Reverse electrophysiologic remodeling after cardiac mechanical unloading for end-stage nonischemic cardiomyopathy

Three-Dimensional Cultivation a Valuable Tool for Modelling Canine Mammary Gland Tumour Behaviour In Vitro

Cell cultivation has been one of the most popular methods in research for decades. Currently, scientists routinely use two-dimensional (2D) and three-dimensional (3D) cell cultures of commercially available cell lines and primary cultures to study cellular behaviour, responses to stimuli, and interactions with their environment in a controlled laboratory setting. In recent years, 3D cultivation has gained more attention in modern biomedical research, mainly due to its numerous advantages compared to 2D cultures. One of the main goals where 3D culture models are used is the investigation of tumour diseases, in both animals and humans. The ability to simulate the tumour microenvironment and design 3D masses allows us to monitor all the processes that take place in tumour tissue created not only from cell lines but directly from the patient's tumour cells. One of the tumour types for which 3D culture methods are often used in research is the canine mammary gland tumour (CMT). The clinically similar profile of the CMT and breast tumours in humans makes the CMT a suitable model for studying the issue not only in animals but also in women.

LVAD therapy as a catalyst to heart failure remission and myocardial recovery

The management of chronic heart failure over the past decade has witnessed tremendous strides in medical optimization and device therapy including the use of left ventricular assist devices (LVAD). What we once thought of as irreversible damage to the myocardium is now demonstrating signs of reverse remodeling and recovery. Myocardial recovery on the structural, molecular, and hemodynamic level is necessary for sufficient recovery to withstand explant and achieve sustained recovery post-LVAD. Guideline-directed medical therapy and unloading have been shown to aid in recovery with the potential to successfully explant the LVAD. This review will summarize medical optimization, assessment for recovery, explant methodologies and outcomes post-recovery with explant of durable LVAD.

Regression of cardiac hypertrophy in health and disease: mechanisms and therapeutic potential

Left ventricular hypertrophy is a leading risk factor for cardiovascular morbidity and mortality. Although reverse ventricular remodelling was long thought to be irreversible, evidence from the past three decades indicates that this process is possible with many existing heart disease therapies. The regression of pathological hypertrophy is associated with improved cardiac function, quality of life and long-term health outcomes. However, less than 50% of patients respond favourably to most therapies, and the reversibility of remodelling is influenced by many factors, including age, sex, BMI and disease aetiology. Cardiac hypertrophy also occurs in physiological settings, including pregnancy and exercise, although in these cases, hypertrophy is associated with normal or improved ventricular function and is completely reversible postpartum or with cessation of training. Studies over the past decade have identified the molecular features of hypertrophy regression in health and disease settings, which include modulation of protein synthesis, microRNAs, metabolism and protein degradation pathways. In this Review, we summarize the evidence for hypertrophy regression in patients with current first-line pharmacological and surgical interventions. We further discuss the molecular features of reverse remodelling identified in cell and animal models, highlighting remaining knowledge gaps and the essential questions for future investigation towards the goal of designing specific therapies to promote regression of pathological hypertrophy.

Baseline QRS duration associates with cardiac recovery in patients with continuous-flow left ventricular assist device implantation

Objective

In chronic heart failure (HF) patients supported with continuous-flow left ventricular assist device (CF-LVAD), we aimed to assess the clinical association of pre-LVAD QRS duration (QRSd) with post-LVAD cardiac recovery, and its correlation with pre- to post-LVAD change in left ventricular ejection fraction (LVEF) and left ventricular end-diastolic diameter (LVEDD).

Methods

Chronic HF patients (n = 402) undergoing CF-LVAD implantation were prospectively enrolled, at one of the centers comprising the U.T.A.H. (Utah Transplant Affiliated Hospitals) consortium. After excluding patients with acute HF etiologies, hypertrophic or infiltrative cardiomyopathy, and/or inadequate post-LVAD follow up (<3 months), 315 patients were included in the study. Cardiac recovery was defined as LVEF ≥ 40 % and LVEDD < 6 cm within 12 months post-LVAD implantation. Patients fulfilling this condition were termed as responders (R) and results were compared with non-responders (NR).

Results

Thirty-five patients (11 %) achieved 'R' criteria, and exhibited a 15 % shorter QRSd compared to 'NR' (123 ± 37 ms vs 145 ± 36 ms; p < 0.001). A univariate analysis identified association of baseline QRSd with post-LVAD cardiac recovery (OR: 0.986, 95 % CI: 0.976-0.996, p < 0.001). In a multivariate logistic regression model, after adjusting for duration of HF (OR: 0.990, 95 % CI: 0.983-0.997, p = 0.006) and gender (OR: 0.388, 95 % CI: 0.160-0.943, p = 0.037), pre-LVAD QRSd exhibited a significant association with post-LVAD cardiac structural and functional improvement (OR: 0.987, 95 % CI: 0.977-0.998, p = 0.027) and the predictive model showed a c-statistic of 0.73 with p < 0.001. The correlations for baseline QRSd with pre- to post-LVAD change in LVEF and LVEDD were also investigated in 'R' and 'NR' groups.

Conclusion

Chronic advanced HF patients with a shorter baseline QRSd exhibit an increased potential for cardiac recovery after LVAD support.

Electrophysiologic Changes and Their Effects on Ventricular Arrhythmias in Patients with Continuous-Flow Left Ventricular Assist Devices

Ventricular arrhythmias (VAs) continue even after left ventricular assist device (LVAD) implantation. The effect of LVAD on VAs is controversial. We investigated electrophysiologic changes after LVAD and its effects on VAs development. A total of 107 implantable cardioverter-defibrillator (ICD) patients, with LVAD, were included in this study. Electrocardiographic parameters including QRS duration (between the beginning of the QRS complex and the end of the S wave), QT duration (between the first deflection of the QRS complex and the end of the T wave) corrected QT (QTc), QTc dispersion, fragmented QRS (F-QRS), and ICD recordings before, and post-LVAD first year were analyzed. All sustained VAs were classified as polymorphic ventricular tachycardia (PVT) or monomorphic VT (MVT). The QRS, QT, QTc durations, and QTc dispersion had decreased significantly after LVAD implantation (p < 0.001 for all). Also MVT increased significantly from 28.9% to 49.5% (p = 0.019) whereas PVT decreased from 27.1% to 4.67% (p = 0.04) compared to pre-LVAD period. A strong correlation was found between QT shortening and the decrease in PVT occurrence. Besides, the increase in the F-QRS after LVAD was associated with post-LVAD de nova MVT development. Finally, F-QRS before LVAD was found as an independent predictor of post-LVAD late VAs in multivariate analysis. Pre-existing or newly developed F-QRS was associated with post-LVAD late VAs, and it may be used to determine the risk of VAs after LVAD implantation.

Proposal for a trial of early left ventricular venting during venoarterial extracorporeal membrane oxygenation for cardiogenic shock

Objective

Patients with profound cardiogenic shock may require venoarterial (VA) extracorporeal membrane oxygenation (ECMO) for circulatory support most commonly via the femoral vessels. The rate of cardiac recovery in this population remains low, possibly because peripheral VA-ECMO increases ventricular afterload. Whether direct ventricular unloading in peripheral VA-ECMO enhances cardiac recovery is unknown, but is being more frequently utilized. A randomized trial is warranted to evaluate the clinical effectiveness of percutaneous left ventricle venting to enhance cardiac recovery in the setting of VA-ECMO.

Methods

We describe the rationale, design, and initial testing of a randomized controlled trial of VA-ECMO with and without percutaneous left ventricle venting using a percutaneous micro-axial ventricular assist device.

Results

This is an ongoing prospective randomized controlled trial in adult patients with primary cardiac failure presenting in cardiogenic shock requiring peripheral VA-ECMO, designed to test the safety and effectiveness of percutaneous left ventricle venting in improving the rate of cardiac recovery.

Conclusions

The results of this nonindustry-sponsored trial will provide critical information on whether left ventricle unloading in peripheral VA-ECMO is safe and effective.

Management of ventricular arrhythmias in patients with LVAD

PURPOSE OF REVIEW

Left ventricular assist devices (LVADs) have extended the life expectancy of patients with heart failure. The hemodynamic support afforded by LVADs in this population has also resulted in patients having prolonged ventricular arrhythmias. The purpose of this article is to review the mechanisms of ventricular arrhythmias in LVADs and the available management strategies.

RECENT FINDINGS

Recent evidence suggests that prolonged ventricular arrhythmias may result in increased mortality in patients with LVADs.

SUMMARY

Successful management of ventricular arrhythmias in patients with LVAD requires interdisciplinary collaboration between electrophysiology and heart failure specialists. Medical management, including changes to LVAD changes, heart failure medication management, and antiarrhythmics constitute the initial treatment for ventricular arrhythmias. Surgical or endocardial ablation are reasonable options if VAs are refractory.

Tumor organoid models in precision medicine and investigating cancer-stromal interactions

Tumor development and progression require chemical and mechanical cues derived from cellular and non-cellular components in the tumor microenvironment, including the extracellular matrix (ECM), cancer-associated fibroblasts (CAFs), endothelial cells, and immune cells. Therefore, it is crucial to develop tissue culture models that can mimic in vivo cancer cell-ECM and cancer-stromal cell interactions. Three-dimensional (3D) tumor culture models have been widely utilized to study cancer development and progression. A recent advance in 3D culture is the development of patient-derived tumor organoid (PDO) models from primary human cancer tissue. PDOs maintain the heterogeneity of the primary tumor, which makes them more relevant for identifying therapeutic targets and verifying drug response. Other significant advances include development of 3D co-culture assays to investigate cell-cell interactions and tissue/organ morphogenesis, and microfluidic technology that can be integrated into 3D culture to mimic vasculature and blood flow. These advances offer spatial and temporal insights into cancer cell-stromal interactions and represent novel techniques to study tumor progression and drug response. Here, we summarize the recent progress in 3D culture and tumor organoid models, and discuss future directions and the potential of utilizing these models to study cancer-stromal interactions and direct personalized treatment.

Mapping and Ablation of Ventricle Arrhythmia in Patients with Left Ventricular Assist Devices

Ventricular arrhythmias (VA) constitute well-known problems in patients with left ventricular assist devices (LVADs), with incidence ranging from 18% to as high as 52%. Catheter ablation has become a common therapeutic intervention to treat drug-refractory VA, particularly with the increase and more widespread use of durable LVADs to bridge patients to transplantation or as destination therapy. In this article, we focus on etiology, mechanisms, periprocedural management, and mapping and ablation techniques in patients with LVADs and VA.

Catheter Ablation of Ventricular Tachycardia in Patients With a Ventricular Assist Device: A Systematic Review of Procedural Characteristics and Outcomes

OBJECTIVES

This is a systematic review summarizing the procedural characteristics and outcomes of ventricular assist device (VAD)-related ventricular tachycardia (VT) ablation.

BACKGROUND

Drug-refractory VT refractory commonly develops post-VAD implantation. Procedural and outcome data come from small series or case reports.

METHODS

An electronic search was performed using major databases. Primary outcomes were VT recurrence, mortality, and cardiac transplantation. Secondary endpoints were acute procedural success and procedural complications.

RESULTS

Eighteen studies were included, with a total of 110 patients (mean age 59.6 ± 11 years, 89% men; VT storm 34%). Scar-related re-entry was the predominant mechanism of VT (90.3%) and cannula-related VT in 19.3% cases. Electroanatomical mapping interference occurred in 1.8% of cases; there were no reports of catheter entrapment. Noninducibility of clinical VT was achieved in 77.9%; procedural complications occurred in 9.4%. At a mean follow-up of 263.5 ± 267.0 days, VT recurred in 43.6%, 23.4% underwent cardiac transplant, and 48.1% died. There were no procedural-related deaths and no death was directly related to ventricular arrhythmia. In follow-up, there was a significant reduction in implantable cardioverter-defibrillator therapies or shocks (57.1% vs. 23.8%). Ablation allowed VT storm termination in 90% of patients.

CONCLUSIONS

VAD-related VT is predominantly related to pre-existing intrinsic myocardial scar rather than inflow cannula site insertion. Catheter ablation is a reasonable treatment strategy, albeit with expectedly high rate of recurrence, transplantation, and mortality related to severe underlying disease.

Heart rate reduction after ivabradine might be associated with reverse electrical remodeling in patients with cardiomyopathy and left bundle branch block

Left bundle branch block increases the risk of death in patients with chronic heart failure. We herein report four clinical cases of patients with chronic heart failure caused by nonischemic cardiomyopathy with left bundle branch block that occurred when adding ivabradine to optimal medical therapy, resulting in reverse electrical and mechanical remodeling. This phenomenon might be explained by the effect of ivabradine on reverse remodeling of the left ventricle with improvement of intraventricular conduction.

Meta-Analysis of the Relation of Ventricular Arrhythmias to All-Cause Mortality After Implantation of a Left Ventricular Assist Device

Ventricular arrhythmias (VAs) are commonly reported after implantation of left ventricular assist devices (LVADs). Their relation to all-cause mortality and potential risk factors remains unclear. We conducted a meta-analysis of observational studies with the primary objective of evaluating the association of post-LVAD VAs with all-cause mortality at 60, 120, and 180 days. The secondary end point was the association of potential risk factors (cause of cardiomyopathy, indication for LVAD, and history of VA) with mortality in patients with post-LVAD VAs. We searched MEDLINE, Embase, and Cochrane Central from 2001 to 2015. Two reviewers independently searched, selected, and assessed quality of included studies with differences resolved by consensus. Data were collected and analyzed using random- and fixed-effect model, as appropriate, with inverse-variance weighting. Of 2,393 studies identified, 9 observational studies were eligible including 1,179 patients with a mean follow-up of 220 days. Post-LVAD VAs were associated with increased risk of all-cause mortality after adjusting for competing risk factors at 60 days (adjusted odds ratio [OR] 1.91, 95% confidence interval [CI] 1.18 to 3.11, p = 0.001), 120 days (adjusted OR 1.97, 95% CI 1.01 to 3.85, p = 0.05), and 180 days (adjusted OR 2.04, 95% CI 1.01 to 4.15, p = 0.05). Using meta-regression analysis, it was found that only history of VA was a risk factor for mortality after LVAD implantation. In conclusion, post-LVAD VA is associated with an increased risk of all-cause mortality with pre-LVAD VAs acting as a risk factor. This meta-analysis, despite being only hypothesis generating, sets the stage for prospective collection of VA information in a prospective device trial or in the Interagency Registry for Mechanically Assisted Circulatory Support.

Ventricular assist devices in heart failure: how to support the heart but prevent atrophy?

Ventricular assist devices (VAD) have recently established themselves as an irreplaceable therapeutic modality of terminal heart failure. Because of the worldwide shortage of donors, ventricular assist devices play a key role in modern heart failure therapy. Some clinical data have revealed the possibility of cardiac recovery during VAD application. On the other hand, both clinical and experimental studies indicate the risk of the cardiac atrophy development, especially after prolonged mechanical unloading. Little is known about the specific mechanisms governing the unloading-induced cardiac atrophy and about the exact ultrastructural changes in cardiomyocytes, and even less is known about the ways in which possible therapeutical interventions may affect heart atrophy. One aim of this review was to present important aspects of the development of VAD-related cardiac atrophy in humans and we also review the most significant observations linking clinical data and those derived from studies using experimental models. The focus of this article was to review current methods applied to alleviate cardiac atrophy which follows mechanical unloading of the heart. Out of many pharmacological agents studied, only the selective beta2 agonist clenbuterol has been proved to have a significantly beneficial effect on unloading-induced atrophy. Mechanical means of atrophy alleviation also seem to be effective and promising.

Molecular changes after left ventricular assist device support for heart failure

Heart failure is associated with remodeling that consists of adverse cellular, structural, and functional changes in the myocardium. Until recently, this was thought to be unidirectional, progressive, and irreversible. However, irreversibility has been shown to be incorrect because complete or partial reversal can occur that can be marked after myocardial unloading with a left ventricular assist device (LVAD). Patients with chronic advanced heart failure can show near-normalization of nearly all structural abnormalities of the myocardium or reverse remodeling after LVAD support. However, reverse remodeling does not always equate with clinical recovery. The molecular changes occurring after LVAD support are reviewed, both those demonstrated with LVAD unloading alone in patients bridged to transplantation and those occurring in the myocardium of patients who have recovered enough myocardial function to have the device removed. Reverse remodeling may be attributable to a reversal of the pathological mechanisms that occur in remodeling or the generation of new pathways. A reduction in cell size occurs after LVAD unloading, which does not necessarily correlate with improved cardiac function. However, some of the changes in both the cardiac myocyte and the matrix after LVAD support are specific to myocardial recovery. In the myocyte, increases in the cytoskeletal proteins and improvements in the Ca²⁺ handling pathway seem to be specifically associated with myocardial recovery. Changes in the matrix are complex, but excessive scarring appears to limit the ability for recovery, and the degree of fibrosis in the myocardium at the time of implantation may predict the ability to recover.

Continuous monitoring of cardiac rhythms in left ventricular assist device patients

Monitoring of cardiac rhythms is of major importance in the treatment of heart failure patients with left ventricular assist devices (LVADs) implanted. A continuous surveillance of these rhythms could improve out-of-hospital care in these patients. The aim of this study was to investigate cardiac rhythms using available pump data only. Datasets (n = 141) obtained in the normal ward, in the intensive care unit, and during bicycle ergometry were analyzed in 11 recipients of a continuous flow LVAD (59.1 ± 9.7 years; male 82%). Tachograms and arrhythmic patterns derived from the pump flow waveform, and a simultaneously recorded ECG were compared, as well as heart rate variability parameters such as: the average heart beat duration (RR interval), the standard deviation of the beat duration (SDNN), the root-mean-square of the difference of successive beat durations (RMSSD), and the number of pairs of adjacent beat duration differing by >50 ms divided by the number of all beats (pNN50). A very good agreement of cardiac rhythm parameters from the pump flow compared with ECG was found. Tachycardia, atrial fibrillation, and extrasystoles could be accurately identified from the tachograms derived from the pump flow. Also, Bland-Altman analysis comparing pump flow with ECG indicated a very small difference in average RR interval of 0.3 ± 1.0 ms, in SSDN of 0.5 ± 2.7 ms, in RMSSD of 1.0 ± 5.6 ms, and in pNN50 of 0.3 ± 1.0%. Continuous monitoring of cardiac rhythms from available pump data is possible. It has the potential to reduce the out-of-hospital diagnostic burden and to permit a more efficient adjustment of the level of mechanical support.

Magnitude and time course of changes induced by continuous-flow left ventricular assist device unloading in chronic heart failure: insights into cardiac recovery

OBJECTIVES

This study sought to prospectively investigate the longitudinal effects of continuous-flow left ventricular assist device (LVAD) unloading on myocardial structure and systolic and diastolic function.

BACKGROUND

The magnitude, timeline, and sustainability of changes induced by continuous-flow LVAD on the structure and function of the failing human heart are unknown.

METHODS

Eighty consecutive patients with clinical characteristics consistent with chronic heart failure requiring implantation of a continuous-flow LVAD were prospectively enrolled. Serial echocardiograms (at 1, 2, 3, 4, 6, 9, and 12 months) and right heart catheterizations were performed after LVAD implant. Cardiac recovery was assessed on the basis of improvement in systolic and diastolic function indices on echocardiography that were sustained during LVAD turn-down studies.

RESULTS

After 6 months of LVAD unloading, 34% of patients had a relative LV ejection fraction increase above 50% and 19% of patients, both ischemic and nonischemic, achieved an LV ejection fraction ≥ 40%. LV systolic function improved as early as 30 days, the greatest degree of improvement was achieved by 6 months of mechanical unloading and persisted over the 1-year follow up. LV diastolic function parameters also improved as early as 30 days after LVAD unloading, and this improvement persisted over time. LV end-diastolic and end-systolic volumes decreased as early as 30 days after LVAD unloading (113 vs. 77 ml/m(2), p < 0.01, and 92 vs. 60 ml/m(2), p < 0.01, respectively). LV mass decreased as early as 30 days after LVAD unloading (114 vs. 95 g/m(2), p < 0.05) and continued to do so over the 1-year follow-up but did not reach values below the normal reference range, suggesting no atrophic remodeling after prolonged LVAD unloading.

CONCLUSIONS

Continuous-flow LVAD unloading induced in a subset of patients, both ischemic and nonischemic, early improvement in myocardial structure and systolic and diastolic function that was largely completed within 6 months, with no evidence of subsequent regression.

Bridge to recovery: what remains to be discovered?

The use of left ventricular assist devices to induce substantial myocardial recovery with explantation of the device, bridge to recovery (BTR), is an exciting but currently grossly underused application. Recently acquired knowledge relating to BTR and its mechanisms offers unprecedented opportunities to streamline its use and unravel some of the secrets of heart failure with much wider implications. This article reviews the status, challenges, and future of cardiac recovery.

Ventricular assist devices: pharmacological aspects of a mechanical therapy

Heart failure (HF) is a global epidemic that continues to cause significant morbidity and mortality despite advances in medical therapy. Ventricular assist device technology has emerged as a therapeutic option to bridge patients with end-stage HF to heart transplantation or as an alternative to transplantation in selected patients. In some patients, mechanical unloading induced by ventricular assist devices leads to improvement of myocardial function and a possibility of device removal. The implementation of this advanced technology requires multiple pharmacological interventions, both in the perioperative and long-term periods, in order to minimize potential complications and improve patient outcomes. We herein review the latest available evidence supporting the use of specific pharmacological interventions and current practices in the care of these patients: anticoagulation, bleeding management, pump thrombosis, infections, arrhythmias, right ventricular failure, hypertension, desensitization protocols, among others. Areas of uncertainty and ground for future research are also highlighted.

Left ventricular assist device unloading effects on myocardial structure and function: current status of the field and call for action

PURPOSE OF REVIEW

Myocardial remodeling driven by excess pressure and volume load is believed to be responsible for the vicious cycle of progressive myocardial dysfunction in chronic heart failure. Left ventricular assist devices (LVADs), by providing significant volume and pressure unloading, allow a reversal of stress-related compensatory responses of the overloaded myocardium. Herein, we summarize and integrate insights from studies which investigated how LVAD unloading influences the structure and function of the failing human heart.

RECENT FINDINGS

Recent investigations have described the impact of LVAD unloading on key structural features of cardiac remodeling - cardiomyocyte hypertrophy, fibrosis, microvasculature changes, adrenergic pathways and sympathetic innervation. The effects of LVAD unloading on myocardial function, electrophysiologic properties and arrhythmias have also been generating significant interest. We also review information describing the extent and sustainability of the LVAD-induced myocardial recovery, the important advances in understanding of the pathophysiology of heart failure derived from such studies, and the implications of these findings for the development of new therapeutic strategies. Special emphasis is given to the great variety of fundamental questions at the basic, translational and clinical levels that remain unanswered and to specific investigational strategies aimed at advancing the field.

SUMMARY

Structural and functional reverse remodeling associated with LVADs continues to inspire innovative research. The ultimate goal of these investigations is to achieve sustained recovery of the failing human heart.