We recruited 85 consecutive adult patients (over 18 years old) diagnosed with advanced heart failure, meeting at least one of the following inclusion criteria: a history of at least 3 hospitalizations due to HF decompensations in the preceding 12 months, dependence on inotropes or temporary mechanical circulatory support, progressive end-organ dysfunction attributed to the low cardiac output, very limited exercise capacity (VO2 peak < 12ml/kg/min), or an inability to exercise. Exclusion criteria encompassed current pregnancy, ongiong infections, recurrent malignant arrhythmias, severe right ventricular failure, phenotypes of hypertrophic or restrictive cardiomyopathy hindering safe LVAD implantation, known contraindications to antiplatelet or anticoagulation therapies, life-limiting severe comorbidities or cancer (with an expected survival of less than two years), severe renal or liver failure, absence of social support or unstable psychosocial background.
Implantation was performed either as a bridge to transplantation or bridge to candidacy. The study was conducted at a single high-volume heart transplantation center between May 10, 2017 and September 10, 2021. All patients provided informed consent before participation in and underwent assessment adhering to the inclusion and exclusion criteria preimplantation.
The study adheres to the principles of the Declaration of Helsinki and received approval from the Medical University of Silesia Bioethics Committee (PCN/CBN/0022/KB1/144/21/22).
Two available continuous-flow LVAD systems (HeartWare, Medtronic or HeartMate 3, Abbot) were used. The choice between two types and surgical approach (full sternotomy vs. mini- sternotomy) was at the operator’s discretion. Both devices had national health insurance approval at the time of implantation. Both pumps consisted of an inflow cannula inserted into the left ventricle connected to a continuous-flow centrifugal pump placed in the chest. The outflow cannula transported blood from the pump to the ascending aorta. Both pumps were externally powered, connected to an external energy source via the driveline tunneled in abdominal tissues and exiting on the skin surface. Pump flow was regulated by altering the rotation speed in the external controller 14. Pump speed adjustment was performed by an experienced transplant physician based on echocardiography and patient’ clinical condition 15.
Subsequent to acquiring informed consent for participation in the study, patients were regularly followed up at scheduled visits: prior to LVAD implantation, 3–4 months post-implantation, 6–12 months post-implantation, and thereafter every 6 months post the first year (for a maximum follow-up of 5 years). The last available blood sample was analyzed We (median 21 months; IQR:10–29 months).
The anticoagulation regimen comprised titrated warfarin (vitamin K antagonist) to achieve a target international normalized ratio (INR) of 2–3. Patients underwent INR home tests for all-day self-monitoring. In instances of vitamin K antagonist cessation, patients were bridged with therapeutic doses of low molecular weight or unfractionated heparin.
Acetylsalicylic acid at a daily dose of 75mg was the preferred an antiplatelet therapy. We monitored ASPI to assess aspirin response. If the ASPI test fell below 745AU × min, we maintained the dose; if it exceeded 745AU × min, we increased the dosage to 150 mg daily. Should ASPI test levels remain elevated, we switched antiplatelet medication to clopidogrel 75mg daily and monitored the response using ADP tests. If the ADP test resulted below 534 AU × min, we maintained the dosage; otherwise, we doubled the dosage. Detail of the anticoagulation and antiplatelet regimen are described elsewhere 16.
Heart failure guideline-directed medical therapy included angiotensin-convertingenzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), angiotensin receptor- neprilysin inhibitor (ARNI), mineralocorticoid receptor antagonists (MRA), sodium-glucose contransporter-2 (SGLT-2), beta-blockers, diuretics, and optionally, depending on etiology, statins. Comorbidities were managed based on individual indications.
Major adverse cardiac and cerebrovascular events (MACCE) encompassed all-cause mortality, ischemic stroke, transient ischemic attack, peripheral embolism, pulmonary embolism, and pump thrombosis. We documented all symptomatic events during follow-ups and outpatient visits. Bleeding complications were classified based on criteria established by the International Society on Thrombosis and Hemostasis 17.Net adverse clinical events (NACE) comprised a composite of MACCE and bleeding complications. Transplantations were calculated separately and were not included in MACCE or NACE assessments.
Laboratory investigations
Assessment timeline: Basic clinical and laboratory parameters were analyzed at four time points: directly before to LVAD implantation (T1), 3–4 months post-implantation (T2), 6–12 months post-implantation (T3), and the last available blood sample (T4). Fasting venous blood samples were collected between 7:30 and 09:00 AM. Routine laboratory tests were used to evaluate basic biochemical parameters and complete blood count.
Coagulation profile: Citrated venous blood samples were collected using S—Monovettes: Citrate 9NC/2.9 mL (9NC:0.106 mol/L) to assess Prothrombin Time, Activated Partial Thromboplastin Time, Fibrinogen, D-dimer, Antithrombin, Thrombin Time, Factor VIII, and von Willebrand Factor.
Assay Details
Prothrombin time (PT) and INR we evaluated using STA Neoptimal reagent, Diagnostica Stago, Canada, with a reference range of 70–120%.
Activated Partial Thromboplastin Time (APTT) was assessed with STA Cephascreen reagent, Diagnostica Stago, Canada, with a normal range of 24–35 s.
Thrombin Time (TT) was evaluated with STA Thrombin, Diagnostica Stago, Canada with a reference range of 14–21 s.
Fibrinogen levels were determined using STA Liquid Fib reagent, Diagnostica Stago, Canada, with a normal range of 200–400 mg/dL.
D-dimer assessment employed an immunoturbidimetric method (TA Liatest D-DI Plus reagent, Diagnostica Stago, Canada) with a reference range of 0-0.5 ug/mL FEU.
Antithrombin time (AT) utilized a colorimetric method with the STA Stachrom AT III reagent, Diagnostica Stago, Canada, and reference range of 80–120%.
Factor VIII assessment involved STA Immunodef VIII, Diagnostica Stago, Canada, with a reference range of 60–150%.
Von Willebrand factor assessment used an immunoturbidimetric method (STA Liatest VWF: Ag reagent, Diagnostica Stago, Canada) with aormal range was 50–160%.
Platelet Function Assessment
ASPI Test
Platelet function in response to acetylsalicylic acid was evaluated using impedance aggregation in a Multiplate analyzer (Roche Diagnostics, Mannheim, Germany), with a reference range from 745 to 1361 AU × min.
ADP test
Platelet function in response to clopidogrel was assessed via impedance aggregation in a Multiplate analyzer (Roche, Diagnostics, Mannheim, Germany), with a reference range of 534 to 1220 AU × min.
Fibrin Clot Permeability Assessment
Fibrin clot permeability was evaluated using a pressure system 18. Clots were obtained from citrated plasma by applying 1 IU/mL of human thrombin and 20mM CaCl2 according to established standards 13. The volume and mass of the buffer flowing through the clot was measured over a specified time period.
Permeability Coefficient (Ks) Calculation: The Ks (×10− 9cm2) was calculated using the following formula: Ks (×10− 9cm2) = Q × L × η/t × A × ∆P, Where:
Q (cm3) represents the flow rate at time t (s),
L (cm) signifies the length of the fibrin gel,
η (dyne × s/cm2) denotes the viscosity of the liquid,
A (cm2) signifies the cross-sectional area, and
∆P (dyne/cm2) represents the pressure gradient.
Statistical Analysis
Continuous variables were presented as means and standard deviations for normally distributed data or medians with lower and upper quartiles (IQR: 25th to 75th) for data with non-normal distribution. Categorical variables were presented as percentages. Normal distribution was verified using the Shapiro-Wilk test. Statistical tests included the chi-squared test for categorical variables and the Student’s t-test or Mann-Whitney U test for continuous variables. Friedman rank sum test and exact all-pairs comparisons tests of Friedman-type ranked data 19[ and Mann-Whitney U test with Holm-Bonferroni correction for multiple comparisons were used. To assess a monotonic trend the Page's ordered aligned rank sum test was used. Repeated measures correlation was also calculated 20. A P value < 0.05 was considered statistically significant. All analyses were conducted using SAS 9.4 (SAS Institute Inc., Cary, NC, USA) and R version 4.3.1 (R Core Team, 2023).