Paced QRS axis as a predictor of pacing-induced left ventricular dysfunction.
OBJECTIVE
The selection of the optimal right ventricular (RV) pacing site remains unclear. We hypothesized that a normal paced QRS axis would provide a physiological ventricular activation and lead to a better long-term outcome.


METHODS
We evaluated 187 patients who underwent a permanent pacemaker implantation and were dependent on RV pacing. The pacing sites were classified as the apex and non-apex according to the chest radiography. A paced QRS axis was defined as that between -30° and 90°. Preservation of the left ventricular (LV) systolic function was defined as that with a <10 % decrease in the ejection fraction after the pacemaker implantation.


RESULTS
The median follow-up period was 5.8 years (interquartile 3.9-9.0). Radiographically, the RV leads were located in the apex (n = 148, 79 %) or non-apex (n = 39, 21 %). In the electrocardiogram, normal paced and abnormal paced QRS axes were observed in 28 patients (15 %) and 159 patients (85 %), respectively. The LV ejection fraction was decreased in the patients with an abnormal paced QRS axis (-10 ± 10 %, P < 0.001), but not in those with a normal axis (0 ± 6 %, P = 0.80). The electrocardiographic determinant differentiated a preserved LV function (95 % vs. 35 %, log-rank P = 0.04). Among the patients with radiographically non-apical pacing, a normal paced QRS axis was an additional meaningful predictor of a preserved LV function after the pacemaker implantation (95 % vs. 24 %, log-rank P = 0.002).


CONCLUSIONS
Compared with the radiographic method, a normal paced QRS axis was associated with a preserved LV function.
Division of Cardiology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul St. Mary's Hospital, 222 Banpo-daero, Seocho-gu, Seoul, 137-701, South Korea.
Sung-Hwan
SH
Kim
Yong-Seog
YS
Oh
Gi-Byoung
GB
Nam
Kee-Joon
KJ
Choi
Jae Seok
JS
Park
Sang Weon
SW
Park
Seung-Jung
SJ
Park
Young Keun
YK
On
June Soo
JS
Kim
Woo-Seung
WS
Shin
Ji-Hoon
JH
Kim
Sung-Won
SW
Jang
Man Young
MY
Lee
You-Ho
YH
Kim
Tai-Ho
TH
Rho
D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D011379:Prognosis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000517:prevention & control*