Right ventricular adaptation in the critical phase after acute intermediate-risk pulmonary embolism

Immediate cardiopulmonary responses to consecutive pulmonary embolism: a randomized, controlled, experimental study

BACKGROUND

Acute pulmonary embolism (PE) induces ventilation-perfusion mismatch and hypoxia and increases pulmonary pressure and right ventricular (RV) afterload, entailing potentially fatal RV failure within a short timeframe. Cardiopulmonary factors may respond differently to increased clot burden. We aimed to elucidate immediate cardiopulmonary responses during successive PE episodes in a porcine model.

METHODS

This was a randomized, controlled, blinded study of repeated measurements. Twelve pigs were randomly assigned to receive sham procedures or consecutive PEs every 15 min until doubling of mean pulmonary pressure. Cardiopulmonary assessments were conducted at 1, 2, 5, and 13 min after each PE using pressure-volume loops, invasive pressures, and arterial and mixed venous blood gas analyses. ANOVA and mixed-model statistical analyses were applied.

RESULTS

Pulmonary pressures increased after the initial PE administration (p < 0.0001), with a higher pulmonary pressure change compared to pressure change observed after the following PEs. Conversely, RV arterial elastance and pulmonary vascular resistance was not increased after the first PE, but after three PEs an increase was observed (p = 0.0103 and p = 0.0015, respectively). RV dilatation occurred following initial PEs, while RV ejection fraction declined after the third PE (p = 0.004). RV coupling exhibited a decreasing trend from the first PE (p = 0.095), despite increased mechanical work (p = 0.003). Ventilatory variables displayed more incremental changes with successive PEs.

CONCLUSION

In an experimental model of consecutive PE, RV afterload elevation and dysfunction manifested after the third PE, in contrast to pulmonary pressure that increased after the first PE. Ventilatory variables exhibited a more direct association with clot burden.

Changes in Pulmonary Vascular Resistance and Obstruction Score Following Acute Pulmonary Embolism in Pigs

OBJECTIVES

To investigate the contribution of mechanical obstruction and pulmonary vasoconstriction to pulmonary vascular resistance (PVR) in acute pulmonary embolism (PE) in pigs.

DESIGN

Controlled, animal study.

SETTING

Tertiary university hospital, animal research laboratory.

SUBJECTS

Female Danish slaughter pigs (n = 12, ~60 kg).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

PE was induced by infusion of autologous blood clots in pigs. CT pulmonary angiograms were performed at baseline, after PE (first experimental day [PEd0]) and the following 2 days (second experimental day [PEd1] and third experimental day [PEd2]), and clot burden quantified by a modified Qanadli Obstruction Score. Hemodynamics were evaluated with left and right heart catheterization and systemic invasive pressures each day before, under, and after treatment with the pulmonary vasodilators sildenafil (0.1 mg/kg) and oxygen (Fio2 40%). PE increased PVR (baseline vs. PEd0: 178 ± 54 vs. 526 ± 160 dynes; p < 0.0001) and obstruction score (baseline vs. PEd0: 0% vs. 45% ± 13%; p < 0.0001). PVR decreased toward baseline at day 1 (baseline vs. PEd1: 178 ± 54 vs. 219 ± 48; p = 0.16) and day 2 (baseline vs. PEd2: 178 ± 54 vs. 201 ± 50; p = 0.51). Obstruction score decreased only slightly at day 1 (PEd0 vs. PEd1: 45% ± 12% vs. 43% ± 14%; p = 0.04) and remained elevated throughout the study (PEd1 vs. PEd2: 43% ± 14% vs. 42% ± 17%; p = 0.74). Sildenafil and oxygen in combination decreased PVR at day 0 (-284 ± 154 dynes; p = 0.0064) but had no effects at day 1 (-8 ± 27 dynes; p = 0.4827) or day 2 (-18 ± 32 dynes; p = 0.0923).

CONCLUSIONS

Pulmonary vasoconstriction, and not mechanical obstruction, was the predominant cause of increased PVR in acute PE in pigs. PVR rapidly declined over the first 2 days after onset despite a persistent mechanical obstruction of the pulmonary circulation from emboli. The findings suggest that treatment with pulmonary vasodilators might only be effective in the acute phase of PE thereby limiting the window for such therapy.

The hemodynamic interplay between pulmonary ischemia-reperfusion injury and right ventricular function in lung transplantation: a translational porcine model

Lung transplantation (LTx) is a challenging procedure. Following the process of ischemia-reperfusion injury, the transplanted pulmonary graft might become severely damaged, resulting in primary graft dysfunction. In addition, during the intraoperative window, the right ventricle (RV) is at risk of acute failure. The interaction of right ventricular function with lung injury is, however, poorly understood. We aimed to address this interaction in a translational porcine model of pulmonary ischemia-reperfusion injury. Advanced pulmonary and hemodynamic assessment was used, including right ventricular pressure-volume loop analysis. The acute model was based on clamping and unclamping of the left lung hilus, respecting the different hemodynamic phases of a clinical lung transplantation. We found that forcing entire right ventricular cardiac output through a lung suffering from ischemia-reperfusion injury increased afterload (pulmonary vascular resistance from baseline to end experiment P < 0.0001) and induced right ventricular failure (RVF) in 5/9 animals. Notably, we identified different compensation patterns in failing versus nonfailing ventricles (arterial elastance P = 0.0008; stroke volume P < 0.0001). Furthermore, increased vascular pressure and flow produced by the right ventricle resulted in higher pulmonary injury, as measured by ex vivo CT density (correlation: pressure r = 0.8; flow r = 0.85). Finally, RV ischemia as measured by troponin-T was negatively correlated with pulmonary injury (r = -0.76); however, troponin-T values did not determine RVF in all animals. In conclusion, we demonstrate a delicate balance between development of pulmonary ischemia-reperfusion injury and right ventricular function during lung transplantation. Furthermore, we provide a physiological basis for potential benefit of extracorporeal life support technology.NEW & NOTEWORTHY In contrast to the abundant literature of mechanical pulmonary artery clamping to increase right ventricular afterload, we developed a model adding a biological factor of pulmonary ischemia-reperfusion injury. We did not only focus on the right ventricular behavior, but also on the interaction with the injured lung. We are the first to describe this interaction while addressing the hemodynamic intraoperative phases of clinical lung transplantation.

Right-to-left ventricular ratio is higher in systole than diastole in patients with acute pulmonary embolism

OBJECTIVES

In acute pulmonary embolism (PE), the right ventricle (RV) may dilate compromising left ventricular (LV) size, thereby increasing RV/LV ratio. End-diastolic RV/LV ratio is often used in PE risk stratification, though the cause of death is RV systolic failure. We aimed to confirm our pre-clinical observations of higher RV/LV ratio in systole compared to diastole in human patients with PE.

METHODS

We blinded and independently analyzed echocardiograms from 606 patients with PE, evaluated by a Pulmonary Embolism Response Team. We measured RV/LV ratios in end-systole and end-diastole and fractional area change (FAC). Our primary outcome was a composite of 7-day clinical deterioration, treatment escalation or death. Secondary outcomes were 7-day and 30-day all-cause mortality.

RESULTS

RV/LV ratio was higher in systole compared to diastole (median 1.010 [.812-1.256] vs. .975 [.843-1.149], p < .0001). RV/LV in systole and diastole were correlated (slope = 1.30 [95% CI 1.25-1.35], p < .0001 vs. slope = 1). RV/LV ratios in both systole and diastole were associated with the primary composite outcome but not with all-cause mortality.

CONCLUSION

The RV/LV ratio is higher when measured in systole versus in diastole in patients with acute PE. The two approaches had similar associations with clinical outcomes, that is, it appears reasonable to measure RV/LV ratio in diastole.

Impact of sternotomy and pericardiotomy on cardiopulmonary haemodynamics in a large animal model

NEW FINDINGS

What is the central question of this study? Invasive cardiovascular instrumentation can occur through closed- or open-chest approaches. To what extent will sternotomy and pericardiotomy affect cardiopulmonary variables? What is the main finding and its importance? Opening of the thorax decreased mean systemic and pulmonary pressures. Left ventricular function improved, but no changes were observed in right ventricular systolic measures. No consensus or recommendation exists regarding instrumentation. Methodological differences risk compromising rigour and reproducibility in preclinical research.

ABSTRACT

Animal models of cardiovascular disease are often evaluated by invasive instrumentation for phenotyping. As no consensus exists, both open- and closed-chest approaches are used, which might compromise rigour and reproducibility in preclinical research. We aimed to quantify the cardiopulmonary changes induced by sternotomy and pericardiotomy in a large animal model. Seven pigs were anaesthetized, mechanically ventilated and evaluated by right heart catheterization and bi-ventricular pressure-volume loop recordings at baseline and after sternotomy and pericardiotomy. Data were compared by ANOVA or the Friedmann test where appropriate, with post-hoc analyses to control for multiple comparisons. Sternotomy and pericardiotomy caused reductions in mean systemic (-12 ± 11 mmHg, P = 0.027) and pulmonary pressures (-4 ± 3 mmHg, P = 0.006) and airway pressures. Cardiac output decreased non-significantly (-1329 ± 1762 ml/min, P = 0.052). Left ventricular afterload decreased, with an increase in ejection fraction (+9 ± 7%, P = 0.027) and coupling. No changes were observed in right ventricular systolic function or arterial blood gases. In conclusion, open- versus closed-chest approaches to invasive cardiovascular phenotyping cause a systematic difference in key haemodynamic variables. Researchers should adopt the most appropriate approach to ensure rigour and reproducibility in preclinical cardiovascular research.

Effects of Mechanical Ventilation Versus Apnea on Bi-Ventricular Pressure-Volume Loop Recording

Respiration changes intrathoracic pressure and lung volumes in a cyclic manner, which affect cardiac function. Invasive ventricular pressure-volume (PV) loops can be recorded during ongoing mechanical ventilation or in transient apnea. No consensus exists considering ventilatory mode during PV loop recording. The objective of this study was to investigate the magnitude of any systematic difference of bi-ventricular PV loop variables recorded during mechanical ventilation versus apnea. PV loops were recorded simultaneously from the right ventricle and left ventricle in a closed chest porcine model during mechanical ventilation and in transient apnea (n=72). Variables were compared by regression analyses. Mechanical ventilation versus apnea affected regression coefficients for important PV variables including right ventricular stroke volume (1.22, 95% CI [1.08-1.36], p=0.003), right ventricular ejection fraction (0.90, 95% CI [0.81-1.00], p=0.043) and right ventricular arterial elastance (0.61, 95%CI [0.55-0.68], p<0.0001). Right ventricular pressures and volumes were parallelly shifted with Y-intercepts different from 0. Few left ventricular variables were affected, mainly first derivatives of pressure (dP/dt(max): 0.96, 95% CI [0.92-0.99], p=0.016, and dP/dt(min): 0.92, 95% CI [0.86-0.99], p=0.026), which might be due to decreased heart rate in apnea (Y-intercept -6.88, 95% CI [-12.22; -1.54], p=0.012). We conclude, that right ventricular stroke volume, ejection fraction and arterial elastance were mostly affected by apnea compared to mechanical ventilation. The results motivate future standardization of respiratory modality when measuring PV relationships.

The echocardiographic ratio tricuspid annular plane systolic excursion/pulmonary arterial systolic pressure predicts short-term adverse outcomes in acute pulmonary embolism

AIMS

Right ventricular (RV) failure causes death from acute pulmonary embolism (PE), due to a mismatch between RV systolic function and increased RV afterload. We hypothesized that an echocardiographic ratio of this mismatch [RV systolic function by tricuspid annular plane systolic excursion (TAPSE) divided by pulmonary arterial systolic pressure (PASP)] would predict adverse outcomes better than each measurement individually, and would be useful for risk stratification in intermediate-risk PE.

METHODS AND RESULTS

This was a retrospective analysis of a single academic centre Pulmonary Embolism Response Team registry from 2012 to 2019. All patients with confirmed PE and a formal transthoracic echocardiogram performed within 2 days were included. All echocardiograms were analysed by an observer blinded to the outcome. The primary endpoint was a 7-day composite outcome of death or haemodynamic deterioration. Secondary outcomes were 7- and 30-day all-cause mortality. A total of 627 patients were included; 135 met the primary composite outcome. In univariate analysis, the TAPSE/PASP was associated with our primary outcome [odds ratio = 0.028, 95% confidence interval (CI) 0.010-0.087; P < 0.0001], which was significantly better than either TAPSE or PASP alone (P = 0.017 and P < 0.0001, respectively). A TAPSE/PASP cut-off value of 0.4 was identified as the optimal value for predicting adverse outcome in PE. TAPSE/PASP predicted both 7- and 30-day all-cause mortality, while TAPSE and PASP did not.

CONCLUSION

A combined echocardiographic ratio of RV function to afterload is superior in prediction of adverse outcome in acute intermediate-risk PE. This ratio may improve risk stratification and identification of the patients that will suffer short-term deterioration after intermediate-risk PE.

Levosimendan, milrinone, and dobutamine in experimental acute pulmonary embolism

Acute pulmonary embolism is a frequent condition in emergency medicine and potentially fatal. Cause of death is right ventricular failure due to increased right ventricular afterload from both pulmonary vascular obstruction and vasoconstriction. Inodilators are interesting drugs of choice as they may improve right ventricular function and lower its afterload. We aimed to investigate the cardiovascular effects of three clinically relevant inodilators: levosimendan, milrinone, and dobutamine in acute pulmonary embolism. We conducted a randomized, blinded, animal study using 18 female pigs. Animals received large autologous pulmonary embolism until doubling of baseline mean pulmonary arterial pressure and were randomized to increasing doses of each inodilator. Effects were evaluated with bi-ventricular pressure–volume loop recordings, right heart catheterization, and blood gas analyses. Induction of pulmonary embolism increased right ventricular afterload and pulmonary pressure (p < 0.05) causing right ventricular dysfunction. Levosimendan and milrinone showed beneficial hemodynamic profiles by lowering right ventricular pressures and volume (p < 0.001) and improved right ventricular function and cardiac output (p < 0.05) without increasing right ventricular mechanical work. Dobutamine increased right ventricular pressure and function (p < 0.01) but at a cost of increased mechanical work at the highest doses, showing an adverse hemodynamic profile. In a porcine model of acute pulmonary embolism, levosimendan and milrinone reduced right ventricular afterload and improved right ventricular function, whereas dobutamine at higher doses increased right ventricular afterload and right ventricular mechanical work. The study motivates clinical testing of inodilators in patients with acute pulmonary embolism and right ventricular dysfunction.

Outcomes of catheter-directed interventions in high-risk pulmonary embolism-a retrospective analysis

BACKGROUND

First-line treatment of high-risk pulmonary embolism with persistent hypotension and/or signs of shock is intravenous thrombolysis. However, if thrombolysis is contraindicated due to risk of serious bleeding, or if it yields insufficient effect, surgical thrombectomy or catheter-directed intervention (CDI) plus anticoagulation is recommended. The aim of this study was to assess the outcomes of the CDI modality introduced in a tertiary referral centre in 2013.

METHODS

Retrospective comparison between patients treated with CDI plus anticoagulation (n = 22) and patients treated with anticoagulation only (n = 23) as used before the CDI technique was available. The main outcomes of interest were 90-day survival and reduction of right to left ventricle diameter (RV/LV) ratio, using the Fischer's exact test and a mixed model, respectively, for statistical analysis.

RESULTS

Ninety-day survival was 59% after CDI and 61% after anticoagulation only; P = .903. The rate of RV/LV ratio reduction was 0.4 units higher per 24 hours in the CDI group (median 2.1 pre-treatment), than in the anticoagulation only group (median 1.3 pre-treatment); P = .007.

CONCLUSION

In patients with high-risk pulmonary embolism, 90-day survival was similar after treatment with CDI plus anticoagulation compared to anticoagulation only. The mean reduction in RV/LV ratio was larger in the CDI group. Our results support the use of CDI in selected patients, respecting the limitations and potential side effects of each technical device used.

Developing a scoring tool to estimate the risk of deterioration for normotensive patients with acute pulmonary embolism on admission

Background

It is important to identify deterioration in normotensive patients with acute pulmonary embolism (PE). This study aimed to develop a tool for predicting deterioration among normotensive patients with acute PE on admission.

Methods

Clinical, laboratory, and computed tomography parameters were retrospectively collected for normotensive patients with acute PE who were treated at a Chinese center from January 2011 to May 2020 on admission into the hospital. The endpoint of the deterioration was any adverse outcome within 30 days. Eligible patients were randomized 2:1 to derivation and validation cohorts, and a nomogram was developed and validated by the aforementioned cohorts, respectively. The areas under the curves (AUCs) with 95% confidence intervals (CIs) were calculated. A risk-scoring tool for predicting deterioration was applied as a web-based calculator.

Results

The 845 eligible patients (420 men, 425 women) had an average age of 60.05 ± 15.43 years. Adverse outcomes were identified for 81 patients (9.6%). The nomogram for adverse outcomes included heart rate, systolic pressure, N-terminal-pro brain natriuretic peptide, and ventricle/atrial diameter ratios at 4-chamber view, which provided AUC values of 0.925 in the derivation cohort (95% CI 0.900–0.946, p < 0.001) and 0.900 in the validation cohort (95% CI 0.883–0.948, p < 0.001). A risk-scoring tool was published as a web-based calculator (https://gaoyzcmu.shinyapps.io/APE9AD/).

Conclusions

We developed a web-based scoring tool that may help predict deterioration in normotensive patients with acute PE.