Introduction: Nowadays the benefit and preferable spot of septal RV pacing is still controversial and not well established. Our aim was to investigate a correlation between QRS duration and position of electrode in the septum in bradyarrhythmic RV pacing depending on relative septum wall thickness (RSWT) evaluation.
Methods: During the period of 2 years 56 patients with bradyarrhythmias were involved into investigation (age 72±8 yrs, 43% males (n=24)). In a month after pacemaker implantation we assessed QRS duration on ECG (KhAI Medica, Kharkiv, Ukraine) and the location of RV lead by conventional EchoCG (Cypress, Siemens, Germany) using standard and intermediate oblique echo views. Data received from EchoCG was decisive in determination of RV lead location with accepting for further analysis leads in septum area, including RVOT (21%, n=12), mid- (54%, n=30) and low (25%, n=14) positions. We assessed RSWT in place of lead implantation by equation RSWT=h/H (described on the picture), where (h) – septum thickness in the place of interest, (H) - average septum thickness, calculated as H=S/L, where (S) - septum square determined by planimetry, (L) - septum longest longitudinal dimension.
Results: According to our data in 39% of patients (n=22) the thinner part of septum localized in the border of mid and low parts. In 48% of patients (n=27) the thickest place was in the high septum. In 16% of patients (n=9) septum has approximately equal width throughout. Average QRS duration was 155±17ms in RVOT, 143±15ms in mid-septum and 152±18ms in low-septum. In patients with lead implanted in the thinnest part of the septum (RSWT = 1.05, 55%, n=31) duration of QRS was significantly shorter than those with RSWT > 1.05 (45%, n=25) – 142±15 ms vs. 153±17 ms (p – 0.07).
Conclusions: Placing RV lead into the thinner part of interventricular septum tends to shorten paced QRS duration. RVOT in most cases in our group was not optimal pacing site because of anatomical features (thicker septum with longer paced QRS) that would contradict the common approach taken to physiological pacing in some studies.