Quantification of Cardiopulmonary Interactions during Free Breathing by Semi-automatic Midventricular Parameters Using Real-Time Cardiac MRI and MR-Compatible Spirometry

Background: Respiration modifies cardiac function. Our aim was to analyze those interactions under physiological conditions. Real-time MRI is a technique which allows for a high temporal resolution while maintaining a high spatial resolution. In combination with MR-compatible spirometry, it is particularly useful to quantify changes due to respiration.

Methods: Healthy, young adults (n = 15) underwent a cardiac real-time MRI protocol (1.5 T, 30 frames/s) during deep breathing (breathing rate 12/min). Respiratory volume and flow were registered by MR-compatible spirometry. MR volumetry sequences with short axis orientation were acquired in parallel. The left and right ventricle were automatically contoured using commercial software. A software tool designed by our working group calculated the left ventricular end-diastolic epicardial eccentricity index (LV-EI(d)) and the mid-ventricular areas of the right and left cavity. Sorting of the images by heart cycle phase and respiratory volume served to describe cardiopulmonary interactions.

Results: The minimum of the LV-EI(d) occurred during late end-expiration and early inspiration. It increases with increasing respiratory volume and reaches its maximum before the maximum of the end-inspiratory respiratory volume. The right ventricular mid-ventricular area increases during inspiration with a maximum before the end-inspiration. The left ventricular area changed less and reached its maximum somewhat later, i.e., more closely to the maximal end-inspiratory respiratory volumes. End-diastolic left ventricular areas had a higher respiratory-dependent change than end-systolic areas.

Conclusion: The combination of RT-MRI with MRI-compatible spirometry is a valuable method to visualize and analyze the respiratory dependence of ventricular parameters. Future analyses will investigate the relationship of the midventricular parameters with the ventricular volumes and alterations under pathological conditions.

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Artikel online veröffentlicht:
13. Februar 2024