Current concepts relating coronary flow, myocardial perfusion and metabolism in left bundle branch block and cardiac
Simon Claridge1, Zhong Chen2, Tom Jackson2
1Guy's and St Thomas' Hospital, UK; King's College London, UK.
Insights
Cardiac resynchronisation therapy (CRT) benefits heart failure patients, but 50% don't respond. Research explores dyssynchrony's effects on coronary flow, perfusion, and metabolism to predict non-response and improve CRT outcomes.
Area of Science:
- Cardiology
- Biomedical Engineering
- Physiology
Background:
- Cardiac resynchronisation therapy (CRT) improves outcomes in heart failure patients with ventricular dyssynchrony.
- A significant 50% of patients do not respond to CRT, and reliable biomarkers for non-response are lacking.
- Understanding the pathophysiological effects of dyssynchrony on coronary flow, myocardial perfusion, and metabolism is crucial.
Purpose of the Study:
- To investigate the impact of electrical and mechanical dyssynchrony on coronary vasculature and myocardial perfusion.
- To explore how CRT affects coronary flow and myocardial perfusion patterns.
- To assess the potential of metabolic phenotyping for identifying CRT non-responders.
Main Methods:
- Review of studies examining coronary flow dynamics from epicardial arteries to the microvasculature in dyssynchronous hearts.
- Analysis of research on the effects of dyssynchrony on septal and lateral myocardial perfusion.
- Evaluation of novel invasive and non-invasive metabolic phenotyping approaches for non-responder identification.
Main Results:
- Dyssynchronous electrical activation impacts coronary flow across the vasculature, with potential correction by CRT.
- The effect of dyssynchrony on myocardial perfusion is debated, with some studies noting reduced septal perfusion and others increased lateral perfusion.
- CRT may enhance myocardial perfusion homogeneity in patients with initial perfusion heterogeneity.
Conclusions:
- Further research is needed to elucidate the complex interactions between coronary flow, perfusion, and metabolism in CRT patients.
- Improved understanding of these interactions could lead to better prediction of CRT non-response.
- Metabolic phenotyping shows promise for identifying patients who will not benefit from CRT.
Abstract:
Cardiac resynchronisation therapy (CRT) improves mortality and symptoms in heart failure patients with electromechanically dyssynchronous ventricles. There is a 50% non-response rate and reproducible biomarkers to predict non-response have not been forthcoming. Therefore, there has been increasing interest in the pathophysiological effects of dyssynchrony particularly focusing on coronary flow, myocardial perfusion and metabolism. Studies suggest that dyssynchronous electrical activation effects coronary flow throughout the coronary vasculature from the epicardial arteries to the microvascular bed and that these changes can be corrected by CRT. The effect of both electrical and mechanical dyssynchrony on myocardial perfusion is unclear with some studies suggesting there is a reduction in septal perfusion whilst others propose that there is an increase in lateral perfusion. Better understanding of these effects offers the possibility for better prediction of non-response. CRT appears to improve homogeneity in myocardial perfusion where heterogeneity is described in the initial substrate. Novel approaches to the identification of non-responders via metabolic phenotyping both invasively and non-invasively have been encouraging. There remains a need for further research to clarify the interaction of coronary flow with perfusion and metabolism in patients who undergo CRT.
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