Human immunodeficiency virus infection is associated with greater risk of pneumonia and readmission after cardiac surgery

Objective

Human immunodeficiency virus infection (HIV+) is associated with a 2-fold increased risk of cardiovascular disease. Increasingly, patients who are HIV + are being evaluated to undergo cardiac surgery. Current risk-adjusted scoring systems, including the Society of Thoracic Surgeons Predicted Risk of Mortality score, fail to stratify HIV + risk. Unfortunately, there exists a paucity of cardiac surgery outcomes data in modern patients who are HIV+.

Methods

We conducted a retrospective review of PearlDiver, an all-payer claims administrative database. In total, 14,714,743 patients were captured between 2010 and 2020. Of these, 59,695 (0.4%) of patients had a history of HIV+, and 1759 (2.95%) of these patients underwent cardiac surgery. Patients who were HIV+ were younger, more often male, and had greater comorbidity, history of hypertension, chronic obstructive pulmonary disease, chronic liver disease, chronic kidney disease, chronic lung disease, and heart failure.

Results

Postoperatively, patients who were HIV + had significantly greater rates of pneumonia (relative risk, 1.70; P = .0003) and 30-day all-cause readmission (relative risk, 1.28, P < .0001). After linear regression analysis, these results remained significant. Data also show that a lesser proportion of patients with HIV + underwent coronary artery bypass grafting, aortic valve replacement, and any cardiac surgery compared with controls.

Conclusions

Patients who are HIV + undergoing cardiac surgery are at greater risk of pneumonia and readmission. Moreover, we discovered lower rates of cardiac surgery in patients who are HIV+, which may reflect limited access to surgery when indicated. Today's risk-adjusted scoring systems in cardiac surgery need to better account for the modern patient who is HIV+.

Ambulatory 7-day mechanical circulatory support in sheep model of pulmonary hypertension and right heart failure

BACKGROUND

Right heart failure is the major cause of death in pulmonary hypertension. Lung transplantation is the only long-term treatment option for patients who fail medical therapy. Due to the scarcity of donor lungs, there is a critical need to develop durable mechanical support for the failing right heart. A major design goal for durable support is to reduce the size and complexity of devices to facilitate ambulation. Toward this end, we sought to deploy wearable mechanical support technology in a sheep disease model of chronic right heart failure.

METHODS

In 6 sheep with chronic right heart failure, a mechanical support system consisting of an extracorporeal blood pump coupled with a gas exchange unit was attached in a right atrium-to-left atrium configuration for up to 7 days. Circuit performance, hematologic parameters, and animal hemodynamics were analyzed.

RESULTS

Six subjects underwent the chronic disease model for 56 to 71 days. Three of the subjects survived to the 7-day end-point for circulatory support. The circuit provided 2.8 (0.5) liter/min of flow compared to the native pulmonary blood flow of 3.5 (1.1) liter/min. The animals maintained physiologically balanced blood gas profile with a sweep flow of 1.2 (1.0) liter/min. Two animals freely ambulated while wearing the circuit.

CONCLUSIONS

Our novel mechanical support system provided physiologic support for a large animal model of pulmonary hypertension with right heart failure. The small footprint of the circuit and the low sweep requirement demonstrate the feasibility of this technology to enable mobile ambulatory applications.

A Dynamic Sheep Model to Induce Pulmonary Hypertension and Right Ventricular Failure

Decompensated right ventricular failure (RVF) in pulmonary hypertension (PH) is fatal, with limited medical treatment options. Developing and testing novel therapeutics for PH requires a clinically relevant large animal model of increased pulmonary vascular resistance and RVF. This manuscript describes the method to induce an ovine PH-RVF model that utilizes left pulmonary artery (LPA) ligation, progressive main pulmonary artery (MPA) banding, and insertion of an RV pressure line for monitoring. The PA cuff and RV pressure tubing are connected to subcutaneous access ports. This model of PH-RVF is a versatile platform to control not only the disease severity, but also the RV's phenotypic response. Subjects undergo progressive PA band adjustments twice per week for approximately 9 weeks with sequential measures of RV pressure, PA cuff pressures, and mixed venous blood gas (SvO2). Subjects can further be exercised on a livestock treadmill while hemodynamic parameters are captured. At the initiation and endpoint of this model, ventricular function and dimensions are assessed using echocardiography. In this model, RV mean and systolic pressure increased to 28 ± 5 and 57 ± 7 mmHg at week 1, and further to 44 ± 7 and 93 ± 18 mmHg by week 9, respectively. Echocardiography demonstrates characteristic findings of PH-RVF, notably RV dilation, increased wall thickness, and septal bowing. The rate of PA banding has a significant impact on SvO2 and thus the model can be titrated to elicit varying RV phenotypes. When the PA cuff is tightened rapidly, it can lead to a precipitous decline in SvO2, leading to RV decompensation, whereas a slower, more paced strategy leads to an adaptive RV stress-load response that maintains physiologic SvO2. A faster rate of PA banding will also lead to more severe liver fibrosis. The addition of controlled exercise provides a useful platform for assessing the effects of physical exertion in a PH-RVF model. This chronic PH-RVF model provides a valuable tool for studying molecular mechanisms, developing diagnostic biomarkers, and evaluating mechanical circulatory support systems.

Xenogeneic cross-circulation for physiological support and recovery of ex vivo human livers

BACKGROUND AND AIMS

The scarcity of suitable donor livers highlights a continuing need for innovation to recover organs with reversible injuries in liver transplantation.

APPROACH AND RESULTS

Explanted human donor livers (n = 5) declined for transplantation were supported using xenogeneic cross-circulation of whole blood between livers and xeno-support swine. Livers and swine were assessed over 24 hours of xeno-support. Livers maintained normal global appearance, uniform perfusion, and preservation of histologic and subcellular architecture. Oxygen consumption increased by 75% ( p = 0.16). Lactate clearance increased from -0.4 ± 15.5% to 31.4 ± 19.0% ( p = 0.02). Blinded histopathologic assessment demonstrated improved injury scores at 24 hours compared with 12 hours. Vascular integrity and vasoconstrictive function were preserved. Bile volume and cholangiocellular viability markers improved for all livers. Biliary structural integrity was maintained.

CONCLUSIONS

Xenogeneic cross-circulation provided multisystem physiological regulation of ex vivo human livers that enabled functional rehabilitation, histopathologic recovery, and improvement of viability markers. We envision xenogeneic cross-circulation as a complementary technique to other organ-preservation technologies in the recovery of marginal donor livers or as a research tool in the development of advanced bioengineering and pharmacologic strategies for organ recovery and rehabilitation.

Immune characterization of a xenogeneic human lung cross-circulation support system

Improved approaches to expanding the pool of donor lungs suitable for transplantation are critically needed for the growing population with end-stage lung disease. Cross-circulation (XC) of whole blood between swine and explanted human lungs has previously been reported to enable the extracorporeal recovery of donor lungs that declined for transplantation due to acute, reversible injuries. However, immunologic interactions of this xenogeneic platform have not been characterized, thus limiting potential translational applications. Using flow cytometry and immunohistochemistry, we demonstrate that porcine immune cell and immunoglobulin infiltration occurs in this xenogeneic XC system, in the context of calcineurin-based immunosuppression and complement depletion. Despite this, xenogeneic XC supported the viability, tissue integrity, and physiologic improvement of human donor lungs over 24 hours of xeno-support. These findings provide targets for future immunomodulatory strategies to minimize immunologic interactions on this organ support biotechnology.

Large animal preclinical investigation into the optimal extracorporeal life support configuration for pulmonary hypertension and right ventricular failure

INTRODUCTION

Right ventricular failure (RVF) is a major cause of mortality in pulmonary hypertension (PH). Mechanical circulatory support holds promise for patients with medically refractory PH, but there are no clinical devices for long-term right ventricular (RV) support. Investigations into optimal device parameters and circuit configurations for PH-induced RVF (PH-RVF) are needed.

METHODS

Eleven sheep underwent previously published chronic PH model. We then evaluated a low-profile, ventricular assist device (VAD)-quality pump combined with a novel low-resistance membrane oxygenator (Pulmonary Assist Device, PAD) under one of four central cannulation strategies: right atrium-to-left atrium (RA-LA, N = 3), RA-to-pulmonary artery (RA-PA, N=3), pumpless pulmonary artery-to-left atrium (PA-LA, N = 2), and RA-to-ascending aorta (RA-Ao, N = 3). Acute-on-chronic RVF (AoC RVF) was induced, and mechanical support was provided for up to 6 hours at blood flow rates of 1 to 3 liter/min. Circuit parameters, physiologic, hemodynamic, and echocardiography data were collected.

RESULTS

The RA-LA configuration achieved blood flow of 3 liter/min. Meanwhile, RA-PA and RA-Ao faced challenges maintaining 3 liter/min of flow due to higher circuit afterload. Pumpless PA-LA was flow-limited due to anatomical limitations inherent to this animal model. RA-LA and RA-Ao demonstrated serial RV unloading with increasing circuit flow, while RA-PA did not. RA-LA also improved left ventricular (LV) and septal geometry by echocardiographic assessment and had the lowest inotropic dependence.

CONCLUSION

RA-LA and RA-Ao configurations unload the RV, while RA-LA also lowers pump speed and inotropic requirements, and improves LV mechanics. RA-PA provide inferior support for PH-RVF, while an alternate animal model is needed to evaluate PA-LA.

"Keep Your Move in the Tube" safely increases discharge home following cardiac surgery

BACKGROUND

Restrictive sternal precautions intended to prevent cardiac surgery patients from damaging healing sternotomies lack supporting evidence and may decrease independence and increase postacute care utilization. Data regarding the impact of alternative approaches on safety and outcomes are needed to guide evidence-based best practices.

OBJECTIVE

To examine whether an approach allowing greater freedom during activities of daily living than permitted under commonly used restrictive sternal precautions can safely decrease postacute care utilization.

DESIGN

Before-and-after study, using propensity score adjustment to account for differences in patient clinical and demographic characteristics, surgery type, and surgeon.

SETTING

600-bed acute care hospital.

INTERVENTION

Beginning March 2016, the acute care hospital replaced traditional weight- and time-based precautions given to patients who underwent median sternotomy with the "Keep Your Move in the Tube" (KMIT) approach for mindfully performing movements involved in the activities of daily living, guided by pain.

MAIN OUTCOME MEASURES

The study compared sternal wound complications, discharge disposition, 30-day readmission, and functional status between consecutive cardiac surgery patients with "independent" or "modified independent" preoperative functional status who underwent median sternotomy in the 1.5 years before (n = 627, standard precautions group) and after (n = 477, KMIT group) KMIT implementation.

RESULTS

The odds of discharge to home, versus to inpatient rehabilitation or skilled nursing facility, were ~3 times higher for KMIT than standard precautions patients (risk-adjusted odds ratio [rOR], 95% confidence interval [CI] = 2.90, 1.95-4.32, and 3.03, 1.57-5.86, respectively). KMIT patients also had significantly higher odds of demonstrating "independent" or "modified independent" functional status on final inpatient physical therapy treatment for bed mobility (rOR, 95% CI = 7.51, 5.48-10.30) and transfers (rOR, 95% CI = 3.40, 2.62-4.42). No significant difference was observed in sternal wound complications (in-hospital or causing readmission) (rOR, 95% CI = 1.27, 0.52-3.09) or all-cause 30-day readmissions (rOR, 95% CI = 0.55, 0.23-1.33).

CONCLUSIONS

KMIT increases discharge-to-home for cardiac surgery patients without increasing risk for adverse events and reducing utilization of expensive institutional postacute care.

Aortic Valve Replacement without Annular Enlargement in Patients with Small Aortic Roots

Use of small prostheses for aortic valve replacement eliminates the need for annular enlargement but may impair symptomatic resolution and long-term patient survival. We reviewed our experience with 105 consecutive patients who had isolated aortic valve replacement with small mechanical prostheses or bioprostheses (14 to 21 mm) without concurrent annular enlargement between August 1976 and November 1992. The mean age was 72 ± 10 years and 82% of patients were female. Valvular disease was primarily aortic stenosis in 61%, aortic regurgitation in 7%, and mixed aortic disease was present in 32% of patients. Mean preoperative ejection fraction was 64% ± 17% and the aortic valve area was 0.5 ± 0.2 cm2. Prior to surgery, 82% of patients were in New York Heart Association functional class III or IV. The mean duration of follow-up was 8.1 years. There were 7 early and 14 late deaths giving an overall survival of 80% and a 10-year Kaplan-Meier survival rate of 77%. Five patients developed thromboembolic complications (transient stroke) and 2 required repeat aortic valve replacement due to prosthetic valve endocarditis. Doppler echocardiography or cardiac catheterization was performed in 15 patients postoperatively but peak systolic gradient exceeded 50 mm Hg in only one individual with a 21-mm porcine valve. All surviving patients were in functional class I or II. We conclude that aortic valve replacement with small prostheses is associated with excellent long-term patient survival, improvement in clinical symptoms, and a low incidence of complications.

Using value-based analysis to influence outcomes in complex surgical systems

BACKGROUND

Value-based analysis (VBA) is a management strategy used to determine changes in value (quality/cost) when a usual practice (UP) is replaced by a best practice (BP). Previously validated in clinical initiatives, its usefulness in complex systems is unknown. To answer this question, we used VBA to correct deficiencies in cardiac surgery at Memorial Healthcare System.

STUDY DESIGN

Cardiac surgery is a complex surgical system that lends itself to VBA because outcomes metrics provided by the Society of Thoracic Surgeons provide an estimate of quality; cost is available from Centers for Medicare and Medicaid Services and other contemporary sources; the UP can be determined; and the best practice can be established.

RESULTS

Analysis of the UP at Memorial Healthcare System revealed considerable deficiencies in selection of patients for surgery; the surgery itself, including choice of procedure and outcomes; after care; follow-up; and control of expenditures. To correct these deficiencies, each UP was replaced with a BP. Changes included replacement of most of the cardiac surgeons; conversion to an employed physician model; restructuring of a heart surgery unit; recruitment of cardiac anesthesiologists; introduction of an interactive educational program; eliminating unsafe practices; and reducing cost.

CONCLUSIONS

There was a significant (p < 0.01) reduction in readmissions, complications, and mortality between 2009 and 2013. Memorial Healthcare System was only 1 of 17 (1.7%) database participants (n = 1,009) to achieve a Society of Thoracic Surgeons 3-star rating in all 3 measured categories. Despite substantial improvements in quality, the cost per case and the length of stay declined. These changes created a savings opportunity of $14 million, with actual savings of $10.4 million. These findings suggest that VBA can be a powerful tool to enhance value (quality/cost) in a complex surgical system.

Superior vena cava syndrome secondary to thyroid cancer

It is uncommon for thyroid cancer to present with superior vena cava syndrome. Obstruction of superior vena cava can develop as a result of intrinsic and extrinsic spread of the thyroid cancer. The usual presentation of this disease entity is a neck mass with symptoms and signs suggestive of superior vena cava obstruction. Superior vena cava obstruction is commonly caused by lung cancer and lymphoma. However, thyroid cancer can cause superior vena cava obstruction by downward tumour spread into the mediastinum causing extrinsic compression, which will lead to narrowing and thrombosis of the major venous system in the chest. Paraganglioma can also present with superior vena cava obstruction and it mimics thyroid cancer microscopically. Proper staining should be performed to differentiate between the two diseases. This could be the first case of this kind reported in the literature.

Correction of anomalous systemic venous drainage: transposition of left SVC to left PA

In some patients, a persistent left superior vena cava drains into the left atrium (rather than the right) and may produce a symptomatic right-to-left shunt. We describe an extracardiac approach for correcting anomalous systemic venous drainage when the innominate vein is absent. In this technique, the left superior vena cava is transposed to the left pulmonary artery.

Subintimal hematoma of the aorta after deceleration injury

Deceleration injuries of the aorta may occur without aortic disruption. We describe the case of a patient with a subintimal hematoma of the aorta that resolved within 48 hours. Serial arteriography confirmed the diagnosis and excluded aortic rupture. Thoracic exploration was not performed.