Bertolone, Dario Tino Absolute Coronary Flow and Microvascular Resistance to assess Coronary Microcirculation in different Clinical Settings. [Tesi di dottorato]

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Abstract

This thesis explores the significance of coronary microvascular dysfunction (CMD) as a contributor to chest pain and adverse clinical outcomes, emphasizing its importance beyond patients with angina and non-obstructive coronary artery disease (ANOCA). By utilizing continuous thermodilution, we demonstrate a reliable method for assessing CMD that delivers deeper insights into coronary blood flow dynamics compared to traditional approaches like the Index of Microcirculatory Resistance (IMR) and Coronary Flow Reserve (CFR). Our findings reveal that continuous thermodilution provides more reproducible and precise measurements of absolute coronary blood flow (Q) and microvascular resistance (Rμ), leading to substantial reclassification of patient diagnoses and highlighting potential overestimations associated with bolus thermodilution. The thesis further investigates the impact of epicardial resistance on microvascular parameters, illustrating the differential influence on CFR and MRR, with MRR emerging as a more stable marker in the context of increased epicardial resistance. Our study demonstrates the prevalence and characteristics of CMD in various conditions, including heart failure (HFpEF and HFrEF), severe aortic stenosis (AS), Takotsubo syndrome (TTS), and diabetes mellitus (T2DM), revealing unique pathophysiological mechanisms across these patient groups. Notably, we identify distinct profiles of CMD in HF patients, suggesting tailored management strategies based on the underlying mechanisms. In patients with severe AS, TAVI resulted in improved hyperemic perfusion, yet persistent microvascular impairment remained evident. In TTS, acute CMD was linked to myocardial dysfunction, with recovery observed in microvascular function following appropriate intervention. Finally, we found that CMD is prevalent in T2DM patients, indicating early alterations in microvascular function, critical for risk stratification and therapeutic applications. Collectively, our findings underscore the necessity of integrating microvascular assessments into clinical practice to enhance CMD diagnosis and optimize patient management across diverse cardiovascular conditions.

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