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Marwick TH, Shah SJ, Thomas JD. Myocardial Strain in the Assessment of Patients With Heart Failure: A Review. JAMA Cardiol 2020; 4:287-294. [PMID: 30810702 DOI: 10.1001/jamacardio.2019.0052] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Importance The cornerstones of imaging in heart failure (HF) are the measurement of systolic and diastolic function and left ventricular (LV) filling pressure. Observations Ejection fraction and the assessment of LV filling pressure and diastolic dysfunction using the ratio of early transmitral flow and LV relaxation (E/e') are conventional imaging markers of LV function. Despite their extensive use in HF guidelines, both have significant detractions, especially in an era when HF with preserved ejection fraction is becoming the dominant presentation. In contrast, strain imaging has provided a new window into myocardial mechanics. Myocardial strain is now well validated, robust, and can easily be performed on most modern echocardiography machines. This Review summarizes the evidence in 9 situations across the stages of HF where LV global longitudinal strain and other strain parameters may provide information on risk prediction, diagnosis, assessment of treatment response, and follow-up. Conclusions and Relevance The evolution of myocardial deformation imaging from research tool to clinical practice will provide clinicians with a useful additional imaging parameter to facilitate the assessment and risk evaluation of patients with HF.
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Affiliation(s)
- Thomas H Marwick
- Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Sanjiv J Shah
- Bluhm Cardiovascular Institute, Northwestern University, Chicago, Illinois.,Associate Editor
| | - James D Thomas
- Bluhm Cardiovascular Institute, Northwestern University, Chicago, Illinois
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2
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Liang Y, Wang Q, Zhang M, Wang J, Chen H, Yu Z, Gong X, Su Y, Ge J. Cessation of pacing in super‐responders of cardiac resynchronization therapy: A randomized controlled trial. J Cardiovasc Electrophysiol 2018; 29:1548-1555. [PMID: 30106214 DOI: 10.1111/jce.13711] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 08/03/2018] [Accepted: 08/06/2018] [Indexed: 01/04/2023]
Affiliation(s)
- Yixiu Liang
- Department of CardiologyShanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan UniversityShanghai China
| | - Qingqing Wang
- Department of CardiologyShanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan UniversityShanghai China
| | - Mingliang Zhang
- Department of CardiologyCentral Hospital of Tai’an Shandong China
| | - Jingfeng Wang
- Department of CardiologyShanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan UniversityShanghai China
| | - Haiyan Chen
- Department of EchocardiographyShanghai Institute of Medical Imaging, Zhongshan Hospital, Fudan UniversityShanghai China
| | - Ziqing Yu
- Department of CardiologyShanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan UniversityShanghai China
| | - Xue Gong
- Department of CardiologyDeltahealth HospitalShanghai China
| | - Yangang Su
- Department of CardiologyShanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan UniversityShanghai China
| | - Junbo Ge
- Department of CardiologyShanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan UniversityShanghai China
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Mele D, Bertini M, Malagù M, Nardozza M, Ferrari R. Current role of echocardiography in cardiac resynchronization therapy. Heart Fail Rev 2018; 22:699-722. [PMID: 28714039 DOI: 10.1007/s10741-017-9636-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cardiac resynchronization therapy (CRT) is an established treatment for patients with heart failure and left ventricular systolic dysfunction. Patients are usually assessed by echocardiography, which provides a number of anatomical and functional information used for cardiac dyssynchrony assessment, prognostic stratification, identification of the optimal site of pacing in the left ventricle, optimization of the CRT device, and patient follow-up. Compared to other cardiac imaging techniques, echocardiography has the advantage to be non-invasive, repeatable, and safe, without exposure to ionizing radiation or nefrotoxic contrast. In this article, we review current evidence about the role of echocardiography before, during, and after the implantation of a CRT device.
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Affiliation(s)
- Donato Mele
- Centro Cardiologico Universitario and LTTA Centre, University of Ferrara, Ferrara, Italy. .,Noninvasive Cardiology Unit, Azienda Ospedaliero-Universitaria, Via Aldo Moro 8, 44124, Ferrara, Cona, Italy.
| | - Matteo Bertini
- Centro Cardiologico Universitario and LTTA Centre, University of Ferrara, Ferrara, Italy
| | - Michele Malagù
- Centro Cardiologico Universitario and LTTA Centre, University of Ferrara, Ferrara, Italy
| | - Marianna Nardozza
- Centro Cardiologico Universitario and LTTA Centre, University of Ferrara, Ferrara, Italy
| | - Roberto Ferrari
- Centro Cardiologico Universitario and LTTA Centre, University of Ferrara, Ferrara, Italy.,Maria Cecilia Hospital, GVM Care & Research, E.S. Health Science Foundation, Cotignola, RA, Italy
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Mele D, Luisi GA, Malagù M, Laterza A, Ferrari R, Bertini M. Echocardiographic evaluation of cardiac dyssynchrony: Does it still matter? Echocardiography 2018; 35:707-715. [PMID: 29719067 DOI: 10.1111/echo.13902] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cardiac resynchronization therapy (CRT) is an established treatment for patients with heart failure and left ventricular systolic dysfunction. For many years, cardiac mechanical dyssynchrony assessed by echocardiography has been considered as a key evaluation to characterize CRT candidates and predict CRT response. In current guidelines, however, CRT implant indications rely only on electrical dyssynchrony. The aim of this article was to clarify whether and how the evaluation of cardiac mechanical dyssynchrony should be performed today by echocardiography.
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Affiliation(s)
- Donato Mele
- Cardiology Unit and LTTA Center, University of Ferrara, Ferrara, Italy
| | | | - Michele Malagù
- Cardiology Unit and LTTA Center, University of Ferrara, Ferrara, Italy
| | - Anna Laterza
- Cardiology Unit and LTTA Center, University of Ferrara, Ferrara, Italy
| | - Roberto Ferrari
- Cardiology Unit and LTTA Center, University of Ferrara, Ferrara, Italy.,Maria Cecilia Hospital, GVM Care & Research, E.S. Health Science Foundation, Cotignola, Italy
| | - Matteo Bertini
- Cardiology Unit and LTTA Center, University of Ferrara, Ferrara, Italy
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Höke U, Bax JJ, Delgado V, Ajmone Marsan N. Assessment of left ventricular dyssynchrony by three-dimensional echocardiography: Prognostic value in patients undergoing cardiac resynchronization therapy. J Cardiovasc Electrophysiol 2018; 29:780-787. [PMID: 29377419 DOI: 10.1111/jce.13445] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 01/10/2018] [Accepted: 01/22/2018] [Indexed: 11/26/2022]
Abstract
BACKGROUND Systolic dyssynchrony index (SDI) using three-dimensional echocardiography (3DE) was shown to be a reliable measure of left ventricular (LV) dyssynchrony. However, the prognostic value of SDI on long-term outcomes after cardiac resynchronization therapy (CRT) remains unknown. METHODS AND RESULTS A total of 414 patients (mean age 67 ± 10 years, 60% ischemic etiology) with 3DE evaluation before CRT implantation were included. SDI was evaluated as continuous value and in quartiles. The study endpoint was combined all-cause mortality, heart transplantation, and LV assist device implantation. At baseline, median SDI was 8.0% (IQR 5.6-11.3%). During a median follow-up of 45 months (IQR 25-59 months), the endpoint was observed in 94 (23%) patients. SDI was independently associated with the endpoint together with ischemic etiology, diabetes, and renal function (HR 0.914, P = 0.003) after adjustment for age, atrial fibrillation, hemoglobin level, NYHA functional class, and posterolateral LV lead position. Patients from the 1st, 2nd, and 3rd SDI quartiles showed similar survival and superior as compared to the 4th quartile with the lowest SDI values (≤5.5%; χ²: 30.4, log-rank P < 0.001). From receiver operating characteristic curve analysis, the optimal SDI cut-off value associated with the endpoint was >6.8% (area under the curve 0.634). Finally, a subgroup analysis (293 patients) demonstrated that a more pronounced reduction in SDI immediately after CRT (resynchronization) was independently associated with superior survival (HR 0.461, P = 0.011) after adjustment for prognostic relevant parameters. CONCLUSION SDI is independently associated with long-term prognosis after CRT and might therefore be important to optimize risk-stratification in these patients.
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Affiliation(s)
- Ulas Höke
- Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands.,Interuniversity Cardiology Institute of The Netherlands, Utrecht, The Netherlands
| | - Jeroen J Bax
- Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Victoria Delgado
- Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Nina Ajmone Marsan
- Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands
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Abstract
Objective: Cardiac resynchronization therapy (CRT) has been shown to induce a structural and electrical remodeling; the data on whether left ventricle (LV) reverse remodeling is associated with restitution of intrinsic contraction pattern are unknown. In this study, we investigated the presence of improvement in left ventricular intrinsic dyssynchrony in patients with CRT. Methods: A total of 45 CRT recipients were prospectively studied. Dyssynchrony indexes including interventricular mechanical delay (IVMD) and tissue Doppler velocity opposing-wall delay (OWD) as well as QRS duration on 12-lead surface electrocardiogram were recorded before CRT device implantation. After 1 year, patients with chronic biventricular pacing were reprogramed to VVI 40 to allow the resumption of native conduction and contraction pattern. After 4–6 h of intrinsic rhythm, QRS duration and all echocardiographic measurements were recorded. Dyssynchrony was defined as IVMD >40 ms and OWD >65 ms. CRT response was defined by a ≥15% reduction in left ventricular end-systolic volume (LVESV) at a 12-month follow-up. Results: Thirty-two patients (71%) showed response to CRT. The native QRS duration reduced significantly from 150±12 ms to 138±14 ms (p<0.001), and dyssynchrony indexes showed a significant improvement only in responders. The mean OWD reduced from 86±37 ms to 50±29 ms (p<0.001), and the mean IVMD decreased from 55±22 ms to 28±22 ms (p<0.001) in responders. The reduction in LVESV was significantly correlated with ΔOWD (r=0.47, p=0.001), ΔIVMD (r=0.45, p=0.001), and ΔQRS (r=0.34, p=0.022). Conclusion: Chronic CRT significantly improves LV native contraction pattern and causes reverse remodeling in dyssynchrony.
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Witt CT, Kronborg MB, Nohr EA, Nielsen JC. Left ventricular performance during triggered left ventricular pacing in patients with cardiac resynchronization therapy and left bundle branch block. J Interv Card Electrophysiol 2016; 46:345-51. [PMID: 27272650 DOI: 10.1007/s10840-016-0155-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/27/2016] [Indexed: 10/21/2022]
Abstract
PURPOSE To assess the acute effect of triggered left ventricular pacing (tLVp) on left ventricular performance and contraction pattern in patients with heart failure, left bundle branch block (LBBB), and cardiac resynchronization therapy (CRT). METHODS Twenty-three patients with pre-implant QRS complex >150 ms, QRS complex narrowing under CRT, and sinus rhythm were included ≥3 months after CRT implantation. Echocardiographic assessment of left ventricular ejection fraction (LVEF), global peak systolic longitudinal strain (GLS), and contraction pattern by 2D strain was performed during intrinsic conduction, tLVp, and BiV pacing and compared as paired data. Echocardiographic analysis was done blinded with respect to pacing mode. RESULTS LVEF was significantly higher during BiV pacing (47 ± 11 %) compared with intrinsic conduction (43 ± 13 %, P = 0.001) and tLVp (44 ± 13 %, P = 0.001), while there was no difference between intrinsic conduction and tLVp (P = 0.28). GLS was higher during BiV (14 ± 3) than during intrinsic conduction (13 ± 3, P = 0.01) and tLVp (13 ± 3, P = 0.03). Difference in time-to-peak contraction between the basal septal and lateral walls was shorter during BiV pacing (-3 ± 44 ms) than during intrinsic conduction (129 ± 66, P < 0.001) and tLVp (118 ± 118 ms, P < 0.001), with no difference between tLVp and intrinsic conduction (P = 0.56). The electrocardiogram showed change in frontal axis from intrinsic conduction in only 2 (9 %) patients during tLVp and in 20 (87 %) patients during BiV pacing. CONCLUSIONS The acute effect of tLVp on LV systolic function and contraction pattern is significantly lower than the effect of BiV pacing and not different from intrinsic conduction in patients with LBBB and CRT.
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Affiliation(s)
- Christoffer Tobias Witt
- Department of Cardiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.
| | - Mads Brix Kronborg
- Department of Cardiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Ellen Aagaard Nohr
- Institute of Clinical Research, University of Southern Denmark, Winslowparken 19, 5000, Odense, Denmark
| | - Jens Cosedis Nielsen
- Department of Cardiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
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Long-Term Echocardiographic Response to Cardiac Resynchronization Therapy in Initial Nonresponders. JACC-HEART FAILURE 2015; 3:990-7. [PMID: 26577619 DOI: 10.1016/j.jchf.2015.09.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 09/04/2015] [Accepted: 09/05/2015] [Indexed: 11/22/2022]
Abstract
OBJECTIVES The aim of this study was to investigate the frequency and clinical implications of a delayed echocardiographic response to cardiac resynchronization therapy (CRT). BACKGROUND Long-term prognosis for CRT patients is routinely based on the assessment of echocardiograms after 6 to 12 months of therapy. Some patients, however, may require a longer period of therapy before echocardiographic improvements are detectable. METHODS This observational study included all patients with heart failure (HF) receiving a CRT device at a single center from 2003 to 2011. Eligible patients met current indications and had technically adequate echocardiograms from before implantation, approximately 1 year after implantation (mid-term), and ≥3 years after implantation (long-term). A positive echocardiographic response to CRT was defined as a reduction in left ventricular end-systolic volume ≥15%. All-cause mortality was compared for patients in 3 response groups: mid-term responders, long-term responders, and nonresponders. RESULTS During this study, 294 patients met the study criteria. Of the 120 patients who were nonresponders after 1 year, 52 (43%) experienced a delayed positive response. Delayed, long-term responders had mortality and hospitalization rates similar to mid-term responders and significantly lower than nonresponders. CONCLUSIONS Among patients surviving at least 3 years after implantation of a CRT device and with echocardiographic follow-up, a significant portion of nonresponders after 1 year of CRT experience a delayed echocardiographic response after a longer period of time. Survival and hospitalization rates were similar for all echocardiographic responders, regardless of the time at which the response occurred.
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Osca J, Alonso P, Cano O, Andrés A, Miro V, Tello MJS, Olagüe J, Martínez L, Salvador A. The use of multisite left ventricular pacing via quadripolar lead improves acute haemodynamics and mechanical dyssynchrony assessed by radial strain speckle tracking: initial results. Europace 2015; 18:560-7. [PMID: 26333378 DOI: 10.1093/europace/euv211] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 05/19/2015] [Indexed: 11/14/2022] Open
Abstract
AIMS The objective of the present study was to evaluate the effect of multipoint pacing (MPP) on acute haemodynamics, cardiac contractility, and left ventricle (LV) dyssynchrony, in comparison with conventional cardiac resynchronization therapy (CRT). METHODS AND RESULTS An open-label, non-randomized, single-centre, prospective study was designed. Twenty-seven consecutive patients were included. Evaluation of pacing configurations was performed in a random order. Transthoracic echocardiography was used to obtain haemodynamic and dyssynchrony parameters. Left ventricular ejection fraction (LVEF) was significantly superior in MPP compared with baseline (38.4 ± 1.8% vs. 26.1 ± 2.2%; P < 0.001), and in conventional pacing configuration compared with baseline (33.2 ± 1.8% vs. 26.1 ± 2.2%; P = 0.007). Cardiac index (CI) was increased by 21.8 ± 5.4% and 34.7 ± 5.1% in conventional and MPP configurations, respectively (P = 0.19). Percentage of acute responders (CI increase ≥10%) was 62.9 and 85.2% in conventional and MPP, respectively (P < 0.001). LV dyssynchrony was defined by radial strain rate parameters. Baseline anteroseptal-to-posterior wall time delay was 168 ± 21 ms. It was reduced until 70.4 ± 29 ms in conventional and -6.6 ± 11 ms in MPP (conventional vs. baseline P = 0.04; MPP vs. conventional P = 0.05). Standard deviation of the time-to-peak radial strain of the 6 LV basal segments was 101 ± 9.7, 80.3 ± 9.2, and 66 ± 8.03 ms in baseline, conventional, and MPP configurations, respectively (MPP vs. basal P = 0.012). Finally, we observed a positive correlation (r = 0.69) between reduction in dyssynchrony and CI increase (P < 0.0001). CONCLUSION MPP showed a further reduction in LV dyssynchrony compared with conventional biventricular pacing. Moreover, MPP resulted in an additional improvement in LVEF and in CI, and this was translated into a higher number of acute responders to CRT.
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Affiliation(s)
- Joaquín Osca
- Electrophysiology Section, Cardiology Department, Hospital Universitari i Politècnic La Fe, El Bachiller, 7-47, Valencia 46010, Spain
| | - Pau Alonso
- Electrophysiology Section, Cardiology Department, Hospital Universitari i Politècnic La Fe, El Bachiller, 7-47, Valencia 46010, Spain
| | - Oscar Cano
- Electrophysiology Section, Cardiology Department, Hospital Universitari i Politècnic La Fe, El Bachiller, 7-47, Valencia 46010, Spain
| | - Ana Andrés
- Electrophysiology Section, Cardiology Department, Hospital Universitari i Politècnic La Fe, El Bachiller, 7-47, Valencia 46010, Spain
| | - Vicente Miro
- Image Section, Cardiology Department, Hospital Universitari i Politècnic La Fe, Valencia, Spain
| | - María José Sancho Tello
- Electrophysiology Section, Cardiology Department, Hospital Universitari i Politècnic La Fe, El Bachiller, 7-47, Valencia 46010, Spain
| | - Jose Olagüe
- Electrophysiology Section, Cardiology Department, Hospital Universitari i Politècnic La Fe, El Bachiller, 7-47, Valencia 46010, Spain
| | - Luis Martínez
- Cardiology Department, Hospital Universitari i Politècnic La Fe, Valencia, Spain
| | - Antonio Salvador
- Cardiology Department, Hospital Universitari i Politècnic La Fe, Valencia, Spain
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Abstract
PURPOSE OF REVIEW Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with mild-to-severe heart failure. However, up to 40% of CRT recipients are nonresponders. This review addresses important aspects with regard to the identification and management of CRT nonresponders. RECENT FINDINGS Mid-term clinical or echocardiographic nonresponse is associated with worse clinical outcomes during the extended follow-up. A number of predictors are indicative of CRT response, which include patient characteristics, electrical determinants, and imaging techniques from preimplant to postimplant period, and can be grouped as modifiable and nonmodifiable contributors to treatment response. Advanced age, male sex, ischemic cause, end-stage heart failure, inadequate electrical delay, and absence of mechanical dyssynchrony are regarded as unfavorable but nonmodifiable factors, for which considering underutilization of CRT by refining patient selection is reasonable. On the contrary, more efforts should be made to optimize patient management by correcting those modifiable factors, such as suboptimal medical therapy, uncontrolled atrial fibrillation, left ventricular lead dislodgement or inappropriate location, loss of biventricular capture, and lack of device optimization. SUMMARY Proper management and careful selection of CRT recipients will transform a proportion of treatment nonresponders into responders, which is vital to improve patients' outcome.
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Bordachar P, Eschalier R, Lumens J, Ploux S. Optimal Strategies on Avoiding CRT Nonresponse. CURRENT TREATMENT OPTIONS IN CARDIOVASCULAR MEDICINE 2014; 16:299. [PMID: 24633974 DOI: 10.1007/s11936-014-0299-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OPINION STATEMENT The high rate of nonresponse to cardiac resynchronization therapy (CRT) has remained nearly unchanged since the treatment was introduced. We believe that this is directly related to the many persisting unknowns regarding the mechanical function of asynchronous hearts and the use of electrical stimulation to counteract the deleterious effects of that asynchrony. As a consequence, the key questions pertaining to the pre-implant, intra-implant, and postimplant phases remain unanswered or only partially answered. QRS duration is an imperfect selection criterion, as it does not discriminate the activation pattern. The inclusion of QRS morphology in the international professional practice guidelines is an important first step toward increasing the yield of this therapy. The invasive and the noninvasive electrical mapping techniques seem highly promising and need to be tested in large trials. The site of stimulation is a key element of the response to CRT; additional research must be pursued in this field.
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Exner DV, Auricchio A, Singh JP. Contemporary and future trends in cardiac resynchronization therapy to enhance response. Heart Rhythm 2012; 9:S27-35. [PMID: 22521939 DOI: 10.1016/j.hrthm.2012.04.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Indexed: 10/28/2022]
Abstract
The rationale for cardiac resynchronization therapy (CRT), expectations in terms of patient benefit, patient selection for CRT, selection of a CRT pacemaker (CRT-P) vs CRT plus implantable cardioverter-defibrillator (CRT-D) platform, and studies evaluating device programming to enhance benefit from CRT are reviewed. The notion of an "optimal" left ventricular (LV) pacing site, the rationale for identifying and avoiding LV pacing in regions of scar, the use of anatomic, hemodynamic, and electrical parameters to identify an optimal LV pacing site, and the potential utility of multisite LV pacing to enhance benefit from CRT are discussed. Finally, the advantages and disadvantages of the various methods for LV lead delivery are reviewed.
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Affiliation(s)
- Derek V Exner
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Canada
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