Normal Defined for Adolescent Hearts Under Cardiac MRI

With new cardiac MRI (CMR) reference values for healthy adolescents, clinicians may have a better picture of what a normal scan looks like on this increasingly favored noninvasive imaging modality.

Reference values for anatomical and functional parameters in the heart during adolescence were based on a Spanish regional population and reported by Rodrigo Fernández-Jiménez, MD, PhD, of Centro Nacional de Investigaciones Cardiovasculares (CNIC) and Hospital Universitario Clínico San Carlos in Madrid, Spain, and colleagues.

The researchers set sex-stratified comprehensive percentile tables for various 3-Tesla cardiac MRI parameters in a paper published in eClinicalMedicine:

• Left and right ventricular end-diastolic indexed volumes

• Left and right ventricular ejection fraction

• Indexed atrial size and function parameters

• Global myocardial native T1 and T2 relaxation times

“This information is useful for clinical practice and may help to distinguish between the diseased and healthy cardiac states and in the differential diagnosis of cardiac diseases, such as cardiomyopathies and myocarditis, in adolescent populations,” the authors concluded.

“[W]ith this information, physicians at any center can determine if cardiac MRI data from an adolescent’s heart fall within the normal range for this age group, and prescribe closer follow-up and additional tests if needed,” Fernández-Jiménez said in a press release.

These reference values fill a gap in the literature as most published MRI data from adolescents come from patients with congenital heart defects or other heart conditions. In healthy pediatric populations, most studies assessing cardiac structure and function have relied on another imaging modality, echocardiography, because of its simplicity and availability, the investigators noted.

Advances in cardiac MRI technology have contributed to its rise in recent years.

“Magnetic resonance imaging has become a very important method for studying the heart because it avoids exposing patients to radiation and provides more information, and with greater precision, than ultrasound, currently the most frequently used cardiac imaging technique,” said co-investigator Valentín Fuster, MD, PhD, of CNIC and Mount Sinai Medical Center in New York City, in the press release.

Yet because of the resources required, cardiac MRI is considered a selective downstream test and not recommended for widespread routine screening. This was a point of contention early on in the COVID pandemic, when cardiac MRI scans provided evidence of lingering myocardial inflammation and other cardiac abnormalities in COVID-19 survivors.

Reassuringly, however, problems with heart inflammation and cardiac function after COVID generally resolve within months, reports show.

Moreover, cardiac involvement was observed in just 3.8% of professional athletes who had COVID and systematic cardiac screening in the form of troponin testing, electrocardiography, and resting echocardiography in 2020. The prevalence of inflammatory heart disease specifically — myocarditis being a known risk factor of sudden cardiac death — was 0.6% in that study.

For the development of the present cardiac MRI reference values, Fernández-Jiménez and colleagues drew upon an ongoing cluster-randomized trial testing the effects of a school-based behavioral intervention on adolescent obesity and lifestyle.

Participants were 123 adolescent boys and girls with no known cardiovascular disease who were enrolled in one of seven schools in the Madrid area. They agreed to undergo a non-contrast 3-Tesla CMR scan between March 2021 and October 2021.

The cohort averaged 16 years of age and 52% were girls. Over one in five had at least one parent born outside Spain.

“This study reports reference values of CMR parameters based in a relatively large adolescent sample based in Spain and has some limitations. The impact of race/ethnicity on CMR reference values could not be assessed and the geographical limitation of the sample could compromise external validity,” Fernández-Jiménez and co-authors acknowledged.

They recommended that centers check the reference mapping values with their own local data.