Patient selection and data collection
After obtaining approval from the review board of Chiba Nishi General Hospital, we performed a prospective, observational study of data collected from patients who underwent right mini-thoracotomy, which is a minimally invasive surgery, at Chiba Nishi General Hospital between July 2014 and July 2018. All patients were diagnosed based on cardiac catheterization and echocardiography findings. During the study period, there were 273 patients who underwent MICS and MRI, including diffusion-weighted imaging (DWI) sequences, the day before and 5 days after surgery. We selected the femoral artery for retrograde perfusion and the axillary artery or ascending aorta for antegrade perfusion. Preoperative computed tomography (CT) angiography was routinely performed, and vascular pathology was evaluated.
The femoral artery was chosen as the cannulation site if the patients met the following criteria: 1) no calcification in the entire circumference of the aorta, 2) thrombosis in less than one-third of the aorta, and 3) thrombosis in the aorta with thickness <3 mm. In patients who did not meet the criteria, antegrade cannulation was performed.
Of 273 patients, 175 (64.8%) underwent femoral cannulation for CPB and 95 (34.4%) axillary arterial cannulation. Moreover, one (0.37%) patient had both femoral cannulations, 1 patient (0.37%) femoral and axillary arterial cannulations, and remaining 1 patient (0.37%) ascending aorta cannulation. Patients who underwent axillary arterial cannulation, both femoral and axillary arterial cannulations, and ascending aorta cannulation were excluded. Moreover, one patient who presented with a subdural hematoma 3 days after the surgery was excluded. Finally, 174 patients were included in the study (Figure 1).
Patients who were scheduled for right mini-thoracotomy underwent MRI, including DWI sequences, the day before and 5 days after surgery. SBIs detected via DWI were categorized as follows: A) 1–3 DWI spots measuring <10 mm, B) >3 DWI spots measuring <10 mm, and C) single DWI lesion measuring >10 mm (Figure 2).
A high field strength (3T) MRI unit was used. The protocol included axial T2-weighted imaging, axial T2-weighted fluid attenuation inversion recovery imaging, axial trace-weighted DWI, and apparent diffusion coefficient mapping.
All images were evaluated by a diagnostic radiologist. When lesions were detected, neurosurgeons were consulted. Renal failure was defined as the requirement of hemodialysis or an elevated creatinine level at 2.0 mg/dL, which is two times the preoperative baseline level. Thirty-day mortality was defined as all deaths within 30 days after surgery regardless of where the patients died (in- or out-of-hospital).