Left Ventricular Ejection Time Measured by Echocardiography Differentiates Neurobehavioral Resilience and Vulnerability to Sleep Loss and Stress

There are substantial individual differences (resilience and vulnerability) in performance resulting from sleep loss and psychosocial stress, but predictive potential biomarkers remain elusive. Similarly, marked changes in the cardiovascular system from sleep loss and stress include an increased risk for cardiovascular disease. It remains unknown whether key hemodynamic markers, including left ventricular ejection time (LVET), stroke volume (SV), heart rate (HR), cardiac index (CI), blood pressure (BP), and systemic vascular resistance index (SVRI), differ in resilient vs. vulnerable individuals and predict differential performance resilience with sleep loss and stress. We investigated for the first time whether the combination of total sleep deprivation (TSD) and psychological stress affected a comprehensive set of hemodynamic measures in healthy adults, and whether these measures differentiated neurobehavioral performance in resilient and vulnerable individuals. Thirty-two healthy adults (ages 27–53; 14 females) participated in a 5-day experiment in the Human Exploration Research Analog (HERA), a high-fidelity National Aeronautics and Space Administration (NASA) space analog isolation facility, consisting of two baseline nights, 39 h TSD, and two recovery nights. A modified Trier Social Stress Test induced psychological stress during TSD. Cardiovascular measure collection [SV, HR, CI, LVET, BP, and SVRI] and neurobehavioral performance testing (including a behavioral attention task and a rating of subjective sleepiness) occurred at six and 11 timepoints, respectively. Individuals with longer pre-study LVET (determined by a median split on pre-study LVET) tended to have poorer performance during TSD and stress. Resilient and vulnerable groups (determined by a median split on average TSD performance) showed significantly different profiles of SV, HR, CI, and LVET. Importantly, LVET at pre-study, but not other hemodynamic measures, reliably differentiated neurobehavioral performance during TSD and stress, and therefore may be a biomarker. Future studies should investigate whether the non-invasive marker, LVET, determines risk for adverse health outcomes.

Left ventricular myocardial performance index in prediabetic patients without coronary artery disease

Background Prediabetes is considered a major risk factor for diabetes mellitus (DM), leading to microvascular and cardiovascular disorders. Myocardial performance index (MPI) is a non-invasive Doppler method for the determination of global ventricular activity. We have not enough knowledge about the effect of prediabetes on the left ventricular (LV) function. We aimed to assess the MPI in prediabetic patients without coronary artery disease (CAD) utilizing echocardiography tissue Doppler imaging (TDI). Results We conducted a randomized controlled study that included fifty prediabetic patients and fifty healthy participants as the control group. All the participants were subjected to laboratory tests and echocardiography TDI to evaluate the LV systolic and diastolic functions We found that the isovolumic relaxation time (IVRT) and MPI values were significantly increased in the prediabetic patients compared to the control group (P < 0.001). In contrast, left ventricular ejection time (ET) was significantly longer in the control group than in prediabetic patients. Conclusion Prediabetes may adversely affect the LV function as assessed by MPI. Screening for prediabetes and early intervention is required for the prevention of cardiovascular morbidity and mortality.

The underlying mechanism of inter-site discrepancies in ejection time measurements from arterial waveforms and its validation in the Framingham Heart Study

Radial applanation tonometry is a well-established method for clinical hemodynamic assessment and is also becoming popular in wrist-worn fitness trackers. The time difference between the foot and the dicrotic notch of the arterial pressure waveform is a well-accepted approximation for the left ventricular ejection time (ET). However, several clinical studies have shown that ET measured from the radial pressure waveform deviates from that measured centrally. In this work, we consider the systolic wave and the dicrotic wave as two independent traveling waves and hypothesize that their wave speed difference leads to the inter-site differences of measured ET (ΔET). Accordingly, we derived a mathematical dicrotic wave decomposition model and identified the most influential factors on ΔET via global sensitivity analysis. In our clinical validation on a heterogeneous cohort (N = 5742) from the Framingham Heart Study (FHS), the local sensitivity analysis results resembled the sensitivity variations patterns of ΔET from model simulations. A regression analysis on FHS data, using morphological features of radial pressure waveforms to estimate the Carotid ET, produced a root mean square error of 3.76 ms and R2 of 0.91. The proposed dicrotic wave decomposition model can explain the inter-site ET measurement discrepancies observed in the clinical data of FHS and can facilitate the precise identification of ET with radial pressure waveforms. Therefore, the proposed model will improve various physics-based pulse wave analysis methods as well as prospective artificial intelligence methods for tackling the subsequent big data produced­ from widespread wearable radial pressure monitoring.

A Close Examination of the Use of Systolic Time Intervals in the Calculation of Impedance Derived Cardiac Autonomic Balance and Regulation

Traditionally, impedance derived measures of cardiac autonomic balance (CAB) and regulation (CAR) are calculated using indices of heart rate variability (HRV) that primarily reflect parasympathetic nervous system activity (e.g., high-frequency HRV | HF-HRV) and pre-ejection period (PEP; a systolic time interval and measure of sympathetic activity). However, HF-HRV and PEP are considered measures of chronotropic and inotropic cardiac influence, respectively. Left ventricular ejection time (LVET) is a systolic time interval that reflects sympathetic chronotropic influence, and therefore may be a more appropriate measure for calculating CAB and CAR compared to PEP. Thus, the current study evaluates both PEP and LVET in the calculation of CAB and CAR. Data from 158 healthy participants (mean age = 19.09 years old, SD = 1.84 years) were available for analyses. CAB and CAR values were calculated using both HF-HRV and the root mean square of successive differences, in addition to both PEP and LVET, in accordance with previously established guidelines. Analyses showed that correlations were significantly weaker between CAB and CAR calculated using LVET for both HF (z = 5.12, p &lt; 0.001) and RMSSD (z = 5.26, p &lt; 0.001) than with PEP. These data suggest that LVET, compared to PEP, provides better “autonomic space” as evidenced by a lack of correlation between CAB and CAR computed using LVET. We stress that future research consider calculating CAB and CAR using chronotropic measures for both parasympathetic and sympathetic activity, as doing so may yield more accurate and independent measures of cardiac autonomic activity compared to a mixture of inotropic (i.e., PEP) and chronotropic (i.e., HF-HRV) measures.

Nucleated Red Blood Cells as Markers of Perinatal Adaptation in Preterm Neonates Receiving Minimally Invasive Surfactant Therapy

Objective The study aimed to assess the association of nucleated red blood cells (NRBC), a surrogate of intrauterine hypoxia, and elevated pulmonic vascular resistance (E-PVR) and oxygen requirement after minimally invasive surfactant therapy (MIST). Study Design Retrospective study of a cohort of preterm neonates that received MIST in a single unit. Results NRBC were measured in 65 of 75 (87%) neonates administered MIST during the period. In total, 22 of 65 (34%) infants had pre-MIST echocardiography (ECHO).Neonates with elevated NRBC (predefined as >5 × 109/L, n = 16) required higher post-MIST fraction of inspired oxygen (FiO2) than neonates with normal NRBC (<1 × 109/L, n = 17; FiO2 = 0.31 ± 0.10 and 0.24 ± 0.04, respectively, p = 0.02).NRBC correlated positively with % of time in right to left ductal shunt (r = 0.51, p = 0.052) and inversely with right ventricular stroke volume (r = −0.55, p = 0.031) and time to peak velocity to right ventricular ejection time ratio (r = −0.62, p < 0.001). Conclusion Elevated NRBC are associated with elevated FiO2 after MIST and elevated E-PVR. Intrauterine hypoxia may impact postnatal circulatory adaptations and oxygen requirement. Key Points

Assessment of Right Heart Functions in Children with Mild Cystic Fibrosis

Background Cystic fibrosis (CF) is a multisystemic disease that prevalently involves the lungs. Hypoxemia occurs due to the existing of progressive damage to the pulmonary parenchyma and pulmonary vessels. The condition may cause systolic and diastolic dysfunction to the right ventricle due to the effects of high pulmonary artery systolic pressure (PASP). The study aimed to determine echocardiographic alterations in PASP, right ventricle (RV) anatomy, and functions in mild CF children. Materials and Methods RV anatomy, systolic, and diastolic functions were evaluated with conventional echocardiographic measurements. Estimated PASP was used measured with new echocardiographic modalities, including pulmonary artery acceleration time (PAAT), right ventricular ejection time (RVET), and their ratio (PAAT/RVET). The obtained echocardiographic data were statistically compared between the patient group and the control group. Results The study consisted of 30 pediatric patients with mild CF and 30 healthy children with similar demographics. In patient group, conventional parameters disclosed differences in RV anatomy, both systolic and diastolic functions of RV compared with the healthy group. We did not compare the patient group with published standard data because of the wide range variability. However, new echocardiographic parameters showed notable increase in pulmonary artery pressure compared with values of control group and published standard data (p<0.001). Conclusion Elevated PASP, RV failure, and Cor pulmonale usually begin early in children with mild CF. In addition to routine echocardiographic measurements to evaluate RV, we recommend the use of new echocardiographic modalities for routine examinations and in the follow up of children with mild CF.

Comparison of maternal third trimester hemodynamics between singleton pregnancy and twin pregnancy

Objectives The impedance cardiography (ICG) technique measures the variation of impedance in the thorax due to the physical contractile activity of the heart. Twin pregnancy is characterized by greater maternal hemodynamic changes than a singleton pregnancy. Methods In a study on 121 pregnant women in the last trimester we performed ICG, evaluating the following hemodynamic parameters: stroke volume, heart rate, cardiac output, ventricular ejection time, left ventricular ejection time, thoracic impedance, and systemic vascular resistance. Results The study included singleton and twin pregnancies. Heart rate values in women with single fetus was lower than in those carrying twins (85 vs. 100 beats/min, p=0.021) as were the stroke volume values (64 vs. 83 mL, p=0.010) and the cardiac output (p<0.0001). Systemic vascular resistance decreased in twin pregnancies compared to singleton pregnancy (p=0.023). Conclusions ICG studies are rare, and the validation of their results is an ongoing process. However, the ICG technique is applicable in the third trimester of pregnancy and can yield important information regarding the hemodynamic profile of singleton and twin pregnancies, revealing maternal heart changes specific to twin pregnancies.