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Preliminary Study of Right Ventricular Dyssynchrony Under High-Altitude Exposure: Determinants and Impacts.

ABSTRACT: The aims of this study were to explore the effect of high-altitude (HA) exposure on the incidence, determinants, and impacts of right ventricular dyssynchrony (RVD). In our study, 108 healthy young men were enrolled, and physiological and echocardiographic variables were recorded at both sea level and 4,100 m. By using two-dimensional speckle-tracking echocardiography, RVD was evaluated by calculating the R-R interval-corrected standard deviation of the time-to-peak systolic strain for the four mid-basal RV segments (RVSD4) and defined by RVSD4 > 18.7 ms. After HA exposure, RVSD4 was significantly increased, and the incidence of RVD was approximately 32.4%. Subjects with RVD showed lower oxygen saturation (SaO2) and RV global longitudinal strain and higher systolic pulmonary artery pressure than those without RVD. Moreover, myocardial acceleration during isovolumic contraction was increased in all subjects and those without RVD, but not in those with RVD. Multivariate logistic regression revealed that SaO2 is an independent determinant of RVD at HA (odds ratio: 0.72, 95% CI: 0.56-0.92; P = 0.009). However, the mean pulmonary artery pressure was linearly correlated with the magnitude of RVD in the presence of Notch. No changes were found in RV fractional area change, tricuspid annular motion, or tricuspid s' velocity between subjects with and without RVD. Collectively, we demonstrated for the first time that HA exposure could induce RVD in healthy subjects, which may be mainly attributed to the decline in SaO2 as well as RV overload; the incidence of RVD was associated with reduced RV regional function and blunted myocardial acceleration.

SUBMITTER: Yang Y

PROVIDER: S-EPMC7343894 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Preliminary Study of Right Ventricular Dyssynchrony Under High-Altitude Exposure: Determinants and Impacts.

Yang Yuanqi Y Liu Chuan C Tian Jingdu J Ding Xiaohan X Yu Shiyong S Bian Shizhu S Yang Jie J Qin Zhexue Z Zhang Jihang J Ke Jingbin J Yuan Fangzhengyuan F Zhang Chen C Rao Rongsheng R Huang Lan L

Frontiers in physiology 20200702

The aims of this study were to explore the effect of high-altitude (HA) exposure on the incidence, determinants, and impacts of right ventricular dyssynchrony (RVD). In our study, 108 healthy young men were enrolled, and physiological and echocardiographic variables were recorded at both sea level and 4,100 m. By using two-dimensional speckle-tracking echocardiography, RVD was evaluated by calculating the R-R interval-corrected standard deviation of the time-to-peak systolic strain for the four ...[more]

PMID: 32714205

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Project description:IntroductionPulmonary artery pressure (PAP) is increased and right ventricular (RV) function is well preserved in healthy subjects upon exposure to high altitude (HA). An increase in PAP may trigger notching of the right ventricular outflow tract Doppler flow velocity envelope (RVOT notch), which is associated with impaired RV function in patients with pulmonary hypertension. However, whether HA exposure can induce RVOT notch formation and the subsequent impact on cardiac function in healthy subjects remains unclear.MethodsA total of 99 subjects (69 males and 30 females) with a median age of 25 years were enrolled in this study; they traveled from 500 to 4100 m by bus over a 2-day period. All subjects underwent a comprehensive physiological and echocardiographic examination 1 day before ascension at low altitude and 15 ± 3 h after arrival at HA. The RVOT notch was determined by the presence of a notched shape in the RVOT Doppler flow velocity envelope. The systolic PAP (SPAP) was calculated as Bernoulli equation SPAP = 4 × (maximum tricuspid regurgitation velocity)2+5 and mean PAP (mPAP) = 0.61 × SPAP+2. Cardiac output was calculated as stroke volume × heart rate. Pulmonary capillary wedge pressure (PCWP) was calculated as 1.9+1.24 × mitral E/e'. Pulmonary vascular resistance (PVR) was calculated as (mPAP-PCWP)/CO.ResultsAfter HA exposure, 20 (20.2%) subjects had an RVOT notch [notch (+)], and 79 (79.8%) subjects did not have an RVOT notch [notch (-)]. In the multivariate logistic regression analysis, the SPAP, right ventricular global longitude strain (RV GLS), and tricuspid E/A were independently associated with the RVOT notch. The SPAP, mPAP, PVR, standard deviations of the times to peak systolic strain in the four mid-basal RV segments (RVSD4), peak velocity of the isovolumic contraction period (ICV), and the peak systolic velocity (s') at the mitral/tricuspid annulus were increased in all subjects. Conversely, the pulse oxygen saturation (SpO2), RV GLS, and tricuspid annulus plane systolic excursion (TAPSE)/SPAP were decreased. However, the increases of SPAP, mPAP, PVR, and RVSD4 and the decreases of SpO2, RV GLS, and TAPSE/SPAP were more pronounced in the notch (+) group than in the notch (-) group. Additionally, increased tricuspid ICV and mitral/tricuspid s' were found only in the notch (-) group.ConclusionHA exposure-induced RVOT notch formation is associated with impaired RV function, including no increase in the tricuspid ICV or s', reduction of RV deformation, deterioration in RV-pulmonary artery coupling, and RV intraventricular synchrony.

Project description:Background and purposeElectromechanical dyssynchrony, manifested by right bundle branch block and regional wall mechanical dysfunction, contributes to inefficient RV function in repaired Tetralogy of Fallot (ToF). This study aims to evaluate the synchronicity of multiple RV walls using two-dimensional multi-plane echocardiography (2D-MPE) in order to augment current understanding of the mechanisms behind RV dyssynchrony.MethodsSixty-nine adult ToF patients [aged 33 (23-45) years; 61% male] and twenty-five matched healthy controls underwent deformational analysis of the RV lateral, anterior, inferior and septal walls following 2D-MPE acquisitions. RV synchronicity was assessed by the intra-RV deformation delay between each basal RV wall and mid-septal segment in addition to mechanical dispersion calculated across four, six and eight segments (MD).ResultsAll RV wall-septum delays plus MD-4 and MD-6 indices were significantly greater in ToF patients compared to healthy controls (p < 0.001-0.03). In ToF patients, the lateral and anterior RV walls were last to reach peak deformation and anterior wall longitudinal strain was lower (p = 0.001). Post systolic shortening of at least one RV wall segment was identified in 19 (28%) ToF patients. Despite similar ECG characteristics, lateral and anterior wall-septum delays were significantly longer in patients with greater degrees of dyssynchrony (73 [37-108]ms vs. 37 [0-63]ms, p = 0.006; 91 [52-116]ms vs. 41 [1-69]ms, p = 0.013), although RV ejection fraction (RVEF) was not significantly lower. MD-4 and MD-8 indices displayed moderate negative associations with RVEF, strengthened by inclusion of lateral wall longitudinal strain (r = 0.64/0.65; p ≤0.01).ConclusionRV dyssynchrony in ToF is characterised by electromechanical delays between the lateral, anterior and septal walls, with anterior wall dysfunction likely associated with surgical repair of the RV outflow tract. Prospectively, 2D-MPE may have an emerging role evaluating RV mechanical response to electrical resynchronisation therapy.

Project description:BackgroundHigh-altitude deacclimatization syndrome (HADAS) is a severe public health issue. The study of the changes in right ventricular function caused by high-altitude deacclimatization (HADA) is of great significance for the prevention and treatment of HADAS.MethodsSix-week-old, male Sprague Dawley (SD) rats were randomly divided into the plain, plateau and the HADA group. Rats in the plateau and plain group were exposed to altitudes of 3,850 and 360 m, respectively, for 12 weeks. Rats in HADA group were exposed to the plateau altitude of 3,850 m for 12 weeks and subsequently transported to the plain altitude of 360 m for 4 weeks. Right ventricular ejection fraction (RVEF), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and myocardial strain parameters, including the global longitudinal strain (GLS), global radial strain (GRS), and global circumferential strain (GCS), were evaluated by 7.0T cardiac magnetic resonance (CMR). The levels of red blood cell (RBC), hemoglobin (HGB), and hematocrit (HCT) in the blood were measured, and hematoxylin-eosin (HE) staining was used to observe the pathological changes in the myocardium.ResultsIn rats in the plateau group, the right ventricular fibrous space was slightly widened, and partial focal steatosis were observed. However, in the HADA group, only a few focal steatoses were found. Rats in the plateau group had elevated levels of RBC, HGB and HCT, increased right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV) and right ventricular stroke volume (RVSV), and decreased right ventricular global longitudinal strain (RVGLS), right ventricular global circumferential strain (RVGCS), and right ventricular global radial strain (RVGRS) compared to rats in the plain group (P<0.001). The RVEDV, RVGCS, and RVGRS in the HADA group basically returned to the plain state. Interestingly, the RVESV in the HADA group was higher, while the RVSV, RVEF, and RVGLS were lower than those in the other two groups.ConclusionsAfter 12 weeks of exposure to high-altitude environment, there were some pathological changes and the whole contractile strain of the right ventricle was observed. Some pathological changes in the myocardial tissue and stroma recovered after returning to the plain for 4 weeks. However, the right ventricular systolic function and strain did not recover completely.

Project description:Background The relative impact of right ventricular ( RV ) electromechanical dyssynchrony versus pulmonary regurgitation ( PR ) on exercise capacity and RV function after tetralogy of Fallot repair is unknown. We aimed to delineate the relative effects of these factors on RV function and exercise capacity. Methods and Results We retrospectively analyzed 81 children with tetralogy of Fallot repair using multivariable regression. Predictor parameters were electrocardiographic QRS duration reflecting electromechanical dyssynchrony and PR severity by cardiac magnetic resonance. The outcome parameters were exercise capacity (percentage predicted peak oxygen consumption) and cardiac magnetic resonance ejection fraction (RV ejection fraction). To understand the relative effects of RV dyssynchrony versus PR on exercise capacity and RV function, virtual patient simulations were performed using a closed-loop cardiovascular system model (CircAdapt), covering a wide spectrum of disease severity. Eighty-one patients with tetralogy of Fallot repair (median [interquartile range { IQR} ] age, 14.48 [11.55-15.91] years) were analyzed. All had prolonged QRS duration (median [IQR], 144 [123-152] ms), at least moderate PR (median [IQR], 40% [29%-48%]), reduced exercise capacity (median [IQR], 79% [68%-92%] predicted peak oxygen consumption), and reduced RV ejection fraction (median [IQR], 48% [44%-52%]). Longer QRS duration, more than PR , was associated with lower oxygen consumption and lower RV ejection fraction. In a multivariable regression analysis, oxygen consumption decreased with both increasing QRS duration and PR severity. CircAdapt modeling showed that RV dyssynchrony exerts a stronger limiting effect on exercise capacity and on RV ejection fraction than does PR , regardless of contractile function. Conclusions In both patient data and computer simulations, RV dyssynchrony, more than PR , appears to be associated with reduced exercise capacity and RV systolic dysfunction in patients after TOF repair.

Dataset Information

Preliminary Study of Right Ventricular Dyssynchrony Under High-Altitude Exposure: Determinants and Impacts.

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Preliminary Study of Right Ventricular Dyssynchrony Under High-Altitude Exposure: Determinants and Impacts.

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