Ventricular Volume Measurements Research Articles

Changes in the hemodynamic profile when establishing mechanical ventilation in patients with ischemic heart disease and coronary disease: Measurement with thoracic bioreactance

Breathing affects cardiac output on a cycle-by-cycle basis, through changes in pressure and intrathoracic volume of key components in cardiovascular function Hence, heart–lung interactions affect cardiovascular functioning and the heart's ability to adapt. The heart–lung interaction is an area of applied physiology broadly studied but in Colombia, this is the first trial ever done with a thoracic bioreactance monitor. The hemodynamic profiles of 38 patients scheduled for myocardial revascularization were measured at the Fundación Clínica Abood Shaio using thoracic bioreactance monitor, which provided ventricular volume and cardiac output measurements. The ventilator volumes and pressures with which corrections were made to interpret the effects of mechanical ventilation were recorded.

Cambios en el perfil hemodinámico al instaurar la ventilación mecánica en pacientes con cardiopatía isquémica y enfermedad coronaria. Medición con biorreactancia torácica

Breathing affects cardiac output on a cycle-by-cycle basis, through changes in pressure and intrathoracic volume of key components in cardiovascular function Hence, heart-lung inter-actions affect cardiovascular functioning and the heart's ability to adapt. The heart-lung interaction is an area of applied physiology broadly studied but in Colombia, this is the first trial ever done with a thoracic bioreactance monitor (NICOM). The hemodynamic profiles of 38 patients scheduled for myocardial revascularization were measured at the Fundación Clínica Abood Shaio using NICOM, which provided ventricular volume and cardiac output measurements. The ventilator volumes and pressures with which corrections were made to interpret the effects of mechanical ventilation were recorded.

Myocardial fibrosis in patients with myotonic dystrophy type 1: a cardiovascular magnetic resonance study

BackgroundMyotonic dystrophy type 1 (DM1) is associated with increased cardiac morbidity and mortality. Therefore, assessment of cardiac involvement and risk stratification for sudden cardiac death is crucial. Nevertheless, optimal screening-procedures are not clearly defined. ECG, echocardiography and Holter-monitoring are useful but insufficient. Cardiovascular magnetic resonance (CMR) can provide additional information of which myocardial fibrosis may be relevant.The purpose of this study was to describe the prevalence of myocardial fibrosis in patients with DM1 assessed by CMR, and the association between myocardial fibrosis and abnormal findings on ECG, Holter-monitoring and echocardiography.MethodsWe selected 30 unrelated patients with DM1: 18 patients (10 men, mean age 51 years) with, and 12 patients (7 men, mean age 41 years) without abnormal findings on ECG and Holter-monitoring.Patients were evaluated with medical history, physical examination, ECG, Holter-monitoring, echocardiography and CMR.ResultsMyocardial fibrosis was found in 12/30 (40%, 9 men). The presence of myocardial fibrosis was associated with the following CMR-parameters: increased left ventricular mass (median (range) 55 g/m2 (43–83) vs. 46 g/m2 (36–64), p = 0.02), increased left atrial volume (median (range) 52 ml/m2 (36–87) vs. 46 ml/m2 (35–69), p = 0.04) and a trend toward lower LVEF (median (range) 63% (38–71) vs. 66% (60–80), p = 0.06). Overall, we found no association between the presence of myocardial fibrosis and abnormal findings on: ECG (p = 0.71), Holter-monitoring (p = 0.27) or echocardiographic measurements of left ventricular volumes, ejection fraction or global longitudinal strain (p = 0.18).ConclusionPatients with DM1 had a high prevalence of myocardial fibrosis which was not predicted by ECG, Holter-monitoring or echocardiography. CMR add additional information to current standard cardiac assessment and may prove to be a clinically valuable tool for risk stratification in DM1.

Inter-observer variability of LV mass and volumes with compressed sensing

Background Recently developed compressed sensing (CS) SSFP sequences significantly reduce data acquisition time thereby reducing patient breath-hold and scan time relative to standard techniques. The variability of ventricular functional (VF) analysis of CS data is not known so this study investigated the inter-observer variation of left ventricular (LV) mass and volume measurements compared to standard SSFP acquisitions.

Electrocardiographically gated 11C-hydroxyephedrine PET for the simultaneous assessment of cardiac sympathetic and contractile functions

Application of the electrocardiographically (ECG) gated positron emission tomography (PET) technique with (11)C-hydroxyephedrine (HED) would allow the simultaneous assessment of cardiac sympathetic and contractile functions. However, there are uncertainties regarding the diagnostic accuracy of left ventricular (LV) volume measurements using ECG-gated HED-PET. The purpose of this study was to clarify the minimal requirement of count statistics to measure LV volumes with ECG-gated HED-PET and to investigate the reliability of the measurements. Five healthy volunteers and 11 patients with heart failure underwent a 40-min list-mode PET scan after an injection of HED (197 ± 35 MBq). The list-mode data were histogrammed into multiple sets of acquisition periods at 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, 12.0 Mcount/bin and reconstructed into corresponding gated images using an iterative algorithm. The LV end-diastolic volume (LVEDV), the LV end-systolic volume (LVESV), and the LV ejection fraction (LVEF) were calculated in each acquisition period. These values were compared with those obtained by cardiac magnetic resonance imaging (MRI). Possible effects of HED retention on the accuracy of the volume measurements were investigated. Collecting less than 4.0 Mcount/bin resulted in noisy cardiac images. The lower counts resulted in underestimation in the volume measurements. Reasonably accurate volume measurements required equal to or greater than 6.0 Mcount/bin. This corresponded to 7.0 ± 1.9 min (range, 4.0-10.3 min) for the acquisition period. Volumetric results using the 6.0 Mcount/bin data highly correlated with cardiac MRI (LVEDV: r = 0.85, p < 0.0001; LVESV: r = 0.89, p < 0.0001; LVEF: r = 0.77, p < 0.01). The HED retention did not affect the volumetric results compared to the MRI volumetry. The volumetric accuracy with ECG-gated HED-PET was affected by the count statistics rather than the HED retention. LV volume measurements were feasible with 10-min acquisition period for most of the patients. This technique allows the simultaneous assessment of cardiac sympathetic and contractile functions without the need for an additional injection or scanning time, thus reducing overall costs for diagnostic imaging.

Abstract 18878: Development of a Unique Mode of Cardiac Remodeling in Muscular Dystrophy Patients

The muscular dystrophies (MD) represent an array of inherited myogenic disorders involving mutations and dysregulations of a variety of cytoskeleton or nuclear proteins. Many MD patients also develop a commitant cardiomyopathy. Despite the high incidence of end-stage cardiomyopathy in MD patients there is limited data regarding the mode of maladaptive cardiac remodeling that develops in these patients. In this retrospective study, we examined the hypothesis that MD patients with a cardiomyopathy develop a unique mode of cardiac remodeling as compared to patients with other forms of nonischemic cardiomyopathy. We examined the cardiac MRIs of 3 cohorts (N = 35 per cohort): patients with neuromuscular disorders with associated cardiomyopathy; patients with primary idiopathic nonischemic cardiomyopathy (NICM); and healthy patients from the Dallas Heart Study (DHS). The cardiac MRIs in each group were reviewed, assessing objective measurements of left ventricular ejection fraction (LVEF), mass (LVM), and end diastolic volume (LVEDV). LVM and LVEDV were indexed for body surface area. In addition, left ventricular concentricity 0.67 (LV Conc 0.67 = LVM / LVEDV 0.67 ), a surrogate marker for wall thickness known to decrease in advanced nonischemic heart failure, was computed for each patient. Despite a preserved ejection fraction in the neuromuscular cohort compared to the NICM cohort (58% vs. 30 %, p&lt;0.05), both displayed similar reduced LV Conc 0.67 (4.69 ± 1.05 and 5.16 ± 1.47) compared to the DHS cohort (7.27 ± 0.83). However, whereas the nonischemic cohort demonstrated hypertrophy with marked dilation (95.8 vs. 84.6 g/m 2 and 119.4 vs. 54.7 mL/m 2 , DHS comparison, p&lt;0.05), the neuromuscular cohort demonstrated a reduced cardiac mass (65.6 vs. 84.6 g/m 2 , p&lt;0.05) with only moderate dilation (74.5 vs. 54.7 mL/m 2 , p&lt;0.05) compared to the DHS population. In conclusion, our data suggests that MD patients develop a unique mode of cardiac remodeling and highlights that novel signaling pathways are involved in the development of cardiomyopathy in these patients.

A Physiological Controller for Turbodynamic Ventricular Assist Devices Based on a Measurement of the Left Ventricular Volume

The current article presents a novel physiological control algorithm for ventricular assist devices (VADs), which is inspired by the preload recruitable stroke work. This controller adapts the hydraulic power output of the VAD to the end-diastolic volume of the left ventricle. We tested this controller on a hybrid mock circulation where the left ventricular volume (LVV) is known, i.e., the problem of measuring the LVV is not addressed in the current article. Experiments were conducted to compare the response of the controller with the physiological and with the pathological circulation, with and without VAD support. A sensitivity analysis was performed to analyze the influence of the controller parameters and the influence of the quality of the LVV signal on the performance of the control algorithm. The results show that the controller induces a response similar to the physiological circulation and effectively prevents over- and underpumping, i.e., ventricular suction and backflow from the aorta to the left ventricle, respectively. The same results are obtained in the case of a disturbed LVV signal. The results presented in the current article motivate the development of a robust, long-term stable sensor to measure the LVV.

Cardiac MRI in the Assessment of Cardiac Injury and Toxicity From Cancer Chemotherapy

During the past 30 years, there has been a significant decrease in cancer mortality rates, predominantly attributable to improvements in treatment options.1 However, survivors are at increased risk of premature cardiac disease,2 both because of the overlap in risk factors for cancer and cardiovascular disease3 and the cardiotoxic effects of cancer chemotherapy. Two chemotherapeutic agent classes that are commonly associated with cardiotoxicity are the anthracyclines and tyrosine kinase inhibitors, both of which can cause left ventricular (LV) dysfunction and heart failure (HF).4,5 Mechanisms of cardiac injury from cancer therapy have been summarized elsewhere.4,6 Briefly, anthracycline cardiotoxicity has been attributed to reactive oxygen species formation, transcriptional changes in intracellular adenosine triphosphate production in cardiac myocytes, and, more recently, through interaction with cardiac topoisomerase IIβ.4,6 Trastuzumab cardiotoxicity seems to be because of inhibition of cardiomyocyte human epidermal growth factor receptor 2, resulting in ATP depletion and contractile dysfunction.4 Other proposed mechanisms include immune-mediated destruction of cardiomyocytes.4,6 At the tissue level, early anthracycline toxicity has been associated with myocardial inflammation,7–9 vacuolization,9–12 and cell swelling/edema.11,13 These changes seem to occur before myocardial functional abnormalities.11,13 Later stages of toxicity are associated with myocardial fibrosis.14,15 Unfortunately, the use of myocardial biopsy is not feasible for diagnostic purposes in this setting. However, once HF manifests, the 2-year mortality can be as high as 60%.16 This emphasizes the importance of early recognition of cardiac injury and institution of cardioprotective therapy in an effort to prevent development of HF and allow uninterrupted completion of cancer therapy.17 Thus, the diagnosis is dependent on either direct evidence of myocardial damage or functional disturbance. Either signal may be identified …

Feasibility of left ventricular volume measurements by three-dimensional speckle tracking echocardiography depends on image quality and degree of left ventricular enlargement: Validation study with cardiac magnetic resonance imaging

BackgroundNovel 3-dimensional echocardiography with speckle tracking imaging (3D-STE) may have advantages in assessing left ventricular (LV) volume through a cardiac cycle. The feasibility of 3D-STE may be affected by image quality and LV morphology. Methods and resultsWe studied 64 patients (38 men, age 55±12 years) who underwent cardiac magnetic resonance imaging (CMRI) and 3D-STE on the same day. LV end-diastolic volume (EDV) and end-systolic volume (ESV) were measured by both modalities. Imaging qualities were quantified in each of 6 LV segments by an imaging quality score (IQS) of 1–3, and scores were averaged (mean IQS) at end-diastole and end-systole. Compared to CMRI, 3D-STE showed a tendency to underestimate LV volume measurements, but not significantly (EDV: bias=−18±37ml; ESV: bias=−10±34ml), and measurements correlated well with those by CMRI (EDV: R=0.80, ESV: R=0.86, ejection fraction: R=0.75, p<0.001). The absolute differences of LVEDV and ESV between 3D-STE and CMRI correlated significantly with mean IQS (LVEDV, R=−0.35, p=0.005; LVESV, R=−0.30, p=0.02). Based on the medium value of LVEDV by CMRI (127ml), subjects were classified into the small (<127ml) and large LVEDV (≧127ml) groups. In the large LVEDV group, mean IQS significantly correlated with the absolute differences of LVEDV (mean IQS, r=−0.45, p=0.01), despite no significant correlation in the small LVEDV group. Conclusion3D-STE could measure LV volume as well as CMRI, however, its accuracy depends on the quality of the acquired image and particularly on enlargement of the left ventricle.

Interinstitutional Measurements of Left Ventricular Volumes, Speckle-Tracking Strain, and Dyssynchrony Using Three-Dimensional Echocardiography

Three-dimensional echocardiographic (3DE) analysis provides better measurements of left ventricular (LV) volumes, ejection fraction, myocardial deformation, and dyssynchrony. Many studies have shown that this technique has high intrainstitutional reproducibility. However, interinstitutional reproducibility is low, limiting its adoption. The aim of this study was to determine if standardization of training could reduce the interinstitutional variability in 3DE data analysis. In total, 50 full-volume, transthoracic 3DE data sets of the left ventricle were analyzed by two readers. Measurements obtained included LV volumes, ejection fraction, global longitudinal strain, and two dyssynchrony indices. The cases represented a wide spectrum of ejection fraction. After initial analysis of 21 studies, readers formally met to standardize their analytic approach on six additional cases. Five months after the intervention, 23 new cases were analyzed. Paired t tests were performed to identify systematic institutional differences in measurements. Interinstitutional variability was quantified using intraclass correlation coefficients and variability. Before the intervention, there was a systematic bias in LV volumes, which was eliminated after intervention. Intraclass correlation coefficients showed that the intervention improved agreement in measurements of LV volumes, strain, and dyssynchrony between the two centers and decreased variability. A simple intervention to standardize analysis can reduce interinstitutional variability of measurements obtained from 3DE analysis. This intervention is needed before the use of 3DE measurement in multicenter trials and to increase the reproducibility of such measurements in routine clinical practice.

Comparison of accelerated and nonaccelerated MRI in ADNI: Effects on measures of brain and ventricular volumes and rates of atrophy

Comparison of accelerated and nonaccelerated MRI in ADNI: Effects on measures of brain and ventricular volumes and rates of atrophy

Comparison of accelerated and nonaccelerated MRI in ADNI: Effects on measures of brain and ventricular volumes and rates of atrophy

Comparison of accelerated and nonaccelerated MRI in ADNI: Effects on measures of brain and ventricular volumes and rates of atrophy

Effect of acute endotoxemia on analog estimates of mean systemic pressure

Dynamic estimates of mean systemic pressure based on a Guytonian analog model (Pmsa) appear accurate under baseline conditions but may not remain so during septic shock because blood volume distribution and resistances between arterial and venous beds may change. Thus, we examined the effect of acute endotoxemia on the ability of Pmsa, estimated from steady-state cardiac output, right atrial pressure, and mean arterial pressure, to reflect our previously validated instantaneous venous return measure of mean systemic pressure (Pmsi), derived from beat-to-beat measures of right ventricular stroke volume and right atrial pressure during positive pressure ventilation. We studied 6 splenectomized pentobarbital-anesthetized close chested dogs. Right ventricular stroke volume was measured by a pulmonary arterial electromagnetic flow probe. Instantaneous venous return measure of mean systemic pressure and Pmsa were calculated during volume loading and removal (±100-mL bolus increments ×5) both before (control) and 30 minutes after endotoxin infusion (endo). Cardiac output increased (2628 ± 905 vs 3560 ± 539 mL/min; P < .05) and mean arterial pressure decreased (107 ± 16 vs 56 ± 12 mm Hg; P < .01) during endo. Changes in Pmsi and Pmsa correlated during both control and endo (r2 = 0.7) with minimal bias by Bland-Altman analysis (mean difference ± 95% confidence interval, 0.47 ± 5.04 mm Hg). We conclude that changes in Pmsa accurately tracts Pmsi under both control and endo.

Comparison of Echocardiographic Measurements of Left Ventricular Volumes to Full Volume Magnetic Resonance Imaging in Normal and Diseased Rats

Clinical two-dimensional (2D) and clinical three-dimensional echocardiography are validated against cardiac magnetic resonance imaging (CMR), the gold standard for left ventricular (LV) volume measurement. In rodents, there is no widely accepted echocardiographic measure of whole LV volumes, and CMR measurements vary among studies. The aim of this study was to compare LV volumes by 2D echocardiography (using a hemisphere-cylinder [HC] model) with HC and full-volume (FV) CMR in normal and diseased rats to measure the impact of geometric models and imaging modalities. Rats (n= 27) underwent ascending aortic banding, myocardial infarction induction by either permanent left anterior descending coronary artery ligation or ischemia-reperfusion, and sham thoracotomy. Subsequently, end-diastolic volume, end-systolic volume, and ejection fraction were measured using an HC 2D echocardiographic model combining parasternal short-axis and long-axis measurements, and these were compared with HC and FV CMR. Diseased groups showed LV dilatation and dysfunction. HC echocardiographic and FV CMR measures of end-diastolic volume, end-systolic volume, and ejection fraction were correlated. On Bland-Altman plots, end-diastolic volumes were concordant between both methods, while HC echocardiography underestimated end-systolic volumes, resulting in a modest overestimation of ejection fractions compared with FV CMR. Other 2D echocardiographic geometric models offered less concordance with FV CMR than HC. HC CMR overestimated LV volumes compared with FV CMR, while HC echocardiography underestimated HC CMR volumes. Echocardiography underestimated corresponding LV dimensions by CMR, particularly short axis. Concordant measures of LV volume and function were obtained using (1) a relatively simple HC model of the left ventricle inclusive of two orthogonal 2D echocardiographic planes and (2) FV CMR in normal and diseased rats. The HC model appeared to compensate for the underestimation of LV dimensions by echocardiography.

Left Ventricular Energy Model Predicts Adverse Events in Women With Suspected Myocardial Ischemia: Results From The NHLBI-Sponsored Women's Ischemia Syndrome Evaluation (WISE) Study.

To assess the prognostic value of a left ventricular energy-model in women with suspected myocardial ischemia. The prognostic value of internal energy utilization (IEU) of the left ventricle in women with suspected myocardial ischemia is unknown. Women (n=227, mean age 59±12 years, range 31-86), with symptoms of myocardial ischemia, underwent myocardial perfusion imaging (MPI) assessment for regional perfusion defects along with measurement of ventricular volumes separately by gated Single Photon Emission Computed Tomography (SPECT) (n= 207) and magnetic resonance imaging (MRI) (n=203). During follow-up (40±17 months), time to first major adverse cardiovascular event (MACE, death, myocardial infarction or hospitalization for congestive heart failure) was analyzed using MRI and gated SPECT variables. Adverse events occurred in 31 (14%). Multivariable Cox models were formed for each modality: IEU and wall thickness by MRI (Chi-squared 34, p<0.005) and IEU and systolic blood pressure by gated SEPCT (Chi-squared 34, p<0.005). The models remained predictive after adjustment for age, disease history and Framingham risk score. For each Cox model, patients were categorized as high-risk if the model hazard was positive and not high-risk otherwise. Kaplan-Meier analysis of time to MACE was performed for high-risk vs. not high-risk for MR (log rank 25.3, p<0.001) and gated SEPCT (log rank 18.2, p<001) models. Among women with suspected myocardial ischemia a high internal energy utilization has higher prognostic value than either a low EF or the presence of a myocardial perfusion defect assessed using two independent modalities of MR or gated SPECT.

936Left ventricular stroke volume measurement accordance between magnetic resonance volumetry and phase contrast flow methods

936Left ventricular stroke volume measurement accordance between magnetic resonance volumetry and phase contrast flow methods

Are measures of left ventricular systolic performance during low dose dobutamine stress echocardiograms repeatable over time?

To establish the test-retest reliability and the normal dose-response relationship of echocardiographic measures of Left Ventricular (LV) contractile function to low dose dobutamine stress in healthy individuals. Thirty healthy volunteers (23 males, 7 females) with an average age of 38 ± 13 years underwent dobutamine stress echocardiography (DSE) (at successive doses of 0, 5, 10, and 20 mcg/kg/min) on two occasions, separated by 14 days. Ejection fraction (EF) was determined from 2D echocardiographic measures of left ventricular (LV) end diastolic and end systolic volumes. Longitudinal strain (S) and strain rate (SR) were measured using 2D speckle tracking analysis from three consecutive cardiac cycles. The Intraclass Correlation Coefficient (ICC) and the Coefficient of Variation (CV) were calculated to assess reliability and variability of the study population's EF, S, and SR responses to increasing doses of dobutamine. Left ventricular S and EF gradually increased with low doses of dobutamine but reached a plateau between 10 and 20 mcg/kg/min. Strain rate, however, gradually increases with each increasing dose of dobutamine. These responses were replicated on Day 2 with a high degree of reliability as determined from the ICC and low variability as determined from the CV, which fell within acceptable limits (<10 %). Left ventricular EF, S and SR can be measured during DSE with a high degree of test-retest reliability, and may be of clinical value when serial follow up of DSE measures of LV performance is indicated over time.

A Probabilistic Patch-Based Label Fusion Model for Multi-Atlas Segmentation With Registration Refinement: Application to Cardiac MR Images

The evaluation of ventricular function is important for the diagnosis of cardiovascular diseases. It typically involves measurement of the left ventricular (LV) mass and LV cavity volume. Manual delineation of the myocardial contours is time-consuming and dependent on the subjective experience of the expert observer. In this paper, a multi-atlas method is proposed for cardiac magnetic resonance (MR) image segmentation. The proposed method is novel in two aspects. First, it formulates a patch-based label fusion model in a Bayesian framework. Second, it improves image registration accuracy by utilizing label information, which leads to improvement of segmentation accuracy. The proposed method was evaluated on a cardiac MR image set of 28 subjects. The average Dice overlap metric of our segmentation is 0.92 for the LV cavity, 0.89 for the right ventricular cavity and 0.82 for the myocardium. The results show that the proposed method is able to provide accurate information for clinical diagnosis.

Real Time Three‐Dimensional Echocardiography for Quantification of Ventricular Volumes, Mass, and Function in Children with Congenital and Acquired Heart Diseases

Quantitative measurement of left ventricular (LV) volumes, mass, and function is one of the most common and important indications for echocardiography. These measurements are among the most powerful tools for diagnosis and prognosis of congenital and acquired heart diseases and for assessment of medical, percutaneous, and surgical interventions. Awareness is also growing of the importance of right ventricular (RV) volume, mass, and function in many cardiopulmonary diseases. Furthermore, there are challenges and opportunities to measure the volume, mass, and function of complex chambers such as the left atrium, right atrium, and the univentricular heart. As echocardiography continues to be the imaging modality of choice for these measurements, the strengths and limitations of M-mode, two-dimensional (2D), and recently three-dimensional (3D) echocardiographic (3DE) methodologies for accurate and reproducible measurement of these indices have been extensively investigated for congenital and acquired heart diseases. Evidence suggests that 3DE provides improved accuracy and reproducibility over 2D methods for measurement of LV volume and function calculation in adults and in children. Data have accumulated on the utility of 3DE for measuring chamber volumes and function for the RV and for the single ventricle, which may become more widely used in clinical and research arenas in the future. Finally, new advanced modes of analysis such as 3D strain and synchrony analysis by 3DE are promising methodologies that warrant further investigation.

Measurement of cardiac function using dual catheterization in the Dahl SS rat on low salt

The assessment of cardiovascular function in both animal and human studies has traditionally focused on left ventricular pressure and volume measurements. However, quantifying the interaction of left ventricular function with the right ventricle and cardiovascular system as a whole extends this functional assessment to the systems level. Computational models of the heart and circulatory system incorporating left and right ventricular function have been developed but experimental data describing simultaneous function of both right and left side of the heart have not been previously measured. Here, we studied cardiac performance in rats by measuring left ventricular pressure‐volume and right ventricular pressure simultaneously using a pressure‐volume conductance catheter in the left ventricle and a pressure‐tip catheter in the right ventricle. This study focuses on development of the experimental protocol and using it to assess normal cardiovascular function in the Dahl SS rat (SS/JrHsdMcwiCrl) on low salt as a baseline for comparative studies. It was found that this dual catheterization measurement method sufficiently informs our computational model, defines cardiac and cardiovascular system function and provides an excellent platform for future comparison of cardiovascular system function between strains on different diets such as Dahl SS and SS.13BN on low and high salt.