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(Circulation. 2008;117:e196.)
© 2008 American Heart Association, Inc.

Correspondence

Letter by Naqvi and Motallebi Regarding Article, "Left Ventricular Resynchronization Is Mandatory for Response to Cardiac Resynchronization Therapy"

Tasneem Z. Naqvi, MD, FRCP

Echocardiography Laboratory, Department of Clinical Medicine, University of Southern California, Los Angeles

Mazda Motallebi, MD

Department of Cardiology, University of Southern California, Los Angeles

To the Editor:

Bleeker et al¹ propose that in patients selected on the basis of both electrical and a single mechanical dyssynchrony measure derived from maximum delay during left ventricular (LV) ejection between peak systolic velocities among 4 basal LV segments, immediate resynchronization (of at least 20%) after cardiac resynchronization treatment (CRT) predicts reduction in LV end-systolic volume by at least 10% at 6-month follow-up. The editorial accompanying the article by Bleeker and colleagues² appropriately "cautions" against relying on a single "dyssynchrony" measure and on "early resynchronization" as predictors of reduction in LV volume. A number of single-center studies reported impressive CRT results based on mechanical rather than electrical dyssynchrony criteria. These results have not been reproducible however. The multicenter Predictors of Response to Cardiac Resynchronization Therapy (PROSPECT) study found that individual mechanical dyssynchrony variables added only 11% to 13% response to the clinical composite score and 13% to 23% to LV end-systolic volume.³ Interestingly, septolateral delay did not predict clinical response to CRT.³ Data on the number of patients with traditional CRT criteria screened to get 100 eligible patients in Bleekers study are lacking.¹ Feasibility of mechanical dyssynchrony measurement from lack of measurable peak during ejection or double or variable peaks between cardiac cycles is not reported. The discussion of intersegmental delay does not provide data on the location of delay. Is it the lateral wall, inferior wall, anterior wall, or inferior interventricular septum? Previous work has shown that those with delay in the interventricular septum respond less favorably to CRT.⁴ No data on the type of bundle-branch block or on heart rate between responders and nonresponders are provided. Is intersegmental delay of 65 ms in someone with a heart rate of 90 bpm of the same significance as in someone with a heart rate of 70 bpm? On the basis of this group’s earlier study,⁵ a significant number of patients, particularly those with an ischemic pathogenesis, should have transmural scar that would have precluded early resynchronization and hence response to CRT, despite the presence of mechanical dyssynchrony. It therefore appears rather simplistic that evaluation of dyssynchrony in the longitudinal direction alone using a method with technical limitations in a mixed cohort of ischemic and nonischemic patients without evaluation of myocardial viability or scar could be sufficient in predicting a very high response rate. In addition, data on immediate post-CRT LV ejection fraction and volumes are not reported. Early resynchronization could have been a secondary phenomenon related to an immediate improvement in LV systolic function and size. Thus, early resynchronization merely picked up patients who responded early and were destined to continue to respond later.

	References

Top References

 
1. Bleeker GB, Mollema SA, Holman ER, Van de Veire N, Ypenburg C, Boersma E, van der Wall EE, Schalij MJ, Bax JJ. Left ventricular resynchronization is mandatory for response to cardiac resynchronization therapy: analysis in patients with echocardiographic evidence of left ventricular dyssynchrony at baseline. Circulation. 2007; 116: 1440–1448.[Abstract/Free Full Text]

2. Kass DA. Highlighting the R in CRT. Circulation. 2007; 116: 1434–1436.[Free Full Text]

3. Ghio S, Chung ES, Leon AR, Tavazzi L, Sun JP, Nihoyannopoulos p, Merlino J, Abraham WT, Leclercq C. Results of the Predictors of Response to CRT (PROSPECT) Trial. Paper presented at: European Society of Cardiology Congress; September 4, 2007; Vienna, Austria.

4. Murphy RT, Sigurdsson G, Mulamalla S, Agler D, Popovic ZB, Starling RC, Wilkoff BL, Thomas JD, Grimm RA. Tissue synchronization imaging and optimal left ventricular pacing site in cardiac resynchronization therapy. Am J Cardiol. 2006; 97: 1615–1621.[CrossRef][Medline] [Order article via Infotrieve]

5. Bleeker GB, Kaandorp TA, Lamb HJ, Boersma E, Steendijk P, de Roos A, van der Wall EE, Schalij MJ, Bax JJ. Effect of posterolateral scar tissue on clinical and echocardiographic improvement after cardiac resynchronization therapy. Circulation. 2006; 113: 969–976.[Abstract/Free Full Text]

This Article Extract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Naqvi, T. Z. Articles by Motallebi, M. Search for Related Content PubMed Articles by Naqvi, T. Z. Articles by Motallebi, M. Related Collections Pacemaker Echocardiography