This study was approved and the requirement for informed consent from the study subjects was waived by the institutional review board (Ethics Committee on Epidemiological and its related Studies, Sakuragaoka Campus, Kagoshima University; approval number, 220009) due to the retrospective study design. This study was conducted in accordance with the Declaration of Helsinki and Ethical Guidelines for Medical and Health Research Involving Human Subjects in Japan.
Patients.
A retrospective review of the CT imaging database and clinical records of our radiology department identified 936 consecutive patients with suspected lung neoplasms who had undergone pretreatment chest CT examination between January 2018 and October 2020. Among these, 50 patients (27 men and 23 women; mean age, 68 ± 10 years; age range, 41 to 83 years) met the following inclusion criteria and were included in this study: (1) had undergone LUL; (2) the presence or absence of PV stump thrombus had been evaluated at 7 days after lobectomy using cine-MR images with or without contrast-enhanced cardiac CT.
Preoperative CT examination and left atrial volume measurement.
CT examinations were obtained on a 64-multidetector row CT scanner (IQon spectral CT, Philips Healthcare). The CT scan parameters were as follows: tube voltage, 120 kVp; effective tube current–time product, 160 mAs with automatic tube current modulation; rotation time, 0.4 seconds; pitch, 0.703; and collimator configuration, 64 × 0.625 mm. Scan timing was initiated 50 seconds after attenuation in the ascending aorta increased to a default threshold (150 HU), as measured by a dedicated monitoring system after intravenous administration of a nonionic contrast agent (Omnipaque 300 mgI/mL, Daiichi Sankyo, Tokyo, Japan). The injected contrast agent dose was 2.0 mL/kg body weight, up to a maximum dose of 150 mL for patients weighing ≥75.0 kg, and injection time was fixed at 30 seconds.
All CT images were transferred and analyzed using a thin-client workstation (SYNAPSE VINCENT, Fujifilm Medical Co., Tokyo, Japan). LA volume was measured by a radiologist with 20 years of chest radiology experience (K.T.) who was blinded to the final results of the presence or absence of PV thrombus after surgery. The 3D volume of the LA was semiautomatically obtained and measured using an automated analysis program installed in the workstation.
Evaluation of CHA 2 DS 2 -VASc score.
The CHA2DS2-VASc score was calculated for each patient as follows: two points were assigned for a history of stroke or transient ischemic attack (TIA), or age > 75 years; and 1 point was assigned for age 65–74 years, history of hypertension, diabetes mellitus, cardiac failure, vascular disease (myocardial infarction, complex aortic plaque and peripheral arterial disease) and female sex 22. Heart failure was defined as clinical heart failure (any history of systolic heart failure or ejection fraction < 40%). Hypertension was defined as high blood pressure (> 140/90 mm Hg) or receiving treatment with antihypertensive drugs. Diabetes mellitus was defined as a fasting plasma glucose level > 126 mg/dl or the use of oral anti-diabetic drugs and/or insulin. Vascular disease was defined as intermittent claudication, amputation, lower extremity revascularization, history of myocardial infarction, or complex aortic plaques on CT imaging.
Evaluation of PV stump thrombus after LUL.
Since November 2017, cine-MR imaging has been a part of our institute’s routine clinical protocol for evaluating the development of PV stump thrombus after LUL. Cardiac cine-MR imaging is considered a reliable diagnostic method for the evaluation of thrombus in the LA and LA appendage 23. All patients had undergone cine-MR examinations on postoperative day 7 using a 3T system (Prisma, Siemens Healthcare, Erlangen, Germany) with a 30-channel body array coil. Cine images were acquired in the coronal plane using the balanced steady state free precession (bSSFP) sequence (repetition time, 40–80 ms; echo time, 1.1 ms; flip angle, 48°; number of cardiac phases, 10–15; number of signals averaged, 1; field-of-view, 360 × 360 mm2; in-plane spatial resolution 1.9 ⋅ 1.9 mm; section thickness, 5 mm; number of slices, 27) with short periods of breath-holding. Thrombus was defined as a mass within the PV stump or LA cavity that had margins distinct from the PV stump or LA wall, and distinguishable from technical or flow artifact. All cases of suspected thrombus on cine-MR imaging underwent contrast-enhanced ECG-gated cardiac CT to confirm the presence of thrombus. The size of the PV stump thrombus was also measured in the axial plane on cardiac CT.
Statistical analysis.
LA volume and CHA2DS2-VASc score were compared between patients with and without the development of PV stump thrombus, using the Mann–Whitney U test. Spearman’s rank correlation coefficient was used to measure the association between LA volume and CHA2DS2-VASc score. Receiver–operating characteristic (ROC) curve analysis was performed to evaluate the accuracy of predicting the development of PV stump thrombus, for each of LA volume, CHA2DS2-VASc score, and their combination. For each parameter, optimal cutoff values were chosen using a threshold criterion that maximized the Youden index for predicting PV stump thrombus. The area under the ROC curve (AUC) for LA volume, CHA2DS2-VASc score, and their combination were compared using DeLong’s test 24. All data for continuous variables are presented as the mean ± standard deviation (SD). A P-value < 0.05 was considered to indicate statistical significance in all analyzes. Statistical analyses were performed using MedCalc version 20.1 (MedCalc Software, Mariakerke, Belgium) and SPSS version 28.0 (SPSS, Chicago, IL).