Assessment of flip angle-TR equivalence for standardized dissolved-phase imaging of the lung with hyperpolarized 129Xe MRI.

PURPOSE: To investigate the feasibility of describing the impact of any flip angle-TR combination on the resulting distribution of the hyperpolarized xenon-129 (HXe) dissolved-phase magnetization in the chest using a single virtual parameter, TR90°,equiv . METHODS: HXe MRI scans with simultaneous gas- (GP) and dissolved-phase (DP) excitation were performed using 2D projection scans in mechanically ventilated rabbits. Measurements with DP flip angles ranging from 6-90° and TRs ranging from 8.3-500 ms were conducted. DP maps based on acquisitions of similar radio frequency pulse-induced relaxation rates were compared. RESULTS: The observed distribution of the DP magnetization was strongly affected by acquisition flip angle and TR. However, for flip angles up to 60°, measurements with the same radio frequency pulse-induced relaxation rates, resulted in very similar DP images despite the presence of significant macroscopic gas transport processes. For flip angles approaching 90°, the downstream signal component decreased noticeably relative to acquisitions with lower flip angles. Nevertheless, the total DP signal continued to follow an empirically verified conversion equation over the entire investigated parameter range, which yields the equivalent TR of a hypothetical 90° measurement for any experimental flip angle-TR combination. CONCLUSION: We have introduced a method for converting the flip angle and TR of a given HXe DP measurement to a standardized metric based on the virtual quantity, TR90°,equiv , using their equivalent RF relaxation rates. This conversion permits the comparison of measurements obtained with different pulse sequence types or by different research groups using various acquisition parameters.

Central Veno-Arterial Extracorporeal Membrane Oxygenation (C-VA-ECMO) After Cardiothoracic Surgery: A Single-Center Experience.

OBJECTIVES: Central veno-arterial extracorporeal membrane oxygenation (C-VA-ECMO) provides temporary cardiorespiratory support for patients in heart failure who cannot be weaned from cardiopulmonary bypass successfully. Outcomes are influenced by the reversibility of the initial insult and complications of the technique. METHODS: The authors reviewed their single-center experience over the last 8 years to inform future practice. The study included all patients supported with C-VA-ECMO after cardiothoracic surgery between January 2008 and July 2016. The authors identified mortality risk factors using logistic regression analysis and chi-square tests. RESULTS: One hundred and one patients were supported with C-VA-ECMO during the studied period. Weaning from ECMO was successful in 57.4% of patients, whereas 7.9% were bridged to veno-venous ECMO, 2% to peripheral veno-arterial ECMO, and 2% to biventricular ventricular assist devices. In-hospital and 1-year survival for all patients was 33.7% and 27.7%, respectively. Survival was considerably higher in transplantation patients (n = 11), at 63.6% and 54.5%, respectively. Risk factors linked to in-hospital mortality were age older than 70 years, lactate level greater than 4 mmol/L after 48 hours, and hepatic and kidney failure during ECMO support. CONCLUSIONS: Overall one-third of patients in the cohort who the authors believe would otherwise have died from postcardiotomy cardiogenic shock survived because C-VA-ECMO was commenced after cardiac surgery. Survival is greater in transplantation patients necessitating this form of support during or immediately after surgery.

Predictors of in-hospital mortality and midterm outcomes of patients successfully weaned from venoarterial extracorporeal membrane oxygenation.

OBJECTIVES: There is limited evidence to guide the decision to proceed with weaning from venoarterial extracorporeal membrane oxygenation, and approximately 30% of patients weaned "successfully" do not survive to hospital discharge. We evaluated predictors of in-hospital mortality and midterm outcomes of patients successfully weaned from venoarterial extracorporeal membrane oxygenation after support for cardiogenic shock, surviving more than 24 hours after weaning, with the aim of improving patient selection for durable weaning. METHODS: We performed a retrospective analysis of 92 patients supported on venoarterial extracorporeal membrane oxygenation and successfully weaned between January 2013 and February 2018. Survival was estimated by the Kaplan-Meier method. Predictors of in-hospital mortality were identified using a Cox proportional hazards model and an Akaike information criterion-selected multivariate model. RESULTS: Overall survival at hospital discharge was 64.2%; survival was 54.6% 1 year after support and 51.4% 3 years after support. A history of diabetes, previous myocardial infarction, prolonged extracorporeal membrane oxygenation support, and hypoxemia at extracorporeal membrane oxygenation weaning were independent predictors of in-hospital mortality. At midterm follow-up, New York Heart Association class I heart function was observed in 53% of patients, class II in 19%, class III in 16%, and class IV in 12%. Average left ventricular ejection fraction was 46.5% ± 18.2%, and 50% of the patients had been readmitted to the hospital because of heart failure. CONCLUSIONS: Durable extracorporeal membrane oxygenation weaning with acceptable midterm functional status is obtainable in well-selected patients. Previous myocardial infarction, diabetes, prolonged extracorporeal membrane oxygenation support, and pulmonary dysfunction strongly predicted in-hospital mortality after venoarterial extracorporeal membrane oxygenation weaning. In this high-risk situation, other heart replacement therapies should be considered.

Increased Intracranial Hemorrhage Amid Elevated Inflammatory Markers in Those With COVID-19 Supported With Extracorporeal Membrane Oxygenation.

ABSTRACT: COVID-19-related coagulopathy is a known complication of SARS-CoV-2 infection and can lead to intracranial hemorrhage (ICH), one of the most feared complications of extracorporeal membrane oxygenation (ECMO). We sought to evaluate the incidence and etiology of ICH in patients with COVID-19 requiring ECMO. Patients at two academic medical centers with COVID-19 who required venovenous-ECMO support for acute respiratory distress syndrome (ARDS) were evaluated retrospectively. During the study period, 33 patients required ECMO support; 16 (48.5%) were discharged alive, 13 died (39.4%), and 4 (12.1%) had ongoing care. Eleven patients had ICH (33.3%). All ICH events occurred in patients who received intravenous anticoagulation. The ICH group had higher C-reactive protein (P = 0.04), procalcitonin levels (P = 0.02), and IL-6 levels (P = 0.05), lower blood pH before and after ECMO (P < 0.01), and higher activated partial thromboplastin times throughout the hospital stay (P < 0.0001). ICH-free survival was lower in COVID-19 patients than in patients on ECMO for ARDS caused by other viruses (49% vs. 79%, P = 0.02). In conclusion, patients with COVID-19 can be successfully bridged to recovery using ECMO but may suffer higher rates of ICH compared to those with other viral respiratory infections.

Mid-term outcomes with the use of extracorporeal membrane oxygenation for cardiopulmonary failure secondary to massive pulmonary embolism.

OBJECTIVES: There has been increasing interest in using extracorporeal membrane oxygenation (ECMO) to rescue patients with pulmonary embolism (PE) in the advanced stages of respiratory or haemodynamic decompensation. We examined mid-term outcomes and risk factors for in-hospital mortality. METHODS: We conducted a retrospective study of 36 patients who required ECMO placement (32 veno-arterial ECMO, 4 veno-venous) following acute PE. Survival curves were estimated using the Kaplan-Meier method. Risk factors for in-hospital mortality were assessed by logistic regression analysis. Functional status and quality of life were assessed by phone questionnaire. RESULTS: Overall survival to hospital discharge was 44.4% (16/36). Two-year survival conditional to discharge was 94% (15/16). Two-year survival after veno-arterial ECMO was 39% (13/32). In patients supported with veno-venous ECMO, survival to discharge was 50%, and both patients were alive at follow-up. In univariable analysis, a history of recent surgery (P = 0.064), low left ventricular ejection fraction (P = 0.029), right ventricular dysfunction ≥ moderate at weaning (P = 0.083), on-going cardiopulmonary resuscitation at ECMO placement (P = 0.053) and elevated lactate at weaning (P = 0.002) were risk factors for in-hospital mortality. In multivariable analysis, recent surgery (P = 0.018) and low left ventricular ejection fraction at weaning (P = 0.013) were independent factors associated with in-hospital mortality. At a median follow-up of 23 months, 10 patients responded to our phone survey; all had acceptable functional status and quality of life. CONCLUSIONS: Massive acute PE requiring ECMO support is associated with high early mortality, but patients surviving to hospital discharge have excellent mid-term outcomes with acceptable functional status and quality of life. ECMO can provide a stable platform to administer other intervention with the potential to improve outcomes. Risk factors for in-hospital mortality after PE and veno-arterial ECMO support were identified.

Stratification Risk Analysis in Bridging Patients to Lung Transplant on ECMO: The STABLE Risk Score.

BACKGROUND: No clinically validated tool exists to predict in-hospital mortality in patients requiring extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplantation. We generated a quantitative risk assessment tool for these patients. METHODS: Of 822 patients in the United Network for Organ Sharing (UNOS) database who required ECMO as bridge to lung transplant between 2004 and 2018, 630 were included in the analysis after exclusion for age <18 years, prior transplant, or treatment before 2004. Recipient-specific variables associated with posttransplant in-hospital mortality were incorporated into a multivariable logistic regression model in an automated stepwise fashion. Linear prediction was used to construct the Recipient Stratification Risk Analysis in Bridging Patients to Lung Transplant on ECMO (STABLE) score. K-fold cross-validation provided an unbiased estimate of out-of-sample performance. After further exclusion for University of Pennsylvania patients, the remaining cohort was used for external score validation. An iOS application was developed to aid clinical use. RESULTS: Six recipient-specific, pretransplant variables were translated into a 24-point score. STABLE scores in the United Network for Organ Sharing (UNOS) database ranged from 0 to 21, and each point increased the odds of in-hospital mortality by 22.0% (95% confidence interval, 1.14-1.29, P < .001). K-fold cross-validation yielded a receiver operating characteristic area under the curve of 86.2%. Validation of the STABLE score using our institutional database yielded an area under the curve of 89%. CONCLUSIONS: The STABLE score is a novel, internally cross-validated tool for risk stratification of patients on ECMO as a bridge to transplant. Its predictive power and accuracy may aid clinical decision-making and improve posttransplant outcomes.

Not All Septal Defects Are Equal: Outcomes of Bilateral Lung Transplant With Cardiac Defect Repair vs Combined Heart-Lung Transplant in Patients With Eisenmenger Syndrome in the United States.

BACKGROUND: Thoracic transplantation is considered for patients with Eisenmenger syndrome (ES) who have refractory right ventricular failure despite optimal therapy for pulmonary arterial hypertension. This study compared the outcomes of bilateral lung transplantation (BLT) with cardiac defect repair vs combined heart-lung transplantation (HLT). RESEARCH QUESTION: This study presents an updated analysis using a US national registry to evaluate the outcomes of patients diagnosed with ES who underwent HLT or BLT with repair of cardiac defects. STUDY DESIGN AND METHODS: This study identified patients with ES who underwent thoracic transplantation from 1987 to 2018 from the United Network for Organ Sharing database. Survival curves were estimated by using the Kaplan-Meier method and were compared by using the log-rank test. RESULTS: During the study period, 442 adults with ES underwent thoracic transplantation (316 HLTs and 126 BLTs). Following BLT, overall survival 1, 5, and 10 years' posttransplant was 63.1%, 38.5%, and 30.2%, respectively. Following HLT, overall survival 1, 5, and 10 years' posttransplant was 68.0%, 47.3%, and 30.5% (P = .6). When survival analysis was stratified according to type of defect, patients with an atrial septal defect had better survival following BLT than following HLT (88.3% vs 63.2% 1 year posttransplant, P < .01; 71.1% vs 49.8% 3 years' posttransplant, P < .01; and 37.4% vs 29.9% 10 years' posttransplant, P = .08). Patients with a ventricular septal defect (VSD) exhibited better survival following HLT than following BLT (78.2% vs 49.6% 1 year posttransplant, P < .01; 55.6% vs 34.3% 5 years' posttransplant, P < .01; and 35.7% vs 26.5% 10 years' posttransplant, P = .03). The most common cause of mortality in patients with VSD undergoing BLT was cardiac ventricular failure. INTERPRETATION: This study suggests that the best transplant option for patients with VSD remains HLT, which prevents subsequent development of ventricular failure. BLT with cardiac defect repair should be considered as the first-line treatment option in patients with ES due to an uncorrected atrial septal defect. These patients can be considered to have isolated and reversible right ventricular failure akin to patients with advanced pulmonary arterial hypertension.

Use veno-venous extra corporeal membrane oxygenation in elderly patients with post-cardiotomy hypoxia: the changing paradigm of respiratory support in adult respiratory distress syndrome.

BACKGROUND: Veno-venous extracorporeal membrane oxygenation (VV-ECMO) support for ARDS treatment after cardiac surgery has progressed remarkably in the last 20 years. However, one of the limitations of a successful recover is age, being a powerful predictor of mortality. CASE PRESENTATION: In this case report we discuss a 78-year-old man who underwent aortic valve and aortic root replacement. The postoperative period was complicated by ARDS following aspiration pneumonia treated with VV-ECMO weaned after 6 days. At two-year follow up, the patient made an excellent recover, being the second oldest person to survive VV-ECMO following cardiac surgery in the world. CONCLUSION: In the literature there is no consensus regarding a specific age limit and results, in the use of ECMO in the elderly are scarce and inconsistent. We do not think advanced age is a contraindication to the use of ECMO.

Measurement of Regional 2D Gas Transport Efficiency in Rabbit Lung Using Hyperpolarized 129Xe MRI.

While hyperpolarized xenon-129 (HXe) MRI offers a wide array of tools for assessing functional aspects of the lung, existing techniques provide only limited quantitative information about the impact of an observed pathology on overall lung function. By selectively destroying the alveolar HXe gas phase magnetization in a volume of interest and monitoring the subsequent decrease in the signal from xenon dissolved in the blood inside the left ventricle of the heart, it is possible to directly measure the contribution of that saturated lung volume to the gas transport capacity of the entire lung. In mechanically ventilated rabbits, we found that both xenon gas transport and transport efficiency exhibited a gravitation-induced anterior-to-posterior gradient that disappeared or reversed direction, respectively, when the animal was turned from supine to prone position. Further, posterior ventilation defects secondary to acute lung injury could be re-inflated by applying positive end expiratory pressure, although at the expense of decreased gas transport efficiency in the anterior volumes. These findings suggest that our technique might prove highly valuable for evaluating lung transplants and lung resections, and could improve our understanding of optimal mechanical ventilator settings in acute lung injury.

Multibreath Hyperpolarized 3He Imaging Scheme to Measure Alveolar Oxygen Tension and Apparent Diffusion Coefficient.

RATIONALE AND OBJECTIVES: In this study, we compared a newly developed multibreath simultaneous alveolar oxygen tension and apparent diffusion coefficient (PAO2-ADC) imaging sequence to a single-breath acquisition, with the aim of mitigating the compromising effects of intervoxel flow and slow-filling regions on single-breath measurements, especially in chronic obstructive pulmonary disease (COPD) subjects. MATERIALS AND METHODS: Both single-breath and multibreath simultaneous PAO2-ADC imaging schemes were performed on a total of 10 human subjects (five asymptomatic smokers and five COPD subjects). Estimated PAO2 and ADC values derived from the different sequences were compared both globally and regionally. The distribution of voxels with nonphysiological values was also compared between the two schemes. RESULTS: The multibreath protocol decreased the ventilation defect volumes by an average of 12.9 ± 6.6%. The multibreath sequence generated nonphysiological PAO2 values in 11.0 ± 8.5% fewer voxels than the single-breath sequence. Single-breath PAO2 maps also showed more regions with gas-flow artifacts and general signal heterogeneity. On average, the standard deviation of the PAO2 distribution was 16.5 ± 7.0% lower using multibreath PAO2-ADC imaging, suggesting a more homogeneous gas distribution. Both mean and standard deviation of the ADC increased significantly from single- to multibreath imaging (p = 0.048 and p = 0.070, respectively), suggesting more emphysematous regions in the slow-filling lung. CONCLUSION: Multibreath PAO2-ADC imaging provides superior accuracy and efficiency compared to previous imaging protocols. PAO2 and ADC maps generated by multibreath imaging allowed for the qualification of various regions as emphysematous or obstructed, which single-breath PAO2 maps can only identify as defects. The simultaneous PAO2 and ADC measurements generated by the presented multibreath method were also more physiologically realistic, and allowed for more detailed analysis of the slow-filling regions characteristic of COPD subjects.

ICD lead extraction: Not a benign procedure. External chest compression: Not a benign manoeuvre.

This is the case of a 45-year-old man who was electively admitted to our hospital for revision and extraction of his faulty implantable cardioverter-defibrillator lead and box. The procedure was complicated by cardiac tamponade requiring pericardiocentisis (unsuccessful) and cardiopulmonary resuscitation. The patient was then rushed to theatre for emergency sternotomy and institution of cardiopulmonary bypass. A tear in the superior vena cava was identified and repaired. Unfortunately, the patient suffered of a liver laceration, due to chest compression, which required emergency laparotomy. The aim of this report is to highlight the combination and management of two rare life-threatening complications that occurred in a single case.