Lower limb hyperthermia augments functional hyperaemia during small muscle mass exercise similarly in trained elderly and young humans

Heat and exercise therapies are recommended to improve vascular health across the lifespan. However, the haemodynamic effects of hyperthermia, exercise and their combination are inconsistent in young and elderly people. Here we investigated the acute effects of local-limb hyperthermia and exercise on limb haemodynamics in nine healthy, trained elderly (69 ± 5 years) and 10 young (26 ± 7 years) adults, hypothesising that the combination of local hyperthermia and exercise interact to increase leg perfusion, albeit to a lesser extent in the elderly. Participants underwent 90 min of single whole-leg heating, with the contralateral leg remaining as control, followed by 10 min of low-intensity incremental single-leg knee-extensor exercise with both the heated and control legs. Temperature profiles and leg haemodynamics at the femoral and popliteal arteries were measured. In both groups, heating increased whole-leg skin temperature and blood flow by 9.5 ± 1.2°C and 0.7 ± 0.2 L min−1 (>3-fold), respectively (P < 0.0001). Blood flow in the heated leg remained 0.7 ± 0.6 and 1.0 ± 0.8 L min−1 higher during exercise at 6 and 12 W, respectively (P < 0.0001). However, there were no differences in limb haemodynamics between cohorts, other than the elderly group exhibiting a 16 ± 6% larger arterial diameter and a 51 ± 6% lower blood velocity following heating (P < 0.0001). In conclusion, local hyperthermia-induced limb hyperperfusion and/or small muscle mass exercise hyperaemia are preserved in trained older people despite evident age-related structural and functional alterations in their leg conduit arteries

A comparison between local wave speed in the carotid and femoral arteries in healthy humans: application of a new method

The wave speed (c) and the arrival time of reflected wave (Trw) in the common left carotid artery and common left femoral artery have been evaluated in 70 healthy subjects, aged 35-55 years with a non-invasive method. Wave speed and the arrival time of reflected waves were determined with InDU-loop and non-invasive wave intensity analysis (ndl) techniques, respectively. Diameter (D) was measured with ultrasound echo wall tracking and velocity (U) was obtained by ultrasonography. A statistical analysis has been carried out in order to establish a potential relation of c and Trw with gender and age in the study population. Subjects have been divided in two classes of age, one from 35 to 45 years and the other from 45 to 55 years. Results show that c and Trw in the femoral artery are higher than those in carotid, in both men and women (P < 0.001). Also, the distance of the reflection (L) site from the point of measurement is higher in the femoral than in the carotid artery. We did not find statistically significant differences between c, age or gender in femoral artery. However, c in the carotid artery increases with age (P < 0.05), but did not change between men and women. In this paper InDU-loop has been used for the first time to determine c and Trw in carotid and femoral arteries in a large population of healthy subjects

How much of the intraaortic balloon volume is displaced toward the coronary circulation?

This is a post-print version of the published article. Copyright @ 2010 The American Association for Thoracic Surgery.This article has been made available through the Brunel Open Access Publishing Fund.Objective: During intraaortic balloon inflation, blood volume is displaced toward the heart (Vtip), traveling retrograde in the descending aorta, passing by the arch vessels, reaching the aortic root (Vroot), and eventually perfusing the coronary circulation (Vcor). Vcor leads to coronary flow augmentation, one of the main benefits of the intraaortic balloon pump. The aim of this study was to assess Vroot and Vcor in vivo and in vitro, respectively. Methods: During intraaortic balloon inflation, Vroot was obtained by integrating over time the aortic root flow signals measured in 10 patients with intraaortic balloon assistance frequencies of 1:1 and 1:2. In a mock circulation system, flow measurements were recorded simultaneously upstream of the intraaortic balloon tip and at each of the arch and coronary branches of a silicone aorta during 1:1 and 1:2 intraaortic balloon support. Integration over time of the flow signals during inflation yielded Vcor and the distribution of Vtip. Results: In patients, Vroot was 6.4% ± 4.8% of the intraaortic balloon volume during 1:1 assistance and 10.0% ± 5.0% during 1:2 assistance. In vitro and with an artificial heart simulating the native heart, Vcor was smaller, 3.7% and 3.8%, respectively. The distribution of Vtip in vitro varied, with less volume displaced toward the arch and coronary branches and more volume stored in the compliant aortic wall when the artificial heart was not operating. Conclusion: The blood volume displaced toward the coronary circulation as the result of intraaortic balloon inflation is a small percentage of the nominal intraaortic balloon volume. Although small, this percentage is still a significant fraction of baseline coronary flow.This article is available through the Open Access Publishing Fund

A comparison of different methods to maximise signal extraction when using central venous pressure to optimise atrioventricular delay after cardiac surgery.

Our group has shown that central venous pressure (CVP) can optimise atrioventricular (AV) delay in temporary pacing (TP) after cardiac surgery. However, the signal-to-noise ratio (SNR) is influenced both by the methods used to mitigate the pressure effects of respiration and the number of heartbeats analysed. This paper systematically studies the effect of different analysis methods on SNR to maximise the accuracy of this technique. We optimised AV delay in 16 patients with TP after cardiac surgery. Transitioning rapidly and repeatedly from a reference AV delay to different tested AV delays, we measured pressure differences before and after each transition. We analysed the resultant signals in different ways with the aim of maximising the SNR: (1) adjusting averaging window location (around versus after transition), (2) modifying window length (heartbeats analysed), and (3) applying different signal filtering methods to correct respiratory artefact. (1) The SNR was 27 % higher for averaging windows around the transition versus post-transition windows. (2) The optimal window length for CVP analysis was two respiratory cycle lengths versus one respiratory cycle length for optimising SNR for arterial blood pressure (ABP) signals. (3) Filtering with discrete wavelet transform improved SNR by 62 % for CVP measurements. When applying the optimal window length and filtering techniques, the correlation between ABP and CVP peak optima exceeded that of a single cycle length (R = 0.71 vs. R = 0.50, p < 0.001). We demonstrated that utilising a specific set of techniques maximises the signal-to-noise ratio and hence the utility of this technique. [Abstract copyright: © 2024 The Author(s).

P24 Restored Physiological Local Carotid Pulse Wave Velocity After Bariatric Surgery in Obese Subjects

AbstractObesity is a risk factor for cardiovascular events and is associated with increased arterial stiffness [1,2]. However, the effect of drastic changes in Body Mass Index (BMI) on arterial mechanics has not been fully investigated. Our study aimed at evaluating changes in local carotid PWV (cPWV) in obese patients before and 6 months after bariatric surgery. N = 20 obese subjects free of cardiovascular events and diabetes (44 ± 9 years, 5 men, BMI = 48.8 ± 7.5 kg/m2) undergoing bariatric surgery were recruited in the Pisa University Hospital (Italy). Flow and diameter waveforms were acquired by ultrasound scanner (Aloka Alpha10, Hitachi Group, Japan) (1 kHz) at the right common carotid artery at baseline, after a 32.4 ± 7.6 days diet period, and 6.5 ± 2.7 months post-intervention. The lnDU-loop method was used for the estimation of cPWV [3]. Basal cPWV was 6.05 ± 1.21 m/s. The 1-month diet period produced a 2 kg/m2 reduction in BMI, while cPWV decreased by approx. 0.6 m/s. 6–7 months after bariatric surgery, BMI dropped to 35.3 ± 6.5 kg/m2 and cPWV furtherly decreased of approx. 0.9 m/s reaching a mean value of 4.57 ± 1.02 m/s (76% of the basal value) (Figure 1). Bariatric surgery and the consequent intensive weight loss produced a significant decrease of arterial stiffness and restored cPWV to physiological values of age-matched healthy subjects [4]. The fast reversal of increased arterial stiffness suggests a functional mechanism possibly related to a reduced haemodynamic load. Moreover, while having a small effect on the BMI, 1-month diet regulation effectively decreased cPWV by 10%, possibly indicating the short-term positive effects of a healthy lifestyle on haemodynamics

Arterial pulse wave modelling and analysis for vascular age studies: a review from VascAgeNet

Arterial pulse waves (PWs) such as blood pressure and photoplethysmogram (PPG) signals contain a wealth of information on the cardiovascular (CV) system that can be exploited to assess vascular age and identify individuals at elevated CV risk. We review the possibilities, limitations, complementarity, and differences of reduced-order, biophysical models of arterial PW propagation, as well as theoretical and empirical methods for analyzing PW signals and extracting clinically relevant information for vascular age assessment. We provide detailed mathematical derivations of these models and theoretical methods, showing how they are related to each other. Finally, we outline directions for future research to realize the potential of modeling and analysis of PW signals for accurate assessment of vascular age in both the clinic and in daily life

The hemodynamic effects of aortic clamping.

Imperial Users onl

Wave intensity analysis in the ventricles, carotid and coronary arteries – What has been learnt during the last 25 years?: Part 2

Wave intensity analysis (WIA) was introduced 25 years ago for the study of arterial wave travel and has since been established as a powerful tool for the investigation of cardio-vascular interaction. Despite the complex mathematical derivation of the method, the implementation is simple. As a time-domain technique, WIA enables the direct association between waves and events during the cardiac cycle. Furthermore, it enables the separation of the pressure (or diameter), velocity and wave intensity waveforms into their forward and backward components, and provides a means for the determination of the timing and magnitude of waves of different origins. Hemodynamic questions at several locations along the vascular tree have been investigated with WIA. Part 2 of this review will focus on the physiological and clinical findings to which WIA has contributed, through clinical and in vivo studies in the ventricles and in the coronary and carotid arteries

Wave intensity analysis in the great arteries — What has been learnt during the last 25 years? Part 1

Wave intensity analysis (WIA) was introduced 25 years ago for the study of arterial wave propagation. The mathematical derivation of the method is complex, but the results are simple to use and WIA has since been established as a valuable technique for investigating the cardio-arterial interaction. WIA has several advantages; the most important of them is that it is a time-domain technique, which enables the direct association between waves and events during the cardiac cycle. Further, WIA allows for the separation of the measured pressure and velocity waveforms, and derived wave intensity, into their forward and backward directions, and also provides a means for the determination of the arrival time of reflected waves to the measurement site. This powerful technique has been used in several locations in the vascular system for investigating a wide range of physiological and clinical questions, but this review will focus on the clinical application of WIA, as demonstrated from in vivo and clinical studies in the aorta, pulmonary arteries and pulmonary veins