IJCS | Volume 31, Nº2, March / April 2018

DOI: 10.5935/2359-4802.20170100 193 International Journal of Cardiovascular Sciences. 2018;31(2)193-195 CASE REPORT Mailing Address: Michel Cabrera Ortega Calle 100 y Perla, Postal Code: 10800. Altahabana. Boyeros. La Habana, Boyeros – Cuba E-mail: michel@cardiows.sld.cu; anrossca@yahoo.es Improvement of Pacing-Induced Dyssynchrony by Right Ventricular Septal Stimulation in a Child with Tetralogy of Fallot Alexander González Guillen, Michel Cabrera Ortega, Francisco Díaz Ramírez, Dunia Bárbara Benítez Ramos Cardiocentro Pediátrico "William Soler", Boyeros, Havana – Cuba Manuscript received February 02, 2017; revised manuscript June 05, 2016; accepted July 07, 2017 Heart Defects, Congenital; Tetralogy of Fallot / surgery; Atrioventricular Block; Ventricular Dysfunction, Right; Cardiac Resynchronization Therapy. Keywords Introduction Complete atrioventricular block (CAVB) is not an uncommon complication after surgical correction of tetralogy of Fallot (TOF). The choice of the ventricular pacing site in patients requiring pacemaker therapy depends on factors such as age, weight, presence of a venous anomaly, and intracardiac short -circuit. The harmful effects of ventricular pacing are most pronounced during right ventricular (RV) stimulation. Even then, RV pacing sites have been determined to be optimal in some patients with and without congenital heart disease. 1 Case report A 4-year-old boy with a history of surgically repaired TOF had a single-chamber pacemaker with rate response mode (VVIR) implanted in the left ventricular (LV) epicardium due to a postoperative CAVB (Figure 1a). During LV pacing, the electrocardiogram (ECG) demonstrated an increased QRS complex duration and a marked right bundle-branch block (RBBB) pattern with negative paced QRS complexes in inferior leads (Figure 1b). Subsequent echocardiographic evaluations showed interventricular and right intraventricular dyssynchrony, which was associated with progressive RV dilatation. After 1 year of ventricular pacing, the patient developed RV dysfunction with a fractional area change (FAC) of 28% and a tricuspid annular plane systolic excursion (TAPSE) of 12 mm. Furthermore, two‑dimensional strain reflected an RV dyssynchrony index of 56 msec, with the worse QS delay at the RV mid-septum (195 msec). Considering the beneficial effects of septal stimulation, 1,2 the patient underwent lead and pacemaker replacement. An active ventricular lead (Medtronic CapSureFix, Medtronic Limited, Watford, UK) was fixed in the RV mid-septum (Figure 2), obtaining appropriate sensing and pacing thresholds. Following single-site RV midseptal pacing, a 12-lead surface ECG revealed a shorter duration of the QRS complex and a left bundle-branch block pattern with positive paced QRS complexes in inferior leads. Additionally, there was an immediate decrease in interventricular dyssynchrony to 31 msec and RV dyssynchrony index to 27 msec. An echocardiographic assessment showed an increase in FAC (39%) and TAPSE (15 mm), with a reduction in the RV diameters 3 months after the therapy. Discussion The LV is the optimal pacing site in the pediatric population. 3 However, Karpawich et al. 1 demonstrated that the optimal lead implantation site varies among patients and congenital heart diseases (CHD). In our case, LV pacing produced a dyssynchronous RV contraction, evidenced by an increasedQRS duration and echocardiographic parameters. Correction of TOF is often followed by RV conduction delay and RBBB. A study in an animal model of repaired TOF evidenced the activation sequence relatedwith RBBB, first with activation of the basolateral LV region and last withactivationof the areaof theRVfreewall. 4 Moreover, LV pacing enhances a baselineRBBB, and the delayed electrical activation observed may induce a dyssynchronous RV contraction with a negative impact on the RV function.