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

Traditional Cardiovascular Risk Factors and Coronary Microvascular Dysfunction in Women and Men: A Single-Center Study

INTRODUCTION

Coronary microvascular dysfunction (CMD) is common in patients with and without obstructive epicardial coronary artery disease (CAD). Risk factors for the development of CMD have not been fully elucidated, and data regarding sex-associated differences in traditional cardiovascular risk factors for obstructive CAD in patients with CMD are lacking.

METHODS

In this single-center, prospective registry, we enrolled patients with nonobstructive CAD undergoing clinically indicated invasive assessment of coronary microvascular function between November 2019 and March 2023. Associations between coronary microvascular dysfunction, traditional cardiovascular risk factors, and sex were assessed using univariate and multivariate regression models.

RESULTS

Overall, 245 patients with nonobstructive CAD were included in the analysis (62.9% female; median age 68 (interquartile range: 59, 75). Microvascular dysfunction was diagnosed in 141 patients (57.5%). The prevalence of microvascular dysfunction was similar in women and men (59.0% vs. 57.0%; p = 0.77). No association was found between traditional risk factors for coronary atherosclerosis and CMD regardless of whether CMD was structural or functional. In women, but not in men, older age and the presence of previous ischemic heart disease were associated with lower coronary flow reserve (β = -0.29; p < 0.01 and β = -0.15; p = 0.05, respectively) and lower resistive reserve ratio (β = -0.28; p < 0.01 and β = -0.17; p = 0.04, respectively).

CONCLUSION

For the entire population, no association was found between coronary microvascular dysfunction and traditional risk factors for coronary atherosclerosis. In women only, older age and previous ischemic heart disease were associated with coronary microvascular dysfunction. Larger studies are needed to elucidate risk factors for CMD.

Functional Assessment of Long-Term Microvascular Cardiac Allograft Vasculopathy

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a leading cause of death and retransplantation following heart transplantation (HTX). Surveillance angiography performed yearly is indicated for the early detection of the disease, but it remains of limited sensitivity.

METHODS

We performed bolus thermodilution-based coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) and fractional flow reserve (FFR) measurements in HTX patients undergoing yearly surveillance coronary angiography without overt CAV.

RESULTS

In total, 27 HTX patients were included who had 52 CFR, IMR, and FFR measurements at a mean of 43 months after HTX. Only five measurements were performed in the first year. CFR decreased significantly by 0.13 every year (p = 0.04) and IMR tended to increase by 0.98 every year (p = 0.051), whereas FFR did not change (p = 0.161) and remained well above 0.80 over time. After one year, CFR decreased significantly (p = 0.022) and IMR increased significantly (p = 0.015), whereas FFR remained unchanged (p = 0.72).

CONCLUSIONS

The functional status of the epicardial coronary arteries of transplanted hearts did not deteriorate over time. On the contrary, a significant decrease in CFR was noted. In view of the increasing IMR, this is caused by the deterioration of the function of microvasculature. CFR and IMR measurements may provide an early opportunity to diagnose CAV.

CT Coronary Angiography and Dynamic CT Myocardial Perfusion for Detection of Cardiac Allograft Vasculopathy

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a major obstacle limiting long-term graft survival. Effective noninvasive surveillance modalities reflecting both coronary artery and microvascular components of CAV are needed.

OBJECTIVES

The authors evaluated the diagnostic performance of dynamic computed tomography-myocardial perfusion imaging (CT-MPI) and coronary computed tomography angiography (CCTA) for CAV.

METHODS

A total of 63 heart transplantation patients underwent combined CT-MPI and CCTA plus invasive coronary angiography (ICA) with intravascular ultrasonography (IVUS) between December 2018 and October 2021. The median interval between CT-MPI and heart transplantation was 4.3 years. Peak myocardial blood flow (MBF) of the whole myocardium (MBF_global) and minimum MBF (MBF_min) among the 16 segments according to the American Heart Association model, except the left ventricular apex, were calculated from CT-MPI. CCTA was assessed qualitatively, and the degree of coronary artery stenosis was recorded. CAV was diagnosed based on both ICA (ISHLT criteria) and IVUS. Patients were followed up for a median time of 2.3 years after CT-MPI and a median time of 5.7 years after transplantation.

RESULTS

Among the 63 recipients, 35 (55.6%) had diagnoses of CAV. The median MBF_global and MBF_min were significantly lower in patients with CAV (128.7 vs 150.4 mL/100 mL/min; P = 0.014; and 96.9 vs 122.8 mL/100 mL/min; P < 0.001, respectively). The combined use of coronary artery stenosis on CCTA and MBF_min showed the highest diagnostic performance with an area under the curve of 0.886 (sensitivity: 74.3%, specificity: 96.4%, positive predictive value: 96.3%, and negative predictive value: 75.0%).

CONCLUSIONS

The combination of CT-MPI and CCTA demonstrated excellent diagnostic performance for the detection of CAV. One-stop evaluation of the coronary artery and microvascular components involved in CAV using combined CCTA and CT-MPI may be a potent noninvasive screening method for early detection of CAV.

Prognostic value of myocardial flow reserve obtained by 82-rubidium positron emission tomography in long-term follow-up after heart transplantation

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a leading cause of death following heart transplantation (HTx) and non-invasive prognostic methods in long-term CAV surveillance are needed. We evaluated the prognostic value of myocardial flow reserve (MFR) obtained by 82-rubidium (82Rb) positron emission tomography (PET).

METHODS

Recipients undergoing dynamic rest-stress 82Rb PET between April 2013 and June 2017 were retrospectively evaluated in a single-center study. Evaluation by PET included quantitative myocardial blood flow and semiquantitative myocardial perfusion imaging. Patients were grouped by MFR (MFR ≤ 2.0 vs MFR > 2.0) and the primary outcome was all-cause mortality.

RESULTS

A total of 50 patients (68% men, median age 57 [IQR: 43 to 68]) were included. Median time from HTx to PET was 10.0 (6.7 to 16.0) years. In 58% of patients CAV was documented prior to PET. During a median follow-up of 3.6 (2.3 to 4.3) years 12 events occurred. Survival probability by Kaplan-Meier method was significantly higher in the high-MFR group (log-rank P = .02). Revascularization (n = 1), new CAV diagnosis (n = 1), and graft failure (n = 4) were more frequent in low-MFR patients. No retransplantation occurred.

CONCLUSIONS

Myocardial flow reserve appears to offer prognostic value in selected long-term HTx recipients and holds promise as a non-invasive method for CAV surveillance possibly guiding management strategy.

Comparison of Diagnostic Value Between STE+LDDSE and CMR-FT for Evaluating Coronary Microvascular Obstruction in Post-PCI Patients for STEMI

Background

Coronary microvascular obstruction (CMVO) is closely associated with poor prognosis of ST-segment elevation myocardial infarction (STEMI) patients. However, data showing the comparison between cardiac magnetic resonance feature tracking (CMR-FT) and speckle tracking echocardiography (STE) combined with low-dose dobutamine stress echocardiography (LDDSE) in evaluating CMVO was scarcely available. We aimed to explore and compare the predictive value between CMR-FT and STE+LDDSE in detecting CMVO.

Methods

Sixty-one STEMI patients were executed cardiac magnetic resonance and echocardiography within the first 5–7 days after primary percutaneous coronary intervention (PCI). The myocardial strain analysis was performed in STE, STE+LDDSE, and CMR-FT, and strain parameters included radial strain (RS), circumferential strain (CS), and longitudinal strain (LS). ROC curves were performed to predict infarcted myocardium segments with CMVO.

Results

Finally, 324 infarcted myocardium segments were analyzed, including 100 infarcted segments with CMVO and 224 segments without CMVO by the gold standard assessment of late gadolinium-enhancement cardiac magnetic resonance imaging (LGE-CMR). The results showed that CS was generally superior to RS and LS in identifying CMVO. CS in CMR-FT facilitated the detection of CMVO, with a sensitivity, specificity, and accuracy of 78.00%, 81.25%, and 80.25%, respectively. The sensitivity, specificity, and accuracy of CS in STE combined with LDDSE were better than STE alone (76.00% vs 60.00%, 79.91% vs 64.29%, and 78.70% vs 62.96%, P < 0.05). In addition, CMR-FT is not superior to STE+LDDSE for detection of CMVO (P > 0.05).

Conclusion

Low-dose dobutamine can improve the clinical value of STE for evaluating CMVO in STEMI patients. Compared with CMR-FT, STE+LDDSE might be a better choice for STEMI patients because of its safety, convenience, and low-cost.

Prognostic value of comprehensive intracoronary physiology assessment early after heart transplantation

AIMS

We evaluated the long-term prognostic value of invasively assessing coronary physiology after heart transplantation in a large multicentre registry.

METHODS AND RESULTS

Comprehensive intracoronary physiology assessment measuring fractional flow reserve (FFR), the index of microcirculatory resistance (IMR), and coronary flow reserve (CFR) was performed in 254 patients at baseline (a median of 7.2 weeks) and in 240 patients at 1 year after transplantation (199 patients had both baseline and 1-year measurement). Patients were classified into those with normal physiology, reduced FFR (FFR ≤ 0.80), and microvascular dysfunction (either IMR ≥ 25 or CFR ≤ 2.0 with FFR > 0.80). The primary outcome was the composite of death or re-transplantation at 10 years. At baseline, 5.5% had reduced FFR; 36.6% had microvascular dysfunction. Baseline reduced FFR [adjusted hazard ratio (aHR) 2.33, 95% confidence interval (CI) 0.88-6.15; P = 0.088] and microvascular dysfunction (aHR 0.88, 95% CI 0.44-1.79; P = 0.73) were not predictors of death and re-transplantation at 10 years. At 1 year, 5.0% had reduced FFR; 23.8% had microvascular dysfunction. One-year reduced FFR (aHR 2.98, 95% CI 1.13-7.87; P = 0.028) and microvascular dysfunction (aHR 2.33, 95% CI 1.19-4.59; P = 0.015) were associated with significantly increased risk of death or re-transplantation at 10 years. Invasive measures of coronary physiology improved the prognostic performance of clinical variables (χ2 improvement: 7.41, P = 0.006). However, intravascular ultrasound-derived changes in maximal intimal thickness were not predictive of outcomes.

CONCLUSION

Abnormal coronary physiology 1 year after heart transplantation was common and was a significant predictor of death or re-transplantation at 10 years.

Validation of Coronary Angiography-Derived Vessel Fractional Flow Reserve in Heart Transplant Patients with Suspected Graft Vasculopathy

Cardiac transplant-related vasculopathy remains a leading cause of morbidity and mortality in heart transplant (HTx) recipients. Recently, coronary angiography-derived vessel fractional flow reserve (vFFR) has emerged as a new diagnostic computational tool to functionally evaluate the severity of coronary artery disease. Although vFFR estimates have been shown to perform well against invasive FFR in atherosclerotic coronary artery disease, data on the use of vFFR in heart transplant recipients suffering from cardiac transplant-related arteriopathy are lacking. The aim of the presented study was to validate coronary angiography-derived vessel fractional flow reserve to calculate fractional flow reserve in HTx patients with and without cardiac transplant-related vasculopathy. A prospective, single center study of HTx patients referred for annual check-up, undergoing surveillance coronarography was conducted. Invasive FFR was measured using a motorized device at the speed of 1.0 mm/s in all three major coronary arteries. Angiography-derived pullback FFR was derived from the angiogram and compared with invasive FFR pullback curve. Overall, 18,059 FFR values were extracted from the FFR pullback curves from 23 HTx patients. The mean age was 59.3 ± 9.7 years, the mean time after transplantation was 5.24 years [IQR 1.20, 11.25]. A total of 39 vessels from 23 patients (24 LAD, 11 LCX, 4 RCA) were analyzed. Mean distal vFFR was 0.87 ± 0.14 whereas invasive distal FFR was 0.88 ± 0.17. An excellent correlation was found between invasive distal FFR and vFFR (r = 0.92; p < 0.001). The correlation of the pullback tracing was high, with a correlation coefficient between vFFR and invasive FFR pullback values of 0.72 (95% CI 0.71 to 0.73, p < 0.001). The mean difference between vFFR and invasive FFR pullback values was -0.01 with 0.06 of SD (limits of agreements -0.12 to 0.13). In HTx patients, coronary angiography-derived FFR correlates excellently with invasively measured wire-derived FFR. Therefore, angiography derived FFR could be used as a novel diagnostic tool to quantify the functional severity of graft vasculopathy.

CT-derived fractional flow reserve (FFRct) for functional coronary artery evaluation in the follow-up of patients after heart transplantation

OBJECTIVES

Invasively measured fractional flow reserve (FFR) is associated with outcome in heart transplant (HTx) patients. Coronary computed tomography angiography (CCTA)-derived FFR (FFRct) provides additional functional information from anatomical CT images. We describe the first use of FFRct in HTx patients.

METHODS

HTx patients underwent CCTA with FFRct to screen for cardiac allograft vasculopathy. FFRct was measured distal to each coronary stenosis > 30% and FFRct ≤ 0.8 indicated hemodynamically significant stenosis. FFRct was also measured at the most distal location of each vessel. Overall distal FFRct was calculated as the mean of the distal values in the left, right, and circumflex coronary artery in each patient.

RESULTS

Seventy-three patients (age 56 (42-65) years, 63% males) at 11 (8-16) years after HTx were included. Eighteen (25%) patients had a focal hemodynamically significant stenosis (stenosis > 30% with FFRct ≤ 0.8). In the 55 patients without a hemodynamically significant focal FFRct stenosis (FFRct > 0.80), the distal left anterior descending artery FFRct was < 0.90 in 74% of the patients and 10 (18%) patients had ≥ 1 coronary artery with a distal FFRct ≤ 0.8, including 1 with a distal FFRct ≤ 0.8 in all coronaries. Overall distal FFRct in patients without focal stenosis was 0.88 (0.86-0.91), 0.87 (0.86-0.90), and 0.88 (0.86-0.91) (median with 25th-75th percentile) at 5-9, 10-14, or ≥ 15 years post-transplantation, respectively (p = 0.93).

CONCLUSIONS

FFRct performed on CCTA scans of HTx patients demonstrated that 25% of patients had a focal coronary stenosis with FFRct ≤ 0.8. Even without a focal stenosis, FFRct values are often abnormal in HTx patients.

KEY POINTS

• This is the first report describing the use of FFRct in in heart transplant patients. • FFRct identifies patients after heart transplantation with hemodynamically significant coronary stenosis. • Even without a focal stenosis, FFRct values are often abnormal in heart transplant patients.

Cardiac allograft vasculopathy after heart transplantation: Pathophysiology, detection approaches, prevention, and treatment management

Cardiac allograft vasculopathy (CAV) continues to be a significant risk factor for the recipient's long-term survival following heart transplantation. Our knowledge of its etiology is constantly changing as new imaging techniques provide direct insight into the disease's natural history. CAV identification continues to be difficult since symptoms may be varied or nonexistent. Due to the irreversible nature of the disease, early diagnosis is critical to halting development. Prognostic tools and biomarkers have proliferated as a result of advancements in diagnostic techniques. Simultaneously, pharmaceutical advancements have aided in the amelioration of the disease's progressive progression.

Imaging of Cardiac Transplantation: An Overview

Heart transplantation (HTx) remains the optimal treatment for selected patients with end-stage advanced heart failure. However, survival is limited early by acute rejection and long term by cardiac allograft vasculopathy (CAV). Even though the diagnosis of rejection is based on histology, cardiac imaging provides a pivotal role for early detection and severity assessment of these hazards. The present review focuses on the use and reliability of different invasive and non-invasive imaging modalities to detect and monitor CAV and rejection after HTx. Coronary angiography remains the corner stone in routine CAV surveillance. However, angiograms are invasive and underestimates the CAV severity especially in the early phase. Intravascular ultrasound and optical coherence tomography are invasive methods for intracoronary imaging that detects early CAV lesions not evident by angiograms. Non-invasive imaging can be divided into myocardial perfusion imaging, anatomical/structural imaging and myocardial functional imaging. The different non-invasive imaging modalities all provide clinical and prognostic information and may have a gatekeeper role for invasive monitoring. Acute rejection and CAV are still significant clinical problems after HTx. No imaging modality provides complete information on graft function, coronary anatomy and myocardial perfusion. However, a combination of invasive and non-invasive modalities at different stages following HTx should be considered for optimal personalized surveillance and risk stratification.

Effect of Sex Difference of Coronary Microvascular Dysfunction on Long-Term Outcomes in Deferred Lesions

OBJECTIVES

This study investigated the sex difference of long-term cardiovascular outcomes on coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) in patients with deferred coronary artery lesions.

BACKGROUND

Coronary microvascular dysfunction is associated with poorer long-term outcomes. It can be assessed by CFR and the IMR.

METHODS

The study prospectively enrolled 434 patients (133 women and 301 men) and analyzed CFR, IMR, fractional flow reserve, and quantitative coronary angiography. Clinical outcomes were assessed by major adverse cardiovascular event(s) (MACE) of cardiac death, myocardial infarction, and revascularization during 5 years of follow-up. The study protocol was approved by the Institutional Review Board or Ethics Committee at each participating center, and all patients provided written informed consent. The study protocol was in accordance with the Declaration of Helsinki.

RESULTS

Women had milder epicardial disease compared with men (fractional flow reserve: 0.91 [interquartile range (IQR): 0.87 to 0.96] vs. 0.90 [IQR: 0.86 to 0.95]; p = 0.037). IMR was similar between the sexes, but CFR was lower in women (2.69 [IQR: 2.08 to 3.90] vs. 3.20 [IQR: 2.20 to 4.31]; p = 0.006) due to a shorter resting mean transit time, whereas hyperemic mean transit times were similar. At 5-year follow-up, MACE was significantly lower in women compared with men (1.1% vs. 5.5%; p = 0.017). Sex, diabetes mellitus, and CFR were independent predictors for MACE for all patients. The risk of MACE was significantly higher in men with low versus high CFR (hazard ratio: 4.58; 95% confidence interval: 1.85 to 11.30; p = 0.011) which was not seen in women.

CONCLUSIONS

There was no sex difference in microvascular function by IMR. CFR was lower in women due to a higher resting coronary flow; however, long-term clinical outcomes in deferred lesions were better in women compared with men. (Clinical, Physiological and Prognostic Implication of Microvascular Status; NCT02186093).

Vessel Fractional Flow Reserve and Graft Vasculopathy in Heart Transplant Recipients

Background

Cardiac allograft vasculopathy (CAV) remains the Achilles' heel of long-term survival after heart transplantation (HTx). The severity and extent of CAV is graded with conventional coronary angiography (COR) which has several limitations. Recently, vessel fractional flow reserve (vFFR) derived from COR has emerged as a diagnostic computational tool to quantify the functional severity of coronary artery disease.

Purpose

The present study assessed the usefulness of vFFR to detect CAV in HTx recipients.

Methods

In HTx patients referred for annual check-up, undergoing surveillance COR, the extent of CAV was graded according to the criteria proposed by the international society of heart and lung transplantation (ISHLT). In addition, three-dimensional coronary geometries were constructed from COR to calculate pressure losses using vFFR.

Results

In 65 HTx patients with a mean age of 53.7 ± 10.1 years, 8.5 years (IQR 1.90, 15.2) years after HTx, a total number of 173 vessels (59 LAD, 61 LCX, and 53 RCA) were analyzed. The mean vFFR was 0.84 ± 0.15 and median was 0.88 (IQR 0.79, 0.94). A vFFR ≤ 0.80 was present in 24 patients (48 vessels). HTx patients with a history of ischemic cardiomyopathy (ICMP) had numerically lower vFFR as compared to those with non-ICMP (0.70 ± 0.22 vs. 0.79 ± 0.13, p = 0.06). The use of vFFR reclassified 31.9% of patients compared to the anatomical ISHLT criteria. Despite a CAV score of 0, a pathological vFFR ≤ 0.80 was detected in 8 patients (34.8%).

Conclusion

The impairment in epicardial conductance assessed by vFFR in a subgroup of patients without CAV according to standard ISHLT criteria suggests the presence of a diffuse vasculopathy undetectable by conventional angiography. Therefore, we speculate that vFFR may be useful in risk stratification after HTx.

The role of optical coherence tomography and other intravascular imaging modalities in cardiac allograft vasculopathy

Orthotopic heart transplantation (OHT) is the standard-of-care for end-stage heart disease. Although a significant improvement in the prognosis of patients after OHT has been observed in recent years, their overall mortality remains relatively high, with a median survival of approximately 10 years after transplantation. One of the primary causes of death in patients after OHT is cardiac allograft vasculopathy (CAV), the condition developing specifically in the coronary vasculature after OHT, the pathophysiology of which is still inadequately known. It is estimated that CAV development and progression is responsible for approximately 30% of deaths within five years post-OHT. According to the International Society for Heart and Lung Transplantation (ISHLT) Nomenclature for CAV, its presence should be assessed primarily by the coronary angiography performed routinely after OHT, mostly due to its wide availability, reproducibility, and low complication rate. However, the analysis of CAV in coronary angiography has limitations, mostly concerning its - sometimes inadequate - sensitivity and specificity. Hence, there is a growing need for the introduction of more accurate methods of CAV assessment, such as intravascular imaging, which through a thorough evaluation of the arterial wall structure and thickness allows the drawbacks of routine angiography to be minimised. The aim of the article was to critically summarise the current findings derived from the analysis of CAV by optical coherence tomography, the other intravascular imaging modalities, such as intravascular ultrasound (IVUS) and IVUS-derived virtual histology, along with physiological assessment with the use of the fractional flow reserve.

Coronary computed tomography-angiography quantitative plaque analysis improves detection of early cardiac allograft vasculopathy: A pilot study

Cardiac allograft vasculopathy (CAV) is an increasingly important complication after cardiac transplant. We assessed the additive diagnostic benefit of quantitative plaque analysis in patients undergoing coronary computed tomography-angiography (CCTA). Consecutive patients undergoing CCTA for CAV surveillance were identified. Scans were visually interpreted for coronary stenosis. Semiautomated software was used to quantify noncalcified plaque (NCP), as well as its components. Optimal diagnostic cut-offs for CAV, with coronary angiography as gold standard, were defined using receiver operating characteristic curves. In total, 36 scans were identified in 17 patients. CAV was present in 17 (46.0%) reference coronary angiograms, at a median of 1.9 years before CCTA. Median NCP (147 vs 58, P < .001), low-density NCP (median 4.5 vs 0.9, P = .003), fibrous plaque (median 76.1 vs 31.1, P = .003), and fibrofatty plaque (median 63.6 vs 27.6, P < .001) volumes were higher in patients with CAV, whereas calcified plaque was not (median 0.0 vs 0.0, P = .510). Visual assessment of CCTA alone was 70.6% sensitive and 100% specific for CAV. The addition of total NCP volume increased sensitivity to 82.4% while maintaining 100% specificity. NCP volume is significantly higher in patients with CAV. The addition of quantitative analysis to visual interpretation improves the sensitivity for detecting CAV without reducing specificity.

Dose-Response Relationship Between Intracoronary Acetylcholine and Minimal Lumen Diameter in Coronary Endothelial Function Testing of Women and Men With Angina and No Obstructive Coronary Artery Disease

BACKGROUND

Intracoronary acetylcholine (Ach) provocation testing is the gold standard for assessing coronary endothelial function. However, dosing regimens of Ach are quite varied in the literature, and there are limited data evaluating the optimal dose. We evaluated the dose-response relationship between Ach and minimal lumen diameter (MLD) by sex and studied whether incremental intracoronary Ach doses given during endothelial function testing improve its diagnostic utility.

METHODS

We evaluated 65 men and 212 women with angina and no obstructive coronary artery disease who underwent endothelial function testing using the highest tolerable dose of intracoronary Ach, up to 200 μg. Epicardial endothelial dysfunction was defined as a decrease in MLD >20% after intracoronary Ach by quantitative coronary angiography. We used a linear mixed effects model to evaluate the dose-response relationship. Deming regression analysis was done to compare the %MLD constriction after incremental doses of intracoronary Ach.

RESULTS

The mean age was 53.5 years. Endothelial dysfunction was present in 186 (68.1%). Among men with endothelial dysfunction, there was a significant decrease in MLD/10 µg of Ach at doses above 50 μg and 100 µg, while this decrease in MLD was not observed in women (P<0.001). The %MLD constriction at 20 μg versus 50 μg and 50 μg versus 100 μg were not equivalent while the %MLD constriction at 100 μg versus 200 μg were equivalent.

CONCLUSIONS

Women and men appear to have different responses to Ach during endothelial function testing. In addition to having a greater response to intracoronary Ach at all doses, men also demonstrate an Ach-MLD dose-response relationship with doses up to 200 μg, while women have minimal change in MLD with doses above 50 µg. An incremental dosing regimen during endothelial function testing appears to improve the diagnostic utility of the test and should be adjusted based on the sex of the patient.

In vitro test-retest repeatability of invasive physiological indices to assess coronary flow

AIMS

Several invasive techniques are available in clinical practice to assess coronary flow. Nevertheless, the test-retest repeatability of these techniques in a controlled setting has not been reported. Therefore, we sought to evaluate fractional flow reserve (FFR), coronary flow reserve (CFR), index of microvascular resistance (IMR), and absolute coronary blood flow (ABF) with absolute microvascular resistance (AMR) test-retest repeatability using a coronary flow simulator.

METHODS AND RESULTS

Using a coronary flow simulator (FFR WetLab version 2.0; Abbott Vascular, Santa Clara, CA), we created stenoses ranging from 0% to 70%, with 10% increments. Three different flows were established with their hyperemic phases, and two consecutive measurements were obtained, evaluating the following indices: FFR, CFR, IMR, ABF, and AMR, using a pressure/temperature wire and an infusion catheter. One hundred and thirty-eight pairs of measurements were performed. Test-retest reliability was compared in 48 FFR, 18 CFR, 24 IMR, 24 ABF, and 24 AMR. Test-retest repeatability showed excellent reproducibility for FFR, ABF, and AMR; respectively 0.98 (0.97-0.99), 0.92 (0.81-0.97) and 0.91 (0.79-0.96) (P < 0.0001 for all). However, test-retest repeatability was weaker for IMR and poor for CFR; respectively 0.53 (0.16-0.77) (P = 0.006) and 0.27 (-0.26-0.67) (P = 0.30).

CONCLUSIONS

Using a coronary flow simulator, FFR and ABF with AMR had excellent test-retest reliability. IMR and CFR demonstrated weaker test-retest reliability.

Coronary CTA for Surveillance of Cardiac Allograft Vasculopathy

PURPOSE OF REVIEW

The purpose of this review is to highlight recent hardware and software advances in coronary computed tomography angiography (CTA) that make it a potentially viable alternative to invasive coronary angiography for surveillance of cardiac allograft vasculopathy (CAV) in heart transplant recipients.

RECENT FINDINGS

Dual-source CT, multisegment reconstruction, and intracycle motion correction algorithms are all technologies applied during or after image acquisition that can improve image quality and diagnostic accuracy in patients with elevated heart rates, such as heart transplant recipients. CT fractional flow reserve may also add value in this clinical scenario.

SUMMARY

Coronary CTA now has equivalent diagnostic accuracy, offers more nuanced anatomic information, is inherently safer, and could be less costly than invasive coronary angiography. For these reasons, coronary CTA may now be a viable alternative to ICA for CAV surveillance in heart transplant recipients.

Comprehensive morphologic and functional imaging of heart transplant patients: first experience with dynamic perfusion CT

OBJECTIVES

We aimed to assess the diagnostic performance of a combined protocol with coronary computed tomography angiography (CCTA) and stress CT perfusion imaging (CTP) in heart transplant patients for comprehensive morphological and functional imaging.

METHODS

In this prospective study, 13 patients undergoing routine follow-up 8±6 years after heart transplantation underwent CCTA and dynamic adenosine stress CTP using a third-generation dual-source CT scanner, cardiac magnetic resonance (MR) adenosine stress perfusion imaging at 1.5 T, and catheter coronary angiography. In CCTA stenoses >50% luminal diameter narrowing were noted. Myocardial perfusion deficits were documented in CTP and MR. Quantitative myocardial blood flow (MBF) was calculated with CTP. Left ventricular ejection fraction was determined on cardiac MR cine images. Radiation doses of CT were determined.

RESULTS

One of the 13 patients had to be excluded because of severe motion artifacts. CCTA identified three patients with stenosis >50%, which were confirmed with catheter coronary angiography. CTP showed four patients with stress-induced myocardial hypoperfusion, which were confirmed by MR stress perfusion imaging. Quantitative analysis of global MBF showed lower mean values as compared to known reference values (MBF under stress 125.5 ± 34.5 ml/100 ml/min). Average left ventricular ejection fraction was preserved (56 ± 5%).

CONCLUSIONS

In heart transplant patients, a comprehensive CT protocol for the assessment of morphology and function including CCTA and CTP showed good concordance to results from MR perfusion imaging and catheter coronary angiography.

KEY POINTS

• Stress CT perfusion imaging enables the detection of myocardial ischemia • CT myocardial perfusion imaging can be combined with coronary computed tomography angiography • Combining perfusion and coronary CT imaging is accurate in heart transplant patients • CT myocardial perfusion imaging can be performed at a reasonable radiation dose.

Invasive Assessment of the Coronary Microvasculature

Traditionally, invasive coronary physiological assessment has focused on the epicardial coronary artery. More recently, appreciation of the importance of the coronary microvasculature in determining patient outcomes has grown. Several invasive modalities for interrogating microvascular function have been proposed. Angiographic techniques have been limited by their qualitative and subjective nature. Doppler wire-derived coronary flow reserve has been applied in research studies, but its clinical role has been limited by its lack of reproducibility, its lack of a clear normal value, and the fact that it is not specific for the microvasculature but interrogates the entire coronary circulation. The index of microcirculatory resistance—a thermodilution-derived measure of the minimum achievable microvascular resistance—is relatively easy to measure, more reproducible, has a clearer normal value, and is independent of epicardial coronary artery stenosis. The index of microcirculatory resistance has been shown to have prognostic value in patients with ST-segment–elevation myocardial infarction and cardiac allograft vasculopathy after heart transplantation. Emerging data demonstrate its role in evaluating patients with chest pain and nonobstructive coronary artery disease. Increasingly, the index of microcirculatory resistance is used as a reference standard for invasively assessing the microvasculature in clinical trials.

Fractional flow reserve and resting indices for coronary physiologic assessment: Practical guide, tips, and tricks

Physiologic assessment using fractional flow reserve (FFR) to guide percutaneous coronary interventions (PCI) has been demonstrated to improve clinical outcomes, compared to angiography-guided PCI. Recently, resting indices such as resting Pd/Pa, "instantaneous wave-free ratio", and contrast medium induced FFR have been evaluated for the assessment of the functional consequences of coronary lesions. Herein, we review and discuss the use of FFR and other indices for the functional assessment of coronary lesions. This review will cover theoretical aspects, as well as practical points and common pitfalls related to coronary physiological assessment. © 2017 Wiley Periodicals, Inc.

The effect of negative remodeling on fractional flow reserve after cardiac transplantation

BACKGROUND

Negative remodeling is a common occurrence early after cardiac transplantation. Its impact on the development of myocardial ischemia is not well documented. The aim of this study is to investigate the impact of negative remodeling on fractional flow reserve after cardiac transplantation.

METHODS

Thirty-four cardiac transplant recipients underwent intravascular ultrasound (IVUS) and fractional flow reserve (FFR) assessment soon after transplantation and one year later. Patients were divided into those with and without negative remodeling based on IVUS, and the impact on FFR was assessed. In the 19 patients with negative remodeling, there was no significant change in plaque volume (119.3±82.0 to 131.3±91.2mm³, p=0.21), but vessel volume (775.6±212.0 to 621.9±144.1mm³, p<0.0001) and lumen volume (656.3±169.1 to 490.7±132.0mm³, p<0.0001) decreased significantly and FFR likewise decreased significantly (0.88±0.06 to 0.84±0.07, p=0.04). In the 15 patients without negative remodeling, vessel volume did not change (711.7±217.6 to 745.7±198.5, p=0.28), but there was a significant increase in plaque volume (126.8±88.3 to 194.4±92.7, p<0.001) and a resultant significant decrease in FFR (0.89±0.05 to 0.85±0.05, p=0.01).

CONCLUSION

Negative remodeling itself, without any change in plaque volume can cause a significant decrease in fractional flow reserve after cardiac transplantation and appears to be another possible mechanism for myocardial ischemia.

Is ischemia the only factor predicting cardiovascular outcomes in all diabetes mellitus patients?

Diabetes mellitus (DM) is associated with an excess in cardiovascular morbidity and mortality, and is characterized by increased rates of coronary artery disease. Furthermore, once atherosclerosis is established, this is associated with an increased extent, complexity and a more rapid progression than seen in non-DM patients. Ischemia is the single most important predictor of future hard cardiac events and ischemia correction remains the cornerstone of current revascularization strategies. However recent data suggests that, in DM patients, coronary atherosclerosis despite the absence of ischemia, detected by either invasive or non-invasive methods, may not be associated with the same low risk of future cardiac events as seen in non-DM patients. This review seeks to examine the current evidence supporting an ischemia driven revascularization strategy, and to challenge the notion that ischemia is the only clinically relevant factor in the prediction of cardiovascular outcomes in all-comer DM patients. Specifically, we examine whether in DM patients certain characteristics beyond ischemia, such as microvascular disease, coronary atherosclerosis burden, progression and plaque composition, may need to be considered for a more refined risk stratification in these high-risk patients.

Randomised trial to compare a protective effect of Clopidogrel Versus TIcagrelor on coronary Microvascular injury in ST-segment Elevation myocardial infarction (CV-TIME trial)

AIMS

Ticagrelor has shown greater, more rapid and more consistent platelet inhibition than clopidogrel. However, the superiority of ticagrelor for preventing ischaemic damage in STEMI patients has not been proven. The aim of this trial was to assess whether ticagrelor is superior to clopidogrel in preventing microvascular injury in ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Patients with STEMI underwent prospective random assignment to receive a loading dose (LD) of clopidogrel 600 mg or ticagrelor 180 mg (1:1 ratio) before primary percutaneous coronary intervention (PCI). As the primary endpoint, the index of microcirculatory resistance (IMR) was measured immediately after primary PCI. The secondary endpoint was the infarct size estimated from the wall motion score index (WMSI). A total of 76 patients were enrolled (clopidogrel group=38, ticagrelor group=38). The IMR in the ticagrelor group was significantly lower than that in the clopidogrel group (22.2±18.0 vs. 34.4±18.8 U, p=0.005). Cardiac enzymes were less elevated in the ticagrelor group than in the clopidogrel group (CK peak; 2,651±1,710 vs. 3,139±2,698 ng/ml, p=0.06). Infarct size, estimated by WMSI, was not different between the ticagrelor and clopidogrel groups at baseline (1.55±0.30 vs. 1.61±0.29, p=0.41) or after three months (1.42±0.33 vs. 1.47±0.33, p=0.57).

CONCLUSIONS

In patients with STEMI treated by primary PCI, a 180 mg LD of ticagrelor might be more effective in reducing microvascular injury than a 600 mg LD of clopidogrel, as demonstrated by IMR immediately after primary PCI.

Does Pre-Treatment with High Dose Atorvastatin Prevent Microvascular Dysfunction after Percutaneous Coronary Intervention in Patients with Acute Coronary Syndrome?

Background and Objectives

There is controversy surrounding whether or not high dose statin administration before percutaneous coronary intervention (PCI) decreases peri-procedural microvascular injury. We performed a prospective randomized study to investigate the mechanisms and effects of pre-treatment high dose atorvastatin on myocardial damage in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS) undergoing PCI.

Subjects and Methods

Seventy seven patients with NSTE-ACS were randomly assigned to either the high dose group (atorvastatin 80 mg loading 12 to 24 h before PCI with a further 40 mg loading 2 h before PCI, n=39) or low dose group (atorvastatin 10 mg administration 12 to 24 h before PCI, n=38). Index of microcirculatory resistance (IMR) was measured after stent implantation. Creatine kinase-myocardial band (CK-MB) and high sensitivity C-reactive protein (CRP) levels were measured before and after PCI.

Results

The baseline characteristics were not different between the two patient groups. Compared to the low dose group, the high dose group had lower post PCI IMR (14.1±5.0 vs. 19.2±9.3 U, p=0.003). Post PCI CK-MB was also lower in the high dose group (median: 1.40 ng/mL (interquartile range [IQR: 0.75 to 3.45] vs. 4.00 [IQR: 1.70 to 7.37], p=0.002) as was the post-PCI CRP level (0.09 mg/dL [IQR: 0.04 to 0.16] vs. 0.22 [IQR: 0.08 to 0.60], p=0.001).

Conclusion

Pre-treatment with high dose atorvastatin reduces peri-PCI microvascular dysfunction verified by post-PCI IMR and exerts an immediate anti-inflammatory effect in patients with NSTE-ACS.

Effect of Sex Differences on Invasive Measures of Coronary Microvascular Dysfunction in Patients With Angina in the Absence of Obstructive Coronary Artery Disease

OBJECTIVES

This study investigated sex differences in coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) in patients with angina in the absence of obstructive coronary artery disease.

BACKGROUND

Coronary microvascular dysfunction is associated with worse long-term outcomes, especially in women. Coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) are 2 methods of assessing the coronary microcirculation.

METHODS

We prospectively enrolled 117 women and 40 men with angina in the absence of obstructive coronary artery disease. We performed CFR, IMR, fractional flow reserve, and quantitative coronary angiography in the left anterior descending artery. Coronary flow was assessed with a thermodilution method by obtaining mean transit time (Tmn) (an inverse correlate to absolute flow) at rest and hyperemia.

RESULTS

All patients had minimal atherosclerosis by quantitative coronary angiography (% diameter stenosis: 23.2 ± 12.3%), and epicardial disease was milder in women (fractional flow reserve: 0.88 ± 0.04 vs. 0.87 ± 0.04; p = 0.04). IMR was similar between the sexes (20.7 ± 9.8 vs. 19.1 ± 8.0; p = 0.45), but CFR was lower in women (3.8 ± 1.6 vs. 4.8 ± 1.9; p = 0.004). This was primarily due to a shorter resting Tmn in women (p = 0.005), suggesting increased resting coronary flow, whereas hyperemic Tmn was identical (p = 0.79). In multivariable analysis, female sex was an independent predictor of lower CFR and shorter resting Tmn.

CONCLUSIONS

Despite similar microvascular function in women and men by IMR, CFR is lower in women. This discrepancy appears to be due to differences in resting coronary flow between the sexes. The effect of sex differences should be considered in interpretation of physiological indexes using resting coronary flow.

[Fractional flow reserve and instantaneous wave-free ratio for the physiological assessment of coronary artery stenosis in the catheterization laboratory: Practical tips]

In recent years, a large body of evidence has revealed the limitations of angiographic evaluation in determining the physiological significance of coronary stenosis, particularly when these are intermediate lesions. Percutaneous coronary interventions (PCI) guided by physiological assessment using fractional flow reserve (FFR) have been shown to reduce cardiovascular events when compared to angiography alone. Recently, another coronary physiologic parameter has been introduced: the "instantaneous wave-free ratio" (iFR). In this review, we will discuss the FFR, the iFR, and their use in the functional assessment of coronary stenosis in the cardiac catheterization laboratory. This review will cover theoretical aspects for non-interventional cardiologists, as well as practice points and common pitfalls related to coronary physiological assessment for interventional cardiologists.

Invasive Assessment of Coronary Physiology Predicts Late Mortality After Heart Transplantation

BACKGROUND

The aim of this study is to determine the prognostic value of invasively assessing coronary physiology early after heart transplantation.

METHODS AND RESULTS

Seventy-four cardiac transplant recipients had fractional flow reserve, coronary flow reserve, index of microcirculatory resistance (IMR), and intravascular ultrasound performed down the left anterior descending coronary artery soon after (baseline) and 1 year after heart transplantation. The primary end point was the cumulative survival free of death or retransplantation at a mean follow-up of 4.5±3.5 years. The cumulative event-free survival was significantly lower in patients with a fractional flow reserve <0.90 at baseline (42% versus 79%; P=0.01) or an IMR ≥20 measured 1 year after heart transplantation (39% versus 69%; P=0.03). Patients in whom IMR decreased or did not change from baseline to 1 year had higher event-free survival compared with patients with an increase in IMR (66% versus 36%; P=0.03). Fractional flow reserve <0.90 at baseline (hazard ratio, 0.13; 95% confidence interval, 0.02-0.81; P=0.03), IMR ≥20 at 1 year (hazard ratio, 3.93; 95% confidence interval, 1.08-14.27; P=0.04), and rejection during the first year (hazard ratio, 6.00; 95% confidence interval, 1.56-23.09; P=0.009) were independent predictors of death/retransplantation, whereas intravascular ultrasound parameters were not.

CONCLUSIONS

Invasive measures of coronary physiology (fractional flow reserve and IMR) determined early after heart transplantation are significant predictors of late death or retransplantation.

Clinical Relevance of Coronary Fractional Flow Reserve: Art-of-state

Objective:

The objective was to delineate the current knowledge of fractional flow reserve (FFR) in terms of definition, features, clinical applications, and pitfalls of measurement of FFR.

Data Sources:

We searched database for primary studies published in English. The database of National Library of Medicine (NLM), MEDLINE, and PubMed up to July 2014 was used to conduct a search using the keyword term “FFR”.

Study Selection:

The articles about the definition, features, clinical application, and pitfalls of measurement of FFR were identified, retrieved, and reviewed.

Results:

Coronary pressure-derived FFR rapidly assesses the hemodynamic significance of individual coronary artery lesions and can readily be performed in the catheterization laboratory. The use of FFR has been shown to effectively guide coronary revascularization procedures leading to improved patient outcomes.

Conclusions:

FFR is a valuable tool to determine the functional significance of coronary stenosis. It combines physiological and anatomical information, and can be followed immediately by percutaneous coronary intervention (PCI) if necessary. The technique of FFR measurement can be performed easily, rapidly, and safely in the catheterization laboratory. By systematic use of FFR in dubious stenosis and multi-vessel disease, PCI can be made an even more effective and better treatment than it is currently. The current clinical evidence for FFR should encourage cardiologists to use this tool in the catheterization laboratory.

Epicardial Artery Stenosis with a High Index of Microcirculatory Resistance Is Frequently Functionally Insignificant as Estimated by Fractional Flow Reserve (FFR)

Objective Differences in microvascular integrity can diversely influence the functional assessment of epicardial coronary artery disease in each patient. We investigated the relevance of the index of microcirculatory resistance (IMR) and fractional flow reserve (FFR) of intermediate coronary lesions. Methods The IMR and FFR were measured in 67 intermediate coronary lesions of the left anterior descending artery of 67 patients, by using a pressure sensor/thermistor-tipped guidewire. Results To assess the differences in FFR in relationship to the IMR value, patients were divided into tertile IMR groups as follows: Low-IMR (n=22, IMR 14±3), Mid-IMR (n=23, IMR 21±2), and High-IMR (n=22, IMR 36±10). An analysis of variance showed that the High-IMR group had significantly higher FFR values (0.87±0.07) than the Low-IMR group (0.81±0.08) (p=0.03). Functionally significant lesions with FFR ≤0.8 accounted for 9% of lesions in the High-IMR group, 36% in the Low-IMR group and 22% in the Mid-IMR group (p=0.02). In the multivariate logistic analysis, the IMR value was an independent determinant of FFR ≤0.8 (p=0.03). Conclusion In patients with a high IMR, intermediate lesions as identified with visual estimation were more frequently functionally insignificant. The IMR can provide additional information in understanding the mismatch between the anatomical and functional severity of intermediate coronary stenosis.

Imaging in patients after cardiac transplantation and in patients with ventricular assist devices

The field of cardiac imaging and the management of patients with severe heart failure have advanced substantially during the past 10 years. Cardiac transplantation offers the best long-term survival with high quality of life for the patients with end stage heart failure. However, acute cardiac rejection and cardiac allograft vasculopathy (CAV) can occur post cardiac transplantation and these problems necessitate regular surveillance. The short-term success of mechanical circulatory support devices (MCSD), such as ventricular assist devices (VADs), in improving survival and quality of life has led to a dramatic growth of the patient population with these devices. The development of optimal imaging techniques and algorithms to evaluate these advanced heart failure patients is evolving and multimodality non-invasive imaging approaches and invasive techniques are commonly employed. Most of the published studies done in the transplant and VAD population are small, and biased based on the strength of the particular program, and there is a relative lack of published protocols to evaluate these patient groups. Moreover, the techniques of echocardiography, computed tomography (CT), magnetic resonance imaging, and nuclear cardiology have all progressed rapidly in recent years. There is thus a knowledge gap for cardiologists, radiologists, and clinicians, especially regarding surveillance for CAV and ideal imaging approaches for patients with VADs. The purpose of this review article is to provide an overview of different noninvasive imaging modalities used to evaluate patients after cardiac transplantation and for patients with VADs. The review focuses on the role of echocardiography, CT, and nuclear imaging in surveillance for CAV and rejection and on the assessment of ventricular structure and function, myocardial remodeling and complications for VAD patients.

Accuracy of intravascular ultrasound and optical coherence tomography in identifying functionally significant coronary stenosis according to vessel diameter: A meta-analysis of 2,581 patients and 2,807 lesions

INTRODUCTION

Accuracy of intracoronary imaging to discriminate functionally significant coronary stenosis according to vessel diameter remains to be defined.

METHODS

PubMed, Scopus, and Google Scholar were systematically searched for studies assessing diagnostic accuracy (area under the receiver operating characteristic curve [AUC], the primary end point) and sensitivity and specificity (the secondary end points) of minimal luminal area (MLA) or of minimal luminal diameter (MLD) derived from intravascular ultrasound (IVUS) or optical coherence tomography (OCT) to detect functionally significant stenosis as determined with fractional flow reserve (FFR).

RESULTS

Fifteen studies were included, 2 with 110 patients analyzing only left main (LM), 5 with 224 patients and 306 lesions using OCT, and 9 with 1532 patients and 1681 lesions with IVUS. Median MLA for the OCT studies was 1.96 mm(2) (1.85-1.98 mm(2)), 2.9 mm(2) (2.7-3.1 mm(2)) for MLA of all lesions assessed with IVUS, 2.8 mm(2) (2.7-2.9 mm(2)) for lesions with an angiographic diameter >3 mm, 2.4 mm(2) (2.4-2.5 mm(2)) for lesions <3 mm, and 5.4 mm(2) (5.1-5.6 mm(2)) for LM lesions. For OCT-MLA, AUC was 0.80 (0.74-0.86), with a sensitivity of 0.81 (0.74-0.87) and specificity of 0.77 (0.71-0.83), whereas OCT-MLD had an AUC of 0.85 (0.79-0.91), sensitivity of 0.74 (0.69-0.78), and specificity of 0.70 (0.68-0.73). For IVUS-MLA, AUC was 0.78 (0.75-0.81) for all lesions, 0.78 (0.73-0.84) for vessels with a diameter >3 mm, and 0.79 (0.70-0.89) for those with a diameter <3 mm. Left main AUC was 0.97 (0.93-1).

CONCLUSION

Intravascular ultrasound and OCT had modest diagnostic accuracy for identification hemodynamically significant lesions, also with specific cutoff for different diameters. Invasive imaging for assessment of LM severity demonstrated excellent correlation with FFR. What is already known about this subject? Fractional flow reserve represents the criterion standard to evaluate the prognostic value of coronary stenosis, whereas its relationship with IVUS and OCT remains to be assessed. What does this study add? Despite improvement, IVUS and OCT do not predict functional stenosis, even with dedicated cutoff, apart from LM disease. How might this impact on clinical practice? The recent guidelines of myocardial revascularization have stressed the crucial role of FFR before performing percutaneous coronary intervention on LM, whereas intravascular imaging is often exploited to drive revascularization. The present analysis stresses the point that LM percutaneous coronary intervention may be driven only by intravascular imaging, given the high accuracy for significant ischemic lesions, whereas for other vessels, these 2 techniques mirror 2 different aspects.

Coronary microvascular dysfunction correlates with the new onset of cardiac allograft vasculopathy in heart transplant patients with normal coronary angiography

Coronary microvascular dysfunction is emerging as a strong predictor of outcome in heart transplantation (HT). We assessed the validity of microvascular dysfunction, defined by means of a reduced coronary flow reserve (CFR), as a factor associated with new onset epicardial cardiac allograft vasculopathy (CAV) or death. We studied 105 patients at 4 ± 1 years post-HT with a normal coronary angiography (CA). New onset CAV was assessed by CA. CFR was assessed in the left anterior descending (LAD) coronary artery by transthoracic Doppler echocardiography and calculated as the ratio of hyperaemic to basal blood flow velocity. A CFR ≤ 2.5 was considered abnormal. Epicardial CAV onset or death was assessed during a follow-up of 10 years. New onset CAV was diagnosed in 30 patients (28.6%) (Group A), and the CA was normal in the remaining 75 patients (71.4%) (Group B). Group A had reduced CFR compared with group B (2.4 ± 0.6 vs. 3.2 ± 0.7, p < 0.0001). A CFR ≤ 2.5 was independently associated with a higher probability of new onset CAV (p < 0.0001) and a higher probability of death, regardless of CAV onset (p < 0.01). Microvascular dysfunction is independently associated with the onset of epicardial CAV, and associated with a higher risk of death, regardless of CAV onset.

Invasive evaluation of patients with angina in the absence of obstructive coronary artery disease

BACKGROUND

More than 20% of patients presenting to the cardiac catheterization laboratory with angina have no angiographic evidence of coronary artery disease. Despite a "normal" angiogram, these patients often have persistent symptoms, recurrent hospitalizations, a poor functional status, and adverse cardiovascular outcomes, without a clear diagnosis.

METHODS AND RESULTS

In 139 patients with angina in the absence of obstructive coronary artery disease (no diameter stenosis >50%), endothelial function was assessed; the index of microcirculatory resistance, coronary flow reserve, and fractional flow reserve were measured; and intravascular ultrasound was performed. There were no complications. The average age was 54.0±11.4 years, and 107 (77%) were women. All patients had at least some evidence of atherosclerosis based on an intravascular ultrasound examination of the left anterior descending artery. Endothelial dysfunction (a decrease in luminal diameter of >20% after intracoronary acetylcholine) was present in 61 patients (44%). Microvascular impairment (an index of microcirculatory resistance ≥25) was present in 29 patients (21%). Seven patients (5%) had a fractional flow reserve ≤0.80. A myocardial bridge was present in 70 patients (58%). Overall, only 32 patients (23%) had no coronary explanation for their angina, with normal endothelial function, normal coronary physiological assessment, and no myocardial bridging.

CONCLUSIONS

The majority of patients with angina in the absence of obstructive coronary artery disease have occult coronary abnormalities. A comprehensive invasive assessment of these patients at the time of coronary angiography can be performed safely and provides important diagnostic information that may affect treatment and outcomes.

Diagnosis and management of coronary allograft vasculopathy in children and adolescents

Coronary allograft vasculopathy remains one of the leading causes of death beyond the first year post transplant. As a result of denervation following transplantation, patients lack ischaemic symptoms and presentation is often late when the graft is already compromised. Current diagnostic tools are rather invasive, or in case of angiography, significantly lack sensitivity. Therefore a non-invasive tool that could allow early diagnosis would be invaluable.This paper review the disease form its different diagnosis techniques,including new and less invasive diagnostic tools to its pharmacological management and possible treatments.

Comparing the effect of clopidogrel versus ticagrelor on coronary microvascular dysfunction in acute coronary syndrome patients (TIME trial): study protocol for a randomized controlled trial

BACKGROUND

Although prompt reperfusion treatment restores normal epicardial flow, microvascular dysfunction may persist in some patients with acute coronary syndrome (ACS). Impaired myocardial perfusion is caused by intraluminal platelets, fibrin thrombi and neutrophil plugging; antiplatelet agents play a significant role in terms of protecting against thrombus microembolization. A novel antiplatelet agent, ticagrelor, is a non-thienopyridine, direct P2Y12 blocker that has shown greater, more rapid and more consistent platelet inhibition than clopidogrel. However, the effects of ticagrelor on the prevention of microvascular dysfunction are uncertain. The present study is a comparison between clopidogrel and ticagrelor use for preventing microvascular dysfunction in patients with ST elevation or non-ST elevation myocardial infarction (STEMI or NSTEMI, respectively).

METHODS/DESIGN

The TIME trial is a single-center, randomized, open-label, parallel-arm study designed to demonstrate the superiority of ticagrelor over clopidogrel. A total of 152 patients with a spectrum of STEMI or NSTEMI will undergo prospective random assignment to clopidogrel or ticagrelor (1:1 ratio). The primary endpoint is an index of microcirculatory resistance (IMR) measured after percutaneous coronary intervention (PCI); the secondary endpoint is wall motion score index assessed at 3 months by using echocardiography.

DISCUSSION

The TIME trial is the first study designed to compare the protective effect of clopidogrel and ticagrelor on coronary microvascular dysfunction in patients with STEMI and NSTEMI.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02026219. Registration date: 24 December 2013.

Multiparametric cardiovascular magnetic resonance assessment of cardiac allograft vasculopathy

OBJECTIVES

This study sought to evaluate the diagnostic performance of multiparametric cardiovascular magnetic resonance (CMR) for detecting cardiac allograft vasculopathy (CAV) using contemporary invasive epicardial artery and microvascular assessment techniques as reference standards, and to compare the performance of CMR with that of angiography.

BACKGROUND

CAV continues to limit the long-term survival of heart transplant recipients. Coronary angiography has a Class I recommendation for CAV surveillance and annual or biannual surveillance angiography is performed routinely in most centers.

METHODS

All transplant recipients referred for surveillance angiography at a single UK center over a 2-year period were prospectively screened for study eligibility. Patients prospectively underwent coronary angiography followed by coronary intravascular ultrasound, fractional flow reserve, and index of microcirculatory resistance. Within 1 month, patients underwent multiparametric CMR, including assessment of regional and global ventricular function, absolute myocardial blood flow quantification, and myocardial tissue characterization. In addition, 10 healthy volunteers underwent CMR.

RESULTS

Forty-eight patients were recruited, median 7.1 years (interquartile range: 4.6 to 10.3 years) since transplantation. The CMR myocardial perfusion reserve was the only independent predictor of both epicardial (β = -0.57, p < 0.001) and microvascular disease (β = -0.60, p < 0.001) on stepwise multivariable regression. The CMR myocardial perfusion reserve significantly outperformed angiography for detecting moderate CAV (area under the curve, 0.89 [95% confidence interval (CI): 0.79 to 1.00] vs. 0.59 [95% CI: 0.42 to 0.77], p = 0.01) and severe CAV (area under the curve, 0.88 [95% CI: 0.78 to 0.98] vs. 0.67 [95% CI: 0.52 to 0.82], p = 0.05).

CONCLUSIONS

CAV, including epicardial and microvascular components, can be detected more accurately using noninvasive CMR-based absolute myocardial blood flow assessment than with invasive coronary angiography, the current clinical surveillance technique.

Disturbed coronary hemodynamics in vessels with intermediate stenoses evaluated with fractional flow reserve: a combined analysis of epicardial and microcirculatory involvement in ischemic heart disease

BACKGROUND

In chronic ischemic heart disease, focal stenosis, diffuse atherosclerotic narrowings, and microcirculatory dysfunction (MCD) contribute to limit myocardial flow. The prevalence of these ischemic heart disease levels in fractional flow reserve (FFR) interrogated vessels remains largely unknown.

METHODS AND RESULTS

Using intracoronary measurements, 91 coronaries (78 patients) with intermediate stenoses were classified in 4 FFR and coronary flow reserve (CFR) agreement groups, using FFR>0.80 and CFR<2 as cutoffs. Index of microcirculatory resistance (IMR) and atherosclerotic burden (Gensini score) were also assessed. MCD was assumed when IMR≥29.1 (75(th) percentile). Fifty-four (59.3%) vessels had normal FFR, from which only 20 (37%) presented both normal CFR and IMR. Among vessels with FFR>0.80, most (63%) presented disturbed hemodynamics: abnormal CFR in 28 (52%) and MCD in 18 (33%). Vessels with FFR>0.80 presented higher IMR [adjusted mean 27.6 (95% confidence interval, 23.4-31.8)] than those with FFR≤0.80 [17.3 (95% confidence interval, 13.0-21.7), p=0.001]. Atherosclerotic burden was inversely correlated with CFR (r=-0.207, P=0.055), and in vessels with FFR>0.80 and CFR<2 (n=28, 39%), IMR had a wide dispersion (7-72.7 U), suggesting a combination of diffuse atherosclerotic narrowings and MCD. Vessels with FFR≤0.80 and normal CFR presented the lowest IMR, suggesting a preserved microcirculation.

CONCLUSIONS

A substantial number of coronary arteries with stenoses showing an FFR>0.80 present disturbed hemodynamics. Integration of FFR, CFR, and IMR supports the existence of differentiated patterns of ischemic heart disease that combine focal and diffuse coronary narrowings with variable degrees of MCD.

[Diagnosis, prevention and treatment of cardiac allograft vasculopathy]

The major limitation of long-term survival after cardiac transplantation is allograft vasculopathy, which consists of concentric and diffuse intimal hyperplasia. The disease still has a significant incidence, estimated at 30% five years after cardiac transplantation. It is a clinically silent disease and so diagnosis is a challenge. Coronary angiography supplemented by intravascular ultrasound is the most sensitive diagnostic method. However, new non-invasive diagnostic techniques are likely to be clinically relevant in the future. The earliest possible diagnosis is essential to prevent progression of the disease and to improve its prognosis. A new nomenclature for allograft vasculopathy has been published in July 2010, developed by the International Society for Heart and Lung Transplantation (ISHLT), establishing a standardized definition. Simultaneously, the ISHLT published new guidelines standardizing the diagnosis and management of cardiac transplant patients. This paper reviews contemporary concepts in the pathophysiology, diagnosis, prevention and treatment of allograft vasculopathy, highlighting areas that are the subject of ongoing research.