Hypoxia Prevents Mitochondrial Dysfunction and Senescence in Human c-Kit+ Cardiac Progenitor Cells.

Senescence-associated dysfunction deleteriously affects biological activities of human c-Kit+ cardiac progenitor cells (hCPCs), particularly under conditions of in vitro culture. In comparison, preservation of self-renewal and decreases in mitochondrial reactive oxygen species (ROS) are characteristics of murine CPCs in vivo that reside within hypoxic niches. Recapitulating hypoxic niche oxygen tension conditions of ∼1% O2 in vitro for expansion of hCPCs rather than typical normoxic cell culture conditions (21% O2 ) could provide significant improvement of functional and biological activities of hCPCs. hCPCs were isolated and expanded under permanent hypoxic (hCPC-1%) or normoxic (hCPC-21%) conditions from left ventricular tissue explants collected during left ventricular assist device implantation. hCPC-1% exhibit increased self-renewal and suppression of senescence characteristics relative to hCPC-21%. Oxidative stress contributed to higher susceptibility to apoptosis, as well as decreased mitochondrial function in hCPC-21%. Hypoxia prevented accumulation of dysfunctional mitochondria, supporting higher oxygen consumption rates and mitochondrial membrane potential. Mitochondrial ROS was an upstream mediator of senescence since treatment of hCPC-1% with mitochondrial inhibitor antimycin A recapitulated mitochondrial dysfunction and senescence observed in hCPC-21%. NAD+ /NADH ratio and autophagic flux, which are key factors for mitochondrial function, were higher in hCPC-1%, but hCPC-21% were highly dependent on BNIP3/NIX-mediated mitophagy to maintain mitochondrial function. Overall, results demonstrate that supraphysiological oxygen tension during in vitro expansion initiates a downward spiral of oxidative stress, mitochondrial dysfunction, and cellular energy imbalance culminating in early proliferation arrest of hCPCs. Senescence is inhibited by preventing ROS through hypoxic culture of hCPCs. Stem Cells 2019;37:555-567.

Principles of HeartMate II implantation to avoid pump malposition and migration.

Proper left ventricular assist device (LVAD) insertion will help maximize LVAD flow and may reduce adverse events such as right heart failure and pump thrombosis. Although no standardized insertion technique has been universally accepted, the goals are: unobstructed inflow cannula, unobstructed outflow graft with avoidance of right ventricular compression, and prevention of pump migration. To achieve these objectives for the HeartMate II LVAD, we delineate four principles: proper pump pocket creation, optimized positioning of inflow cannula and outflow graft, proper pump position in the body, and fixation. These basic principles are easy to implement and have been beneficial in our patients, assuring long-term unobstructed LVAD flow.

Factors Related to Pump Thrombosis With the Heartmate II Left Ventricular Assist Device.

BACKGROUND: Recent reports suggested that HeartMate II (HMII) thrombosis rates may be higher in implants after 2011. We characterize events at HMII centers (>100 HMII implants) whose device thrombosis rates are equivalent or lower than reported by INTERMACS. METHODS: Seven centers pooled implants from 2011 through June 2013 to examine pump thrombus and identify characteristics and clinical strategies that potentially mitigate the risk. A total of 666 patients (age 59 ± 13 years; 81% male) were studied (support duration: 13.7 ± 8.3 months, cumulative: 759 patient years). Median target INR was 2.25 (range 2.0 to 2.5), and median pump speed was 9200 rpm (range 8600 to 9600). Pump thrombus was suspected with clinical evidence (e.g., hemolysis, positive ramp test) requiring intervention (e.g., anticoagulation therapy, pump exchange) or patient death. RESULTS: Suspected pump thrombus occurred in 24/666 (3.6%) patients within three months of implant. At six months, 38/666 (5.7%) had suspected pump thrombus including 24 (3.6%) resulting in pump exchange or death. Stroke (hemorrhagic: 0.049, and ischemic: 0.048 events/patient year) and survival (six months: 88 ± 1%; 1 year: 81 ± 2%) were consistent with national averages. Suspected pump thrombus patients were younger (55 ± 13 vs. 59 ± 13, p = 0.046) and had more females (31.6% vs. 18.3%, p = 0.054). There was no difference in indication, etiology of heart failure, or body size. CONCLUSIONS: This analysis demonstrates low HMII thrombus events. Minimization of risk factors by uniform implant techniques and consistent post-op management may reduce device thrombosis. A larger scale multicenter evaluation may better elucidate the difference in thrombus events between centers.

Cardiac interstitial tetraploid cells can escape replicative senescence in rodents but not large mammals.

Cardiomyocyte ploidy has been described but remains obscure in cardiac interstitial cells. Ploidy of c-kit+ cardiac interstitial cells was assessed using confocal, karyotypic, and flow cytometric technique. Notable differences were found between rodent (rat, mouse) c-kit+ cardiac interstitial cells possessing mononuclear tetraploid (4n) content, compared to large mammals (human, swine) with mononuclear diploid (2n) content. In-situ analysis, confirmed with fresh isolates, revealed diploid content in human c-kit+ cardiac interstitial cells and a mixture of diploid and tetraploid content in mouse. Downregulation of the p53 signaling pathway provides evidence why rodent, but not human, c-kit+ cardiac interstitial cells escape replicative senescence. Single cell transcriptional profiling reveals distinctions between diploid versus tetraploid populations in mouse c-kit+ cardiac interstitial cells, alluding to functional divergences. Collectively, these data reveal notable species-specific biological differences in c-kit+ cardiac interstitial cells, which could account for challenges in extrapolation of myocardial from preclinical studies to clinical trials.

Radiologic assessment of HeartMate II position: Minimal pump migration after long-term support.

BACKGROUND: Surgical positioning of the HeartMate II (HMII) left ventricular assist device assuring an unobstructed blood flow path is essential for optimal device function and hemodynamic support. We report a non-invasive radiologic assessment of HMII position after implant and long-term follow-up. METHODS: We reviewed 132 consecutive patients (age 64 ± 14 years; 86% male; 60% destination therapy) implanted with an HMII from January 2009 to December 2012 and followed for them for up to 4 years. A radiologist measured pump position, pocket depth and cannula angles using chest radiography. Changes over time were determined in 64 of these patients with pairs of radiographs immediately after implant and at an average of 2.0 ± 0.7 years of follow-up. RESULTS: The axis of the pump relative to the spine was 92 ± 10° at baseline and 94 ± 9° at 2 years (n = 64, p = 0.02), and inflow cannula angles averaged 21 ± 13° from vertical at baseline and 20 ± 12° at 2 years (p = not statistically significant). More than 90% of angle measurements showed <15° movement over the follow-up duration. There was a small but significant superior pump migration from a depth of 12.7 ± 2.7 cm to 10.4 ± 2.6 cm (p < 0.001). There were no cannula obstructions or instances of right ventricular assist device use. The 30-day operative mortality was 3.0%. Prolonged inotrope dependence occurred in 5.3% (7 of 126) of patients, and low rates of pump thrombosis of 0.018 event/patient-year (0 at 3 months) and stroke 0.074 event/patient-year were noted. CONCLUSION: Non-invasive radiographic measurements of surgical pump placement designed to avoid pump and cannula malposition demonstrate stable position with minimal pump migration.

Safety of Prothombin Complex Concentrate to Control Excess Bleeding During Continuous Flow LVAD Insertion.

In cardiovascular surgery, hemostatic complexities require the provision of blood products to control bleeding as well as the use of a number of hemostatic agents, some of which cause significant morbidity. Among these agents is prothrombin complex concentrates (PCC), however there is no clear consensus on PCC use in cardiovascular surgery. To investigate the safety of PCC in patients undergoing left ventricular assist device (LVAD) placement, we reviewed our single institution experience to examine the incidence of thromboembolic events and a variety of hospital markers including morbidity and mortality. A retrospective review was conducted of patients who underwent LVAD placement between January 2010 and October 2012. Patients who received intraoperative PCC constituted the PCC group (n = 41) and those who did not constituted the non-PCC group (n = 27). The overall incidence of thromboembolic events at 3 months postoperative was 12 (29.3%) in the PCC group compared with six (22.2%) in the non-PCC group, respectively (p > 0.05). Morbidity did not differ between groups and one patient in the PCC group died. The intraoperative use of PCC in LVAD insertion does not appear to be associated with a significant increase in thromboembolic events; however, larger randomized trials are needed to confirm these findings.

Safety of reduced anti-thrombotic strategies in HeartMate II patients: A one-year analysis of the US-TRACE Study.

BACKGROUND: Patients with bleeding complications during left ventricular assist device (LVAD) support often require a reduction in the recommended warfarin plus aspirin regimen. To characterize those who can be safely managed with a reduced anti-thrombotic strategy, the TRACE (STudy of Reduced Anti-Coagulation/Anti-platelEt Therapy in Patients with the HeartMate II LVAS) study was initiated in the United States (U.S.) and Europe. METHODS: The TRACE U.S. arm enrolled HeartMate II (HMII; Thoratec) outpatients on a regimen of reduced anti-thrombotic therapy (RT), defined as vitamin K antagonist (warfarin) only, aspirin only, or no anti-thrombotic agent. The indication for RT, changes in anti-thrombotic therapies, and patient outcomes after RT were documented. Results for patients reaching 12 months or outcome are presented here. RESULTS: Between April 2012 and June 2013, 100 HMII outpatients (85% men) on RT (median age 64.5 [interquartile range, 32, 82] years, 61% with ischemic etiology, 69% destination therapy) were enrolled from 9 U.S. sites. The primary reason for RT initiation was in response to a bleeding event (82%). Pharmacotherapy at RT initiation included warfarin only (38%), aspirin only (28%), or no anti-thrombotic agent (34%). Freedom from ischemic stroke at 1 year was 93.8% ± 2.5%, and freedom from device thrombosis was 92.7% ± 2.7%. Despite RT, a subsequent bleeding event occurred in 52%. CONCLUSIONS: Reducing anti-thrombotic therapies in response to bleeding among HMII patients was achievable but may be associated with a higher risk for device thrombosis. Furthermore, despite an RT strategy, bleeding often will persist in those prone to such events.

Infection in permanent circulatory support: experience from the REMATCH trial.

BACKGROUND: This analysis of the REMATCH Trial focuses on infection, which was an important source of morbidity and mortality. We use the information to suggest ways to decrease the incidence and effects of device-related infection. METHODS: Patients were randomized prospectively to receive left ventricular assist devices (LVADs) or optimal medical management (OMM) for end-stage heart failure. Infection variables included sepsis adjudicated as the cause of death; sepsis reported as a serious adverse event; percutaneous site or pocket infection; and pump housing, inflow- or outflow-tract infection. We compared the incidence and prevalence of events between groups and generated time-related descriptions. RESULTS: Survival with LVAD (n=68 patients) was superior to OMM survival (n=61 patients) with a 47% decrease in risk of death (p <0.001), but the aggregate adverse event rate was greater for patients with LVADs (risk ratio, 2.29; 95% confidence interval, 1.85-2.84). Freedom from sepsis in patients with LVADs was 58% at 1 year and 48% at 2 years after implantation with superior survival in non-septic patients (60% vs 39% at 1 year and 38% vs 8% at 2 years in non-septic vs septic patients with LVADs, p <0.06). Percutaneous site or pocket infection did not affect survival (p=0.86). The hazard for onset of sepsis peaked within the first 3 weeks after implantation. CONCLUSIONS: Survival is improved with permanent LVAD implantation compared with OMM therapy. However, infection causes substantial morbidity and mortality. Decreasing infections will increase survival and decrease morbidity in permanent LVAD recipients and will improve the risk-benefit ratio for permanent LVAD therapy.

Pump replacement for left ventricular assist device failure can be done safely and is associated with low mortality.

BACKGROUND: Although continuous-flow left ventricular assist devices (LVAD) are durable and reliable, device replacement will be inevitable in some patients. We evaluated the incidence and outcomes of pump replacement procedures with the HeartMate II (Thoratec Corporation, Pleasanton, CA) LVAD. METHODS: Data were obtained from 1,128 patients implanted from March 2005 to January 2010 with the HeartMate II during the clinical trials for bridge to transplant and destination therapy. The operative mortality associated with the replacement procedure was determined. RESULTS: The mean duration of HeartMate II support was 568 ± 535 days (cumulative duration: 1,755 patient-years, longest: 6.5 years). A total of 72 (6.4%) patients underwent 79 LVAD replacements (0.045 events/patient-year) of which 2 were in the initial operation and 77 in separate procedures. Reasons for replacement were percutaneous lead damage (36 events, 3.0%), device thrombosis (25 events, 2.1%), infection (7 events, 0.6%), and miscellaneous other (11 events, 0.9%). The median time to pump replacement was 428 days (range 0 to 1,474). Of the 77 replacement procedures, there were 5 (6.5%) operative deaths within 30 days. The causes of death were device thrombosis, right heart failure, multisystem organ failure, and bleeding. One year after exchange (median 2.1 years after initial implant), 30% had died, 5% were transplanted, and 65% were ongoing and alive. CONCLUSIONS: HeartMate II device failure requiring pump replacement is infrequent, but when required can be done safely. These data continue to provide encouraging evidence supporting HeartMate II use for long-term circulatory support.

Risk assessment for continuous flow left ventricular assist devices: does the destination therapy risk score work? An analysis of over 1,000 patients.

OBJECTIVES: This study sought to assess the utility of the Destination Therapy Risk Score (DTRS) in patients with continuous flow left ventricular assist devices (LVAD). BACKGROUND: The DTRS was developed to predict the risk of 90-day in-hospital mortality with pulsatile flow LVAD as destination therapy (DT). Despite ongoing use in patients with continuous flow devices, its utility has not been studied in such populations. METHODS: The DTRS was determined in 1,124 patients with the continuous flow HeartMate II (Thoratec Corporation, Pleasanton, California) LVAD as a bridge to transplant (BTT, n = 486) and DT (n = 638) and 114 DT patients with the pulsatile flow HeartMate XVE (Thoratec Corporation). Patients were divided into risk groups based on DTRS: low (0-8), medium (9-16), and high (>16). RESULTS: The 90-day in-hospital mortality for low-, medium-, and high-risk groups was 8%, 7%, and 16%, respectively, for BTT patients; 9%, 12%, and 19%, respectively, for DT patients; and 11%, 18%, and 25%, respectively, for XVE DT patients. The high-risk groups had more than a 2-fold increased risk of mortality compared with the low-risk groups. However, the area under the receiver-operating characteristic curve for 90-day in-hospital mortality yielded modest values ranging from 0.54 to 0.58 for the HeartMate II BTT and DT groups, respectively. Survival rates over 2 years were statistically significantly different as stratified by the 3 DTRS groups for patients implanted for DT but not for BTT. CONCLUSIONS: DTRS provides poor discrimination of mortality for BTT patients and only modest discrimination for DT patients receiving continuous flow LVAD.

Outcomes in advanced heart failure patients with left ventricular assist devices for destination therapy.

BACKGROUND: The HeartMate II (HMII) destination therapy (DT) trial demonstrated significant improvements in outcomes in continuous-flow left ventricular assist devices compared with patients implanted with the pulsatile-flow HeartMate XVE. The primary hypothesis of the current study is that trial patients enrolled after the initial data cohort would have better clinical outcomes. METHODS AND RESULTS: Two hundred eighty-one patients who underwent HMII for DT from May 2007 to March 2009 (Mid Trial [MT] group) were compared with the initial 133 HMII patients from March 2005 to May 2007 (Early Trial [ET] group). Patient entry criteria were the same during the 2 time periods. Survival, adverse events, and quality of life were compared between the 2 groups. Baseline characteristics were similar between the groups. Compared with the ET group, patients in the MT group had reduced adverse event rates for bleeding requiring transfusions (1.66 versus 1.13 events per patient-year, P<0.001), sepsis (0.38 versus 0.27, P=0.025), device-related infections (0.47 versus 0.27, P<0.001), and hemorrhagic stroke (0.07 versus 0.03, P=0.01). Other event rates were similar between groups including ischemic stroke (0.06 versus 0.05 events per patient-year, P=0.57). Survival at 1 year in the MT group was 73% versus 68% in the ET group (P=0.21). Additionally, there was a significant reduction in deaths caused by hemorrhagic stroke (P=0.01). Quality of life improvements were significant in both the groups (P<0.001). CONCLUSIONS: The benefit of DT therapy with the HMII is confirmed in subsequent trial patients, with improved adverse event rates and a strong trend for improvements in survival. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00121485.

Clinical strategies and outcomes in advanced heart failure patients older than 70 years of age receiving the HeartMate II left ventricular assist device: a community hospital experience.

OBJECTIVES: The primary objective of this study was to determine outcomes in left ventricular assist device (LVAD) patients older than age 70 years. BACKGROUND: Food and Drug Administration approval of the HeartMate II (Thoratec Corporation, Pleasanton, California) LVAD for destination therapy has provided an attractive option for older patients with advanced heart failure. METHODS: Fifty-five patients received the HeartMate II LVAD between October 5, 2005, and January 1, 2010, as part of either the bridge to transplantation or destination therapy trials at a community hospital. Patients were divided into 2 age groups: ≥ 70 years of age (n = 30) and < 70 years of age (n = 25). Outcome measures including survival, length of hospital stay, adverse events, and quality of life were compared between the 2 groups. RESULTS: Pre-operatively, all patients were in New York Heart Association functional class IV refractory to maximal medical therapy. Kaplan-Meier survival for patients ≥ 70 years of age (97% at 1 month, 75% at 1 year, and 70% at 2 years) was not statistically different from patients <7 0 years of age (96% 1 month, 72% at 1 year, and 65% at 2 years, p = 0.806). Average length of hospital stay for the ≥ 70-year age group was 24 ± 15 days, similar to that of the < 70-year age group (23 ± 14 days, p = 0.805). There were no differences in the incidence of adverse events between the 2 groups. Quality of life and functional status improved significantly in both groups. CONCLUSIONS: The LVAD patients ≥ 70 years of age have good functional recovery, survival, and quality of life at 2 years. Advanced age should not be used as an independent contraindication when selecting a patient for LVAD therapy at experienced centers.

Aortic valve closure associated with HeartMate left ventricular device support: technical considerations and long-term results.

BACKGROUND: Aortic valve integrity is crucial for optimal left ventricular assist device (LVAD) support. Pre-existing native aortic insufficiency, aortic valve incompetence acquired during support, as well as previously placed prosthetic aortic valves present unique problems for these patients. METHODS: We reviewed and analyzed data for 28 patients who underwent left ventricular outflow tract closure associated with HeartMate I (n =12) and HeartMate II (n = 16) LVAD insertion or exchange. Indications for valve closure, surgical technique, LVAD function, survival rates and complications were retrospectively analyzed. Survival rates were compared with those of HeartMate LVAD patients (n = 104) who did not undergo aortic valve closure. RESULTS: Indications for closure included native aortic valve insufficiency (10 patients), aortic valve deterioration after prolonged LVAD support (8 patients) and previously placed mechanical (9 patients) or bioprosthetic aortic prostheses (1 patient). There were 2 operative and 5 late deaths (mean 227 days post-operatively). Of the deaths, none were due to aortic valve closure. Actuarial survival was 78% at 1 year and 53% at 3 years, which was statistically better than for our patients with an intact aortic outflow (61% at 1 year, 45% at 3 years; p < 0.05). Five patients had transplants, 1 patient was successfully bridged to recovery, and 15 patients remain on LVAD support. No patient with outflow closure developed regurgitation, embolization or compromised LVAD support. CONCLUSION: Outflow tract closure in LVAD-supported patients is safe, often necessary and well tolerated.

Clinical management of continuous-flow left ventricular assist devices in advanced heart failure.

Continuous-flow left ventricular assist devices (LVAD) have emerged as the standard of care for advanced heart failure patients requiring long-term mechanical circulatory support. Evidence-based clinical management of LVAD-supported patients is becoming increasingly important for optimizing outcomes. In this state-of-art review, we propose key elements in managing patients supported with the new continuous-flow LVADs. Although most of the presented information is largely based on investigator experience during the 1,300-patient HeartMate II clinical trial, many of the discussed principles can be applied to other emerging devices as well. Patient selection, pre-operative preparation, and the timing of LVAD implant are some of the most important elements critical to successful circulatory support and are principles universal to all devices. In addition, proper nutrition management and avoidance of infectious complications can significantly affect morbidity and mortality during LVAD support. Optimizing intraoperative and peri-operative care, and the monitoring and treatment of other organ system dysfunction as it relates to LVAD support, are discussed. A multidisciplinary heart failure team must be organized and charged with providing comprehensive care from initial referral until support is terminated. Preparing for hospital discharge requires detailed education for the patient and family or friends, with provisions for emergencies and routine care. Implantation techniques, troubleshooting device problems, and algorithms for outpatient management, including the diagnosis and treatment of related problems associated with the HeartMate II, are discussed as an example of a specific continuous-flow LVAD. Ongoing trials with other continuous-flow devices may produce additional information in the future for improving clinical management of patients with these devices.

HeartMate left ventricular assist system exchange: results and technical considerations.

The duration times of left ventricular assist system (LVAS) support have increased because of prolonged wait times for transplant and the more frequent use of devices for destination therapy. The HeartMate LVAS, the only device approved for bridge to transplant and destination therapy, has limited durability, making replacement increasingly necessary. Since 1996, we have exchanged 19 left ventricular assist devices in 15 patients (11 men: mean age, 57.1 years; range, 33-77 years). Most of the devices (14) were replaced with the HeartMate vented electric/extended-lead vented electric pump; five devices were exchanged for a HeartMate II LVAS. Bearing failure was the most frequent reason for exchange (15 of 19 pumps); four of the 19 pumps also had active device-related infections at the time of exchange. There were no early deaths (30 days). Overall survival (Kaplan-Meier) was 85% at 1 year, 67% at 2 years, and 56% at 3 years. Three patients had transplants (mean, 518 days); six patients died during support (mean, 934 days), and six patients remain on LVAS support (mean, 1,219 days). One patient has been on device for over 6 years. Left ventricular assist devices exchange is becoming increasingly likely and can be associated with acceptably low-operative mortality rates and good intermediate-term survival.

Combined thigh flap for closure of massive trunk defect.

A massive trunk defect resulting from resection of recurrent sarcoma was reconstructed with a combined free flap incorporating medial, anterior, and lateral thigh tissues. This flap included the tensor fasciae latae, lateral thigh perforator, and rectus femoris, all based on the lateral femoral circumflex pedicle. A saphenous vein conduit enabled this flap to replace resected tissues at the lower thorax. Combining the three different commonly used thigh flaps on a single large pedicle enabled transfer of a 47.5 x 33.5-cm mega-flap.

Assessment of recurrent heart failure associated with left ventricular assist device dysfunction.

BACKGROUND: Patients with advanced heart failure may require long-term support with an intracorporeal left ventricular assist device (LVAD) before cardiac transplant, while awaiting myocardial recovery, or during destination therapy. Compared with the diagnosis of native heart dysfunction, there is less experience with the assessment of recurrent heart failure after LVAD placement. METHODS: Ten patients (9 men, 1 woman; age, 58 +/- 11 years) were studied after LVAD placement. Six patients were studied because of recurrent heart failure; the remaining 4 had other indications for study and are reported here as controls. Cardiac catheterization, including LVAD and cannulae catheterization, and angiography were performed. RESULTS: Inflow cannula valve regurgitation by LVAD angiography was found in 3 cases. Patients with regurgitation had a mean increased resting LVAD rate of 105 beats/min (range, 90-120); LVAD output exceeded forward cardiac output (LVAD - thermodilution cardiac output = +3.7 liters/min [0.6-6.4]). Inflow cannula obstruction identified with a filling phase pressure gradient between the left ventricle and the LVAD was found in 3 additional patients. Patients with obstruction had decreased resting LVAD rates (50 beats/min, all patients); LVAD output was less than the forward cardiac output (LVAD - thermodilution cardiac output = -2.3 liters/min [-0.8 to -3.5]). Compared with those with inflow valve regurgitation, patients with cannula obstruction had higher pulmonary capillary wedge pressures; phasic left ventricular pressure variation was reduced. Patients with cannula dysfunction underwent surgical intervention, and 4 of 6 were long-term survivors. CONCLUSIONS: When heart failure recurs after LVAD placement, abnormalities of the inflow cannula are common. Cardiac catheterization can confirm the diagnosis before surgical intervention. Hemodynamic coupling between the left ventricle and the LVAD is increased with inflow valve regurgitation and reduced with cannula obstruction.