Clinical research
Long-term effectiveness of cardiac resynchronization therapy in patients with refractory heart failure and “narrow” QRS

https://doi.org/10.1016/j.jacc.2003.08.024Get rights and content
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Abstract

Objectives

The aim of the study was to evaluate the effectiveness of cardiac resynchronization therapy (CRT) in patients with refractory heart failure (HF) and incomplete left bundle branch block (“narrow” QRS), together with echocardiographic evidence of interventricular and intraventricular asynchrony.

Background

Cardiac resynchronization therapy has been proven effective in patients with HF and wide QRS by ameliorating contraction asynchrony.

Methods

Fifty-two patients with severe HF received biventricular pacing. The patients were eligible in the presence of echocardiographic evidence of interventricular and intraventricular asynchrony, regardless of QRS duration. The patient population was divided into group 1 (n = 38), with a QRS duration >120 ms, and group 2 (n = 14), with a QRS duration ≤120 ms.

Results

The baseline parameters considered in the study were similar in both groups. At follow-up, CRT determined narrowing of the QRS interval in the entire population and in group 1 (p < 0.001), whereas a small increase in QRS duration was observed in group 2 (p = NS); in all patients and within groups, we observed improvement of New York Heart Association functional class (p < 0.001 in all), left ventricular ejection fraction (p < 0.001 in all), left ventricular end-diastolic and end-systolic diameter (p < 0.05 within groups), mitral regurgitation area (p < 0.001 in all), interventricular delay (p < 0.001 in all), and deceleration time (group 1: p < 0.001, group 2: p < 0.05), with no significant difference between groups. The 6-min walking test improved in both groups (group 1: p < 0.001; group 2: p < 0.01).

Conclusions

Cardiac resynchronization therapy determined clinical and functional benefit that was similar in patients with wide or “narrow” QRS. Cardiac resynchronization therapy may be helpful in patients with echocardiographic evidence of interventricular and intraventricular asynchrony and incomplete left bundle branch block.

Abbreviations

ACE
angiotensin-converting enzyme
AV
atrioventricular
CRT
cardiac resynchronization therapy
DCM
dilated cardiomyopathy
DT
deceleration time
E-A
left ventricular filling time
ECG
electrocardiogram
EF
ejection fraction
HF
heart failure
IVD
interventricular delay
LBBB
left bundle branch block
LVEDD
left ventricular end-diastolic diameter
LVESD
left ventricular end-systolic diameter
MR
mitral regurgitation
NYHA
New York Heart Association
PM
pacemaker
SR
sinus rhythm
Q-E
Q-wave–transmitral filling E-wave interval
Q-LW
posterolateral left ventricular wall activation delay
6MWT
6-min walking test

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