Update on the Use of Pulse Wave Velocity to Measure Age-Related Vascular Changes

PURPOSE OF REVIEW

Pulse wave velocity (PWV) is an important and well-established measure of arterial stiffness that is strongly associated with aging. Age-related alterations in the elastic properties and integrity of arterial walls can lead to cardiovascular disease. PWV measurements play an important role in the early detection of these changes, as well as other cardiovascular disease risk factors, such as hypertension. This review provides a comprehensive summary of the current knowledge of the effects of aging on arterial stiffness, as measured by PWV.

RECENT FINDINGS

This review highlights recent findings showing the applicability of PWV analysis for investigating heart failure, hypertension, and other cardiovascular diseases, as well as cerebrovascular diseases and Alzheimer's disease. It also discusses the clinical implications of utilizing PWV to monitor treatment outcomes, various challenges in implementing PWV assessment in clinical practice, and the development of new technologies, including machine learning and artificial intelligence, which may improve the usefulness of PWV measurements in the future. Measuring arterial stiffness through PWV remains an important technique to study aging, especially as the technology continues to evolve. There is a clear need to leverage PWV to identify interventions that mitigate age-related increases in PWV, potentially improving CVD outcomes and promoting healthy vascular aging.

Cardiac effects of renal ischemia

Mortality in acute kidney injury (AKI) remains very high, yet the cause of death is often failure of extrarenal organs. We and others have demonstrated remote organ dysfunction after renal ischemia. The term "cardiorenal syndrome" was first applied to the "cross talk" between the organs by the National Heart, Lung, and Blood Institute of the National Institutes of Health, and the clinical importance is being increasingly appreciated. Nevertheless, more information is needed to effectively address the consequences of renal injury on the heart. Since AKI often occurs in patients with comorbidities, we investigated the effect of renal ischemia in the setting of existing cardiac failure. We hypothesized that the cardiac effects of renal ischemia would be significantly amplified in experimental cardiomyopathy. Male Sprague-Dawley rats with preexisting cardiac and renal injury due to low-dose doxorubicin were subjected to bilateral renal artery occlusion. Cardiac structure and function were examined 2 days after reperfusion. Loss of functional myocardial tissue with decreases in left ventricular pressure, increases in apoptotic cell death, inflammation, and collagen, and greater disruption in ultrastructure with mitochondrial fragmentation were seen in the doxorubicin/ischemia group compared with animals in the groups treated with doxorubicin alone or following ischemia alone. Systemic inflammation and cardiac abnormalities persisted for at least 21 wk. These results suggest that preexisting comorbidities can result in much more severe distant organ effects of acute renal injury. The results of this study are relevant to human AKI.NEW & NOTEWORTHY Acute kidney injury is common, expensive, and deadly, yet morbidity and mortality are often secondary to remote organ dysfunction. We hypothesized that the effects of renal ischemia would be amplified in the setting of comorbidities. Sustained systemic inflammation and loss of functional myocardium with significantly decreased systolic and diastolic function, apoptotic cell death, and increased collagen and inflammatory cells were found in the heart after renal ischemia in the doxorubicin cardiomyopathy model (vs. renal ischemia alone). Understanding the remote effects of renal ischemia has the potential to improve outcomes in acute kidney injury.

Overcoming the Limits of Ejection Fraction and Ventricular-Arterial Coupling in Heart Failure

Left ventricular ejection fraction (LVEF) and ventricular-arterial coupling (VAC) [VAC = Ea/Ees; Ea: effective arterial elastance; Ees: left ventricle (LV) elastance] are both dimensionless ratios with important limitations, especially in heart failure setting. The LVEF to VAC relationship is a divergent non-linear function, having a point of intersection at the specific value of 0.62, where V0 = 0 ml (V0: the theoretical extrapolated value of the volume-axis intercept at end-systolic pressure 0 mmHg). For the dilated LV, both LVEF and VAC are highly dependent on V0 which is inconclusive when derived from single-beat Ees formulas. VAC simplification should be avoided. Revisiting the relationship between systolic time intervals (STI), pressure, and volumes could provide simple-to-use guiding formulas, affordable for daily clinical practice. We have analyzed by echocardiography the hemodynamics of 21 patients with severe symptomatic heart failure with reduced ejection (HFrEF) compared to 12 asymptomatic patients (at risk of heart failure with mild structural disease). The groups were unequivocally separated by ‘classic’ measures (LVEF, LV end-systolic volume (ESV), LV mass, STI). Chen's Ees formula was weakly correlated with LVEF and indexed ESV (ESVi) but better correlated to the pre-ejection period (PEP); PEP/total ejection time (PEP/TET); systolic blood pressure/PEP (SBP/PEP) (P < 0.001). Combining the predictability of the LVEF to the determinant role of SBP/PEP on the Ees variations, we obtained: (SBP^*LVEF)/PEP mm Hg/ms, with an improved R² value (R² = 0.848; P < 0.001). The strongest correlations to VAC were for LVEF (R = −0.849; R² = 0.722) and PEP/TET (R = 0.925; R² = 0.857). By multiple regression, the VAC was strongly predicted (N = 33): (R = 0.975; R² = 0.95): VAC = 0.553–0.009^*LVEF + 3.463^*PEP/TET, and natural logarithm: Ln (VAC) = 0.147–1.4563^*DBP/SBP^*0.9–0.010^*LVEF + 4.207^*PEP/TET (R = 0.987; R² = 0.975; P = 0) demonstrating its exclusive determinants: LVEF, PEP/TET, and DBP/SBP. Considering Ea as a known value, the VAC-derived Ees formula: Ees_d ≈ Ea/(0.553–0.009^*LVEF+3.463^*PEP/TET) was strongly correlated to Chen's Ees formula (R = 0.973; R² = 0.947) being based on SBP, ESV, LVEF, and PEP/TET and no exponential power. Thus, the new index supports our hypothesis, in the limited sample of patients with HFrEF. Indices like SBP/PEP, (SBP^*LVEF)/PEP, PEP/TET, and DBP/SBP deserve further experiments, underlining the major role of the forgotten STI.