Cardiac Health Assessment Using a Wearable Device Before and After Transcatheter Aortic Valve Implantation: Prospective Study.

Background: Due to aging of the population, the prevalence of aortic valve stenosis will increase drastically in upcoming years. Consequently, transcatheter aortic valve implantation (TAVI) procedures will also expand worldwide. Optimal selection of patients who benefit with improved symptoms and prognoses is key, since TAVI is not without its risks. Currently, we are not able to adequately predict functional outcomes after TAVI. Quality of life measurement tools and traditional functional assessment tests do not always agree and can depend on factors unrelated to heart disease. Activity tracking using wearable devices might provide a more comprehensive assessment. Objective: This study aimed to identify objective parameters (eg, change in heart rate) associated with improvement after TAVI for severe aortic stenosis from a wearable device. Methods: In total, 100 patients undergoing routine TAVI wore a Philips Health Watch device for 1 week before and after the procedure. Watch data were analyzed offline-before TAVI for 97 patients and after TAVI for 75 patients. Results: Parameters such as the total number of steps and activity time did not change, in contrast to improvements in the 6-minute walking test (6MWT) and physical limitation domain of the transformed WHOQOL-BREF questionnaire. Conclusions: These findings, in an older TAVI population, show that watch-based parameters, such as the number of steps, do not change after TAVI, unlike traditional 6MWT and QoL assessments. Basic wearable device parameters might be less appropriate for measuring treatment effects from TAVI.

The Influence of Epicardial Resistance on Microvascular Resistance Reserve.

BACKGROUND: The optimal index of microvascular function should be specific for the microvascular compartment. Yet, coronary flow reserve (CFR), despite being widely used to diagnose coronary microvascular dysfunction (CMD), is influenced by both epicardial and microvascular resistance. Conversely, microvascular resistance reserve (MRR) adjusts for fractional flow reserve (FFR), and thus is theoretically independent of epicardial resistance. OBJECTIVES: The authors tested the hypothesis that MRR, unlike CFR, is not influenced by increasing epicardial resistance, and thus is a more specific index of microvascular function. METHODS: In a cohort of 16 patients who had undergone proximal left anterior descending artery stenting, we created 4 grades of artificial stenosis (no stenosis, mild, moderate, and severe) using a coronary angioplasty balloon inflated to different degrees within the stent. For each stenosis grade, we calculated CFR and MRR using continuous thermodilution (64 measurements of each) to assess their response to changing epicardial resistance. RESULTS: Graded balloon inflation resulted in a significant sequential decrease in mean FFR (no stenosis: 0.82 ± 0.05; mild: 0.72 ± 0.04; moderate: 0.61 ± 0.05; severe: 0.48 ± 0.09; P < 0.001). This translated into a linear decrease in mean hyperemic coronary flow (no stenosis: 170.5 ± 66.8 mL/min; mild: 149.8 ± 58.8 mL/min; moderate: 124.4 ± 53.0 mL/min; severe: 94.0 ± 45.2 mL/min; P < 0.001). CFR exhibited a marked linear decrease with increasing stenosis (no stenosis: 2.5 ± 0.9; mild: 2.2 ± 0.8; moderate: 1.8 ± 0.7; severe: 1.4 ± 0.6), corresponding to a decrease of 0.3 for a decrease in FFR of 0.1 (P < 0.001). In contrast, MRR exhibited a negligible decrease across all stenosis grades (no stenosis: 3.0 ± 1.0; mild: 3.0 ± 1.0; moderate: 2.9 ± 1.0; severe: 2.8 ± 1.0), corresponding to a decrease of just 0.05 for a decrease in FFR of 0.1 (P < 0.001). CONCLUSIONS: MRR, unlike CFR, is minimally influenced by epicardial resistance, and thus should be considered the more specific index of microvascular function. This suggests that MRR can also reliably evaluate microvascular function in patients with significant epicardial disease.

Measuring Absolute Coronary Flow and Microvascular Resistance by Thermodilution: JACC Review Topic of the Week.

Diagnosing coronary microvascular dysfunction remains challenging, primarily due to the lack of direct measurements of absolute coronary blood flow (Q) and microvascular resistance (Rµ). However, there has been recent progress with the development and validation of continuous intracoronary thermodilution, which offers a simplified and validated approach for clinical use. This technique enables direct quantification of Q and Rµ, leading to precise and accurate evaluation of the coronary microcirculation. To ensure consistent and reliable results, it is crucial to follow a standardized protocol when performing continuous intracoronary thermodilution measurements. This document aims to summarize the principles of thermodilution-derived absolute coronary flow measurements and propose a standardized method for conducting these assessments. The proposed standardization serves as a guide to ensure the best practice of the method, enhancing the clinical assessment of the coronary microcirculation.