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Subject characteristics and cardiac volumes at rest for men and women (mean±SD)

Subject characteristics and cardiac volumes at rest for men and women (mean±SD)

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The effects on left and right ventricular (LV, RV) volumes during physical exercise remains controversial. Furthermore, no previous study has investigated the effects of exercise on longitudinal contribution to stroke volume (SV) and the outer volume variation of the heart. The aim of this study was to determine if LV, RV and total heart volumes (T...

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... characteristics are presented in Table 1. All sub- jects reported to be healthy and none of the subjects showed any signs of cardiac disease on the CMR scan. ...

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... Reliability of LV volumetric and mass measurements between all completed RT short-axis stack constructions was tested using ICC to further evaluate necessary image acquisition time. For reliability during exercise, only LVM was compared to ECG-gated images as volumes, but not mass, were expected to differ between these two physiological conditions 17,33,34 . Similarly, RT CMR images analyzed at end inspiration were not used for volumes as ventricular volumes may differ depending on the respiratory state [17][18][19] . ...
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... Several investigators demonstrated exercise stress CMR using an in-room treadmill system followed by a rapid transfer of the subject into the scanner with subsequent imaging [7][8][9][10][11][12]. On the other hand, MR-compatible equipment enabling imaging at 1.5 tesla (T) while the patient is at peak exercise stress was shown to be feasible for the evaluation of blood flow dynamics and ventricular function in healthy volunteers [13][14][15][16][17][18][19][20]. Another proof-of-concept study reported on a 3T compatible ergometer, which allowed the assessment of cardiac morphology and function in healthy subjects [6]. ...
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... Inter-scan reproducibility was not assessed with this study, but has been demonstrated in our institution previously in an Ex-CMR study assessing biventricular volumes using a similar retrospectively gated, respiratory navigated short axis cine sequence [42]. As expected, and demonstrated in prior Ex-CMR studies [16,31,46,47], image quality decreases with increasing exercise intensity, however our study still demonstrated good intra-and inter-observer reproducibility during moderate intensity exercise. ECG interference was encountered in one patient, early in the study, such that miss-triggering occurred at moderate exercise intensity. ...
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... Animal studies initially showed that LA relaxation rate, reservoir volume, and mean and V-wave pressures increase during exercise (198). In humans, the LA volume response to exercise remains unclear; several studies using two-dimensional (2D) volumes or diameters have shown increased maximal and stable minimal LA size (199)(200)(201), whereas others demonstrate the opposite (166,202,203), which may reflect differences in study design. However, both perspectives support an expanded reservoir volume proportionate to increases in SV (59) during exercise along with reservoir phase LA strain (172,195). ...
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With each heartbeat, the right ventricle (RV) inputs blood into the pulmonary vascular (PV) compartment which conducts blood through the lungs at low pressure and concurrently fills the left atrium (LA) for output to the systemic circulation. This overall hemodynamic function of the integrated RV-PV-LA unit is determined by complex interactions between the components that vary over the cardiac cycle but are often assessed in terms of mean pressure and flow. Exercise challenges these hemodynamic interactions as cardiac filling increases, stroke volume augments, and cycle length decreases, with PV pressures ultimately increasing in association with cardiac output. Recent cardio-pulmonary exercise hemodynamic studies have enriched the available data from healthy adults, yielded insight into the underlying mechanisms which modify the PV pressure-flow relationship, and better delineated the normal limits of healthy responses to exercise. This review will examine hemodynamic function of the RV-PV-LA unit using the 2-element Windkessel model for the pulmonary circulation. It will focus on acute PV and LA responses that accommodate increased RV output during exercise, including PV recruitment and distension and LA reservoir expansion, and the integrated mean pressure-flow response to exercise in healthy adults. Finally, it will consider how these responses may be impacted by age-related remodeling and modified by sex-related cardio-pulmonary differences. Studying the determinants and recognizing the normal limits of PV pressure-flow relations during exercise will improve our understanding of cardio-pulmonary mechanisms that facilitate or limit exercise.
... Studies utilising commercially produced cycle ergometers followed in 1998 with the use of the Lode BV MR compatible ergometer (Fig. 3) on a 1.5 T CMR scanner [60]. Whilst the majority of Ex-CMR cycle ergometer studies use this system [29,54,55,, some institutions have created custom made CMR compatible cycle ergometers [25,81,82]. Other approaches include the supine CMR compatible 'stepper' ergometer, that utilises an up/down motion, such as the Lode BV up/down ergometer [83][84][85], Ergospect cardio-stepper [86] and custom built supine steppers as demonstrated in Fig. 4 [87]. ...
... Cycle ergometer Ex-CMR ventricular volume assessment has progressed from imaging during exercise cessation with breath holding [25,67,[70][71][72]81], breath holding during exercise [82,86], free breathing with exercise cessation [54,64,66], to free breathing during continuous exercise [29,83]. Initial studies utilised turbo field echo planar imaging (EPI) with retrospective gating to acquire short axis cine imaging for biventricular volumes during exercise [67,70,71]. ...
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... Excessive motion during exercise however poses a challenge in image acquisition. As a result, investigators have resorted to acquire images following transient cessation of exercise (17), during breath-holds (6,17,18) or using ungated real-time cine imaging (19). Reconstruction of a short axis stack for volumetric analysis from ungated realtime imaging, however, involves complex post-processing analysis in addition to a requirement for bespoke in-house software (19). ...
... Previously, image acquisition techniques using the MRI cycle ergometer have either involved a brief period of exercise cessation (17) or required a breath-hold protocol (6,18) in order to reduce excessive motion artefacts and avoid poor ECG signal. Ungated real-time CMR imaging (19,23,24) has been a method that enabled cine images to be acquired during continuous exercise. ...
... The results of this present study are in line with previous studies of supine exercise, showing a decrease in LV (24,36) and RV (18,23,37) EDVs, particularly during later stages of exercise. Similar to previous exCMR studies, we demonstrated no significant rise in stroke volume with exercise (38). ...
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Background: Cardiovascular magnetic resonance (CMR) image acquisition techniques during exercise typically requires either transient cessation of exercise or complex post-processing, potentially compromising clinical utility. We evaluated the feasibility and reproducibility of a navigated image acquisition method for ventricular volumes assessment during continuous physical exercise. Methods: Ten healthy volunteers underwent supine cycle ergometer (Lode) exercise CMR on two separate occasions using a free-breathing, multi-shot, navigated, balanced steady-state free precession cine pulse sequence. Images were acquired at 3-stages, baseline and during steady-state exercise at 55% and 75% maximal heart rate (HRmax), based on a prior supine cardiopulmonary exercise test. Intra-and inter-observer variability and inter-scan reproducibility were derived. Clinical feasibility was tested in a separate cohort of patients with severe mitral regurgitation (n=6). Results: End-diastolic volume (EDV) of both LV and RV decreased during exercise at 55% and 75% HRmax, although a reduction in RVEDV index was only observed at 75% HRmax. Ejection fractions (EF) for both ventricles were significantly higher at 75% HRmax compared to their respective baselines (LVEF 68%±3% vs. 58%±5%, P=0.001; RVEF 66%±4% vs. 58%±7%, P=0.02). Intra-observer and inter-observer reproducibility of LV parameters was excellent at all 3-stages. Although measurements of RVESV were more variable during exercise, the reproducibility of both RVEF and RV cardiac index was excellent (CV <10%). Inter-scan LV and RV ejection fraction were highly reproducible at all 3 stages, although inter-scan reproducibility of indexed RVESV was only moderate. The protocol was well tolerated by all patients. Conclusions: Exercise CMR using a free-breathing, multi-shot, navigated cine imaging method allows simultaneous assessment of left and right ventricular volumes during continuous exercise. Intra- and inter-observer reproducibility were excellent. Inter-scan LV and RV ejection fraction were also highly reproducible.
... In addition, despite the presence of observations regarding the effect of alterations in heart rate on LV volumes, these studies were done mainly among men and did not provide viable information on the effect of heart rate increase on heart chamber volumes among women. [2][3][4][11][12][13][14][15][16][17][18] CCTA is nowadays widely used for the assessment of CAD. 19 The same imaging study may provide in addition data on the volumes of each of the cardiac chambers, including the LA, RV, and RA, which can be valuable. ...
... Investigations of the effect of increased heart rate on LV volume during physical exercise as opposed to resting are numerous but are mostly performed on men only. [12][13][14][15][16][17][18][21][22][23] This study, which contains a relatively Adjusted to age and variables, which had p < 0.2 in univariate analysis. Hypertension, diabetes mellitus, hyperlipidemia, overweight, chronic obstructive pulmonary disease, anemia, smoking, and b-blocker were considered as potential confounders for inclusion in multivariate analysis. ...
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Background: Currently, normal values of the cardiac chambers' volumes are adjusted only for gender and body surface area (BSA). We aim to investigate the association between the heart rate and the volume of each of the four cardiac chambers using cardiac-gated computed tomography angiography (CCTA). Methods: A total of 350 consecutive patients without known cardiac diseases or significant (>50%) stenosis undergoing CCTA between January 2009 and June 2014 for suspected coronary artery disease were included. Cardiac chamber volumes adjusted to BSA were calculated using automated model-based segmentation analysis software of the CCTA data and correlated with patients' mean heart rate during the scan. Results: There were 240 men and 110 women, median interquartile range age was 55 years (47?61). Women were older 59.0 years (53.7?64) versus 52.0 years (45.0?59.0), had higher prevalence of hyperlipidemia, diabetes mellitus, anemia, and hypothyroidism, and higher median heart rates 64.0 (59.7?66.0) versus 60.0 (55.0?65.0) (p?<?0.001). Men had a negative correlation between the volume of each cardiac chamber and the heart rate [rage_adj?=?(?0.4)?(?0.27), p?<?0.001 for all], whereas such a correlation was not found in women. The multivariate analysis showed that a decrease of five beats per minute was associated with an increase of 4%?5% in volume of each chamber in men. There was no such association among females. Conclusions: Lower heart rate is associated with an increase of each cardiac chamber volume by CCTA in men. This association is not found in women. More extensive studies are required to further elaborate on these gender differences.
... Dobutamine was administered intravenously starting at a dose between 5 and 10 µg/kg/min, and the dose was increased or decreased in intervals of ∼2 min depending on the observed effect on the subject's heart rate and arterial pressure. The target heart rate was 50% higher than the subject's rest heart rate, in order to achieve heart rates in the range of those from previous studies on stress testing with cardiac magnetic resonance (CMR) (Pennell et al., 1992;van Rugge et al., 1994;Roest et al., 2001;Steding-Ehrenborg et al., 2013). Heart rate was monitored continuously throughout the study. ...
... Several studies have investigated the effects of clinically induced stress on cardiovascular function based on non-invasive indices derived from Doppler ultrasound or 2D PC-MRI measurements, such as left ventricular volumes and mitral inflow patterns. In line with our results, these studies have reported a decrease in left ventricular ESV (Steding-Ehrenborg et al., 2013), enhanced mitral peak E and A flows (el-Said et al., 1994;Kilner et al., 1997;Paelinck et al., 2004). In addition, like others (Kilner et al., 1997;Chung et al., 2004;Paelinck et al., 2004), we found a progressive merging of mitral E and A waves as a result of increasing heart rates during stress conditions. ...
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Background: The possibility of non-invasively assessing load-independent parameters characterizing cardiac function is of high clinical value. Typically, these parameters are assessed during resting conditions. However, for diagnostic purposes, the parameter behavior across a physiologically relevant range of heart rate and loads is more relevant than the isolated measurements performed at rest. This study sought to evaluate changes in non-invasive estimations of load-independent parameters of left-ventricular contraction and relaxation patterns at rest and during dobutamine stress. Methods: We applied a previously developed approach that combines non-invasive measurements with a physiologically-based, reduced-order model of the cardiovascular system to provide subject-specific estimates of parameters characterizing left ventricular function. In this model, the contractile state of the heart at each time point along the cardiac cycle is modeled using a time-varying elastance curve. Non-invasive data, including four-dimensional magnetic resonance imaging (4D Flow MRI) measurements, were acquired in nine subjects without a known heart disease at rest and during dobutamine stress. For each of the study subjects, we constructed two personalized models corresponding to the resting and the stress state. Results: Applying the modeling framework, we identified significant increases in the left ventricular contraction rate constant [from 1.5 ± 0.3 to 2 ± 0.5 (p = 0.038)] and relaxation constant [from 37.2 ± 6.9 to 46.1 ± 12 (p = 0.028)]. In addition, we found a significant decrease in the elastance diastolic time constant from 0.4 ± 0.04 s to 0.3 ± 0.03 s (p = 0.008). Conclusions: The integrated image-modeling approach allows the assessment of cardiovascular function given as model-based parameters. The agreement between the estimated parameter values and previously reported effects of dobutamine demonstrates the potential of the approach to assess advanced metrics of pathophysiology that are otherwise difficult to obtain non-invasively in clinical practice.
... Marked hemodynamic recovery during the transition from exercise to imaging (18,30,32,44,45,58) and the technical training and familiarization required of both the patient and imaging staff to achieve rapid and accurate body placement has prevented wide-spread adoption of this approach. Accordingly, several investigators have focused on MRI-compatible cycle ergometers, which allow patients to exercise inside the bore of the magnet (3,24,26,31,33,38,41,47,55,61). Although several studies have evaluated cardiac output dynamics using velocityencoding approaches (5,7,21,25,37,50,57,61), only a few studies have attempted to evaluate ventricular morphology and function (8 -10, 23, 24, 31, 34, 38, 43, 47-49, 51, 55), the vast majority of which have utilized a real-time, ungated freebreathing pulse sequence (8 -10, 31, 34, 51). ...
Article
Cardiac stress testing improves detection and risk assessment of heart disease. Magnetic resonance imaging (MRI) is the clinical gold-standard for assessing cardiac morphology and function at rest; however, exercise MRI has not been widely adapted for cardiac assessment due to imaging and device limitations. Commercially available MR ergometers, together with improved imaging sequences, have overcome many previous limitations, making cardiac stress MRI more feasible. Here, we aimed to demonstrate clinical feasibility, and establish the normative, healthy response to supine exercise MRI. Eight young, healthy subjects, underwent rest and exercise cinematic imaging to measure left ventricular volumes and ejection fraction. To establish the normative, healthy response to exercise MRI we performed a comprehensive literature review and meta-analysis of existing exercise cardiac MRI studies. Results were pooled using a random effects model to define the left ventricular ejection fraction, end-diastolic, end-systolic, and stroke volume responses. Our proof-of-concept data showed a marked increase in cardiac index with exercise, secondary to an increase in both heart rate and stroke volume. The change in stroke volume was driven by a reduction in end-systolic volume, with no change in end-diastolic volume. These findings were entirely consistent with 17 previous exercise MRI studies (226 individual records), despite differences in imaging approach, ergometer, or exercise type. Taken together, the data herein demonstrate that exercise cardiac MRI is clinically feasible, using commercially available exercise equipment and vendor-provided product sequences, and establish the normative, healthy response to exercise MRI.
... As an MRI-based full heart segmentation is a challenging task [172], the heart was simplified by a geometric model mainly consisting of two cropped ellipsoids representing the atria and ventricles as illustrated in Figure A.2a. To best mimic real heart behaviour, the model has only a slight variation in total heart volume, no longitudinal shortening but radial compression as observed at rest [32] and moderate exercise [141]. The six parameters configuring the model (position of base, apex, AVP ES , AVP ED and both short axis dimensions of the AVP) are shown in Figure A.2 and were determined by fitting the model to the outer heart contours in end diastole and end systole and from manual measurements obtained from MRI scans M2. ...
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In clinical practice it is of vital importance to track the health of a patient's cardiovascular system via the continuous measurement of hemodynamic parameters. Cardiac output (CO) and the related stroke volume (SV) are two such parameters of central interest as they are closely linked with oxygen delivery and the health of the heart. Many techniques exist to measure CO and SV, ranging from highly invasive to noninvasive ones. However, none of the noninvasive approaches are reliable enough in clinical settings. To overcome this limitation, we investigated the feasibility and practical applicability of noninvasively measuring SV via electrical impedance tomography (EIT), a safe and low-cost medical imaging modality. In a first step, the unclear origins of cardiosynchronous EIT signals were investigated in silico on a 4D bioimpedance model of the human thorax. Our simulations revealed that the EIT heart signal is dominated by ventricular activity, giving hope for a heart amplitude-based SV estimation. We further showed via simulations that this approach seems feasible in controlled scenarios but also suffers from some limitations. That is, EIT-based SV estimation is impaired by electrode belt displacements and by changes in lung conductivity (e.g. by respiration or liquid redistribution). We concluded that the absolute measurement of SV by EIT is challenging, but trending - that is following relative changes - of SV is more promising. In a second step, we investigated the practical applicability of this approach in three experimental studies. First, EIT was applied on 16 mechanically ventilated patients in the intensive care unit (ICU) receiving a fluid challenge to improve their hemodynamic situation. We showed that the resulting relative changes in SV could be tracked using the EIT lung amplitude, while this was not possible via the heart amplitude. The second study, performed on patients in the operating room (OR), had to be prematurely terminated due to too low variations in SV and technical challenges of EIT in the OR. Finally, the third experimental study aimed at testing an improved measurement setup that we designed after having identified potential limitations of available clinical EIT systems. This setup was tested in an experimental protocol on 10 healthy volunteers undergoing bicycle exercises. Despite the use of subject-specific 3D EIT, neither the heart nor the lung amplitudes could be used to assess SV via EIT. Changes in electrode contact and posture seem to be the main factors impairing the assessment of SV. In summary, based on in silico and in vivo investigations, we revealed various challenges related to EIT-based SV estimation. While our simulations showed that trending of SV via the EIT heart amplitude should be possible, this could not be confirmed in any of the experimental studies. However, in the ICU, where sufficiently controlled EIT measurements were possible, the EIT lung amplitude showed potential to trend changes in SV. We concluded that EIT amplitude-based SV estimation can easily be impaired by various factors such as electrode contact or small changes in posture. Therefore, this approach might be limited to controlled environments with the least possible changes in ventilation and posture. Future research should scrutinize the lung amplitude-based approach in dedicated simulations and clinical trials.