Aortic regurgitation and left ventricle remodeling in cardiac magnetic resonance and transthoracic echocardiography

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Medical University of SIlesia

Background

Transthoracic echocardiography (TTE) is the main imaging modality used to assess patients with chronic aortic regurgitation (AR). However, it is not possible to provide a precise quantification in all patients. Our aim was to compare TTE and cardiovascular magnetic resonance (CMR) measurements in grading AR and left ventricle (LV) remodeling.

Methods

A total of 51 consecutive patients with isolated AR in TTE were enrolled into the study and finally forty nine individuals (age: 57.1 (14); 61% males) underwent a non-contrast CMR (2 pts excluded for CMR contraindications). AR severity grading and LV remodeling were assessed according to the current ASE guidelines, including a semi-quantitative and quantitative parameters. All CMR studies were obtained on ecg-gated cine images acquired on 1.5T system (GE Optima MR450w, GE Healthcare, Wisconsin, USA) with a dedicated cardiac coil using a non-contrast protocol, including a quantitative approach (phase-contrast velocity  encoded imaging).

Results

Most of the study patients showed mild symptoms (NYHA I/II/III – 55%/38%/7%; CCS 0/I/II/III/IV – 79%/2%/12%/6%) and typical cardiovascular risk factors: hypertension (83%), dyslipidemia (91%), diabetes (12%) and obesity (16%). Twenty patients (40%) showed combined AV disease and 14 patients (28,5%) had a bicuspid AV. The AR jets were central (53%) or eccentric (47%) and multiple in 7 cases (14%). The inter-modality agreement (TTE-CMR) in AR grading was high in mild AR (91%) and low in mild-to-moderate (12%), moderate-to-severe (10%) and severe (20%) AR. The comprehensive quantitative grading with AR volume (AR vol) and regurgitant fraction (RF) were measurable in TTE in 24 cases and showed a significant association with CMR parameters (AR vol: r = 0.75; p < 0.001 and RF: r = 0.55; p < 0.01). Moreover, CMR revealed significantly larger LV end-diastolic volumes (EDV) (185,5 ± 61ml vs 158,4 ± 61ml; p = 0.03) and a trend towards higher left ventricle ejection fraction (59 ± 8 vs 56 ± 8%; p = 0.08). The association of AR vol and LV EDV was stronger in CMR (r = 0.85; p < 0.0001) compared to TTE (r = 0.6; p = 0.001).

Conclusions

CMR provides a comprehensive assessment of AR severity and LV remodeling with a moderate agreement with TTE.

Rest NT-proBNP but not MR-proANP predicts positive diastolic stress echocardiography test result in patients with preserved left ventricle ejection fraction and heart failure symptoms

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Medical University of Silesia

Introduction

Diastolic dysfunction and heart failure (HF) with preserved ejection fraction are diagnostic challenges in rest transthoracic echocardiography (TTE) and clinical practice. The aim of our study was to evaluate the clinical value of diastolic stress echocardiography (DSE) and its corelation with NT-proBNP and MR-proANP testing in patients with preserved left ventricle ejection fraction (LVEF) and HF symptoms. Methods: All the consecutive patients with HF symptoms, preserved LVEF and suspected diastolic dysfunction were examined with DSE with the protocol according to the EACVI 2016 recommendations. Patients with cardiomyopahties, significant valve defects or extracardiac diseases causing similar symptoms were excluded. The assessment of diastolic function was obtained at rest transthoracic echocardiography (TTE) and at peak exertion in DSE: left atrium volume index (LAVI), average E/e’ >14, peak tricuspid regurgitation velocity >2,8 m/s, septal e’ velocity <7 cm/s or lateral e’< 10cm/s (>50% positive – diastolic dysfunction). Moreover, blood samples for NT-proBNP and MR-proANP were taken just before and 30 minutes after DSE.

Results

The study group included 80 patients (age: 69 ± 8.3 years; 24% males) with dyspnea (NYHA IIa – 53pts; IIb – 17pts; III – 10pts) and risk factors: hypertension (77pts), diabetes (33pts), known coronary artery disease (8pts) and chronic kidney disease (21pts). The rest TTE showed preserved systolic function (LVEF 61.6 ± 8.8%) and normal or indeterminate diastolic function in all patients. DSE revealed positive result for diastolic dysfunction in 17 patients (21%). The levels of NT-proBNP :267(160-518) vs 310(172-522) (p = 0.46) and MR-proANP: 16,2(7,8-542) vs 14,7(6,1-646) p = 0,38 did not significantly change before and after DSE. The ROC analysis showed that age (AUC = 0.720; p < 0.001), LAVI rest (AUC = 0.722, p < 0.01), E/e’ rest (AUC 0.790;p < 0.001) and baseline NT-proBNP (AUC 0.770; p = 0.002) predicted positive DSE. Other parameters, including BMI, baseline E/A, DT or e’ and MR-proANP were not predictive for DSE result. There was a positive correlation between stress NTproBNP and stress LAVI (r = 0.3;p < 0.05) and stress E/e’ (r = 0.5; p < 0.05)  There wasn’t such correlation between MRproANP and stress LAVI and stress E/e’.

Conclusions

Diastolic stress echocardiography revealed diastolic dysfunction in 21% of study patients and improved the diagnostic value of echocardiography. Rest NT-proBNP but not rest MR-proANP predicted positive DSE.

Perinatal and lifetime exposure to methylmercury in the mouse: blood and brain concentrations of mercury to 26 months of age

Chronic, low-level exposures to environmental toxicants, because they often begin prenatally and then persist throughout the individual's lifetime, pose challenging issues to risk assessment. Exposure to low levels of methylmercury through the diet, based largely on consumption of fish and sea mammals, follows this pattern. Early development is considered to be a period of heightened vulnerability during which even low-level exposures may produce undetected, "silent", damage that is revealed only under conditions that challenge the functional capacities of the individual. Aging, with its diminished functional capacities and compensatory reserves provides such a challenge, but, to explore this possibility, requires basic information about blood and brain levels under conditions of chronic lifetime exposure. The current research was undertaken to provide such information. One hundred female B6C3F1/HSD mice were assigned to one of three dose groups, 0, 1, or 3 ppm methylmercury chloride administered in a 5 nM sodium carbonate drinking solution. They were bred with male CBA/J HSD mice to produce the trihybrid offspring B6C3F1/ HSD x CBA/J HSD. Dosing of the females began 4 weeks prior to breeding and continued for the two methylmercury-exposed groups throughout breeding and gestation. The methylmercury-treated litters were split into two subgroups, one exposed throughout its lifetime (set at 26 months) to the original dose, the other exposed through postnatal day 13 (PND 13). Brain and blood concentrations were assayed by cold-vapor atomic absorption. Samples were obtained on PND 4 and 21, and then at the end of months 14 and 26. On PND 4, brain and blood levels closely reflected maternal dosing. In all groups, concentrations fell sharply from PND 4 to 21, but to a greater extent in the perinatal groups. Blood levels in the 1 ppm lifetime group remained unchanged between months 14 and 26, but brain levels rose modestly. In the 3 ppm lifetime group, both brain and blood levels rose significantly between months 14 and 26, suggesting an interaction between dose and age.

Perinatal methanol exposure in the rat. II. Behavioral effects in neonates and adults

The use of methanol as a component of automobile fuel will increase perinatal exposures in the general population. Few studies have addressed questions concerning neurotoxicity stemming from such exposures. In the current study, four cohorts of pregnant Long-Evans rats, each cohort consisting of an exposure and a control group, were exposed to 4500 ppm methanol vapor in Rochester-type inhalation chambers for 6 hr daily beginning on Gestation Day 6. Exposure continued for both dams and pups through Postnatal Day 21 (PND 21) to model gestational and neonatal toxicity in humans. Several behavioral procedures were used to assess exposure effects in the offspring. Male-female littermates were studied whenever possible to examine sex differences, with one pair from a litter for each procedure. Exposure to methanol did not affect suckling latency and nipple attachment on PND 5 or performance on an aversive olfactory conditioning procedure on PND 10. Exposure to methanol did alter performances in a motor activity procedure. Methanol-exposed neonates were less active on PND 18, but more active on PND 25 than the equivalent control group pups. Two operant conditioning procedures, not used previously in this context, assayed other littermates as adults. A fixed ratio schedule required the rat to rotate a running wheel a specified number of revolutions to obtain food-pellet reinforcers. When the fixed ratio requirement changed, number of responses (revolutions) per 1-hr session displayed a complex interaction with treatment. Changes in performance over the course of training differed between males and females depending on exposure to methanol. Compared to initial baseline performances, methanol-exposed males showed decreases, and methanol-exposed females increases, in the rate of running. A stochastic spatial discrimination procedure permitted subjects to respond on any three levers, with the probabilities of food-pellet delivery determined by the location of the preceding response. A reinforcement matrix defined the response sequence required to maximize reinforcements. When the matrix was changed, the methanol-exposed subjects responded less efficiently at asymptotic levels of performance than controls. Across procedures, developmental exposure to 4500 ppm methanol vapor was associated with subtle behavioral changes in both neonates and adults.

Perinatal methanol exposure in the rat. I. Blood methanol concentration and neural cell adhesion molecules

Although the acute toxicity of methanol is well documented, few studies have addressed the consequences of perinatal exposures to the low concentrations that are expected to arise from its proposed use as a component of automobile fuel. This report describes the general research design of a series of studies, the effects of methanol exposures on blood concentrations in dams and neonates, and indices of brain development. Four cohorts of Long-Evans pregnant rats, each cohort consisting of an exposure (n = 12) and a control (n = 12) group, were exposed whole-body to 4500 ppm methanol vapor or air for 6 hr daily beginning on Gestation Day 6. Both dams and pups were then exposed through Postnatal Day 21 (PND 21). Blood methanol concentrations determined by gas chromatography from samples obtained immediately following a 6-hr exposure reached approximately 500-800 micrograms/ml in the dams during gestation and lactation. Average concentrations for pups attained levels about twice those of the dams. Selected offspring from Cohort 4 were exposed for one additional 6-hr session at ages that extended out to PND 52. Regression analyses showed that the blood methanol concentrations of the pups declined until about PND 48, at which time their levels approximated those of their dams. Such pharmacokinetic differences might increase the risks posed to developing organisms. Light-microscopic analysis showed no significant abnormalities in the brains of the methanol-treated animals. However, assays of neural cell adhesion molecules (NCAMs) in brains of pups sacrificed on PND 4 showed staining for both the 140 and the 180 kDa isoforms to be less intense in the cerebellum of exposed animals. NCAM differences were not apparent in animals sacrificed 15 months after their final exposure.

Developmental neurotoxicity of methanol exposure by inhalation in rats

The possibility of widespread methanol exposure via inhalation stemming from its adoption as an automotive fuel or fuel component arouses concerns about the potential vulnerability of the fetal brain. This project was designed to help address such concerns by studying the behavior of neonate and adult rats following perinatal exposure to methanol vapor. Four cohorts of pregnant Long-Evans hooded rats, each cohort consisting of an exposure and a control group, were exposed to 0 parts per million (ppm) (control) or 4,500 ppm methanol vapor for six hours daily beginning on gestation day (GD) 6 with dams and pups then being exposed postnatal day (PND) 21. Exposures took place in 2-m3 Rochester-type inhalation chambers while the animals remained in their plastic breeder cages. Prenatal and postnatal blood methanol concentrations were determined by gas chromatography. Blood methanol concentrations of the dams, measured immediately following a six-hour exposure, were approximately 500 to 800 micrograms/mL throughout gestation and lactation. Average blood methanol concentrations of the pups were about twice those of the dams. Because such results appeared consistently across the other cohorts, we decided to obtain additional data with Cohort 4. Once it had undergone the standard exposure protocol, we selected sets of extra pups from those that had not been assigned previously to the adult phase of behavioral testing. Each set was exposed once, at ages that extended out to PND 52, for one additional six-hour session of exposure to 4,500 ppm methanol. The blood methanol concentrations of these pups declined until about PND 48, at which time they approximated those of the dams. These findings might be accounted for by a process of metabolic maturation in the pups that remains to be identified.