Imaging of myocardial dyssynchrony in congestive heart failure
Boaz D Rosen1, Albert C Lardo, Ronald D Berger
1Division of Cardiology, Johns Hopkins University, Baltimore, MD, USA. rosenbo_99@yahoo.com
Insights
Biventricular pacing can improve heart failure outcomes, but patient selection is key. Advanced imaging techniques like Tissue Doppler Imaging help identify candidates who will benefit most from this cardiac resynchronization therapy.
Area of Science:
- Cardiology
- Medical Imaging
- Biomedical Engineering
Background:
- Heart failure is a significant health issue, with limited effectiveness of current treatments like ACE inhibitors and beta-blockers.
- Myocardial conduction abnormalities, particularly left bundle branch block (LBBB), are common in heart failure patients and linked to impaired mechanical function.
- Biventricular (BiV) pacing shows promise in improving outcomes for selected heart failure patients with conduction abnormalities.
Purpose of the Study:
- To review the role of imaging modalities in patient selection for biventricular pacing (cardiac resynchronization therapy - CRT).
- To highlight the benefits and limitations of various imaging techniques, including echo-Doppler, Tissue Doppler Imaging, and MRI.
- To discuss the evolving field of dyssynchrony imaging and its potential impact on CRT.
Main Methods:
- Review of existing studies on biventricular pacing and cardiac resynchronization therapy (CRT).
- Evaluation of imaging techniques such as echo-Doppler, Tissue Doppler Imaging (TDI), and Magnetic Resonance Imaging (MRI) for patient selection.
- Discussion of novel imaging techniques like speckle tracking.
Main Results:
- Biventricular pacing can improve exercise tolerance, reduce heart failure morbidity and mortality, enhance ejection fraction, decrease mitral regurgitation, and promote reverse remodeling.
- A significant portion of patients do not benefit from BiV pacing, suggesting electrical activity doesn't always correlate with mechanical function.
- Tissue Doppler Imaging (TDI) is a valuable, accessible tool for evaluating CRT candidates and response, despite limitations in acoustic windows.
- MRI offers 3-D myocardial function imaging but is limited for follow-up due to cost and potential device interference.
Conclusions:
- Accurate patient selection is crucial for successful biventricular pacing (CRT).
- Advanced imaging, particularly TDI and emerging techniques like speckle tracking, are vital for optimizing CRT outcomes.
- Continued research in dyssynchrony imaging is needed to further refine patient selection and improve CRT efficacy.
Abstract:
Heart failure constitutes a major health problem in USA and Europe. Angiotensin converting enzyme inhibitors and _ blockers were shown to reduce morbidity and mortality in patients with CHF. Yet, their effectiveness is limited. A significant number of patients with heart failure manifest myocardial conduction abnormalities. Conduction abnormalities, especially in the form of left bundle branch block (LBBB) may be associated with abnormal mechanical function. Several studies demonstrated that these patients may gain benefit from biventricular (BiV) pacing in terms of improvement in exercise tolerance, heart failure morbidity and even decreased mortality. BiV pacing was also associated with improvement in ejection fraction, reduction in the extent of mitral regurgitation and a decrease in cardiac size (reverse remodeling). However, a significant number of patients do not gain benefit from biventricular pacing despite having conduction abnormalities. The underlying reason is that the electrical activity may not closely reflect mechanical activity. Several imaging modalities and techniques have been proposed to improve the selection of patients who may benefit from biventricular pacemakers. Of those, echo-Doppler, and especially, Tissue Doppler Imaging has been demonstrated as important tools for evaluating patients for cardiac resynchronization therapy (CRT) and following their response. The advantages of echo include accessibility, portability, its cost and a high temporal resolution. Yet, it is limited by its acoustic windows and scanning angles. MRI is a useful tool for evaluating patients for CRT by providing 3-D image of myocardial function. However, it is limited for follow-up after implantation due to its cost and a potential damage to the patients or pacemakers. Dyssnchrony imaging is a rapidly evolving field. New imaging techniques such as speckle tracking are promising and close update is needed to keep track of the developments and the changes in this exciting field.
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