QRS analysis using wavelet transformation for the prediction of response to cardiac resynchronization therapy: A prospective pilot study ☆ Vassilios P. Vassilikos, MD, PhD, a Lilian Mantziari, MD, PhD, a,b, ⁎ Georgios Dakos, MD, PhD, a Vasileios Kamperidis, MD, MSc, a Ioanna Chouvarda, PhD, c Yiannis S. Chatzizisis, MD, PhD, a Panagiotis Kalpidis, MD, a Efstratios Theofilogiannakos, MD, PhD, a Stelios Paraskevaidis, MD, PhD, a Haralambos Karvounis, MD, PhD, a Sotirios Mochlas, MD, PhD, a Nikolaos Maglaveras, PhD, c Ioannis H. Styliadis, MD, PhD a a First Department of Cardiology, AHEPA University Hospital, Aristotle University Medical School, Thessaloniki, Greece b Cardiology Department, Royal Brompton Hospital, London, UK c Laboratory of Medical Informatics, Aristotle University Medical School, Thessaloniki, Greece Abstract Background: Wider QRS and left bundle branch block morphology are related to response to cardiac resynchronization therapy (CRT). A novel time-frequency analysis of the QRS complex may provide additional information in predicting response to CRT. Methods: Signal-averaged electrocardiograms were prospectively recorded, before CRT, in orthogonal leads and QRS decomposition in three frequency bands was performed using the Morlet wavelet transformation. Results: Thirty eight patients (age 65 ± 10 years, 31 males) were studied. CRT responders (n = 28) had wider baseline QRS compared to non-responders and lower QRS energies in all frequency bands. The combination of QRS duration and mean energy in the high frequency band had the best predicting ability (AUC 0.833, 95%CI 0.705-0.962, p = 0.002) followed by the maximum energy in the high frequency band (AUC 0.811, 95%CI 0.663-0.960, p = 0.004). Conclusions: Wavelet transformation of the QRS complex is useful in predicting response to CRT. © 2014 Elsevier Inc. All rights reserved. Keywords: Heart failure; Biventricular pacing; Morlet wavelet transform; QRS complex; Signal processing Introduction Cardiac resynchronization therapy (CRT) was introduced as a revolutionary treatment for patients with advanced heart failure and left ventricular (LV) conduction delay, aiming to restore the electrical dyssynchrony, improve LV mechanics and thus reduce heart failure morbidity and mortality. 1–3 Nevertheless, about one third of patients fulfilling the criteria for CRT implantation, as suggested by guidelines, 4,5 show no benefit from this treatment. Patients with wider QRS are more likely to respond possibly because QRS duration correlates with the degree of LV posterolateral wall conduction delay in the presence of left bundle branch block (LBBB). 6 However, QRS duration does not consistently reflect the underlying severity of mechanical dyssynchrony. 7 Since echocardiographic indices of mechanical dyssyn- chrony are unreliable and difficult to obtain consistently, 8 the effort to define electrical measures of LV depolarization has become attractive again. Different patterns of LV electrical activation sequence both during intrinsic conduc- tion in LBBB and in response to pacing have been recorded, allowing the conclusion that not all LBBBs are created equally. 6 Surface ECG provides a time-domain analysis of the electrical activation of the heart. However the frequency content of the signal may provide additional information. The wavelet transform is a mathematical function that has been used for almost two decades as an alternative to the traditional time-domain methods provid- ing a time-frequency domain analysis. 9,10 Wavelet decom- position of the signal-averaged electrocardiogram has been Available online at www.sciencedirect.com ScienceDirect Journal of Electrocardiology 47 (2014) 59 – 65 www.jecgonline.com ☆ Disclosures: None. ⁎ Corresponding author. First Department of Cardiology, AHEPA University Hospital, Aristotle University Medical School, 1 Stilponos Kiriakidi St, 54636, Thessaloniki, Greece. E-mail address: lmantziari@yahoo.com 0022-0736/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jelectrocard.2013.08.003