(RTMPE for CAV) Real Time Myocardial Perfusion Echocardiography for Detection of Coronary Allograft Vasculopathy in Cardiac Transplant Patients
Phase: PHASE4
Conditions: Cardiac Allograft Vasculopathy
Sponsor: Mayo Clinic

 
 
(RTMPE for CAV) Real Time 
Myocardial Perfusion 
Echocardiography for Detection 
of Coronary Allograft 
Vasculopathy in Cardiac 
Transplant Patients 
 
NCT# 02880137 
 
August 4, 2017 

 
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(RTMPE for CAV) Real Time Myocardial Perfusion 
Echocardiography for Detection of Coronary Allograft 
Vasculopathy in Cardiac Transplant Patients 
 
 
 
Principal Investigator: Jonathan Johnson, M.D. 
 
 
 
 
 

 
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INTRODUCTION & BACKGROUND 
 
Cardiac allograft vasculopathy (CAV) is an important cause of morbidity and mortality among 
pediatric and adult transplant recipients.(13-15) Due to the often asymptomatic nature of disease 
progression serial surveillance is recommended for all cardiac transplant recipients, however 
current techniques are either invasive and/or lack sensitivity to detect early stages of CAV due to 
its significant effect on coronary microvasculature. Real time myocardial perfusion 
echocardiography (RTMPE) is a safe and feasible non-invasive technique commonly used to 
diagnose coronary disease, and offers an attractive alternative for CAV detection. 
 
The incidence of CAV is approximately 10% at 1 year post-transplant, 30% at 5 years and 50% 
at 10 years, and it has become one of the leading causes of graft loss and death after the first 
year.(13) CAV is a diffuse and accelerated fibro-proliferative process that affects both the large 
epicardial and small intramyocardial allograft coronary arteries (Figure 1).(16) Early detection of 
CAV is critically important because it allows alterations to medical therapy to slow progression 
before revascularization is required. Early detection is challenged by the often asymptomatic 
nature of disease progression, making routine CAV screening the current standard of care for 
transplant recipients. Invasive coronary angiographic (ICA) imaging is the gold standard for the 
detection of CAV, but is invasive (and may require a general anesthetic in the pediatric 
population) and exposes the patient to ionizing radiation, while current noninvasive methods best 
evaluate the large vessels with limitations for the detection of small vessel disease. 
 
The objectives of this study are to determine the feasibility and diagnostic accuracy of RTMPE 
to detect CAV in pediatric and adult transplant recipients. We hypothesize that RTMPE is an 
effective non-invasive method for CAV detection in these populations, and that perfusion 
deficits will correlate with significant coronary artery stenosis identified by standard stress 
echocardiography and invasive angiography.  
 
Real-time myocardial perfusion echocardiography (RTMPE) may offer an attractive alternative 
to ICA for the detection of CAV.(17-20) RTMPE utilizes the intravenous administration of 
biologically-inert microbubbles to assess myocardial perfusion,(6) and has demonstrated utility 
for identifying small vessel coronary artery disease.(7) Although contrast echocardiography has 
found common application for evaluation of coronary artery disease in adult non-transplant 
recipients,(6) this safe and potentially useful imaging modality remains understudied in CAV 
with only two small single center studies published in the current literature (Figure 2).(21,22) 
The contrast medium administered in RTMPE is routinely used without significant side effects in 
adults (8,23,24) and has been studied in pediatric populations with no adverse effects.(12) The 
purpose of this study is to evaluate the feasibility and diagnostic utility of RTMPE for the 
detection of CAV in adult and pediatric transplant recipients from a multicenter experience 
 

 
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Cardiac transplant recipients followed at Mayo Clinic (Rochester, MN) will be included. The 
study population will be divided into adult and pediatric subgroups. Consenting patients will 
undergo rest and pharmacologic stress perfusion RTMPE. Results of RTMPE will be correlated 
with wall motion assessment by standard stress echocardiography and clinically indicated 
invasive coronary angiography (including intravascular ultrasound findings when available). We 
expect that RTMPE will be well tolerated and findings of myocardial perfusions defects will 
correlate with current CAV surveillance techniques. RTMPE may represent a preferred method 
and new clinical standard for CAV surveillance among adult and pediatric cardiac transplant 
recipients.  
 
 
 
Figure 1. Marked concentric intimal hyperplasia and proliferation associated with cardiac allograft 
vasculopathy. Pollack et al, JACC CV Img 2013. 
 

 
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Figure 2. Myocardial contrast echocardiography from the apical 4-chamber view demonstrating an 
apical and lateral wall perfusion defect (arrows) during peak dobutamine stress (right) compared with 
normal perfusion at rest (left). Rodriguez et al, JASE 2005. 
 
 
OBJECTIVES  
 
• To determine the feasibility of real time myocardial perfusion echocardiography 
(RTMPE) for the detection of coronary allograft vasculopathy (CAV) in pediatric and 
adult cardiac transplant recipients.  
• To determine the diagnostic accuracy of RTMPE for the detection of CAV in pediatric 
and adult cardiac transplant recipients compared with current standardized methods. 
 
 
HYPOTHESIS  
 
RTMPE is a feasible and effective non-invasive method to detect significant CAV in pediatric 
and adult cardiac transplant recipients. Perfusion deficits will correlate with significant coronary 
artery stenosis identified by standard stress echocardiography and ICA, and may identify diffuse 
small vessel disease more effectively than current noninvasive techniques.  
 
 
STUDY DESIGN  
 
This will be a prospective, observational cohort study. The study population will be divided into 
adult (age ≥18 years-old) and pediatric (age <18 years-old) subgroups, each with a separate 

 
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recruitment process and data analysis. Eligible subjects will be screened and recruited through 
the Transplant Clinic. Consenting patients will undergo rest and dobutamine stress RTMPE at in 
the echocardiography laboratory using a standardized imaging protocol.(8) Relevant clinical data 
will be collected from the electronic medical records.  
 
Dobutamine stress echocardiograms will be performed per institutional protocol. 
 
For adults, standard dosing of DEFINITY® (Perflutren Lipid Microsphere) Injectible 
Suspension ultrasound contrast agent will be used.  For each adult, the vial of DEFINITY® 
contrast will be divided in half (~0.75 mL) and drawn up into two 30 mL syringes pre-filled with 
29.25 mL of normal saline. Hand injections of the solution will be performed at baseline, pre-
peak, and peak perfusion stages. 
 
For pediatric patients > 60 kg, the standard adult dosing will be used. For pediatric patients under 
60 kg, the dose will be 20 microL/kg diluted to the same concentration used in the adult dosing. 
Hand injections will be performed at baseline, pre-peak, and peak perfusion stages.  
 
 
INCLUSION CRITERIA 
• Cardiac transplant recipients (≥10 months post transplant)  
• Clinically followed at Mayo Clinic (Rochester MN)  
 
 
EXCLUSION CRITERIA 
• Standard contraindications to the use of ultrasound contrast and pharmacologic stress 
(6,25)  
• Recent (<3 months) hospitalization for heart failure, acute coronary syndrome or allograft 
rejection 
• Multi-organ transplant  
• Known or suspected right-to-left, bi-directional or transient right-to-left cardiac shunts 
• Hypersensitivity to perflutren 
  
 
ENDPOINTS  
 
The primary study endpoint will be presence of a perfusion defect by RTPME. Results of 
RTMPE will be correlated with wall motion assessment by standard stress echocardiography 
(available at the time of RTMPE) and with clinically indicated ICA (including intravascular 
ultrasound findings when available) performed within 3 months of RTMPE. Pediatric cardiac 
transplant recipients at Mayo Clinic undergo annual or bi-annual surveillance ICA, while adult 

 
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cardiac transplant recipients at Mayo Clinic undergo annual surveillance ICA. Grading of ICA 
(13) and RTMPE (8) will be performed independently by two experienced reviewers in a blinded 
fashion. Safety and adverse event data for RTMPE will be collected.  
 
 
SAMPLE SIZE & DATA ANALYSIS  
 
 
A conservative estimated disease prevalence of 25% among adult transplant recipient and 10% 
among pediatric transplant recipients is anticipated.(13) For both pediatric and adult patients 
there are no prior large population studies for estimated diagnostic accuracy of RTMPE for 
detection of CAV, and so sample size estimates are challenging. A target of 25 adult and 25 
pediatric patients for appropriate pilot data will be used. Data will be expressed as the mean ± 
standard deviation for continuous variables, and as absolute frequencies or relative percentages 
for categorical variables. Comparison between groups (with and without CAV by ICA) for 
continuous variables will be done using analysis of variance, and for categorical variables using 
χ2 analysis. Comparison of RTMPE with wall motion stress echocardiography and with ICA will 
be performed using 2x2 contingency tables on a per patient and per coronary artery territory 
perfusion defect distribution basis. All comparisons of diagnostic accuracy will be made on the 
basis of binary outcome data analysis of paired within patient data. All p-values will be 2-sided, 
and a value of ≤ 0.05 will be considered statistically significant. Data analysis will be performed 
using statistical software. 
 
Safety Statement:  RTMPE utilizes the intravenous administration of chemically- and 
biologically-inert microbubbles to assess myocardial perfusion, and may demonstrate improved 
detection of small vessel disease. The ultrasound microbubble contrast medium used in RTMPE 
is routinely used without significant side effects in adults for other indications.  It has been used 
in children on a case-by-case basis with no recognized safety issues unique to children.  
However, for the purposes of this study (perfusion), it would be considered off-label for both 
adults and children.  
 
 
IMPACT AND FUTURE RESEARCH PLANS AND KNOWLEDGE 
TRANSLATION  
 
This project in pediatric and adult transplant recipients will provide pilot data to support the 
development of a larger multicenter study designed to compare the utility of a serial RTMPE 
strategy for CAV surveillance compared with current standard of care of either ICA or alternate 
stress imaging modality. Such a study would be longitudinal in nature and have the ability to 
track changes in RTMPE over time, in addition to comparing sensitivities with alternate CAV 
surveillance strategies. Such research could lead to important potential knowledge translation 

 
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regarding the progression of perfusion deficits mediated by small vessel CAV that are 
asymptomatic and difficult to detect by alternate imaging modalities, improving understanding of 
both risk factors for CAV progression and appropriate tailoring of noninvasive surveillance 
strategies.  
 
PROJECT ASSETS 
 
The study team is highly qualified for this project (see RECENT RELEVANT RESEARCH & 
EXPERIENCE section).  The team includes international experts in the use of contrast 
echocardiography, RTMPE, as well as the medical directors of the pediatric and adult heart 
transplant programs and echo labs.  The contrast agent will be supplied by industry.     
 
 
 
RECENT RELEVANT RESEARCH & EXPERIENCE 
 
Our research group has extensive research experience in fields of cardiac transplant medicine 
and CAV, as well as RTPME. 
 
Dr. Sharon Mulvagh is an echocardiologist at the Mayo Clinic and widely recognized as an 
international leader in the field of contrast echocardiography, and has extensively published 
research in the field of RTMPE.(6-8)  
 
Dr. Sudhir Kushwaha is the Medical Director of the adult Cardiac Transplant Program at Mayo 
Clinic with extensive research in the field of CAV.(9-11)  
 
Dr. Benjamin Eidem is a pediatric cardiologist at Mayo Clinic and widely recognized as an 
international leader in the fields of pediatric cardiology and echocardiology, including the use of 
ultrasound contrast in pediatric patients.(12)  
 
Dr. Jonathan Johnson is a pediatric transplant cardiologist at Mayo Clinic with extensive 
research in this field.(11) 
Dr. Runqing Huang is a PhD research assistant with extensive experience in the use of contrast 
agents in ultrasound imaging.  
 
 
 
 
 
 
 

 
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LAY ABSTRACT  
Heart transplantation is a life prolonging treatment for patients with severe heart failure. Heart 
transplant recipients are susceptible to developing a unique disease that causes blockages in the 
arteries of the transplanted heart (coronary arteries) called coronary allograft vasculopathy 
(CAV). Because CAV often progresses without symptoms, transplant recipients undergo regular 
surveillance testing so that CAV can be detected and treatment offered before significant damage 
to the transplanted heart occurs. Current tests used to detect CAV are either invasive (with risk of 
complications) or may not be able to detect CAV in its early stages. Myocardial contrast 
perfusion echocardiography is a safe noninvasive diagnostic test that may be well suited for 
detecting CAV, however has not been well studied in heart transplant recipients. This study will 
examine the ability of myocardial contrast perfusion echocardiography to detect CAV in adult 
and pediatric heart transplant recipients, and compare those results to current standard testing 
strategies such as invasive coronary angiography and standard stress echocardiography. This will 
help to determine whether myocardial contrast perfusion echocardiography is a better test for 
regular surveillance of CAV for adult and pediatric transplant recipients.