Electrocardiogram-based predictors for arrhythmia after spinal cord injury

Individuals with spinal cord injury (SCI) have an increased risk of cardiac arrhythmias, particularly during autonomic dysreflexia (acute hypertensive episodes). This may be partly due to impaired autonomic control of the heart after SCI. The interval between the peak and end of the T-wave of the electrocardiograph (ECG) provides an index of transmural dispersion of repolarisation, a factor underlying the development of ventricular arrhythmias. Another ECG-based risk factor for ventricular arrhythmias is variability in the QT segment, the QT variability index (QTVI). Similarly, P-wave variability may be correlated with risk for atrial arrhythmias. We aimed to: (1) determine whether there are abnormalities in these parameters at rest in those with SCI; (2) determine correlations between these ECG parameters and severity of autonomic impairment after SCI.

ECG intervals were determined using customised software from a 15 min ECG recording (lead II) in 28 SCI subjects and 27 controls. Autonomic severity of SCI was determined from sympathetic skin responses, low frequency systolic blood pressure variability, and plasma noradrenaline levels.

T(peak)-T(end) variability and QTVI were increased in those with autonomically complete SCI compared to controls. P-wave variability was increased in SCI individuals compared to controls, and was negatively correlated with plasma noradrenaline.

The higher T(peak)-T(end) variability, QTVI and P-wave variability in individuals with SCI could be markers of severity of injury to cardiac autonomic (sympathetic) pathways after SCI, and may represent new risk assessment parameters for predisposition to cardiac arrhythmias in this population.