Upgrade and de novo cardiac resynchronization therapy: impact of paced or intrinsic QRS morphology on outcomes and survival.
BACKGROUND
Cardiac resynchronization therapy (CRT) improves outcomes in patients with left bundle branch block (LBBB), but the benefits of CRT in patients with other QRS morphologies or previous pacing are uncertain.


OBJECTIVE
The purpose of this study was to describe outcomes in patients with prior right ventricular pacing and non-LBBB morphologies.


METHODS
We studied 505 patients who underwent de novo CRT (n = 338) or CRT upgrade (n = 167). De novo patients were categorized by underlying QRS morphology: LBBB (67%), right bundle branch block (RBBB; 11%), intraventricular conduction delay (IVCD; 13%), and QRS <120 ms (9%). Upgrade patients were categorized by the percentage of previous ventricular pacing.


RESULTS
Patients were followed for death over a median of 2.6 years (interquartile range 1.6-4.0). New York Heart Association (NYHA) functional class and echocardiographic improvements were similar in de novo and upgrade patients. However, within the de novo group, NYHA improvements were less in patients with RBBB (0.3 +/- 0.8; P = .014) or IVCD (0.2 +/- 0.7; P = .001) than in those with LBBB (0.7 +/- 0.8). These patients had less left ventricular functional improvement as well. Survival was comparable after de novo versus upgrade CRT (61% vs 63% at 4 years; P = .906). No clinical or survival differences were noted in upgrade patients based on the percentage of previous pacing. However, survival in de novo CRT recipients with RBBB (32%) was lower than in those with LBBB (66%; P <.001), and RBBB independently predicted death (hazard ratio 3.5, confidence interval 1.9-6.5; P <.001).


CONCLUSIONS
RBBB and IVCD result in less clinical improvement or worsened survival after CRT. Additional selection criteria may be beneficial in identifying potential responders with RBBB, IVCD, or narrow QRS.
Wokhlu
Anita
A
Mayo Clinic, Rochester, MN 55905, USA.
Rea
Robert F
RF
Asirvatham
Samuel J
SJ
Webster
Tracy
T
Brooke
Kelly
K
Hodge
David O
DO
Wiste
Heather J
HJ
Dong
Yingxue
Y
Hayes
David L
DL
Cha
Yong-Mei
YM
D000368:Aged; D001145:Arrhythmias, Cardiac / Q000401:mortality / Q000503:physiopathology*; D002037:Bundle-Branch Block / Q000401:mortality / Q000628:therapy; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System; D006333:Heart Failure / Q000503:physiopathology; D006801:Humans; D008297:Male; D011379:Prognosis; D016896:Treatment Outcome