Right ventricle dimensions and function in response to acute hypoxia in healthy human subjects

Correlation between worsening pneumonitis and right ventricular systolic function in critically ill patients with COVID-19

BACKGROUND

The pneumonitis associated with coronavirus disease 2019 (COVID-19) infection impacts the right ventricle (RV). However, the association between the disease severity and right ventricular systolic function needs elucidation.

METHOD

We conducted a retrospective study of 108 patients admitted to critical care with COVID-19 pneumonitis to examine the association between tricuspid annular plane systolic excursion (TAPSE) by transthoracic echocardiography as a surrogate for RV systolic function with PaO2/FiO2 ratio as a marker of disease severity and other respiratory parameters.

RESULTS

The median age was 59 years [51, 66], 33 (31%) were female, and 63 (58%) were mechanically ventilated. Echocardiography was performed at a median of 3 days [2, 12] following admission to critical care. The PaO2/FiO2 and TAPSE medians were 20.5 [14.4, 32.0] and 21 mm [18, 24]. There was a statistically significant, albeit weak, association between the increase in TAPSE and the worsening of the PaO2/FiO2 ratio (r2 = 0.041, p = 0.04). This association was more pronounced in the mechanically ventilated (r2 = 0.09, p = 0.02). TAPSE did not correlate significantly with FiO2, PaO2, PaCO2, pH, respiratory rate, or mechanical ventilation. Patients with a TAPSE ≥ 17 mm had a considerably worse PaO2/FiO2 ratio than a TAPSE < 17 mm (18.6 vs. 32.1, p = 0.005). The PaO2/FiO2 ratio predicted TAPSE (OR = 0.94, p = 0.004) with good area under the curve (0.72, p = 0.006). Moreover, a PaO2/FiO2 ratio < 26.7 (moderate pneumonitis) predicted TAPSE > 17 mm with reasonable sensitivity (67%) and specificity (68%).

CONCLUSION

In patients admitted to critical care with COVID-19 pneumonitis, TAPSE increased as the disease severity worsened early in the course of the disease, especially in the mechanically ventilated. A TAPSE within the normal range is not necessarily reassuring in early COVID-19 pneumonitis.

Right ventricular performance during acute hypoxic exercise

Acute hypoxia increases pulmonary arterial (PA) pressures, though its effect on right ventricular (RV) function is controversial. The objective of this study was to characterize exertional RV performance during acute hypoxia. Ten healthy participants (34 ± 10 years, 7 males) completed three visits: visits 1 and 2 included non-invasive normoxic (fraction of inspired oxygen (F i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) = 0.21) and isobaric hypoxic (F i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$  = 0.12) cardiopulmonary exercise testing (CPET) to determine normoxic/hypoxic maximal oxygen uptake (V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ ). Visit 3 involved invasive haemodynamic assessments where participants were randomized 1:1 to either Swan-Ganz or conductance catheterization to quantify RV performance via pressure-volume analysis. Arterial oxygen saturation was determined by blood gas analysis from radial arterial catheterization. During visit 3, participants completed invasive submaximal CPET testing at 50% normoxicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ and again at 50% hypoxicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ (F i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$  = 0.12). Median (interquartile range) values for non-invasiveV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ values during normoxic and hypoxic testing were 2.98 (2.43, 3.66) l/min and 1.84 (1.62, 2.25) l/min, respectively (P < 0.0001). Mean PA pressure increased significantly when transitioning from rest to submaximal exercise during normoxic and hypoxic conditions (P = 0.0014). Metrics of RV contractility including preload recruitable stroke work, dP/dtmax , and end-systolic pressure increased significantly during the transition from rest to exercise under normoxic and hypoxic conditions. Ventricular-arterial coupling was maintained during normoxic exercise at 50%V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ . During submaximal exercise at 50% of hypoxicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ , ventricular-arterial coupling declined but remained within normal limits. In conclusion, resting and exertional RV functions are preserved in response to acute exposure to hypoxia at anF i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$  = 0.12 and the associated increase in PA pressures. KEY POINTS: The healthy right ventricle augments contractility, lusitropy and energetics during periods of increased metabolic demand (e.g. exercise) in acute hypoxic conditions. During submaximal exercise, ventricular-arterial coupling decreases but remains within normal limits, ensuring that cardiac output and systemic perfusion are maintained. These data describe right ventricular physiological responses during submaximal exercise under conditions of acute hypoxia, such as occurs during exposure to high altitude and/or acute hypoxic respiratory failure.

Increasing Levels of Positive End-expiratory Pressure Cause Stepwise Biventricular Stroke Work Reduction in a Porcine Model

BACKGROUND

Positive end-expiratory pressure (PEEP) is commonly applied to avoid atelectasis and improve oxygenation in patients during general anesthesia but affects cardiac pressures, volumes, and loading conditions through cardiorespiratory interactions. PEEP may therefore alter stroke work, which is the area enclosed by the pressure-volume loop and corresponds to the external work performed by the ventricles to eject blood. The low-pressure right ventricle may be even more susceptible to PEEP than the left ventricle. The authors hypothesized that increasing levels of PEEP would reduce stroke work in both ventricles.

METHODS

This was a prospective, observational, experimental study. Six healthy female pigs of approximately 60 kg were used. PEEP was stepwise increased from 0 to 5, 7, 9, 11, 13, 15, 17, and 20 cm H2O to cover the clinical spectrum of PEEP. Simultaneous, biventricular invasive pressure-volume loops, invasive blood pressures, and ventilator data were recorded.

RESULTS

Increasing PEEP resulted in stepwise reductions in left (5,740 ± 973 vs. 2,303 ± 1,154 mmHg · ml; P < 0.001) and right (2,064 ± 769 vs. 468 ± 133 mmHg · ml; P < 0.001) ventricular stroke work. The relative stroke work reduction was similar between the two ventricles. Left ventricular ejection fraction, afterload, and coupling were preserved. On the contrary, PEEP increased right ventricular afterload and caused right ventriculo-arterial uncoupling (0.74 ± 0.30 vs. 0.19 ± 0.13; P = 0.01) with right ventricular ejection fraction reduction (64 ± 8% vs. 37 ± 7%, P < 0.001).

CONCLUSIONS

A stepwise increase in PEEP caused stepwise reduction in biventricular stroke work. However, there are important interventricular differences in response to increased PEEP levels. PEEP increased right ventricular afterload leading to uncoupling and right ventricular ejection fraction decline. These findings may support clinical decision-making to further optimize PEEP as a means to balance between improving lung ventilation and preserving right ventricular function.

EDITOR’S PERSPECTIVE

Fitness to fly for children and adolescents after Fontan palliation

Introduction

At cruising altitude, the cabin pressure of passenger aircraft needs to be adjusted and, therefore, the oxygen content is equivalent to ambient air at 2,500 masl, causing mild desaturation and a rising pulmonary vascular resistance (PVR) in healthy subjects. For Fontan patients with passive pulmonary perfusion, a rising PVR can cause serious medical problems. The purpose of this fitness to fly investigation (FTF) is to assess the risk of air travel for children and adolescents after Fontan palliation.

Methods

We investigated 21 Fontan patients [3-14y] in a normobaric hypoxic chamber at a simulated altitude of 2,500 m for 3 h. Oxygen saturation, heart rate, and regional tissue saturation in the forehead (NIRS) were measured continuously. Before entering the chamber, after 90 and 180 min in the hypoxic environment, blood gas analysis and echocardiography were performed.

Results

Heart rate and blood pressure did not show significant intraindividual changes. Capillary oxygen saturation (SaO₂) decreased significantly after 90 min by a mean of 5.6 ± 2.87% without further decline. Lactate, pH, base excess, and tissue saturation in the frontal brain did not reach any critical values. In the case of open fenestration between the tunnel and the atrium delta, P did not increase, indicating stable pulmonary artery pressure.

Conclusion

All 21 children finished the investigation successfully without any adverse events, so flying short distance seems to be safe for most Fontan patients with good current health status. As the baseline oxygen saturation does not allow prediction of the maximum extent of desaturation and adaption to a hypoxic environment takes up to 180 min, the so-called hypoxic challenge test is not sufficient for these patients. Performing an FTF examination over a period of 180 min allows for risk assessment and provides safety to the patients and their families, as well as the airline companies.

Right ventricular function is associated with 28-day mortality in myocardial infarction complicated by cardiogenic shock: A retrospective observational study

Background

Right ventricular (RV) function is increasingly being recognised as an important factor influencing outcomes in ST elevation myocardial infarction (STEMI) complicated by cardiogenic shock (CS). In this study, we investigated RV echocardiographic parameters' association with 28-day mortality in patients admitted to intensive care with STEMI complicated by CS with reduced left ventricle ejection fraction (LVEF).

Method

We performed a retrospective analysis of patients admitted to intensive care unit (ICU) in a single tertiary cardiac centre over a 34-month period with STEMI complicated by CS and LVEF < 40%. Clinical and echocardiographic data were collected and correlated with 28-day mortality.

Results

One-hundred patients were included with a mean age of 62.6 ±12.7 years and 78% were male. Mortality at 28 days was 37%. Respectively, 85%, 40% and 25% of patients required mechanical ventilation, mechanical circulatory support and renal replacement therapy. Tricuspid annulus peak systolic velocity (RV S') was significantly higher in survivors (12 ± 3.3 v 10 ± 3.5 cm/s, p = 0.03) and was an independent predictor of mortality (odds ratio 1.2, 95% confidence interval 1.1-1.4, p = 0.04). RV S' of 10.5 cm/s exhibited best sensitivity and specificity (64% and 65%, respectively; p = 0.02) for mortality. The Kaplan-Meier curve demonstrated 85% risk of 28-day mortality for RV S' < 10.5 cm/s v 53% for RV S' > 10.5 cm/s (p = 0.02).

Conclusion

RV function is associated 28-day mortality in patients admitted to ICU with STEMI complicated by CS with reduced LVEF. RV S' predicted mortality with good sensitivity and specificity.

Effects of exercise training in hypoxia versus normoxia on fat-reducing in overweight and/or obese adults: A systematic review and meta-analysis of randomized clinical trials

Objective: Fat loss theory under various oxygen conditions has been disputed, and relevant systematic review studies are limited. This study is a systematic review and meta-analysis to assess whether hypoxic exercise training (HET) leads to superior fat-reducing compared with normoxic exercise training (NET).

Methods: We searched PubMed, Web of Science, CNKI, ProQuest, Google Scholar, Cochrane Library, and EBSCOhost from inception to June 2022 for articles comparing the effects of hypoxic and normoxic exercise on body composition indicators, glycometabolism, and lipometabolism indicators in obese and overweight adults. Only randomized controlled trials (RCTs) were included. The effect sizes were expressed as standardized mean difference (SMD) and 95% confidence intervals (CI). Between-study heterogeneity was examined using the I² test and evaluated publication bias via Egger’s regression test. The risk of bias assessment was performed for each included trial using Cochrane Evaluation Tool second generation. The meta-analysis was performed by using R 4.1.3 and RevMan 5.3 analytic tools.

Results: A total of 19 RCTs with 444 subjects were analyzed according to the inclusion and exclusion criteria. Among them, there were 14 English literature and five Chinese literature. No significant difference in body composition (SMD -0.10, 95% CI -0.20 to -0.01), glycometabolism and lipid metabolism (SMD -0.01, 95% CI -0.13 to -0.10) has been observed when comparing the HET and NET groups. We only found low heterogeneity among trials assessing glycometabolism and lipometabolism (I² = 20%, p = 0.09), and no publication bias was detected.

Conclusion: The effects of HET and NET on fat loss in overweight or obese people are the same. The application and promotion of HET for fat reduction need further exploration.

A change of heart: mechanisms of cardiac adaptation to acute and chronic hypoxia

Over the last 100 years, high‐altitude researchers have amassed a comprehensive understanding of the global cardiac responses to acute, prolonged and lifelong hypoxia. When lowlanders are exposed to hypoxia, the drop in arterial oxygen content demands an increase in cardiac output, which is facilitated by an elevated heart rate at the same time as ventricular volumes are maintained. As exposure is prolonged, haemoconcentration restores arterial oxygen content, whereas left ventricular filling and stroke volume are lowered as a result of a combination of reduced blood volume and hypoxic pulmonary vasoconstriction. Populations native to high‐altitude, such as the Sherpa in Asia, exhibit unique lifelong or generational adaptations to hypoxia. For example, they have smaller left ventricular volumes compared to lowlanders despite having larger total blood volume. More recent investigations have begun to explore the mechanisms underlying such adaptive responses by combining novel imaging techniques with interventions that manipulate cardiac preload, afterload, and/or contractility. This work has revealed the contributions and interactions of (i) plasma volume constriction; (ii) sympathoexcitation; and (iii) hypoxic pulmonary vasoconstriction with respect to altering cardiac loading, or otherwise preserving or enhancing biventricular systolic and diastolic function even amongst high altitude natives with excessive erythrocytosis. Despite these advances, various areas of investigation remain understudied, including potential sex‐related differences in response to high altitude. Collectively, the available evidence supports the conclusion that the human heart successfully adapts to hypoxia over the short‐ and long‐term, without signs of myocardial dysfunction in healthy humans, except in very rare cases of maladaptation.

Continuous Heart Rate Dynamics Preceding In-Hospital Pulseless Electrical Activity or Asystolic Cardiac Arrest of Respiratory Etiology

INTRODUCTION

Respiratory failure is a common cause of pulseless electrical activity (PEA) and asystolic cardiac arrest, but the changes in heart rate (HR) pre-arrest is not well described. We describe HR dynamics prior to in-hospital cardiac arrest (IHCA) among PEA/asystole arrest patients with respiratory etiology.

METHODS

In this retrospective study, we evaluated 139 patients with 3-24 hours of continuous electrocardiogram data recorded preceding PEA/asystole IHCA from 2010-2017. We identified respiratory failure cases by chart review and evaluated electrocardiogram data to identify patterns of HR changes, sinus bradycardia or sinus arrest, escape rhythms, and development right ventricular strain prior to IHCA.

RESULTS

A higher proportion of respiratory cases (58/73, 79%) fit a model of HR response characterized by tachycardia followed by rapid HR decrease prior to arrest, compared to non-respiratory cases (30/66, 45%, p<0.001). Among the 58 respiratory cases fitting this model, 36 (62%) had abrupt increase in HR occurring 64 (IQR 23-191) minutes prior to arrest, while 22 (38%) had stable tachycardia until time of HR decrease. Mean peak HR was 123±21 bpm. HR decrease occurred 3.0 (IQR 2.0-7.0) minutes prior to arrest. Sinus arrest occurred during the bradycardic phase in 42/58 of cases; escape rhythms were present in all but 2/42 (5%) cases. Right ventricular strain ECG pattern, when present, occurred at a median of 2.2 (IQR -0.05-17) minutes prior to onset of HR decrease.

CONCLUSION

IHCAs of respiratory etiology follow a model of HR increase from physiologic compensation to hypoxia, followed by rapid HR decrease prior to arrest.

Right Ventricular Response to Acute Hypoxia Exposure: A Systematic Review

Background: Acute hypoxia exposure is associated with an elevation of pulmonary artery pressure (PAP), resulting in an increased hemodynamic load on the right ventricle (RV). In addition, hypoxia may exert direct effects on the RV. However, the RV responses to such challenges are not fully characterized. The aim of this systematic review was to describe the effects of acute hypoxia on the RV in healthy lowland adults.

Methods: We systematically reviewed PubMed and Web of Science and article references from 2005 until May 2021 for prospective studies evaluating echocardiographic RV function and morphology in healthy lowland adults at sea level and upon exposure to simulated altitude or high-altitude.

Results: We included 37 studies in this systematic review, 12 of which used simulated altitude and 25 were conducted in high-altitude field conditions. Eligible studies reported at least one of the RV variables, which were all based on transthoracic echocardiography assessing RV systolic and diastolic function and RV morphology. The design of these studies significantly differed in terms of mode of ascent to high-altitude, altitude level, duration of high-altitude stay, and timing of measurements. In the majority of the studies, echocardiographic examinations were performed within the first 10 days of high-altitude induction. Studies also differed widely by selectively reporting only a part of multiple RV parameters. Despite consistent increase in PAP documented in all studies, reports on the changes of RV function and morphology greatly differed between studies.

Conclusion: This systematic review revealed that the study reports on the effects of acute hypoxia on the RV are controversial and inconclusive. This may be the result of significantly different study designs, non-compliance with international guidelines on RV function assessment and limited statistical power due to small sample sizes. Moreover, the potential impact of other factors such as gender, age, ethnicity, physical activity, mode of ascent and environmental factors such as temperature and humidity on RV responses to hypoxia remained unexplored. Thus, this comprehensive overview will promote reproducible research with improved study designs and methods for the future large-scale prospective studies, which eventually may provide important insights into the RV response to acute hypoxia exposure.

Cardiovascular injuries and SARS-COV-2 infection: focus on elderly people

The novel coronavirus disease (COVID-19) has hit the healthcare system worldwide. The risk of severe infection and mortality increases with advancing age, especially in subjects with comorbidities such as cardiovascular disease, hypertension, diabetes, obesity and cancer. Moreover, cardiovascular complications such as myocardial injury, heart failure and thromboembolism are frequently observed in COVID-19 cases, and several biomarkers (troponin, NTproBNP and D-Dimer) have been identified as prognostic indicators of disease severity and worst outcome. Currently, there is no specific therapy against SARS-CoV-2, although many medications are under investigation. The aim of this review will be to explore the intertwined relationship between COVID-19 disease and the cardiovascular system, focusing on elderly population. The available supportive treatments along with the related concerns in elderly patients, due to their comorbidities and polypharmacotherapy, will be explored.

The Association Between Notching of the Right Ventricular Outflow Tract Flow Velocity Doppler Envelope and Impaired Right Ventricular Function After Acute High-Altitude Exposure

Introduction

Pulmonary 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.

Methods

A 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.

Results

After 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.

Conclusion

HA 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.

Exaggerated Cardiac Contractile Response to Hypoxia in Adults Born Preterm

Individuals born prematurely have smaller hearts, cardiac limitations to exercise, and increased overall cardiometabolic risk. The cardiac effects of acute hypoxia exposure as another physiologic stressor remain under explored. The purpose of this study was to determine the effects of hypoxia on ventricular function in adults born preterm. Adults born moderately to extremely preterm (≤32 weeks gestation or <1500 g, N = 32) and born at term (N = 18) underwent cardiac magnetic resonance imaging under normoxic (21% O₂) and hypoxic (12% O₂) conditions to assess cardiovascular function. In normoxia, cardiac function parameters were similar between groups. During hypoxia, the right ventricular (RV) contractile response was significantly greater in participants born premature, demonstrated by greater increases in RV ejection fraction (EF) (p = 0.002), ventricular-vascular coupling (VVC) (p = 0.004), and strain (p < 0.0001) measures compared to term-born participants, respectively. Left ventricular contractile reserve was similar to term-born participants. Adults born preterm exhibit an exaggerated contractile response to acute hypoxia, particularly in the RV. This suggests that adults born preterm may have contractile reserve, despite the lack of volume reserve identified in previous exercise studies. However, this exaggerated and hyper-adapted response may also increase their risk for late RV failure.

COVID-19-associated cardiovascular morbidity in older adults: a position paper from the Italian Society of Cardiovascular Researches

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells following binding with the cell surface ACE2 receptors, thereby leading to coronavirus disease 2019 (COVID-19). SARS-CoV-2 causes viral pneumonia with additional extrapulmonary manifestations and major complications, including acute myocardial injury, arrhythmia, and shock mainly in elderly patients. Furthermore, patients with existing cardiovascular comorbidities, such as hypertension and coronary heart disease, have a worse clinical outcome following contraction of the viral illness. A striking feature of COVID-19 pandemics is the high incidence of fatalities in advanced aged patients: this might be due to the prevalence of frailty and cardiovascular disease increase with age due to endothelial dysfunction and loss of endogenous cardioprotective mechanisms. Although experimental evidence on this topic is still at its infancy, the aim of this position paper is to hypothesize and discuss more suggestive cellular and molecular mechanisms whereby SARS-CoV-2 may lead to detrimental consequences to the cardiovascular system. We will focus on aging, cytokine storm, NLRP3/inflammasome, hypoxemia, and air pollution, which is an emerging cardiovascular risk factor associated with rapid urbanization and globalization. We will finally discuss the impact of clinically available CV drugs on the clinical course of COVID-19 patients. Understanding the role played by SARS-CoV2 on the CV system is indeed mandatory to get further insights into COVID-19 pathogenesis and to design a therapeutic strategy of cardio-protection for frail patients.

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

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.

Acute Cor Pulmonale in COVID-19-Related ARDS: Improvement With Almitrine Infusion

Coronavirus disease-19 (COVID-19)-related severe acute respiratory distress syndrome can lead to acute cor pulmonale. We report a case of acute cor pulmonale secondary to severe COVID-19 acute respiratory distress syndrome diagnosed with transesophageal echocardiography. Almitrine infusion allowed rapid enhancement of right ventricular function as well as improvement in oxygenation. (Level of Difficulty: Intermediate.)

Electrocardiographic right ventricular strain precedes hypoxic pulseless electrical activity cardiac arrests: Looking beyond pulmonary embolism

AIM

The role of the right ventricle (RV) in pulseless electrical activity (PEA) is poorly defined outside of pulmonary embolism. We aimed to (1) describe the continuous electrocardiographic (ECG) manifestations of RV strain (RVS) preceding PEA/Asystole in-hospital cardiac arrest (IHCA), and (2) determine the prevalence and clinical causes of RVS in PEA/Asystole IHCA.

METHODS

In this retrospective cross-sectional study, we evaluated 140 patients with continuous ECG data preceding PEA/Asystole IHCA. We iteratively defined the RVS continuous ECG pattern using the development cohort (93 patients). Clinical cause determination was blinded from ECG analysis in the validation cohort (47 patients).

RESULTS

The overall cohort had mean age 62.1 ± 17.1 years, 70% return of spontaneous circulation and 30% survival to discharge. RVS continuous ECG pattern was defined as progressive RV depolarization delay in lead V1 with at least one supporting finding of RV ischaemia or right axis deviation. Using this criterion, 66/140 (47%) cases showed preceding RVS. In patients with RVS, no pulmonary embolism was found in 9/13 (69%) autopsies and 8/10 (80%) CT chest angiograms. The positive and negative predictive value of RVS pattern for diagnosing a respiratory cause of PEA/Asystole in the validation cohort was 81% [95% CI 64-98%] and 58% [95% CI 36-81%], respectively.

CONCLUSION

RVS continuous ECG pattern preceded 47% of PEA/Asystole IHCA and is predictive of a respiratory cause of cardiac arrest, not just pulmonary embolism. These suggest that rapid elevations in pulmonary pressures and resultant RV failure may cause PEA in respiratory failure.

The Right Ventricle During Selective Lung Ventilation for Thoracic Surgery

The right ventricle (RV) has been an area of evolving interest after decades of being ignored and considered less important than the left ventricle. Right ventricular dysfunction/failure is an independent predictor of mortality and morbidity in cardiac surgery; however, very little is known about the incidence or impact of RV dysfunction/failure in thoracic surgery. The pathophysiology of RV dysfunction/failure has been studied in the context of acute respiratory distress syndrome (ARDS), cardiac surgery, pulmonary hypertension, and left ventricular failure, but limited data exist in literature addressing the issue of RV dysfunction/failure in the context of thoracic surgery and one-lung ventilation (OLV). Thoracic surgery and OLV present as a unique situation where the RV is faced with sudden changes in afterload, preload, and contractility throughout the perioperative period. The authors discuss the possible pathophysiologic mechanisms that can affect adversely the RV during OLV and introduce the term RV injury to the myocardium that is affected adversely by the various intraoperative factors, which then makes it predisposed to acute dysfunction. The most important of these mechanisms seems to be the role of intraoperative mechanical ventilation, which potentially could cause both ventilator-induced lung injury leading to ARDS and RV injury. Identification of at-risk patients in the perioperative period using focused imaging, particularly echocardiography, is paramount. The authors also discuss the various RV-protective strategies required to prevent RV dysfunction and management of established RV failure.

When appearances deceive: Echocardiographic changes due to common chest pathology

Most indications for performing echocardiography focus on the evaluation of properties intrinsic to the heart. However, numerous extra-cardiac conditions indirectly convey changes to the echocardiographic appearance through alterations in the governing physiology. Pulmonary embolism increases pulmonary arterial pressure if a sufficient cross-sectional area of the pulmonary vascular bed is occluded. This may result in dilatation of the right ventricle and, in severe cases, concomitant early diastolic septal collapse into the left ventricle. Acute respiratory failure has been shown to yield a similar echocardiographic appearance in experimental conditions due to the resultant pulmonary vasoconstriction. Echocardiography in the presence of pulmonary disease can reveal underlying cardiac pathologies such as pulmonary hypertension that contribute to the clinical severity of respiratory distress. Positive pressure ventilation affects preload, afterload, and compliance of both ventricles. The echocardiographic net result cannot be uniformly anticipated, but provides information on the deciding physiology or pathophysiology. Mediastinal pathology including tumors, herniation of abdominal content, and pleural effusion can often be visualized directly with echocardiography. Mediastinal pathologies adjacent to the heart may compress the myocardium directly, thus facilitating echocardiographic and clinical signs of tamponade in the absence of pericardial effusion. In conclusion, many pathologies of extra-cardiac origin influence the echocardiographic appearance of the heart. These changes do not reflect properties of the myocardium but may well be mistaken for it. Hence, these conditions are essential knowledge to all physicians performing echocardiography across the spectrum from advanced cardiological diagnostics to rapid point-of-care focused cardiac ultrasonography.

Right ventricular dyssynchrony during hypoxic breathing but not during exercise in healthy subjects: a speckle tracking echocardiography study

NEW FINDINGS

What is the central question of this study? Right ventricular dyssynchrony in severe pulmonary hypertension is associated with a poor prognosis. However, it has recently been observed in patients with lung or connective tissue disease and pulmonary artery pressure at the upper limits of normal. The mechanisms of right ventricular dyssynchrony in pulmonary hypertension remain uncertain. What is the main finding and its importance? Acute hypoxic breathing, but not normoxic exercise, induces an increase in right ventricular dyssynchrony detected by speckle tracking echocardiography in healthy subjects. These results add new insights into the determinants of right ventricular dyssynchrony, suggesting a role for systemic factors added to afterload in the pathophysiology of right ventricular inhomogeneity of contraction.

ABSTRACT

Pulmonary hypertension (PH) has been shown to be associated with regional inhomogeneity (or dyssynchrony) of right ventricular (RV) contraction. Right ventricular dyssynchrony is an independent predictor of decreased survival in advanced PH, but has also been reported in patients with only mildly elevated pulmonary artery pressure (PAP). The mechanisms of RV dyssynchrony in PH remain uncertain. Our aim was to evaluate RV regional function in healthy subjects during acute hypoxia and during exercise. Seventeen healthy subjects (24 ± 6 years) underwent a speckle tracking echocardiography of the RV at rest in normoxia and every 15 min during a 60 min exposure to hypoxic breathing ( F I O 2 12%). Ten of the subjects also underwent an incremental cycle ergometry in normoxia to 100 W, with the same echocardiographic measurements. Dyssynchrony was measured as the SD of the times to peak systolic strain of the four basal and mid RV segments corrected for the heart rate (RV-SD4). RV-SD4 increased during hypoxia from 12 ± 7 to 22 ± 11 ms in spite of mild increases in mean PAP (mPAP) from 15 ± 2 to 20 ± 2 mmHg and pulmonary vascular resistance (PVR) from 1.18 ± 0.15 to 1.4 ± 0.15 Wood units (WU). During exercise RV-SD4 did not significantly change (from 12 ± 6 ms to 14 ± 6 ms), while mPAP increased to 25 ± 2 mmHg and PVR was unchanged. These data show that in healthy subjects, RV contraction is inhomogeneous in hypoxia but not during exercise. Since PAP increases more during exercise, RV dyssynchrony in hypoxia may be explained by a combination of mechanical (RV afterload) and systemic (hypoxia) factors.

Effects of Progressive Hypoventilation on Left Ventricular Appearance: An Alternative Etiology of Acute Sonographic Short-Axis D-Shaping

OBJECTIVES

The purpose of this study was to evaluate the effects of progressive hypoventilation on echocardiographic measures of the left ventricular (LV) appearance in a porcine model.

METHODS

Ten piglets were included in the experimental group, and 5 served as controls. The experimental group underwent 3 interventions of progressive hypoventilation (baseline: tidal volume, 240 mL; respiratory frequency, 16 minutes^-1 ; first intervention: tidal volume, 240 mL; respiratory frequency, 8 minutes-1; second intervention: tidal volume, 240 mL; respiratory frequency, 4 minutes^-1 ; and third intervention: tidal volume, 120 mL; respiratory frequency, 4 minutes^-1 ). Respiratory resuscitation was initiated if the MAP decreased to 50% of the baseline level or at the end of the third intervention. Transthoracic sonography and invasive measurements were obtained throughout. The primary end point was the LV end-diastolic eccentricity index, a measure of LV D-shaping.

RESULTS

The median LV end-diastolic eccentricity index increased from 1.1 (interquartile range, 1.0-1.1) at baseline to 1.4 (1.3-1.4) 3 minutes after the third intervention (P < .001) and returned to baseline after resuscitation (P = .093). The MAP declined from 87 mm Hg (81-92 mm Hg) to 50 mmHg (33-66 mm Hg) after initiation of the third intervention (P < .001). The mean pulmonary arterial pressure increased from 20 mm Hg (15-21 mm Hg) to 39 mm Hg (38-40 mm Hg) during the second intervention (P < .001).

CONCLUSIONS

Progressive hypoventilation led to a marked D-configuration of the LV and a sharp decrease in systemic blood pressure. After respiratory resuscitation, sonographic measures normalized. These findings were explainable by the pressure changes observed within the left and right ventricles.