CLINICAL RESEARCH: HEART FAILURE TREATMENT
Benefits of Cardiac Resynchronization Therapy for Heart Failure Patients With Narrow QRS Complexes and Coexisting Systolic Asynchrony by Echocardiography
Cheuk-Man Yu, MD, FRCP*,*,
Yat-Sun Chan, FHKAM*,
Qing Zhang, MM*,
Gabriel W.K. Yip, MRCP*,
Chi-Kin Chan, FHKAM ,
Leo C.C. Kum, MRCP*,
LiWen Wu, BM*,
Alex Pui-Wai Lee, MRCP*,
Yat-Yin Lam, MRCP* and
Jeffrey Wing-Hong Fung, FHKAM*
* Division of Cardiology, S. H. Ho Cardiovascular and Stroke Centre, Institute of Vascular Medicine, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
Department of Medicine, Alice Ho Miu Ling Nethersole Hospital, Hong Kong, China.
Manuscript received May 8, 2006;
revised manuscript received July 14, 2006,
accepted July 17, 2006.
* Reprint requests and correspondence: Prof. Cheuk-Man Yu, Division of Cardiology, S. H. Ho Cardiovascular and Stroke Centre, Institute of Vascular Medicine, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China. (Email: cmyu{at}cuhk.edu.hk).
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Abstract
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OBJECTIVES: This study was designed to evaluate the role of cardiac resynchronization therapy (CRT) in heart failure (HF) patients with narrow QRS complexes (<120 ms) and echocardiographic evidence of mechanical asynchrony.
BACKGROUND: Cardiac resynchronization therapy is currently recommended to advanced HF patients with prolonged QRS duration. Echocardiographic assessment of systolic mechanical asynchrony has been proven useful to predict a favorable response after CRT.
METHODS: A total of 102 HF patients with New York Heart Association (NYHA) functional class III or IV were enrolled. Among them, 51 had wide QRS (>120 ms) and 51 had narrow QRS (<120 ms). Tissue Doppler imaging (TDI) was employed to select patients with systolic asynchrony (increased asynchrony index) in the narrow-QRS group. Clinical and echocardiographic assessments were performed at baseline and 3 months after CRT.
RESULTS: There was a significant reduction of left ventricular (LV) end-systolic volume in both narrow (122 ± 42 cc vs. 103 ± 47 cc, p < 0.001) and wide (148 ± 74 cc vs. 112 ± 64 cc, p < 0.001) QRS groups. Improvement of NYHA functional class (both p < 0.001), maximal exercise capacity (both p < 0.05), 6-min hall-walk distance (both p < 0.01), ejection fraction (both p < 0.001), and mitral regurgitation (both p < 0.005) was also observed. In both groups, the degree of baseline mechanical asynchrony determined LV reverse remodeling to a similar extent, as shown by the superimposed regression lines. Withholding CRT for 4 weeks resulted in loss of echocardiographic benefits.
CONCLUSIONS: Cardiac resynchronization therapy for HF patients with narrow QRS complexes and coexisting mechanical asynchrony by TDI results in LV reverse remodeling and improvement of clinical status. The amplitude of benefit is similar to the wide-QRS group provided that similar extent of systolic asynchrony is selected.
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Abbreviations and Acronyms
| | CRT = cardiac resynchronization therapy | | HF = heart failure | | LV = left ventricular | | NYHA = New York Heart Association | | ROC = receiver-operating characteristic | | TDI = tissue Doppler imaging |
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Cardiac resynchronization therapy (CRT) is an established therapy for patients with chronic heart failure (HF) with wide QRS complexes (1–3) . Left ventricular (LV) reverse remodeling is an objective structural end point that heralds improved long-term survival (4). However, about 30% to 40% of patients with wide QRS do not respond to the therapy (1,4–6). Echocardiographic assessment of systolic mechanical asynchrony was found useful to predict a favorable LV reverse remodeling response and therefore is a potentially important adjunctive tool for selecting appropriate patients for CRT (5,6).
Previous studies have shown that systolic asynchrony was present in 27% to 43% of HF patients with narrow QRS complexes (defined as <120 ms) (7,8). Therefore, CRT may have therapeutic potential to those with narrow QRS complexes and systolic asynchrony by echocardiography. The current study: 1) sought to determine whether CRT induces LV reverse remodeling and improves clinical status in patients with narrow QRS complexes who had coexisting systolic asynchrony by echocardiography, and 2) compared its efficacy with that in patients with wide QRS complexes. The effect of withholding CRT was also examined.
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Methods
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Patients.
This study consisted of 102 optimally treated HF patients (mean age: 65 ± 12 years, 75% men) in New York Heart Association (NYHA) functional class III (n = 87) or IV (n = 15) who had an ejection fraction <40%, received CRT, and were followed up for at least 3 months. There were 51 patients with QRS duration <120 ms (narrow-QRS group) with predefined systolic asynchrony by echocardiography. The wide-QRS group consisted of 51 patients with QRS duration >120 ms with conventional electrocardiographic selection criteria alone for CRT. All patients received a biventricular pacemaker (Guidant Inc., St. Paul, Minnesota, or Medtronic Inc., Minneapolis, Minnesota). Serial clinical assessments and echocardiographic examinations were performed before and 3 months after CRT as well as after withholding pacing for 4 weeks. Clinical assessments included NYHA functional class, 6-min hall-walk test, Minnesota Living With Heart Failure Questionnaire for quality of life, and maximal metabolic equivalent achieved on treadmill test by Chronotropic Assessment Exercise Protocol (9). This study protocol was approved by our local ethics committee, and written informed consent was obtained from all patients. The primary end point was LV reverse remodeling as reflected by a decrease in LV end-systolic volume. Secondary end points included clinical parameters and change in LV ejection fraction. To detect a 30-cc or 20% reduction in LV end-systolic volume with an SD of measurement of 55 cc and a statistical power of 80%, 27 patients in each group were needed to allow for 2-sided alpha of 0.05.
Echocardiographic assessment of cardiac function.
Standard echocardiography was performed (Vivid 7, Vingmed-General Electric, Horten, Norway). The LV volumes and ejection fraction were assessed by biplane Simpson’s equation (10). The LV +dp/dt, mitral regurgitation, myocardial performance index, and sphericity index were measured (5).
Tissue Doppler imaging (TDI) was performed using apical 4-chamber, 2-chamber, and long-axis views for long-axis motion of the LV (EchoPac-PC [BT-05], Vingmed-General Electric, Horten, Norway) (6,10,11). Systolic asynchrony was assessed by calculating the standard deviation of the time to peak systolic velocity in ejection phase of the 12 LV segments (asynchrony index) (5,6,11), and the cutoff value was 32.6 ms. It was predetermined that about one-half of the patients enrolled in the narrow-QRS group had significant systolic asynchrony (asynchrony index  32.6 ms) and the other half had no significant asynchrony (asynchrony index 15 to <32.6 ms). This would provide further information to examine the importance of before-treatment systolic asynchrony in predicting a favorable response and allow parallel comparison with the wide-QRS group.
Statistical analysis.
The comparison of parametric variables before and after CRT was performed by paired-sample t test. The comparison of clinical and echocardiographic parameters between wide- and narrow-QRS groups was performed by unpaired t test or Pearson chi-square test where appropriate. Pearson correlation analysis was used to examine the relationship between before-pacing systolic asynchrony and the change of LV end-systolic volume after CRT. Stepwise multivariate regression analysis was employed to examine predictors of LV reverse remodeling using the change of LV end-systolic volume as the dependent covariate. Receiver-operating characteristic (ROC) curves were analyzed for asynchrony index in predicting LV reverse remodeling. The sensitivity and specificity of best-performing cutoff values were examined in both groups. Data were expressed as mean values ± SD. A p value <0.05 was considered statistically significant.
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Results
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There was no difference in age, gender, or etiologies of HF between the narrow- and wide-QRS groups (Table 1). However, the narrow-QRS group had less severe clinical status and smaller LV volume at baseline. There was no difference in optimized atrioventricular interval (102 ± 30 ms vs. 98 ± 34 ms, p = NS).
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Table 1. Comparison of Baseline Clinical and Echocardiographic Parameters Between Heart Failure Patients With Narrow and Wide QRS Complexes
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LV function and reverse remodeling.
Left ventricular reverse remodeling, together with improvement in myocardial performance index, mitral regurgitation, and diastolic filling time, was evident in both groups (Tables 2 and 3). There was no difference between the 2 groups in improvement of echocardiographic parameters, except that the reduction of LV end-diastolic volume was greater in the wide-QRS group (Table 4). When pacing was withheld for 4 weeks, the echocardiographic benefits of CRT disappeared in both groups (Tables 2 and 3).
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Table 2. Comparison of Clinical and Echocardiographic Parameters at Baseline, After Cardiac Resynchronization Therapy for 3 Months, and After Off Pacing for 4 Weeks for Heart Failure Patients With Narrow QRS Complexes
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Table 3. Comparison of Clinical and Echocardiographic Parameters at Baseline, After Cardiac Resynchronization Therapy for 3 Months, and After Off Pacing for 4 Weeks for Heart Failure Patients With Wide QRS Complexes
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Table 4. Comparison of the Changes in Clinical and Echocardiographic Parameters After Cardiac Resynchronization Therapy for Heart Failure Patients With Narrow and Wide QRS Complexes
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Clinical assessment.
In both groups, CRT resulted in significant improvement in most clinical parameters, except for quality of life (Tables 2 and 3). The amplitude of improvement in these clinical parameters was similar, with the exception of quality of life, which was improved only in the wide-QRS group (p < 0.001) (Table 4). When pacing was withheld for 4 weeks, there was no significant change in clinical parameters in both groups (Tables 2 and 3).
Comparison of relationship between changes in LV systolic asynchrony and the degree of reverse remodeling in narrow- and wide-QRS groups.
There was significant correlation between before-pacing systolic asynchrony index and changes in LV end-systolic volume in both groups, as shown in Figure 1. Furthermore, the regression lines of these 2 groups superimpose on each other with nearly identical slopes (narrow: –0.46 ± 0.09 vs. wide: –0.42 ± 0.06) and Y-intercept (narrow: 28.10 ± 2.15 ms vs. wide: 28.00 ± 1.95 ms).
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Figure 1 Change in left ventricular (LV) end-systolic volume and severity of systolic asynchrony as measured by asynchrony index for heart failure patients with narrow (solid triangles) and wide (open triangles) QRS complexes. The regression lines for both groups nearly superimpose on each other with nearly identical slopes. Wide QRS: r = –0.71, p < 0.001; narrow QRS: r = –0.61, p < 0.001.
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The prevalence of "responders" was 62.7% (32 of 51) in the wide-QRS group and 45.1% (23 of 51) in the narrow-QRS group (chi-square = 3.20, p = 0.07), as defined by a reduction of LV end-systolic volume >15% (5,10,11). The areas under ROC curves were good for both narrow- and wide-QRS groups (Fig. 2). From the shoulders of the ROC curves, the cutoff values of asynchrony index for predicting LV reverse remodeling were the same (i.e., 32.7 ms), with high sensitivity and specificity. Figure 3
is an example of a CRT responder.
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Figure 2 The receiver-operating characteristics for identification of left ventricular reverse remodeling in heart failure patients with narrow (A) and wide (B) QRS complexes. The area under curve (AUC) is shown in each group.
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Figure 3 An example of a responder of cardiac resynchronization therapy (CRT) showing left ventricular (LV) reverse remodeling with reduction of LV end-systolic volume from 131 cc (A) to 78 cc (B) after CRT for 3 months. This patient had significant systolic asynchrony with asynchrony index (Ts-SD) of 41.0 ms at baseline. Tissue Doppler imaging showing great variations of time to peak systolic velocity (arrows) with delay in lateral wall at apical 4-chamber view (C), inferior wall at apical 2-chamber view (E), and posterior wall at apical long-axis (G) views. Such delay was abolished at the corresponding views after CRT for 3 months (D, F, and H). The asynchrony index was normalized to 21.4 ms.
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By multivariate analysis, Ts-SD was the only independent predictor of LV reverse remodeling in both narrow- (beta = –0.81, confidence interval = –0.49 to –1.12, p < 0.001) and wide-QRS groups (beta = –1.17, confidence interval = –0.75 to –1.59, p < 0.001).
Improvement of cardiac function in narrow QRS group stratified by asynchrony index.
Twenty-seven patients in the narrow-QRS group had significant systolic asynchrony. There was no difference in baseline clinical and echocardiographic characteristics between those with and without significant asynchrony. However, those with significant asynchrony had a greater extent of LV reverse remodeling than those without (all p < 0.001) (Fig. 4).
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Figure 4 Comparison of changes in left ventricular end-systolic volume (LVESV) (A), left ventricular end-diastolic volume (LVEDV) (B), and left ventricular ejection fraction (EF) (C) in heart failure patients with narrow QRS complexes with and without significant systolic asynchrony according to asynchrony index.
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Discussion
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This study revealed that CRT may be beneficial in selected patients with narrow QRS complexes. It illustrated that those patients with mechanical asynchrony detected by TDI had improvement in symptoms, exercise capacity and, most importantly, LV systolic function with reverse remodeling after CRT. Moreover, the echocardiographic benefits by CRT disappeared when pacing was withheld, further ascertaining the pacing-dependent nature of CRT benefits. Interestingly, for a similar extent of before-pacing systolic asynchrony, the degree of cardiac improvement is very similar to those with wide QRS complexes. This was corroborated by the finding that the improvement of cardiac structure was more dramatic in those with significant mechanical asynchrony among the narrow-QRS group.
Role of CRT for HF patients with narrow QRS complexes.
Cardiac resynchronization therapy is an established therapy for HF patients with wide QRS complexes (>120 ms), which signify the presence of LV electromechanical abnormality. However, previous studies observed that only 25% of HF patients had wide QRS complexes (12,13). On the other hand, mechanical asynchrony detected by echocardiography is present in up to 43% of HF patients with narrow QRS duration (<120 ms) (7,8,14). Therefore, the current selection criteria may have excluded a large proportion of patients who may potentially benefit from CRT (15). It is thus worthwhile to examine the role of CRT for those with narrow QRS complexes and systolic asynchrony.
In the wide-QRS group, CRT response is predicted by the degree of systolic asynchrony (5,16). This suggests that the presence of mechanical asynchrony rather than wide QRS is a major determinant of CRT benefits. The potential role of CRT in narrow-QRS patients was evaluated in 2 studies (17,18). Achilli et al. (17) examined 14 HF patients with narrow QRS complexes. Although there was improvement in clinical parameters and LV ejection fraction, degree of LV reverse remodeling was not measured (17). Turner et al. (18) reported an insignificant increase in ejection fraction in 8 patients with narrow QRS complex after CRT. However, both studies were limited by a small sample size. In particular, the latter study did not examine the presence of before-pacing systolic asynchrony and therefore resulted in the selection of patients with only mild to moderate systolic asynchrony when compared with the wide-QRS group (18).
The present study is the largest that examined comprehensively the clinical and echocardiographic benefits of CRT in HF patients with narrow QRS complexes. In particular, we examined the presence of systolic asynchrony prospectively by the use of validated parameters. A close relationship between systolic asynchrony and the degree of reverse remodeling was observed in these patients. Intriguingly, the degree of LV reverse remodeling was similar between the wide- and narrow-QRS groups if the extent of mechanical asynchrony was similar. This is illustrated by the nearly superimposed regression lines with nearly identical slopes as well as X- and Y-intercepts in both groups (Fig. 1). Therefore, this study reemphasized the importance of screening for intraventricular systolic asynchrony in narrow-QRS patients. Furthermore, the cutoff values for the asynchrony index derived from the ROC curves to predict a favorable reverse remodeling response were identical for both groups (32.7 ms), which is nearly identical to the value derived from a control population (32.6 ms) (12). This confirms the internal consistency and usefulness of employing the asynchrony index as a screening tool to detect systolic asynchrony irrespective of QRS duration.
Study limitations.
This study has a relatively small sample size and is a single-center experience. However, the sample size has adequate power to examine the occurrence of LV reverse remodeling as the primary end point and is the largest study of narrow-QRS patients to date. The result of the present study will also provide valuable reference information for the consideration of large, controlled, multicenter trials of CRT in narrow-QRS patient groups, which it is hoped will extend CRT benefits to a wider spectrum of HF patients. Although the use of 3 apical views to calculate asynchrony index appears to be complex, comprehensive assessment of underlying mechanical asynchrony is necessary to select the potential responders, as shown in the current study.
Conclusions.
This study illustrated that CRT benefits HF patients with narrow QRS complexes who had mechanical asynchrony as demonstrated by TDI. The extent of LV reverse remodeling after CRT benefit is similar to those with wide QRS complexes. Furthermore, the same cutoff value of asynchrony index appears useful to identify significant systolic asynchrony in both wide- and narrow-QRS groups.
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Footnotes
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This study was jointly supported by a research grant from Guidant Inc. and a direct grant from the Chinese University of Hong Kong (Ref 2003.1.061).
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References
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1. Abraham WT, Fisher WG, Smith AL, et al. Cardiac resynchronization in chronic heart failure N Engl J Med 2002;346:1845-1853.[Abstract/Free Full Text]2. St. John Sutton MG, Plappert T, Abraham WT, et al. Effect of cardiac resynchronization therapy on left ventricular size and function in chronic heart failure Circulation 2003;107:1985-1990. 3. Cleland JG, Daubert JC, Erdmann E, et al. The effect of cardiac resynchronization on morbidity and mortality in heart failure N Engl J Med 2005;352:1539-1549.[Abstract/Free Full Text] 4. Yu CM, Bleeker GB, Fung JW, et al. Left ventricular reverse remodeling but not clinical improvement predicts long-term survival after cardiac resynchronization therapy Circulation 2005;112:1580-1586. 5. Yu CM, Fung JWH, Lin H, Zhang Q, Sanderson JE, Lau CP. Predictors of left ventricular reverse remodeling after cardiac resynchronization therapy for heart failure secondary to idiopathic dilated or ischemic cardiomyopathy Am J Cardiol 2003;91:684-688.[CrossRef][Web of Science][Medline] 6. Yu CM, Fung JW, Zhang Q, et al. Tissue Doppler imaging is superior to strain rate imaging and postsystolic shortening on the prediction of reverse remodeling in both ischemic and nonischemic heart failure after cardiac resynchronization therapy Circulation 2004;110:66-73. 7. Bleeker GB, Schalij MJ, Molhoek SG, et al. Relationship between QRS duration and left ventricular dyssynchrony in patients with end-stage heart failure J Cardiovasc Electrophysiol 2004;15:544-549.[Web of Science][Medline] 8. Ghio S, Constantin C, Klersy C, et al. Interventricular and intraventricular dyssynchrony are common in heart failure patients, regardless of QRS duration Eur Heart J 2004;25:571-578.[Abstract/Free Full Text] 9. Yu CM, Lau CP, Cheung BM, et al. Clinical predictors of morbidity and mortality in patients with myocardial infarction or revascularization who underwent cardiac rehabilitation, and importance of diabetes mellitus and exercise capacity Am J Cardiol 2000;85:344-349.[CrossRef][Web of Science][Medline] 10. Yu CM, Chau E, Sanderson JE, et al. Tissue Doppler echocardiographic evidence of reverse remodeling and improved synchronicity by simultaneously delaying regional contraction after biventricular pacing therapy in heart failure Circulation 2002;105:438-445. 11. Yu CM, Zhang Q, Fung JW, et al. A novel tool to assess systolic asynchrony and identify responders of cardiac resynchronization therapy by tissue synchronization imaging J Am Coll Cardiol 2005;45:677-684.[Abstract/Free Full Text] 12. Yu CM, Lin H, Zhang Q, Sanderson JE. High prevalence of left ventricular systolic and diastolic asynchrony in patients with congestive heart failure and normal QRS duration Heart 2003;89:54-60.[Abstract/Free Full Text] 13. Farwell D, Patel NR, Hall A, Ralph S, Sulke AN. How many people with heart failure are appropriate for biventricular resynchronization? Eur Heart J 2000;21:1246-1250.[Abstract/Free Full Text] 14. Baldasseroni S, Opasich C, Gorini M, et al. Left bundle-branch block is associated with increased 1-year sudden and total mortality rate in 5517 outpatients with congestive heart failure: a report from the Italian Network on Congestive Heart Failure Am Heart J 2002;143:398-405.[CrossRef][Web of Science][Medline] 15. Kashani A, Barold SS. Significance of QRS complex duration in patients with heart failure J Am Coll Cardiol 2005;46:2183-2192.[Abstract/Free Full Text] 16. Bax JJ, Abraham T, Barold SS, et al. Cardiac resynchronization therapy: part 1—issues before device implantation J Am Coll Cardiol 2005;46:2153-2167.[Abstract/Free Full Text] 17. Achilli A, Sassara M, Ficili S, et al. Long-term effectiveness of cardiac resynchronization therapy in patients with refractory heart failure and "narrow" QRS J Am Coll Cardiol 2003;42:2117-2124.[Abstract/Free Full Text] 18. Turner MS, Bleasdale RA, Vinereanu D, et al. Electrical and mechanical components of dyssynchrony in heart failure patients with normal QRS duration and left bundle-branch block: impact of left and biventricular pacing Circulation 2004;109:2544-2549.
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J. F. Beshai, R. A. Grimm, S. F. Nagueh, J. H. Baker II, S. L. Beau, S. M. Greenberg, L. A. Pires, P. J. Tchou, and the RethinQ Study Investigators
Cardiac-Resynchronization Therapy in Heart Failure with Narrow QRS Complexes
N. Engl. J. Med.,
December 13, 2007;
357(24):
2461 - 2471.
[Abstract]
[Full Text]
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W.H. W. Tang and G. S. Francis
The Year in Heart Failure
J. Am. Coll. Cardiol.,
December 11, 2007;
50(24):
2344 - 2351.
[Full Text]
[PDF]
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C. Leclercq, G. B. Bleeker, C. Linde, E. Donal, J. J. Bax, M. J. Schalij, and C. Daubert
Cardiac resynchronization therapy: clinical results and evolution of candidate selection
Eur. Heart J. Suppl.,
December 1, 2007;
9(suppl_I):
I94 - I106.
[Abstract]
[Full Text]
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Authors/Task Force Members, P. E. Vardas, A. Auricchio, J.-J. Blanc, J.-C. Daubert, H. Drexler, H. Ector, M. Gasparini, C. Linde, F. B. Morgado, et al.
Guidelines for cardiac pacing and cardiac resynchronization therapy: The Task Force for Cardiac Pacing and Cardiac Resynchronization Therapy of the European Society of Cardiology. Developed in Collaboration with the European Heart Rhythm Association
Europace,
October 1, 2007;
9(10):
959 - 998.
[Full Text]
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Authors/Task Force Members, P. E. Vardas, A. Auricchio, J.-J. Blanc, J.-C. Daubert, H. Drexler, H. Ector, M. Gasparini, C. Linde, F. B. Morgado, et al.
Guidelines for cardiac pacing and cardiac resynchronization therapy: The Task Force for Cardiac Pacing and Cardiac Resynchronization Therapy of the European Society of Cardiology. Developed in Collaboration with the European Heart Rhythm Association
Eur. Heart J.,
September 2, 2007;
28(18):
2256 - 2295.
[Full Text]
[PDF]
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C.-M. Yu, Q. Zhang, and J. W.-H. Fung
Reply
J. Am. Coll. Cardiol.,
May 8, 2007;
49(18):
1900 - 1900.
[Full Text]
[PDF]
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O.-A. Breithardt
Cardiac Resynchronization Therapy
J. Am. Coll. Cardiol.,
May 8, 2007;
49(18):
1899 - 1899.
[Full Text]
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G. B. Bleeker, M. J. Schalij, and J. J. Bax
Reply
J. Am. Coll. Cardiol.,
May 8, 2007;
49(18):
1899 - 1900.
[Full Text]
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Does Echo Have a Role in Predicting Benefit from CRT?
Journal Watch Cardiology,
January 10, 2007;
2007(110):
3 - 3.
[Full Text]
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