Boško Skorić

Different endothelin receptor subtypes are involved in phospholipid signalling in the proximal tubule of rat kidney

Phospholipid signalling mediated by endothelin (ET) receptor subtypes was studied in the rat proximal tubule. In freshly isolated proximal tubule cells, ET-1, ET-2 and sarafotoxin S6c (S6c) evoked an increase in 1,2-diacylglycerol (DAG), inositol 1,4,5-trisphosphate (InsP3 and phosphocholine (PCho), suggesting stimulation of both phosphatidyl-inositol 4,5-bisphosphate- and phosphatidyl-choline-specific phospholipase C (PLC), while ET-3 increased only DAG and PCho, presumably via phosphatidyl-choline-dependent PLC. Renal cortical slices were also stimulated by the above-mentioned agonists, followed by isolation of either brush border (BBM) or basolateral (BLM) membranes for which mass measurements of inositol lipids and DAG were performed. In BBM, DAG increased in response to ET-1, ET-2 and ET-3, and was followed by protein kinase C (PKC) translocation to the BBM, while in BLM, DAG formation and translocation of PKC were observed only in response to ET-3, suggesting spatial segregation of signalling systems between two membane domains of proximal tubule cells. Tyrphostine, pertussis toxin (PTX) or cholera toxin (CTX) did not influence ET-mediated signalling in either of the membranes, suggesting involvement of PTX- and CTX-insensitive G-protein-mediated stimulation of PLCβ by ET receptors. ET-dependent stimulation of PLC in BBM and BLM was used as a tool to examine the presence of different ET receptor subtypes in these two cell membrane domains. BQ123, an inhibitor of ETA receptors, did not prevent ET-1-mediated signalling in BBM, but an ETA,B antagonist, bosentan, inhibited ET-3-mediated signalling in BBM. In addition, an ETB agonist, S6c, stimulated PLC in BBM. Neither BQ123 nor bosentan inhibited ET-3 signalling in BLM. Therefore, these data strongly suggest the presence of ETB receptors coupled to phosphatidyl-inositol 4,5-bisphosphate- and phosphatidyl-choline-dependent PLC in BBM and ETC receptors linked to phosphatidyl-choline-dependent PLC in BLM.

Initial patency of the infarct-related artery in patients with acute ST elevation myocardial infarction is related to platelet response to aspirin

INTRODUCTION A proportion of patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary angiography (PCI) presents with patent infarct-related artery (IRA) on initial angiography. We tested the hypothesis that stronger platelet response to aspirin in these patients at admission might be associated with higher initial coronary flow in the IRA. METHODS Platelet response to aspirin was assessed with Multiplate ASPI-test before coronary angiography in 70 patients on previous aspirin treatment admitted for acute STEMI. Coronary flow on initial angiogram was evaluated quantitatively according to the Thrombolysis in Myocardial Infarction (TIMI) grading system. Depending on the degree of arachidonic acid (AA) induced platelet aggregation in ASPI-test, patients were stratified into four quartiles and compared according to initial TIMI flow. RESULTS When TIMI flow was compared according to quartiles of platelet aggregation in ASPI-test, we have found significantly higher frequency of TIMI-2 and TIMI-3 flow among patients with low values of ASPI-test, i.e. with stronger aspirin response (P=0.014). None of the patients in the highest quartile of ASPI-test had TIMI flow of 2 or 3. CONCLUSIONS Patients with stronger antiplatelet response to aspirin therapy in acute STEMI are more likely to present with spontaneous IRA recanalization.

Cardiac allograft vasculopathy: diagnosis, therapy, and prognosis.

Development of cardiac allograft vasculopathy represents the major determinant of long-term survival in patients after heart transplantation. Due to graft denervation, these patients seldom present with classic symptoms of angina pectoris, and the first clinical presentations are progressive heart failure or sudden cardiac death. Although coronary angiography remains the routine technique for coronary artery disease detection, it is not sensitive enough for screening purposes. This is especially the case in the first year after transplantation when diffuse and concentric vascular changes can be easily detected only by intravascular ultrasound. The treatment of the established vasculopathy is disappointing, so the primary effort should be directed toward early prevention and diagnosis. Due to diffuse vascular changes, revascularization procedures are restricted only to a relatively small proportion of patients with favorable coronary anatomy. Percutaneous coronary intervention is preferred over surgical revascularization since it leads to better acute results and patient survival. Although there is no proven long-term advantage of drug-eluting stents for the treatment of in-stent restenosis, they are preferred over bare-metal stents. Severe vasculopathy has a poor prognosis and the only definitive treatment is retransplantation. This article reviews the present knowledge on the pathogenesis, diagnosis, treatment, and prognosis of cardiac allograft vasculopathy.

The effect of big endothelin-1 in the proximal tubule of the rat kidney

1 An obligatory step in the biosynthesis of endothelin‐1 (ET‐1) is the conversion of its inactive precursor, big ET‐1, into the mature form by the action of specific, phosphoramidon‐sensitive, endothelin converting enzyme(s) (ECE). Disparate effects of big ET‐1 and ET‐1 on renal tubule function suggest that big ET‐1 might directly influence renal tubule function. Therefore, the role of the enzymatic conversion of big ET‐1 into ET‐1 in eliciting the functional response (generation of 1,2‐diacylglycerol) to big ET‐1 was studied in the rat proximal tubules. 2 In renal cortical slices incubated with big ET‐1, pretreatment with phosphoramidon (an ECE inhibitor) reduced tissue immunoreactive ET‐1 to a level similar to that of cortical tissue not exposed to big ET‐1. This confirms the presence and effectiveness of ECE inhibition by phosphoramidon. 3 In freshly isolated proximal tubule cells, big ET‐1 stimulated the generation of 1,2‐diacylglycerol (DAG) in a time‐and dose‐dependent manner. Neither phosphoramidon nor chymostatin, a chymase inhibitor, influenced the generation of DAG evoked by big ET‐1. 4 Big ET‐1‐dependent synthesis of DAG was found in the brush‐border membrane. It was unaffected by BQ123, an ETA receptor antagonist, but was blocked by bosentan, an ETA B‐nonselective endothelin receptor antagonist. 5 These results suggest that the proximal tubule is a site for the direct effect of big ET‐1 in the rat kidney. The effect of big ET‐1 is confined to the brush‐border membrane of the proximal tubule, which may be the site of big ET‐1‐sensitive receptors.

The predictive value of platelet function point-of-care tests for postoperative blood loss and transfusion in routine cardiac surgery: a systematic review.

Excessive bleeding after cardiopulmonary bypass (CPB) operations remains to be a persistent problem and weak platelet function certainly contributes to bleeding diathesis. Antiplatelet therapy (APT) is an integral component of perioperative management in patients undergoing cardiac surgery procedures, both with and without use of CPB. In addition to individual variability in platelet function, different preoperative APT administration/discontinuation management further affects platelet function, which in turn may reflect bleeding tendency. However, the impact of drug-induced platelet inhibition on early postoperative bleeding extent remains difficult to predict. Herein, we reviewed the available evidence on the association between platelet function testing values and the extent of bleeding and transfusion requirements in early perioperative period. Currently, the association between platelet function measured by ex vivo assay and the occurrence of bleeding events remains uncertain. The intent of this review is to provide comprehensive literature insight into published evidence, investigating the possibility of platelet function tests to predict bleeding extent as well as transfusion requirements in cardiac surgery patients.

Pretransplant and perioperative predictors of early heart transplantation outcomes

Aim To identify predictors of 3-month mortality after heart transplantation in a Croatian academic center. Methods A retrospective review of institutional database identified 117 heart transplantations from January 2008 to July 2014. Two children <14 years were excluded from the study. The remaining 115 patients were dichotomized into survivors and non-survivors adjudicated at 3-months postoperatively, and their demographic, clinical, and longitudinal hemodynamic data were analyzed. Results 3-month survival after heart transplantation was 86%. Non-survivors were older (59 ± 8 vs 50 ± 14 years, P = 0.009), more likely to have previous cardiac surgery (44% vs 19%; odds ratio [OR] 3.28, 95% confidence interval [CI] 1.08-9.90; P = 0.029), lower body mass index (BMI) (25 ± 4 vs 28 ± 2 kg/m2, P = 0.001), and be diabetics (44% vs 23%; OR 2.57, 95% CI 0.86-7.66; P = 0.083). Creatinine clearance was marginally superior among survivors (59 ± 19 vs 48 ± 20 mL/min, P = 0.059). Donor age and sex did not affect outcomes. Non-survivors were more likely to have had ischemic cardiomyopathy (69% vs 32%, P = 0.010). Postoperative utilization of epinephrine as a second line inotropic agent was a strong predictor of mortality (63% vs 7%; OR 21.91; 95% CI 6.15-78.06; P < 0.001). Serum lactate concentrations were consistently higher among non-survivors, with the difference being most pronounced 2 hours after cardiopulmonary bypass (9.8 ± 3.5 vs 5.2 ± 3.2 mmol/L, P < 0.001). The donor hearts exhibited inferior early hemodynamics in non-survivors (cardiac index 3.0 ± 1.0 vs 4.0 ± 1.1 L/min/m2, P = 0.001), stroke volume (49 ± 24 vs 59 ± 19 mL, P = 0.063), and left and right ventricular stroke work indices (18 ± 8 vs 30 ± 11 g/beat/m2, P < 0.001 and 5 ± 3 vs 7 ± 4 g/beat/m2, P = 0.060, respectively). Non-survivors were more likely to require postoperative re-sternotomy (50% vs 12%; OR 7.25, 95% CI 2.29-22.92; P < 0.001), renal replacement therapy (RRT) (69% vs 9%; OR 22.00, 95% CI 6.24-77.54; P < 0.001), and mechanical circulatory assistance (MCS) (44% vs 5%; OR 14.62, 95% CI 3.84-55.62; P < 0.001). Binary logistic regression revealed recipient age (P = 0.024), serum lactates 2 hours after CPB (P = 0.007), and epinephrine use on postoperative day 1 (P = 0.007) to be independently associated with 3-month mortality. Conclusion Pretransplant predictors of adverse outcome after heart transplantation were recipient age, lower BMI, ischemic cardiomyopathy, reoperation and diabetes. Postoperative predictors of mortality were inferior donor heart hemodynamics, epinephrine use, and serum lactate concentrations. Non-survivors were more likely to require re-sternotomy, MCS, and RRT.

CYP2C19*2 genotype influence in acute coronary syndrome patients undergoing serial clopidogrel dose tailoring based on platelet function testing: Analysis from randomized controlled trial NCT02096419.

Aspirin and a P2Y12 inhibitor administration are crucial in acute coronary syndrome (ACS) and percutaneous coronary intervention. ADP- induced high on-treatment platelet reactivity (HTPR) increases the rate of adverse ischemic events and whether it is a modifiable risk factor for future events is not clear. CYP2C19 enzyme plays a significant role in clopidogrel bioactivation and its polymorphism can cause clopidogrel pharmacodynamic effect reduction. Earlier, we performed a clopidogrel dose tailoring trial based on serial platelet function testing (PFT) using Multiplate® electrode aggregometry during 12 months to maintain optimal platelet reactivity (PR) in ACS patients presenting with HTPR. Patients were randomly assigned to an interventional group taking up to two additional 600 mg loading doses and a range of 75-300 mg maintenance dose, and a control group on standard clopidogrel maintenance dose. Patients in the interventional group maintained better PR during follow-up and had better outcome. In this exploratory analysis we sought to evaluate the effect of CYP2C19*2 genotype on PR levels in both groups of patients during the initial trial. There were no differences in PR between CYP2C19*2 carriers and non-carriers in the interventional group (p=0.187) while CYP2C19*2 carriers had significantly higher PR compared to non-carriers in the control group (p<0.05). Adjusting clopidogrel dose after PFT to reach and maintain optimal PR might overcome unfavorable genotype in ACS patients initially presenting with HTPR. This implies that strategies of antiplatelet therapy tailoring studies should be focused on maintaining optimal PR phenotype, rather than adjusting P2Y12 inhibition based on genotype to improve outcomes.

Platelet response to standard aspirin and clopidogrel treatment correlates with long-term outcome in patients with acute ST-elevation myocardial infarction

In this article the authors analyze platelet response in patients with acute ST elevation myocardial infarction by measuring its residual activity with point of care method (Multiplate). After 12 months they analyze the connection between the paltelet response and clinical outcomes.

Donor heart selection and outcomes: An analysis of over 2,000 cases

BACKGROUND Decision-making when offered a donor heart for transplantation is complex, and supportive data describing outcomes according to acceptance or non-acceptance choices are sparse. Our aim was to analyze donor heart acceptance decisions and associated outcomes at a single center, and after subsequent acceptance elsewhere. METHODS This investigation was a retrospective analysis of data obtained from the University of Vienna Medical Center and Eurotransplant centers for the period 2001 to 2015. RESULTS Our center accepted 31.8% (699 of 2,199) of donor hearts offered. Unlike other centers, the acceptance rate, with or without transplantation, did not increase over time. Of the donor hearts rejected by our center, 38.1% (572 of 1,500) were later accepted elsewhere. Acceptance rates were twice as high for donor hearts initially rejected for non-quality reasons (339 of 601, 56.4%) compared with initial rejection for quality reasons (233 of 899, 25.9%). Three-year patient survival rate was 79% at Vienna; for donor hearts initially rejected by Vienna for non-quality reasons or quality reasons, it was 73% and 63%, respectively (p < 0.001). Outcomes at other centers after transplantation of grafts rejected by Vienna varied according to the reason for rejection, with good 3-year survival rates for rejection due to positive virology (77%), high catecholamines (68%), long ischemic time (71%), or low ejection fraction (68%), but poor survival was observed for hearts rejected for hypernatremia (46%), cardiac arrest (21%), or valve pathology (50%). CONCLUSIONS A less restrictive policy for accepting donor hearts at our center, particularly regarding rejection for non-quality reasons or for positive virology, high catecholamine levels, longer ischemic time, or low ejection fraction, could expand our donor pool while maintaining good outcomes.

Venovenous extracorporeal membrane oxygenation in a patient with acute respiratory distress syndrome caused by drowning

Case report: 32-year-old male patient with no prior medical history presented to our Emergency Department following drowning and a successful resuscitation. He was found submerged in the pool just a couple of minutes after being seen conscious and swimming. Lifeguard on duty pulled him out of the pool and started cardiopulmonary resuscitation. Upon the arrival of Emergency Medical Service, patient had a pulse and was breathing spontaneously, but was exhibiting grand mal seizures and not recovering consciousness. In the emergency department he was put on mechanical ventilation (MV) due to global RF and in the Coronary Care Unit therapeutic hypothermia (TH) was started. Urgent diagnostics was performed and no signs of stroke, coronary artery disease, pulmonary embolism or significant electrolyte imbalance were detected. 12-lead ECG and echocardiography showed no abnormal findings despite severe respiratory acidosis. Due to signs of ARDS (Figure 1) and worsening RF in Marijan Pašalić*, Boško Skorić, Maja Čikeš, Daniel Lovrić, Jana Ljubas Maček, Hrvoje Jurin, Jure Samardžić, Joško Bulum, Davor Miličić