Biomechanical Properties of the Human Ascending Aortic Wall in Aneurysm

Description of the procedures:

All surgical procedures will be performed via median sternotomy. During the aortic arch anastomosis, continuous, unilateral SACP using innominate artery will be employed. Unilateral SACP may be converted to bilateral ACP at the surgeon's discretion if adequate cerebral flows are not achieved or if there are concerns with cerebral oximetry measurements.

Once on CPB, the patient will be cooled to a nasopharyngeal (NP) temperature of 28-30 °C. Rectal temperature with be monitored as an additional temperature sites. Unilateral SACP will only be initiated once the target temperature has been reached. SACP via the innominate artery will be commenced with target flows of 8-10 ml/kg/min and perfusion pressure of 60-80 mmHg. Perfusion adequacy will be evaluated using measurement of blood pressure in both radial arteries and cerebral oximetry using near-infrared spectroscopy (NIRS).

After completion of the aortic hemiarch replacement, CPB will be resumed and the patient re-warmed to 36 °C prior to coming off CPB, with a = 1 °C temperature difference between temperature monitoring sites (NP and rectal).

Intraoperative information will be collected from the anesthetic record, surgical notes and perfusion records. Intraoperative data collection will include total operative time, CPB time, cross-clamp time, hypothermic cardiac arrest time, uSACP time, lowest nasopharyngeal and rectal temperature, arterial pressure in both radial arteries, perfusion rate and perfusion pressure during both of CPB and unilateral SACP, lowest hemoglobin concentration (g/L) and hematocrit (%), acid-base indices, intraoperative red blood cell transfusion (units), highest dose/agent used for intraoperative inotrope or vasopressor support. Also during the surgery will be performed NIRS and BIS-monitoring.

Postoperative data will include valuation of following indicators: mortality (hospital mortality and death from any cause); neurological injury (TIA, stroke, delirium), MRI and CT-scan only in event of postoperative stroke; acute kidney injury (creatinine level prior and 1, 2, 4 postoperative day (POD), urine output-up to 24-48 h, renal replacement therapy (dialysis); time of mechanical ventilation; re-exploration for bleeding, tamponade or other reasons; postoperative transfusion (packed red blood cells, platelets, fresh frozen platelets, cryoprecipitate); postoperative myocardial infarction (electrocardiogram and troponins); inotropic support during 24-48 h (agent and dose (VIS)); length of stay (intensive care unit and total hospital days).

In non-operted grop of patients annually echo cardiography, CT scans will be performed.

Aortic imaging All measurements will be taken using electrocardiography-gated computed tomographic angiography. Analysis was performed using 64-slice scanner Discovery NM-CT 570c (GE Healthcare, Milwaukee, WI, USA) with spatial resolution of the angiographic phase ranging from 0.6 to 1.25 mm. Adopted computed tomographic protocol included unenhanced, arterial, and delayed data acquisition. The arterial phase will be acquired after intravenous injection of 80-100 mL of nonionic iodinated contrast at 5 mL/s, followed by a 50-mL bolus of saline solution. Delayed-phase scans will be obtained 120-180 seconds after contrast injection. All measurements will be taken in multiplanar reconstruction, always in the plane perpendicular to the manually corrected local aortic centre line. Ascending aortic diameter will be measured at the level of the pulmonary artery bifurcation. The maximum aortic diameter (mm) will be measured from the outer contours of the aortic wall. Normalized aortic diameter (cm/m2) will be calculated by dividing the maximum aortic diameter (cm) by the body surface area (m2). The body surface area will be calculated based on the Mosteller formula: body surface area (m2) = √([Height (cm) x Weight (kg)]/3600). Analysis and assessment of the images will be based on the consensus between two experienced investigators.

Follow-up information will be collected using direct or phone contact with patients, relatives, or physicians.