-Meier analysis evaluated the association between AMR and MACE risk. In the study, 52% of patients were diagnosed with CMD, and the AUC under the AMR curve for predicted IMR ≥ 25 was 0.90 (95% CI: 0.79-0.95). The CMD group had a higher proportion of female patients, smokers, and those with hypertension and diabetes mellitus compared to the non-CMD group (all P < .05). The CMD group exhibited higher AMR values than the non-CMD group (3.20 ± 0.5 vs 1.95 ± 0.45, P < .01), with a significant correlation between AMR and IMR (R2 = 0.81, P < .001). The ROC curve illustrated AMR's effectiveness in diagnosing CMD in CCS patients, using IMR as the gold standard, with the optimal cutoff value of AMR = 2.6mmHgs/cm (sensitivity: 90.5%, specificity: 81.5%). Patients with AMR ≥ 2.6mmHgs/cm had a higher risk of MACE events (HR = 6.00; 95% CI: 1.59-22.67). AMR in patients with CCS was significantly correlated with IMR and demonstrated good diagnostic accuracy. AMR ≥ 2.6 mm Hg*s/cm was associated with an increased risk of MACE occurrence and served as a valuable prognostic factor. In patients with CCS, AMR has a high diagnostic performance, In patients with CCS who smoke, impaired coronary microvascular function as assessed by AMR is significant and is an independent predictor of MACE.

Impact of Pericoronary Adipose Tissue Attenuation on Periprocedural Myocardial Injury in Patients With Chronic Coronary Syndrome

BACKGROUND

Perivascular inflammation contributes to the development of atherosclerosis and microcirculatory dysfunction. Pericoronary adipose tissue (PCAT) attenuation, measured by coronary computed tomography angiography, is a potential indicator of coronary inflammation. However, the relationship between PCAT attenuation, microcirculatory dysfunction, and periprocedural myocardial injury (PMI) remains unclear.

METHODS AND RESULTS

Patients with chronic coronary syndrome who underwent coronary computed tomography angiography before percutaneous coronary intervention were retrospectively identified. PCAT attenuation and adverse plaque characteristics were assessed using coronary computed tomography angiography. The extent of microcirculatory dysfunction was evaluated using the angio-based index of microcirculatory resistance before and after percutaneous coronary intervention. Overall, 125 consecutive patients were included, with 50 experiencing PMI (PMI group) and 75 without PMI (non-PMI group). Multivariable analysis showed that older age, higher angio-based index of microcirculatory resistance, presence of adverse plaque characteristics, and higher lesion-based PCAT attenuation were independently associated with PMI occurrence (odds ratio [OR], 1.07 [95% CI, 1.01-1.13]; P=0.02; OR, 1.06 [95% CI, 1.00-1.12]; P=0.04; OR, 6.62 [95% CI, 2.13-20.6]; P=0.001; and OR, 2.89 [95% CI, 1.63-5.11]; P<0.001, respectively). High PCAT attenuation was correlated with microcirculatory dysfunction before and after percutaneous coronary intervention and its exacerbation during percutaneous coronary intervention. Adding lesion-based PCAT attenuation to the presence of adverse plaque characteristics improved the discriminatory and reclassification ability in predicting PMI.

CONCLUSIONS

Adding PCAT attenuation at the culprit lesion level to coronary computed tomography angiography-derived adverse plaque characteristics may provide incremental benefit in identifying patients at risk of PMI. Our results highlight the importance of microcirculatory dysfunction in PMI development, particularly in the presence of lesions with high PCAT attenuation.

REGISTRATION

URL: https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000057722; Unique identifier: UMIN000050662.

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.

Effects of percutaneous coronary intervention and diabetes mellitus on short- and long-term prognosis assessed by the three-vessel quantitative flow ratio

AIMS

We aimed to investigate the impact of percutaneous coronary intervention (PCI) and diabetes mellitus (DM) on short- and long-term prognosis in patients with coronary artery disease using three-vessel quantitative flow ratio (3 V-QFR) assessment.

METHODS

A retrospective analysis of 2440 vessels in 1181 patients who underwent PCI was performed. The patients were categorized according to the presence or absence of DM and the median 3 V-QFR. The primary outcome was the occurrence of major adverse cardiac events (MACE), defined as a combination of cardiovascular death, myocardial infarction, and ischemia-driven revascularization, over a 5-year period.

RESULTS

The pre-PCI and post-PCI 3 V-QFR values for the entire population were 2.37 (2.04-2.56) and 2.94 (2.82-3.00), respectively. Landmark analysis showed that the incidence of MACE was comparable among all groups within the first year (log-rank p = 0.088). Over the course of 2 years, the incidence of MACE was higher in both groups with a post-PCI 3 V-QFR < 2.94 (log-rank p < 0.001). However, from 2 to 5 years, patients with DM had higher rates of MACE (log-rank p = 0.013).

CONCLUSIONS

In the short term, a low post-PCI 3 V-QFR is a predictor of high risk for MACE. However, in the long term, DM emerges as the dominant risk factor.

Integrated Assessment of Computational Coronary Physiology From a Single Angiographic View in Patients Undergoing TAVI

BACKGROUND

Angiography-derived computational physiology is an appealing alternative to pressure-wire coronary physiology assessment. However, little is known about its reliability in the setting of severe aortic stenosis. This study sought to provide an integrated assessment of epicardial and microvascular coronary circulation by means of single-view angiography-derived physiology in patients with severe aortic stenosis undergoing transcatheter aortic valve implantation (TAVI).

METHODS

Pre-TAVI angiographic projections of 198 stenotic coronary arteries (123 patients) were analyzed by means of Murray's law-based quantitative flow ratio and angiography microvascular resistance. Wire-based reference measurements were available for comparison: fractional flow reserve (FFR) in all cases, instantaneous wave-free ratio in 148, and index of microvascular resistance in 42 arteries.

RESULTS

No difference in terms of the number of ischemia-causing stenoses was detected between FFR ≤0.80 and Murray's law-based quantitative flow ratio ≤0.80 (19.7% versus 19.2%; P=0.899), while this was significantly higher when instantaneous wave-free ratio ≤0.89 (44.6%; P=0.001) was used. The accuracy of Murray's law-based quantitative flow ratio ≤0.80 in predicting pre-TAVI FFR ≤0.80 was significantly higher than the accuracy of instantaneous wave-free ratio ≤0.89 (93.4% versus 77.0%; P=0.001), driven by a higher positive predictive value (86.9% versus 50%). Similar findings were observed when considering post-TAVI FFR ≤0.80 as reference. In 82 cases with post-TAVI angiographic projections, Murray's law-based quantitative flow ratio values remained stable, with a low rate of reclassification of stenosis significance (9.9%), similar to FFR and instantaneous wave-free ratio. Angiography microvascular resistance demonstrated a significant correlation (Rho=0.458; P=0.002) with index of microvascular resistance, showing an area under the curve of 0.887 (95% CI, 0.752-0.964) in predicting index of microvascular resistance ≥25.

CONCLUSIONS

Angiography-derived physiology provides a valid, reliable, and systematic assessment of the coronary circulation in a complex scenario, such as severe aortic stenosis.

Impact of Isolated Coronary Microvascular Disease Diagnosed Using Various Measurement Modalities on Prognosis: An Updated Systematic Review and Meta-Analysis

INTRODUCTION

The main aim of this study was to investigate the impact of isolated coronary microvascular disease (CMD) as diagnosed via various modalities on prognosis.

METHODS

A systematic literature review of PubMed, Embase, and Cochrane Library databases was conducted to identify relevant studies published up to March 2023. Included studies were required to measure coronary microvascular function and report outcomes in patients without obstructive coronary artery disease (CAD) or any other cardiac pathological characteristics. The primary endpoint was all-cause mortality, and the secondary endpoint was a major adverse cardiac event (MACE). Pooled effects were calculated using random effects models.

RESULTS

A total of 27 studies comprising 18,204 subjects were included in the meta-analysis. Indices of coronary microvascular function measurement included coronary angiography-derived index of microcirculatory resistance (caIMR), hyperemic microcirculatory resistance (HMR), coronary flow reserve (CFR), and so on. Patients with isolated CMD exhibited a significantly higher risk of mortality (OR: 2.97, 95% CI, 1.91-4.60, p < 0.0001; HR: 3.38, 95% CI, 1.77-6.47, p = 0.0002) and MACE (OR: 5.82, 95% CI, 3.65-9.29, p < 0.00001; HR: 4.01, 95% CI, 2.59-6.20, p < 0.00001) compared to those without CMD. Subgroup analysis by measurement modality demonstrated consistent and robust pooled effect estimates in various subgroups.

CONCLUSION

CMD is significantly associated with an elevated risk of mortality and MACE in patients without obstructive CAD or any other identifiable cardiac pathologies. The utilization of various measurement techniques may have potential advantages in the management of isolated CMD.

Impact of plaque characteristics on percutaneous coronary intervention-related microvascular dysfunction: insights from angiographic microvascular resistance and intravascular ultrasound

Background

The correlation between percutaneous coronary intervention (PCI)-related microvascular dysfunction (MVD) and plaque characteristics remains unclear. To investigate this correlation and its prognosis, we assessed changes in MVD by angiographic microvascular resistance (AMR) and intracoronary ultrasound scans after PCI.

Methods

We conducted a retrospective study that enrolled 250 patients with coronary artery disease between July 2016 and December 2018. We collected demographic characteristics, laboratory tests, coronary angiography (CAG) and intracoronary ultrasound findings. We calculated quantitative flow ratio (QFR) and AMR by CAG. The endpoint was vessel-oriented composite outcomes (VOCOs).

Results

After 47 exclusions, we divided 203 cases into a deteriorated group (n=139) and an improved group (n=64) based on AMR change after PCI. Compared with the improved group, the deteriorated group had smaller lumen area [3.03 (interquartile range, 2.20-3.91) vs. 3.55 mm2 (interquartile range, 2.45-4.57), P=0.033], higher plaque burden [78.92% (interquartile range, 73.95-82.61%) vs. 71.93% (interquartile range, 62.70-77.51%), P<0.001], and higher proportion of lipidic components (13.86%±4.67% vs. 11.78%±4.41%, P=0.024). Of 186 patients who completed 4.81±1.55 years follow-up, 56 developed VOCOs. Receiver-operating characteristic (ROC) curve analysis showed post-PCI AMR and VOCOs correlation (area under the curve: 0.729, P<0.001). Multivariate regression analysis showed post-PCI AMR >285 mmHg·s/m correlated with adverse outcome (hazard ratio =4.350; 95% confidence interval: 1.95-9.703; P<0.001).

Conclusions

Intravascular ultrasound (IVUS) imaging and AMR revealed an association of post-PCI MVD with a smaller lumen area, more severe plaque burden, and a higher percentage of lipidic components. Post-PCI MVD was an independent risk factor for poor prognosis.