PURPOSE

MRI plays a vital role in congenital heart disease (CHD) imaging without ionizing radiation. Conventional CHD MRI exams require multi-slice cine acquisition, angiography, and phase-contrast imaging. Recently, a 4D (MUSIC) technique has been described^1,2, which generates high-resolution 3D dynamic images of the beating heart during uninterrupted ventilation. We evaluated the diagnostic performance and clinical impact of 4D MUSIC in neonates and infants with congenital heart disease (CHD).

METHODS

Forty consecutive children with CHD (age range 2 days to 2 years, weight 1 to 13 kg) underwent MRI with ferumoxytol (FE) at 3.0T and were prospectively enrolled. Two readers graded the diagnostic image quality of intra-cardiac structures and vascular segments including coronaries using a four-point scale. A score of 4 reflects excellent image quality with well-defined, sharp borders whereas a score of 1 reflects non-diagnostic image quality. Correlation of FE-MUSIC findings with other imaging modalities and/or surgical reports was performed. Clinical impact was assessed on a five-point scale (one point per key measure): 1) change in overall management, 2) change in surgical approach, 3) elimination of need for diagnostic catheterization, 4) improved assessment of risk-to-benefit for planned intervention and discussion with parents, and 5) accurate pre-procedural roadmap

RESULTS

All studies were technically successful and there were no adverse events. In all cases, FE-MUSIC satisfactorily answered all clinical questions requested by referring surgeons or cardiologists and in many cases provided additional insight, which impacted the overall patient care plan. On a four-point scale, the average FE-MUSIC image quality scores were >3.5 for intra-cardiac structures and >3.0 for coronary arteries. Intra-cardiac morphology and vascular anatomy were visualized with good interobserver agreement (r=0.46). Tiny structures such as the course of a 1mm vestigial aortic root in a neonate weighing 3.6 kg was well-visualized (Figure 1). Concordance with correlative imaging, surgical, and /or autopsy results was excellent. In five patients with discordant findings on echo /MUSIC (n=5) and catheter angiography /MUSIC (n=1), findings on FE-MUSIC were shown to be accurate at autopsy (n=1) and surgery (n = 4). The clinical impact score was 4.2±0.9. Surgical management was affected in all cases. Of the 28 cases where management may have called for cardiac catheterization to assess vascular anatomy, diagnostic cath was avoided in 13 patients because vascular anatomy and its relationship to intracardiac morphology were well visualized on FE-MUSIC imaging (Figure 2). In 75% of cases, clinical impact was affected across more than four key outcome measures.

CONCLUSION

FE-MUSIC provides reliable high-resolution dynamic imaging of all relevant cardiac and vascular anatomy in neonates with CHD. By obviating the need for breath holding and operator input, FE-MUSIC promises to enhance the practicality and generalizability of MRI in children.

Acknowledgements

This work is supported by grant R01HL127153 from the National Heart, Lung, and Blood Institute.