{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,11]],"date-time":"2026-08-11T04:32:00Z","timestamp":1786422720620,"version":"build-2736575974"},"reference-count":53,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,8,11]],"date-time":"2026-08-11T00:00:00Z","timestamp":1786406400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003484","name":"Heinrich-Heine-Universit\u00e4t D\u00fcsseldorf","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100003484","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Cardiovasc. Med."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Cardiopulmonary exercise testing (CPET) is the gold standard for assessing cardiopulmonary responses to physical stress. Real-time magnetic resonance imaging (RT-MRI) enables continuous cardiovascular imaging during free breathing (FB) and dynamic exercise.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>This study aimed to develop a clinically applicable, easy-to-use MR-CPET protocol using user-friendly postprocessing software and to describe preliminary physiological observations in healthy subjects, forming the basis for future clinical applications.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Material and Methods<\/jats:title>\n                    <jats:p>\n                      Healthy adults (\n                      <jats:italic>n<\/jats:italic>\n                      \u2009=\u200912) underwent conventional cine cardiac magnetic resonance imaging (CMR) and cardiac RT-MRI at rest and during submaximal exercise in a 1.5\u2005T MR scanner. The protocol included short-axis cine imaging for volumetry and phase-contrast imaging for aortic flow quantification. CPET was performed using an MR-compatible spirometry and a supine exercise setup enabling continuous measurement of respiratory airflow and gas exchange during image acquisition and simultaneous exercise. Data processing included automated spirometry analysis, temporal synchronization with RT-MRI, and ECG- and respiratory-based binning for volumetric reconstruction. Indexed oxygen consumption (VO\u2082i) and cardiac index (CI) were used to calculate the arteriovenous oxygen difference (a-vO\n                      <jats:sub>2<\/jats:sub>\n                      diff) according to the Fick equation. Participant comfort was assessed.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      The examination was well tolerated, with only minor discomfort related to the spirometry mask. RT-MRI showed strong agreement with conventional cine MRI for left ventricular volumes and ejection fraction at rest. Submaximal exercise significantly increased heart rate and ventilation, with concomitant increases in VO\n                      <jats:sub>2<\/jats:sub>\n                      i (201- 309\u2005mL\/min\/m\n                      <jats:sup>2<\/jats:sup>\n                      ) and CI (3.38- 4.24 L\/min\/m\n                      <jats:sup>2<\/jats:sup>\n                      ), while ventricular volumes slightly decreased and ejection fraction remained unchanged. The calculated a-vO\n                      <jats:sub>2<\/jats:sub>\n                      diff increased from 5.9 to 7.3\u2005mL\/dL, indicating enhanced peripheral oxygen extraction.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Data conclusion<\/jats:title>\n                    <jats:p>Combined CPET and cardiac RT-MRI using the presented user- and participant-friendly setup enables integrated assessment of cardiopulmonary performance and cardiovascular function during submaximal exercise and provides physiologically plausible Fick-derived measures of oxygen transport and utilization.<\/jats:p>\n                  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