Exercise capacity in patients implanted with left ventricular assist devices for end-stage heart failure treatment

Funding Acknowledgements

Type of funding sources: None.

Introduction

Left ventricular assist device (LVAD) is an expanding therapy in end-stage heart failure today. Although LVAD therapy bears the potential to normalize cardiac output, a majority of patients show a severely impaired physical condition at the time of LVAD implantation. To date, no validated standardized training protocol is available, and established practices to effectively improve LVAD patients’ exercise tolerance is lacking. This study sought to investigate exercise capacity quantified by cardiopulmonary exercise testing (CPX) and a standardized six-minute walk test (6MWT) in patients after LVAD implantation.

Methods

We enrolled 30 end-stage heart failure patients who had received an LVAD implantation 20.7 ± 7.6 days prior to examination, mean age 54.9 ± 7.8 years, 26 males (87 %). Exercise tolerance was assessed using cardiopulmonary exercise testing (CPX) for maximal and submaximal exercise capacity, followed by a standardized (6MWT).

Results

Patients showed peak oxygen uptake values of 8.3 ± 2.4 ml/min/kg at a mean workload of 46.7 ± 11.3 watts and a mean anaerobic threshold of 6.7 ± 1.7 ml/min/kg at a workload of 32.6 ± 6.9 watts. Mean standardized 6-minute walking distance was at 183.8 ± 71.4 meters. There were no adverse events during exercise testing.

Conclusions

Cardiopulmonary exercise testing (CPX) and standardized 6MWT show severely impaired cardiopulmonary exercise capacity in patients after LVAD implantation, warranting further studies for dedicated training protocols, specifically focusing on LVAD patients to improve exercise tolerance at an acceptable safety profile.

P820 Echocardiographic assessment of late-onset right ventricular dysfunction following continuous-flow left ventricular assist device

Methods and results

We retrospectively analyzed the 1-year hemodynamic and clinical data from patients (p) that, between 2016 and 2018, underwent a right heart catheterization (RHC) after LVAD as bridge to transplantation (BTT). 73 p (84% males, 52 ± 12 years, 49% Heart Ware LVAD, 51% Heart Mate 3 LVAD), out of 187 LVAD implants, were studied. According to the Intermacs definition, LoRVF was assigned if the RHC showed a central venous pressure (CVP)>18 mmHg with cardiac index< 2.3 L/min/m2. Isolated LoRVF was assigned if LoRVF was present in the absence of elevated pulmonary capillary wedge pressure (PCWP) ≤15 mmHg. TTE was performed at the time of the RHC and the following parameters were obtained: parasternal long-axis left ventricular end diastolic diameter (LVEDD), basal (RVED1) and mid-cavity (EDRV2) end diastolic RV linear dimension in 4 chamber view, severity of tricuspid regurgitation (TR) and of mitral regurgitation (MR), tricuspid annular plane systolic excursion (TAPSE), and the position of the LVAD inflow cannula (IC).

LoRVF was present in 16 p (22% of the studied population): 12 p (75%) presented a PCWP > 15 mmHg and 4 p (25%) presented isolated LoRVF. Symptoms and signs of venous congestion were present in 2/3 of the p with LoRVF and elevated PCWP. On the other hand, all the p with isolated LoRVF presented severe signs of venous congestion, and 50% of them could be successfully transplanted in high urgent status. P with LoRVF showed more dilated RV (RVED1 43.8 ± 9.2 vs 37.7 ± 5.3 mm, p = 0.02) and lower TAPSE (11 ± 2 vs 14 ± 2 mm p < 0.01) than the no LoRVF group. RVED1 showed a weak significant correlation with CVP (R = 0.3, p = 0.02). On the other hand, the presence of an elevated PCWP was not related to etiology of the cardiomyopathy, type and speed of LVAD, position of the IC, LVEDD, nor the presence of MR > mild.

Conclusion

LoRVF is a frequent complication during LVAD support as BTT and most of the cases are associated with persistent elevated PCWP. Isolated LoRVF, which is not associated with high PCWP, has a bad prognosis. RV evaluation with TTE during the clinical follow-up can be useful to detect LoRVF. However a persistent elevated PCWP is not associated with echocardiographic signs of incomplete unloading of the LV by the LVAD.

P1670Incidence and prognosis of late-onset right ventricular failure following continuous-flow left ventricular assist device implantation as bridge to transplantation

Methods and results

We retrospectively analysed the 1-year hemodynamic and clinical data from all patients that, between 2016 and 2018, underwent a right heart catheterization (RHC) after continuous-flow LVAD implantation as bridge to transplantation. Sixty-six patients (84% males, 53±11 years, 60% implanted in Intermacs 1–2, 52% HeartWare LVAD, 48% HM3 LVAD), out of 187 LVAD implants, were studied. LoRVF was defined as central venous pressure>18 mmHg with cardiac index<2.3 L/min/m2 during RHC.

LoRVF was present in 17 patients (25.7%) and 12 (71%) of them manifested concomitant clinical signs of RVF. Eleven of the patients who presented LoRVF (65% of the LoRVF) had a pulmonary capillary wedge pressure (PCWP)>15 mmHg. Isolated LoRVF (LoRVF criteria + PCWP≤15 mmhg) was found in 6 patients (35% of the LoRVF) and accounted for 9% of the studied population. Fifty percent of patients who presented isolated LoRVF could be successfully transplanted in high urgent status due to severe chronic RVF and 1 patient died to refractory RVF. We did not find an association between isolated LoRVF and age, renal function, type of LVAD, persistent increased pulmonary vascular resistances or the previous need of temporary right ventricular support due to early acute RVF following LVAD. There was however a significant association between the presence of atrial fibrillation and isolated LoRVF (p<0.05).

Incidence and prognosis of LoRVF

Conclusion

Late-onset RVF is a frequent complication during LVAD support as bridge to transplantation. Most of the cases are associated to a lesser degree of left ventricular unloading. The presence of isolated late-onset RVF with normal PCWP has an impact on the long-term prognosis and the need of urgent heart transplantation and is not related to early RVF following LVAD implantation or persistent increased pulmonary vascular resistance.

Development and Initial in Vivo Testing of a New Hydraulic Drive System (Paedipump) for Circulatory Support in Infants

The main limitation in the use of circulatory support in children is the lack of an adequate system with regard to size and pumping capacity Recently, two pneumatically driven ventricular support systems with low volume chambers for use in a pediatric population became available. We have developed a hydraulic drive system with an advantageous exact control of the stroke volume. The system enables two different modes of operation: the full-empty and the filled-empty modes. In both cases the ventricle is empty at the end of systole.

This new system was tested in experimental animals (6 pigs, body weight 9.5–14.0 kg) with normal and reduced left ventricular function (MAP<45 mmHg). A 25 ml ventricle (HIA-Medos) was implanted. The full-empty and the filled-empty mode used led to a significant load reduction, both in animals with normal and impaired cardiac function. Plasma lactate levels, pH-values and total body 0 2 consumption were in the normal range during circulatory support indicating adequate organ perfusion.

Results showed that sufficient ventricular support was achieved during all pumping modes due to the possibility of controlling and modifying the stroke volume of the hydraulically driven support system employed according to necessity. This is a promising feature for its future application in infants with congenital or acquired heart diseases.

The MiniACcor: Constructive Redesign of an Implantable Total Artificial Heart, Initial Laboratory Testing and Further Steps

The Aachen Total Artificial Heart (ACcor) has been under development at the Helmholtz Institute in Aachen over the last decade. It may serve as a bridge to transplant or as a long-term replacement of the natural heart. Based upon previous in vivo experiments with the ACcor total artificial heart, it was decided to optimize and redesign the pump unit. Smaller dimensions, passive filling and separability into three components were the three main design goals. The new design is called the MiniACcor, which is about 20% smaller than its predecessor, and weighs only 470 grams. Also its external driver/control unit was miniaturized and a new microcontroller was selected. To validate the design, it was extensively tested in laboratory mock loops. The MiniACcor was able to pump between 4.5 and 7 l/min at different pump rates against normal physiological pressures. Several requirements for the future compliance chamber and transcutaneous energy transmission (TET) system were also measured in the same mock loop. Further optimization and validation are being performed in cooperation with the Heart and Diabetes Centre North Rhine-Westphalia.

Vitamin D metabolites and fibroblast growth factor-23 in patients with left ventricular assist device implants: association with stroke and mortality risk

PURPOSE

Stroke and mortality risk in patients with left ventricular assist device (LVAD) implants continue to be high. Whether nonclassical cardiovascular risk markers such as vitamin D metabolites and fibroblast growth factor (FGF)-23 contribute to this risk remains to be studied, and this was the objective of our work.

METHODS

In 154 LVAD patients (91 HeartWare and 63 HeartMate II implants), we measured circulating 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D3 (1,25[OH]2D3), parathyroid hormone (PTH) and FGF-23 shortly before LVAD implantation and investigated their association with stroke and mortality risk during 1-year follow-up.

RESULTS

Of the study cohort, 34.4 and 92.2%, respectively, had deficient 25OHD (<25 nmol/l) and 1,25(OH)2D3 (<41 pmol/l) values, whereas 42.6 and 98.7%, respectively, had elevated PTH levels (>6.7 pmol/l) and FGF-23 values above the reference range (100 RU/ml). One-year freedom from stroke was 80.9 %, and 1-year survival was 64.3%. The multivariable-adjusted hazard ratio of stroke was 2.44 (95% CI: 1.09-5.45; P = 0.03) for the subgroup of 25OHD levels <25 nmol/l (reference group: 25OHD levels ≥25 nmol/l). The multivariable-adjusted hazard ratio of 1-year mortality was 2.78 (95% CI: 1.52-5.09; P = 0.001) for patients with 25OHD levels <25 nmol/l compared with patients with 25OHD levels ≥25 nmol/l. PTH, FGF-23 and 1,25(OH)2D3 were not associated with stroke or mortality risk.

CONCLUSIONS

In LVAD patients, deficient 25OHD levels are independently associated with high stroke and mortality risk. If confirmed in randomized controlled trials, preoperative correction of deficient vitamin D status could be a promising measure to reduce stroke and mortality risk in LVAD patients.

[Heart and combined heart-lung transplantation. Indications, chances and risks]

Orthotopic heart transplantation (HTX) is nowadays the worldwide accepted gold standard for the treatment of terminal heart failure. The main indications for HTX are non-ischemic dilatative (54%) and ischemic (37%) heart failure. In the acute phase after HTX the survival rate is approximately 90%. Good short and long-term results with survival rates ranging from 81% after 1 year to more than 50% after 11 years demonstrate that there is currently no real treatment alternative to HTX for treatment of end-stage heart failure. In the case of irreversible pulmonary hypertension in combination with end-stage heart failure or complex congenital heart syndromes, a combined heart and lung transplantation (HLTX) is necessary. Compared with HTX the short-term survival of HLTX is reduced, mostly for technical reasons. Improved long-term results after HTX and HLTX are a result of highly specialized transplantation units and effective immunosuppression. However, a major problem is the shortage of organ donors in Germany and the resulting long waiting times for patients with frequently occurring blood groups of up to 10 months for transplantation. The consequence of the latter is the ever increasing number of implanted cardiac assist devices in patients not only as a bridge to transplant but also as destination therapy.