Diagnostic and prognostic value of serial dobutamine stress echocardiography for noninvasive assessment of cardiac allograft vasculopathy: a comparison with coronary angiography and intravascular ultrasound

A Comprehensive Excursus of the Roles of Echocardiography in Heart Transplantation Follow-Up

Current guidelines for the care of heart transplantation recipients recommend routine endomyocardial biopsy and invasive coronary angiography as the cornerstones in the surveillance for acute rejection (AR) and coronary allograft vasculopathy (CAV). Non-invasive tools, including coronary computed tomography angiography and cardiac magnetic resonance, have been introduced into guidelines without roles of their own as gold standards. These techniques also carry the risk of contrast-related kidney injury. There is a need to explore non-invasive approaches providing valuable information while minimizing risks and allowing their application independently of patient comorbidities. Echocardiographic examination can be performed at bedside, serially repeated, and does not carry the burden of contrast-related kidney injury and procedure-related risk. It provides comprehensive assessment of cardiac morphology and function. Advanced echocardiography techniques, including Doppler tissue imaging and strain imaging, may be sensitive tools for the detection of minor myocardial dysfunction, thus providing insight into early detection of AR and CAV. Stress echocardiography may offer a valuable tool in the detection of CAV, while the assessment of coronary flow reserve can unravel coronary microvascular impairment and add prognostic value to conventional stress echocardiography. The review highlights the role of Doppler echocardiography in heart transplantation follow-up, weighting advantages and limitations of the different techniques.

Invasive Intracoronary Imaging of Cardiac Allograft Vasculopathy: Established Modalities and Emerging Technologies

Despite advances in the care of heart transplant recipients during the past 5 decades, cardiac allograft vasculopathy (CAV) continues to be a major barrier to long-term survival. The early diagnosis and treatment of CAV is crucial for improving long-term outcomes. Coronary angiography, the current gold standard for CAV screening, has low sensitivity for detecting early CAV. Increasingly, invasive intracoronary imaging modalities that provide a more detailed analysis of vessel anatomy and allow for plaque characterization are being used to detect CAV earlier after transplant and uncover mechanistic insights. Studies validating these emerging imaging platforms are needed before their widespread adoption.

Prognostic Value of Exercise Stress Echocardiography in Pediatric Cardiac Transplant Recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a leading cause of long-term morbidity and mortality in pediatric heart transplant (HTx) recipients. Exercise stress echocardiography (ESE) has been shown to be useful in the detection of angiographically-confirmed CAD in children. However, the prognostic utility of ESE for prediction of cardiac events in HTx survivors is unknown.

STUDY AIM AND HYPOTHESIS

Therefore, we aim to assess if an abnormal (positive) ESE will be associated with a higher risk of future cardiovascular (CV) outcomes in pediatric HTx recipients.

MATERIAL AND METHODS

We conducted a retrospective review of CV outcomes of a cohort of 95 pediatric HTx recipients who underwent 188 ESE over a 10-year period. A composite endpoint for CV events including myocardial infarction, hospitalization for non-rejection heart failure, coronary revascularization, need for repeat transplantation, and death was used. Based on the interpretation of the ESE results, each ESE study was classified for this study as either positive (abnormal), or negative (normal) for ischemia. Results of the coronary angiograms performed near the time of ESE were also assessed and classified for this study as positive (abnormal) or negative (normal) for CAV according to standard HTx criteria for CAV.

RESULTS

51 (27%) ESE were positive for ischemia. There was a total of 35 CV events in 23 patients. A positive ESE was associated with increased risk of any CV event [Hazard ratio [HR] 3.55, 95% CI 1.52, 8.28, and also an increased risk of CV death (HR 3.19, 95% CI 1.23, 8.28) Freedom from composite CV outcome at 1, 2, and 3 years following a positive ESE was 89.9% (CI = 77.3%, 95.7%), 81.5% (CI = 65.9%, 90.5%), and 63.2% (CI = 41.9%, 78.5%), respectively. Freedom from composite cardiovascular outcome at 1, 2, and 3 years following a negative ESE was 99.3% (94.8, 99.9), 98.4% (93.6, 99.6), and 97.0% (90.6, 99.1) respectively. No patient died within 1 year of a negative ESE.

CONCLUSIONS

In this largest study of ESE in pediatric HTx recipients, a positive or abnormal ESE is associated with increased future cardiovascular morbidity and mortality. Conversely, a negative ESE can help predict CV event-free survival. Even in the setting of a normal ANG, our pilot data show that an abnormal ESE may be still clinically important. Use of ESE in follow-up may improve risk stratification and management of pediatric HTx recipients.

Invasive Coronary Imaging Assessment for Cardiac Allograft Vasculopathy: State-of-the-Art Review

Heart transplantation is the standard of care treatment for end-stage heart failure. Therapeutic advances including enhanced immunosuppression and aggressive infectious prophylaxis have led to increased life-expectancy following transplantation; however, cardiac allograft vasculopathy (CAV) remains a leading cause of morbidity and mortality. Although coronary angiography is the current guideline-recommended diagnostic modality for invasive CAV screening, it is limited in its ability to detect early and/or diffuse disease. Efforts to improve outcomes for heart transplant recipients with CAV have focused on developing diagnostic tools with greater sensitivity to capture early CAV in order to better understand the pathobiology and implement treatment to slow disease progression sooner after transplant. The contemporary invasive imaging armamentarium for CAV surveillance includes coronary angiography, intravascular ultrasound, and newer technologies including optical coherence tomography and near-infrared spectroscopy. The present review outlines the use of and data in support of these imaging platforms in the CAV arena and highlights the potential advantages and limitations of each of these modalities.

Non-Invasive Imaging in the Evaluation of Cardiac Allograft Vasculopathy in Heart Transplantation: A Systematic Review

Cardiac allograft vasculopathy (CAV) is the leading cause of long-term graft dysfunction in patients with heart transplantation and is linked with significant morbidity and mortality. Currently, the gold standard for diagnosing CAV is coronary imaging with intravascular ultrasound (IVUS) during traditional invasive coronary angiography (ICA). Invasive imaging, however, carries increased procedural risk and expense to patients in addition to requiring an experienced interventionalist. With the improvements in non-invasive cardiac imaging modalities such as transthoracic echocardiography (TTE), computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET), an alternative non-invasive imaging approach for the early detection of CAV may be feasible. In this systematic review, we explored the literature to investigate the utility of non-invasive imaging in diagnosis of CAV in >3000 patients across 49 studies. We also discuss the strengths and weaknesses for each imaging modality. Overall, all four imaging modalities show good to excellent accuracy for identifying CAV with significant variations across studies. Majority of the studies compared non-invasive imaging with ICA without intravascular imaging. In summary, non-invasive imaging modalities offer an alternative approach to invasive coronary imaging for CAV. Future studies should investigate longitudinal non-invasive protocols in low-risk patients after heart transplantation.

The fundamental role of stress echo in evaluating coronary artery disease in specific patient populations

Stress echocardiography (SE) was initially used for assessing patients with known or suspected coronary heart disease by detecting and evaluating myocardial ischemia and viability. The implementation of SE has gradually been extended to several cardiovascular diseases beyond coronary artery disease, and SE protocols have been modified and adapted for the detection of coronary artery disease (CAD) or other cardiovascular diseases in specific patient populations. This review attempts to summarize current data concerning SE implementation and clinical value in these specific and diverse populations: patients with an intramural course of a coronary artery - known as a myocardial bridge, chronic severe or end-stage hepatic disease, chronic severe or end-stage kidney disease, cardiac allograft vasculopathy, patients scheduled for solid-organ transplantation and other intermediate and high-risk surgery and, finally, patients treated with anticancer drugs or radiotherapy.

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.

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.

Intravascular ultrasound-guided selection for early noninvasive cardiac allograft vasculopathy screening in heart transplant recipients

BACKGROUND

Noninvasive screening for cardiac allograft vasculopathy (CAV) instead of invasive coronary angiography (ICA) within the first 3 to 5 years after heart transplantation (HTx) is controversial. We evaluated a strategy of intravascular ultrasound (IVUS)-guided conversion to early noninvasive screening post-HTx.

METHODS

A single-center study of 103 consecutive HTx recipients from 2008 to 2018 undergoing ICA at 1 year post-HTx. Of 88 patients with normal 1-year ICA, sixty-six patients underwent IVUS examination for risk stratification by maximal intimal thickness (MIT) into (i) low-risk group (MIT < 0.5 mm) (n = 41, 62%) followed noninvasively versus (ii) high-risk group (MIT ≥ 0.5 mm) (n = 25, 38%) followed with yearly ICA. Both groups underwent ICA at year 5 post-HTx. We evaluated a combined endpoint of angiographic CAV and death at 5-year follow-up post-HTx.

RESULTS

Median (IQR) age was 51 (33-60) years, and 62% were male. Follow-up was 1443 (1125-1456) days. Survival free from angiographic CAV (Kaplan-Meier) differed significantly between groups (log-rank p < .0001). A subgroup of 27 patients completed ICA at year 5, and the proportion of angiographic CAV was significantly lower in low-risk patients (p < .0001).

CONCLUSION

IVUS-guided selection for early noninvasive CAV screening appears to be safe and holds promise as a novel strategy for early risk stratification and CAV surveillance post-HTx.

Pharmacological vs Exercise Stress Echocardiography for Detection of Cardiac Allograft Vasculopathy

Objective

To test the hypothesis that exercise and dobutamine would provide levels of cardiac stress that are comparable to those achieved in a general stress test population, and to one another, in heart transplant recipients.

Patients and Methods

From February 10, 2015, to December 31, 2017, 81 patients underwent exercise stress (N=45) or dobutamine stress (N=36) echocardiography at a mean ± SD of 11±14 years (range, 1-29 years) after heart transplant. Hemodynamic and inotropic responses were compared between groups, and to a prior test, longitudinally. The primary outcome was peak heart rate (HR) × systolic blood pressure (SBP).

Results

Peak exercise HR × SBP × 10⁻³ was a mean ± SD of 24.9±4.9 mm Hg/min for exercise stress vs 21.2±3.4 mm Hg/min during dobutamine stress (P<.001). In 35 patients who underwent a dobutamine stress test followed later by another dobutamine stress test, peak HR × SBP changed by 4.2%±16% (P=.05). In 25 patients who underwent a dobutamine stress test followed later by an exercise stress test, peak HR × SBP increased by 12%±23% (P=.002 vs serial dobutamine stress tests). Peak exercise HR did not correlate with time since heart transplant, patient age, or graft age. Peak dobutamine HR correlated modestly with patient age (r²=0.28). Inotropic responses were similar in both groups. Overall, patients preferred exercise stress testing to dobutamine stress tests. Dobutamine stress testing was more expensive than exercise stress tests.

Conclusion

Exercise induces a level of cardiac stress that is equal to or greater than dobutamine-induced stress, at lower cost, in heart transplant recipients who express preference for exercise stress testing.

Cardiac Allograft Vasculopathy: The Enduring Enemy of Cardiac Transplantation

Cardiac allograft vasculopathy remains a major limiting factor in the long-term survival of the heart transplant recipient. Our understanding of its pathogenesis is continuously evolving as advances in imaging modalities have allowed a direct window into the natural history of the disease. Innovation in diagnostic modalities has spurred the proliferation of prognostic tools and biomarkers. And in parallel, pharmacological advances have emerged that have helped ameliorate the disease's progressive course.

Initial Intravascular Ultrasound Without a Routine Early Baseline Study in the Evaluation of Cardiac Transplant Vasculopathy has Prognostic Valve

BACKGROUND

Abnormal minimal intimal thickening (MIT) on intravascular ultrasound (IVUS) defined as difference of ≥0.5 mm between baseline and one-year post-transplantation has been shown to have prognostic value. The goal of this retrospective cohort study was to evaluate whether abnormal MIT found on routine IVUS studies in cardiac transplant patients after 6 months without an early baseline study (modified MIT or MMIT), has any prognostic value. Furthermore, we evaluated the prognostic effect of serial IVUS performed beyond one year.

METHODS

A cohort of 149 cardiac transplant patients who underwent IVUS examination > 6 months post-transplant were evaluated retrospectively. Of these 149 patients, 109 patients underwent a subsequent IVUS study approximately 1 year following the initial study. MMIT values of ≥0.5 mm without an early baseline study were correlated with major adverse cardiac event (MACE).

RESULTS

The all-cause mortality was 4.7% (5/107) in patients with MMIT of <0.5 mm vs. 14.6% (6/41) in patients with MMIT of ≥0.5 mm [hazards ratio (HR): 3.2; 95% confidence interval (CI): 1.002-12.17; p = 0.039]. The overall MACE rate was 8.4% (9/107) in patients with MMIT of <0.5 mm vs. 24.4% (10/41) in patients with MMIT of ≥0.5 mm [HR: 6.7; 95% CI: 1.30-9.42; p = 0.009]. After adjusting for age, abnormal MMIT remained a significant independent predictor of MACE (HR: 3.93; CI 1.21-12.81; p = 0.023).

CONCLUSIONS

The presence of abnormal MMIT noted on IVUS performed after 6 months post-transplantation without a routine baseline IVUS carries important prognostic value.

Diagnostic accuracy of dobutamine stress echocardiography in the detection of cardiac allograft vasculopathy in heart transplant recipients: A systematic review and meta-analysis study

BACKGROUND

Dobutamine stress echocardiography (DSE) is a well-established imaging modality used to screen patients with mild-to-moderate risk for coronary artery disease. In heart transplantation recipients, cardiac allograft vasculopathy (CAV) is a common and lethal complication. The use of DSE to detect CAV showed promising results initially, but later studies showed limitation in its use to detect CAV. It is unclear if this cohort of patients derives benefit from DSE.

METHODS

We searched PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, and Scopus from inception through March 2018 for studies examining the accuracy of DSE in correlation to coronary angiography (CA) or intravascular ultrasound (IVUS) to detect CAV. Original studies comparing the ability of DSE to detect CAV in comparison with CA or IVUS were included. Relevant data were extracted and hierarchical summary receiver operating characteristic analysis was conducted to test the overall diagnostic accuracy of DSE for patients with CAV.

RESULTS

Eleven studies (749 participants) met the inclusion criteria. The sensitivity of DSE varied from 1.7% to 93.8%, and specificity, from 54.8% to 98.8%. Pooled sensitivity was 60.2% (95% confidence interval (CI), 33.0%-82.3%) and specificity 85.7% (95% CI, 73.8%-92.7%). DSE had an overall diagnostic odds ratio (OR) of 9.1 (95% CI, 4.6-17.8), positive likelihood ratio (LR+) of 4.1 (95% CI, 2.8-6.1), negative likelihood ratio (LR-) of 0.47 (95% CI: 0.23-0.73), and area under curve (AUC) of 0.73 (95% CI, 0.72-0.75). Heterogeneity among studies was not statistically significant (τ²  = 0.32, Cochran's Q = 9.5, P = 0.483).

CONCLUSION

Dobutamine stress echocardiography has a limited sensitivity to detect early CAV but its specificity is much higher. There remains a need for an alternative noninvasive modality which will have both high sensitivity and high specificity for detecting CAV.

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.

Current diagnostic and treatment strategies for cardiac allograft vasculopathy

Heart transplantation remains the most durable treatment for end-stage heart disease that is not amenable to coronary revascularization or anti-arrhythmic therapies. Cardiac allograft vasculopathy (CAV) remains one of the main contributors to morbidity and mortality post heart transplant. Nonimmune and immune factors that influence CAV can be modified after a heart transplant. Given the potential silent nature of CAV in the denervated heart, early diagnosis of CAV is critical. Diagnosis and treatment of CAV remain key areas of investigation to improve patient care and quality of life post heart transplant. While repeat heart transplantation is an option in the treatment of significant CAV, outcomes following retransplantation are inferior to outcomes following first heart transplant. Repeat heart transplantation is limited to a select group of patients after index heart transplant.

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.

Cardiac Transplantation in the New Era

The prevalence of heart failure continues to rise due to the aging population and longer survival of people with conditions that lead to heart failure, eg, hypertension, diabetes, and coronary artery disease. Although medical therapy has had an important impact on survival of patients and improving quality of life, heart transplantation remains the definitive therapy for patients that eventually deteriorate. Since the first successful heart transplantation in 1967, significant improvements have been made regarding donor and recipient selection, surgical techniques, and postoperative care. However, the number of potential organ donors has not changed and the growing number of patients in need for transplantation has resulted an increase in waiting list time, and the need for mechanical support. To overcome this issue, the United Network for Organ Sharing implemented an allocation system to prioritize the sickest patients on the list to receive organs. Despite the careful selection of patients, pretransplant immunological screening, and multidrug immunosuppressive regimens, acute and chronic rejections occur and potentially limit graft and patient survival. Treatment for rejection largely depends on the type of rejection, the presence of hemodynamic compromise, and time after transplantation. The limiting factor for long-term graft survival is allograft vasculopathy, an immune-mediated process causing diffuse narrowing of the coronary arteries. Percutaneous coronary intervention and coronary artery bypass surgery are often not an option for this vasculopathy due to the lack of focal lesions, and retransplantation is the only option in appropriate patients.

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.

Dobutamine stress echocardiography after cardiac transplantation: implications of donor-recipient age difference

Dobutamine stress echocardiography (DSE) is widely used during follow-up after cardiac transplant for the diagnosis of allograft vasculopathy. We investigated the effect of donor–recipient age difference on the ability to reach target heart rate (HR) during DSE.

All cardiac transplant patients who were undergoing DSE over a 3-year period in a single institution were reviewed. Target HR was specified as 85%×(220 – patient age). Further patient and donor demographics were obtained from the local transplant database.

61 patients (45 male, 55±12 years) were stressed with a median dose of 40 mcg/kg per min dobutamine. Only 37 patients (61%) achieved target HR. Donor hearts were mostly younger (mean 41±14 years, P<0.001), with only 11 patients (18%) having donors who were older than they were. Patients with older donors required higher doses of dobutamine (median 50 vs 30 mcg/kg per min, P<0.001) but achieved a lower percentage target HR (mean 93% vs 101%, P=0.003) than those with younger donors did. Patients with older donors were less likely to achieve target HR (18% vs 67%, P=0.003).

In conclusion, donor–recipient age difference affects the likelihood of achieving target HR and should be considered when a patient is consistently unable to achieve ‘adequate’ stress according to the patient's age.

Cardiac allograft vasculopathy: diagnosis, therapy, and prognosis

Development of cardiac allograft vasculopathy represents the major determinant of long-term survival in patients after heart transplantation. Due to graft denervation, these patients seldom present with classic symptoms of angina pectoris, and the first clinical presentations are progressive heart failure or sudden cardiac death. Although coronary angiography remains the routine technique for coronary artery disease detection, it is not sensitive enough for screening purposes. This is especially the case in the first year after transplantation when diffuse and concentric vascular changes can be easily detected only by intravascular ultrasound. The treatment of the established vasculopathy is disappointing, so the primary effort should be directed toward early prevention and diagnosis. Due to diffuse vascular changes, revascularization procedures are restricted only to a relatively small proportion of patients with favorable coronary anatomy. Percutaneous coronary intervention is preferred over surgical revascularization since it leads to better acute results and patient survival. Although there is no proven long-term advantage of drug-eluting stents for the treatment of in-stent restenosis, they are preferred over bare-metal stents. Severe vasculopathy has a poor prognosis and the only definitive treatment is retransplantation. This article reviews the present knowledge on the pathogenesis, diagnosis, treatment, and prognosis of cardiac allograft vasculopathy.

Coronary microvasculopathy in heart transplantation: Consequences and therapeutic implications

Despite the progress made in the prevention and treatment of rejection of the transplanted heart, cardiac allograft vasculopathy (CAV) remains the main cause of death in late survival transplanted patients. CAV consists of a progressive diffuse intimal hyperplasia and the proliferation of vascular smooth muscle cells, ending in wall thickening of epicardial vessels, intramyocardial arteries (50-20 μm), arterioles (20-10 μm), and capillaries (< 10 μm). The etiology of CAV remains unclear; both immunologic and non-immunologic mechanisms contribute to endothelial damage with a sustained inflammatory response. The immunological factors involved are Human Leukocyte Antigen compatibility between donor and recipient, alloreactive T cells and the humoral immune system. The non-immunological factors are older donor age, ischemia-reperfusion time, hyperlipidemia and CMV infections. Diagnostic techniques that are able to assess microvascular function are lacking. Intravascular ultrasound and fractional flow reserve, when performed during coronary angiography, are able to detect epicardial coronary artery disease but are not sensitive enough to assess microvascular changes. Some authors have proposed an index of microcirculatory resistance during maximal hyperemia, which is calculated by dividing pressure by flow (distal pressure multiplied by the hyperemic mean transit time). Non-invasive methods to assess coronary physiology are stress echocardiography, coronary flow reserve by transthoracic Doppler echocardiography, single photon emission computed tomography, and perfusion cardiac magnetic resonance. In this review, we intend to analyze the mechanisms, consequences and therapeutic implications of microvascular dysfunction, including an extended citation of relevant literature data.

The risk of adverse events associated with atropine administration during dobutamine stress echocardiography in cardiac transplant patients: a 28-year single-center experience

BACKGROUND

Although dobutamine stress echocardiography (DSE) is performed in heart transplant patients, the safety profile of atropine administration in DSE in this setting is unclear.

METHODS AND RESULTS

We identified heart transplant patients who received atropine during DSE from January 1984 to August 2011 at our institution and compared them with a propensity-scored matched control group of heart transplant patients who underwent DSE without atropine. Adverse events were defined as significant arrhythmias (sinus arrest, Mobitz type II heart block, complete heart block, ventricular tachycardia, or ventricular fibrillation), hypotension requiring hospitalization, syncope or presyncope, myocardial infarction, and death. Forty-five heart transplant patients (median age 62 years, 82% male) received 0.2-1 mg atropine during DSE. Of these, 1 patient (2.2%) developed temporary complete heart block. No adverse events were identified in the control group of 154 patients who received dobutamine without atropine.

CONCLUSIONS

Our findings suggest that complete heart block can occur infrequently with the administration of atropine in heart transplant patients undergoing DSE. Therefore, patients should be appropriately monitored for these adverse events during and after DSE.

Myocardial infarction in an adult with cystic fibrosis and heart and lung transplant

We present a case of myocardial infarction in a 19 year old female with cystic fibrosis who had a heart and lung transplant performed at the age of four years old. She presented atypically with a one day history of severe, intermittent, central, sharp chest pain, radiating to her back and down her left arm. A coronary angiogram showed proximal stenosis of the left anterior descending artery and right coronary artery. She was treated with percutaneous coronary intervention, involving drug eluting stents to the left anterior descending artery (LAD) and the right coronary artery (RCA). In this study we discuss the pathophysiology, investigations and treatment of cardiac transplant vasculopathy. Although complete reversal of LAD and RCA stenosis was achieved, routine follow-up with coronary angiography and careful control of cardiac risk factors will be important to identify and reduce future restenosis and adverse cardiac events.

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.

[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.