Fractional flow reserve: physiological basis, advantages and limitations, and potential gender differences

Multimodality OCT, IVUS and FFR evaluation of coronary intermediate grade lesions in women vs. men

Background

The pathophysiology of atherosclerotic plaque formation and its vulnerability seem to differ between genders due to contrasting risk profiles and sex hormones, however this process is still insufficiently understood. The aim of the study was to compare the differences between sexes regarding the optical coherence tomography (OCT), intravascular ultrasound (IVUS) and fractional flow reserve (FFR)-derived coronary plaque indices.

Methods

In this single-center multimodality imaging study patients with intermediate grade coronary stenoses identified in coronary angiogram (CAG) were evaluated using OCT, IVUS and FFR. Stenoses were considered significant when the FFR value was ≤0.8. Minimal lumen area (MLA), was analyzed by OCT in addition to plaque stratification into fibrotic, calcific, lipidic and thin-cap fibroatheroma (TCFA). IVUS was used for evaluation of lumen-, plaque- and vessel volume, as well as plaque burden.

Results

A total of 112 patients (88 men and 24 women) with chronic coronary syndromes (CCS), who underwent CAG were enrolled. No significant differences in baseline characteristics were present between the study groups. The mean FFR was 0.76 (0.73-0.86) in women and 0.78 ± 0.12 in men (p = 0.695). OCT evaluation showed a higher prevalence of calcific plaques among women than men p = 0.002 whereas lipid plaques were more frequent in men (p = 0.04). No significant differences regarding minimal lumen diameter and minimal lumen area were found between the sexes. In IVUS analysis women presented with significantly smaller vessel area, plaque area, plaque volume, vessel volume (11.1 ± 3.3 mm² vs. 15.0 ± 4.6 mm² p = 0.001, 6.04 ± 1.7 mm² vs. 9.24 ± 2.89 mm² p < 0.001, 59.8 ± 35.2 mm³ vs. 96.3 (52.5-159.1) mm³ p = 0.005, 106.9 ± 59.8 mm³ vs. 153.3 (103-253.4) mm³ p = 0.015 respectively). At MLA site plaque burden was significantly greater for men than women (61.50 ± 7.7% vs. 55.5 ± 8.0% p = 0.005). Survival did not differ significantly between women and men (94.6 ± 41.9 months and 103.51 ± 36.7 months respectively; p = 0.187).

Conclusion

The presented study did not demonstrate significant differences in FFR values between women and men, yet a higher prevalence of calcific plaques by OCT and lower plaque burden at the MLA site by IVUS was found in women vs. men.

Improved Diagnosis through Diastolic Hyperemia-Free Ratio (DFR) over Fractional Flow Reserve (FFR) in Intermediate Coronary Lesions

OBJECTIVES

To compare the fractional flow reserve (FFR) and diastolic hyperemia-free ratio (DFR) measurements in a population with intermediate coronary artery stenosis and improve the diagnosis.

BACKGROUND

Visual assessment of coronary artery stenosis severity, particularly in intermediate lesions, is prone to errors in decision-making. FFR provides a reliable assessment of functional severity in these cases but requires hyperemia induction by adenosine, which has side effects and increased cost. DFR is a novel hyperemia-independent index, which could be used as an alternative to adenosine-based hyperemia induction.

METHODS AND RESULTS

Between September 2019 to March 2020, 25 patients with 38 intermediate coronary stenotic lesions were included in the study. All patients underwent assessment of whole cycle Pd/Pa (ratio of distal coronary pressure to proximal aortic pressure), DFR and FFR. Mean whole cycle Pd/Pa, DFR and FFR were 0.93±0.06, 0.88±0.09, and 0.85±0.08, respectively. A significant positive correlation between DFR and FFR [r = 0.74; p<0.001] was observed. Receiver operating characteristic analysis showed an area under the curve of 0.90. DFR-only strategy with a treatment cut-off of ≤0.89 showed a diagnostic agreement with the FFR-only strategy in 74% of lesions, with a sensitivity of 54%, specificity of 82%, a positive predictive value of 60%, and a negative predictive value of 79%.

CONCLUSIONS

Real-time DFR measurements show a clinically reliable correlation with FFR. Hence, using DFR is likely to avoid adenosine administration as well as reduce the cost and procedural time. Further studies with a larger sample size would be ideal to evaluate specific cut-off values and endpoints.

Is it the Time to Move Towards Coronary Computed Tomography Angiography-Derived Fractional Flow Reserve Guided Percutaneous Coronary Intervention? The Pros and Cons

Coronary artery disease is the leading cause of mortality worldwide. Diagnosis is conventionally performed by direct visualization of the arteries by invasive coronary angiography (ICA), which has inherent limitations and risks. Measurement of fractional flow reserve (FFR) has been suggested for a more accurate assessment of ischemia in the coronary artery with high accuracy for determining the severity and decision on the necessity of intervention. Nevertheless, invasive coronary angiography-derived fractional flow reserve (ICA-FFR) is currently used in less than one-third of clinical practices because of the invasive nature of ICA and the need for additional equipment and experience, as well as the cost and extra time needed for the procedure. Recent technical advances have moved towards non-invasive high-quality imaging modalities, such as magnetic resonance, single-photon emission computed tomography, and coronary computed tomography (CT) scan; however, none had a definitive modality to confirm hemodynamically significant coronary artery stenosis. Coronary computed tomography angiography (CCTA) can provide accurate anatomic and hemodynamic data about the coronary lesion, especially calculating fractional flow reserve derived from CCTA (CCTA-FFR). Although growing evidence has been published regarding CCTA-FFR results being comparable to ICA-FFR, CCTA-FFR has not yet replaced the invasive conventional angiography, pending additional studies to validate the advantages and disadvantages of each diagnostic method. Furthermore, it has to be identified whether revascularization of a stenotic lesion is plausible based on CCTA-FFR and if the therapeutic plan can be determined safely and accurately without confirmation from invasive methods. Therefore, in the present review, we will outline the pros and cons of using CCTA-FFR vs. ICA-FFR regarding diagnostic accuracy and treatment decision-making.

Differences in Plaque Characteristics and Myocardial Mass

Background

The mechanism of the fractional flow reserve (FFR) difference according to sex has not been clearly understood.

Objectives

This study sought to evaluate sex differences in coronary stenosis, plaque characteristics, and left ventricular (LV) mass and their implications for physiological significance.

Methods

This was a post hoc analysis of a pooled population of multicenter, international prospective cohorts. Patients (166 women and 489 men) underwent coronary computed tomography angiography (CCTA) within 90 days before invasive FFR measurements were included. The minimal lumen area, percent of plaque burden, whole vessel plaque volume by composition, high-risk plaque characteristics, and LV mass were analyzed from CCTA images.

Results

Among 1,188 vessels analyzed, the FFR value was higher in women than that in men (0.85 ± 0.13 vs 0.82 ± 0.14; P = 0.001) despite a similar percentage of diameter stenosis between the sexes (45.9% ± 18.9% vs 46.1% ± 17.7%; P = 0.920). The composition of fibrofatty plaque + necrotic core (13.1% ± 16.9% vs 21.2% ± 19.9%; P < 0.001) and frequencies of low attenuation plaque (12.7% vs 24.5%; P < 0.001) and positive remodeling (33.8% vs 45.5%; P = 0.001) were lower in women than in men. Vessel, plaque, and lumen volumes were significantly smaller in women than that in men (all P < 0.001); however, no sex difference was observed in any of these parameters after adjustment for LV mass (all P > 0.10). Sex was not an independent predictor of the FFR value after adjustment for stenosis severity, plaque characteristics, and LV mass.

Conclusions

Higher FFR values for the same stenosis severity in women can be explained by fewer high-risk plaque characteristics and smaller myocardial mass in women than that in men. (CCTA-FFR Registry for Risk Prediction; NCT04037163)

Sex Differences in the Non-infarct-Related Artery-Based Quantitative Flow Ratio in Patients With ST-Elevation Myocardial Infarction: A Retrospective Study

Introduction: It has been reported that sex has well-established relationships with the prevalence of coronary artery disease (CAD) and the major adverse cardiovascular events. Compared with men, the difference of coronary artery and myocardial characteristics in women has effects on anatomical and functional evaluations. Quantitative flow ratio (QFR) has been shown to be effective in assessing the hemodynamic relevance of lesions in stable coronary disease. However, its suitability in acute myocardial infarction patients is unknown. This study aimed to evaluate the sex differences in the non-infarct-related artery (NIRA)-based QFR in patients with ST-elevation myocardial infarction (STEMI).

Methods: In this study, 353 patients with STEMI who underwent angiographic cQFR assessment and interventional therapy were included. According to contrast-flow QFR (cQFR) standard operating procedures: reliable software was used to modeling the hyperemic flow velocity derived from coronary angiography in the absence of pharmacologically induced hyperemia. 353 patients were divided into two groups according to sex. A cQFR ≤0.80 was considered hemodynamically significant, whereas invasive coronary angiography (ICA) luminal stenosis ≥50% was considered obstructive. Demographics, clinical data, NIRA-related anatomy, and functional cQFR values were recorded. Clinical outcomes included the NIRA reclassification rate between men and women, according to the ICA and cQFR assessments.

Results: Women were older and had a higher body mass index (BMI) than men. The levels of diastolic blood pressure, troponin I, peak creatine kinase-MB, low-density lipoprotein cholesterol, N terminal pro B-type natriuretic peptide, stent diameter, and current smoking rate were found to be significantly lower in the female group than in the male group. Women had a lower likelihood of a positive cQFR ≤0.80 for the same degree of stenosis and a lower rate of NIRA revascularization. Independent predictors of positive cQFR included male sex and diameter stenosis (DS) >70%.

Conclusions: cQFR values differ between the sexes, as women have a higher cQFR value for the same degree of stenosis. The findings suggest that QFR variations by sex require specific interpretation, as these differences may affect therapeutic decision-making and clinical outcomes.

Sex Differences in Instantaneous Wave-Free Ratio or Fractional Flow Reserve-Guided Revascularization Strategy

OBJECTIVES

This study sought to evaluate sex differences in procedural characteristics and clinical outcomes of instantaneous wave-free ratio (iFR)- and fractional flow reserve (FFR)-guided revascularization strategies.

BACKGROUND

An iFR-guided strategy has shown a lower revascularization rate than an FFR-guided strategy, without differences in clinical outcomes.

METHODS

This is a post hoc analysis of the DEFINE-FLAIR (Functional Lesion Assessment of Intermediate stenosis to guide Revascularization) study, in which 601 women and 1,891 men were randomized to iFR- or FFR-guided strategy. The primary endpoint was 1-year major adverse cardiac events (MACE), a composite of all-cause death, nonfatal myocardial infarction, or unplanned revascularization.

RESULTS

Among the entire population, women had a lower number of functionally significant lesions per patient (0.31 ± 0.51 vs. 0.43 ± 0.59; p < 0.001) and less frequently underwent revascularization than men (42.1% vs. 53.1%; p < 0.001). There was no difference in mean iFR value according to sex (0.91 ± 0.09 vs. 0.91 ± 0.10; p = 0.442). However, the mean FFR value was lower in men than in women (0.83 ± 0.09 vs. 0.85 ± 0.10; p = 0.001). In men, an FFR-guided strategy was associated with a higher rate of revascularization than an iFR-guided strategy (57.1% vs. 49.3%; p = 0.001), but this difference was not observed in women (41.4% vs. 42.6%; p = 0.757). There was no difference in MACE rates between iFR- and FFR-guided strategies in both women (5.4% vs. 5.6%, adjusted hazard ratio: 1.10; 95% confidence interval: 0.50 to 2.43; p = 0.805) and men (6.6% vs. 7.0%, adjusted hazard ratio: 0.98; 95% confidence interval: 0.66 to 1.46; p = 0.919).

CONCLUSIONS

An FFR-guided strategy was associated with a higher rate of revascularization than iFR-guided strategy in men, but not in women. However, iFR- and FFR-guided strategies showed comparable clinical outcomes, regardless of sex. (Functional Lesion Assessment of Intermediate Stenosis to guide Revascularization [DEFINE-FLAIR]; NCT02053038).

Sex Differences in Coronary Computed Tomography Angiography-Derived Fractional Flow Reserve: Lessons From ADVANCE

OBJECTIVES

This study is to determine the management and clinical outcomes of patients investigated with coronary computed tomography angiography (CCTA)-derived fractional flow reserve (FFR_CT) according to sex.

BACKGROUND

Women are underdiagnosed with conventional ischemia testing, have lower rates of obstructive coronary artery disease (CAD) at invasive coronary angiography (ICA), yet higher mortality compared to men. Whether FFR_CT improves sex-based patient management decisions compared to CCTA alone is unknown.

METHODS

Subjects with symptoms and CAD on CCTA were enrolled (2015 to 2017). Demographics, symptom status, CCTA anatomy, coronary volume to myocardial mass ratio (V/M), lowest FFR_CT values, and management plans were captured. Endpoints included reclassification rate between CCTA and FFR_CT management plans, incidence of ICA demonstrating obstructive CAD (≥50% stenosis) and revascularization rates.

RESULTS

A total of 4,737 patients (n = 1,603 females, 33.8%) underwent CCTA and FFR_CT. Women were older (age 68 ± 10 years vs. 65 ± 10 years; p < 0.0001) with more atypical symptoms (41.5% vs. 33.9%; p < 0.0001). Women had less obstructive CAD (65.4% vs. 74.7%; p < 0.0001) at CCTA, higher FFR_CT (0.76 ± 0.10 vs. 0.73 ± 0.10; p < 0.0001), and lower likelihood of positive FFR_CT ≤ 0.80 for the same degree stenosis (p < 0.0001). A positive FFR_CT ≤0.80 resulted in equal referral to ICA (n = 510 [54.5%] vs. n = 1,249 [56.5%]; p = 0.31), but more nonobstructive CAD (n = 208 [32.1%] vs. n = 354 [24.5%]; p = 0.0003) and less revascularization (n = 294 [31.4%] vs. n = 800 [36.2%]; p < 0.0001) in women, unless the FFR_CT was ≤0.75 where revascularization rates were similar (n = 253 [41.9%] vs. n = 715 [46.4%]; p = 0.06). Women have a higher V/M ratio (26.17 ± 7.58 mm³/g vs. 24.76 ± 7.22 mm³/g; p < 0.0001) that is associated with higher FFR_CT independent of degree stenosis (p < 0.001). Predictors of revascularization included stenosis severity, FFR_CT, symptoms, and V/M ratio (p < 0.001) but not female sex (p = 0.284).

CONCLUSIONS

FFR_CT differs between the sexes, as women have a higher FFR_CT for the same degree of stenosis. In FFR_CT-positive CAD, women have less obstructive CAD at ICA and less revascularization, which is associated with higher V/M ratio. The findings suggest that CAD and FFR_CT variations by sex need specific interpretation as these differences may affect therapeutic decision making and clinical outcomes. (Assessing Diagnostic Value of Non-invasive FFRCT in Coronary Care [ADVANCE]; NCT02499679).

Influence of Sex on Relationship Between Total Anatomical and Physiologic Disease Burdens and Their Prognostic Implications in Patients With Coronary Artery Disease

Background Total atherosclerosis disease burden is associated with clinical outcomes in patients with coronary artery disease. However, the influence of sex on the relationship between total anatomical and physiologic disease burdens and their prognostic implications have not been well defined. Methods and Results A total of 1136 patients who underwent fractional flow reserve (FFR) measurement in all 3 major coronary arteries were included in this study. Anatomical and physiologic total disease burden was assessed by SYNTAX (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery) score, residual SYNTAX score, a total sum of FFR in 3 vessels (3-vessel FFR), and functional SYNTAX score. The primary end point was major adverse cardiac events, a composite of cardiac death, myocardial infarction, and ischemia-driven revascularization at 2 years. There were no differences in angiographic diameter stenosis, SYNTAX score, or residual SYNTAX score between women and men. However, both per-vessel FFR (0.89±0.10 versus 0.87±0.11, P<0.001) and 3-vessel FFR (2.72±0.13 versus 2.69±0.15, P<0.001) were higher in women. Multivariable Cox regression analyses showed that total anatomical and physiologic disease burdens were significantly associated with 2-year major adverse cardiac events, and there was no significant interaction between sex and total disease burden for clinical outcomes. Conclusions Despite similar angiographic disease severity, both per-vessel and per-patient physiologic disease severity was less in women than in men. There was no influence of sex on prognostic implications of total anatomical and physiologic disease burdens in patients with coronary artery disease. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT01621438.

Utility of Imaging Modalities in Coronary Lesions With Borderline Fractional Flow Reserve

BACKGROUND

Coronary intervention is routinely deferred in intermediate lesions with fractional flow reserve (FFR) ≥ 0.80. Patients with borderline FFR (0.80-0.85) who were initially deferred, have been shown to have higher risk of future interventions; however, the data is limited, and the long term prognosis in these patients remains unknown. We assessed the utility of adjunctive imaging modalities to determine the need for intervention in lesions with borderline FFR.

METHODS

We retrospectively evaluated consecutive patients who underwent coronary angiography at Einstein Medical Center from January 2013 to April 2016. All patients with borderline FFR (0.80-0.85) were included. Patients were divided into Defer or Perform intervention groups based on additional available or procured clinical data. The Perform group was further stratified into intervention With or Without adjunctive imaging guidance (including intravascular ultrasound, optical coherence tomography, echocardiography, and exercise or pharmacologic stress test). Follow-up data was collected for all patients, which included future target lesion revascularization (TLR) and major adverse cardiac events (MACE; all-cause and cardiovascular mortality and acute coronary syndromes).

RESULTS

A total of 196 patients were eligible. Median (IQR) FFR in Perform and Defer groups was 0.81 (0.8-0.83) and 0.84 (0.82-0.85) respectively. Median (IQR) follow up was 21 (13-29) and 25 (15-36) months respectively. Overall MACE rate in Perform group (n = 101) was 20.8% (n = 21) and Defer group (n = 95) was 15.8% (n = 15). The stratified MACE rate in Perform group With imaging guidance (n = 57) was 17.5% (n = 10) and Without imaging guidance (n = 44) was 25% (n = 11). Overall, the FFR only guided management (n = 196) led to MACE rate of 18.4% (n = 36); whereas, FFR With imaging guidance (n = 136) led to MACE rate of 16.2% (n = 22). The p values were non-significant in each of the above group comparisons due to relatively low numbers with trends as noted.

CONCLUSIONS

Our study suggests that intervention of coronary lesions with borderline FFR under imaging guidance, although not significant, trends towards improved cardiovascular outcomes compared with intervention in this group without adjunctive imaging. These findings are merely speculative without achieving statistical significance in a small subset and need to be further validated in a large scale prospective study.

Fractional Flow Reserve-Based Coronary Artery Bypass Surgery: Current Evidence and Future Directions

Fractional flow reserve (FFR) provides an objective measurement of the severity of ischemia caused by coronary stenoses in downstream myocardial regions. Data from the interventional cardiology realm have suggested benefits of a FFR-guided percutaneous coronary intervention (PCI) strategy. Limited evidence is available on the use of FFR to guide coronary artery bypass grafting (CABG). The most recent data have shown that FFR might simplify CABG procedures and optimize patency of arterial grafts without any clear impact on clinical outcomes. The aim of this review was to summarize the available data on FFR-based CABG and discuss the rationale and potential consequences of a switch toward FFR-based surgical revascularization strategy.

The prognostic significance of coronary flow reserve in the risk stratification of patients with chronic total occlusion of the right coronary artery and the intermediary stenosis of the left coronary artery

Introduction: Coronary Flow Reserve (CFR) is a clinically useful, non-invasive diagnostic method for assessing the functional ability of coronary arteries and it is important for their long-term follow-up in patients. However, CFR has not always been sufficiently investigated in previous studies. Objective: To examine the prognostic significance of CFR in the risk stratification of patients with chronic total occlusion of the right coronary artery (RCA) and the intermediary stenosis of the left coronary artery (LAD). Material and Methods: Number of 71 patients, mean age 64 ± 7 years, (84%) patients male, having LAD stenosis, diameter 50-70%, and CTO of RCA, were referred for noninvasive estimation of functional significance of LAD stenosis. Transthoracic Doppler echocardiography was used to obtain coronary flow velocities in the distal segment of LAD. Patients were followed for the mean period of 18.3 ± 7.1 months for the occurrence of composite end point including cardiovascular death, myocardial infarction, bypass surgery and PCI. Results: During the follow-up period, there were a total of 23 adverse events (4 deaths, 2 myocardial infarction, 7 bypass surgeries and 10 PCI). Patients with CFR < 2 had significantly more adverse events (n = 9; 56.3% vs. n = 14; 25.5%; p = 0.021), they were significantly older (68 ± 9 vs. 62 ± 6; p = 0.011), with a higher incidence of a positive family history (14; 87.5% vs. 26; 47.3%; p = 0.039), as well as a significantly higher frequency of three-dose coronary disease (14; 87.5% vs. 30; 54.5%; p = 0.017). Using Kaplan-Meier estimator, we obtained that patients with CFR < 2 have a significantly shorter average period without unwanted event (15.4 ± 2.8 months vs 23.5 ± 1.1 months, Log Rank 7.407; p = 0.008). Conclusion: CFR plays an important role in stratifying the risk of patients with CTO of RCA and the intermediary stenosis of LAD.

Instantaneous wave-free ratio and fractional flow reserve in clinical practice

Objectives

To compare fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) measurements in an all-comer patient population with moderate coronary artery stenoses.

Background

Visual assessment of the severity of coronary artery stenoses is often discordant in moderate lesions. FFR allows reliable functional severity assessment in these cases but requires adenosine-induced hyperaemia with associated additional time, costs and side effects. The iFR is a hyperaemia-independent index.

Methods and results

Between November 2015 and February 2017, 356 consecutive patients were included in whom 515 coronary stenoses were measured using both iFR and FFR. Mean iFR and FFR were 0.90 ± 0.09 and 0.86 ± 0.08, respectively. iFR correlated well with FFR [r = 0.75; p < 0.001]. Receiver operating characteristic analysis identified an area under the curve of 0.92. An iFR-only strategy with a treatment cut-off ≤0.89 revealed a diagnostic classification agreement with the FFR-only strategy in 420 lesions (82%) with a sensitivity of 87%, a specificity of 80%, a positive predictive value of 56% and a negative predictive value of 96%.

Conclusions

Real-time iFR measurements have good negative predictive value compared to FFR, but moderate diagnostic accuracy (82%). It exposes fewer patients to adenosine, reduces procedure time and costs. Further prospective trials are needed to evaluate specific clinical settings, cut-off values and endpoints.

Right Ventricular Perfusion

Regulation of blood flow to the right ventricle differs significantly from that to the left ventricle. The right ventricle develops a lower systolic pressure than the left ventricle, resulting in reduced extravascular compressive forces and myocardial oxygen demand. Right ventricular perfusion has eight major characteristics that distinguish it from left ventricular perfusion: (1) appreciable perfusion throughout the entire cardiac cycle; (2) reduced myocardial oxygen uptake, blood flow, and oxygen extraction; (3) an oxygen extraction reserve that can be recruited to at least partially offset a reduction in coronary blood flow; (4) less effective pressure–flow autoregulation; (5) the ability to downregulate its metabolic demand during coronary hypoperfusion and thereby maintain contractile function and energy stores; (6) a transmurally uniform reduction in myocardial perfusion in the presence of a hemodynamically significant epicardial coronary stenosis; (7) extensive collateral connections from the left coronary circulation; and (8) possible retrograde perfusion from the right ventricular cavity through the Thebesian veins. These differences promote the maintenance of right ventricular oxygen supply–demand balance and provide relative resistance to ischemia-induced contractile dysfunction and infarction, but they may be compromised during acute or chronic increases in right ventricle afterload resulting from pulmonary arterial hypertension. Contractile function of the thin-walled right ventricle is exquisitely sensitive to afterload. Acute increases in pulmonary arterial pressure reduce right ventricular stroke volume and, if sufficiently large and prolonged, result in right ventricular failure. Right ventricular ischemia plays a prominent role in these effects. The risk of right ventricular ischemia is also heightened during chronic elevations in right ventricular afterload because microvascular growth fails to match myocyte hypertrophy and because microvascular dysfunction is present. The right coronary circulation is more sensitive than the left to α-adrenergic–mediated constriction, which may contribute to its greater propensity for coronary vasospasm. This characteristic of the right coronary circulation may increase its vulnerability to coronary vasoconstriction and impaired right ventricular perfusion during administration of α-adrenergic receptor agonists.

Functional evaluation of sublingual microcirculation indicates successful weaning from VA-ECMO in cardiogenic shock

Background

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly adopted for the treatment of cardiogenic shock (CS). However, a marker of successful weaning remains largely unknown. Our hypothesis was that successful weaning is associated with sustained microcirculatory function during ECMO flow reduction. Therefore, we sought to test the usefulness of microcirculatory imaging in the same sublingual spot, using incident dark field (IDF) imaging in assessing successful weaning from VA-ECMO and compare IDF imaging with echocardiographic parameters.

Methods

Weaning was performed by decreasing the VA-ECMO flow to 50% (F₅₀) from the baseline. The endpoint of the study was successful VA-ECMO explantation within 48 hours after weaning. The response of sublingual microcirculation to a weaning attempt (WA) was evaluated. Microcirculation was measured in one sublingual area (single spot (ss)) using CytoCam IDF imaging during WA. Total vessel density (TVDss) and perfused vessel density (PVDss) of the sublingual area were evaluated before and during 50% flow reduction (TVDss_F50, PVDss_F50) after a WA and compared to conventional echocardiographic parameters as indicators of the success or failure of the WA.

Results

Patients (n = 13) aged 49 ± 18 years, who received VA-ECMO for the treatment of refractory CS due to pulmonary embolism (n = 5), post cardiotomy (n = 3), acute coronary syndrome (n = 2), myocarditis (n = 2) and drug intoxication (n = 1), were included. TVDss_F50 (21.9 vs 12.9 mm/mm², p = 0.001), PVDss_F50 (19.7 vs 12.4 mm/mm², p = 0.01) and aortic velocity–time integral (VTI) at 50% flow reduction (VTI_F50) were higher in patients successfully weaned vs not successfully weaned. The area under the curve (AUC) was 0.99 vs 0.93 vs 0.85 for TVDss_F50 (small vessels) >12.2 mm/mm², left ventricular ejection fraction (LVEF) >15% and aortic VTI >11 cm. Likewise, the AUC was 0.91 vs 0.93 vs 0.85 for the PVDss_F50 (all vessels) >14.8 mm/mm², LVEF >15% and aortic VTI >11 cm.

Conclusion

This study identified sublingual microcirculation as a novel potential marker for identifying successful weaning from VA-ECMO. Sustained values of TVDss_F50 and PVDss_F50 were found to be specific and sensitive indicators of successful weaning from VA-ECMO as compared to echocardiographic parameters.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1855-2) contains supplementary material, which is available to authorized users.

Multi-Detector Coronary CT Imaging for the Identification of Coronary Artery Stenoses in a "Real-World" Population

BACKGROUND

Multi-detector computed tomography (CT) has emerged as a modality for the non-invasive assessment of coronary artery disease (CAD). Prior studies have selected patients for evaluation and have excluded many of the “real-world” patients commonly encountered in daily practice. We compared 64-detector-CT (64-CT) to conventional coronary angiography (CA) to investigate the accuracy of 64-CT in determining significant coronary stenoses in a “real-world” clinical population.

METHODS

A total of 1,818 consecutive patients referred for 64-CT were evaluated. CT angiography was performed using the GE LightSpeed VCT (GE^® Healthcare). Forty-one patients in whom 64-CT results prompted CA investigation were further evaluated, and results of the two diagnostic modalities were compared.

RESULTS

A total of 164 coronary arteries and 410 coronary segments were evaluated in 41 patients (30 men, 11 women, age 39–85 years) who were identified by 64-CT to have significant coronary stenoses and who thereafter underwent CA. The overall per-vessel sensitivity, specificity, positive predictive value, negative predictive value, and accuracy at the 50% stenosis level were 86%, 84%, 65%, 95%, and 85%, respectively, and 77%, 93%, 61%, 97%, and 91%, respectively, in the per-segment analysis at the 50% stenosis level.

CONCLUSION

64-CT is an accurate imaging tool that allows a non-invasive assessment of significant CAD with a high diagnostic accuracy in a “real-world” population of patients. The sensitivity and specificity that we noted are not as high as those in prior reports, but we evaluated a population of patients that is typically encountered in clinical practice and therefore see more “real-world” results.