Brian A. Bruckner

Regression of fibrosis and hypertrophy in failing myocardium following mechanical circulatory support.

BACKGROUND The cellular and structural changes that occur during long-term ventricular unloading leading to cardiac recovery are poorly understood. However, we have previously demonstrated that left ventricular assist device (LVAD) support leads to a significant decrease in intracardiac tumor necrosis factor-alpha (TNF-alpha), a protein capable of producing hypertrophy and fibrosis. METHODS To further define the beneficial effects of long-term ventricular unloading on cardiac function, we determined the effect of mechanical circulatory support on fibrosis and hypertrophy in paired myocardial samples of 18 patients with end-stage cardiomyopathy obtained at the time of LVAD implantation and removal. RESULTS We determined total collagen as well as collagen I and III by a semiquantitative analysis of positive immune-stained areas in pre- and post-LVAD myocardial samples. We found that total collagen content was reduced by 72% (p < 0.001), whereas collagen I content decreased by 66% (p < 0.001) and collagen III content was reduced by 62% (p < 0.001). Next, we determined myocyte size by direct analysis of cellular dimensions utilizing a computerized edge detection system in pre- and post-LVAD myocardial samples. We found that myocyte size decreased in all patients studied for an average reduction of 26% (33.1 +/- 1.32 to 24.4 +/- 1.64 microm, p < 0.001). CONCLUSION These data demonstrate that long-term mechanical circulatory support significantly reduces collagen content and decreases myocyte size. We suggest that the reduction of fibrosis and hypertrophy observed may in part contribute to the recovery of cardiac function associated with long-term mechanical circulatory support.

Blockade of IL-6 Trans Signaling Attenuates Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease with progressive fibrosis and death within 2–3 y of diagnosis. IPF incidence and prevalence rates are increasing annually with few effective treatments available. Inhibition of IL-6 results in the attenuation of pulmonary fibrosis in mice. It is unclear whether this is due to blockade of classical signaling, mediated by membrane-bound IL-6Rα, or trans signaling, mediated by soluble IL-6Rα (sIL-6Rα). Our study assessed the role of sIL-6Rα in IPF. We demonstrated elevations of sIL-6Rα in IPF patients and in mice during the onset and progression of fibrosis. We demonstrated that protease-mediated cleavage from lung macrophages was important in production of sIL-6Rα. In vivo neutralization of sIL-6Rα attenuated pulmonary fibrosis in mice as seen by reductions in myofibroblasts, fibronectin, and collagen in the lung. In vitro activation of IL-6 trans signaling enhanced fibroblast proliferation and extracellular matrix protein production, effects relevant in the progression of pulmonary fibrosis. Taken together, these findings demonstrate that the production of sIL-6Rα from macrophages in the diseased lung contributes to IL-6 trans signaling that in turn influences events crucial in pulmonary fibrosis.

Degree of cardiac fibrosis and hypertrophy at time of implantation predicts myocardial improvement during left ventricular assist device support

BACKGROUND There have been increasing reports of cardiac improvement in heart failure patients supported by left ventricular assist devices (LVADs i.e.), including a number of patients who have tolerated removal of the device without the benefit of cardiac transplant. In the current study, we retrospectively investigated echocardiographic and histologic changes in patients supported by LVADs (n = 18). The goal of our study was to determine if the degree of cardiac fibrosis and myocyte size in pre-implant biopsies could predict myocardial improvement as assessed by improvements in ejection fraction (EF) during LVAD support. METHODS We determined total collagen content in myocardial biopsy specimens by a semi-quantitative analysis of positive Picro-Sirius Red-stained areas and myocyte size measurements by computerized edge detection software. RESULTS During LVAD support, 9 of the 18 patients (Group A) were distinguished by significant improvement in ejection fraction (pre <20% vs unloaded 34 +/- 5%). In addition, Group A patients had significantly less fibrosis and smaller myocytes than their Group B counterparts, whose EF did not improve. There was an inverse correlation between pre-implant biopsy collagen levels and myocyte size with increases in EF during LVAD unloading. CONCLUSIONS We found that the patients who demonstrated the greatest improvements in EF during support had less fibrosis and smaller myocytes at the time of device implantation. We propose that tissue profiling a patients pre-implant biopsy for fibrosis and myocyte size may allow stratification in Stage IV heart failure and may predict myocardial improvement during LVAD support.

Reversal of secondary pulmonary hypertension by axial and pulsatile mechanical circulatory support.

BACKGROUND Pulmonary hypertension associated with chronic congestive heart failure posses a significant risk of morbidity and death after heart transplantation. Isolated observations suggest that chronic ventricular unloading may lead to normalization of pulmonary pressures and thus render a patient likely to be a heart transplant candidate. METHODS This study is a retrospective analysis of 9 heart failure patients with secondary pulmonary hypertension (transpulmonary gradient [TPG] > 15 mm/Hg). Two were treated with a pulsatile left ventricular assist device (LVAD) and 7 with an axial-flow LVAD. RESULTS After LVAD support, mean pulmonary artery pressure decreased from 39 +/- 7 to 31 +/- 5 mm Hg, and the TPG decreased from 19 +/- 3 to 13 +/- 4 mm Hg (p < 0.01). The 1-year Kaplan-Meier survival curve for patients with pre-LVAD TPG > 15 mm Hg vs those with TPG < 15 mm Hg showed no difference in survival (p = 0.6). This finding was supported by analysis of a large multi-institutional cohort obtained from the Organ Procurement and Transplantation Network database, where no differences in survival were found in the same groups. CONCLUSIONS Pulmonary hypertension that is secondary to congestive heart failure, as defined by a TPG > 15 mm Hg can be reversed by the use of pulsatile and axial-flow LVADs; furthermore, post-transplant survival for patients with secondary pulmonary hypertension treated with an LVAD was no different than for those without pulmonary hypertension who received LVAD support.

The implications for cardiac recovery of left ventricular assist device support on myocardial collagen content.

BACKGROUND To define the beneficial cellular changes that occur with chronic ventricular unloading, we determined the effect of left ventricular assist device (LVAD) placement on myocardial fibrosis. METHODS We obtained paired myocardial samples (before and after LVAD implantation) from 10 patients (aged 43 to 64 years) with end-stage cardiomyopathy. We first determined regional collagen expression of an explanted heart by a computerized semiquantitative analysis of positive picro-sirius red stained areas. RESULTS We found that there was no statistically significant difference in collagen content between regions of the failed heart studied. Next we determined collagen content in these paired myocardial biopsies pre- and post-LVAD implantation. All 10 patients had significant reductions in collagen content after LVAD placement with a mean reduction of 82% (percent of tissue area stained decreased from 32% +/- 4% to 4% +/- 0.8%, P < 0.001). CONCLUSION In summary, these data demonstrate that chronic mechanical circulatory support significantly reduces fibrosis in the failing myocardium.

Increased right-to-left ventricle diameter ratio is a strong predictor of right ventricular failure after left ventricular assist device.

BACKGROUND Predictors of right ventricular failure (RVF) in patients with left ventricular assist devices (LVADs) have not been fully elucidated and are comprised mostly of clinical variables. We evaluated echocardiographic parameters associated with adverse outcomes in this population. METHODS Transthoracic echocardiograms (TTEs) before continuous-flow LVAD implantation were analyzed in 109 patients. Twenty-six 2-dimensional and Doppler parameters were assessed for their association with the primary outcome of 30-day RVF, defined as a requirement of an RV assist device or ≥ 14 consecutive days of inotropic support, and the secondary composite outcome of 30-day death or RVF. Multivariate analysis adjusted for known clinical risk prediction models was performed. RESULTS Overall, 25 (22.9%) and 27 (24.8%) patients reached the primary and secondary end-points, respectively. An increased RV/LV diameter ratio was the only TTE variable independently associated with both the primary (odds ratio [OR] = 5.40; 95% confidence interval [CI] 2.40 to 12.40; p = 0.012) and secondary (OR = 2.70; 95% CI 1.06 to 6.22; p = 0.03) outcomes after multivariate analysis. Scatterplot analysis with regression determined the optimal cut-off value for RV/LV diameter to be 0.75. Based on receiver operating characteristic curves, an increased RV/LV diameter ratio provided an additional predictive value to clinical risk scores. CONCLUSIONS A TTE-measured RV/LV diameter ratio of ≥0.75 is independently associated with a higher risk for RVF in patients with continuous-flow LVAD. When used alone, this simple, easily derived, practical echocardiographic measurement has a predictive value equivalent to known clinical risk scores, whereas their combination provides stronger risk prediction for adverse outcomes.

Percutaneous Placement of an Intra-Aortic Balloon Pump in the Left Axillary/Subclavian Position Provides Safe, Ambulatory Long-Term Support as Bridge to Heart Transplantation

OBJECTIVES This study evaluated the feasibility, tolerability, and efficacy of a strategy for percutaneous intra-aortic balloon pump (IABP) placement through the left axillary-subclavian artery to provide mechanical circulatory support in patients with end-stage heart failure as a bridge to heart transplantation. BACKGROUND The transfemoral approach to IABP placement is associated with major disadvantages, including the risk for infection and limitation of patient mobility in those requiring extended support. METHODS We developed a percutaneous technique for placing IABPs in the left axillary artery that permits upright sitting and ambulation. We performed a retrospective review of data from patients who had undergone left axillary IABP implantation between 2007 and 2012. RESULTS Fifty patients who received a left axillary IABP as a bridge to transplantation were identified, of whom 42 (84%) underwent heart or heart-multiorgan transplantation. Cumulative survival on IABP support was 92%, and post-transplant 90-day survival was 90%. Median duration of support was 18 days. Four of 50 patients (8%) died while on IABP support, and 3 (6%) received greater mechanical circulatory support. Four patients (8%) had clinically significant thromboembolic or bleeding events without long-term sequelae. The most common minor adverse event was IABP malposition, in 22 patients (44%). Prolonged IABP support in the heart-transplantation cohort was associated with significant improvements in mean pulmonary artery pressure and in creatinine and total bilirubin concentrations. CONCLUSIONS Percutaneous insertion of an IABP through the left axillary artery is a feasible and relatively well-tolerated strategy to bridge patients with end-stage heart failure to heart transplantation. This form of mechanical-device treatment permits upright sitting and ambulation in those requiring extended support.

Clinical experience with sternotomy versus subcostal approach for exchange of the HeartMate XVE to the HeartMate II ventricular assist device.

BACKGROUND Most patients undergoing destination therapy with a HeartMate XVE left ventricular assist device will eventually require pump exchange to continue long-term cardiac support. METHODS To determine whether left ventricular assist device exchange can be accomplished with low morbidity and mortality, we retrospectively reviewed the records of 14 patients who experienced pump malfunction and subsequently required replacement of their HeartMate XVE left ventricular assist devices with HeartMate II axial-flow pumps. We collected data regarding duration of support and reasons for pump failure, perioperative characteristics, and operative approach. RESULTS On average, patients were supported 473 +/- 233 days with HeartMate XVE pumps. Seven early patients required both subcostal and sternotomy incisions; 7 later patients had subcostal incisions only. Thirteen patients underwent successful exchange to the HeartMate II; 1 patient died in the operating room. Another patient died in the perioperative period (30-day mortality, 14% [2 of 14]). There were significant differences between the two groups. The patients who required only subcostal incisions had shorter operative times (187 versus 220 minutes; p = 0.04) and required fewer transfused blood products (packed red blood cells, 8.6 versus 28.7 units; p = 0.03; and fresh-frozen plasma, 12.4 versus 30.9 units; p = 0.04). Additionally, the patients with subcostal incisions had shorter postoperative intensive care unit stays (5.3 +/- 1.1 versus 8.4 +/- 3.1 days for redo sternotomy patients; p = 0.03). Of the survivors, average hospital stay was 22 +/- 14 days. Average long-term follow-up was 11.2 +/- 7.8 months; 71% (10 of 14) of patients are currently alive. CONCLUSIONS Exchange of a HeartMate XVE to a HeartMate II can be accomplished with relatively low morbidity and mortality through a subcostal approach.

Two-Year Outcomes with a Magnetically Levitated Cardiac Pump in Heart Failure

Background In an early analysis of this trial, use of a magnetically levitated centrifugal continuous‐flow circulatory pump was found to improve clinical outcomes, as compared with a mechanical‐bearing axial continuous‐flow pump, at 6 months in patients with advanced heart failure. Methods In a randomized noninferiority and superiority trial, we compared the centrifugal‐flow pump with the axial‐flow pump in patients with advanced heart failure, irrespective of the intended goal of support (bridge to transplantation or destination therapy). The composite primary end point was survival at 2 years free of disabling stroke (with disabling stroke indicated by a modified Rankin score of >3; scores range from 0 to 6, with higher scores indicating more severe disability) or survival free of reoperation to replace or remove a malfunctioning device. The noninferiority margin for the risk difference (centrifugal‐flow pump group minus axial‐flow pump group) was ‐10 percentage points. Results Of 366 patients, 190 were assigned to the centrifugal‐flow pump group and 176 to the axial‐flow pump group. In the intention‐to‐treat population, the primary end point occurred in 151 patients (79.5%) in the centrifugal‐flow pump group, as compared with 106 (60.2%) in the axial‐flow pump group (absolute difference, 19.2 percentage points; 95% lower confidence boundary, 9.8 percentage points [P<0.001 for noninferiority]; hazard ratio, 0.46; 95% confidence interval [CI], 0.31 to 0.69 [P<0.001 for superiority]). Reoperation for pump malfunction was less frequent in the centrifugal‐flow pump group than in the axial‐flow pump group (3 patients [1.6%] vs. 30 patients [17.0%]; hazard ratio, 0.08; 95% CI, 0.03 to 0.27; P<0.001). The rates of death and disabling stroke were similar in the two groups, but the overall rate of stroke was lower in the centrifugal‐flow pump group than in the axial‐flow pump group (10.1% vs. 19.2%; hazard ratio, 0.47; 95% CI, 0.27 to 0.84, P=0.02). Conclusions In patients with advanced heart failure, a fully magnetically levitated centrifugal‐flow pump was superior to a mechanical‐bearing axial‐flow pump with regard to survival free of disabling stroke or reoperation to replace or remove a malfunctioning device. (Funded by Abbott; MOMENTUM 3 ClinicalTrials.gov number, NCT02224755.)

Mechanical Unloading of the Failing Human Heart Fails to Activate the Protein Kinase B/Akt/Glycogen Synthase Kinase-3β Survival Pathway

Background: Left ventricular assist device (LVAD) support of the failing human heart improves myocyte function and increases cell survival. One potential mechanism underlying this phenomenon is activation of the protein kinase B (PKB)/Akt/glycogen synthase kinase-3beta (GSK-3β) survival pathway. Methods and Results: Left ventricular tissue was obtained both at the time of implantation and explantation of the LVAD (n = 11). Six patients were diagnosed with idiopathic dilated cardiomyopathy, 4 patients with ischemic cardiomyopathy and 1 patient with peripartum cardiomyopathy. The mean duration of LVAD support was 205 ± 35 days. Myocyte diameter and phosphorylation of ERK were used as indices for reverse remodeling. Transcript levels of genes required for the activation of PKB/Akt (insulin-like growth factor-1, insulin receptor substrate-1) were measured by quantitative RT-PCR. In addition, we measured the relative activity of PKB/Akt and GSK-3β, and assayed for molecular and histological indices of PKB/Akt activation (cyclooxygenase mRNA levels and glycogen levels). Myocyte diameter and phosphorylation of ERK decreased with LVAD support. In contrast, none of the components of the PKB/Akt/GSK-3β pathway changed significantly with mechanical unloading. Conclusion: The PKB/Akt/GSK-3β pathway is not activated during LVAD support. Other signaling pathways must be responsible for the improvement of cellular function and cell survival during LVAD support.