Photoplethysmographic Features and Echocardiographic Cardiac Structural and Diastolic Modifications: Interaction with Kidney Function

Background: Photoplethysmography (PPG) offers a simple peripheral optical signal that may contain cardiac structure- and function-related information. However, multidomain PPG feature–echocardiographic remodeling phenotype associations and whether these associations vary with kidney function remain incompletely characterized. Methods: We performed a secondary observational analysis of 1283 cardiology participants. Four PPG indices representing temporal, harmonic, and pulse-rate variability domains, including systolic duration (Ts), systolic-to-diastolic duration ratio (Ts/Td), second-harmonic-to-fundamental ratio (H2/H1), and low-frequency-to-high-frequency ratio (LF/HF), were evaluated against the early mitral inflow velocity-to-early diastolic mitral annular velocity ratio (E/e′), left atrial volume index (LAVI), and left ventricular mass index (LVMI). All 1283 participants were included in the primary analyses of each echocardiographic outcome. Multivariable regression was adjusted for age, sex, body mass index, systolic blood pressure, pulse rate, hypertension, diabetes mellitus, coronary artery disease, beta-blocker use, and estimated glomerular filtration rate (eGFR). False-discovery-rate (FDR) correction was applied; kidney-function interactions were investigated using eGFR < 60 versus ≥60 mL/min/1.73 m2. Results: Higher log2(LF/HF) was independently associated with lower E/e′ (−5.02% per 1-standard-deviation increase; 95% confidence interval [CI], −7.51% to −2.46%; q = 0.002), lower LAVI (−5.19%; 95% CI, −7.91% to −2.39%; q = 0.002), and lower LVMI (−2.57%; 95% CI, −4.60% to −0.50%; q = 0.046). Higher Ts/Td was associated with higher LVMI (+4.05%; q = 0.028), whereas higher H2/H1 was associated with lower LVMI (−3.48%; q = 0.049). Kidney function significantly altered several PPG–remodeling associations, most prominently for LAVI; LF/HF–LAVI associations in participants with eGFR ≥ 60 and <60 mL/min/1.73 m2 were −2.91% and −11.92%, respectively (interaction q = 0.007). Sensitivity analyses generally supported the principal findings; however, incorporating the four PPG indices into clinical models yielded minimal incremental predictive improvement. Conclusions: PPG-derived pulse variability and waveform features were associated with diastolic function and cardiac remodeling echocardiographic measures, with considerable kidney-function-dependent heterogeneity. These findings support PPG as a physiological phenotyping tool for cardiorenal and remodeling-related signals but not as a stand-alone replacement for echocardiography.