Enhanced detection of cardiac allograft arterial disease with intracoronary ultrasonographic imaging

New Non-Invasive Imaging Technologies in Cardiac Transplant Follow-Up: Acquired Evidence and Future Options

Heart transplantation (HT) is the established treatment for end-stage heart failure, significantly enhancing patients' survival and quality of life. To ensure optimal outcomes, the routine monitoring of HT recipients is paramount. While existing guidelines offer guidance on a blend of invasive and non-invasive imaging techniques, certain aspects such as the timing of echocardiographic assessments and the role of echocardiography or cardiac magnetic resonance (CMR) as alternatives to serial endomyocardial biopsies (EMBs) for rejection monitoring are not specifically outlined in the guidelines. Furthermore, invasive coronary angiography (ICA) is still recommended as the gold-standard procedure, usually performed one year after surgery and every two years thereafter. This review focuses on recent advancements in non-invasive and contrast-saving imaging techniques that have been investigated for HT patients. The aim of the manuscript is to identify imaging modalities that may potentially replace or reduce the need for invasive procedures such as ICA and EMB, considering their respective advantages and disadvantages. We emphasize the transformative potential of non-invasive techniques in elevating patient care. Advanced echocardiography techniques, including strain imaging and tissue Doppler imaging, offer enhanced insights into cardiac function, while CMR, through its multi-parametric mapping techniques, such as T1 and T2 mapping, allows for the non-invasive assessment of inflammation and tissue characterization. Cardiac computed tomography (CCT), particularly with its ability to evaluate coronary artery disease and assess graft vasculopathy, emerges as an integral tool in the follow-up of HT patients. Recent studies have highlighted the potential of nuclear myocardial perfusion imaging, including myocardial blood flow quantification, as a non-invasive method for diagnosing and prognosticating CAV. These advanced imaging approaches hold promise in mitigating the need for invasive procedures like ICA and EMB when evaluating the benefits and limitations of each modality.

Early Growth Response-1: Friend or Foe in the Heart?

Cardiovascular disease is a major cause of mortality and morbidity worldwide. Early growth response-1 (Egr-1) plays a critical regulatory role in a range of experimental models of cardiovascular diseases. Egr-1 is an immediate-early gene and is upregulated by various stimuli including shear stress, oxygen deprivation, oxidative stress and nutrient deprivation. However, recent research suggests a new, underexplored cardioprotective side of Egr-1. The main purpose of this review is to explore and summarise the dual nature of Egr-1 in cardiovascular pathobiology.

Intravascular ultrasound for cardiac allograft vasculopathy detection

Cardiac allograft vasculopathy (CAV) after heart transplantation is a fibro-proliferative process affecting coronary arteries of the graft in up to 46.8% of the cases during the first 10 years post-transplantation. It is one of the main causes of graft loss and death. Due to graft denervation, CAV causing ischemia is usually clinically silent until the disease is far advanced. In this study, we compared coronary angiography with intravascular ultrasound (IVUS) for CAV detection. OUTCOMES: A total of 114 patients with HTx who underwent coronary angiography and IVUS between March 2018 and March 2019 were included. Mean follow-up was 87 ± 61 month. Lesions documented by coronary angiography were found in only 27 (24%) of the 114 patients. IVUS revealed ISHLT CAV ₀ in 87 patients (76.3%); ISHLT CAV₁ in 15 (13,1%) and ISHLT CAV₂ and CAV₃ in 6 patients (5.2%) each. Among 328 IVUS images, maximum intimal thickness (MIT) >0.5 mm was obtained in 60 vessels (52%) with 24 patients having three-vessel and 19 two-vessel involvement. CONCLUSION: As an adjunct to conventional coronary angiography to detect angiographically silent CAV in heart transplant patients, IVUS is a reliable and safe technique with a low complication rate. Large multicenter studies are necessary to confirm these findings and the potential long-term clinical impact of early detection in clinically and angiographically silent phase.

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.

Coronary Angiography for Follow-up of Heart Transplant Recipients: Insights From TIMI Frame Count and TIMI Myocardial Perfusion Grade

BACKGROUND

The aim of this study was to evaluate the course of Thrombolysis in Myocardial Infarction (TIMI) frame count (TIMI FC) and myocardial perfusion grade (TIMI MPG) in heart transplant recipients and whether these parameters could predict mortality.

METHODS

Sixty-two heart transplant recipients were enrolled in this study. All patients had coronary angiography at baseline and at 1 year, which were evaluated for TIMI FC and TIMI MPG. Also, 50 vessels in 35 patients were analyzed with volumetric intravascular ultrasound (IVUS) at baseline and at 1 year. Rejection episodes and mortality were recorded during the follow-up period.

RESULTS

The mean follow-up interval was 51.5 +/- 17.2 months (range 12.2 to 78.4 months). TIMI FCs of all three coronary arteries and global TIMI FC (gTIMI FC) significantly increased from baseline during the first year (p < 0.0001). TIMI MPG deteriorated significantly (p < 0.0001 for left anterior descending and circumflex coronary arteries, p = 0.002 for right coronary artery). There was no correlation between changes in TIMI FC and progression of transplant vasculopathy as assessed by IVUS. Episodes of Grade > or = 3A rejection were significantly more frequent in the stable gTIMI FC group (p = 0.03). Mortality rate was significantly higher in the group with increasing gTFC (p = 0.02).

CONCLUSIONS

gTIMI FCs and TIMI FCs of coronary arteries increase, and TIMI MPG gradually deteriorates during the first year after transplantation. Mortality rate is significantly higher in patients whose gTIMI FC increases from baseline. Change in gTIMI FC is a simple quantitative predictor of long-term mortality in heart transplant recipients.

Vascular Remodeling 1 Year After Cardiac Transplantation

BACKGROUND

The belief that vascular remodeling and intimal hyperplasia are causes of luminal narrowing in cardiac allograft vasculopathy (CAV) is controversial. This study evaluated the relationship of vascular remodeling and intimal hyperplasia to luminal narrowing 1 year after orthotopic heart transplantation.

METHODS

Intravascular ultrasound imaging was performed on 190 cardiac transplant recipients at baseline and again 1 year after transplantation as part of a randomized trial of mycophenolate mofetil (MMF) and azathioprine (Aza). Studies 1 year apart were matched at 625 sites. All sites were classified into positive, non-significant and negative remodeling patterns, depending on a change of +/-10% in external elastic membrane area. Of the 190 patients, 99 were randomized to receive MMF, and 91 to receive Aza.

RESULTS

A total of 625 sites were observed. Of these, 52% had no remodeling, 25% exhibited vessel dilation, and 23% had vessel shrinkage in the presence of variable intimal growth (Delta intimal area: 0.73 +/- 1.70 mm2, p < 0.0001; 1.23 +/- 2.02 mm2, p < 0.0001; and 0.20 +/- 1.40 mm2, p = 0.09, respectively). Sixty percent of the lumen loss was due to a decrease in external elastic membrane area and 40% to an increase in intimal area (p = 0.005). Compared with Aza-treated patients, the MMF-treated patients had a lower incidence of vessel shrinkage (17% vs 28%, p = 0.001), and a trend for smaller maximum intimal thickness (0.21 +/- 0.25 mm vs 0.29 +/- 0.31 mm, p = 0.052).

CONCLUSIONS

Positive remodeling is associated with intimal growth, but negative remodeling does not correlate with any specific change in intimal hyperplasia. Constrictive remodeling is more responsible than intimal hyperplasia for the luminal narrowing that occurs. MMF is more efficacious than azathioprine in preventing the development of CAV at 1 year, by reducing the degree and incidence of vessel shrinkage and the progression of intimal hyperplasia.

Value of radionuclide studies in cardiac transplantation

Effective noninvasive evaluation of acute and chronic allograft rejection remains an important challenge in patients with cardiac transplantation. Radionuclide studies have demonstrated utility because of their ease of use, giving relevant information about the pathophysiology of the transplanted heart, along with valuable diagnostic and prognostic indicators. This article focuses on reviewing the pathophysiological changes of the transplanted heart and implications for radionuclide studies.

Angiographic, Pathologic, and Clinical Relationships in Coronary Artery Disease in Cardiac Allografts

BACKGROUND

To date, the etiologic factors involved in the development of allograft coronary disease remain speculative and the treatment uncertain. The purpose of this study was to review the relationship of clinical, angiographic, and pathologic features of cardiac allograft vascular disease in a large population of heart transplant recipients followed for up to 15 years.

METHODS

From 1981 to 1996, 789 angiograms from 255 cardiac allografts were reviewed to determine the prevalence and severity of coronary artery disease. Demographic, clinical, and laboratory variables were analyzed to identify factors associated with the presence of angiographic coronary artery disease. In addition, pathologic examination was performed on many of the lost grafts.

RESULTS

Unsuspected severe donor coronary artery disease may be responsible for up to 10% of early graft failures. Angiographic coronary artery disease prevalence increased by approximately 10% with every 2-year interval after transplantation. Angiographic coronary artery disease consisted most often of minor luminal irregularities. Severe disease occurred in 12% of patients. At 1 year, the most significant factors associated with the presence of coronary artery disease were older donor age and the number of rejection episodes. Immunologic factors as well as traditional coronary risk factors such as hypercholesterolemia and hyperglycemia may play an important role in the genesis and progression of later-developing abnormalities.

CONCLUSIONS

Cardiac allograft coronary artery disease is a major limiting factor to the long-term success of cardiac transplantation. Immune processes, as well as traditional coronary artery disease risk factors, appear to play a role in the development of this disease.

Current understanding and management of allograft vasculopathy

Cardiac allograft vasculopathy (CAV) is the major obstacle to long-term survival after heart transplantation. It is a rapidly progressive, obliterative form of coronary vasculopathy distinct from classic atheromatous disease. The pathogenesis is most likely multifactorial and involves both alloantigen dependent and independent mechanisms. Since there is no definitive treatment for CAV and new immunosuppressive agents can only slow the progression of this disease, the prophylaxis and modification of numerous risk factors remains the foundation of posttransplant management in the heart transplant recipient. In this review, we discuss current understanding of the pathogenesis of CAV, novel diagnostic and therapeutic avenues and explore optimal approaches to risk factors modification.

Intravascular ultrasound evidence of angiographically silent progression in coronary atherosclerosis predicts long-term morbidity and mortality after cardiac transplantation

OBJECTIVES

The aim of this study was to determine whether angiographically silent early coronary intimal thickening could predict long-term morbidity and mortality.

BACKGROUND

Although intravascular ultrasound (IVUS) is widely used to detect early transplant coronary disease, its prognostic significance has not been well defined.

METHODS

The study cohort consisted of 143 patients who underwent early multivessel (2.1 +/- 0.7 arteries/patient) IVUS examination 1.0 +/- 0.5 month and 12.0 +/- 1.0 month after transplantation. The change in intimal thickness was evaluated using paired analysis of 1,069 matched sites. Rapidly progressive vasculopathy was defined as the change in intimal thickness >/=0.5 mm. Patients were followed for a primary end point of all-cause mortality and a secondary composite end point of mortality and nonfatal myocardial infarction (MI). Angiographic disease, defined as any >/=50% diameter stenosis, was assessed in 126 patients.

RESULTS

Intravascular ultrasound at one year demonstrated rapid progression in 54 (37%) of 143 patients and new lesions in 67 (47%) of 143 of patients. At a mean clinical follow-up of 5.9 years, more patients with rapidly progressive vasculopathy died, as compared with those without (26% vs. 11%, p = 0.03). Death and MI also occurred more frequently among those with rapid progression than in those without it (51% vs. 16%, p < 0.0001). There was no significant difference in outcome in patients with and without donor-transmitted lesions. Angiographic disease was found in 11 (22%) of 50 patients with and in 2 (2.1%) of 76 patients without (p = 0.003) rapidly progressive vasculopathy. The IVUS-defined rapid progression correlated highly with future development of angiographic disease (p = 0.0005).

CONCLUSIONS

Rapidly progressive vasculopathy by IVUS, defined as an increase of >/=0.5 mm in intimal thickness within the first year after transplantation, is a powerful predictor of all-cause mortality, MI, and angiographic abnormalities. Accordingly, such patients may be candidates for more aggressive anti-atherosclerotic and/or immunosuppressive therapy.

Relative contributions of intimal hyperplasia and vascular remodeling in early cardiac transplant-mediated coronary artery disease

The relative contribution of intimal hyperplasia and vascular remodeling in early transplant coronary artery disease (TxCAD) is unknown. This study was designed to determine the contributions of vascular remodeling and intimal hyperplasia in the initial year after transplantation by intravascular ultrasound (IVUS). Twenty-five patients underwent baseline (<6 weeks after transplant) and 1-year angiography and IVUS to evaluate total vessel, luminal, and intimal + medial areas in >or=3 segments of the coronary artery. Nine patients had donor atherosclerotic disease on baseline study (23% of segments), and at 1-year, 21 patients (84%) had intimal hyperplasia (70% of segments). Fourteen patients had positive remodeling in all arterial segments, whereas the remaining 11 had positive and negative remodeling in the same vessel. Mean plaque area and total vessel area increased significantly (p = 0.0001) in proximal, mid, and distal segments, whereas total vessel area was most pronounced in distal segments. Luminal area did not change over time. Of the 87 segments evaluated, 68 (78%) had an increase in total vessel area, 57 (66%) had intimal growth, and 54 (62%) had an increase in luminal area. Although changes in total vessel and luminal area were closely correlated, a decrease in luminal area was associated with positive and negative remodeling. In conclusion, luminal area is generally maintained during the initial transplant year despite significant intimal hyperplasia due to positive remodeling. Reduction in the luminal area results from either inadequate positive remodeling or negative remodeling without intimal growth and often occurs in the same artery.

Lumen loss in transplant coronary artery disease is a biphasic process involving early intimal thickening and late constrictive remodeling: results from a 5-year serial intravascular ultrasound study

BACKGROUND

Coronary artery disease is the major cause of late cardiac allograft failure. However, few data exist regarding the natural history of changes in intimal and external elastic membrane (EEM) areas after heart transplantation.

METHODS AND RESULTS

In 38 transplant recipients, serial intravascular ultrasound examinations were performed 3.7+/-2.2 weeks after transplantation and annually thereafter for 5 years. In 59 coronary arteries, we compared 135 matched segments among serial studies. In each segment, intravascular ultrasound images were digitized at 1-mm intervals, and mean values of EEM and lumen and intimal areas were analyzed. In the first year after transplantation, the intimal area increased significantly from 1.8+/-1.6 to 3.0+/-2.1 mm(2) (P<0.001). Subsequently, the annual increase in intimal area decreased. EEM area did not change during the first year; however, between years 1 and 3, significant expansion of EEM area occurred (15.4+/-4.6 to 17.2+/-5.4 mm(2), P<0.001). Thereafter, EEM area decreased significantly from 17.2+/-5.4 mm(2) (year 3) to 15.1+/-4.9 mm(2) (year 5, P=0.01). Different mechanisms of lumen loss were observed during 2 phases after transplantation: early lumen loss primarily caused by intimal thickening and late lumen loss caused by EEM area constriction.

CONCLUSIONS

This serial ultrasound study revealed that most of the intimal thickening occurred during the first year after heart transplantation. Changes in the EEM area showed a biphasic response, consisting of early expansion and late constriction. Thus, different mechanisms of lumen loss were observed during the early and late phases after transplantation.

Evaluation of regional wall motion and quantitative measures of ventricular function during dobutamine stress echocardiography in pediatric cardiac transplantation patients

BACKGROUND

Graft coronary disease is a leading cause of death in patients who have undergone cardiac transplantation. The purpose of this study was to evaluate regional wall motion response and quantitative measures of ventricular function during dobutamine stress echocardiography (DSE) in pediatric transplantation patients.

METHODS

Eleven patients were evaluated the first year after transplantation (10/11 no rejection). Ten of the 11 were reevaluated 1.2 +/- 0.3 years later (9/10 no rejection).

RESULTS

Dobutamine stress echocardiography revealed the following: (1) baseline regional wall motion abnormalities in 80% that resolved in all, (2) increased heart rate and blood pressure, (3) no change in left ventricular end-diastolic diameter, (4) decreased end-systolic diameter, (5) decreased wall stress and increased velocity of circumferential fiber shortening, (6) increased VCFcZ score (representing systolic left ventricular function), and (7) a decreased mitral passive-to-active filling ratio. Patients with rejection had abnormal VCFcZ scores at rest.

CONCLUSIONS

Pediatric transplantation patients without rejection have baseline regional wall motion abnormalities. With DSE, the following are present: (1) resolution of wall motion abnormalities, (2) increased contractility independent of load, and (3) changes in diastolic parameters that reflect increased heart rate. Patients with rejection may have abnormal contractility at rest.

Electron-beam computed tomography in the assessment of coronary artery disease after heart transplantation

BACKGROUND

Our aim was to compare the electron-beam CT (EBCT) features of coronary arteries in heart transplant recipients with those of biplane coronary angiography and intracoronary ultrasound (ICUS).

METHODS AND RESULTS

We examined 112 heart transplant recipients (25 female; age, 17 to 69 years; median, 52 years) 1 to 153 months (median, 46 months) after surgery by EBCT to detect coronary artery calcifications. Calcifications were quantified by the Agatston scoring system. EBCT scores were compared with coronary angiography in all patients and ICUS of the left anterior descending coronary artery (LAD) in 100 patients. Coronary artery calcifications were found in 84 patients (75%). Angiographically, 16 patients displayed >50% coronary artery stenoses, all of whom had some degree of coronary artery calcification and only 1 of whom had a score of <55 (P<0.0001). With this threshold, EBCT had a sensitivity of 94%, a specificity of 79%, a positive predictive value of 43%, and a negative predictive value of 99% for detecting stenosis. ICUS confirmed the presence of calcified plaques in all patients with an LAD score >9. EBCT total calcium score was associated with the degree of intimal proliferation in that patients without ICUS features of allograft vasculopathy had a median score of 0 (25th percentile, 0; 75th percentile, 0), whereas patients with Stanford class IV vasculopathy had a median score of 41 (9 to 98, P<0.0001).

CONCLUSIONS

EBCT is a promising noninvasive test for the detection of coronary heart disease in cardiac transplant recipients.

Double-helical CT as a new tool for tracking of allograft atherosclerosis in heart transplant recipients

RATIONALE AND OBJECTIVES

Tracking the progression of allograft atherosclerosis in heart transplant recipients is currently accomplished using invasive techniques. If its monitoring feasibility is demonstrated, spiral CT could be a non-invasive alternative for this objective.

METHODS

Twenty-four consecutive heart transplant patients (21 men, 3 women, mean age 55 +/- 11 years) were scanned using double-helical CT. The first scan was performed 1.9 +/- 1.3 years after transplantation. After 2 years of follow-up, 4 patients died and the remaining 20 underwent a second scan. All scans were performed according to a previously reported double-helical CT protocol.

RESULTS

The incidence of coronary calcification at the first scan was 4.2% (1/24); it increased to 40% (8/20) at the second scan (P < 0.001). Spiral CT identified new but very mild calcific deposits in seven patients with a mean total calcium score of 6.7 +/- 4.0.

CONCLUSIONS

Double-helical CT is a viable tool to diagnose and track newly developed allograft atherosclerosis.

Impact of intravascular ultrasound in understanding transplant coronary artery disease

Intravascular ultrasound imaging has been recognized as a sensitive tool to study early transplant vasculopathy lesions. An early examination performed soon after transplantation allows one to study donor atherosclerosis. Further, serial follow-up imaging with meticulous site matching provides important information regarding the progression of donor atherosclerosis and the development of transplant vasculopathy lesions. This review highlights the contribution of intravascular imaging in understanding the transplant coronary artery disease. This review also outlines various methodologies employed by different investigators, and stresses the strengths and weaknesses of these methodologies for correct interpretation as well as comparison of data from different studies.

Relation of donor age and preexisting coronary artery disease on angiography and intracoronary ultrasound to later development of accelerated allograft coronary artery disease

OBJECTIVES

This study assessed the influence of donor age and preexisting donor coronary disease on the later development of allograft coronary artery disease, ischemic events and overall survival.

BACKGROUND

The increasing demand for heart donors has led to a tendency to liberalize age criteria for donor acceptability.

METHODS

A total of 233 consecutive heart transplant recipients who had baseline, early postoperative and follow-up coronary angiograms, as well as a subset of 47 patients with baseline intracoronary ultrasound imaging recordings, were analyzed (mean 3.8 years of follow-up). Patients were subclassified according to the presence of donor coronary artery disease on the baseline angiogram and stratified at age 40 years.

RESULTS

patients without evidence of preexisting coronary artery disease on a baseline angiogram (n = 219) were significantly less likely to develop new disease than the 14 patients with preexisting coronary artery disease (p = 0.002). Although older donors exhibited earlier coronary artery disease than younger donors at 3 years of follow-up, there was no difference by 5 years (p = 0.25). There was no difference in survival or probability of developing ischemic events between the groups. Baseline ultrasound imaging revealed substantial disease in 7 of 9 older donated hearts, and in only 7 of 38 younger donated hearts (p = 0.002). Preexisting coronary artery disease, nonuse of calcium channel blocking agents, older donor age, posttransplantation cytomegalovirus infection, elevated very low density lipoprotein levels and previous ischemic heart disease in the recipient were significant predictors of allograft coronary artery disease.

CONCLUSIONS

Heart donors with angiographic evidence of preexisting coronary artery disease and older donors are more likely to develop new allograft coronary artery disease by 3 years. However, there is no difference in survival or freedom from ischemic events between younger and older donors at a mean follow-up of 3.8 years.

Coronary plaque morphologic characteristics early and late after heart transplantation: in vivo analysis with intravascular ultrasonography

To characterize plaque morphologic characteristics of transplant coronary artery disease early and late after cardiac transplantation, 72 patients were studied with intravascular ultrasonography during routine coronary angiography (group 1, 25 patients < or = 2 months after surgery; group 2, 47 patients > or = 12 months after surgery). Both groups had comparable baseline characteristics. Three hundred fifty-one segments were imaged in 127 coronary arteries (4.9 +/- 1.8 segments per patient). By intravascular ultrasonography, relevant intimal thickening (> 0.3 mm) was found in the majority of patients (68% for group 1 and 72% for group 2). Angiography detected abnormal findings in only 16% and 32% for groups 1 and 2, respectively. Mean intimal index was higher in patients late after transplantation (27% +/- 12% vs 17% +/- 12%, respectively; p < 0.01). Maximal and mean plaque thickness were comparable in both groups, whereas a higher mean plaque circumference was found in group 2 (278 +/- 66 degrees vs 211 +/- 75 degrees, respectively; p < 0.002). The lesions were more eccentric in patients early after transplantation (mean eccentricity index 95% +/- 7% vs 77% +/- 15%, respectively; p < 0.0001). Diffuse, concentric intimal thickening was not a common pattern. Maximal plaque thickness correlated with donor age (r = 0.50, p < 0.0001). Coronary lesions were frequent even early after transplantation, with predominantly eccentric plaque morphologic characteristics indicative of preexisting atherosclerosis. Later after transplantation, a more homogeneous plaque distribution was seen, partly with diffuse concentic intimal thickening. Late transplant coronary artery disease appears to be a combination of preexisting native and acquired immune-mediated coronary artery disease.

Can Tl-201 myocardial SPECT abnormalities in orthotopic heart recipients be explained by coronary vessel wall alterations assessed by intravascular ultrasound?

The aim of this study was to compare findings on coronary intravascular ultrasound and thallium-201 SPECT in patients following orthotopic heart transplantation.

BACKGROUND

No data are available on whether pathological thallium scintigraphic findings in heart recipients are based on coronary vessel wall alterations identifiable by intravascular ultrasound.

METHODS

29 patients (mean age: 50.9 +/- 11.5 years; male n = 23) were investigated by means of intravascular ultrasound of selected coronary segments and thallium-201 myocardial SPECT. Patients were investigated 11.6 +/- 5.4 weeks post transplantation, a subgroup of 13 patients was re-investigated 70.2 +/- 18.4 weeks following transplantation. A total of 214 cross-sectional areas of the left coronary artery were examined using a 3.5 French intravascular ultrasound catheter to measure intimal index and the circumferential extension of a three-layer appearance of the vessel wall. Shortly after catheterisation, an ergometric stress-test was performed to examine all recipients by means of thallium-201 SPECT. In each patient, 20 segments of the left ventricle were evaluated using a score system of differentiate between persistent defects, redistribution, and reverse redistribution. A score was developed that measured the degree of inhomogeneity and severity of perfusion defects, respectively. Findings on scintigraphy were correlated to coronary intravascular ultrasound findings.

RESULTS

At first investigation, mean intimal index of all evaluated coronary cross-sectional areas was 0.06 +/- 0.1. Sixty-four cross-sectional areas demonstrated a three-layer appearance of the vessel wall, mean circumferential extension was 72 +/- 122 degrees. Thallium scintigraphy demonstrated a total of 336 (40%) pathological left ventricular segments; 168 (20%) were regarded as permanent defects, 67 (8%) demonstrated redistribution and 101 (12%) showed reverse redistribution. The score of inhomogeneity was calculated as 5.8% +/- 2.6%. In the subgroup of patients at the follow-up study, the score was 6.4 +/- 2.8%. There was no correlation between intimal index and the score, nor could any correlation be confirmed between the score and the circumferential extension of a three-layer appearance of the vessel wall. At second investigation, no significant differences of intimal index (0.05 +/- 0.07) or circumferential extension of a three-layer appearance of the vessel wall (74 +/- 118 degrees) could be confirmed. The score was slightly, but significantly increased to 8.1 +/- 4.5% at the second investigation (P < 0.05).

CONCLUSION

Early after orthotopic heart transplantation, pathologic thallium distribution patterns of the left ventricle could be observed. These pathological patterns did not correlate with the extent of diffuse coronary vessel wall alterations identifiable by intravascular ultrasound. After more than 1 year, the degree of scintigraphic abnormalities increased significantly, not accompanied by an increase of diffuse coronary vessel wall alterations.

Experimental models of accelerated atherosclerosis syndromes

The processes of angioplasty restenosis, vein graft failure, and transplant atherosclerosis, collectively termed 'syndromes of accelerated atherosclerosis', have been the focus of significant clinical and experimental research. Limitations of clinical studies have forced emphasis onto experimental animal models for the purpose of determining pathophysiology and evaluation of potential therapeutic strategies. However, the apparent failure of many in vivo animal models to predict interventional outcome in humans has raised doubt over their suitability as models of these pathophysiological states. Similar criticism has befallen the use of in vitro techniques for elucidating pathophysiology of the cellular elements. An awareness of the shortcomings of the various experimental models in use would therefore seem prerequisite both to a more critical evaluation of data generated from their use, and to the development of truly effective therapeutic strategies for humans.

Are heart-lung transplant recipients protected from developing transplant coronary artery disease? A case-matched intracoronary ultrasound study

BACKGROUND

Accelerated coronary artery disease is a major cause of mortality in heart transplant recipients; however, it does not appear to play a major role in the clinical outcome of heart-lung transplant recipients. The purpose of this study was to determine whether the incidence and severity of transplant coronary artery disease as detected by intracoronary ultrasound in heart-lung transplant recipients are less than those encountered in heart transplant recipients.

METHODS AND RESULTS

We studied the left anterior descending coronary artery with the use of intracoronary ultrasound imaging in 22 heart-lung transplant recipients at the time of their routine annual coronary angiogram. Twenty-two heart transplant recipients were case matched for number of years after transplant at ultrasound study, recipient age, donor age, and diagnosis of nonischemic cardiomyopathy. Mean intimal area, intimal index, Stanford class, and incidence of at least moderate disease (Stanford class > or = 3) were measured and calculated in each group and then compared between the two groups. Mean intimal area (1.6 +/- 2.5 versus 3.8 +/- 2.8 mm2), mean intimal index (0.07 +/- 0.10 versus 0.22 +/- 0.14), mean Stanford class (1.7 +/- 1.0 versus 2.7 +/- 1.2), and incidence of Stanford class > or = 3 (14% versus 45%) were significantly lower in the heart-lung transplant recipient group.

CONCLUSIONS

The incidence and severity of transplant coronary artery disease are much less in patients receiving heart-lung transplants than in those receiving heart transplants alone.

Dobutamine stress echocardiography for noninvasive diagnosis of cardiac allograft vasculopathy: a comparison with angiography and intravascular ultrasound

This study was performed to assess the value of dobutamine stress echocardiography for noninvasive diagnosis of cardiac allograft vasculopathy (CAV) compared with coronary angiography and intravascular ultrasound (IVUS) in 50 consecutive orthotopic heart transplant recipients. In 46 of 50 patients, a technically adequate echocardiogram could be obtained. Using a 16-segment model, a total of 675 segments were analyzed. At rest, wall motion abnormalities were found in 61 of 675 (9.0%) left ventricular segments in 15 of 46 patients. At maximal dobutamine stress, 103 of 675 segments (15.3%) had wall motion abnormalities (25 of 46 patients). Based on IVUS and angiographic findings, patients were allocated to 2 groups. Group I (n=18) had absent or only mild intimal hyperplasia (mean IVUS grade < or = 3.0 on a 6-grade scale). Group II (n=28) had moderate to severe intimal hyperplasia (mean grade > 3.0 with or without angiographic evidence of CAV. The prevalence of wall motion abnormalities was significantly higher in group II than in group I, both at rest (50 of 415 vs 11 of 270 coronary segments in 13 of 28 vs 2 of 18 patients) and during maximal stress (88 of 415 vs 15 of 270 coronary segments in 22 of 28 vs 3 of 18 patients). Quantitative M-mode echocardiography demonstrated decreased wall thickening in group II versus group I patients at maximal dobutamine dosage in the septum (48 +/- 18% vs 61 +/- 17%; p < 0.01) as well as in the left ventricular posterior wall (77 +/- 21% vs 96 +/- 21%; p <0.005). Regional myocardial dysfunction as assessed by dobutamine stress echocardiography was associated with IVUS evidence of moderate to severe intimal hyperplasia. Dobutamine stress echocardiography appears to be a feasible noninvasive method for detection of CAV in heart transplant recipients, which may reduce the need for routine coronary angiography.

Exercise echocardiography, angiography, and intracoronary ultrasound after cardiac transplantation

Fifty-one consecutive patients underwent exercise echocardiography, angiography, and intracoronary ultrasound (ICUS) 2.5 years (range from 1 to 6) after cardiac transplantation. The average age of the donor was 29 years (range 13 to 50), and the average age of the recipient was 49 +/- 12 years. In total, 78 studies were performed, as 25 patients had >1 annual evaluation and 2 patients had 3 consecutive annual evaluations. Of the 78 angiographic studies, 40 (26 patients) had evidence of coronary artery disease, defined as a focal stenosis (>20%, n=4) or luminal irregularities (n=36). However, by ICUS all 51 patients had intimal thickening at some point, with 34 patients possessing diffuse disease and 17 focal intimal thickening only. Of the 25 serial studies, 12 progressed by at least 1 Stanford class. The sensitivity of angiography for determination of class III to IV intimal thickening was 64% and the specificity was 76%. On exercise echocardiography, 6 examinations revealed resting wall motions abnormalities, whereas 6 had inducible wall motion abnormalities with exercise. The sensitivity of exercise echocardiography to determine class III to IV intimal thickening was 15%, and the specificity was 85%. In conclusion, exercise echocardiography is an insensitive method for predicting transplant-mediated coronary artery disease, whereas luminal irregularities on angiography may predict the presence of Stanford grade III to IV intimal thickening.

Dichotomous pattern of coronary atherosclerosis 1 to 9 years after transplantation: insights from systematic intravascular ultrasound imaging

OBJECTIVE

The aim of this study was to evaluate the extent and distribution of coronary atherosclerosis after transplantation.

BACKGROUND

Transplant coronary artery disease is an important cause of death after cardiac transplantation. Unlike coronary angiography, intravascular ultrasound is a sensitive tool for detection and quantitation of this disease.

METHODS

We performed intravascular ultrasound imaging in 132 (106 men, 50 +/- 10 years) patients, 1 to 9 years after transplantation using a 30-MHz ultrasound catheter.

RESULTS

All three coronary arteries were visualized in 49, two in 62 and one in 21 patients. Of the 1,188 coronary artery segments, 706 were imaged (74% proximal, 64% mid- and 40% distal). At least one site with atherosclerosis (intimal thickness > or = to 0.5 mm) was found in 83% of patients. Atherosclerosis was noted in 64% of proximal, 43% of mid- and 26% of distal segments. Disease was diffuse in 48% and focal in 52%, circumferential in 66% and noncircumferential in 34%. Focal atherosclerosis was more common in proximal (59%) than mid- (48%) and distal segments (27%) (p=0.001). Noncircumferential plaques were more common in the proximal (42%) than mid- (28%) and distal segments (12%) (p=0.001). This pattern of focal and noncircumferential disease proximally, diffuse and circumferential disease distally, was observed irrespective of the time from transplantation.

CONCLUSION

Atherosclerosis was detected in more than 80% of patients, with proximal segments most frequently involved. Diffuse and circumferential atherosclerosis was more common in mid- and distal segments. However, focal and noncircumferential involvement was more frequent proximally, a similar pattern to native atherosclerosis. These findings suggest that transplant coronary artery disease has a dual etiology based on the dichotomous pattern of atherosclerosis seen by intravascular ultrasound.

Adult Cardiac Transplantation

Patients with severe drug-refractory heart failure experience one of two modes of death. Either they collapse from an arrhythmia and are deemed to have had sudden death, or they die of progressive congestive heart failure. In either instance, their poor functional status during life limits their ability to perform usual daily activities. Currently, the only proven long-term benefit to these patients is heart transplantation. The technique that led to the first human-to-human heart transplantation nearly 30 years ago has changed very little; however, refinements in post operative care have kept research in this field at the fore for many years. Immediate postoperative hemodynamic stabilization by experienced clinicians may improve a patient's chances of survival after heart transplantation. Improved immunosuppressive agents have decreased life-threatening rejection episodes. Better knowledge of the infectious diseases that attack these immunosuppressed patients has also contributed to the nearly 85% one-year survival of heart transplantation recipients. The longest surviving heart transplantation recipient remains alive and well after more than 22 years. The development of transplant-related coronary artery disease may be the only transplantation-associated factor that keeps recipients from living for many decades. Transplantation coronary artery disease leads the list of late causes of mortality. Unlike native coronary artery disease, there exists ongoing difficulty in both diagnosis and treatment of this dreaded complication. We cover current standards and future possibilities in adult heart transplantation. We look at history, demographics, indications, management, and outcome in these patients, as well as future goals.

Prognostic importance of intimal thickness as measured by intracoronary ultrasound after cardiac transplantation

BACKGROUND

Although intracoronary ultrasound (ICUS) has been validated for the early detection of transplant coronary artery disease (TxCAD), the prognostic importance of findings detected by this new imaging technique is unknown.

METHODS AND RESULTS

This study examined the relation of clinical outcome in 145 heart transplant recipients (mean age, 45.1 +/- 11.1 years) with the amount of intimal thickness measured by ICUS during routine annual coronary angiography 1 to 10 years (mean, 3.1 +/- 2.2 years) after transplantation. From published autopsy data, a mean intimal thickness of > 0.3 mm was considered significant. During a mean follow-up time of 48.2 +/- 10.2 months, 23 deaths (12 cardiac) occurred, and 6 patients required retransplantation. Angiographic TxCAD developed in 22 of 125 patients (17.6%) in the subgroup with normal angiograms at the time of ICUS and a follow-up annual angiographic study. In the total population and the subgroup, mean intimal thicknesses of > 0.3 and < or = 0.3 mm, respectively, were associated with significantly inferior 4-year actuarial overall survival (73% versus 96%, P = .005; 72% versus 92%, P = .05), cardiac survival (79% versus 96%, P = .005; 80% versus 98%, P = .04), and freedom from cardiac death and retransplantation (74% versus 98%, P < .0001; 70% versus 96%, P = .001). In addition, ICUS predicted freedom from development of subsequent angiographic TxCAD in the subgroup that was initially normal (26% versus 72%, P = .02). A mean intimal thickness by ICUS of > 0.3 mm was associated with inferior clinical outcome regardless of the presence of angiographic TxCAD and predicted the development of subsequent angiographic TxCAD. Despite significantly longer duration after transplantation, higher rejection incidence, and lower average daily cyclosporine dose, none of these covariates were independent risk factors for outcome.

CONCLUSIONS

These findings confirm the prognostic importance of mean intimal thickening of > 0.3 mm in heart transplant recipients and suggest that these patients should be candidates for early interventional strategies.

Influence of preexistent donor coronary artery disease on the progression of transplant vasculopathy. An intravascular ultrasound study

BACKGROUND

Transplant vasculopathy (TxCAD) limits longterm survival of allograft recipients. The possibility that preexistent donor coronary disease (PEDD) might accelerate this process is of concern. The serial progression of sites with and without PEDD as assessed by intravascular ultrasonic imaging is explored in this study.

METHODS AND RESULTS

Thirty patients with baseline intravascular imaging within 3 weeks of cardiac transplantation who had at least one annual follow-up study were included in this study. Vessel luminal area (LA), total area (TA), intimal index (II = TA - LA/TA), mean intimal thickness (MIT), and Stanford classification were expressed for each image site and for each patient at each study. Progression of sites and of patients with and without PEDD on the baseline study was compared. Patients with PEDD (n = 9) still had significantly more intimal disease than those without PEDD (n = 21) at the first follow-up study (MIT = 0.35 +/- 0.13 versus 0.13 +/- 0.11 mm; II = 0.29 +/- 0.11 versus 0.11 +/- 0.1; class = 3.7 +/- 0.5 versus 2.2 +/- 0.94; P < .001 for all comparisons). However, the increase in intimal thickness during the 1- year interval was not significantly different between the two groups. In 4 patients in whom both types of sites were present, no difference in progression was found. Data were similar for patients and sites studied over > 1 year.

CONCLUSIONS

PEDD does not accelerate the progression of TxCAD within the first few years after cardiac transplantation. The pathophysiology of TxCAD is most likely immune mediated and does not seem to be accelerated by native coronary artery disease.

Correlation of donor characteristics with transplant coronary artery disease as assessed by intracoronary ultrasound and coronary angiography

The mechanisms responsible for transplant coronary artery disease (CAD) and its predisposing factors remain incompletely understood. The influence of donor characteristics as predisposing factors has not been studied systematically. We examined the correlation of donor demographic, clinical, and immunologic parameters with transplant CAD assessed by both intracoronary ultrasound (ICUS) and coronary angiography in 116 heart transplant recipients (age 44.7 +/- 12.0 years) studied 3.4 years (range 1.0 to 14.6) after transplantation. Quantitative ultrasound data were obtained by calculating mean intimal thickness from several distinct coronary sites. Coronary angiograms were categorized visually as normal or showing any transplant CAD. By multivariate regression analysis, donor undersize of > 20% of recipient weight (p < 0.02) and duration after transplantation (p < 0.005) were independently correlated with the amount of ICUS intimal thickness (r = 0.36, p = 0.0007), and older donor age with angiographic evidence for the disease (r = 0.34, p < 0.006). In a subgroup analysis of the 39 patients studied 1 year after transplantation, white donor race (p < 0.05), fewer human leukocyte antigen-DR mismatches (p < 0.002), shorter ischemic time (p < 0.04), and donor smoking history (p < 0.02) were independent predictors for severity of ICUS intimal thickening (r = 0.92, p = 0.0009); higher donor age (p < 0.006) and higher arterial partial pressure of oxygen (p < 0.003) were independent predictors for angiographic disease (r = 0.67, p < 0.002). In conclusion, donor characteristics may contribute to the probably multifactorial pathogenesis of transplant CAD.

Coronary angioplasty, atherectomy and bypass surgery in cardiac transplant recipients

OBJECTIVES

This study sought to analyze the outcomes of revascularization procedures in the treatment of allograft coronary disease.

BACKGROUND

Allograft vasculopathy is the main factor limiting survival of heart transplant recipients. Because no medical therapy prevents allograft atherosclerosis, and retransplantation is associated with suboptimal allograft survival, palliative coronary revascularization has been attempted.

METHODS

Thirteen medical centers retrospectively analyzed their complete experience with percutaneous transluminal coronary angioplasty, directional coronary atherectomy and coronary bypass graft surgery in allograft coronary disease.

RESULTS

Sixty-six patients underwent coronary angioplasty. Angiographic success (< or = 50% residual stenosis) occurred in 153 (94%) of 162 lesions. Forty patients (61%) are alive without retransplantation at 19 +/- 14 (mean +/- SD) months after angioplasty. The consequences of failed revascularization were severe. Two patients sustained periprocedural myocardial infarction and died. Angiographic restenosis occurred in 42 (55%) of 76 lesions at 8 +/- 5 months after angioplasty. Angiographic distal arteriopathy adversely affected allograft survival. Eleven patients underwent directional coronary atherectomy. Angiographic success occurred in 9 (82%) of 11 lesions. Two periprocedural deaths occurred. Nine patients are alive without transplantation at 7 +/- 4 months after atherectomy. Bypass graft surgery was performed in 12 patients. Four patients died perioperatively. Seven patients are alive without retransplantation at 9 +/- 7 months after operation.

CONCLUSIONS

Coronary revascularization may be an effective palliative therapy in suitable cardiac transplant recipients. Angioplasty has an acceptable survival in patients without angiographic distal arteriopathy. Because few patients underwent atherectomy and coronary bypass surgery, assessment of these procedures is limited. Angiographic distal arteriopathy is associated with decreased allograft survival in patients requiring revascularization.

Intracoronary ultrasound: current state of the art

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Angiographic, intravascular ultrasound and functional findings early after orthotopic heart transplantation

Accelerated graft atherosclerosis is responsible for increased mortality and morbidity among heart transplant recipients. The aim of this in-vivo study was to evaluate coronary atherosclerotic vessel alterations and endothelial function. Seventeen patients (14 males; mean age 49.3 years; range 24 to 69) were studied an average of 11 weeks (range 5 to 21) after heart transplantation because of coronary artery disease (n = 8), dilative cardiomyopathy (n = 7), mitral valve replacement (n = 1) and left atrial metastases of a leiomyosarcoma (n = 1). Mean age of the donor hearts (9 males) was 29 years (range 12 to 55). All recipients underwent biplane ventriculography and coronary angiography. In this study population, a total of 120 coronary segments (main stem, 21; left anterior descending artery, 85; circumflex artery, 14) were analyzed by intravascular ultrasound (20 MHz, 3.5F). In 13 patients, acetylcholine was infused into the proximal left anterior descending artery (10(-8) to 10(-5) M) to evaluate vasomotion within this segment. Regional contraction abnormalities were documented in 2 patients. Nine segments angiographically showed non-critical stenoses (5 patients). Intravascular ultrasound detected 52 cross-sectional areas with a three-layer pattern indicating intimal thickening. Mean circumferential extension of intimal proliferation was 192 degrees, mean intimal thickness 0.35 mm. Only 5 segments of the sonographically pathological cross-sectional areas showed angiographical evidence of atherosclerotic lesions. Intracoronary administration of acetylcholine at doses of 10(-8) and 10(-7) M resulted in vasoconstriction of the examined coronary segment in only 2 patients; the intracoronary application of acetylcholine at doses of 10(-6) and 10(-5) M revealed coronary vasoconstriction in 10 of the total of 13 patients. Using intravascular ultrasound, coronary artery lesions in heart transplant recipients can already be depicted at a very early stage. The abnormal response to acetylcholine in most of the heart recipients is independent of the extent of atherosclerotic vessel abnormalities documented by ultrasound or angiography.

Occult and frequent transmission of atherosclerotic coronary disease with cardiac transplantation. Insights from intravascular ultrasound

BACKGROUND

Transplant coronary artery disease is a major cause of morbidity and mortality after cardiac transplantation. However, limited data exist regarding the potential contribution of coronary atherosclerosis in the donor heart to cardiac-allograft vasculopathy.

METHODS AND RESULTS

We performed quantitative coronary angiography and intravascular ultrasound imaging in 50 of 62 consecutive heart-transplant recipients (40 men, 10 women, mean age, 53 +/- 9 years) 4.6 +/- 2.6 weeks after transplantation. The donor population consisted of 30 men and 20 women (mean age, 32 +/- 12 years). Ultrasound imaging visualized all three coronary arteries in 22 patients, two coronary arteries in 23, and one coronary artery in 5. Ultrasound imaging detected coronary atherosclerosis (intimal thickness > or = 0.5 mm) in 28 patients (56%). However, the angiography was abnormal in only 13 patients (26%). The sensitivity and specificity of coronary angiography were 43% and 95%, respectively. With ultrasound, the average atherosclerotic plaque thickness was 1.3 +/- 0.6 mm and the cross-sectional area narrowing was 34 +/- 16%. Atherosclerotic involvement frequently was focal (85%), eccentric (mean eccentricity index, 87 +/- 8), and near arterial bifurcations. Donors of the transplant recipients with coronary atherosclerosis were older than those without atherosclerosis (37 +/- 12 versus 25 +/- 10 years, P = .001). Maximal intimal thickness correlated with donor age (r = .54, P = .0001). Multivariate analysis demonstrated that donor age (P = .0001), male sex of donor (P = .0006), and recipient age (P = .03) were independent predictors of atherosclerosis.

CONCLUSIONS

Coronary atherosclerosis is frequently but inadvertently transmitted by means of cardiac transplantation from the donor to the recipient. Long-term outcomes of donor-transmitted coronary artery disease will require further evaluation.

Incidence and severity of transplant coronary artery disease early and up to 15 years after transplantation as detected by intravascular ultrasound

OBJECTIVES

The purpose of this study was to quantify the severity of transplant coronary artery disease and to assess lesion characteristics early and up to 15 years after heart transplantation by using intracoronary ultrasound.

BACKGROUND

Intravascular ultrasound has the ability to measure the components of the arterial wall and has been shown to be a sensitive method for detection of transplant coronary artery disease.

METHODS

A total of 304 intracoronary ultrasound studies were performed in 174 heart transplant recipients at baseline and up to 15 (mean 3.3 +/- 0.2) years after transplantation. Mean intimal thickness and an intimal index were calculated, and lesion characteristics (eccentricity, calcification) were assessed for all coronary sites imaged (mean 3.0 +/- 0.1 sites/study). The Stanford classification was used to grade lesion severity.

RESULTS

Compared with findings in patients studied at baseline (< 2 months after transplantation, n = 50), mean intimal thickness (0.09 +/- 0.02 vs. 0.16 +/- 0.02 mm, p < 0.01), intimal index (0.07 +/- 0.01 vs. 0.14 +/- 0.02, p < 0.01) and mean severity class (1.5 +/- 0.2 vs. 2.3 +/- 0.2, p < 0.01) were significantly higher at year 1 (n = 52) after transplantation. Thereafter, all three variables further increased over time and reached highest values between years 5 and 15. Calcification of lesions was detected in 2% to 12% of studies up to 5 years after transplantation, with a significant increase to 24% at years 6 to 10 (p < 0.05).

CONCLUSIONS

Severity of transplant coronary artery disease appeared to progress with time after transplantation in this cross-sectional study. This characteristic was most prominent during the 1st 2 years after transplantation, whereas calcification of plaques occurred to a significant extent only later in the process. These data may serve as a reference for comparison of intravascular ultrasound findings in other studies of patients with transplant coronary artery disease.