Prevalence of different gadolinium enhancement patterns in patients after heart transplantation

Cardiac magnetic resonance imaging in heart transplant recipients with biopsy-negative graft dysfunction

AIMS

Graft dysfunction (GD) after heart transplantation (HTx) can develop without evidence of cell- or antibody-mediated rejection. Cardiac magnetic resonance imaging (CMR) has an evolving role in detecting rejection; however, its role in biopsy-negative GD has not been described. This study examines CMR findings, evaluates outcomes based on CMR results, and seeks to identify the possibility of rejection missed through endomyocardial biopsy by using CMR in HTx recipients with biopsy-negative GD.

METHODS AND RESULTS

HTx recipients with GD [defined as a decrease in left ventricular ejection fraction (LVEF) by >5% and LVEF < 50%] in the absence of rejection by biopsy or allograft vasculopathy and who underwent CMR were included in the study. The primary outcome was a composite of all-cause mortality, re-transplantation, or persistent LVEF < 50%. Overall, 34 HTx recipients developed biopsy-negative GD and underwent CMR. Left ventricular late gadolinium enhancement (LGE) on CMR was observed in 16 patients with two distinct patterns: diffuse epicardial (n = 13) and patchy (n = 3) patterns. Patients with LGE developed GD later after HTx [4 (1.4-6.8) vs. 0.8 (0.3-1.2) years, P < 0.001], were more often symptomatic (88% vs. 56%, P = 0.06), and had greater haemodynamic derangement (pulmonary capillary wedge pressure: 19 ± 7 vs. 13 ± 3 mmHg, P = 0.002) as compared with those without LGE. No significant difference was observed in the primary composite outcome between patients with LGE and those without LGE (50% vs. 38% of patients with events, P = 0.515). During a median follow-up of 3.8 years, mean LVEF improved similarly in the LGE-negative (37-55%) and LGE-positive groups (32-55%) (P = 0.16).

CONCLUSIONS

Biopsy-negative GD occurs with and without LGE when assessed by CMR, indicative of possible rejection/inflammation occurring only in a subset of patients. Irrespective of LGE, LVEF improvement occurs in most GD patients, suggesting that other neurohormonal or immunomodulatory mechanisms may also contribute to GD development.

Late-gadolinium enhancement is common in older pediatric heart transplant recipients and is associated with lower ejection fraction

BACKGROUND

Chronic graft failure and cumulative rejection history in pediatric heart transplant recipients (PHTR) are associated with myocardial fibrosis on endomyocardial biopsy (EMB). Cardiovascular magnetic resonance imaging (CMR) is a validated, non-invasive method to detect myocardial fibrosis via the presence of late gadolinium enhancement (LGE). In adult heart transplant recipients, LGE is associated with increased risk of future adverse clinical events including hospitalization and death. We describe the prevalence, pattern, and extent of LGE on CMR in a cohort of PHTR and its associations with recipient and graft characteristics.

METHODS

This was a retrospective study of consecutive PHTR who underwent CMR over a 6-year period at a single center. Two independent reviewers assessed the presence and distribution of left ventricular (LV) LGE using the American Heart Association (AHA) 17-segment model. LGE quantification was performed on studies with visible fibrosis (LGE+). Patient demographics, clinical history, and CMR-derived volumetry and ejection fractions were obtained.

RESULTS

Eighty-one CMR studies were performed on 59 unique PHTR. Mean age at CMR was 14.8 ± 6.2 years; mean time since transplant was 7.3 ± 5.0 years. The CMR indication was routine surveillance (without a clinical concern based on laboratory parameters, echocardiography, or cardiac catheterization) in 63% (51/81) of studies. LGE was present in 36% (29/81) of PHTR. In these LGE + studies, patterns included inferoseptal in 76% of LGE + studies (22/29), lateral wall in 41% (12/29), and diffuse, involving > 4 AHA segments, in 21% (6/29). The mean LV LGE burden as a percentage of myocardial mass was 18.0 ± 9.0%. When reviewing only the initial CMR per PHTR (n = 59), LGE + patients were older (16.7 ± 2.9 vs. 12.8 ± 4.6 years, p = 0.001), with greater time since transplant (8.3 ± 5.4 vs. 5.7 ± 3.9 years, p = 0.041). These patients demonstrated higher LV end-systolic volume index (LVESVI) (34.7 ± 11.7 vs. 28.7 ± 6.1 ml/m2, p = 0.011) and decreased LV ejection fraction (LVEF) (56.2 ± 8.1 vs. 60.6 ± 5.3%, p = 0.015). There were no significant differences in history of moderate/severe rejection (p = 0.196) or cardiac allograft vasculopathy (CAV) (p = 0.709).

CONCLUSIONS

LV LGE was present in approximately one third of PHTR, more commonly in older patients with longer time since transplantation. Grafts with LGE have lower LVEF. CMR-derived LGE may aid in surveillance of chronic graft failure in PHTR.

Heart Transplantation: Indications, Surgical Techniques, and Complications

Heart transplantation has been increasingly performed for patients with end-stage heart failure most commonly related to ischemic and non-ischemic cardiomyopathies. The major complications are procedure-related complications, infection, acute rejection, cardiac allograft vasculopathy, and malignancy. Radiologists have an important role in the evaluation of transplant candidates and early detection of postoperative complications.

Case report: Coronary allograft vasculopathy: an accurate reflection of the histopathological findings on cardiovascular magnetic resonance imaging

Heart transplant recipients undergo extensive invasive and non-invasive postoperative screening to exclude complications, such as allograft rejection and vasculopathy. Cardiac magnetic resonance imaging is a non-invasive, non-irradiating, diagnostic tool for monitoring graft health and identifying possible tissue rejection or myocardial fibrosis. We describe the case of a 29-year-old female heart transplant recipient admitted to our care center with a worsening clinical condition. The patient underwent clinical evaluation, blood tests, including troponin I and N-terminal pro brain type natriuretic peptide, transthoracic echocardiography, invasive coronary angiography, and cardiovascular magnetic resonance imaging. Cardiovascular magnetic resonance imaging showed widespread sub-epicardial hyperintensity of the myocardial segments along the course of the coronary arteries. T2 mapping sequences showed an elevated value and the myocardial native T1 values and extracellular volume percentage were significantly increased. Late gadolinium enhancement demonstrated a diffuse sub-epicardial hypersignal along the lateral, free, and left ventricular walls. All the sequences evidenced widespread hyper-enhancement of epicardial fat along the course of the thickened main coronary artery walls. One month later, the recipient underwent re-transplantation due to progressive worsening of the clinical condition and refractoriness to intravenous medication. The anatomopathological findings of the explanted heart provided impressive visualization of structural and histopathological changes. These results could guide the tailoring of preventive therapeutic strategies and non-invasive monitoring of cardiac grafts.

The association with organ procurement techniques and early cardiac transplant outcomes using cardiac MRI

BACKGROUND

Heart transplantation (HT) has historically been limited by organ availability. Use of donation after circulatory death (DCD) donors addresses this limitation by utilizing previously unused hearts through use of the Organ Care System (OCS).

OBJECTIVES

This study aimed to determine the impact of procurement and transportation method on allograft structure and function using early post-transplant cardiac magnetic resonance imaging (MRI).

METHODS

Patients who underwent HT at our institution from February 1, 2020, through April 30, 2021 who underwent cardiac MRI imaging <60 days from transplant were included. Recipient and donor characteristics, clinical outcomes, and MRI findings were compared between those who underwent DCD transplantation using the OCS device (DCD-OCS), brain dead donation (DBD) using the OCS device (DBD-OCS), and DBD transported via cold storage (DBD-cold storage) using one-way analysis of variance.

RESULTS

A total of 85 patients underwent HT with a cardiac MRI during the study period. Thirty-one (36%) patients received a DCD organ, 16 (19%) received a DBD-OCS organ and 38 (45%) received a DBD-cold storage organ. Rates of primary graft dysfunction (PGD) were significantly higher in DCD transplants (19.5% DCD vs. .0% DBD-OCS and 5.3% DBD-cold storage; p < .050 across three groups), but with no differences in mortality or rejection. There were no differences in cardiac MRI findings between the three transplant types, including presence of gadolinium hyperenhancement after transplant (all p > .050).

CONCLUSIONS

We observed no differences in early cardiac MRI findings between patients that received DCD and DBD-OCS heart transplants compared with those receiving DBD-cold storage transplants.

Evaluation of cardiac allograft vasculopathy by positron emission tomography

Cardiac allograft vasculopathy (CAV) remains one of the most important late occurring complications in heart transplant (HT) recipients significantly effecting graft survival. Recently, there has been tremendous focus on the development of effective and safe non-invasive diagnostic strategies for the diagnosis of CAV employing a wide range of imaging technologies. During the past decade multiple studies have been published using positron emission tomography (PET) myocardial perfusion imaging, establishing the value of PET myocardial blood flow quantification for the evaluation of CAV. These independent investigations demonstrate that PET can be successfully used to establish the diagnosis of CAV, can be utilized for prognostication and may be used for serial monitoring of HT recipients. In addition, molecular imaging techniques have started to emerge as new tools to enhance our knowledge to better understand the pathophysiology of CAV.

Cardiac magnetic resonance imaging myocardial perfusion reserve index in heart transplant patients

OBJECTIVE

To compare the myocardial perfusion reserve index (MPRI) measured during stress cardiac magnetic resonance imaging (MRI) with regadenoson in patients with heart transplants versus in patients without heart transplants.

MATERIAL AND METHODS

We retrospectively compared 20 consecutive asymptomatic heart transplant patients without suspicion of microvascular disease who underwent stress cardiac MRI with regadenoson and coronary computed tomography angiography (CTA) to rule out cardiac allograft vasculopathy versus 16 patients without transplants who underwent clinically indicated stress cardiac MRI who were negative for ischemia and had no signs of structural heart disease. We estimated MPRI semiquantitatively after calculating the up-slope of the first-pass enhancement curve and dividing the value obtained during stress by the value obtained at rest. We compared MPRI in the two groups. Patients with positive findings for ischemia on stress cardiac MRI or significant coronary stenosis on coronary CTA were referred for conventional coronary angiography.

RESULTS

More than half the patients remained asymptomatic during the stress test. Stress cardiac MRI was positive for ischemia in two heart transplant patients; these findings were confirmed at coronary CTA and at conventional coronary angiography. Patients with transplants had lower end-diastolic volume index (59.3±15.2 ml/m² vs. 71.4±15.9 ml/m² in those without transplants, p=0.03), lower MPRI (1.35±0.19 vs. 1.6±0.28 in those without transplants, p=0.003), and a less pronounced hemodynamic response to regadenoson (mean increase in heart rate 13.1±5.4 bpm vs. 28.5±8.9 bpm in those without transplants, p <0.001).

CONCLUSION

Stress cardiac MRI with regadenoson is safe. In the absence of epicardial coronary artery disease, patients with heart transplants have lower MPRI than patients without transplants, suggesting microvascular disease. The hemodynamic response to regadenoson is less pronounced in patients with heart transplants than in patients without heart transplants.

Myocardial Fibrosis and Prognosis in Heart Transplant Recipients

BACKGROUND

Myocardial fibrosis is a well-described histopathologic feature in heart transplant recipients. Whether myocardial fibrosis in heart transplant recipients is independently associated with clinical outcomes is unclear. We sought to determine whether myocardial fibrosis on late gadolinium enhancement cardiovascular magnetic resonance imaging in heart transplant recipients was independently associated with all-cause death or major adverse cardiac outcomes in the long-term.

METHODS

Using a cohort of consecutive heart transplant recipients that had cardiovascular magnetic resonance imaging, we determined the prevalence and the patterns of myocardial fibrosis and analyzed associations between myocardial fibrosis and a composite end point of all-cause death or major adverse cardiac events: retransplantation, nonfatal myocardial infarction, coronary revascularization, and heart failure hospitalization.

RESULTS

One hundred and fifty-two heart transplant recipients (age, 54±15 years; 29% women; 5.0±5.4 years after heart transplantation) were included. Myocardial fibrosis was present in 18% (37% infarct pattern, 41% noninfarct pattern, and 22% both). Its prevalence was positively associated with cardiac allograft vasculopathy grade. With a median follow-up of 2.6 years, myocardial fibrosis was independently associated with all-cause death or major adverse cardiac events (hazard ratio, 2.88; 95% CI, 1.59-5.23; P<0.001) after adjustment for cardiac allograft vasculopathy, history of rejection, time since transplantation, left ventricular ejection fraction, and indexed right ventricular end-diastolic volume. Every 1% increase in myocardial fibrosis was independently associated with a 6% higher hazard for all-cause death or major adverse cardiac events (hazard ratio, 1.06; 95% CI, 1.03-1.09; P<0.001). The addition of myocardial fibrosis variables to models with cardiac allograft vasculopathy, history of rejection, time since transplantation, left ventricular ejection fraction, and indexed right ventricular end-diastolic volume resulted in significant improvements in model fit, suggesting incremental prognostic value.

CONCLUSIONS

In heart transplant recipients, myocardial fibrosis is seen on late gadolinium enhancement cardiovascular magnetic resonance imaging in 18%. Both the presence and the extent of myocardial fibrosis are independently associated with the long-term risk of all-cause death or major adverse cardiac events.

The Role of Contrast-Enhanced Cardiac Magnetic Resonance in the Assessment of Patients with Malignant Ventricular Arrhythmias

Cardiac magnetic resonance (CMR) imaging has gained significant traction as an imaging modality of choice in the evaluation of individuals with, or at risk for, heart failure. Ventricular arrhythmias, often malignant, may be sequelae of heart failure and arise from fibrosis. Late gadolinium enhancement evaluation by CMR has become a preferred modality to assess individuals at risk for malignant ventricular arrhythmias. A spectrum of various pathologies that predispose individuals to malignant ventricular arrhythmias, as well as the usefulness of CMR in their identification and prognostication, are reviewed.

Strain-encoded magnetic resonance: a method for the assessment of myocardial deformation

This study aims to assess the usefulness of strain‐encoded magnetic resonance (SENC) for the quantification of myocardial deformation (‘strain’) in healthy volunteers and for the diagnostic workup of patients with different cardiovascular pathologies. SENC was initially described in the year 2001. Since then, the SENC sequence has undergone several technical developments, aiming at the detection of strain during single‐heartbeat acquisitions (fast‐SENC). Experimental and clinical studies that used SENC and fast‐SENC or compared SENC with conventional cine or tagged magnetic resonance in phantoms, animals, healthy volunteers, or patients were systematically searched for in PubMed. Using ‘strain‐encoded magnetic resonance and SENC’ as keywords, three phantom and three animal studies were identified, along with 27 further clinical studies, involving 185 healthy subjects and 904 patients. SENC (i) enabled reproducible assessment of myocardial deformation in vitro, in animals and in healthy volunteers, (ii) showed high reproducibility and substantially lower time spent compared with conventional tagging, (iii) exhibited incremental value to standard cine imaging for the detection of inducible ischaemia and for the risk stratification of patients with ischaemic heart disease, and (iv) enabled the diagnostic classification of patients with transplant vasculopathy, cardiomyopathies, pulmonary hypertension, and diabetic heart disease. SENC has the potential to detect a wide range of myocardial diseases early, accurately, and without the need of contrast agent injection, possibly enabling the initiation of specific cardiac therapies during earlier disease stages. Its one‐heartbeat acquisition mode during free breathing results in shorter cardiovascular magnetic resonance protocols, making its implementation in the clinical realm promising.

Noninvasive monitoring of acute and chronic rejection in heart transplantation

PURPOSE OF REVIEW

Recent years have seen advances in the early detection of cardiac graft rejection.

RECENT FINDINGS

We review the possibilities offered by tissue Doppler imaging and speckle tracking echocardiography, cardiac magnetic resonance, cardiac computed tomography, single positron emission tomography, gene expression profiling, and quantitation of donor-derived cell-free DNA, and microRNAs.

SUMMARY

Noninvasive monitoring of acute and chronic rejection after cardiac transplantation is an unmet need and remains a challenge. Imaging techniques and peripheral blood biomarkers are the most commonly used approaches, and in recent years there has been great progress. Gene expression profiling seems to be useful for ruling out the presence of a moderate to severe acute cellular rejection in stable, low-risk patients. Newer monitoring tools, like donor-derived cell-free DNA or microRNA, seem to be promising for individualizing immunosuppressive therapies and better understanding the mechanisms of rejection.

Emerging imaging techniques after cardiac transplantation

Improvements in survival after cardiac transplantation have in part been driven by improved graft surveillance. Graft surveillance relies mainly on 3 techniques: coronary angiography, endomyocardial biopsy and echocardiography. Developments in invasive and non-invasive imaging technology have revolutionized assessment of the heart in both health and disease, offering new insights into tissue composition and myocardial metabolism. Herein we aim to review the strengths and weaknesses of these techniques, and summarize the evidence in the following 5 fields of cardiac imaging after transplantation: cardiovascular magnetic resonance; computed tomography; positron emission tomography; single-photon emission computed tomography; and optical coherence tomography and molecular imaging techniques.

Transplant allograft vasculopathy: Role of multimodality imaging in surveillance and diagnosis

Cardiac allograft vasculopathy (CAV) is a challenging long-term complication of cardiac transplantation and remains a leading long-term cause of graft failure, re-transplantation, and death. CAV is an inflammatory vasculopathy distinct from traditional atherosclerotic coronary artery disease. Historically, the surveillance and diagnosis of CAV has been dependent on serial invasive coronary angiography with intravascular imaging. Although commonly practiced, angiography is not without significant limitations. Technological advances have provided sophisticated imaging techniques for CAV assessment. It is now possible to assess the vascular lumen, vessel wall characteristics, absolute blood flow, perfusion reserve, myocardial contractile function, and myocardial metabolism and injury in a noninvasive, expeditious manner with little risk. The current article will review key imaging modalities for the surveillance, diagnosis, and prognosis of CAV and discuss coronary physiology of transplanted hearts with emphasis on the clinical implications for provocative and vasodilator stress testing.

Diagnostic performance of late gadolinium enhancement in the assessment of acute cellular rejection after heart transplantation

OBJECTIVE

Allograft rejection is still an important cause of morbidity and mortality after heart transplantation (HTx). Many techniques in cardiac magnetic resonance imaging (CMR) were investigated to diagnose acute cellular rejection (ACR). However, there is not enough information about late gadolinium enhancement (LGE) in the myocardium and ACR.

METHODS

We prospectively analyzed our consecutive 41 heart transplant recipients who were admitted for routine endomyocardial biopsies. CMR was performed maximum 6 h before the scheduled endomyocardial biopsy. Correlation between LGE in the myocardium and ACR was investigated.

RESULTS

Twenty-seven patients showed no rejection, and nine of them had LGE in the myocardium. Fourteen patients had LGE in the left ventricle (LV), and two patients had LGE also in the right ventricle (RV). There was no correlation between LGE and ACR (p=0.879). There was no difference in the left ventricular ejection fraction (LVEF), right ventricular fractional area change (RVFAC), and cardiac ischemic time between the groups (p=0.825, p=0.370, and p=0.419, respectively). LGE in the myocardium could be due to previous rejection episodes; therefore, all patients were retrospectively searched for previous rejection grades and number of episodes. Thirty-eight of the 41 patients had a history of one ACR episode, but none of them had a statistically significant correlation with LGE (for grade 1R, p=0.964 and grade 3R, p=1) There was also no correlation between number of rejection episodes history and LGE.

CONCLUSION

LGE is not suitable to detect ACR in heart transplant patients. LGE and the history of ACR have no correlation.

Biomarkers of acute rejection following cardiac transplantation

Cardiac transplantation can be a life-saving treatment for selected patients with heart failure. However, despite advances in immunosuppressive therapy, acute allograft rejection remains a significant cause of morbidity and mortality. The current 'gold standard' for rejection surveillance is endomyocardial biopsy, which aims to identify episodes of rejection prior to development of clinical manifestations. This is an invasive technique with a risk of false-positive and false-negative results. Consequently, a wide variety of noninvasive alternatives have been investigated for their potential role as biomarkers of rejection. This article reviews the evidence behind proposed alternatives such as imaging techniques, electrophysiological parameters and peripheral blood markers, and highlights the potential future role for biomarkers in cardiac transplantation as an adjunct to biopsy.

The Value of Cardiovascular Magnetic Resonance in Heart Transplant Patients

Heart transplant patients present a unique set of anatomical and pathophysiological considerations. Patients often present non-specifically, requiring a low index for further investigation. Accurate assessment with standard imaging modalities can be difficult, and cardiovascular magnetic resonance (CMR) is becoming an increasingly useful modality in the assessment of heart transplant patients. This review describes the anatomy of the transplanted heart and typical CMR appearances and discusses the role of CMR in heart transplant disease.

Correlation of cardiovascular magnetic resonance imaging findings and endomyocardial biopsy results in patients undergoing screening for heart transplant rejection

BACKGROUND

Endomyocardial biopsy (EMB) is the current gold standard to screen for heart transplant rejection but has important risks and limitations. Cardiovascular magnetic resonance imaging (CMRI) is increasingly used to characterize cardiac function and myocardial tissue. We evaluated the diagnostic accuracy of CMRI compared with EMB and clinically diagnosed heart transplant rejection.

METHODS

Comprehensive CMRI scans were performed on adult heart transplant recipients within 24 hours of EMB (routine or clinically indicated), before initiation of any anti-rejection therapy, and blinded to EMB results. Multivariable analysis was used to create CMRI diagnostic criteria for comparison with a positive EMB (Grade ≥ 2R or antibody-mediated rejection) and clinical rejection (change in medical therapy to treat rejection).

RESULTS

Sixty participants (75% male; mean age, 51 ± 14 years) were recruited, providing 73 comparisons between CMRI and EMB for the diagnosis of rejection. Multivariable logistic regression identified myocardial edema (T2 relaxation time) and right ventricular end-diastolic volume index as independent predictors of a positive EMB. Combining threshold right ventricular end-diastolic volume index and edema values predicted a positive EMB with very good accuracy: sensitivity, 93%; specificity, 78%; positive predictive value, 52%; and negative predictive valve, 98%. CMRI was more sensitive than EMB at predicting clinical rejection (sensitivity of 67% vs 58%).

CONCLUSIONS

CMRI has high sensitivity and high negative predictive value in predicting biopsy-positive heart transplant rejection and may be useful as a screening test before routine EMB. CMRI also has better sensitivity for clinically diagnosed heart transplant rejection and could be helpful in cases of negative rejection on the biopsy specimen.

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.

Comprehensive bio-imaging using myocardial perfusion reserve index during cardiac magnetic resonance imaging and high-sensitive troponin T for the prediction of outcomes in heart transplant recipients

We sought to determine the ability of quantitative myocardial perfusion reserve index (MPRI) by cardiac magnetic resonance (CMR) and high-sensitive troponin T (hsTnT) for the prediction of cardiac allograft vasculopathy (CAV) and cardiac outcomes in heart transplant (HT) recipients. In 108 consecutive HT recipients (organ age 4.1±4.7 years, 25 [23%] with diabetes mellitus) who underwent cardiac catheterization, CAV grade by International Society for Heart & Lung Transplantation (ISHLT) criteria, MPRI, late gadolinium enhancement (LGE) and hsTnT values were obtained. Outcome data including cardiac death and urgent revascularization ("hard cardiac events") and revascularization procedures were prospectively collected. During a follow-up duration of 4.2±1.4 years, seven patients experienced hard cardiac events and 11 patients underwent elective revascularization procedures. By multivariable analysis, hsTnT and MPRI both independently predicted cardiac events, surpassing the value of LGE and CAV by ISHLT criteria. Furthermore, hsTnT and MPRI provided complementary value. Thus, patients with high hsTnT and low MPRI showed the highest rates of cardiac events (annual event rate=14.5%), while those with low hsTnT and high MPRI exhibited excellent outcomes (annual event rate=0%). In conclusion, comprehensive "bio-imaging" using hsTnT, as a marker of myocardial microinjury, and CMR, as a marker of microvascular integrity and myocardial damage by LGE, may aid personalized risk-stratification in HT recipients.

Prevalence of different forms of infarct-atypical late gadolinium enhancement in patients early and late after heart transplantation

BACKGROUND

Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) enables high-resolution myocardial tissue characterization, showing the results of different injuries, especially in the early period after heart transplantation (HTX).

OBJECTIVES

We sought to apply LGE-CMR to investigate the prevalence and patterns of infarct-atypical myocardial involvement and associated mechanisms in patients early and late after HTX.

METHODS

LGE-CMR was performed on a 1.5-T MRI scanner (Philips, Best, the Netherlands) in 89 patients: group 1 (48 patients) less than 2.5 years after operation (1.2 ± 0.5 years) and group 2 (41 patients) later this period (8.2 ± 4.2 years). Following LGE-CMR, the presence, distribution, patterns of infarct-atypical LGE and possible associated mechanisms were assessed.

RESULTS

71 % of group 1 patients (34/48) showed infarctatypical LGE whereas 57 % of group 2 patients (22/41) were affected (p = 0.25). Fewer segments/patients were involved later after HTX (1.6 ± 2.0 vs. 2.9 ± 3.1 segments/ patient; p = 0.03), but only diffuse LGE-CMR pattern decreased significantly (11.5 % of affected segments in group 1 vs. 6.5 % in group 2; p\0.001). Group 2 had lower ischemic time (181 ± 53 vs. 208 ± 61 min; p = 0.03), the donors were younger (33 ± 13 vs. 41 ± 13 years; p = 0.01) and fewer donors were Toxoplasma gondii seropositive (4 vs. 22pts; p\0.001).

CONCLUSION

Infarct-atypical LGE was found in a significant number of patients early post-HTX, however, fewer patients and myocardial segments per patient were affected later after HTX. Many potential factors seem to be involved, but the exact mechanisms are still unclear. Future studies are necessary to test prognostic implications associated with LGE-CMR patterns.

Cardiovascular MRI predicts 5-year adverse clinical outcome in heart transplant recipients

Imaging recommendations for the follow-up of heart transplant recipients (HTRs) lack evidence justifying their prognostic value. Cardiovascular magnetic resonance imaging (CMRI) can characterize heart structure and function and has prognostic value in many myocardial diseases. We hypothesized that CMRI evaluation of cardiac allografts would predict adverse events. We performed CMRI on 60 HTRs evaluating biventricular size, function and myocardial scar. We performed survival analysis to identify independent predictors of cardiovascular (CV) death or hospitalization. Participants had a mean age of 51 ± 14 years, mean graft age of 3.5 years (±4) and 75% are male. Median follow-up time was 4.9 years with 22 CV hospitalizations and 7 CV deaths. A multivariable survival analysis of imaging and clinical variables identified myocardial scar (hazard ratio [HR] of 10.7, p = 0.005), right ventricular end- diastolic volume index (RVEDVI; 1.1/mL/m(2) , p = 0.001), graft age (HR = 1.2/year, p = 0.004) and previous allograft rejection (HR = 4.4, p = 0.006) as predictive of time to CV death or hospitalization. CMRI-derived myocardial scar and RVEDVI are independently associated with CV outcomes in HTRs.

Assessment of sub-clinical acute cellular rejection after heart transplantation: comparison of cardiac magnetic resonance imaging and endomyocardial biopsy

OBJECTIVE

Comparing the diagnostic value of multi-sequential cardiac magnetic resonance imaging (CMR) with endomyocardial biopsy (EMB) for sub-clinical cardiac allograft rejection.

METHODS

One hundred and forty-six examinations in 73 patients (mean age 53 ± 12 years, 58 men) were performed using a 1.5 Tesla system and compared to EMB. Examinations included a STIR (short tau inversion recovery) sequence for calculation of edema ratio (ER), a T1-weighted spin-echo sequence for assessment of global relative enhancement (gRE), and inversion-recovery sequences to visualize late gadolinium enhancement (LGE). Histological grade ≥1B was considered relevant rejection.

RESULTS

One hundred and twenty-seven (127/146 = 87 %) EMBs demonstrated no or mild signs of rejection (grades ≤1A) and 19/146 (13 %) a relevant rejection (grade ≥1B). Sensitivity, specificity, positive predictive, and negative predictive values were as follows: ER: 63 %, 78 %, 30 %, and 93 %; gRE: 63 %, 70 %, 24 %, and 93 %; LGE: 68 %, 36 %, 13 %, and 87 %; with the combination of ER and gRE with at least one out of two positive: 84 %, 57 %, 23 %, and 96 %. ROC analysis revealed an area under the curve of 0.724 for ER and 0.659 for gRE.

CONCLUSION

CMR parameters for myocarditis are useful to detect sub-clinical acute cellular rejection after heart transplantation. Comparable results to myocarditis can be achieved with a combination of parameters.

KEY POINTS

• Magnetic resonance imaging is useful for the assessment of cardiac allograft rejection. • CMR has a high negative predictive value for exclusion of allograft rejection. • Diagnostic performance is not yet good enough to replace endomyocardial biopsy.

Evolving concepts and treatment strategies for cardiac allograft vasculopathy

OPINION STATEMENT

The central event in the development of allograft vasculopathy is the inflammatory response to immune-mediated and nonimmune-mediated endothelial damage. This response is characterized by the release of inflammatory cytokines, upregulation of cell-surface adhesion molecules, and subsequent binding of leukocytes. Growth factors stimulate smooth muscle cell proliferation and circulating progenitor cells are recruited to sites of arterial injury leading to neointima formation. Because of its diffuse nature, intravascular ultrasound is more sensitive than angiography for early diagnosis. Proliferation signal inhibitors (PSIs) have the capacity to slow vasculopathy progression by inhibiting smooth muscle cell proliferation, but its side effects profile makes its use as a first line agent difficult. Retransplantation is still the only definitive therapy but is available only in selected cases. The current hope is that immunomodulation at the time of transplant could induce long-term tolerance and graft accommodation, leading to less vasculopathy.

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.

Long-term outcome after heart transplantation predicted by quantitative myocardial blush grade in coronary angiography

The purpose of our study was to investigate whether the quantification of myocardial blush grade (MBG) during surveillance coronary angiography can predict long-term outcome after heart transplantation (HT). In 105 HT recipients who underwent cardiac catheterization, cardiac allograft vasculopathy (CAV) was assessed visually using the ISHLT grading scale (prospective cohort study). MBG was quantified by dividing the plateau of contrast agent gray-level intensity (G(max)) by the time-to-peak intensity (T(max)). In a subgroup (n = 72), myocardial perfusion index by cardiac magnetic resonance imaging (CMR) was assessed. During a mean follow-up duration of 2.7 (standard deviation [SD] 1.0) years, 26 patients experienced cardiac events, including 7 with cardiac death and 19 who underwent coronary revascularization. G(max)/T(max) was related to CAV by ISHLT criteria and to subsequent cardiac events. By univariate analysis, patient age, organ age, CAV, MBG and myocardial perfusion index by CMR were all predictive for cardiac events. Multivariable analysis demonstrated that G(max)/T(max) provided the most robust prediction of cardiac death (hazard ratio [HR] = 0.2, 95% confidence interval [CI] = 0.06-0.64, p < 0.01) and cardiac events (HR = 0.52, 95% CI = 0.32-0.84, p < 0.01), beyond clinical parameters and the presence of CAV. G(max)/T(max) is a valuable surrogate parameter of microvascular integrity, which is associated with cardiac death and revascularization procedures after HT.

Detection and grading of coronary allograft vasculopathy in children with contrast-enhanced magnetic resonance imaging of the coronary vessel wall

BACKGROUND

Coronary allograft vasculopathy is the leading cause of late death after heart transplantation in children. It is poorly detected by conventional angiography. Intravascular ultrasound is invasive and costly. This study shows that magnetic resonance imaging (MRI) late gadolinium enhancement (LGE) of the coronary vessel wall can detect and grade coronary allograft vasculopathy.

METHODS AND RESULTS

Twenty-four children (10 male; age range, 9-17 years) underwent coronary angiography, intravascular ultrasound, and MRI. Maximal intimal thickness and mean intimal index were recorded. MRI included coronary magnetic resonance angiogram and LGE vessel wall imaging with 1.5 T (n=12) and 3.0 T (n=12). Ten healthy control subjects also underwent LGE MRI. Mean time posttransplantation was 5.5 years (range, 0.25-14 years). Seven patients had Stanford grade IV coronary allograft vasculopathy on intravascular ultrasound, 3 of whom had angiographic disease. Maximal intimal thickness and mean intimal index were 0.73±0.50 mm and 20.9±10.6%, respectively. On MRI, mean diameter of enhancement of vessel wall was 6.57±4.91 mm, and mean enhancement index (indexed to vessel lumen size) was 1.10±1.72. The control group showed little or no LGE. Correlation of LGE with maximal intimal thickness using the Pearson coefficient was 0.80 (P<0.001) and with mean intimal index was 0.92 (P<0.001). An MRI diameter >7.5 mm gave 86% sensitivity and 93% specificity.

CONCLUSIONS

LGE scores correlate well with traditional intravascular ultrasound measures. These promising early results encourage larger-scale clinical studies to investigate whether LGE MRI will allow closer follow-up and better prevention of coronary allograft vasculopathy in children.

Diagnostic and prognostic value of cardiovascular magnetic resonance in non-ischaemic cardiomyopathies

Cardiovascular Magnetic Resonance (CMR) is recognised as a valuable clinical tool which in a single scan setting can assess ventricular volumes and function, myocardial fibrosis, iron loading, flow quantification, tissue characterisation and myocardial perfusion imaging. The advent of CMR using extrinsic and intrinsic contrast-enhanced protocols for tissue characterisation have dramatically changed the non-invasive work-up of patients with suspected or known cardiomyopathy. Although the technique initially focused on the in vivo identification of myocardial necrosis through the late gadolinium enhancement (LGE) technique, recent work highlighted the ability of CMR to provide more detailed in vivo tissue characterisation to help establish a differential diagnosis of the underlying aetiology, to exclude an ischaemic substrate and to provide important prognostic markers. The potential application of CMR in the clinical approach of a patient with suspected non-ischaemic cardiomyopathy is discussed in this review.

Cardiovascular magnetic resonance in the evaluation of heart failure: a luxury or a need?

Heart failure is a common syndrome with multiple causes. Cardiovascular magnetic resonance (CMR), using the available range of technique, is establishing itself as the gold standard noninvasive test for determining the underlying causes, and adding prognostic value, guiding therapy. Progress is continuing and rapid with promising new techniques such as diffuse fibrosis assessment. This article discusses the diverse roles of CMR in heart failure.

Cardiovascular magnetic resonance: applications in daily practice

Over the last 10 years, the development of newer pulse sequences and applications in new clinical areas has enabled cardiovascular magnetic resonance to emerge as a powerful tool for the physicians to both diagnose and guide treatments of various cardiac pathologies. The greatest strengths of cardiovascular magnetic resonance include the assessment of ischemia and viability, evaluation of nonischemic cardiomyopathies, including myocarditis, pericardial disease, congenital heart disease, and tissue characterization of cardiac masses.