A randomized comparison of fluoroscopic techniques for implanting pacemaker lead on the right ventricular outflow tract septum

The present study was a single-center randomized study performed from January 2013 to December 2014. Patients aged 18 years and older who had a standard indication for permanent pacemaker owing to symptomatic sick sinus syndrome or high degree atrioventricular block were included in this study. Patients were excluded before randomization if they met any of the following criteria: leads inserted into RV apex; indications for an implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy (CRT); clinical manifestations of congestive heart failure; chronic atrial fibrillation; moderate or greater degree of valvulopathy; chronic obstructive pulmonary disease; absence of informed content. All patients gave written consent to participate in the study before randomization. Patients were randomly assigned in a 1:1 ratio to two groups according to intraoperative fluoroscopic views: LL group (three standard fluoroscopic views + LL fluoroscopic view) or standard group (three standard fluoroscopic views). The randomization process was performed on the basis of numbered containers. The interventions (combined or not with use of LL fluoroscopic view) were sealed in the sequentially numbered opaque identical envelopes. The study protocol (20150814) was approved by the Institutional Ethics Committee.

Single-chamber and double-chamber pacemaker systems were performed by a group of operators experienced in RVOT septal lead placement. Prophylactic intravenous antibiotics were given half an hour before the procedure. Pacemaker implantation procedure was done under local anesthesia. The right ventricular (RV) lead was inserted via the left- or right-side subclavian venous approach. Commercially available 58 cm 7—French bipolar steroid-eluting active fixation lead (Capsure-Fix Novus 5076, Medtronic Inc., Minneapolis, MN, USA or Tendril ST 1888TC, St.Jude Medical Inc., St.Paul, MN, USA) was used for RV septal implants. Leads were inserted into RVOT septal position using a standard hand-shaped stylet as previously described by Mond et al. [11]. The style was fashioned with generous curve and a terminal straight bend with posterior angulation. First, the lead was initially advanced into the pulmonary artery guided by the posterior-anterior (PA) position. Afterwards, it was withdrawn slowly until the tip of lead was placed below the pulmonary valve on the RVOT. The 40º right anterior oblique (RAO) projection was used to prevent inadvertent positioning in the coronary sinus and great cardiac vein. RVOT septal lead positioning was determined once the 40º left anterior oblique (LAO) fluoroscopic view showed the lead tip pointing to the spine in the standard group (Fig. 2). The position of the lead in the RVOT septum was also confirmed by fluoroscopy using the LL fluoroscopic position in the LL group before helix deployment. Orientation of the lead tip was classified as anterior or posterior in the LL projection. A posterior projection of the lead towards the spine indicated septal placement (Fig. 3). If the RV lead from the LL group met the criteria for RVOT septum in 40° LAO projection, but not in the LL fluoroscopic view, the lead was retracted and advanced again to the pulmonary artery and the maneuver repeated. If this was not successful, the stylet sometimes had to be reshaped in case of difficult lead positioning, as the curves tended to straighten with time.

Once the tip of the RV lead made attachment with RVOT setptal positioning, the screw was deployed. The ventricular stimulation threshold at a pulse width of 0.48 ms, R-wave amplitude and lead impedance measurements were taken several minutes after screw deployment. Perioperative complications requiring intervention were recorded.

TTE presents an exact tool for assessing the exact anatomic location of pacing sites [12, 16, 17]. TTE was performed in all cases 3 days after pacemaker implantation by two observers who were blinded to the lead position. Disagreements between observers were resolved by consensus. Echocardiography was carried out with the subjects at rest in the left lateral decubitus position with a commercially available ultrasound transducer and equipment (S5-1 probe, Philips IE33, Ultrasound, Bothell, Washington, USA). 2D images were acquired from during end-expiratory held respiration and digitally stored at frame rates of 40–65 frames/second. The exact lead position, defined as the myocardium attachment site of the tip of RV lead, was documented using parasternal short-axis (PSAX) views. The correct location of the lead tip was the primary end point of the study. First, RVOT was displayed in PSAX views at the level of aortic valve. One part of the lead was seen within the RVOT. Then, the tip of RV lead was actively tracked using all available PSAX views. At last, the position of the lead was completely exposed and verified. We categorized the position of the leads into RVOT septum if the direction of the tip of the lead and its attachment site were seen to the plane of interventricular septum (Fig. 4).

A standard 12-lead ECG was recorded during forced ventricular pacing (VVI, 10 bpm above baseline ventricular rate) at a paper speed of 25 mm/s with chest and limb leads placed in standard positions. The ECG parameters derived from RVOT septal pacing and non-septal pacing were analyzed: (1) QRS duration, (2) presence of q-wave or negative QRS complex in lead I, (3) presence of QRS notching in the inferior leads, (4) QRS transition zone in the precordial leads. Transition zone was defined as the lead with R > (Q + S) amplitude.

Continuous variables are expressed as mean value ± standard deviation. Categorical variables were compared by Chi square test. Continuous variables showing normal distribution according to the Shapiro–Wilk test and histogram analysis were compared using Student’s t test between two groups. The Mann–Whitney U test was performed for comparing groups if variables did not follow the normal distribution. A two-tailed p value <0.05 was considered to be statistically significant. All statistical analyses were performed using SPSS 19.0 (SPSS, Inc., Chicago, IL, USA) for windows.

A total of 156 patients were enrolled in the study. Mean age of the entire patients was 59.2 ± 15.5 years. Patients were randomly assigned in a 1:1 ratio to two groups. We excluded 13 patients (6 LL group and 7 standard group patients) due to poor echocardiographic windows. Therefore, data from 143 patients (LL group: n = 72, standard group: n = 71) were finally analyzed.

Clinical variables in the LL and standard groups are shown in Table 1. There were no significant differences in age, gender, pacemaker type, pre-implantation QRS duration, comorbidities between the two groups. Furthermore, indications for pacemaker implantation were not statistically significant between the two groups. There were no significant differences in terms of preoperative echocardiographic data between the LL and standard groups.

Lead placement was successful in all cases, with no procedural complications. All tested parameters were within the normal acceptable range for these leads. No significant differences were observed in R-wave amplitude, RV lead impedance, pacing threshold and fluoroscopy time. There was no statistically significant difference in paced QRS duration in patients between LL group compared with standard group (143.8 ± 20.9 vs. 147.2 ± 18.2 ms, p = 0.35) (Table 2).

TTE of sufficient quality for confirmation of RVOT pacing sites was available in 72 patients in the LL group and 71 patients in the standard group. In the LL group, 60 patients (83 %) were achieved in RVOT septal position. Of the remaining 12 patients, the leads were anchored in the anterior wall in 4 (33 %) and in the free wall in the 8 (67 %). In the standard group, RVOT septal position was observed in 48 patients (68 %). Furthermore, 19 (83 %) patients were classified as being positioned on the anterior wall and 4 (17 %) as being on the free wall. There were significant differences in RVOT septal pacing between the LL and standard groups (p = 0.029). The position of RVOT anterior wall in LL group was significantly less than standard group (p = 0.001). No significant difference in RVOT free wall pacing was shown between 2 groups (p = 0.239) (Table 3).

The ECG characteristics are shown in Table 4. RVOT septal pacing was associated with a shorter QRS duration compared with RVOT non-septal pacing (p = 0.015). QRS vector in lead I was found more frequently negative voltage in septal pacing than in non-septal pacing (p < 0.001). There was no significant difference in the presence of notching of QRS complex in inferior leads or QRS transition zone.

We did not use cardiac computed tomography to confirm the lead position. It was not available in sufficient numbers of patients enrolled in the present study. We did not perform a clinical follow-up. A clinical follow-up, including echocardiography to evaluate LV function and dyssynchrony of groups with leads in different RVOT positions should be the next step.