Subject-Specific Cardiovascular Signatures Revealed by Arterial Pulse Signals in Patients with Heart Diseases—Part II: Special Cases

Aim: This study evaluates whether cardiovascular (CV) parameters derived from noninvasive arterial pulse signals can reveal subject-specific characteristics in patients with atypical CV dynamics. Methods: Seven special-case patients—including a heart transplant (HTx) recipient and individuals with bradycardia (low heart rate, HR), low dicrotic notch (DN), and intermittent arterial pulse waveform (APW) variations—were analyzed across three visits over the cardiac rehabilitation (CR) period. Radial artery (RA) and carotid artery (CA) signals, acquired using micro-fabricated tactile sensors, were processed using a single-degree-of-freedom time–frequency (SDOF–TF) framework to extract multiple CV parameters. The analysis focused on descriptive characterization of subject-specific CV patterns in individual patients. Results: The patients exhibited highly heterogeneous CV profiles. Individuals with low HR exhibited relatively limited post-exercise HR changes. Individuals with low DN morphology exhibited elevated lower-order harmonic amplitudes. Individuals with intermittent APW variations exhibited cyclic changes in APW morphology at rest and during post-exercise recovery. Although CV patterns at rest differed across individuals, post-exercise assessment revealed more distinctive individual-specific differences, including differences between individuals within the same phenotype-based case subset. Across all patients and visits, RA measurements provided more stable and interpretable subject-specific CV patterns, whereas CA measurements were more susceptible to motion artifacts (MA) and sensor noise. For individuals with intermittent APW variations, the CA signals exhibited extremely poor signal quality, limiting their suitability for physiological interpretation. Conclusions: The SDOF–TF framework enabled the characterization of subject-specific, multi-parameter CV dynamics in these seven special cases. The findings illustrate the potential value of arterial pulse analysis for the individualized characterization of atypical CV dynamics. Future studies involving larger patient cohorts are needed to further investigate these findings and establish their clinical utility.