Reservoir-Excess Pressure Parameters Independently Predict Cardiovascular Events in Individuals With Type 2 Diabetes

Aortic reservoir-excess pressure parameters are associated with worse cognitive function in people with untreated stage II/III hypertension

OBJECTIVE

Hypertension is a recognized risk factor for the development of cognitive impairment and dementia in older adults. Aortic stiffness and altered haemodynamics could promote the transmission of detrimental high pressure pulsatility into the cerebral circulation, potentially damaging brain microvasculature and leading to cognitive impairment. We determined whether reservoir-excess pressure parameters were associated with cognitive function in people with hypertension (HT) and normotension (NT).

METHODS

We studied 35 middle-aged and older treatment-naïve stage II/III HT (office systolic BP 176 ± 17 mmHg) and 35 age-, sex- and body mass index-matched NT (office systolic BP 127 ± 8 mmHg). Parameters derived from reservoir-excess pressure analysis including reservoir pressure integral (INTPR), excess pressure integral (INTXSP), systolic rate constant (SRC), diastolic rate constant (DRC) and pulse wave velocity (PWV) were calculated from an ensemble-averaged aortic pressure waveform derived from radial artery tonometry. Cognitive function was assessed using the Addenbrooke's Cognitive Examination Revised (ACE-R), Trail Making Test Part A (TMT-A) and Part B (TMT-B).

RESULTS

All reservoir-excess pressure parameters were greater in HT than NT (all P  < 0.05). Greater INTXSP was associated with lower ACE-R score ( rs  = -0.31), longer TMT-A ( r  = 0.31) and TMT-B ( r  = 0.38). Likewise, greater DRC and PWV were also associated with lower ACE-R score ( rs  = -0.27 and rs  = -0.33), longer TMT-A ( r  = 0.51 and r  = 0.40) and TMT-B ( r  = 0.38 and r  = 0.32). Greater INTXSP, DRC and PWV are consistently associated with worse cognitive function in this study.

CONCLUSIONS

These observations support a potential mechanistic link between adverse haemodynamics and a heightened risk of cognitive impairment in older adults with hypertension.

Reservoir-excess pressure parameters are independently associated with NT-proBNP in older adults

AIMS

Parameters derived from reservoir-excess pressure analysis have been demonstrated to predict cardiovascular events. Thus, altered reservoir-excess pressure parameters could have a detrimental effect on highly-perfused organs like the heart. We aimed to cross-sectionally determine whether reservoir-excess pressure parameters were associated with N-terminal pro-brain-type natriuretic peptide (NT-proBNP) in older adults.

METHODS

We studied 868 older adults with diverse cardiovascular risk. Reservoir-excess pressure parameters were obtained through radial artery tonometry including reservoir pressure integral, peak reservoir pressure, excess pressure integral (INTXSP), systolic rate constant (SRC) and diastolic rate constant (DRC). Plasma levels of NT-proBNP, as a biomarker of cardiac overload, were analysed by the Proximity Extension Assay technology.

RESULTS

Multivariable linear regression analyses revealed that all reservoir-excess pressure parameters studied were associated with NT-proBNP after adjusting for age and sex. After further adjustments for conventional cardiovascular risk factors, INTXSP [β = 0.191 (95% confidence interval, CI: 0.099, 0.283), P < 0.001], SRC [β = -0.080 (95% CI: -0.141, -0.019), P = 0.010] and DRC [β = 0.138 (95% CI: 0.073, 0.202), P < 0.001] remained associated with NT-proBNP. Sensitivity analysis found that there were occasions where the association between SRC and NT-proBNP was attenuated, but both INTXSP and DRC remained consistently associated with NT-proBNP.

CONCLUSIONS

The observed associations between reservoir-excess pressure parameters and NT-proBNP suggest that altered reservoir-excess pressure parameters may reflect an increased load inflicted on the left ventricular cardiomyocytes and could have a potential to be utilized in the clinical setting for cardiovascular risk stratification.

Estimation of central blood pressure waveform from femoral blood pressure waveform by blind sources separation

Background

Central blood pressure (cBP) is a better indicator of cardiovascular morbidity and mortality than peripheral BP (pBP). However, direct cBP measurement requires invasive techniques and indirect cBP measurement is based on rigid and empirical transfer functions applied to pBP. Thus, development of a personalized and well-validated method for non-invasive derivation of cBP from pBP is necessary to facilitate the clinical routine. The purpose of the present study was to develop a novel blind source separation tool to separate a single recording of pBP into their pressure waveforms composing its dynamics, to identify the compounds that lead to pressure waveform distortion at the periphery, and to estimate the cBP. The approach is patient-specific and extracts the underlying blind pressure waveforms in pBP without additional brachial cuff calibration or any a priori assumption on the arterial model.

Methods

The intra-arterial femoral BPfe and intra-aortic pressure BPao were anonymized digital recordings from previous routine cardiac catheterizations of eight patients at the German Heart Centre Berlin. The underlying pressure waveforms in BPfe were extracted by the single-channel independent component analysis (SCICA). The accuracy of the SCICA model to estimate the whole cBP waveform was evaluated by the mean absolute error (MAE), the root mean square error (RMSE), the relative RMSE (RRMSE), and the intraclass correlation coefficient (ICC). The agreement between the intra-aortic and estimated parameters including systolic (SBP), diastolic (DBP), mean arterial pressure (MAP), and pulse pressure (PP) was evaluated by the regression and Bland-Altman analyses.

Results

The SCICA tool estimated the cBP waveform non-invasively from the intra-arterial BPfe with an MAE of 0.159 ± 1.629, an RMSE of 5.153 ± 0.957 mmHg, an RRMSE of 5.424 ± 1.304%, and an ICC of 0.94, as well as two waveforms contributing to morphological distortion at the femoral artery. The regression analysis showed a strong linear trend between the estimated and intra-aortic SBP, DBP, MAP, and PP with high coefficient of determination R2 of 0.98, 0.99, 0.99, and 0.97 respectively. The Bland-Altman plots demonstrated good agreement between estimated and intra-aortic parameters with a mean error and a standard deviation of difference of -0.54 ± 2.42 mmHg [95% confidence interval (CI): -5.28 to 4.20] for SBP, -1.97 ± 1.62 mmHg (95% CI: -5.14 to 1.20) for DBP, -1.49 ± 1.40 mmHg (95% CI: -4.25 to 1.26) for MAP, and 1.43 ± 2.79 mmHg (95% CI: -4.03 to 6.90) for PP.

Conclusions

The SCICA approach is a powerful tool that identifies sources contributing to morphological distortion at peripheral arteries and estimates cBP.

Reservoir Pressure Integral Is Independently Associated With the Reduction in Renal Function in Older Adults

BACKGROUND

Arterial hemodynamic parameters derived from reservoir-excess pressure analysis exhibit prognostic utility. Reservoir-excess pressure analysis may provide useful information about an influence of altered hemodynamics on target organ such as the kidneys. We determined whether the parameters derived from the reservoir-excess pressure analysis were associated with the reduction in estimated glomerular filtration rate in 542 older adults (69.4±7.9 years, 194 females) at baseline and after 3 years.

METHODS

Reservoir-excess pressure parameters, including reservoir pressure integral, excess pressure integral, systolic, and diastolic rate constants, were obtained by radial artery tonometry.

RESULTS

After 3 years, and in a group of 94 individuals (72.4±7.6 years, 26 females), there was an estimated glomerular filtration rate reduction of >5% per year (median reduction of 20.5% over 3 years). A multivariable logistic regression analysis revealed that higher baseline reservoir pressure integral was independently associated with a smaller reduction in estimated glomerular filtration rate after accounting for conventional cardiovascular risk factors and study centers (odds ratio: 0.660 [95% CIs, 0.494-0.883]; P=0.005). The association remained unchanged after further adjustments for potential confounders and baseline renal function (odds ratio: 0.528 [95% CIs, 0.351-0.794]; P=0.002). No other reservoir-excess pressure parameters exhibited associations with the reduction in renal function.

CONCLUSIONS

This study demonstrates that baseline reservoir pressure integral was associated with the decline in renal function in older adults at 3-year follow-up, independently of conventional cardiovascular risk factors. This suggests that reservoir pressure integral may play a role in the functional decline of the kidneys.

Carotid Reservoir Pressure Decrease After Prolonged Head Down Tilt Bed Rest in Young Healthy Subjects Is Associated With Reduction in Left Ventricular Ejection Time and Diastolic Length

Background

The arterial pressure waveform reflects the interaction between the heart and the arterial system and carries potentially relevant information about circulatory status. According to the commonly accepted 'wave transmission model', the net BP waveform results from the super-position of discrete forward and backward pressure waves, with the forward wave in systole determined mainly by the left ventricular (LV) ejection function and the backward by the wave reflection from the periphery, the timing and amplitude of which depend on arterial stiffness, the wave propagation speed and the extent of downstream admittance mismatching. However, this approach obscures the 'Windkessel function' of the elastic arteries. Recently, a 'reservoir-excess pressure' model has been proposed, which interprets the arterial BP waveform as a composite of a volume-related 'reservoir' pressure and a wave-related 'excess' pressure.

Methods

In this study we applied the reservoir-excess pressure approach to the analysis of carotid arterial pressure waveforms (applanation tonometry) in 10 young healthy volunteers before and after a 5-week head down tilt bed rest which induced a significant reduction in stroke volume (SV), end-diastolic LV volume and LV longitudinal function without significant changes in central blood pressure, cardiac output, total peripheral resistance and aortic stiffness. Forward and backward pressure components were also determined by wave separation analysis.

Results

Compared to the baseline state, bed rest induced a significant reduction in LV ejection time (LVET), diastolic time (DT), backward pressure amplitude (bP) and pressure reservoir integral (INTPR). INTPR correlated directly with LVET, DT, time to the peak of backward wave (bT) and stroke volume, while excess pressure integral (INTXSP) correlated directly with central pressure. Furthermore, Δ.INTPR correlated directly with Δ.LVET, and Δ.DT, and in multivariate analysis INTPR was independently related to LVET and DT and INTXSP to central systolic BP.

Conclusion

This is an hypothesis generating paper which adds support to the idea that the reservoir-wave hypothesis applied to non-invasively obtained carotid pressure waveforms is of potential clinical usefulness.