Evolution of renal function after partial and full mechanical support for chronic heart failure.

PURPOSE: Recently a minimal invasive, partial support continuous flow left ventricular assist device (LVAD) became available for treatment of chronic heart failure. The aim of this study was to analyze whether partial support is capable of improving kidney function in end-stage heart failure. METHODS: We performed a single-center retrospective analysis of patients how received a full (n = 43) or partial support LVAD (n = 18) between 2007 and 2013. Patients on dialysis or in INTERMACS class I were excluded. Renal function was assessed until 3 months after the implantation. A calculated GFR less than 60 m/min was considered to be renal failure. RESULTS: Creatinine level after LVAD implant decreased 23% in patients on full support (1.3 ± 0.4 mg/dl vs. 1.0 ± 0.3 mg/dl; p<0.001) and 24% in patients on partial support (1.6 ± 0.6 mg/dl vs. 1.2 ± 0.4 mg/dl; p = 0.17) within 3 months. In each group patients with a preoperative GFR less than 60 ml/min were selected. In this subgroup there was a 35% decrease in creatinine levels for patients on full support (1.7 ± 0.4 mg/dl vs. 1.1 ± 0.5 mg/dl; p<0.01) and a 32% decrease in patients on partial support (2 ± 0.4 mg/dl vs. 1.4 ± 0.3 mg/dl; p<0.05) at 3 months. CONCLUSIONS: We observed a significant improvement in renal function in patients supported by full or partial support devices, even if the preoperative renal function was severly impaired. The use of diuretics decreased in both groups. In chronic heart failure patients with impaired renal function, partial support is sufficient to improve renal function significantly.

Pediatric heart support with a newly developed catheter based pulsatile 12F rotary blood pump: an animal study.

BACKGROUND: To evaluate mechanical and hematological compatibility of a pediatric, temporary left heart support system in a lamb model as a less traumatic alternative to the widely used ECMO. METHODS: A small, pulsatile rotary blood pump (target flow 0.5l/m at 80 mm Hg pressure head at 120 pulses per min) was inserted in six lambs (15.1+/-1 kg) via a left thoracotomy, through a purse string in the arcus aortae. With fluoroscopy the tip (=inflow) of the catheter was positioned in the outflow tract of the left ventricle. The outflow part was positioned immediately above the aortic valve. Animals were extubated at the end of the procedure. Mechanical and hematological parameters were followed for 14 days. RESULTS: Five animals survived a 2-week follow-up. One animal died because of empyema on day 6. Flow maintained stable (0.8+/-0.2l/m) in all animals during the evaluation period. Free hemoglobin as a parameter of hemolysis and hematocrit remained also stable. Necropsy revealed minimal fibrous reaction on one aortic valve leaflet in one animal and small hematoma formation in three. All animals showed mild signs of endothelial damage on the aortic arch at the level of the motor housing. One animal showed signs of old kidney infarction suggesting possible embolization during placement. CONCLUSION: This newly developed, catheter based, pediatric heart support system generates a stable flow for 14 days without compromising hematological stability and with acceptable tissue damage due to positioning of the catheter.

Mechanical stress activates platelets at a subhemolysis level: an in vitro study.

A feasibility study is performed to quantify sheep platelets (PLTs) and to identify the relationship between PLT count and hemolysis as a consequence of mechanical stress. Six adult, healthy Dorset sheep have been used for in vitro blood sampling test procedures in a hemoresistometer device (HRM). In each experiment, blood of the same animal was exposed to six different shear rates. Free hemoglobin levels and PLT count for each shear rate were detected. In all animals (A-F), hemolysis increased significantly between the shear rates of 2325 and 3100/s (P < 0.05) and the mean PLT count dropped immediately (contact, low shear) 40% in the beginning, between the shear rates of 0 and 775/s (P < 0.05). PLT count increased slightly as soon as hemolysis started. At higher shear rates, hemolysis increased and PLTs reduced further. Precise counting of PLTs indicates that PLTs are consumed dramatically at very low shear (by contact) and further by applied mechanical stress when hemolysis is obvious. A repetition of these tests with human blood could indicate species differences.

pH 48 h after onset of extracorporeal membrane oxygenation is an independent predictor of survival in patients with respiratory failure.

Extracorporeal membrane oxygenation (ECMO) is a life-saving procedure in patients with severe respiratory failure, unresponsive to conventional therapy. We reviewed our series of 70 ECMO runs (April 1997 to December 2005) in patients with respiratory distress, refractory to standard ventilation. Survival at 90 days was 42.7%. Besides age, we found no statistical significant difference in patient demographics or preoperative patient data between survivors and nonsurvivors. Univariate analyses indicated that pH values at 24 and 48 h after onset of ECMO were significantly higher in survivors. In multivariate analysis, age and pH at 48 h remained independent predictors of survival. ECMO in respiratory failure saves lives. No other demographic or preoperative, patient-related parameter than age was identified as predictor of survival. Although there was no difference in pH at onset of ECMO, blood gas analysis at 48 h revealed pH as an independent predictor of survival.

Heparin influences human platelet behavior in cardiac surgery with or without cardiopulmonary bypass.

The objective was to investigate whether the platelet dysfunction in cardiac surgery is caused by hemodilution or by shear stress due to cardiopulmonary bypass (CPB). Platelet count and function were prospectively analyzed in two groups of patients undergoing cardiac surgery either with or without CPB (n = 40). In the first study (n = 20; 10 patients with and 10 without CPB), platelet counts were assessed at seven time points. In the second study (n = 20; 10 patients with and 10 without CPB), platelet function was studied with platelet aggregometry at different points during surgery: (a) after induction of anesthesia; (b) after sternotomy; and (c) 1 h after heparin. In the first study, the CPB group showed a significant decrease in platelet count starting after sternotomy (230 +/- 34 vs. 182 +/- 25, P < 0.05) and a maximum decrease at day 1 postoperative (96 +/- 34, P < 0.05). A similar observation was made in the non-CBP group. In the second study, a significant decrease of ADP (54 +/- 13% vs. 38 +/- 9%, P < 0.05), AA (76 +/- 16% vs. 22 +/- 14%, P < 0.05), and Collagen (66 +/- 13% vs. 37 +/- 11%, P < 0.05) induced platelet aggregation was observed at MOMENT d compared to the beginning of surgery in the CPB group. In the non-CBP group a significant decrease was observed in AA-induced platelet aggregation at MOMENT d (83% +/- 4 vs. 44% +/- 14, P < 0.05). The reduction in platelet count is similar with or without cardiopulmonary bypass and is due to pure hemodilution. Platelet function reduces significantly after heparin administration. Hemodilution and predominantly heparin are the causes of platelet dysfunction after cardiac surgery.

Design, development, and first in vivo results of an implantable ventricular assist device, MicroVad.

The design concept and first in vitro and in vivo results of a long-term implantable ventricular assist device system based on a microaxial blood pump are presented. The blood-immersed parts of the pump consist of a single-stage impeller and a proximally integrated microelectric motor. Both parts are surrounded by a pump housing currently made of polycarbonate to allow visible access to the blood-exposed parts. A titanium inflow cage attached to the tip of the housing is directly implanted into the left ventricular apex. The outflow of the pump is connected to the descending aorta by means of an e-PTFE graft. The overall dimensions of the device are 12 mm in outer diameter and about 50 mm in length. The calculated lifetime of the device is up to 2 years. The system underwent long-term durability tests, hydraulic performance tests, dynamic stability tests, and in vitro hemolysis and thrombogenicity tests. Furthermore, animal tests have been performed in adult Dorset sheep. In a first series, the pump has been placed extracorporeally; in a second series, the pump was completely implanted. Mean duration of the animal experiments of the second series was 31 days (range 8-110 days, n=14); no anticoagulation was administered over the whole test period. Blood data revealed no significant changes in blood cell counts, ionogram, or any other value. No end-organ dysfunction induced by long-term support could be observed, nor did the pathology reveal any evidence of thromboembolic complications.