Sarcopenia or muscle loss and function is a component of the frailty syndrome. In this sense, frailty is becoming an important risk factor in predicting outcomes after major surgery and is defined as a geriatric syndrome of decreased reserve and resiliency to stressors that have been associated with adverse health outcomes in older adults. Despite its potentially relevant role in predicting postoperative recovery, frailty is rarely evaluated before surgery, and this is partially due to the low reliability of the most used frailty scores. Therefore, improvement in the frailty evaluation would be beneficial during the preoperative assessment of major surgeries. Sarcopenia, or the decline of skeletal muscle tissue with age, is one of the most important causes of functional decline and loss of independence in older adults and low muscle mass is a core component of frailty that has the advantage of being objectively quantifiable regardless of mobility, disability, or illness acuity. Psoas Muscle (PM) mass is an important parameter for evaluating muscle mass and has been previously correlated to frailty with a negative impact on the postoperative outcomes after major surgery and Psoas Muscle mass Index (PMI) is an easily available parameter for evaluating muscle mass and has already been demonstrated to be effective in predicting outcomes in different clinical settings. PMI has also been shown to be an effective predictor of outcomes in cardiac surgery although there are no studies specifically focusing on minimally invasive cardiac surgery. With this study, the investigators aim to investigate the relevance of PMI as a predictor of postoperative mobilisation, hospital length of stay and clinical recovery after major cardiac surgery conducted via a minimally invasive approach.

This is a prospective, controlled, observational single-centre study of patients undergoing minimally invasive heart valve surgery at the department of minimally invasive cardiac surgery of the IRCCS Galeazzi Sant'Ambrogio Hospital, in Milan (Italy).

The primary endpoint is to evaluate the role of psoas muscle index (PMI) in predicting length of stay and early mobility after heart valve surgery via a minimally invasive approach.

25 consecutive participants patients undergoing minimally invasive cardiac surgery will be assessed with a lower abdomen MRI before the surgery to evaluate the diameter of the psoas muscle and therefore assess the Psoas Muscle Index (PMI). Frailty will be evaluated using the PRISMA-7 questionnaire.

PMI value will be correlated with the main outcomes via regression methods and adjusted for covariates.

The participants will be consented to the study before the cardiac surgery operation (indexed procedure). Surgeries will include aortic, mitral and tricuspid valve operations conducted either via a mini-thoracotomy or a mini-sternotomy approach and every patient will receive routine preoperative, operative and postoperative cardiac surgery care. In addition to standard cardiac surgery clinical variables, the investigators will collect data on:

• Total intubation hours
• Total Intensive Treatment Unit (ITU) length of stay
• Total postoperative length of hospital stay
• Time between end of surgery and first mobilisation (see below)

Inclusion Criteria:

• Elderly patients (≥ 65 years old)
• Able to take consent
• Listed for minimally invasive cardiac surgery
• Elective and urgent procedures included
• Able to undergo MRI

Exclusion Criteria:

• Full median sternotomy approach
• Emergency procedures
• Unable to take consent
• Unable to undergo MRI

Cardiac surgery patients undergoing heart valve surgery via a minimally invasive approach