Sudden Cardiac Death in Dialysis: Arrhythmic Mechanisms and the Value of Non-invasive Electrophysiology

Abstract

Sudden Cardiac Death (SCD) is the leading cause of cardiovascular death in dialysis patients. This review discusses potential underlying arrhythmic mechanisms of SCD in the dialysis population. It examines recent evidence from studies using implantable loop recorders and from electrophysiological studies in experimental animal models of chronic kidney disease. The review summarizes advances in the field of non-invasive electrophysiology for risk prediction in dialysis patients focusing on the predictive value of the QRS-T angle and of the assessments of autonomic imbalance by means of heart rate variability analysis. Future research directions in non-invasive electrophysiology are identified to advance the understanding of the arrhythmic mechanisms. A suggestion is made of incorporation of non-invasive electrophysiology procedures into clinical practice. Key Concepts: - Large prospective studies in dialysis patients with continuous ECG monitoring are required to clarify the underlying arrhythmic mechanisms of SCD in dialysis patients. - Obstructive sleep apnoea may be associated with brady-arrhythmias in dialysis patients. Studies are needed to elucidate the burden and impact of sleeping disorders on arrhythmic complications in dialysis patients. - The QRS-T angle has the potential to be used as a descriptor of uremic cardiomyopathy. - The QRS-T angle can be calculated from routine collected surface ECGs. Multicenter collaboration is required to establish best methodological approach and normal values. - Heart Rate Variability provides indirect assessment of cardiac modulation that may be relevant for cardiac risk prediction in dialysis patients. Short-term recordings with autonomic provocations are likely to overcome the limitations of out of hospital 24-h recordings and should be prospectively assessed.

Keywords: QRS-T angle; TCRT; arrhythmias; dialysis; heart rate variability; implantable loop recorders; sudden cardiac death.

FIGURE 1

Three-dimensional representation of QRS and T vector loops following computerized analysis of standard 12 lead ECG using singular value decomposition to yield an orthogonal lead system (TCRT method). The little white circle in the middle depicts the loop of the p wave. The curved red line with arrow at both ends depicts the spatial QRS-T angle. The maximal T wave vector magnitude is used for the calculations with this method. TCRT is the averaged cosine of the angles between the T wave vector and all vectors within the QRS complex exceeding a pre-defined level. A different method of QRS-T angle measurement from standard 12 lead digital snapshot ECG uses inverse Dower matrix for vectrographic transformation and calculates the angle between the mean vectors of the QRS and T wave. QRS-T angle has also been calculated from continuous signal averaged ECGs as the angle between the peak QRS vector and the peak T vector.

FIGURE 2

Kaplan–Meier survival curves of total mortality and major cardiac events 72 HD patients included in a recently published study (Poulikakos et al., 2018) stratified by QRS-T angle calculated by TCRT above (red) and below (blue) median value (p = 0.000 Log Rank test). Darker bands depict interquartile ranges and the lighter bands ranges between 10th and 90th percentiles. The calculation of confidence intervals was performed using bootstrap 10,000 repetitions. Major cardiac events were defined as sudden cardiac death, acute coronary syndrome, coronary revascularization or admission due to heart failure or arrhythmia.

FIGURE 3

Kaplan–Meier survival curves of total mortality and major cardiac events in 72 HD patients included in a recently published study (Poulikakos et al., 2018) stratified by LF/HF above (blue) and below (red) median value (p = 0.001 Log Rank test). Darker bands depict interquartile ranges and the lighter bands ranges between 10th and 90th percentiles. The calculation of confidence intervals was performed using bootstrap 10,000 repetitions. Major cardiac events were defined as sudden cardiac death, acute coronary syndrome, coronary revascularization or admission due to heart failure or arrhythmia.