Hemocompatibility and biophysical interface of left ventricular assist devices and total artificial hearts

ABSTRACT

Over the past 2 decades, there has been a significant increase in the utilization of long-term mechanical circulatory support (MCS) for the treatment of cardiac failure. Left ventricular assist devices (LVADs) and total artificial hearts (TAHs) have been developed in parallel to serve as bridge-to-transplant and destination therapy solutions. Despite the distinct hemodynamic characteristics introduced by LVADs and TAHs, a comparative evaluation of these devices regarding potential complications in supported patients, has not been undertaken. Such a study could provide valuable insights into the complications associated with these devices. Although MCS has shown substantial clinical benefits, significant complications related to hemocompatibility persist, including thrombosis, recurrent bleeding, and cerebrovascular accidents. This review focuses on the current understanding of hemostasis, specifically thrombotic and bleeding complications, and explores the influence of different shear stress regimens in long-term MCS. Furthermore, the role of endothelial cells in protecting against hemocompatibility-related complications of MCS is discussed. We also compared the diverse mechanisms contributing to the occurrence of hemocompatibility-related complications in currently used LVADs and TAHs. By applying the existing knowledge, we present, for the first time, a comprehensive comparison between long-term MCS options.

Coronary flow capacity and survival prediction after revascularization: physiological basis and clinical implications

BACKGROUND AND AIMS

Coronary flow capacity (CFC) is associated with an observed 10-year survival probability for individual patients before and after actual revascularization for comparison to virtual hypothetical ideal complete revascularization.

METHODS

Stress myocardial perfusion (mL/min/g) and coronary flow reserve (CFR) per pixel were quantified in 6979 coronary artery disease (CAD) subjects using Rb-82 positron emission tomography (PET) for CFC maps of artery-specific size-severity abnormalities expressed as percent left ventricle with prospective follow-up to define survival probability per-decade as fraction of 1.0.

RESULTS

Severely reduced CFC in 6979 subjects predicted low survival probability that improved by 42% after revascularization compared with no revascularization for comparable severity (P = .0015). For 283 pre-and-post-procedure PET pairs, severely reduced regional CFC-associated survival probability improved heterogeneously after revascularization (P < .001), more so after bypass surgery than percutaneous coronary interventions (P < .001) but normalized in only 5.7%; non-severe baseline CFC or survival probability did not improve compared with severe CFC (P = .00001). Observed CFC-associated survival probability after actual revascularization was lower than virtual ideal hypothetical complete post-revascularization survival probability due to residual CAD or failed revascularization (P < .001) unrelated to gender or microvascular dysfunction. Severely reduced CFC in 2552 post-revascularization subjects associated with low survival probability also improved after repeat revascularization compared with no repeat procedures (P = .025).

CONCLUSIONS

Severely reduced CFC and associated observed survival probability improved after first and repeat revascularization compared with no revascularization for comparable CFC severity. Non-severe CFC showed no benefit. Discordance between observed actual and virtual hypothetical post-revascularization survival probability revealed residual CAD or failed revascularization.

STAR procedure becomes SAFER: First-in-man case series of a new antegrade dissection re-entry technique

INTRODUCTION

Antegrade dissection and re-entry (ADR) is an integral part of the hybrid algorithm, which has allowed for improved outcomes in chronic total occlusion (CTO) coronary intervention (PCI).

METHODS

A new ADR method, Subintimal Antegrade FEnestration and Re-entry (SAFER), is described. The results of a first-in-man series are presented.

RESULTS

SAFER was performed on seven consecutive patients with angiographic and clinical success in all patients.

CONCLUSIONS

This first-in-man study has shown that the SAFER technique is feasible and effective with the possibility of improving the antegrade PCI CTO success rate.

The use of veno-arterial extracorporeal membrane oxygenation in the octogenarian population: A single-center experience

INTRODUCTION

Advanced age is a known risk factor for poor outcomes after veno-arterial extracorporeal membrane oxygenation (V-A ECMO) for cardiac support. The use of ECMO support in patients over the age of 80 is controversial, and sometimes its use is contraindicated. We aimed to assess the use of ECMO in octogenarian patients to determine survival and complication rates.

METHODS

A single-center, retrospective analysis was completed at a large, urban academic medical center. Patients requiring V-A ECMO support between December of 2012 and November of 2019 were included as long as the patient was at least 80 years of age at the time of cannulation. Post cardiotomy shock patients were excluded.

RESULTS

A total of 46 patients met eligibility criteria; all received V-A ECMO support. Overall, the majority of patients (71.7%; 33/46) survived to decannulation, and 43.5% (20/46) survived to discharge. Patients who were previously rescued from percutaneous interventions tend to have a better survival than other patients (p = .06). The most common complications were renal and hemorrhagic.

CONCLUSIONS

We demonstrated that advanced age alone should not disqualify patients from cannulating and supporting with V-A ECMO.

Use of Percutaneous Left Ventricular Assist Device Before Durable Device Implantation in Patients With Cardiac Cachexia: Case Series

Frailty and malnutrition in patients with heart failure are barriers to durable left ventricular assist device (D-LVAD) support and heart transplantation. Moreover, cachexia in patients with advanced heart failure carries a high mortality risk. There are no guidelines for these patients other than increased caloric intake and rehabilitation. Patients suffering from cardiac cachexia and heart failure may benefit from temporary, percutaneous assist device support to improve the underlying heart disease and reverse the catabolic state. We retrospectively reviewed patients from January 2017 to January 2022. All patients who received Impella support (5.0 or 5.5, Abiomed) before D-LVAD implantation were screened. Those who met the criteria for cardiac cachexia were included. Patient demographics, nutritional and biochemical markers, and survival data were collected. A total of 14 patients were included. The majority of patients were male (85.7%) with ischemic cardiomyopathy (64.3%). Caloric intake, physical strength, and ambulation improved. Prealbumin levels improved from a median of 13.7-18.0 mg/dl ( p < 0.006) while on Impella 5.0 or 5.5 support. All patients survived to discharge and the 6 month follow-up. In conclusion, use of the Impella device improves cardiogenic shock symptoms and, consequently, may improve cachexia status prior to D-LVAD implantation.

Does the Type of Chronic Heart Failure Impact In-Hospital Outcomes for Aortic Valve Replacement Procedures?

BACKGROUND

This study assessed in-hospital outcomes of patients with chronic systolic, diastolic, or mixed heart failure (HF) undergoing transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (SAVR).

METHODS

The Nationwide Inpatient Sample database was used to identify patients with aortic stenosis and chronic HF who underwent TAVR or SAVR between 2012 and 2015. Propensity score matching and multivariate logistic regression were used to determine outcome risk.

RESULTS

A cohort of 9,879 patients with systolic (27.2%), diastolic (52.2%), and mixed (20.6%) chronic HF were included. No statistically significant differences in hospital mortality were noted. Overall, patients with diastolic HF had the shortest hospital stays and lowest costs. Compared with patients with diastolic HF, the risk of acute myocardial infarction (TAVR odds ratio [OR], 1.95; 95% CI, 1.20-3.19; P = .008; SAVR OR, 1.38; 95% CI, 0.98-1.95; P = .067) and cardiogenic shock (TAVR OR, 2.15; 95% CI, 1.43-3.23; P < .001; SAVR OR, 1.89; 95% CI, 1.42-2.53; P ≤ .001) was higher in patients with systolic HF, whereas the risk of permanent pacemaker implantation (TAVR OR, 0.58; 95% CI, 0.45-0.76; P < .001; SAVR OR, 0.58; 95% CI, 0.40-0.84; P = .004) was lower following aortic valve procedures. In TAVR, the risk of acute deep vein thrombosis and kidney injury was higher, although not statistically significant, in patients with systolic HF than in those with diastolic HF.

CONCLUSION

These outcomes suggest that chronic HF types do not incur statistically significant hospital mortality risk in patients undergoing TAVR or SAVR.

Surgically Implanted Impella Device for Patients on Impella CP Support Experiencing Refractory Hemolysis

The Impella CP (Abiomed Inc., Danvers, MA) is widely used in cardiac catheterization laboratories for patients presenting with cardiogenic shock, but it is also known to cause significant hemolysis. The risk of hemolysis can be reduced by properly positioning the device, ensuring an adequate volume status, and using full anticoagulation strategies; however, in some cases hemolysis persists. We present a case series of eight patients that were diagnosed with cardiogenic shock, underwent Impella CP placement, and then suffered from refractory hemolysis which was treated by upgrading the Impella device to the 5.0 or 5.5 version. Fifty percent (4/8) of the patients in this series were already receiving continuous renal replacement therapy, and the levels of plasma free hemoglobin (pFHb) and lactate dehydrogenase continued to increase after the implantation of the Impella CP. The median time between Impella CP placement and the diagnosis of refractory hemolysis was 16.5 hours (interquartile range [IQR], 8.0-26.0). The median time between the diagnosis of hemolysis to Impella upgrade was 6.0 hours (IQR, 4.0-7.0). A total of 87.5% (7/8) of patients experienced a drop in pFHb to below 40 mg/dl at 72 hours post-Impella upgrade, and they were discharged without any further need of dialysis. One patient expired due to irreversible multiple organ failure. We propose that early identification of hemolysis by close monitoring of pFHb and upgrading to the Impella 5.5 reduces hemolysis, prevents further kidney damage, and significantly improves clinical outcomes.

Use of the SAPIEN 3 Transcatheter Heart Valve in High-Risk Scenarios

The transcatheter aortic valve replacement procedure is used in patients with aortic stenosis. Transcatheter aortic valve replacement devices are quite versatile; thus, they are increasingly being used for nonaortic applications, such as tricuspid valve-in-valve implantation. This case series describes a transcatheter aortic valve replacement procedure in 4 patients with anatomic challenges (eg, aortic tortuosity, high valvular calcium burden, highly calcified bicuspid valve, low coronary artery takeoff, left main coronary artery occlusion, and large aortic annulus) and a fifth patient who had a failed tricuspid bioprosthesis and underwent a tricuspid valve-in-valve implantation with the Edwards SAPIEN 3 transcatheter heart valve (Edwards Lifesciences). All procedures required adjustments to the standard protocol, and each procedure was successful. The critical, technical adjustments in the deployment technique and preprocedural planning of the procedures are detailed to provide a road map for other cardiologists who encounter similar challenges.

Hyperadhesive von Willebrand Factor Promotes Extracellular Vesicle-Induced Angiogenesis: Implication for LVAD-Induced Bleeding

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VWF in patients on LVAD supports was hyperadhesive, activated platelets, and generated platelet-derived extracellular vesicles.

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Extracellular vesicles from LVAD patients and those from shear-activated platelets promoted aberrant angiogenesis in a VWF-dependent manner.

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The activated VWF exposed the A1 domain through the synergistic actions of oxidative stress and HSS generated in LVAD-driven circulation.

Bleeding associated with left ventricular assist device (LVAD) implantation has been attributed to the loss of large von Willebrand factor (VWF) multimers to excessive cleavage by ADAMTS-13, but this mechanism is not fully supported by the current evidence. We analyzed VWF reactivity in longitudinal samples from LVAD patients and studied normal VWF and platelets exposed to high shear stress to show that VWF became hyperadhesive in LVAD patients to induce platelet microvesiculation. Platelet microvesicles activated endothelial cells, induced vascular permeability, and promoted angiogenesis in a VWF-dependent manner. Our findings suggest that LVAD-driven high shear stress primarily activates VWF, rather than inducing cleavage in the majority of patients.

Percutaneous Thrombus Removal in COVID-19-Infected Patient with Pulmonary Embolism

We present a case describing the use of the AngioVac system (AngioDynamics, Inc.) and SENTINEL™ cerebral protection system (SCPS; Boston Scientific) in a patient with COVID-19 who initially presented with a large deep-vein thrombosis of the left lower extremity, complicated by a pulmonary embolism. Although he initially improved with systemic alteplase, he later developed a second large clot diagnosed in transit in the right atrium. Within 12 hours from initial thrombolysis, this large clot wedged across an incidental patent foramen ovale (PFO), the atrial septum, and the cavotricuspid annulus. We emergently performed a percutaneous clot extraction with preemptive placement of the SCPS in anticipation of cardioembolic phenomenon. A large (> 10 cm) clot was extracted without complication, and the patient was discharged home.

The combined use of SCPS and AngioVac in this case suggests a potential role for percutaneous treatment of severe and consequential thromboembolic disease, especially in patients with a PFO, and may be considered as an alternative and less-invasive option in patients with COVID-19. While cerebral embolic protection devices are approved for and widely used in transcatheter aortic valve replacement procedures, there is a theoretical benefit for use in percutaneous thrombolectomies as well.

Traumatic respiratory failure and veno-venous extracorporeal membrane oxygenation support

BACKGROUND

Respiratory failure (RF) is a common cause of death and morbid complication in trauma patients. Extracorporeal membrane oxygenation (ECMO) is increasingly used in adults with RF refractory to invasive mechanical ventilation. However, use of ECMO remains limited for this patient population as they often have contraindications for anticoagulation.

STUDY DESIGN

Medical records were retroactively searched for all adult patients who were admitted to the trauma service and received veno-venous ECMO (VV ECMO) support between June 2015 and August 2018. Survival to discharge and ECMO-related complications were collected and analyzed.

RESULTS

Fifteen patients from a large Level I trauma center met the criteria. The median PaO₂/FiO₂ ratio was 53.0 (IQR, 27.0-76.0), median injury severity score was 34.0 (IQR, 27.0-43.0), and the median duration of ECMO support was 11 days (IQR, 7.5-20.0). For this cohort, the survival-to-discharge rate was 87% (13/15). The incidence of neurologic complications was 13%, and deep vein thrombosis was reported in two cases (13%).

CONCLUSIONS

Survival rates of trauma patients in this study are equivalent to, or may exceed, those of non-trauma patients who receive ECMO support for other types of RF. With the employment of a multidisciplinary team assessment and proper patient selection, early cannulation, traumatic RF may be safely supported with VV ECMO in experienced centers.

Regional, Artery-Specific Thresholds of Quantitative Myocardial Perfusion by PET Associated with Reduced Myocardial Infarction and Death After Revascularization in Stable Coronary Artery Disease

Because randomized coronary revascularization trials in stable coronary artery disease (CAD) have shown no reduced myocardial infarction (MI) or mortality, the threshold of quantitative myocardial perfusion severity was analyzed for association with reduced death, MI, or stroke after revascularization within 90 d after PET. Methods: In a prospective long-term cohort of stable CAD, regional, artery-specific, quantitative myocardial perfusion by PET, coronary revascularization within 90 d after PET, and all-cause death, MI, and stroke (DMS) at 9-y follow-up (mean ± SD, 3.0 ± 2.3 y) were analyzed by multivariate Cox regression models and propensity analysis. Results: For 3,774 sequential rest–stress PET scans, regional, artery-specific, severely reduced coronary flow capacity (CFC) (coronary flow reserve ≤ 1.27 and stress perfusion ≤ 0.83 cc/min/g) associated with 60% increased hazard ratio for major adverse cardiovascular events and 30% increased hazard of DMS that was significantly reduced by 54% associated with revascularization within 90 d after PET (P = 0.0369), compared with moderate or mild CFC, coronary flow reserve, other PET metrics or medical treatment alone. Depending on severity threshold for statistical certainty, up to 19% of this clinical cohort had CFC severity associated with reduced DMS after revascularization. Conclusion: CFC by PET provides objective, regional, artery-specific, size–severity physiologic quantification of CAD severity associated with high risk of DMS that is significantly reduced after revascularization within 90 d after PET, an association not seen for moderate to mild perfusion abnormalities or medical treatment alone.

Transcatheter Mitral Valve Replacement with the Edwards Sapien 3 Valve

We describe the case of a 57-year-old man who had severe mitral valve stenosis and regurgitation without significant annular calcification. He was not a candidate for surgical valve replacement or repair because of his substantial comorbid conditions, overall frailty, and elevated surgical risk. He underwent successful transcatheter mitral valve replacement of his native mitral valve with compassionate, off-label use of an Edwards Sapien 3 valve. A search of the literature produced no other cases like ours, which represents a further evolution of the transcatheter valve implantation concept. Further studies are needed to help define accurate valve sizing, intraprocedural positioning, and long-term device stability, as well as to determine which patients might benefit from this commercially available valve. In the meantime, our findings could present a means of treating patients who have no other options.

Transcatheter aortic valve implantation with a Sapien 3 Commander 20 mm valves in patients with degenerated 19 mm bioprosthetic aortic valve

INTRODUCTION

Transcatheter aortic valve implantation (TAVI) in patients with degenerated bioprosthetic aortic valve has been successfully performed as an alternative to surgery. We describe our initial experience of valve-in-valve TAVI in five patients, using new generation Edwards Sapien 3 transcatheter heart valves implanted into degenerated 19 mm bioprosthetic valves. 20-mm Edwards S3 valves were offered for compassionate use. All patients had significant aortic valve stenosis.

METHODS AND RESULTS

The main vascular access was achieved and pre-closed with two Proglide closure devices in one patient and Prostar closure devices in four patients. For each TAVI procedure an Edwards 14 French sheath was inserted without complication and sutured in place. The Sapien 3 Commander delivery system was inserted and the valve was aligned in the descending aorta. The 20-mm Sapien 3 valve was deployed with slow continuous inflation during rapid right ventricular pacing. The cranial edge of the Edwards S3 valve was aligned with the cranial radiopaque markers of bioprosthesis to minimize paravalvular leak. Post-deployment angiography, transesophageal echocardiography and aortogram confirmed absence of mild aortic insufficiency and no increase in trans-aortic gradient when compared to a naïve 19 mm bioprosthetic valve.

CONCLUSION

Valve-in-valve TAVI with the Edwards S3 transcatheter heart valve for degenerative bioprosthetic aortic valves is technically feasible. The proper position of the stented valve minimizes the risk for post-procedure paravalvular insufficiency and provides good transaortic pressure gradient. © 2016 Wiley Periodicals, Inc.

Transcatheter Tricuspid Valve-in-Valve Replacement with an Edwards Sapien 3 Valve

A few case reports and case series have documented the outcomes in patients with tricuspid bioprosthetic valvular degeneration who underwent transcatheter implantation of the Medtronic Melody and the Edwards Sapien XT and Sapien 3 valves. In this report, we describe the case of a 49-year-old woman with severe bioprosthetic tricuspid valvular stenosis and multiple comorbidities who underwent transcatheter tricuspid valve replacement with a Sapien 3 valve.

Transcatheter Aortic Valve Implantation in a Patient with Unicuspid Aortic Valve

Transcatheter aortic valve replacement (TAVR) in patients with bicuspid aortic valves has been successfully performed, but there is a lack of published experience in percutaneous treatment of patients with unicuspid valves and severe aortic stenosis. We describe a case of TAVR in such a patient. A 31-year-old woman with Turner syndrome-who had undergone coarctation repair via subclavian flap at age 7 days and an aortic valvotomy at age 6 weeks-presented with severe symptomatic aortic stenosis. She was deemed inoperable because of her severe pulmonary hypertension and numerous comorbidities; consequently, a 20-mm Edwards Sapien 3 Transcatheter Heart Valve was offered for compassionate use. Postdeployment angiography and transesophageal echocardiography and aortography revealed no aortic insufficiency. Transcatheter aortic valve replacement for unicuspid aortic valve stenosis is technically feasible. Before implantation, particular attention should be paid to the interplay between the large single leaflet, coronary ostia, and stented valve, to select the correct size and position of the device. Some degree of intraoperative aortic migration should be anticipated.

Transcatheter Pulmonary Valve Replacement in a Carcinoid Heart

Carcinoid heart disease presents as right-sided heart failure attributable to the dysfunction of the tricuspid and pulmonary valves. Although surgical valve replacement is the mainstay of treatment when patients become symptomatic, it is associated with substantial perioperative mortality rates. We present a case of severe pulmonary valve stenosis secondary to carcinoid heart disease, treated successfully with percutaneous valve replacement. A 67-year-old man with severe pulmonary valve stenosis was referred to our center for pulmonary valve replacement. The patient had a history of metastatic neuroendocrine tumor of the small bowel with carcinoid syndrome, carcinoid heart disease, and tricuspid valve regurgitation previously treated with surgical valve replacement. Because of the patient's severe chronic obstructive pulmonary disease and hostile chest anatomy seen on a computed tomographic scan dating from previous cardiothoracic surgery, we considered off-label percutaneous valve replacement a viable alternative to open-heart surgery. A 29-mm Edwards Sapien XT valve was successfully deployed over the native pulmonary valve. There were no adverse sequelae after the procedure, and the patient was discharged from the hospital the next day. This case report shows that percutaneous valve replacement can be a valid option in carcinoid heart disease patients who are not amenable to surgical valve replacement.

Percutaneous coronary intervention with the TandemHeart™ percutaneous left ventricular assist device support: Six years of experience and outcomes

OBJECTIVES

Our study was designed to evaluate the outcomes of TandemHeart™ assistance during percutaneous coronary intervention, specifically in relationship to pre-procedural clinical and hemodynamic risk factors in patients ineligible for surgical revascularization.

BACKGROUND

We have used the TandemHeart™ percutaneous left ventricular assist device during percutaneous coronary intervention (PCI) in patients for whom conventional PCI and aorto-coronary bypass would pose substantial risk owing to comorbidities and/or clinical presentations.

METHODS

We retrospectively analyzed data from 626 consecutive PCIs at the Texas Heart Institute from 2005 to 2011. Among these, 74 interventions were performed with TandemHeart™ support. Mortality and morbidity were analyzed in relationship to presentation status (elective, urgent, emergent, or emergent salvage), and then we recorded outcomes and survival rates over the course of six years.

RESULTS

At 30 days after PCI, survival rates were 94%, 88%, 79%, and 55% in the elective, urgent, emergent, and emergent salvage groups, respectively. Survival rates at one year were at 75% in the elective, 64% in the urgent, 52% in the emergent, and 45% in the emergent salvage groups. Survival rates at 6 years were 68% in the elective, 53% in the urgent, 31% in the emergent, and 41% in the emergent salvage groups, respectively. In elective and urgent groups, successful weaning from mechanical support was possible in all patients. In the emergent and emergent salvage groups, successful weaning from mechanical support was possible in 84% and 55% of patients, respectively.

CONCLUSIONS

TandemHeart™ assisted PCI is a viable option for revascularization in cases of profound cardiogenic shock or extremely risky intervention due to complex anatomy. © 2015 Wiley Periodicals, Inc.

Transcatheter aortic valve implantation despite challenging vascular access

We describe transcatheter aortic valve implantation in a patient who had severe peripheral artery disease. The patient's vascular condition required additional preliminary peripheral intervention to enable adequate vascular access. A 78-year-old man with severe aortic stenosis, substantial comorbidities, and severe heart failure symptoms was referred for aortic valve replacement. The patient's 20-mm aortic annulus necessitated the use of a 23-mm Edwards Sapien valve inserted through a 22F sheath, which itself needed a vessel diameter of at least 7 mm for percutaneous delivery. The left common femoral artery was selected for valve delivery. The left iliac artery and infrarenal aorta underwent extensive intervention to achieve an intraluminal diameter larger than 7 mm. After aortic valvuloplasty, valve deployment was successful, and the transaortic gradient decreased from 40 mmHg to less than 5 mmHg. The patient was discharged from the hospital 4 days postoperatively. We conclude that transcatheter aortic valve implantation can be successfully performed in patients with obstructed vascular access, including stenosis of the infrarenal aorta and the subclavian and coronary arteries.

Association between cell-derived microparticles and adverse events in patients with nonpulsatile left ventricular assist devices

BACKGROUND

Continuous-flow left ventricular assist devices (LVADs) expose blood cells to high shear stress, potentially resulting in the production of microparticles that express phosphatidylserine (PS+) and promote coagulation and inflammation. In this prospective study, we attempted to determine whether PS+ microparticle levels correlate with clinical outcomes in LVAD-supported patients.

METHODS

We enrolled 20 patients undergoing implantation of the HeartMate II LVAD (Thoratec Corp, Pleasanton, CA) and 10 healthy controls who provided reference values for the microparticle assays. Plasma was collected before LVAD implantation, at discharge, at the 3-month follow-up, and when an adverse clinical event occurred. We quantified PS+ microparticles in the plasma using flow cytometry.

RESULTS

During the study period, 8 patients developed adverse clinical events: ventricular tachycardia storm in 1, non-ST-elevation myocardial infarction in 2, arterial thrombosis in 2, gastrointestinal bleeding in 2, and stroke in 3. Levels of PS+ microparticles were higher in patients at baseline than in healthy controls (2.11% ± 1.26% vs 0.69% ± 0.46%, p = 0.007). After LVAD implantation, patient PS+ microparticle levels increased to 2.39% ± 1.22% at discharge and then leveled to 1.97% ± 1.25% at the 3-month follow-up. Importantly, levels of PS+ microparticles were significantly higher in patients who developed an adverse event than in patients with no events (3.82% ± 1.17% vs 1.57% ± 0.59%, p < 0.001), even though the 2 patient groups did not markedly differ in other clinical and hematologic parameters.

CONCLUSIONS

Our results suggest that an elevation of PS+ microparticle levels may be associated with adverse clinical events. Thus, measuring PS+ microparticle levels in LVAD-supported patients may help identify patients at increased risk for adverse events.

Aortic valve regurgitation that resolved after a ruptured coronary sinus aneurysm was patched

Sinus of Valsalva aneurysms appear to be rare. They occur most frequently in the right sinus of Valsalva (52%) and the noncoronary sinus (33%). More of these aneurysms originate from the right coronary cusp than from the noncoronary cusp. Surgical intervention is usually recommended when symptoms become evident. We report the case of a 34-year-old woman who presented with a congenital, ruptured sinus of Valsalva aneurysm that originated from the noncoronary cusp. Moderate aortic regurgitation was associated with this lesion. Simple, direct patch closure of the ruptured aneurysm resolved the patient's left-to-right shunt and was associated with decreased aortic regurgitation to a degree that valve replacement was not necessary. Only trace residual aortic regurgitation was evident after 3 months, and the patient remained free of symptoms after 6 months. Our observations support the idea that substantial runoff blood flow in the immediate supra-annular region can be responsible for aortic regurgitation in the absence of a notable structural defect in the aortic valve, and that restoring physiologic flow in this region and equalizing aortic-cusp closure pressure can largely or completely resolve aortic insufficiency. Accordingly, valve replacement may not be necessary in all cases of ruptured sinus of Valsalva aneurysms with associated aortic valve regurgitation.

Concomitant transapical mitral valvuloplasty and CentriMag assist device placement: in a "no-option" patient

Left ventricular assist devices and percutaneous valve interventions have radically changed the treatment of advanced heart disease and minimized surgical morbidity in patients with end-stage heart failure who would not survive conventional surgery. We describe a successful approach to the simultaneous placement of a percutaneous left ventricular assist device and mitral valvuloplasty in a decompensated patient with end-stage ischemic cardiomyopathy, severe peripheral arterial disease, porcelain aorta, and severe mitral and aortic disease.

Superior vena cava thrombosis and paradoxical embolic stroke due to collateral drainage from the brachiocephalic vein to the left atrium

Thrombosis involving a permanent infusion catheter in the subclavian vein and superior vena cava is relatively common, especially in cancer patients. Edema of the arms and head is a well-known clinical consequence of this thrombosis, with an intrinsic risk of pulmonary embolism; however, systemic embolization into the cerebral circulation has not been reported as a sequela. Herein, we describe the case of a 56-year-old man with metastatic prostate cancer who developed superior vena cava syndrome due to extensive thrombosis in the presence of a central venous catheter that was used for long-term chemotherapy. The patient's case was complicated by a cerebrovascular accident that was most likely caused by a paradoxical air embolism. A clear mechanism for the embolism was provided by a network of collateral veins, which developed between the brachiocephalic vein and the left atrium due to the superior vena cava obstruction and resulted in a right-to-left shunt. We discuss diagnosis and treatment of the condition in our patient and in general terms.

Acute thrombocytopenia after liver transplant: role of platelet activation, thrombopoietin deficiency and response to high dose intravenous IgG treatment

BACKGROUND/AIMS

Thrombocytopenia is common after liver transplantation due to platelet sequestration secondary to hypersplenism. The aim of this study was to further investigate the causes of this condition, as well as the response of thrombocytopenia to high dose intravenous immunoglobulins.

METHODS

We retrospectively studied 73 patients who underwent liver transplantation. Out of these 73 patients, 27 had severe thrombocytopenia and were treated with high dose intravenous immunoglobulin. Additionally, we retrospectively studied 8 patients undergoing liver transplantation.

RESULTS

Our data suggest that splenomegaly is not the only factor responsible for thrombocytopenia after liver transplantion and two additional phenomena, namely, reduced platelet production due to reduced thrombopoietin levels and sustained platelets activation take part in the pathogenesis of this condition. The infusion of high dose immunoglobulins induced a safe, prompt, complete and persistent resolution of severe thrombocytopenia in more than 70% of patients.

CONCLUSIONS

Based on these findings, treatment with high dose intravenous immunoglobulins should be considered in the management of severe thrombocytopenia after liver transplant, although additional randomized trials are warranted.

Human cardiac stem cells

The identification of cardiac progenitor cells in mammals raises the possibility that the human heart contains a population of stem cells capable of generating cardiomyocytes and coronary vessels. The characterization of human cardiac stem cells (hCSCs) would have important clinical implications for the management of the failing heart. We have established the conditions for the isolation and expansion of c-kit-positive hCSCs from small samples of myocardium. Additionally, we have tested whether these cells have the ability to form functionally competent human myocardium after infarction in immunocompromised animals. Here, we report the identification in vitro of a class of human c-kit-positive cardiac cells that possess the fundamental properties of stem cells: they are self-renewing, clonogenic, and multipotent. hCSCs differentiate predominantly into cardiomyocytes and, to a lesser extent, into smooth muscle cells and endothelial cells. When locally injected in the infarcted myocardium of immunodeficient mice and immunosuppressed rats, hCSCs generate a chimeric heart, which contains human myocardium composed of myocytes, coronary resistance arterioles, and capillaries. The human myocardium is structurally and functionally integrated with the rodent myocardium and contributes to the performance of the infarcted heart. Differentiated human cardiac cells possess only one set of human sex chromosomes excluding cell fusion. The lack of cell fusion was confirmed by the Cre-lox strategy. Thus, hCSCs can be isolated and expanded in vitro for subsequent autologous regeneration of dead myocardium in patients affected by heart failure of ischemic and nonischemic origin.

Stem cell niches in the adult mouse heart

Cardiac stem cells (CSCs) have been identified in the adult heart, but the microenvironment that protects the slow-cycling, undifferentiated, and self-renewing CSCs remains to be determined. We report that the myocardium possesses interstitial structures with the architectural organization of stem cell niches that harbor long-term BrdU-retaining cells. The recognition of long-term label-retaining cells provides functional evidence of resident CSCs in the myocardium, indicating that the heart is an organ regulated by a stem cell compartment. Cardiac niches contain CSCs and lineage-committed cells, which are connected to supporting cells represented by myocytes and fibroblasts. Connexins and cadherins form gap and adherens junctions at the interface of CSCs-lineage-committed cells and supporting cells. The undifferentiated state of CSCs is coupled with the expression of alpha(4)-integrin, which colocalizes with the alpha(2)-chain of laminin and fibronectin. CSCs divide symmetrically and asymmetrically, but asymmetric division predominates, and the replicating CSC gives rise to one daughter CSC and one daughter committed cell. By this mechanism of growth kinetics, the pool of primitive CSCs is preserved, and a myocyte progeny is generated together with endothelial and smooth muscle cells. Thus, CSCs regulate myocyte turnover that is heterogeneous across the heart, faster at the apex and atria, and slower at the base-midregion of the ventricle.

Cardiac Stem Cells Possess Growth Factor-Receptor Systems That After Activation Regenerate the Infarcted Myocardium, Improving Ventricular Function and Long-Term Survival

Cardiac stem cells and early committed cells (CSCs-ECCs) express c-Met and insulin-like growth factor-1 (IGF-1) receptors and synthesize and secrete the corresponding ligands, hepatocyte growth factor (HGF) and IGF-1. HGF mobilizes CSCs-ECCs and IGF-1 promotes their survival and proliferation. Therefore, HGF and IGF-1 were injected in the hearts of infarcted mice to favor, respectively, the translocation of CSCs-ECCs from the surrounding myocardium to the dead tissue and the viability and growth of these cells within the damaged area. To facilitate migration and homing of CSCs-ECCs to the infarct, a growth factor gradient was introduced between the site of storage of primitive cells in the atria and the region bordering the infarct. The newly-formed myocardium contained arterioles, capillaries, and functionally competent myocytes that with time increased in size, improving ventricular performance at healing and long thereafter. The volume of regenerated myocytes was 2200 μm 3 at 16 days after treatment and reached 5100 μm 3 at 4 months. In this interval, nearly 20% of myocytes reached the adult phenotype, varying in size from 10 000 to 20 000 μm 3 . Moreover, there were 43±13 arterioles and 155±48 capillaries/mm 2 myocardium at 16 days, and 31±6 arterioles and 390±56 capillaries at 4 months. Myocardial regeneration induced increased survival and rescued animals with infarcts that were up to 86% of the ventricle, which are commonly fatal. In conclusion, the heart has an endogenous reserve of CSCs-ECCs that can be activated to reconstitute dead myocardium and recover cardiac function.

Stem cells in the dog heart are self-renewing, clonogenic, and multipotent and regenerate infarcted myocardium, improving cardiac function

The purpose of this study was to determine whether the heart in large mammals contains cardiac progenitor cells that regulate organ homeostasis and regenerate dead myocardium after infarction. We report that the dog heart possesses a cardiac stem cell pool characterized by undifferentiated cells that are self-renewing, clonogenic, and multipotent. These clonogenic cells and early committed progeny possess a hepatocyte growth factor (HGF)-c-Met and an insulin-like growth factor 1 (IGF-1)-IGF-1 receptor system that can be activated to induce their migration, proliferation, and survival. Therefore, myocardial infarction was induced in chronically instrumented dogs implanted with sonomicrometric crystals in the region of the left ventricular wall supplied by the occluded left anterior descending coronary artery. After infarction, HGF and IGF-1 were injected intramyocardially to stimulate resident cardiac progenitor cells. This intervention led to the formation of myocytes and coronary vessels within the infarct. Newly generated myocytes expressed nuclear and cytoplasmic proteins specific of cardiomyocytes: MEF2C was detected in the nucleus, whereas alpha-sarcomeric actin, cardiac myosin heavy chain, troponin I, and alpha-actinin were identified in the cytoplasm. Connexin 43 and N-cadherin were also present. Myocardial reconstitution resulted in a marked recovery of contractile performance of the infarcted heart. In conclusion, the activation of resident primitive cells in the damaged dog heart can promote a significant restoration of dead tissue, which is paralleled by a progressive improvement in cardiac function. These results suggest that strategies capable of activating the growth reserve of the myocardium may be important in cardiac repair after ischemic injury.

Bone marrow cells differentiate in cardiac cell lineages after infarction independently of cell fusion

Recent studies in mice have challenged the ability of bone marrow cells (BMCs) to differentiate into myocytes and coronary vessels. The claim has also been made that BMCs acquire a cell phenotype different from the blood lineages only by fusing with resident cells. Technical problems exist in the induction of myocardial infarction and the successful injection of BMCs in the mouse heart. Similarly, the accurate analysis of the cell populations implicated in the regeneration of the dead tissue is complex and these factors together may account for the negative findings. In this study, we have implemented a simple protocol that can easily be reproduced and have reevaluated whether injection of BMCs restores the infarcted myocardium in mice and whether cell fusion is involved in tissue reconstitution. For this purpose, c-kit-positive BMCs were obtained from male transgenic mice expressing enhanced green fluorescence protein (EGFP). EGFP and the Y-chromosome were used as markers of the progeny of the transplanted cells in the recipient heart. By this approach, we have demonstrated that BMCs, when properly administrated in the infarcted heart, efficiently differentiate into myocytes and coronary vessels with no detectable differentiation into hemopoietic lineages. However, BMCs have no apparent paracrine effect on the growth behavior of the surviving myocardium. Within the infarct, in 10 days, nearly 4.5 million biochemically and morphologically differentiated myocytes together with coronary arterioles and capillary structures were generated independently of cell fusion. In conclusion, BMCs adopt the cardiac cell lineages and have an important therapeutic impact on ischemic heart failure.

Autologous Peripheral Blood Stem Cell Transplantation for Myocardial Regeneration: A Novel Strategy for Cell Collection and Surgical Injection

PURPOSE

Bone-marrow and peripheral blood-derived stem cells can be used as stimulators of myogenesis and angiogenesis. We describe an original technique for collection and surgical intramyocardial injection of peripheral blood-derived stem cells.

DESCRIPTION

Stem cells are mobilized from the bone marrow by means of subcutaneous administration of Lenogastrim (Granocyte 34 [Aventis Pharma, Milan, Italy]) for 4 days. Then the day before the operation the peripheral blood-derived stem cells are collected by means of apheresis and processed in order to obtain the CD 133+ cells. Cells are injected into the myocardium in a beating heart in order to induce angiogenesis locally or myogenesis, or both. When necessary, off-pump coronary artery bypass grafting is previously accomplished.

EVALUATION

Thus far we have investigated 4 patients (3 patients who have received off-pump peripheral blood stem cell injection and coronary bypass grafting through median sternotomies, and 1 patient who underwent cell transplant alone through a minimally-invasive transdiaphragmatic approach). No complications were noted at a mean of 4 months after surgery.

CONCLUSIONS

This novel method of peripheral bone marrow stem cell collection and intramyocardial injection seems to be safe, feasible, and reproducible. However, there is need of further evidence to definitely assess safety issues and clinical results.