Is it time to measure fractional flow reserve in all patients?

Prognostic differences between physiology-guided percutaneous coronary intervention and optimal medical therapy in coronary artery disease: A systematic review and meta-analysis

Background

Intracoronary physiology, particularly fractional flow reserve (FFR), has been used as a guide for revascularization for patients with coronary artery disease (CAD). The optimal treatment in the physiological grey-zone area has been unclear and remains subject to ongoing debate.

Methods

We conducted a systematic review of randomized controlled trials and observational studies comparing the prognostic effect of percutaneous coronary revascularization (PCI) and optimal medical therapy (OMT) in patients with CAD. Studies were identified by medical literature databases. The outcomes of interest were major adverse cardiac events (MACE) and its components, death, myocardial infarction (MI), and repeat revascularization.

Results

A total of 16 studies with 27,451 patients were included. The pooled analysis demonstrated that PCI was associated with a prognostic advantage over OMT in patients with FFR value ≤0.80 (RR: 0.64, 95 % CI: 0.45-0.90, p < 0.01). Patients with an FFR value >0.80 were shown to benefit more from OMT (RR 1.38, 95 % CI 1.24-1.53, p < 0.01). The analysis also showed that there was no significant difference in MACE in the grey-zone area (FFR 0.75-0.80) (RR 0.64, 95 % CI: 0.35-1.16, p = 0.14), but a significant reduction in repeat revascularization (RR 0.54, 95 % CI, 0.31-0.91, p < 0.01) when patients were treated with PCI.

Conclusions

Among patients with CAD and FFR values >0.80, OMT was associated with favorable outcomes over PCI in reducing the risk of MACE. However, among patients with FFR values ≤0.80, revascularization was superior in terms of reducing MACE. The available evidence supports the guideline-recommended use of an FFR cut-off of ≤0.80.

Accuracy and Reproducibility of Coronary Angiography-Derived Fractional Flow Reserve in the Assessment of Coronary Lesion Severity

Purpose

Coronary angiography-derived fractional flow reserve (caFFR) is a novel computational flow dynamics (CFD)-derived assessment of coronary vessel flow with good diagnostic performance. Herein, we performed a retrospective study to evaluate the reproducibility of caFFR findings between observers and investigate the diagnostic performance of caFFR for coronary stenosis defined as FFR ≤0.80, especially in the grey zone (0.75≤caFFR ≤0.80).

Patients and Methods

A total of 150 patients (167 coronary vessels) underwent caFFR (with FlashAngio used for calculation of flow variables) and subsequent invasive fractional flow reserve (FFR) measurements. Outcomes, including reproducibility, were compared for vessels in and outside the grey zone.

Results

The correlation of caFFR findings was good between the two laboratories (r = 0.723, p<0.001). The AUC of ROC were both high for caFFR-CoreLab1 and caFFR-CoreLab2 (0.975 and 0.883). The diagnostic accuracy, sensitivity, specificity, and negative and positive predictive values were not significantly different between the two laboratories (p>0.05). caFFR had a strong correlation with measures to FFR (r=0.911, p<0.001). There was no systematic difference between caFFR and FFR on Bland-Altman analysis in and outside the grey zone. There was no difference in diagnostic accuracy between the grey and non-grey zones in the prediction of FFR ≤0.80 (p=0.09).

Conclusion

The inter-observer reproducibility for caFFR was high, and the diagnostic accuracy of caFFR was good compared to that of FFR.

Comparison Between 5- and 1-Year Outcomes Using Cutoff Values of Pressure Drop Coefficient and Fractional Flow Reserve for Diagnosing Coronary Artery Diseases

Background

The current pressure-based coronary diagnostic index, fractional flow reserve (FFR), has a limited efficacy in the presence of microvascular disease (MVD). To overcome the limitations of FFR, the objective is to assess the recently introduced pressure drop coefficient (CDP), a fundamental fluid dynamics-based combined pressure–flow index.

Methods

We hypothesize that CDP will result in improved clinical outcomes in comparison to FFR. To test the hypothesis, chi-square test was performed to compare the percent major adverse cardiac events (%MACE) at 5 years between (a) FFR < 0.75 and CDP > 27.9 and (b) FFR < 0.80 and CDP > 25.4 groups using a prospective cohort study. Furthermore, Kaplan–Meier survival curves were compared between the FFR and CDP groups. The results were considered statistically significant for p < 0.05. The outcomes of the CDP arm were presumptive as clinical decision was solely based on the FFR.

Results

For the complete patient group, the %MACE in the CDP > 27.9 group (10 out of 35, 29%) was lower in comparison to the FFR < 0.75 group (11 out of 20, 55%), and the difference was near significant (p = 0.05). The survival analysis showed a significantly higher survival rate (p = 0.01) in the CDP > 27.9 group (n = 35) when compared to the FFR < 0.75 group (n = 20). The results remained similar for the FFR = 0.80 cutoff. The comparison of the 5-year MACE outcomes with the 1-year outcomes for the complete patient group showed similar trends, with a higher statistical significance for a longer follow-up period of 5 years.

Conclusion

Based on the MACE and survival analysis outcomes, CDP could possibly be an alternate diagnostic index for decision-making in the cardiac catheterization laboratory.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT01719016.

The relationship between the basal coronary translesional pressure ratio and fractional flow reserve

AIM

Fractional flow reserve (FFR) allows for physiological definition of coronary lesion severity but requires induction of maximal coronary circulation hyperemia with administration of adenosine leading to coronary resistive vessel vasodilatation. However, the hyperemic response to adenosine, and therefore the calculation of FFR, may be affected by dysfunction of the coronary microvasculature. The aim was to define the relationship between basal P_d /P_a and FFR and identify lesion-independent predictors of the change in P_d /P_a with hyperemia.

METHODS AND RESULTS

One hundred and sixty-six consecutive patients undergoing FFR measurement were prospectively enrolled (mean age 62.6 ± 10.3 years, 27% females). Basal P_d /P_a , FFR, and delta P_d /P_a (difference between basal P_d /P_a and FFR) were recorded. Independent predictors of delta P_d /P_a included angiographic lesion severity, lesion length, gender, body mass index, and total cholesterol:HDL cholesterol ratio. The best basal P_d /P_a cutoff value to predict lesion physiological significance was 0.87 (positive predictive value of 100% for an FFR value ≤0.80) and the best cutoff for nonsignificance was 0.93 (negative predictive value of 98% for an FFR value >0.80).

CONCLUSION

The delta P_d /P_a may be affected by patient gender, body mass index, and cholesterol profile. A basal P_d /P_a value of ≥0.93 is highly predictive of an FFR >0.80. Conversely, a basal P_d /P_a value of ≤0.87 is highly predictive of an FFR ≤0.80. © 2017 Wiley Periodicals, Inc.

Comparison of instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR)--first real world experience

BACKGROUND

The instantaneous wave-free ratio (iFR) is a new adenosine-independent index of coronary stenosis severity. Most published data have been based on off-line analyses of pressure recordings in a core laboratory. We prospectively compared real-time iFR and fractional flow reserve (FFR) measurements.

METHODS AND RESULTS

iFR and FFR were measured in 151 coronary stenoses in 108 patients. Repeated iFR measurements were technically simple, showed excellent agreement [rs=0.99; p<0.0001], and the mean difference between consecutive iFR values was 0.0035 (limits of agreement: -0.019, 0.026). Mean iFR showed a significant correlation with FFR [rs=0.81; p<0.0001]. Receiver-operating characteristic analysis identified an optimal iFR cut-off value of 0.896 for categorization based on an FFR cut-off value 0.8. We compared two different iFR-based diagnostic strategies (iFR-only and hybrid iFR-FFR) with standard FFR: The iFR-only strategy showed good classification agreement (83.4%) with standard FFR. Use of the hybrid iFR-FFR strategy, assessing lesions in an iFR-gray zone of 0.86-0.93 by FFR, improved classification accuracy to 94.7%, and diagnosis would have been established in 61% of patients without adenosine-induced hyperemia. Notably, both iFR and FFR values were significantly higher in the posterior coronary vessels.

CONCLUSIONS

Real-time iFR measurements are easily performed, have excellent diagnostic performance and confirm available off-line core laboratory data. The excellent agreement between repeated iFR measurements demonstrates the reliability of single measurements. Combining iFR with FFR in a hybrid strategy enhances diagnostic accuracy, exposing fewer patients to adenosine. Overall, iFR is a promising method, but still requires prospective clinical endpoint trial evaluation.

Combined functional and anatomical diagnostic endpoints for assessing arteriovenous fistula dysfunction

Failure of arteriovenous fistulas (AVF) to mature and thrombosis in matured fistulas have been the major causes of morbidity and mortality in hemodialysis patients. Stenosis, which occurs due to adverse remodeling in AVFs, is one of the major underlying factors under both scenarios. Early diagnosis of a stenosis in an AVF can provide an opportunity to intervene in a timely manner for either assisting the maturation process or avoiding the thrombosis. The goal of surveillance strategies was to supplement the clinical evaluation (i.e., physical examination) of the AVF for better and earlier diagnosis of a developing stenosis. Surveillance strategies were mainly based on measurement of functional hemodynamic endpoints, including blood flow (Q_a) to the vascular access and venous access pressure (VAP). As the changes in arterial pressure (MAP) affects the level of VAP, the ratio of VAP to MAP (VAPR = VAP/MAP) was used for diagnosis. A Q_a < 400-500 mL/min or a VAPR > 0.55 is considered sign of significant stenosis, which requires immediate intervention. However, due to the complex nature of AVFs, the surveillance strategies have failed to consistently detect stenosis under different scenarios. VAPR has been primarily developed to detect outflow stenosis in arteriovenous grafts, and it hasn’t been successful in accurate diagnosis of outflow lesions in AVFs. Similarly, AVFs can maintain relatively high blood flow despite the presence of a significant outflow stenosis and thus, Q_a has been found to be a better predictor of only inflow lesions. Similar shortcomings have been reported in the detection of functional severity of coronary stenosis using diagnostic endpoints that were based on either flow or pressure. This limitation has been associated with the fact that both pressure and flow change in the presence of a stenosis and thus, hemodynamic diagnostic endpoints that employ only one of these parameters are inherently prone to inaccuracies. Recent attempts have resulted in development of new diagnostic endpoints that can combine the effects of pressure and flow. These new hemodynamic diagnostic endpoints have shown to be better predictors of functional severity of lesions as compared to either flow or pressure based counterparts. In this review article, we discussed the advantages and limitations of current functional and anatomical diagnostic endpoints in AVFs.

The impact of gender on fractional flow reserve measurements

AIMS

Fractional flow reserve (FFR) allows accurate investigation of the functional significance of intermediate coronary stenoses. The present study set out to study the impact of gender on FFR measurements.

METHODS AND RESULTS

Three hundred and seventeen intermediate (40-70% at angiography) stenoses were assessed with FFR in 270 patients (mean age 65.8 ± 10.3 years, 84 females). Resting Pd/Pa (the ratio of mean blood pressure measured distal to the stenosis to mean aortic blood pressure in resting conditions), FFR (Pd/Pa during adenosine-induced hyperaemia) and the ΔPd/Pa (calculated as the change in Pd/Pa during hyperaemia) were measured. There was no difference in the location and degree of stenoses between genders (p>0.5). Similarly, there was no difference in age and in the prevalence of cardiovascular risk factors (all p>0.2). Resting Pd/Pa also did not differ between genders (0.92 ± 0.08 vs. 0.93 ± 0.05, p=0.23). In response to adenosine, however, a significantly larger ΔPd/Pa (0.14 ± 0.07 vs. 0.11 ± 0.07, p=0.001) and a significantly lower FFR (0.79 ± 0.12 vs. 0.82 ± 0.10, p=0.008) were observed in males. This difference was maintained in a multivariate regression analysis.

CONCLUSIONS

We observed gender-based differences in FFR data in daily routine. Further studies are necessary to test the mechanism of this observation and how these differences impact on the assessment of haemodynamically relevant stenoses.

Coronary flow reserve by transthoracic echocardiography predicts epicardial intimal thickening in cardiac allograft vasculopathy

Cardiac allograft vasculopathy (CAV) is the leading cause of morbidity and mortality in heart transplantation (HT). We sought to investigate the role of coronary flow reserve (CFR) by contrast-enhanced transthoracic echocardiography (CE-TTE) in CAV diagnosis. CAV was defined as maximal intimal thickness (MIT) assessed by intravascular ultrasound (IVUS) > or =0.5 mm. CFR was assessed in the left anterior descending coronary artery in 22 HT recipients at 6 +/- 4 years post-HT. CAV was diagnosed in 10 patients (group A), 12 had normal coronaries (group B). The mean MIT was 0.7 +/- 0.1 mm (range 0.03-1.8). MIT was higher in group A (1.16 +/- 0.3 mm vs. 0.34 +/- 0.07 mm, p < 0.0001). CFR was 3.1 +/- 0.8 in all patients and lower in group A (2.5 +/- 0.6 vs. 3.7 +/- 0.3, p < 0.0001). CFR was inversely related with MIT (r =-0.774, p < 0.0001). A cut point of < or =2.9, identified as optimal by receiver operating characteristics analysis was 100% specific and 80% sensitive (PPV = 100%, NPV = 89%, Accuracy = 91%). CFR assessment by CE-TTE is a novel noninvasive diagnostic tool in the detection of CAV defined as MIT > or =0.5 mm. CFR by CE-TTE may reduce the need for routine IVUS in HT.

Influence of coronary collateral flow on coronary diagnostic parameters: an in vitro study

Functional severity of coronary stenosis is often assessed using diagnostic parameters. These parameters are evaluated from the combined pressure and/or flow measurements taken at the site of the stenosis. However, when there are functional collaterals operating downstream to the stenosis, the coronary flow-rate increases, and the pressure in the stenosed artery is altered. This effect of downstream collaterals on different diagnostic parameters is studied using a physiological representative in vitro coronary flow-loop. The three diagnostic parameters tested are fractional flow reserve (FFR), lesion flow coefficient (LFC), and pressure drop coefficient (CDP). The latter two were discussed in recent publications by our group (Banerjee et al., 2007, 2008, 2009). They are evaluated for three different severities of stenosis and tested for possible misinterpretation in the presence of variable collateral flows. Pressure and flow are measured with and without downstream collaterals. The diagnostic parameters are then calculated from these readings. In the case of intermediate stenosis (80% area blockage), FFR and LFC increased from 0.74 to 0.77 and 0.58 to 0.62, respectively, for no collateral to fully developed collateral flow. Also, CDP decreased from 47 to 42 for no collateral to fully developed collateral flow. These changes in diagnostic parameters might lead to erroneous postponement of coronary intervention. Thus, variability in diagnostic parameters for the same stenosis might lead to misinterpretation of stenosis severity in the presence of operating downstream collaterals.

Evaluation of intermediate coronary stenosis with intravascular ultrasound and fractional flow reserve: Its use and abuse

Clinical decision making in patients with intermediate coronary stenosis is still debated. Intravascular ultrasound (IVUS) examination and/or functional assessment of coronary stenosis by fractional flow reserve (FFR) are currently used to define the severity of such lesions. There are very few studies with a small sample size that have a head-to-head comparison between IVUS and FFR in the evaluation of angiographically de novo intermediate lesions. There are no randomized, controlled trials to demonstrate the superiority of IVUS versus FFR in providing improved clinical outcomes in comparison with angiography alone. However, the issue of superiority might be irrelevant, because IVUS and FFR could be complementary techniques to be used in the catheterization laboratory to provide critical anatomic and functional data that permit more accurate decisions in the management of the patient.

The effect of drug eluting stents on cardiovascular events in patients with intermediate lesions and borderline fractional flow reserve

OBJECTIVE

To assess the role of fractional flow reserve (FFR) in guiding therapy in the drug eluting stent (DES) era.

BACKGROUND

FFR is a useful index for evaluation of the physiological significance of angiographically indeterminate coronary artery lesions. However, its role in the DES era is unknown.

METHODS

Long term outcome of 281 patients with angiographically indeterminate coronary lesions and borderline FFR (0.75 </= FFR < 0.9) was obtained. The outcome of patients who had a DES placed (n = 58), was compared with that of consecutive patients with borderline FFR that were treated by PCI with bare metal stents (BMS, n = 58), or were deferred from revascularization (n = 165).

RESULTS

FFR was significantly higher in the deferred group (median and IQR); 0.85 (0.82 to 0.88) compared with the BMS (0.78; 0.76 to 0.82) and the DES (0.79; 0.77 to 0.82), P < 0.001. Pretreatment FFR was a significant determinant of long term event rates in the deferred patients (P = 0.002) but had no effect in patients treated by PCI. In the deferred group, there were fewer events (death, myocardial infarction, target vessel revascularization) compared with the BMS group; but no significant difference was observed between the DES and the deferred groups.

CONCLUSIONS

In borderline FFR, long term outcome after PCI with BMS is inferior to conservative therapy or PCI with DES. While conservative management is preferable in these patients, PCI with DES may be considered in specific circumstances.

Functional and anatomical diagnosis of coronary artery stenoses

BACKGROUND

Functional/physiological evaluation of coronary artery stenoses may be more important than anatomical measurements of severity. Optimization of thresholds for stenosis intervention and treatment endpoints depend on coupling functional hemodynamic and anatomical data. We sought to develop a single prognostic parameter correlating stenosis-specific anatomy, pressure gradient, and velocities that could be measured during catheterization.

MATERIALS AND METHODS

In vivo Experiments were performed in six swine (41 +/- 3 kg). The lumen area of the left anterior descending coronary artery was measured with intravascular ultrasound. An angioplasty balloon was inflated to create the desired intraluminal area obstructions. Fractional flow reserve (FFR), coronary flow reserve (CFR), and hyperemic-stenosis-resistance index were measured distal to the balloon at peak hyperemia with 10 mg intracoronary papaverine. A functional index:pressure drop coefficient (CDP) and a combined functional and anatomical index:lesion flow coefficient (LFC) were calculated from measured hyperemic pressure gradient, velocity, and percentage area stenosis. P < 0.05 was considered statistically significant.

RESULTS

The CDP and LFC correlated linearly and significantly with FFR and CFR. The CDP (R(2) = 0.72, P < 0.0001) correlated better than LFC (R(2) = 0.19, P < 0.003) with hyperemic-stenosis-resistance index. When LFC was correlated simultaneously with FFR and CFR, R(2) improved to 0.82 (P < 0.0001). Inclusion of percentage area stenoses concurrently with FFR and CFR marginally improved the correlation with LFC.

CONCLUSIONS

A dimensionless parameter combining measured pressure gradient, velocity, and area reduction data can optimally define the severity of coronary stenoses based on our preliminary results and could prove useful clinically.

Rationale and design of the Fractional Flow Reserve versus Angiography for Multivessel Evaluation (FAME) study

BACKGROUND

Although its limitations for diagnosing critical coronary artery disease are well described, coronary angiography remains the predominant method for guiding decisions about stent implantation in patients with multivessel coronary artery disease. However, some have suggested that invasive physiologic guidance may improve decision making.

TRIAL DESIGN

The objective of this multicenter, randomized clinical trial is to compare the efficacy of 2 strategies, one based on angiographic guidance to one based on physiologic guidance with fractional flow reserve (FFR), for deciding which coronary lesions to stent in patients with multivessel coronary disease. Eligible patients must have coronary narrowings > 50% diameter stenosis in > or = 2 major epicardial vessels, > or = 2 of which the investigator feels require drug-eluting stent placement. Patients with previous coronary bypass surgery or left main coronary disease are excluded. Based on angiographic evaluation, the investigator notes the lesions that require stenting. The patient is then randomly assigned to either angiographic guidance or FFR guidance. Patients assigned to angiographic guidance undergo stenting as planned. Patients assigned to FFR guidance first have FFR measured in each diseased vessel and only undergo stenting if the FFR is < or = 0.80. The primary end point of the study is a composite of major adverse cardiac events, including death, myocardial infarction, and repeat coronary revascularization, at 1 year. Secondary end points will include the individual adverse events, cost-effectiveness, quality of life, and 30-day, 6-month, 2-year, and 5-year outcomes.

CONCLUSION

The FAME study will examine for the first time in a large, multicenter, randomized fashion the role of measuring FFR in patients undergoing multivessel percutaneous coronary intervention.

Correlation between the tissue Doppler, strain rate, strain imaging during the dobutamine infusion and coronary fractional flow reserve during catheterization: a comparative study

Coronary fractional flow reserve (FFR) as an invasive, and dobutamine stress echocardiography (DSE) as a noninvasive technique were used to detect critical coronary stenosis. This study was undertaken to assess correlation between these two techniques by using tissue Doppler, strain rate (SR), and strain imaging (S).

METHODS

In 17 patients (aged 54.9+/-12.6, 4 F), a total of 22 vessels were studied. On dobutamine stress echocardiography, baseline and peak systolic (Sm), early (Em) and late (Am) diastolic myocardial velocities, SR and S were recorded from parasternal view (mid-posterior segment) for radial and apical view (mid-septum) for longitudinal deformation. Then coronary FFR was performed by using intracoronary adenosine infusion, and the value of < or = 0.75 was accepted as critical coronary stenosis.

RESULTS

FFR was found to be significant in 10 vessels (FFR critical). Baseline Sm, Em/Am, SR, S values, and peak Em/Am, SR, S values were similar between critical or noncritical FFR groups. Baseline Sm and Em, and change between baseline and peak Sm and S were significantly higher in noncritical FFR group (p < 0.01, < 0.05, < 0.001, < 0.001, respectively). In all vessels, FFR after adenosine infusion showed a poor correlation with WMSI, Em, Am, Em/Am values, and the change in SR values (r = -0.22, 0.16, -0.14, 0.21, 18, respectively) showed a good correlation with the change in S (r = 0.51; p = 0.014), and a very good correlation with the change in Sm values (r = 0.77; p < 0.001) during DSE. When FFR values at left coronary system were analyzed for longitudinal SR and S values, it had a mild correlation with SR (r = 0.47, p = 0.044) and a good correlation with S (r = 0.66, p = 0.002).

CONCLUSION

The quantification of regional myocardial deformation by using DSE rather than the motion would be more appropriate in detecting the ischemic dysfunctional segment supplied by the critical coronary stenosis. Strain measurement during the dobutamine infusion may provide an information on the FFR results of the culprit vessel.

Guidelines for percutaneous coronary interventions. The Task Force for Percutaneous Coronary Interventions of the European Society of Cardiology

In patients with stable CAD, PCI can be considered a valuable initial mode of revascularization in all patients with objective large ischaemia in the presence of almost every lesion subset, with only one exception: chronic total occlusions that cannot be crossed. In early studies, there was a small survival advantage with CABG surgery compared with PCI without stenting. The addition of stents and newer adjunctive medications improved the outcome for PCI. The decision to recommend PCI or CABG surgery will be guided by technical improvements in cardiology or surgery, local expertise, and patients' preference. However, until proved otherwise, PCI should be used only with reservation in diabetics with multi-vessel disease and in patients with unprotected left main stenosis. The use of drug-eluting stents might change this situation. Patients presenting with NSTE-ACS (UA or NSTEMI) have to be stratified first for their risk of acute thrombotic complications. A clear benefit from early angiography (<48 h) and, when needed, PCI or CABG surgery has been reported only in the high-risk groups. Deferral of intervention does not improve outcome. Routine stenting is recommended on the basis of the predictability of the result and its immediate safety. In patients with STEMI, primary PCI should be the treatment of choice in patients presenting in a hospital with PCI facility and an experienced team. Patients with contra-indications to thrombolysis should be immediately transferred for primary PCI, because this might be their only chance for quickly opening the coronary artery. In cardiogenic shock, emergency PCI for complete revascularization may be life-saving and should be considered at an early stage. Compared with thrombolysis, randomized trials that transferred the patients for primary PCI to a 'heart attack centre' observed a better clinical outcome, despite transport times leading to a significantly longer delay between randomization and start of the treatment. The superiority of primary PCI over thrombolysis seems to be especially clinically relevant for the time interval between 3 and 12 h after onset of chest pain or other symptoms on the basis of its superior preservation of myocardium. Furthermore, with increasing time to presentation, major-adverse-cardiac-event rates increase after thrombolysis, but appear to remain relatively stable after primary PCI. Within the first 3 h after onset of chest pain or other symptoms, both reperfusion strategies seem equally effective in reducing infarct size and mortality. Therefore, thrombolysis is still a viable alternative to primary PCI, if it can be delivered within 3 h after onset of chest pain or other symptoms. Primary PCI compared with thrombolysis significantly reduced stroke. Overall, we prefer primary PCI over thrombolysis in the first 3 h of chest pain to prevent stroke, and in patients presenting 3-12 h after the onset of chest pain, to salvage myocardium and also to prevent stroke. At the moment, there is no evidence to recommend facilitated PCI. Rescue PCI is recommended, if thrombolysis failed within 45-60 min after starting the administration. After successful thrombolysis, the use of routine coronary angiography within 24 h and PCI, if applicable, is recommended even in asymptomatic patients without demonstrable ischaemia to improve patients' outcome. If a PCI centre is not available within 24 h, patients who have received successful thrombolysis with evidence of spontaneous or inducible ischaemia before discharge should be referred to coronary angiography and revascularized accordingly--independent of 'maximal' medical therapy.

Simultaneous assessment of fractional and coronary flow reserves in cardiac transplant recipients: Physiologic Investigation for Transplant Arteriopathy (PITA Study)

BACKGROUND

The utility of measuring fractional flow reserve (FFR) to assess cardiac transplant arteriopathy has not been evaluated. Measuring coronary flow reserve (CFR) as well as FFR could add information about the microcirculation, but until recently, this has required two coronary wires. We evaluated a new method for simultaneously measuring FFR and CFR with a single wire to investigate transplant arteriopathy.

METHODS AND RESULTS

In 53 cases of asymptomatic cardiac transplant recipients without angiographically significant coronary disease, FFR and thermodilution-derived CFR (CFRthermo) were measured simultaneously with the same coronary pressure wire in the left anterior descending artery and compared with volumetric intravascular ultrasound (IVUS) imaging. The average FFR was 0.88+/-0.07; in 75% of cases, the FFR was less than the normal threshold of 0.94; and in 15% of cases, the FFR was < or =0.80, the upper boundary of the gray zone of the ischemic threshold. There was a significant inverse correlation between FFR and IVUS-derived measures of plaque burden, including percent plaque volume (r=0.55, P<0.0001). The average CFRthermo was 2.5+/-1.2; in 47% of cases, CFRthermo was < or =2.0. In 14%, the FFR was normal (> or =0.94) and the CFR was abnormal (<2.0), suggesting predominant microcirculatory dysfunction.

CONCLUSIONS

FFR correlates with IVUS findings and is abnormal in a significant proportion of asymptomatic cardiac transplant patients with normal angiograms. Simultaneous measurement of CFR with the same pressure wire, with the use of a novel coronary thermodilution technique, is feasible and adds information to the physiological evaluation of these patients.