Short-term mechanical circulatory support as bridge to heart transplantation: paracorporeal ventricular assist device as alternative to extracorporeal life support

Optimizing the design of axial flow pump blades based on fluid characteristics

Non-physiological blood flow conditions in axial blood pumps lead to some complications, including hemolysis, platelet activation, thrombosis, and embolism. The high speed of the axial blood pump destroys large amounts of erythrocytes, thereby causing hemolysis and thrombosis. Thus, this study aims to reduce the vortices and reflux in the flow field by optimizing the axial blood pump. The axial blood pump and arterial flow field were modeled by the finite element method. The blood was assumed to be incompressible, turbulent, and Newtonian. The SST k-ω turbulence model was used. The frozen rotor method was also used to calculate the snapshot of motion. Many vortices and reflux exist in the flow field of the blood pump without optimization. The improved flow field had almost no vortex and reflux, thereby reducing the exposure time of blood. The optimized blood pump had little influence on the pressure field and shear stress field. The optimized blood pump mainly reduced the vortex, reflux, and the risk of thrombosis in the flow field. The flow field characteristics of an axial blood pump were studied, and the results showed the risk of thrombosis and hemolysis in the blood pump. In accordance with the relationship between the blade shape and the flow field, the blade of the blood pump was optimized, reducing the vortex and reflux of the flow field, as well as the risk of thrombosis.

Left Ventricular Unloading in Acute on Chronic Heart Failure: From Statements to Clinical Practice

Cardiogenic shock remains a deadly complication of acute on chronic decompensated heart failure (ADHF-CS). Despite its increasing prevalence, it is incompletely understood and therefore often misdiagnosed in the early phase. Precise diagnosis of the underlying cause of CS is fundamental for undertaking the correct therapeutic strategy. Temporary mechanical circulatory support (tMCS) is the mainstay of management: identifying and selecting optimal patients through understanding of the hemodynamics and a prompt profiling and timing, is key for success. A recent statement from the American Heart Association provided pragmatic suggestions on tMCS device selection, escalation, and weaning strategies. However, several areas of uncertainty still remain in clinical practice. Accordingly, we present an overview of the main pitfalls that can occur during patients' management with tMCS through a clinical case. This case illustrates the strict interdependency between left ventricular unloading and right ventricular dysfunction in the case of low filling pressures. Moreover, it further illustrates the pivotal role of stepwise escalation of therapy in a patient with an ADHF-CS and its peculiarities as compared to other forms of acute heart failure.

Effects of Levosimendan on Systemic Perfusion in Patients with Low Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) Score: Experience from a Single Center in Taiwan

Background

Patients with cardiogenic shock have a high risk of mortality. Intravenous levosimendan can provide pharmacologic inotrope support.

Objectives

We aimed to investigate the effect of levosimendan in patients with extremely severe cardiogenic shock and low Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) score with or without mechanical circulatory support.

Methods

From January 2017 to May 2019, 24 patients with INTERMACS 1-4 were enrolled in this retrospective study. All patients had systemic malperfusion and were treated with levosimendan. Biochemistry data related to systemic perfusion were recorded and compared before and at 24 and 72 hours after levosimendan administration. Echocardiography and Kansas City Cardiomyopathy Questionnaire (KCCQ) were completed 2 months later to assess left ventricular ejection fraction (LVEF) and quality of life (QoL), respectively.

Results

Arterial pressure and heart rate did not significantly differ before and after levosimendan administration. Atrial fibrillation and ventricular premature complex increased without significance. The dose of inotropes could be significantly tapered down. There were no significant differences in blood urea nitrogen, creatinine, and lactate levels. Urine output significantly increased (p = 0.018), and liver-related enzymes improved but without significance. B-type natriuretic peptide significantly decreased (p = 0.007) at 24 hours after levosimendan administration. Echocardiography showed significantly improved LVEF 2 months later (22.43 ± 8.13% to 35.87 ± 13.4%, p = 0.001). KCCQ showed significantly improved physical activity and greater relief of symptoms (p = 0.003). The survival-to-discharge rate was 75%.

Conclusions

We observed a decrease in B-type natriuretic peptide, better urine output, and alleviated hepatic injury in the levosimendan group. Most patients who survived without transplantation had significantly improved LVEF and better QoL after levosimendan administration.

Risk of Thrombus Formation in Patients on Mechanical Circulatory Support with POLVAD-MEV

BACKGROUND Congestive heart failure is a challenging problem due to increasing prevalence in developed countries. Patients admitted due to decompensated congestive heart failure symptoms who do not respond to medical treatment require mechanical circulatory support. Patients with biventricular failure are at particularly high mortality risk. MATERIAL AND METHODS We analyzed the function of 49 pumps (POLVAD-MEV, FRK Intra-cordis, Poland) implanted to rescue INTERMACS 1 and 2 profile patients referred to our department due to severe congestive heart failure. All patients were waiting for heart transplantation and were readmitted due to acute decompensations of congestive biventricular heart failure with resistance to medical therapy. RESULTS During the observational period, there were no technical problems in pump function. The mean duration of pump therapy was 30.6±8.3 (5-49) days. The risk for right-sided pump complications included clots formation on the following parts of the pump: outflow tract (1, 2%), membrane (13, 27%), dome (6, 12.5%), and periphery (1, 2%). The overall risk for device thrombosis was 41%. The risk for thromboembolic complications was CRP-dependent regarding conglomerates of fibrin and platelets formation (p<0.05). The risk for left-sided pump complications included clots formation on the outflow tract (1, 2%), membrane (9, 19%) and dome (3, 6%). The overall risk for device thrombosis was 27%. The risk for clots formation on the membrane (P<0.05) and dome of the pump depended on time (P<0.07). CONCLUSIONS Mechanical circulatory support with a paracorporeal pump is a safe option for biventricular heart dysfunction as a bridge to heart transplantation. The risk for thrombi formation is relatively high but acceptable within 30 days after implantation.

Impact of bridge-to-bridge strategies from paracorporeal to implantable left ventricular assist devices on the pre-heart transplant outcome: A single-center analysis of 134 cases

BACKGROUND

In Japan, patients with heart failure who have a paracorporeal left ventricular assist device (pLVAD) and cannot be weaned from the VAD may undergo conversion to implantable continuous-flow LVAD (iLVAD) via a bridge-to-bridge (BTB) strategy for bridge-to-transplantation (BTT). This study aimed to evaluate the real-world clinical status of BTB strategies.

METHODS

Among 134 patients who underwent iLVAD implantation for BTT, 34 patients underwent conversion from pLVAD to iLVAD (BTB group) and 100 patients underwent iLVAD implantation primarily (primary iLVAD group). The clinical characteristics and outcomes were compared between the two groups.

RESULTS

No significant difference was found in the overall survival between the two groups (p = 0.26; log-rank test). However, the 1-year survival rate and the 1-year freedom from the composite events of death, stroke, systemic infection, and bleeding rate were lower in the BTB group than in the primary iLVAD group (survival rate, 88.2% vs. 99.0%, p = 0.0040; composite event-free survival rate, 26.1% vs. 49.8%, p = 0.030; log-rank test). Multivariate analysis indicated that the BTB strategy [hazard ratio (HR) 1.70, 95% confidence intervals (CI) 1.03-2.72; p=0.036] and serum total bilirubin levels at iLVAD implantation [HR 1.31, 95% CI 1.00-1.65; p=0.043] were independent predictors of 1-year composite events.

CONCLUSIONS

The BTB strategy is useful in providing long-term survival in patients with acute critical diseases. However, the early mortality rate after conversion is higher in patients who underwent the BTB strategy.

Bridge to heart transplantation in patients with cardiogenic shock: a 20-year experience with two different surgical strategies

AIMS

We aimed to describe how treatment of patients in cardiogenic shock bridged to heart transplantation with mechanical circulatory support, using either biventricular assist devices (BVADs) or extracorporeal life support (ECLS), has evolved in the last 20 years in our centre.

METHODS

Since 1998, 72 patients with refractory heart failure and indication for heart transplantation have received mechanical circulatory support: 40 had an ECLS system and 32 a BVAD.

RESULTS

Early mortality was similar (17.5 vs. 9.4%, P = 0.25) regardless of the type of support. After a median support time of 8 (1-27) vs. 34 (0-385) days (P < 0.01), 70 vs. 65.6% (P = 0.69) of patients underwent transplantation in the two groups. Prior to transplantation, BVAD patients were more stable with lower need for mechanical ventilation (9 vs. 57%, P < 0.01) and dialysis (0 vs. 38%, P < 0.01). Thirty-day mortality after transplantation was similar (18 vs. 14%, P = 0.53). Patients with extracorporeal support had higher rates of renal (P = 0.02) and respiratory failure (P = 0.03), infections (P = 0.02), atrial fibrillation (P = 0.03) and longer ICU stay (P = 0.01). Late survival was similar, while 5-year freedom from coronary vasculopathy was higher in those with BVAD (P = 0.03).

CONCLUSION

Although ECLS provides faster and simpler assistance compared with BVADs, no differences in early and medium-term outcomes in the last 20 years were observed in patients with cardiogenic shock. However, BVADs provided longer duration of support, better multiorgan recovery allowing more adequate graft selection, resulting in a lower rate of posttransplant complications.

Comparison of SynCardia total artificial heart and HeartWare HVAD biventricular support for management of biventricular heart failure: a systematic review and meta-analysis

BACKGROUND

The aim of this study was to compare the outcomes of patients undergoing SynCardia total artificial heart (TAH) and biventricular HeartWare ventricular assist device (Bi-HVAD) support for biventricular heart failure (HF).

METHODS

Electronic search was performed to identify all relevant studies detailing patients who underwent biventricular assist device implantation using Bi-HVAD devices and those who underwent TAH placement for biventricular HF. Twelve studies including 512 patients in the TAH group versus 38 patients in the Bi-HVAD group were pooled for meta-analysis.

RESULTS

Ischemic cardiac etiology was present in 32% (95% CI, 24-47) of TAH vs. 15% (95% CI, 4-44) of Bi-HVAD patients (P=0.21). There was a comparable incidence of stroke [TAH 11% (95% CI, 7-16) vs. Bi-HVAD 13% (95% CI, 2-51), P=0.86] and acute kidney injury [TAH 28% (95% CI, 2-89) vs. Bi-HVAD 27% (95% CI, 9-59), P=0.98]. Overall infection rate was 67% (95% CI, 47-82) in TAH and 36% (95% CI, 10-74) in Bi-HVAD (P=0.16). Driveline infections were comparable between the two groups [TAH 11% (95% CI, 6-19) vs. Bi-HVAD 8% (95% CI, 1-39), P=0.73] and although a higher incidence of mediastinitis was found in the Bi-HVAD group [TAH 4% (95% CI, 2-7) vs. Bi-HVAD 15% (95% CI, 4-45), P=0.07] there was no statistically significant difference between the groups. Postoperative bleeding was present in 42% (95% CI, 28-58) of TAH vs. 23% (95% CI, 8-52) of Bi-HVAD (P=0.22). Patients in the TAH group had shorter duration of support [TAH 71 days (95% CI, 15-127) vs. Bi-HVAD 167 days (95% CI, 116-217), P=0.01]. At the mean follow-up time of 120 days, (95% CI, 83-157) patients in both groups had similar overall mortality [TAH 36% (95% CI, 22-49) vs. Bi-HVAD 26% (95% CI, 6-46), P=0.44] including mortality on device support [TAH 26% (95% CI, 17-36) vs. Bi-HVAD 21% (95% CI, 4-37), P=0.55]. Discharge home on support was achieved in 6% (95% CI, 4-17%) of TAH patients vs. 73% (95% CI, 48-89%) of Bi-HVAD (P<0.01), and 68% (95% CI, 52-84) of TAH patients were transplanted vs. 61% (95% CI, 47-75) in the Bi-HVAD group (P=0.14).

CONCLUSIONS

Patients on Bi-HVAD support were more likely to be able to be discharged home on support and had similar overall mortality to TAH, albeit with much longer duration of support.

Clinical outcome of donor heart with prolonged cold ischemic time: A single-center study

OBJECTIVES

Due to the shortage of donor pool, there has been a need for organs with prolonged cold ischemic time. This study aims to evaluate the short-term results of different cold ischemic times in orthotopic heart transplantation based on a single-center experience in China.

METHODS

We retrospectively analyzed outcomes of the heart transplant patients from 1 January 2015 to 31 December 2017. The recipient population was divided into four groups. Group 1: cold ischemic time greater than 8 hours; group 2: the cold ischemic time between 6 and 8 hours; group 3: the cold ischemic time between 4 and 6 hours; and group 4: cold ischemic time less than 4 hours. Efficacy indicators included after transplant survival, infection rate, rejection rate, and complications.

RESULTS

The four groups have similar donor and recipient baseline characteristics (P > .05). Cold ischemic time greater than 8 hours had more cardiopulmonary bypass (CPB) time (127.62 ± 50.23 minutes; P = .003), CPB-assist time (86.14 ± 36.74 minutes; P = .047), and higher intra-aortic balloon pump (IABP) usage rate postoperatively (47.36%; P = .010). Cold ischemic time greater than 8 hours witnessed a relatively higher mortality rate compared with the other three groups (P = .115, P =  .078, and P =  .114) during the 2-year follow-up. Survival rates of 1 and 2 years for the four groups were 78.95%, 87.13%, 87.32%, and 87.50% and 68.42%, 85.14%, 85.92%, and 83.93%, respectively.

CONCLUSION

Cold ischemic time less than 8 hours can be reasonably applied to expand the heart transplantation donor pool. Cold ischemic time greater than 8 hours might result in longer CPB time, CPB-assist time, and higher IABP usage postoperatively. It might also affect the in-hospital and 2-years survival rate.