Diagnostic precision and sex differences in quantitative cardiovascular magnetic resonance

Correct medical treatment necessitates a correct diagnosis. Cardiac imaging aims to establish an accurate diagnosis without performing unnecessary invasive procedures. Cardiovascular magnetic resonance (CMR) has emerged as a valuable diagnostic tool in clinical cardiology because of its inherently good soft-tissue contrast, dynamic visualizations and the possibility to perform quantitative tissue characterization. However, diagnostic precision may be affected in quantitative imaging by several factors such as the presence of sex differences, or measurements errors. Therefore, the aim of this thesis was to identify parameters and sex differences that affect precision and accuracy, and to evaluate post-processing methods to increase diagnostic precision. We found that intramyocardial blood affects native myocardial T1 values in patients without focal abnormalities, and that native myocardial T1 values differ between the sexes. We developed a blood correction model that maintained an increase in diagnostic precision by 13% when applied to an independent patient cohort, which furthermore also eliminated sex differences in healthy volunteers in Study I. In Study II, we evaluated a post-processing method called stationary tissue background correction for increasing diagnostic precision in clinical blood flow measurements. We found that the number of patients with a pulmonaryto-systemic blood flow ratio (Qp/Qs) outside of the normal range decreased following stationary tissue background correction. In Study III, we investigated the presence of sex differences in a newly developed myocardial perfusion imaging sequence in healthy volunteers. We found that women have higher myocardial blood volume, myocardial perfusion and myocardial extracellular volume compared to men both at rest and during adenosine stress, which provide mechanistic insight into myocardial physiology. In Study IV, we investigated the clinical accuracy and precision of synthetic scar images (SynLGE) from post-contrast T1 maps compared to conventional scar images (LGE) for diagnosing focal myocardial fibrosis of any etiology. Compared to LGE, SynLGE yielded a sensitivity of 77%, a specificity of 98%, a positive predictive value of 97% and a negative predictive value of 86%. In conclusion, there are sex differences in several aspects of clinical quantitative CMR imaging that may affect diagnostic precision. Post-processing is a powerful tool to improve diagnostic precision both by increasing precision in native myocardial T1 values via blood correction, and in Qp/Qs via stationary tissue background correction. SynLGE can provide complementary confidence in the assessment of focal myocardial fibrosis in complement to conventional LGE, and thereby increase diagnostic accuracy and precision

A general legendre transformation

Thesis (M.A.)-- University of Wichita, College of Liberal Arts and Sciences, Dept. of MathematicsIntroductory Background -- The transform of $x^r$ -- The transform of $P_m(x)$ -- Expansion formulae for $x^r$ and $P_m(x)$ -- A series representation of the general transform of f(x) -- Theorems -- Transforms of derivatives and derivatives of transforms -- Conclusion

Increased cardiac involvement in Fabry disease using blood-corrected native T1 mapping

Fabry disease (FD) is a rare lysosomal storage disorder resulting in myocardial sphingolipid accumulation which is detectable by cardiovascular magnetic resonance as low native T1. However, myocardial T1 contains signal from intramyocardial blood which affects variability and consequently measurement precision and accuracy. Correction of myocardial T1 by blood T1 increases precision. We therefore deployed a multicenter study of FD patients (n = 218) and healthy controls (n = 117) to investigate if blood-correction of myocardial native T1 increases the number of FD patients with low T1, and thus reclassifies FD patients as having cardiac involvement. Cardiac involvement was defined as a native T1 value 2 standard deviations below site-specific means in healthy controls for both corrected and uncorrected measures. Overall low T1 was 135/218 (62%) uncorrected vs. 145/218 (67%) corrected (p = 0.02). With blood-correction, 13/83 previously normal patients were reclassified to low T1. This reclassification appears clinically relevant as 6/13 (46%) of reclassified had focal late gadolinium enhancement or left ventricular hypertrophy as signs of cardiac involvement. Blood-correction of myocardial native T1 increases the proportion of FD subjects with low myocardial T1, with blood-corrected results tracking other markers of cardiac involvement. Blood-correction may potentially offer earlier detection and therapy initiation, but merits further prospective studies

Reference range determination for imaging biomarkers : Myocardial T1

Funding Information NHS‐Endowments. Grant Number: EA0537 University of Aberdeen Elphinstone scholarship We thank the Cardiovascular Medicine Research team at the University of Aberdeen for acquisition of healthy volunteer data.Peer reviewedPostprin

Obesity-Related Oxidative Stress: the Impact of Physical Activity and Diet Manipulation

Obesity-related oxidative stress, the imbalance between pro-oxidants and antioxidants (e.g., nitric oxide), has been linked to metabolic and cardiovascular disease, including endothelial dysfunction and atherosclerosis. Reactive oxygen species (ROS) are essential for physiological functions including gene expression, cellular growth, infection defense, and modulating endothelial function. However, elevated ROS and/or diminished antioxidant capacity leading to oxidative stress can lead to dysfunction. Physical activity also results in an acute state of oxidative stress. However, it is likely that chronic physical activity provides a stimulus for favorable oxidative adaptations and enhanced physiological performance and physical health, although distinct responses between aerobic and anaerobic activities warrant further investigation. Studies support the benefits of dietary modification as well as exercise interventions in alleviating oxidative stress susceptibility. Since obese individuals tend to demonstrate elevated markers of oxidative stress, the implications for this population are significant. Therefore, in this review our aim is to discuss (i) the role of oxidative stress and inflammation as associated with obesity-related diseases, (ii) the potential concerns and benefits of exercise-mediated oxidative stress, and (iii) the advantageous role of dietary modification, including acute or chronic caloric restriction and vitamin D supplementation

Prognostic utility and characterization of left ventricular hypertrophy using global thickness

Cardiovascular magnetic resonance (CMR) can accurately measure left ventricular (LV) mass, and several measures related to LV wall thickness exist. We hypothesized that prognosis can be used to select an optimal measure of wall thickness for characterizing LV hypertrophy. Subjects having undergone CMR were studied (cardiac patients, n = 2543; healthy volunteers, n = 100). A new measure, global wall thickness (GT, GTI if indexed to body surface area) was accurately calculated from LV mass and end-diastolic volume. Among patients with follow-up (n = 1575, median follow-up 5.4 years), the most predictive measure of death or hospitalization for heart failure was LV mass index (LVMI) (hazard ratio (HR)[95% confidence interval] 1.16[1.12–1.20], p < 0.001), followed by GTI (HR 1.14[1.09–1.19], p < 0.001). Among patients with normal findings (n = 326, median follow-up 5.8 years), the most predictive measure was GT (HR 1.62[1.35–1.94], p < 0.001). GT and LVMI could characterize patients as having a normal LV mass and wall thickness, concentric remodeling, concentric hypertrophy, or eccentric hypertrophy, and the three abnormal groups had worse prognosis than the normal group (p < 0.05 for all). LV mass is highly prognostic when mass is elevated, but GT is easily and accurately calculated, and adds value and discrimination amongst those with normal LV mass (early disease)

THE EFFECT OF DRUGS ON MEDULLARY PRESSOR RESPONSES

Abstract not availabl