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Myocardial Infarct Size by CMR in Clinical Cardioprotection Studies: Insights From Randomized Controlled Trials
Heerajnarain Bulluck1, Matthew Hammond-Haley2, Shane Weinmann2
1The Hatter Cardiovascular Institute, Institute of Cardiovascular Science, University College London, United Kingdom; The National Institute of Health Research University College London Hospitals Biomedical Research Center, London, United Kingdom; National Heart Research Institute Singapore, National Heart Center Singapore, Singapore, Singapore.
Objectives:
The aim of this study was to review randomized controlled trials (RCTs) using cardiac magnetic resonance (CMR) to assess myocardial infarct (MI) size in reperfused patients with ST-segment elevation myocardial infarction (STEMI).
Background:
There is limited guidance on the use of CMR in clinical cardioprotection RCTs in patients with STEMI treated by primary percutaneous coronary intervention.
Methods:
All RCTs in which CMR was used to quantify MI size in patients with STEMI treated with primary percutaneous coronary intervention were identified and reviewed.
Results:
Sixty-two RCTs (10,570 patients, January 2006 to November 2016) were included. One-third did not report CMR vendor or scanner strength, the contrast agent and dose used, and the MI size quantification technique. Gadopentetate dimeglumine was most commonly used, followed by gadoterate meglumine and gadobutrol at 0.20 mmol/kg each, with late gadolinium enhancement acquired at 10 min; in most RCTs, MI size was quantified manually, followed by the 5 standard deviation threshold; dropout rates were 9% for acute CMR only and 16% for paired acute and follow-up scans. Weighted mean acute and chronic MI sizes (≤12 h, initial TIMI [Thrombolysis in Myocardial Infarction] flow grade 0 to 3) from the control arms were 21 ± 14% and 15 ± 11% of the left ventricle, respectively, and could be used for future sample-size calculations. Pre-selecting patients most likely to benefit from the cardioprotective therapy (≤6 h, initial TIMI flow grade 0 or 1) reduced sample size by one-third. Other suggested recommendations for standardizing CMR in future RCTs included gadobutrol at 0.15 mmol/kg with late gadolinium enhancement at 15 min, manual or 6-SD threshold for MI quantification, performing acute CMR at 3 to 5 days and follow-up CMR at 6 months, and adequate reporting of the acquisition and analysis of CMR.
Conclusions:
There is significant heterogeneity in RCT design using CMR in patients with STEMI. The authors provide recommendations for standardizing the assessment of MI size using CMR in future clinical cardioprotection RCTs.
Insights
This review of randomized controlled trials found significant heterogeneity in cardiac magnetic resonance (CMR) use for assessing myocardial infarct (MI) size in ST-elevation myocardial infarction (STEMI) patients. Recommendations are provided to standardize CMR protocols in future cardioprotection trials.
Area of Science:
- Cardiology
- Medical Imaging
- Clinical Trials
Background:
- Limited guidance exists for using cardiac magnetic resonance (CMR) in clinical cardioprotection randomized controlled trials (RCTs) for ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention.
- Standardization is crucial for reliable assessment of myocardial infarct (MI) size in these trials.
Purpose of the Study:
- To review existing randomized controlled trials (RCTs) that utilized cardiac magnetic resonance (CMR) for assessing myocardial infarct (MI) size.
- To identify common practices and variations in CMR methodology within these RCTs.
- To provide recommendations for standardizing CMR assessment of MI size in future cardioprotection RCTs for STEMI patients.
Main Methods:
- A comprehensive review of RCTs employing CMR to quantify MI size in STEMI patients treated with primary percutaneous coronary intervention was conducted.
- Data extraction focused on CMR acquisition parameters, contrast agents, quantification techniques, and reporting standards.
Main Results:
- Sixty-two RCTs involving 10,570 patients were analyzed, revealing significant heterogeneity in reported CMR details (vendor, scanner strength, contrast, dose, quantification methods).
- Gadopentetate dimeglumine was the most common contrast agent, typically administered at 0.20 mmol/kg with late gadolinium enhancement at 10 minutes.
- Manual quantification and the 5 standard deviation threshold were frequent MI size assessment methods. Dropout rates varied based on scan timing.
- Weighted mean acute and chronic MI sizes were established for control arms, offering potential for future sample-size calculations. Patient selection strategies could reduce required sample sizes.
Conclusions:
- Significant heterogeneity exists in the design of RCTs using CMR for STEMI patients.
- The study provides evidence-based recommendations to standardize CMR protocols for MI size assessment in future clinical cardioprotection RCTs.
- Adoption of these recommendations will enhance the reliability and comparability of findings across multicenter trials.
