QRS complex and T wave planarity for the prediction of death and appropriate shocks in recipients of prophylactic implantable defibrillators

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Community’s 7th Framework Programme (HEALTH-F2-2009-602299) Ministry of Health, Czech Republic BACKGROUND: Three-dimensional (e.g., vectorcardiography) loops of normal physiologic QRS complex and T wave are known to be planar. Non-planarity of these electrocardiogram (ECG) loops was described in cardiac patients, mainly in relation to ischemic heart disease, but predictive values of the extent of non-planarity of the loops have not been systematically researched. METHODS: Pre-implantation digital ECGs were collected in 1948 cardiac patients (381 females, median age 65, inter-quartile range 56 – 72 years, 62% ischemic heart disease) who obtained an implantable cardioverter-defibrillator (ICD) for primary prophylactic reasons. In each ECG, QRS and T wave 3-dimensional loops were constructed using singular value decomposition and the non-planarity of the loops was measured as the relative power of the 3rd, least significant decomposition component. The non-planarity (i.e., the spatial twist) of the loops was related to all-cause mortality and to appropriate ICD shocks that occurred during the first 5 years after device implantation. This predictive power was compared to that of age, heart rate, left ventricular ejection fraction, QRS duration, spatial QRS-T angle, QTc interval, and T-peak to T-end interval. RESULTS: Non-planarity of the QRS loop was significantly associated with follow-up deaths despite ICD protection (p<0.001 both univariably and in multivariable Cox regression analysis) but was less powerfully associated with appropriate ICD shocks. Non-planarity of the T wave loop was significantly associated with appropriate ICD shocks during follow-up (p<0.001 both univariably and in multivariable Cox regression analysis) but was not associated with mortality during follow-up (Table). This was also seen in significant separation of Kaplan-Meier event probability curves (Figure). CONCLUSIONS: The analysed data of recipients of prophylactic ICDs suggest that non-planarity of QRS complex and T wave loops offers distinction between patients who are at greater risk of death despite ICD protection and those who are likely to utilize the defibrillator protection. [Figure: see text] [Figure: see text]