Abstract Body (Do not enter title and authors here): Background:
Although microcirculatory function is known to be affected by chronic heart failure (HF), the lack of available sensing technology has limited its investigation. A noninvasive wearable tissue oximeter using near-infrared spectroscopy (NIRS) was developed to measure microcirculatory adaptation during cardiovascular stressors such as vascular occlusion testing (VOT) and mild activity such as a six-minute walk test (6MWT) as a step toward remote monitoring of HF patients during daily activities.
Hypothesis:
We aimed to assess microvascular responses using tissue oximetry on relevant body sites to further characterize HF patients based on their disease stage.
Methods:
Patients (n=20, F=3, NYHA Class I-III) completed a single visit to the clinic (approximately 30 min each). NIRSense devices were placed on the patient’s dominant arm, thigh, and sternum using a custom adhesive patch. Tissue oxygenation (StO2) and reperfusion slopes were independently calculated from sensor signals (Figure 1, B, D).
Results:
Mean VOT reperfusion slopes were 0.083526 +/- 0.114388 (NYHA I), 0.079975 +/- 0.43068 (NYHA II), and 0.064203 +/- 0.159261 (NYHA III). During 6MWT, Mean StO2 was 86.6% +/- 0.1% at baseline (sternum) and 83.1% +/- 0.2% at baseline (thigh). Percent change over the initial 100s of the 6MWT was 5.3 +/- 0.674% (NYHA I), 3.35 +/- 0.745% (NYHA II), 2.67 +/- 1.8% (NYHA III) for sternum and 2.45 +/- 4.28%, 2.94 +/- 2.12%, 2.5 +/- 1.19% for thigh. Reperfusion slopes were lower in the more severe NYHA class (Figure 1, C). StO2 during the 6MWT showed larger decrease after the first 100s in the more severe NYHA class (Figure 1, E). Three patients were excluded from VOT (only) analyses due to poor signal quality.
Conclusion:
We were able to measure tissue oxygenation kinetics during cardiovascular stressors in chronic HF population. NIRS-based tissue oximetry, particularly during VOT, can characterize microvascular function and differentiate patients based on HF stage. Data collection is still ongoing to enable statistical analyses. Continuous tissue oximetry has potential as a prognosis tool, and remote monitoring during daily activities may allow early detection and intervention in HF and pre-HF populations.