Diagnostic and prognostic value of dobutamine thallium-201 single-photon emission computed tomography after heart transplantation

Multimodality Imaging in Advanced Heart Failure for Diagnosis, Management and Follow-Up: A Comprehensive Review

Advanced heart failure (AHF) presents a complex landscape with challenges spanning diagnosis, management, and patient outcomes. In response, the integration of multimodality imaging techniques has emerged as a pivotal approach. This comprehensive review delves into the profound significance of these imaging strategies within AHF scenarios. Multimodality imaging, encompassing echocardiography, cardiac magnetic resonance imaging (CMR), nuclear imaging and cardiac computed tomography (CCT), stands as a cornerstone in the care of patients with both short- and long-term mechanical support devices. These techniques facilitate precise device selection, placement, and vigilant monitoring, ensuring patient safety and optimal device functionality. In the context of orthotopic cardiac transplant (OTC), the role of multimodality imaging remains indispensable. Echocardiography offers invaluable insights into allograft function and potential complications. Advanced methods, like speckle tracking echocardiography (STE), empower the detection of acute cell rejection. Nuclear imaging, CMR and CCT further enhance diagnostic precision, especially concerning allograft rejection and cardiac allograft vasculopathy. This comprehensive imaging approach goes beyond diagnosis, shaping treatment strategies and risk assessment. By harmonizing diverse imaging modalities, clinicians gain a panoramic understanding of each patient's unique condition, facilitating well-informed decisions. The aim is to highlight the novelty and unique aspects of recently published papers in the field. Thus, this review underscores the irreplaceable role of multimodality imaging in elevating patient outcomes, refining treatment precision, and propelling advancements in the evolving landscape of advanced heart failure management.

Negative Predictive Value and Prognostic Associations of Rb-82 PET/CT with Myocardial Blood Flow in CAV

BACKGROUND

Invasive coronary angiography (ICA) is the traditional screening modality for cardiac allograft vasculopathy (CAV). Positron emission tomography/computed tomography (PET/CT) scan with myocardial blood flow (MBF) quantification has emerged as a potential noninvasive alternative.

OBJECTIVES

The aim of the study was to validate the diagnostic and prognostic value of a previously published algorithm for diagnosing CAV via PET/CT scans with MBF in a larger population. The study also sought to assess the downstream use of ICA when using PET/CT scanning as a screening modality.

METHODS

Patients with heart transplantation without prior revascularization who underwent PET/CT scans with MBF were identified retrospectively. The accuracy of the algorithm was assessed in patients who underwent PET/CT scanning within 1 year of ICA. The prognostic value was assessed via a composite outcome of heart failure hospitalization, myocardial infarction, retransplantation, and all-cause mortality.

RESULTS

A total of 88 patients for the diagnostic portion and 401 patients for the prognostic portion were included. PET CAV 0 had high negative predictive value for moderate to severe CAV (97%) and PET CAV 2/3 had a high positive predictive value for moderate to severe CAV (68%) by ICA. The cohort was followed for a median of 1.2 (IQR: 1.0-1.8) years with 46 patients having an adverse event. The annualized event rates were 6.9%, 9.3%, and 30.8% for PET CAV 0, 1, and 2/3, respectively (P < 0.001).

CONCLUSIONS

An algorithm using PET/CT scanning with MBF demonstrates high a negative predictive value for CAV. PET CAV 2/3 is associated with a higher risk of adverse events and need for revascularization. PET/CT scanning with MBF is a reasonable alternative to ICA for screening for CAV.

Clinical Utility of SPECT in the Heart Transplant Population: Analysis From a Single Large-volume Center

BACKGROUND

Survival after heart transplant has greatly improved, with median survival now over 12 years. Cardiac allograft vasculopathy (CAV) has become a major source of long-term morbidity and mortality. Single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is used for CAV surveillance, but there is limited data on its prognostic utility.

METHODS

We retrospectively identified patients undergoing SPECT MPI for CAV surveillance at a single, large-volume center. Images were assessed with semiquantitative visual scoring (summed stress score [SSS] and summed rest score) and quantitatively with total perfusion defect (TPD).

RESULTS

We studied 503 patients (mean age 62.5, 69.3% male) at a median of 9.0 years post-transplant. During mean follow-up of 5.1 ± 2.5 years, 114 (22.6%) patients died. The diagnostic accuracy for significant CAV (ISHLT grade 2 or 3) was highest for SSS with an area under the curve of 0.650 and stress TPD (area under the curve, 0.648), with no significant difference between SSS and stress TPD (P = 0.061). Stress TPD (adjusted hazard ratio, 1.07; P = 0.018) was independently associated with all-cause mortality, while SSS was not (P = 0.064). The prognostic accuracy of quantitative assessment of perfusion tended to be higher compared with semiquantitative assessment, with the highest accuracy for stress TPD (area under the receiver operating curve 0.584).

CONCLUSIONS

While SPECT MPI identified a cohort of higher risk patients, with quantitative analysis of perfusion demonstrating higher prognostic accuracy. However, the overall prognostic accuracy was modest and alternative noninvasive modalities may be more suitable for CAV surveillance.

The role of non-invasive imaging modalities in cardiac allograft vasculopathy: an updated focus on current evidences

Cardiac allograft vasculopathy (CAV) is an obliterative and diffuse form of vasculopathy affecting almost 50% of patients after 10 years from heart transplant and represents the most common cause of long-term cardiovascular mortality among heart transplant recipients. The gold standard diagnostic technique is still invasive coronary angiography, which however holds potential for complications, especially contrast-related kidney injury and procedure-related vascular lesions. Non-invasive and contrast-sparing imaging techniques have been advocated and investigated over the past decades, in order to identify those that could replace coronary angiography or at least reach comparable accuracy in CAV detection. In addition, they could help the clinician in defining optimal timing for invasive testing. This review attempts to examine the currently available non-invasive imaging techniques that may be used in the follow-up of heart transplant patients, spanning from echocardiography to nuclear imaging, cardiac magnetic resonance and cardiac computed tomography angiography, weighting their advantages and disadvantages.

Diagnosis and management of cardiac allograft vasculopathy

One of the main causes of death beyond the first year after heart transplantation is cardiac allograft vasculopathy (CAV). This review summarises the current understanding of its complex pathophysiology, detection and treatment, including the available data on non-invasive imaging modalities used for screening and diagnosis. A better understanding of this entity is crucial to improving the long-term outcomes of the growing population of patients with a heart transplant.

Prediction of long-term (> 10 year) cardiovascular outcomes in heart transplant recipients: Value of stress technetium-99m tetrofosmin myocardial perfusion imaging

BACKGROUND

Myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) is useful in the evaluation of cardiac allograft vasculopathy (CAV) in heart transplant (HTx) recipients. The current study evaluated the long-term prognostic value of stress SPECT MPI for predicting all-cause mortality and cardiac events in HTx recipients.

METHODS

The study population consisted of 166 HTx recipients (mean age 54 ± 10 years, 84% male) who underwent exercise or dobutamine stress 99mTc-tetrofosmin SPECT MPI for the assessment of CAV. An abnormal SPECT MPI was defined as the presence of a fixed or a reversible perfusion defect. Endpoints were all-cause mortality, cardiac mortality, and non-fatal myocardial infarction (MI).

RESULTS

MPI abnormalities were detected in 55 patients (33%), including fixed defects in 28 patients (17%), partially reversible in 17 patients (10%), and completely reversible defects in 10 patients (6%). During a median follow-up of 12.8 years (range 0-15, mean follow-up 9.5 years), 109 (66%) patients died (all-cause mortality), of which 67 (40%) were due to cardiac causes. A total of 5 (3%) patients experienced a non-fatal MI. HTx recipients with a normal stress 99mTc-tetrofosmin SPECT MPI had a significantly better prognosis as compared with those with an abnormal study, up to 5 years after the initial test. The presence of a reversible perfusion defect was a significant predictor of all-cause mortality, cardiac mortality, and major cardiac events, during the entire follow-up period.

CONCLUSIONS

Stress 99mTc-tetrofosmin SPECT MPI provides valuable prognostic information for the prediction of long-term outcome in HTx recipients. Patients with a normal stress 99mTc-tetrofosmin SPECT MPI have a significantly better prognosis as compared with those with an abnormal study, up to 5 years after initial testing.

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.

New developments for the detection and treatment of cardiac vasculopathy

PURPOSE OF REVIEW

Cardiac allograft vasculopathy (CAV) is a major limitation to long-term survival after heart transplantation. Innovative new techniques to diagnose CAV have been applied to detect disease. This review will examine the current diagnostic and treatment options available to clinicians for CAV.

RECENT FINDINGS

Diagnostic modalities addressing the pathophysiology underlying CAV (arterial wall thickening and decreased coronary blood flow) improve diagnostic sensitivity when compared to traditional (angiography and dobutamine stress echocardiography) techniques.

SUMMARY

Limited options are available to prevent and treat CAV; however, progress has been made in making an earlier and more accurate diagnosis. Future research is needed to identify the optimal time to modify immunosuppression and investigate novel treatments for CAV.

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.

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.

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.

Prognostic value of rubidium-82 positron emission tomography in patients after heart transplant

BACKGROUND

Cardiac allograft vasculopathy is a key prognostic determinant after heart transplant. Detection and risk stratification of patients with cardiac allograft vasculopathy are problematic. Positron emission tomography using rubidium-82 allows quantification of absolute myocardial blood flow and may have utility for risk stratification in this population.

METHODS AND RESULTS

Patients with a history of heart transplant undergoing dipyridamole rubidium-82 positron emission tomography were prospectively enrolled. Myocardial perfusion and left ventricular ejection fraction were recorded. Absolute flow quantification at rest and after dipyridamole stress as well as the ratio of mean global flow at stress and at rest, termed myocardial flow reserve, were calculated. Patients were followed for all-cause death, acute coronary syndrome, and heart failure hospitalization. A total of 140 patients (81% men; median age, 62 years; median follow-up, 18.2 months) were included. There were 14 events during follow-up (9 deaths, 1 acute coronary syndrome, and 4 heart failure admissions). In addition to baseline clinical variables (estimated glomerular filtration rate, previously documented cardiac allograft vasculopathy), relative perfusion defects, mean myocardial flow reserve, and mean stress myocardial blood flow were significant predictors of adverse outcome.

CONCLUSIONS

Abnormalities on rubidium-82 positron emission tomography were predictors of adverse events in heart transplant patients. Larger prospective studies are required to confirm these findings.

[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.

Cardiac allograft vasculopathy: advances in diagnosis

Cardiac allograft vasculopathy (CAV), characterized by diffuse intimal thickening and luminal narrowing in the arteries of the allograft, is the leading cause of morbidity and mortality in cardiac transplant recipients. Many transplant centers perform routine annual surveillance coronary angiography. However, angiography can underdiagnose or miss CAV due to its diffuse nature. Intravascular ultrasound (IVUS) is more sensitive than angiography. IVUS provides not only accurate information on lumen size, but also quantification of intimal thickening, vessel wall morphology, and composition. IVUS has evolved as a valuable adjunct to angiography and the optimal diagnostic tool for early detection. Noninvasive testing such as dobutamine stress echocardiography and nuclear stress test have shown considerable accuracy in diagnosing significant CAV. Computed tomographic imaging and cardiac magnetic resonance imaging are promising new modalities but require further study. This article reviews the diagnostic methods that are currently available.

Myocardial perfusion image in asymptomatic postmenopausal women with physical inactivity and overweight

OBJECTIVE

This study aimed to investigate whether physical inactivity and overweight deteriorate myocardial perfusion and cardiac function in asymptomatic postmenopausal women.

METHODS

A prospective cross-sectional study design was used. Postmenopausal women recruited in this study were categorized into groups based on activity level and BMI: physically active, normal-weight group (PANw, n = 15, 60.9 ± 6.0 years), physically inactive, normal-weight group (PIANw, n = 13, 57.2 ± 5.0 years) and physically inactive, overweight group (PIAO, n = 26, 58.5 ± 5.8 years). Each subject took cardiopulmonary function tests and ECG-gated exercise (201)Tl myocardial perfusion imaging (MPI). Perfusion abnormalities, cardiac function indices, and (201)Tl lung-to- heart ratio (LHR) were derived.

RESULTS

The PIANw women had lower exercise capacity than PANw women. More subjects in PIANw (46%) or PIAO (48%) groups had worsening in left ventricular ejection fraction (LVEF) by exercise than subjects in PANw (7%) group. The PIAO women exhibited significantly lower exercise capacity and higher rest LHR than PANw women (LHR 0.41 ± 0.05 vs. 0.36 ± 0.06; p = 0.014). Abnormal MPI tended to increase in PIANw (38%) and PIAO (46%) women when compared with the PANw (27%) group.

CONCLUSIONS

Physically inactive, overweight postmenopausal women had higher rest (201)Tl lung uptake and worsening LVEF by exercise and tended to have higher prevalence of inducible ischemia, suggesting higher cardiovascular risks although asymptomatic.

International Society for Heart and Lung Transplantation working formulation of a standardized nomenclature for cardiac allograft vasculopathy-2010

The development of cardiac allograft vasculopathy remains the Achilles heel of cardiac transplantation. Unfortunately, the definitions of cardiac allograft vasculopathy are diverse, and there are no uniform international standards for the nomenclature of this entity. This consensus document, commissioned by the International Society of Heart and Lung Transplantation Board, is based on best evidence and clinical consensus derived from critical analysis of available information pertaining to angiography, intravascular ultrasound imaging, microvascular function, cardiac allograft histology, circulating immune markers, non-invasive imaging tests, and gene-based and protein-based biomarkers. This document represents a working formulation for an international nomenclature of cardiac allograft vasculopathy, similar to the development of the system for adjudication of cardiac allograft rejection by histology.

PET assessment of myocardial perfusion reserve inversely correlates with intravascular ultrasound findings in angiographically normal cardiac transplant recipients

Cardiac allograft vasculopathy (CAV) is the major determinant of long-term survival after heart transplantation. We aimed to evaluate the efficacy of PET as a noninvasive way to assess the early stages of CAV.

METHODS

Twenty-seven consecutive patients (20 men and 7 women; mean age +/- SD, 46 +/- 12 y) who had normal results on coronary angiography and normal left ventricular systolic function (ejection fraction >or= 60%) were enrolled at 2.5 +/- 2.1 y after transplantation. Myocardial blood flow (MBF) was assessed using dynamic (13)N-ammonia PET at rest and during adenosine-induced hyperemia, and myocardial perfusion reserve (MPR) was calculated as the ratio of hyperemic MBF to resting MBF. Regional (13)N-ammonia PET was assessed using a 5-point scoring system. The intravascular ultrasound (IVUS) measurements for the extent of intimal hyperplasia, including plaque volume index (calculated as [total plaque volume/total vessel volume] x 100%) and maximum area of stenosis, were compared with MPR by linear regression analysis.

RESULTS

In 27 angiographically normal cardiac transplant recipients, MBF at rest and during adenosine stress and MPR of the left anterior descending artery distribution correlated strongly with the other 2 coronary artery distribution territories (r >or= 0.97, P < 0.0001). Summed stress score and summed difference score showed a moderate inverse correlation with MPR (r = -0.41 and -0.49, respectively; P < 0.05) but not with IVUS measurements. MPR correlated inversely with plaque volume index (r = -0.40, P < 0.05) but not with maximal luminal stenosis as assessed by IVUS. In addition, MPR and IVUS measurements gradually inversely changed after heart transplantation (all P < 0.05).

CONCLUSION

This study confirms that CAV is a progressive process, diffusely involving the epicardial and microvascular coronary system. Plaque burden as determined by IVUS agrees well with MPR as assessed by PET in recipients with normal coronary angiography results. This finding suggests that dynamic (13)N-ammonia PET is clinically feasible for the early detection of CAV and can be used as a reliable marker of disease progression.

Diagnostic and prognostic value of myocardial perfusion gated SPECT in orthotopic heart transplant recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) limits long-term survival after heart transplantation. Diagnostic and prognostic value of gated single photon emission computed tomography (gated SPECT) has not been documented in this setting.

METHODS AND RESULTS

We identified 110 consecutive heart transplant recipients (with transplantation >18 months) who underwent stress-rest gated SPECT and coronary angiography within 1 month, and were clinically monitored in a single heart transplantation center. Visual scoring of perfusion and wall motion images used a 16-segment model. Left ventricular function was automatically calculated. Coronary angiography was normal in 64 patients (58%) and abnormal in 46 (any CAV, 42%), of whom 19 had severe stenoses. Sensitivity and negative predictive (NPV) value were .63 and .75 for identification of any CAV, and .84 and .96 for severe CAV. Cox regression analysis showed that independent predictors of cardiac death and retransplantation were the presence of any angiographic CAV lesions (RR = 8.816, P = .043) and a stress perfusion defect >3 segments (RR = 5.607, P = .0053). A stress perfusion defect >3 segments predicted the need for late coronary revascularization >2 months (RR = 6.11, P = .0002).

CONCLUSIONS

We conclude that perfusion gated SPECT is a useful noninvasive screening test and may be proposed to help identify heart transplant recipients with a high risk of poor clinical outcome. A normal gated SPECT was associated with a low risk of cardiac hard event and might alleviate the need for coronary angiography.

Long-term prognostic value of early poststress (99m)Tc-tetrofosmin lung uptake during exercise (SPECT) myocardial perfusion imaging

PURPOSE

The aim of this study was to determine the long-term prognostic value of early poststress lung/heart ratio (LHR) of (99m)Tc-tetrofosmin radioactivity.

METHODS

We studied 276 patients (aged 62.2 + or - 8.9 years, 168 men) with stress/rest (99m)Tc-tetrofosmin myocardial gated-SPECT and coronary angiography. To evaluate myocardial ischaemia, we calculated the summed stress score, summed rest score and summed difference score indices. For the eLHR calculation, an anterior image was acquired, 4-6 min after radiotracer injection at stress (eLHR was defined as mean counts per pixel in the lung region of interest divided by the mean counts per pixel in the myocardial region of interest). Cardiovascular death and nonfatal myocardial infarction were considered as hard cardiac events, and late revascularization procedures as soft cardiac events. The Cox proportional hazards model in a stepwise method was used to determine the independent predictors for hard and soft cardiac events.

RESULTS

During the follow-up period hard cardiac events occurred in 28 patients (10.1%) and soft cardiac events in 32 patients (11.6%). Implying multiple Cox regression analysis, eLHR was found to be a significant independent predictor for both soft and hard cardiac events. The hazard ratio (for a 0.1 unit increase) was 4.41 (95% CI 1.52-12.73, p=0.006) for soft cardiac events and 4.22 (95% CI 2.07-8.62, p<0.001) for hard cardiac events. The other significant prognostic factors were use of beta-blockers, the summed stress score and the use of nitrates for soft events, and exercise duration and the summed stress score for hard cardiac events.

CONCLUSION

Early poststress (99m)Tc-tetrofosmin LHR has an independent and powerful value in predicting hard and soft cardiac events.

Cardiac allograft vasculopathy: recent developments

Cardiac allograft vasculopathy (CAV) continues to limit the long-term success of cardiac transplantation. Recent insights have underscored the fact that innate and adaptive immune responses are involved in the pathogenesis of CAV. Vascular lesions are the result of cumulative endothelial injuries induced both by alloimmune responses and by nonspecific insults (including ischemia-reperfusion injury, viral infections, and metabolic disorders) in the context of impaired repair mechanisms. Intravascular ultrasound is the most sensitive method for detection of CAV, and progressive intimal thickening in the first posttransplant year identifies patients at high risk for future cardiovascular events. Encouraging results with regard to the detection of CAV by noninvasive methods should be an incentive to apply routine noninvasive imaging during mid- to long-term follow-up. Improved immunosuppressive drugs, including mycophenolate mofetil and proliferation signal inhibitors, as well as statins (in part via immunomodulation), have beneficial effects on CAV progression, although there is still a need to confirm the impact of vasodilators in improving outcome after heart transplantation. Coronary revascularization for CAV is only palliative, with no long-term survival benefit. Three main strategies for CAV prevention are currently under investigation: inhibition of growth factors and cytokines, cell therapy, and tolerance induction. However, because individual responses to an allograft change over time, assays to monitor the recipient's immune response and individualized methods for therapeutic immune modulation are clearly needed.

Diagnosis of graft coronary artery disease

PURPOSE OF REVIEW

Graft coronary artery disease is the leading cardiac cause of death in patients who have undergone cardiac transplantation. Due to denervation, classic symptoms of angina are not reliable. Many transplant centers have a protocol of routine annual surveillance cardiac angiography because treatment options are limited, especially with advanced disease. Angiography is an assessment of the arterial lumen, however, and can miss nonfocal disease. This paper reviews invasive and noninvasive diagnostic tools for graft coronary artery disease. Intravascular ultrasound is the most sensitive, but the cost and lack of widespread expertise make it unpopular. Noninvasive techniques have been studied. An ideal test would be sufficiently sensitive to detect disease and allow for prognostic information. Dobutamine echocardiography is the most sensitive noninvasive test but can have a high false-positive rate. It is also not universally available. Exercise nuclear imaging is specific and can be used as a confirmatory test in patients with positive dobutamine echocardiograms.

RECENT FINDINGS

Computed tomographic imaging and cardiac magnetic resonance imaging are exciting new modalities but require further study.

SUMMARY

There is no test sensitive and specific enough yet that can be confidently used to replace coronary angiography.

Multislice CT in Graft Vascular Disease. A Pilot Study

INTRODUCTION

Graft vessel disease (GVD) is one of the main long-term complications in heart transplant (HT) patients. At present, the diagnosis of this complication requires invasive procedures. Multislice CT is an emerging technique that allows visualization of the coronary anatomy, including the vascular lumen and wall thickness. Our objective was to establish the value of 16-detector multislice CT in the detection of GVD, compared with angiography and intravascular ultrasound (IVUS).

PATIENTS AND METHODS

We studied 32 HT patients, who had a mean follow-up of 2016 days. CT was performed 24 hours prior to angiography, associated with IVUS if the latter proved normal. Comparisons were subsequently made using contingency tables to establish the sensitivity, specificity, and predictive values of the CT.

RESULTS

Angiography was not performed on two patients, and eight were excluded from CT assessment due to serum creatinine values >1.5 mg/dL. Comparison of the CT findings with the invasive techniques yielded a sensitivity of 50%, a specificity of 81%, a negative predictive value of 81%, a positive predictive value of 50%, and a precision of 72%.

CONCLUSIONS

Our results suggested good performance of the technique in screening for GVD because a high negative predictive value was recorded. We plan to increase the number of patients and use the 64-detector CT system to ensure greater time and spatial resolution.

Usefulness of Progressive Inhomogeneity of Myocardial Perfusion and Chronotropic Incompetence in Detecting Cardiac Allograft Vasculopathy: Evaluation with Dobutamine Thallium-201 Myocardial SPECT

BACKGROUND

The aim of the study was to investigate the value of longitudinal follow-up of dobutamine thallium-201 single photon emission tomography ((201)Tl SPECT) in the development of significant cardiac allograft vasculopathy (CAV) after orthotopic heart transplantation.

METHODS

We studied 38 cardiac recipients (mean age 57 +/- 12 years) who underwent at least two follow-up dobutamine (201)Tl SPECT since January 1998. All patients had normal coronary angiography and normal left ventricular function initially.

RESULTS

After 2.3 +/- 1.8 years, 12 patients developed significant CAV and there were 4 cardiac deaths (1 died suddenly). Of the 99 scans retrospectively analyzed, patients with significant CAV had elevated values of inhomogeneity score, lung/heart ratio (LHR) at stress and lower left ventricular ejection fraction (all p < 0.05). The higher values of inhomogeneity were significantly correlated with higher stress LHR (r = 0.301, p = 0.021), and lower ejection fraction (r = -0.379, p < 0.001). Progressive inhomogeneity was noted in all heart recipients, and more rapid, although statistically insignificant, in patients who developed significant CAV. Ten patients had inadequate chronotropic response to dobutamine infusion up to 40 mug/kg/min in the follow-up studies. The late onset of chronotropic incompetence was an independent predictor of CAV development (p = 0.03).

CONCLUSIONS

Progressive inhomogeneity of myocardial perfusion, higher lung uptake at stress and chronotropic incompetence assessed by dobutamine (201)Tl myocardial SPECT provide incremental diagnostic value in detecting significant CAV.