Systolic time intervals derived from electrocardiographic gated intra-renal artery Doppler waveform associated with left ventricular systolic function

The association between the renal resistive index and the myocardial performance index in the general population

OBJECTIVE

The renal resistive index (RRI) is the most described measure of renal hemodynamics. The myocardial performance index (MPI) is widely used to assess overall myocardial performance. In this study, we aimed to investigate the relationship between renal hemodynamics, assessed by the RRI, and cardiac functions, assessed by the MPI in the general population.

METHODS

This single-center, cross-sectional study included a total of 302 consecutive patients who presented to our outpatient cardiology clinic between October 2019 and February 2020. All patients underwent transthoracic echocardiography and renal Doppler ultrasonography. The study population was divided into two groups: low RRI group (RRI ≤ 0.7, n = 236) and high RRI group (RRI > 0.7, n = 66).

RESULTS

E/A ratio, left ventricular ejection fraction (LVEF), and the MPI were significantly higher in the high RRI group than in the low RRI group (61.3 ± 15.4 vs 55.3 ± 16.4, P = .010 for E velocity; 0.9 ± 0.3 vs 0.7 ± 0.2, P = .008 for E/A ratio; 57.7 ± 4.7 vs 53.2 ± 10.1, P = .029 for LVEF; 0.52 ± 0.1 vs 0.43 ± 0.1, P < .001 for the MPI). A stepwise linear regression analysis demonstrated that LVEF (β = .123, P = .026), E velocity (β = .221, P < .001), and the MPI (β = .392, P < .001) were independently associated with the RRI.

CONCLUSION

Left ventricular ejection fraction and intra-cardiac Doppler blood flow indices, including E velocity and the MPI, were significantly and independently associated with the RRI in the general population.

Association of renal systolic time intervals with brachial-ankle pulse wave velocity

Aims: The renal systolic time intervals (STIs), including renal pre-ejection period (PEP), renal ejection time (ET), and renal PEP/renal ET measured by renal Doppler ultrasound, were associated with poor cardiac function and adverse cardiac outcomes. However, the relationship between renal hemodynamic parameters and arterial stiffness in terms of brachial-ankle pulse wave velocity (baPWV) has never been evaluated. The aim of this study was to assess the relationship between renal STIs and baPWV. Methods: This cross-sectional study enrolled 230 patients. The renal hemodynamics was measured from Doppler ultrasonography and baPWV was measured from ABI-form device by an oscillometric method. Results: Patients with baPWV ≧ 1672 cm/s had a higher value of renal resistive index (RI) and lower values of renal PEP and renal PEP/ET (all P< 0.001). In univariable analysis, baPWV was significantly associated with renal RI, renal PEP, and renal PEP/renal ET (all P< 0.001). In multivariable analysis, renal PEP (unstandardized coefficient β = -3.185; 95% confidence interval = -5.169 to -1.201; P = 0.002) and renal PEP/renal ET (unstandardized coefficient β = -5.605; 95% CI = -10.217 to -0.992; P = 0.018), but not renal RI, were still the independent determinants of baPWV. Conclusion: Our results found that renal PEP and renal PEP/renal ET were independently associated with baPWV. Hence, renal STIs measured from renal echo may have a significant correlation with arterial stiffness.

Renal systolic time intervals derived from intra-renal artery Doppler as a novel predictor of adverse cardiac outcomes

The aim of this study was to evaluate the use of renal systolic time intervals measured by electrocardiographic gated Doppler ultrasonography for predicting adverse cardiac events. This longitudinal observation study enrolled 205 patients. Renal systolic time intervals, including pre-ejection period (PEP) and ejection time (ET), and ratio of renal PEP to ET, were measured by electrocardiographic gated Doppler ultrasound. The 14 adverse cardiac events identified in this population included 9 cardiac deaths and 5 hospitalizations for heart failure during an average follow up of 30.9 months (25^th-75^th percentile: 30-33 months). Renal PEP (hazard ratio = 1.023, P = 0.001), renal ET (hazard ratio = 0.975, P = 0.001) and renal PEP/ET (per 0.01 unit increase, hazard ratio = 1.060, P < 0.001) were associated with poor cardiac outcomes. The addition of renal PEP/ET to a Cox model containing important clinical variables and renal resistive index further improved the value in predicting adverse cardiac events (Chi-square increase, 9.996; P = 0.002). This study showed that parameters of intra-renal hemodynamics were potential predictors of adverse cardiac outcomes. However, the generalizability of these indicators need to be investigated in future large-scale studies.

Ultrafast wavelength multiplexed broad bandwidth digital diffuse optical spectroscopy for in vivo extraction of tissue optical properties

Frequency-domain diffuse optical spectroscopy (FD-DOS) utilizes intensity-modulated light to characterize optical scattering and absorption in thick tissue. Previous FD-DOS systems have been limited by large device footprints, complex electronics, high costs, and limited acquisition speeds, all of which complicate access to patients in the clinical setting. We have developed a new digital DOS (dDOS) system, which is relatively compact and inexpensive, allowing for simplified clinical use, while providing unprecedented measurement speeds. The dDOS system utilizes hardware-integrated custom board-level direct digital synthesizers and an analog-to-digital converter to generate frequency sweeps and directly measure signals utilizing undersampling at six wavelengths modulated at discrete frequencies from 50 to 400 MHz. Wavelength multiplexing is utilized to achieve broadband frequency sweep measurements acquired at over 97 Hz. When compared to a gold-standard DOS system, the accuracy of optical properties recovered with the dDOS system was within 5.3% and 5.5% for absorption and reduced scattering coefficient extractions, respectively. When tested in vivo, the dDOS system was able to detect physiological changes throughout the cardiac cycle. The new FD-dDOS system is fast, inexpensive, and compact without compromising measurement quality.