The IMR-HT study is a multicenter, prospective observational study that will include
post-HT stable patients undergoing coronary physiological assessment in the first three
months and one year.
Assessment of IMR, coronary flow reserve (CFR) and fractional flow reserve (FFR) will be
performed using the standard thermodilution technique. The left anterior descending
coronary artery will be evaluated in all patients. Circumflex or right coronary artery
could be additionally evaluated at operator's discretion. An intracoronary pressure and
temperature sensor-tipped guidewire (Pressure Wire TM X guide- wire 0.014', Abbott, IL,
USA) will be used to perform the measurements. The tip pressure sensor will be advanced
into the mid-to-distal portion of the evaluated vessel. Baseline aortic pressure (Pa) and
distal intracoronary pressure (Pd) will be obtained to calculate the resting index Pd/Pa.
To measure the mean transit time (Tmn) under basal conditions, intracoronary
administration of 3 mL of room-temperature saline will be manually injected three times
in succession (3 mL/s). Then maximal hyperemia will be induced using adenosine iv (140 to
180 mg/kg/min) and three additional intracoronary room temperature saline boluses of 3 ml
will be administered to determine the mean transit time at hyperemia (Tmnh). Finally,
fractional flow reserve (FFR), coronary flow reserve (CFR) and IMR will be calculated
using the software Coroventis Coroflow (Coroventis Abbott, Uppsala, Sweden).
Changes in HT patient management (number of EMBs, immunosuppressive therapy
modifications) after knowing IMR values will also be assessed.
Based on previously published clinical data on IMR in heart transplant patients, a
post-HT management algorithm is proposed:
IMR < 15: The frequency of biopsies could be reduced or maintained as per protocol.
No changes to immunosuppressive therapy would be required.
IMR ≥ 15: Biopsies would be performed at the standard frequency according to
protocol. Immunosuppressive therapy could be intensified or maintained the same.
Of note, given the observational characteristics of the study, clinical management
decisions will be made at the discretion of the treating physician, taking into account
the patient's clinical condition and other complementary tests.
Both groups (IMR<15 vs IMR≥15) will be compared in terms of cardiac events occurrence.
Clinical conditions, laboratory findings and clinical events will be assessed at one
month and one year. Follow up will be extended for up to five years. Data will be
included in an online database specifically designed for the study on platform REDCap
(Research Electronic Data Capture).
A number will be assigned to each patient; their identity will not be disclosed in any
case. All shared information will be anonymized. The principal investigator at each
center will be responsible for keeping the data anonymized.Data will be processed in
accordance with the protection legislation in force (Spanish Personal Data Protection and
Guarantee of Digital Rights Act 3/2018, and Regulation (EU) 2016/679).
Our aim will be to assess IMR values in heart transplant patients within one year and
evaluate changes in management after knowing of IMR values. We believe it is important to
move forward in AAR surveillance and reduce the number of endomyocardial biopsies. In
addition to assessing their diagnostic capabilities, IMR should also be assessed based on
clinical outcomes. Therefore, we are convinced the results of this trial will be very
important for our HT patient population.
