International Heart Journal
Online ISSN : 1349-3299
Print ISSN : 1349-2365
ISSN-L : 1349-2365
Letter to Editor
Reply to Letter Regarding Article, “Improvement of Cardiac Function by Increasing Stimulus Strength during Left Ventricular Pacing in Cardiac Resynchronization Therapy”
Kohei IshibashiTakashi KuboHironori KitabataShigeho TakaradaKunihiro ShimamuraTakashi TanimotoMakoto OriiYasutsugu ShionoTakashi YamanoYasushi InoTomoyuki YamaguchiKumiko HirataAtsushi TanakaToshio ImanishiTakashi Akasaka
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2015 Volume 56 Issue 5 Pages 580

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Abstract

We thank Cacko, et al for their interest in our clinical study article,1) which describes increasing stimulus strength (SS) of left ventricular (LV) pacing in cardiac resynchronization (CRT) improves LV mechanical dyssynchrony and cardiac function. Moreover, we would like to congratulate them for achieving improvement of cardiac function in their two patients with ischemic cardiomyopathy (ICM) who were not responding to CRT.
There are 2 types of LV electrical activation with a line of block in patients with left bundle branch block (type I pattern: homogenous spread from septum to lateral wall pattern, and type II pattern; presence of block with a subsequent U-shaped electrical activation pattern).2) Non-ischemic cardiomyopathy (NICM) patients are significantly more likely to have a type II pattern than ICM patients, and the presence of a type II pattern predicts a favorable response to CRT. The type I pattern is more frequent in ICM patients and may explain the lower response rates to CRT. The rates of CRT responders are lower in ICM patients because of the scarred myocardium.3) The scar tissue at the region of the LV lead inhibits effective pacing of myocardium.4) As increasing SS of LV pacing in CRT captures an enlarged myocardial area and provides a pacing response beyond a discrete region with conduction block, this optimization might be appropriate for ICM. Both patients of Cacko, et al were ICM patients and increasing SS of LV pacing seemed to be effective for them.
We believe that increasing the SS of LV pacing in CRT might be practical in the clinical setting despite the dramatic battery consumption. Multipoint LV pacing (MPP) can capture an enlarged myocardial area and improve LV mechanical dyssynchrony and cardiac function similar to high SS of LV pacing.5) However, almost all patients with CRT cannot use MPP therapy as MPP needs a special lead. Furthermore, MPP cannot necessarily stimulate myocardium beyond a conduction block area. Increasing SS of LV pacing is one useful optimization method for every CRT non-responder. Thus, we completely agree with their opinion and strongly recommend increasing the SS of LV pacing in CRT as one option for non-responders.
We would like to use increasing SS of LV pacing for appropriate patients in the clinical setting and evaluate the long-term prognosis to confirm the possible positive impact of increasing the SS of LV pacing on the response to CRT in a future study.

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© 2015 by the International Heart Journal Association
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