Skeletal Muscle Assessment Modalities in Heart Transplant Candidates: A mixed methods study

This cross-sectional observational study includes adults (>18 years) with advanced heart failure undergoing assessment for heart transplantation at a tertiary transplant centre. The primary condition observed is skeletal muscle status, assessed using computed tomography derived skeletal muscle cross-sectional area (CT-CSA) at the third lumbar vertebra (L3) (the reference method), compared with bedside skeletal muscle measurement modalities, including ultrasound-derived muscle thickness, anthropometric measures (mid-upper arm circumference, mid-arm muscle circumference, calf circumference), and subjective physical examination. In addition, CT images will be analysed using both manual segmentation (SliceOmatic) and automated artificial intelligence (AI)-based segmentation methods (SliceOmatic Python module and Data Analysis Facilitation Suite (DAFS) to evaluate agreement between manual and AI-derived CT muscle measurement techniques. Additional conditions observed include the prevalence of malnutrition, frailty, sarcopenia, and cachexia. A nested qualitative sub-study explores patients’ experiences of nutrition care and the acceptability of bedside skeletal muscle assessment procedures during the heart transplant assessment process. CT Image Analysis: All CT scans are performed once per clinical indication as part of routine clinical care for heart transplantation evaluation (thoracic and abdominopelvic CT), independent of study participation. The duration of CT scans are typically 15 minutes in length. Scans are ordered by the treating clinical team and performed by qualified radiographers within the hospital radiology department. Once participants are enrolled in the study, a single axial CT slice at the L3 vertebral level will be retrospectively analysed for skeletal muscle cross-sectional area (cm²). Analysis will be conducted using commercially available software via manual segmentation using SliceOmatic (TomoVision, Montreal, Canada), and AI based segmentation via the SliceOmatic Python module and Data Analysis Facilitation Suite (DAFS) (Voronoi Health Analytics, Victoria, Canada). All CT muscle segmentation techniques are applied after clinical imaging has been completed, using de-identified CT images, and does not influence clinical decision-making. Anthropometric Measurements: All anthropometric measurements are taken within 7 days of the routine CT scan. Mid Upper Arm Circumference (MUAC): The same anatomical site used for the upper arm ultrasound assessment will be used (the midpoint between the acromion and olecranon). A measurement will be taken with the participant in a seated position, with the arm relaxed and hanging naturally by the side. A non-stretch measuring tape will be wrapped around the marked anatomical to record the circumference. Mid Arm Muscle Circumference (MAMC): Triceps skinfold thickness (mm) will be measured using a Harpenden skinfold caliper (British indicators Ltd., St Albans, Herts, UK), which will be applied to the posterior surface of the fully relaxed and lifted right arm at the marked point on the mid-upper arm with the participant in a seated position. The measurement will be recorded to the nearest millimetre and converted to centimetres for analysis. The following equation will be used to calculate Mid Arm Muscle Circumference: MAMC = MUAC – [3.14 x tricep skinfold thickness (cm)] Calf Circumference (CC): Calf circumference will be taken, with the patient seated, foot flat to the floor, and the leg at a 90-degree angle. Calf circumference will be measured at the point of maximum circumference using a non-stretch tape measure. The tape will be fit snugly to the skin, without applying excessive pressure or indenting the skin The total duration of all anthropometric measures will take approximately 10 minutes to complete. Subjective physical assessment: A subjective physical assessment will be conducted within 7 days of the routine CT scan. The subjective physical assessment of muscularity will be conducted using the subjective global assessment physical assessment tool, that considers subcutaneous fat loss, fluid retention, and muscle wasting and classifying patients as having low, moderate, or high skeletal muscle depletion. The total duration of the subjective physical assessment will take approximately 5 minutes to complete. Qualitative data: Qualitative data will be collected through individual semi-structured interviews designed to explore participants’ experiences of nutrition care and the acceptability of bedside skeletal muscle assessment procedures during the heart transplant assessment process. Participants will be invited to take part in a single interview, conducted approximately within 2-3 weeks of the routine CT scan. Interviews will be conducted by a member of the research team (a qualified Alfred Health clinical dietitian) who was not involved in the was not involved in the collection of bedside anthropometric or ultrasound data, to support independence of data collection and minimise potential response bias. Interviews may take place in person, via telephone, or via videoconference, according to participant preference, and will be approximately 30–45 minutes in duration. Interviews will be audio-recorded with participant consent using Microsoft Teams (Microsoft Corporation, Redmond, Washington, USA) and transcribed verbatim. Audio recordings will be deleted following transcription. Participants will be offered the opportunity to review their transcript and provide clarifications or corrections if they wish.