Neural Mechanism of Cerebrocardiac Syndrome Following Traumatic Brain Injury

Brain network evaluation by MRI

MRI data of all participants are acquired within 3 days after enrollment, and the MRI scans include one or more of the following contents： 1. 3D T1-weighted images, which were acquired with a magnetization prepared rapid-acquisition gradient-echo sequence. 2. The resting state-fMRI data, acquired with an interleaved T2-weighted axial gradient-echo echoplanar imaging sequence. 3. DTI datasets, acquired using a fully-sampled spin-echo EPI sequence.

Cardiac evaluation by ECG

ECG data of all participants are acquired within 3 days after enrollment, and include resting and ambulatory ECG to detect arrhythmias, heart rate variability or myocardial ischemia. Specifically, arrhythmias include atrial fibrillation (irregular R-R intervals, absent P waves, fibrillatory waves), ventricular tachycardia (QRS \>120 ms, rapid rate, often no discernible P waves), heart blocks (1st degree: PR interval \>200 ms; 2nd degree: progressive PR prolongation until a QRS drops; 3rd degree: complete AV dissociation and atrial rate \> ventricular rate) and premature contractions (early beats with wide or narrow QRS). Heart rate variability is analyzed via R-R interval variability over time (24-hour Holter), and the indicators include Time-Domain (SDNN and RMSSD) and Frequency-Domain (LF/HF ratio). Myocardial ischemia indicators include ST segment depression ≥0.5 mm in ≥2 contiguous leads, ST elevation ≥1 mm in ≥2 contiguous leads, and inversion or hyperacute T waves.

Cardiac evaluation by echocardiography

Echocardiography data of all participants are acquired within 3 days after enrollment, in order to assess heart pumping function. Specifically, the key parameters assessed include ventricular function (ejection fraction: % of blood ejected per beat) and cardiac output quantification. The decline in the above indicators suggests heart ischemia or heart failure.

Cardiac evaluation by blood testing-1

Blood testing data of all participants are acquired within 3 days after enrollment and include several key cardiac biomarkers: myoglobin (normal: 14.3-65.8 μg/L), cardiac troponin I (cTnI, normal: 0-0.03 μg/L), cardiac troponin T (cTnT, normal: 0-0.1 μg/L), B-type natriuretic peptide (BNP, normal: 0-0.1 μg/L) and NT-proBNP (normal: \<0.3 μg/L). Specifically, elevated myoglobin is useful for early detection of myocardial infarction (MI); elevated cTnI and cTnT, especially with a rising/falling pattern, are gold standard for diagnosing MI; elevated BNP and NT-proBNP suggest heart failure (HF), especially BNP \>0.4 μg/L indicates severe HF.

Clinical prognosis assessed by GOS score

Glasgow Outcome Scale (GOS) score (1 = death; 2 = persistent vegetative state; 3 = severe disability; 4 = moderate disability; 5 = good but not necessarily complete recovery; unfavorable outcome was defined as score of ≤3, and favorable outcome was defined as a score of \>3)

Neurological function assessed by mRS score

Modified Rankin Scale (mRS) score (0 = no symptoms; 1 = no significant disability; 2 = slight disability; 3 = moderate disability; 4 = moderately severe disability; 5 = severe disability; 6 = dead; favorable outcome was defined as score of 0-2, and unfavorable outcome was defined as score of 3-6)