Standard risk prediction models in cardiac surgery (such as EuroSCORE II or STS score) are designed to analyze solely the risk of short-term postoperative mortality. The postoperative morbidity, the ability to rehabilitate or the mid-term survival are not addressed by these means. Recently there have been some reports that addition of physical performance testing to the standard prediction models may provide prognostic value. There is a wide scale of various physical performance and frailty tests that could be used for this purpose, but they have not been confronted with each other yet. Moreover, the postoperative physical rehabilitation has not been objectively assessed in larger scale despite the significant improvement in technology.

The hypothesisis of the study is that the preoperative outcomes of physical performance and frailty testing are able to predict the patient's reconvalescence after cardiac surgery in the short- and mid-term postoperatively. The aim is to analyze a set of tests with regard to their ability to predict postoperative reconvalescence, including the objective activity assessment (using Actigraph wGT3X-BT activity tracking device). Secondarily, the investigators aim to follow the patients up to 1 year postoperatively in terms of evaluating their mid-term outcomes.

Detailed description of testing performed in the exact order as in the patient:

1. Body weight and body composition (weigth of fat, weigth of muscle) measurement using bioimpendance scale Tanita BC 545N.
2. Katz Index of Independence in Activites of Daily Living performed and assessed exactly as described elsewhere.
3. Hand-grip strength test using the Kern MAP 80K1 device. Modified Southhampton protocol will be used for the measurement: Patient is sitting on a chair without side arms, the elbows are in a right angle. The patient is instructed to squeeze the device as much as possible and hold for 3 seconds. He squeezes the device with the right hand, then with the left hand. This is performed two times with each hand in total. The highest measured value is recorded.
4. 5-meter gait test. Patient is instructed to walk the 5-meter line as fast as possible and the time is being measured. This is repeated three times. Average time of the three attempts is recorded.
5. 6-minute walk test. Patient is instructed to walk without interruption for 6 minutes in the corridor of department's standard ward (exactly 36 meters long). He walks there and back repeatedly and the walked distance is calculated with regard to the number of corridors walked.
6. During the last two tests patient is wearing a pulse oxymeter (Berry BM1000C) that is connected with investigator's smartphone (either Android or iOS) through bluetooth. Eventual latent respiratory failure is recorded, defined as a drop in peripheral saturation of 4 % and more, or under 88 %.
7. Pre-defined set of laboratory blood tests: haemoglobin, creatinin, albumin, TSH, free T3, free T4.

Inclusion Criteria:

• informed patient consent
• patient scheduled for an elective cardiac surgery. The following procedures are accepted: coronary artery bypass grafting (CABG) , single valve replacement (SVR), CABG + SVR, CABG + MAZE procedure, SVR + MAZE procedure
• since June 2021, patients undergoing double-valve surgery have been allowed to be included in the study to promote patients inclusion

Exclusion Criteria:

• complex cardiac surgery (except the options listed above)
• ejection fraction of the left ventricle < 30 % according to the last preoperative echocardiography
• EuroSCORE II value > 5 %
• urgent or emergent surgery
• patient unable to walk and/or perform the test
• severe dementia (due to unability to cooperate during the testing and follow-up)
• re-do surgery
• minimally invasive surgery (i.e. other than full median sternotomy)

Patients scheduled for non-complex elective cardiac surgery at a single tertiary care cardiovascular center in the Czech Republic.

The anonymized individual patient data will be shared upon a reasonable request to the principal study investigator.