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Simulation of dilated heart failure with continuous flow circulatory support.

ABSTRACT: Lumped parameter models have been employed for decades to simulate important hemodynamic couplings between a left ventricular assist device (LVAD) and the native circulation. However, these studies seldom consider the pathological descending limb of the Frank-Starling response of the overloaded ventricle. This study introduces a dilated heart failure model featuring a unimodal end systolic pressure-volume relationship (ESPVR) to address this critical shortcoming. The resulting hemodynamic response to mechanical circulatory support are illustrated through numerical simulations of a rotodynamic, continuous flow ventricular assist device (cfVAD) coupled to systemic and pulmonary circulations with baroreflex control. The model further incorporated septal interaction to capture the influence of left ventricular (LV) unloading on right ventricular function. Four heart failure conditions were simulated (LV and bi-ventricular failure with/without pulmonary hypertension) in addition to normal baseline. Several metrics of LV function, including cardiac output and stroke work, exhibited a unimodal response whereby initial unloading improved function, and further unloading depleted preload reserve thereby reducing ventricular output. The concept of extremal loading was introduced to reflect the loading condition in which the intrinsic LV stroke work is maximized. Simulation of bi-ventricular failure with pulmonary hypertension revealed inadequacy of LV support alone. These simulations motivate the implementation of an extremum tracking feedback controller to potentially optimize ventricular recovery.

SUBMITTER: Wang Y

PROVIDER: S-EPMC3894974 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundHeart failure (HF) is characterized by perturbations in energy homeostasis and metabolism. The reversibility and prognostic value of circulating markers associated with these changes remain unclear.ObjectivesThis study sought to describe the metabolomic profiles of patients along the spectrum of systolic HF, determine their association with adverse outcomes in a clinical trial of HF, and evaluate whether identified metabolites change with treatment for end-stage systolic HF.MethodsTo assess association of metabolites with clinical outcomes, we evaluated a population of 453 chronic systolic HF patients who had been randomized to exercise training versus usual care. To assess change in metabolites with mechanical circulatory support, 41 patients with end-stage HF who underwent left ventricular assist device (LVAD) placement were studied. Targeted, quantitative profiling of 60 metabolites using tandem flow injection mass spectrometry was performed on frozen plasma samples obtained prior to randomization, as well as prior to and ≥90 days post-placement in the LVAD group. Principal components analysis was used for data reduction.ResultsFive principal components analysis-derived factors were significantly associated with peak Vo2 levels at baseline in fully adjusted models. Of these, factor 5 (composed of long-chain acylcarnitines) was associated with increased risk of all 3 pre-specified clinical trial outcomes: all-cause mortality/all-cause hospitalization, all cause-hospitalization, and cardiovascular death or cardiovascular hospitalization. Individual components of factor 5 were significantly higher in patients with end-stage HF prior to LVAD placement and decreased significantly post-implantation.ConclusionsIn chronic HF patients, circulating long-chain acylcarnitine metabolite levels were independently associated with adverse clinical outcomes and decreased after long-term mechanical circulatory support. These metabolites may serve as potential targets for new diagnostics or therapeutic interventions. (Exercise Training Program to Improve Clinical Outcomes in Individuals With Congestive Heart Failure; NCT00047437).

Project description:ImportanceGiven the shortage of donor hearts and improvement in outcomes with left ventricular assist device (LVAD) therapy, a relevant but, to date, unanswered question is whether select patients with advanced heart failure should receive LVAD destination therapy as an alternative to heart transplant.ObjectiveTo determine whether a strategy of LVAD destination therapy is associated with similar survival benefit as wait-listing for heart transplant with or without LVAD therapy among patients with advanced heart failure.Design, setting, and participantsThis retrospective propensity-matched cohort analysis used data on heart transplants from the United Network for Organ Sharing registry and LVAD implants from the Interagency Registry for Mechanically Assisted Circulatory Support from January 1, 2010, to December 31, 2014. The matched LVAD destination therapy cohort included 3411 patients. Data analysis for this study was conducted from December 22, 2017, to May 24, 2019.Main outcomes and measuresSurvival at 5 years was analyzed using Cox proportional hazards models.ResultsIn total, 8281 patients had albumin level, creatinine level, and BMI data recorded and were included in the analysis. Despite propensity score matching, the 3411 patients receiving LVAD destination therapy still tended to be slightly older than the 3411 patients wait-listed for heart transplant (64.0 years [interquartile range, 55.0-70.0 years] vs 60.0 [interquartile range, 54.0-65.0 years]; P < .001), but there was no significant difference in sex (2701 men [79.2%] vs 2648 men [77.6%]; P = .13). After propensity score matching for age, sex, body mass index, renal function, and albumin level, 3411 patients were wait-listed for heart transplant. This included 1607 patients with bridge to transplant LVAD therapy and 1804 patients without LVAD. The strategy of wait-listing for heart transplant was associated with better 5-year survival than LVAD destination therapy (risk ratio, 0.42; 95% CI, 0.38-0.46) after matching and adjusting for key clinical factors. This survival advantage was associated with heart transplant (adjusted risk ratio for time-dependent transplant status, 0.27; 95% CI, 0.24-0.32).Conclusions and relevanceThe present analysis suggests that heart transplant with or without bridge to transplant LVAD therapy was associated with superior 5-year survival compared with LVAD destination therapy among patients matched on several relevant clinical factors. Continued improvement in LVAD technology, along with prospective comparative research, appears to be needed to amend this strategy.

Project description:BackgroundThe outlook for ambulatory patients with advanced heart failure (HF) and the appropriate timing for left ventricular assist device (LVAD) or transplant remain uncertain. The aim of this study was to better understand disease trajectory and rates of progression to subsequent LVAD therapy and transplant in ambulatory advanced HF.MethodsPatients with advanced HF who were New York Heart Association (NYHA) Class III or IV and Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) Profiles 4 to 7, despite optimal medical therapy (without inotropic therapy), were enrolled across 11 centers and followed for the end-points of survival, transplantation, LVAD placement, and health-related quality of life. A secondary intention-to-treat survival analysis compared outcomes for MedaMACS patients with a matched group of Profile 4 to 7 patients with LVADs from the INTERMACS registry.ResultsBetween May 2013 and October 2015, 161 patients were enrolled with INTERMACS Profiles 4 (12%), 5 (32%), 6 (49%), and 7 (7%). By 2 years after enrollment, 75 (47%) patients had reached a primary end-point with 39 (24%) deaths, 17 (11%) undergoing LVAD implantation, and 19 (12%) receiving a transplant. Compared with 1,753 patients with Profiles 4 to 7 receiving LVAD therapy, there was no overall difference in intention-to-treat survival between medical and LVAD therapy, but survival with LVAD therapy was superior to medical therapy among Profile 4 and 5 patients (p = 0.0092). Baseline health-related quality of life was lower among patients receiving a LVAD than those enrolled on continuing oral medical therapy, but increased after 1 year for survivors in both cohorts.ConclusionsAmbulatory patients with advanced HF are at high risk for poor outcomes, with only 53% alive on medical therapy after 2 years of follow-up. Survival was similar for medical and LVAD therapy in the overall cohort, which included the lower severity Profiles 6 and 7, but survival was better with LVAD therapy among patients in Profiles 4 and 5. Given the poor outcomes in this group of advanced HF patients, timely consideration of transplant and LVAD is of critical importance.

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Simulation of dilated heart failure with continuous flow circulatory support.

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