IJCA-17424; No of Pages 2 International Journal of Cardiology xxx (2014) xxx–xxx
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Letter to the Editor
Geometrical characteristics of interventricular electrical delay☆ Giuseppe Stabile a,⁎, Antonio D'Onofrio b, Albino Reggiani c, Antonio De Simone d, Antonio Rapacciuolo e, Quintino Parisi f, Domenico Pecora g, Daniela Orsida h, Tiziana Giovannini i, Michele Accogli j, Assunta Iuliano a, Gianluca Botto k, Emanuele Bertaglia l, Maurizio Malacrida m, Luigi Padeletti n a
Clinica Mediterranea, Napoli, Italy Ospedale Monaldi, Napoli, Italy Ospedale Carlo Poma, Mantova, Italy d Clinica San Michele, Maddaloni (CE), Italy e Departments of Advanced Biomedical Sciences, Federico II University of Naples, Italy f Fondazione di Ricerca e Cura ‘Giovanni Paolo II’, Università Cattolica del Sacro Cuore, Campobasso, Italy g Ospedale Poliambulanza, Brescia, Italy h Ospedale Sant'Antonio Abate, Gallarate (VA), Italy i Ospedale “Misericordia e Dolce”, Prato, Italy j Ospedale Panico, Tricase (LE), Italy k Ospedale S'Anna, San Fermo della Battaglia (CO), Italy l Universita' di Padova, Padova, Italy m Boston Scientific Italia, Milano, Italy n Ospedale Careggi, Università di Firenze, Firenze, Italy b c
a r t i c l e
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Article history: Received 12 November 2013 Accepted 28 December 2013 Available online xxxx Keywords: Resynchronization therapy Heart failure Interventricular delay Interlead distance
It has been reported that a significant proportion of cardiac resynchronization therapy (CRT) patients does not benefit from treatment [1]. The lack of response to CRT has a variety of potential causes. In particular, patient selection and implantation procedure are fundamental to the success of CRT [2]. Given that CRT is intended to improve ventricular synchrony by coordinating left ventricle (LV) and right ventricle (RV) contractions, the suggestion has been made that optimal lead positioning could result from maximal RV to LV electrode separation [3]. Both interventricular lead distance [4] and spontaneous interventricular conduction time [5] have been reported to predict the response to CRT and can be evaluated during the implantation procedure.
☆ Disclosures: Maurizio Malacrida is an employee of Boston Scientific, Inc. No other conflicts of interest exist. ⁎ Corresponding author at: Laboratorio di Elettrofisiologia, Clinica Mediterranea, Via Orazio 2, 80100 Napoli, Italy. Tel.: +39 0817259641; fax: +39 0817259777. E-mail address:
[email protected] (G. Stabile).
The aim of our study was to evaluate the geometrical characteristics of interventricular electrical delay in an unselected population of patients with left bundle branch block (LBBB) undergoing CRT. The design of the study has been published previously [6]. The study protocol was approved by the local institutional Ethics Committee and all patients provided written informed consent. At the end of the implantation procedure, the electrical inter-lead distance (EID), defined as the time interval between spontaneous peak R-waves of the same QRS complex detected at the RV and LV pacing sites, was automatically measured by the device and printed on an electrocardiographic recording. Among them in 240 patients the geometrical distance between RV and LV leads was determined on chest X-rays in postero-anterior and lateral views, at maximal inspiration, typically on the day after device placement. The inter-lead distance (ID) was measured on a digital radiology workstation, together with the thoracic and cardiac widths. The ID values were divided by the cardio-thoracic ratio in order to take into account the relative differences in cardiac and thoracic sizes among patients, thus providing corrected inter-lead distances (CID): the direct (DCID) and the horizontal (HCID) corrected RV–LV electrode tip separation [4]. The final LV lead tip position was designated as either anterior, anterolateral, lateral, posterolateral, or posterior (LAO projection), and basal, mid, or apical (RAO projection). Table 1 shows the clinical parameters of the 447 study patients. The mean EID was 76 ± 37 ms, with higher values in patients who received a septal RV lead than in those who received an apical RV lead (81 ± 37 ms versus 73 ± 37 ms, p = 0.035). Similarly, lateral (82 ± 36 ms) and posterior/posterolateral (83 ± 33 ms) LV lead positions were associated with longer EID than was an anterior/anterolateral position (56 ± 38 ms, both p b 0.001). No significantly different EID were observed among basal, mid and apical LV lead positions. Moreover, we found that a wider QRS was associated with longer EID: 85 ± 40 ms in
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Please cite this article as: Stabile G, et al, Geometrical characteristics of interventricular electrical delay, Int J Cardiol (2014), http://dx.doi.org/ 10.1016/j.ijcard.2013.12.206
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Table 1 Demographics and baseline inter-lead parameters of the study population. Parameter
n = 447
Male gender, n (%) Age, years Ischemic etiology, n (%) QRS duration, ms NYHA class • Class I–II, n (%) • Class III–IV, n (%) Hypertension, n (%) Diabetes, n (%) COPD, n (%) Chronic kidney disease, n (%) Echocardiographic data • LV ejection fraction, % • LVEDV, ml • LVESV, ml • LVEDD, mm • LVESD, mm • Mitral regurgitation grade ≥ 3, n (%)
317 (71) 70 ± 10 183 (41) 158 ± 25 174 (39) 273 (61) 264 (59) 125 (28) 100 (21) 103 (23) 29 ± 7 205 ± 72 150 ± 63 65 ± 9 54 ± 11 210 (47)
patients with QRS N 158 ms (mean value of the study population) versus 69 ± 34 ms (p b 0.001) in patients with QRS ≤158 ms. The mean cardio-thoracic ratio was 0.54 ± 0.09, with a DCID of 155 ± 53 mm and HCID of 126 ± 67 mm. We observed no difference in DCID and HCID between patients with apical and septal RV leads but, as expected, we found shorter HCID with anterior/anterolateral (101 ± 79 mm) than with lateral (133 ± 66 mm, p = 0.006) and posterior/posterolateral LV lead positioning (136 ± 68 mm, p = 0.017). On adopting the mean values of CID as cut-off values, we found that longer EID were associated with HCID N 126 mm (87 ± 38 ms versus 63 ± 35 ms in patients with HCID b 126 mm, p b 0.001) and with DCID N 155 mm (84 ± 39 ms versus 64 ± 35 ms in patients with DCID b 155 mm, p b 0.001). Similarly, in patients with EID N76 ms (mean value of the study population) HCID was 148 ± 70 mm and DCID was 166 ± 55 mm versus 104 ± 63 mm and 143 ± 52 mm (both p b 0.001), respectively, in patients with EID b 76 ms. Despite this association, on using a linear regression through the method of least squares, no correlation was found between EID and CIDs in the overall population or in any subgroup. The importance of pacing lead positioning in CRT has been extensively commented on in the literature, and several variables have been proposed to identify optimal lead locations in order to improve CRT response [1]. Unfortunately, most of these variables are difficult to collect, their usefulness has not been confirmed and, above all, they do not take into account the anatomical and technical difficulties that may be en-
countered during CRT implantation. Both CIDs and EID can be easily measured during implantation, and have been demonstrated to correlate with the response to CRT [4,5]. In particular, the electrical delay used in the present analysis has the advantage of being automatically measured by means of the pacing system analyzer or the defibrillator. Although we found an association between longer CIDs and greater EID, we did not find a correlation between them. Thus, these two variables are not fully interchangeable, and maximizing CID on implantation will not ensure optimal EID and vice versa. This might be explained by the consideration that many other factors, besides the lead position, may impact the overall electrical delay. The electrical activation pattern is different among patients with similar LBBB morphology, suggesting that an optimal anatomic site may not reflect the site with maximal electrical delay [7]. Indeed, myocardial substraterelated factors (e.g. presence of scarring) may impact the electrical activation pattern and explain our findings. A long electrical delay may represent either delayed overall electrical activation of that segment or slow conduction through a region of LV scar [8,9]. Our findings seem to suggest that a large variability in LV activation exists among CRT candidates, although the conventional lateral or postero-lateral LV segments might be preferred for lead positioning, as they are generally areas of late activation. The LV pacing site that potentially yields the best resynchronization is specific to each patient and is not predicted by anatomical position. However, the association between successful long-term CRT and pacing at the most delayed site remains to be proved by prospective studies. References [1] Auricchio A, Prinzen F. Non-responders to cardiac resynchronization therapy. The magnitude of the problem and the issues. Circ J 2011;75:521–7. [2] Cowburn PJ, Leclercq C. How to improve outcomes with cardiac resynchronization therapy: importance of lead positioning. Heart Fail Rev 2012;17:781–9. [3] Leon AR. Practical issues in cardiac resynchronization therapy device implantation. Rev Cardiovasc Med 2004;4:142–9. [4] Buck S, Maass AH, Nieuwland W, Anthonio RL, Van Veldhuisen DJ, Van Gelder IC. Impact of interventricular lead distance and the decrease in septal-to-lateral delay on response to cardiac resynchronization therapy. Europace 2008;10:1313–9. [5] D'Onofrio A, Botto GL, Mantica M, et al. The interventricular conduction time is associated with response to cardiac resynchronization. Int J Cardiol 2013;168:5067–8. [6] Stabile G, Bertaglia E, Botto GL, et al. Cardiac Resynchronization Therapy MOdular REgistry (CRT MORE): ECG and Rx predictors of response to CRT. J Cardiovasc Med 2013;14:886–93. http://dx.doi.org/10.2459/JCM.0b013e3283644bb2. [7] Auricchio A, Fantoni C, Regoli F, et al. Characterization of left ventricular activation in patients with heart failure and left bundle-branch block. Circulation 2004;109:1133–9. [8] Peichl P, Kautzner J, Cihak R, Bytesnik J. The spectrum of inter- and intraventricular conduction abnormalities in patients eligible for cardiac resynchronization therapy. Pacing Clin Electrophysiol 2004;27:1105–12. [9] Singh JP, Fan D, Heist EK, et al. Left ventricular lead electrical delay predicts response to cardiac resynchronization therapy. Heart Rhythm 2006;3:1285–92.
Please cite this article as: Stabile G, et al, Geometrical characteristics of interventricular electrical delay, Int J Cardiol (2014), http://dx.doi.org/ 10.1016/j.ijcard.2013.12.206
