Zinc metalloprotease ProA of Legionella pneumophila increases alveolar septal thickness in human lung tissue explants by collagen IV degradation.

ProA is a secreted zinc metalloprotease of Legionella pneumophila causing lung damage in animal models of Legionnaires' disease. Here we demonstrate that ProA promotes infection of human lung tissue explants (HLTEs) and dissect the contribution to cell type specific replication and extracellular virulence mechanisms. For the first time, we reveal that co-incubation of HLTEs with purified ProA causes a significant increase of the alveolar septal thickness. This destruction of connective tissue fibres was further substantiated by collagen IV degradation assays. The moderate attenuation of a proA-negative mutant in A549 epithelial cells and THP-1 macrophages suggests that effects of ProA in tissue mainly result from extracellular activity. Correspondingly, ProA contributes to dissemination and serum resistance of the pathogen, which further expands the versatile substrate spectrum of this thermolysin-like protease. The crystal structure of ProA at 1.48 Å resolution showed high congruence to pseudolysin of Pseudomonas aeruginosa, but revealed deviations in flexible loops, the substrate binding pocket S1 ' and the repertoire of cofactors, by which ProA can be distinguished from respective homologues. In sum, this work specified virulence features of ProA at different organisational levels by zooming in from histopathological effects in human lung tissue to atomic details of the protease substrate determination.

Predictors of postoperative atrial fibrillation persisting beyond hospital discharge after coronary artery bypass grafting.

OBJECTIVE: Minimal invasive extracorporeal circuits (MiECC) have been associated with a significant reduction in the incidence of postoperative atrial fibrillation (AF). Nevertheless, AF remains one of the most common complications following elective primary coronary artery bypass grafting (CABG). The aim of this study was to identify the predictors of AF persisting beyond the hospital stay in elective primary CABG patients. METHODS: We conducted a retrospective analysis for the predictors of AF that persisted beyond discharge between all patients who received an elective isolated CABG in our institution between 2009 and 2014. Patients with a positive history for intermittent or persistent AF were excluded from the analysis. Almost all patients were discharged to a rehabilitation facility where they stayed for 3 to 4 weeks postoperatively. At rehab approximately 91% of them received Holter monitoring at least once prior to their discharge. RESULTS: A total of 770 patients were included in the analysis of which 763 patients survived the in-hospital stay. The incidence of AF at hospital discharge was 4.2% (32/763) while that on Holter monitor at Rehab was 1.5% (10/685). Age and the type of extracorporeal circuit (ECC) utilized were the only significant predictors for both AF at discharge (p < 0.01 both) and on Holter monitor in rehab (p < 0.01 and 0.02, respectively). This was also confirmed on multivariate analysis. CONCLUSION: Our findings show that the benefits of MiECC regarding the incidence of postoperative AF persist beyond hospital discharge. They may thus positively influence the outcomes of patients beyond the early postoperative period.

Aortic valve replacement with or without myocardial revascularization in octogenarians. Can minimally invasive extracorporeal circuits improve the outcome?

OBJECTIVE: The positive impact of minimally invasive extracorporeal circuits (MiECC) on patient outcome is expected to be most evident in patients with limited physiologic reserves. Nevertheless, most studies have limited their use to low-risk patients undergoing myocardial revascularization. As such, there is little evidence to their benefit outside this patient population. We, therefore, set out to explore their potential benefit in octogenarians undergoing aortic valve replacement (AVR) with or without concomitant myocardial revascularization. METHODS: Based on the type of the utilized ECC, we performed a retrospective propensity score-matched comparison among all octogenarians (n = 218) who received a primary AVR with or without concomitant coronary artery bypass grafting in our institution between 2003 and 2010. RESULTS: A MiECC was utilized in 32% of the patients. The propensity score matching yielded 52 matched pairs. The 30-day postoperative mortality (2% vs. 10%; p=0.2), the incidence of low cardiac output (0% vs. 6%; p=0.2) and the Intensive Care Unit (ICU) stay (2.5 ± 2.6 vs. 3.8 ± 4.7 days; p=0.06) were all in favour of the MiECC group, but failed to reach statistical significance while the 90-day postoperative mortality did (2% vs. 16%; p=0.02). CONCLUSION: MiECCs have a positive influence on the outcome of octogenarians undergoing AVR with or without concomitant coronary artery bypass grafting. Their use should, therefore, be extended beyond isolated coronary artery bypass graft (CABG) surgery.

Modular minimal invasive extracorporeal circuits: another step toward universal applicability?

INTRODUCTION: Safety concerns have been one of the main reasons opposing a wider acceptance of minimal invasive extracorporeal circuits (MiECC). Following an extensive experience and a multitude of modifications, we have set out to employ a modular MiECC as a universal extracorporeal circuit. METHODS: A total of 129 cardiac surgical procedures were performed by a single surgeon in 2013. Excluding procedures done under circulatory arrest or with the potential need of such, the MiECC was utilized in almost 90% of surgeries. Of sixty-two (simple procedures) patients who underwent coronary artery bypass grafting (CABG), aortic valve replacement (AVR) or CABG + AVR, 82% were non-elective, 10% had a left ventricular ejection fraction (EF) <30% and most had an impaired renal function. Thirty-eight patients had more complex surgeries (complex procedures), 37% of which were urgent, 15% had an EF <30% and the majority had renal dysfunction. RESULTS: The 30-day mortality was 5% in simple procedures and 2.5% in complex procedures. The incidence of postoperative atrial fibrillation was 13% and 16%, respectively. Optimum outcome was defined as a freedom from all complications and blood transfusions and was achieved in 52% and 42%, respectively. CONCLUSIONS: This report shows that modular MiECC can be employed with a high safety margin in cardiac surgery. Furthermore, it emphasizes the impact that minimal invasive philosophy could have in improving patient care.

Effect of minimized perfusion circuit on brain injury markers carnosinase and brain-type fatty binding protein in coronary artery bypass grafting patients.

A minimized perfusion circuit (MPC) has proven to be superior to the conventional circulatory perfusion bypass (CCPB) as it reduces the blood-material interaction and hemodilution. Until now not much is known about impact these different perfusion systems have on the brain. The objective of this study is to determine carnosinase and brain-type fatty binding protein (BFABP) activity as novel specific biomarkers for ischemic brain tissue damage and how their activity differs during and after MPC and CCPB as well as to compare the inflammatory response of both perfusion systems. In a prospective pilot study, 28 patients undergoing coronary artery bypass grafting were randomly divided into an MPC group (n = 14) and a CCPB group (n = 14). Blood samples were taken before, during, and after operation until the fifth postoperative day. The brain biomarker carnosinase was determined by measuring the rate of histidine production from the substrate homocarnosine, whereas BFABP and interleukin-6 were determined by enzyme-linked immunosorbent assay (ELISA). C-reactive protein (CRP) and endothelin-1 were determined by enzyme immunoassay. The mean serum carnosinase activity was significantly higher in MPC (0.57 ± 0.34 nM histidine/mL/min) as compared with the CCPB group (0.36 ± 0.13 nM histidine/mL/min) at the end of operation (P = 0.02). The BFABP did not show any difference between the two groups in the immediate postoperative period until the second postoperative day. From that time point onward, it showed a steep increase in the CCPB group (581.3 ± 157.11 pg/mL) as compared with the concentrations in the MPC group (384.6 ± 39 pg/mL) (P = 0.04). The inflammation markers interleukin-6 and CRP showed a similar pattern in both groups without significant difference. In contrast, the leukocyte count on operation day and endothelin-1 on the first postoperative day were significantly higher in the CCPB group (P = 0.01, P = 0.03, respectively). MPC showed a significant higher and stable serum carnosinase activity during extracorporeal circulation as compared with the CCPB due to less hemodilution and a better preserved oxygen capacity. As a consequence, the antioxidant stress during MPC is limited as compared with CCPB, which means less brain tissue damage reflected by a lower BFABP release. Except endothelin-1 and leukocyte count, the inflammatory response of the MPC and CCPB was equal.

A 20-year experience with cryopreserved allografts as the valve replacement of choice in aortic root reconstruction for destructive endocarditis with abscess formation.

OBJECTIVES: The aim of this retrospective study was to assess the early- and long-term outcomes following the use of cryopreserved allografts in aortic valve endocarditis with peri-annular abscess formation. METHODS: From 2001 to 2021, 110 consecutive patients with active infective endocarditis and peri-annular abscess, underwent a cryopreserved allograft root replacement. In 100 patients (91%), the operation was performed <48 h after admission due to refractory heart failure and or septic shock. In 95 patients (86.4%), a redo operation was performed due to a prosthetic valve endocarditis. Preoperatively, 12 patients were dialysis-dependent and 30 patients suffered from a recent stroke. RESULTS: The 30-day mortality was 18% (20 patients). Freedom from reintervention was 98.3% (standard deviation: 1.7) at 1 year and 83.3% (standard deviation: 8.5) at 10 years. Four patients required a redo operation. Three patients did develop re-endocarditis. Freedom from re-endocarditis was 95% after 17 years of follow-up. Preoperative dialysis dependency (odds ratio: 22.75, 95% confidence interval: 4.79-108.14, P < 0.001), ejection fraction under 30% (odds ratio: 17.91, 95% confidence interval: 3.27-98.01, P < 0.001) and stroke within 14 days prior to operation (odds ratio: 5.21, 95% confidence interval: 1.28-21.2, P = 0.021) were incremental factors associated with the 30-day mortality. CONCLUSIONS: In aortic root endocarditis with abscesses formation, cryopreserved allografts exhibit excellent clinical performance with a low rate of reinfection and reintervention, which make its use as valve replacement a very desirable option. Dialysis dependency, ejection fraction under 30% and recent stroke have the highest impact on the 30-day mortality.

Beating-heart coronary artery bypass grafting with miniaturized cardiopulmonary bypass results in a more complete revascularization when compared to off-pump grafting.

The technique of miniaturized cardiopulmonary bypass (M-CPB) for beating-heart coronary artery bypass grafting (CABG) is relatively new and has potential advantages when compared to conventional cardiopulmonary bypass (CPB). M-CPB consists of less tubing length and requires less priming volume. The system is phosphorylcholine coated and results in minimal pump-related inflammatory response and organ injury. Finally, this technique combines the advantages of the off-pump CABG (OPCAB) with the better exposure provided by CPB to facilitate complete revascularization. The hypothesis is that CABG with M-CPB has a better outcome in terms of complete coronary revascularization and perioperative results as that compared to off-pump CABG (OPCAB). In a retrospective study, 302 patients underwent beating-heart CABG, 117 (39%) of them with the use of M-CPB and 185 (61%) with OPCAB. After propensity score matching 62 patients in both groups were demographically similar. The most important intra- and early-postoperative parameters were analyzed. Endpoints were hospital mortality and complete revascularization. Hospital mortality was comparable between the groups. The revascularization was significantly more complete in M-CPB patients than in patients in the OPCAB group. Beating-heart CABG with M-CPB is a safe procedure and it provides an optimal operative exposure with significantly more complete coronary revascularization when compared to OPCAB. Beating-heart CABG with the support of a M-CPB is the operation of choice when total coronary revascularization is needed.

Is aortic valve replacement with a minimally invasive extracorporeal circuit a contemporary option for octogenarians?

OBJECTIVES: Minimally invasive extracorporeal circuits have been introduced to cardiac surgery in an attempt to reduce the negative effects of cardiopulmonary bypass on patient outcome. On the other hand, transcatheter aortic valve replacement (TAVR) provides an excellent option to replace the aortic valve without the need for cardiopulmonary bypass. Several studies have compared TAVR to surgical aortic valve replacement (SAVR) but none have utilized a minimally invasive extracorporeal circuit. METHODS: We retrospectively analysed the results of both procedures among octogenarians operated in our department from 2003 to 2016. Excluded were patients with an active endocarditis, a history of previous cardiac surgery, as well as those who had a minimally invasive surgical approach. This yielded 81 and 142 octogenarians in the SAVR and TAVR groups, respectively. To compensate for a lack of randomization, we performed a propensity score analysis, which yielded 68 patient pairs for the final analysis. RESULTS: The 30-day postoperative mortality was lower in the SAVR group (1.5% vs 5.9%) but not statistically significant (P = 0.4). In contrast, the incidence of postoperative atrial fibrillation was lower in the TAVR group (13% vs 29%) but also non-significant (P = 0.2). Finally, the incidence of paravalvular leakage was in favour of the SAVR group (2.9% vs 52%; P = 0.001) while the transfusion requirement was significantly lower in the TAVR group (29% vs 72%; P < 0.001). CONCLUSIONS: SAVR utilizing a minimally invasive extracorporeal circuit improves the quality of patient care and can offer an alternative to TAVR in octogenarians.

Autotransfusion management during and after cardiopulmonary bypass alters fibrin degradation and transfusion requirements.

UNLABELLED: The coagulation-fibrinolytic profile during cardiopulmonary bypass (CPB) has been widely documented. However, less information is available on the possible persistence of these alterations when autotransfusion is used in management of perioperative blood loss. This study was designed to explore the influence of autotransfusion management on intravascular fibrin degradation and postoperative transfusions. Thirty patients, undergoing elective primary isolated coronary bypass grafting, were randomly allocated either to a control group (group A; n=15) or an intervention group (group B; n=15) in which mediastinal and residual CPB blood was collected and processed by a continuous autotransfusion system before re-infusion. Intravascular fibrin degradation as indicated by D-dimer generation was measured at five specific intervals and corrected for hemodilution. In addition, chest tube drainage and need for homologous blood were monitored. D-dimer generation increased significantly during CPB in group A, from 312 to 633 vs. 291 to 356 ng/mL in group B (p = .001). The unprocessed residual blood (group A) revealed an unequivocal D-dimer elevation, 4131 +/- 1063 vs. 279 +/- 103 ng/mL for the processed residual in group B (p < .001). Consequently, in the first post-CPB period, the intravascular fibrin degradation was significantly elevated in group A compared with group B (p = .001). Twenty hours postoperatively, no significant difference in D-dimer levels was detected between both groups. However, a significant intra-group D-dimer elevation pre- vs. postoperative was noticed from 312 to 828 ng/mL in group A and from 291 to 588 ng/mL in group B (p < .01 for both). Postoperative chest tube drainage was higher in the patients from group A, which also had the highest postoperative D-dimer levels. Patients in group A perceived a higher need for transfusions of red cells suspensions postoperatively. These data clearly indicate that autotransfusion management during and after CPB suppresses early postoperative fibrin degradation. KEYWORDS: cardiopulmonary bypass, cardiotomy suction, coronary surgery, autotransfusion, fibrin degradation.

Impact of minimally invasive extracorporeal circuits on octogenarians undergoing coronary artery bypass grafting. Have we been looking in the wrong direction?

OBJECTIVES: Minimally invasive extracorporeal circuits (MiECCs) aim at the preservation of physiologic reserves, the impact of which is expected to be most evident in patients in whom these are depleted. In this context, octogenarians present a subpopulation of specific interest. METHODS: Based on the type of the utilized ECC, we performed a retrospective comparison between all octogenarians (n = 324) who received a primary coronary artery bypass in our institution from 2003 until 2010. RESULTS: An MiECC was used in 52% of patients. Preoperative variables showed that the MiECC patients were older (83 ± 2 vs 82 ± 2 years; P = 0.001), had higher incidence of renal dysfunction (8% vs 3%; P = 0.04), moderately reduced left ventricular function (43 vs 33%; P = 0.07) and lower incidence of unstable angina (20% vs 28%; P = 0.06). To overcome these differences, a propensity score matching was performed and yielded 126 matched pairs of patients. The overall transfusion of packed red blood cells (2.3 ± 2.3 vs 3.4 ± 3.2 units per patint; P = <0.001), the rate of low cardiac output (0% vs 6%; P = 0.01) and the 30-day postoperative mortality (2.4% vs 9.5%; P = 0.02) were all in favour of the MiECC group in the matched patient population. CONCLUSIONS: The MiECC concept has shown its benefits regarding both morbidity and mortality in this high-risk patient population. We believe that this beneficial effect finds its reason in a better preservation of physiologic reserves that are essential for a positive outcome in this patient group.

Analysis of mortality within the first six months after coronary reoperation.

BACKGROUND: Identify risk factors associated with mortality following repeat coronary revascularization (redoCABG) within the first 6 months following surgery. METHODS: Five hundred forty-one redoCABG patients (1987 to 1998) were studied by univariant and multivariant analysis. Mortality was assessed at three different points: hospital mortality (A) (36/541, 6.7%); mortality at 6 months (C) (75/541, 13.9%); and outpatient perioperative mortality, which is a death occurring from the time of hospital discharge to 6 months postoperatively (B) (39/541, 7.2%). RESULTS: Diabetes, hypertension, peripheral vascular disease, renal insufficiency, lung disease, myocardial infarction (MI) before the first operation, MI between the first and redoCABG, lack of sinus rhythm, no IMA graft, acute/emergency operation, perfusion time, and perioperative MI were all identified as risk factors related to early mortality. MI before the first operation, antegrade cardioplegia, and the time period 1987 to 1992 all influenced hospital mortality (A). Diabetes, hypertension, renal insufficiency, lung disease, and valvular heart disease all influenced the outpatient mortality up to 6 months. Independent predictive factors for early mortality were: age more than 69 years; diabetes; vascular insufficiency; chronic lung disease; MI between first and redoCABG; no IMA-graft; acute preoperative MI; emergency operation; perfusion time; perioperative MI; and the time period 1987 to 1992. Risk factors for in-hospital death included MI between the first and redoCABG, cardiopulmonary bypass time, and the time period 1987 to 1992. Diabetes is an important risk factor during the outpatient perioperative phase. Emergency surgery and perioperative MI predict mortality regardless of the time period (A, B, or C). CONCLUSIONS: Early mortality after redoCABG is influenced by many variables during the first 6 months following surgery. Understanding these factors and their time course may better help to assess the true risk associated with reoperation for recurrent coronary insufficiency.

Preoperative prediction of prolonged stay in the intensive care unit for coronary bypass surgery.

OBJECTIVES: To construct a predictive model for a prolonged stay in the intensive care unit (ICU) for coronary artery bypass graft surgery (CABG). METHODS: Eight hundred and eighty-eight patients undergoing CABG were studied by univariate and multivariate analysis. Prolonged stay in the ICU was defined as >/=3 days stay. Stepwise selective procedure (P/=0.40 was used as cut-off point for the prognostic test. The specificity of this test for prolonged stay in the ICU was 99%; sensitivity 9%; positive predictive value 60%; and negative predictive value 89%. CONCLUSIONS: The results show that individual patients presented for CABG, can be stratified according to their risk for prolonged stay >/=3 days in the ICU.

Preoperative prediction of early mortality in redocoronary artery surgery.

OBJECTIVES: Construct a predictive model for early mortality in coronary reoperations (RECABG). METHODS: Five hundred and forty one RECABG (1987-1998) were studied by univariate and multivariate analysis. Stepwise selective procedure (p<0.05) was used to identify a subset of variables with prognostic value for early mortality. This subset was used to calculate a prognostic score 'S' and a predicted probability 'P' for early mortality, P=1/1+e(-S). Sensitivity analysis was used for evaluation. RESULTS: The best predictive variables for early mortality were diabetes, vascular-, lung-disease, a myocardial infarction between the primary and the RECABG, acute- and emergency operation and the operative period. The prognostic accuracy (receiver operating characteristics curve (ROC) area) was 80%. Observed probabilities compare well with the predicted probabilities, and patients were classified in low risk (5%), intermediate risk (15%), high risk (30%) and very high risk (40%). A predicted probability of > or =0.40 was used as cut-off point for the prognostic test. The specificity of this test was 97%, sensitivity 33%, predictive value of a positive test 63% and 90% for a negative test. CONCLUSIONS: The results show that individual patients presented for RECABG, can be stratified according to their early mortality risk. This information can be used to inform the patient, and also to discus the opportunity of the RECABG.

Changing profile of patients undergoing redo-coronary artery surgery.

OBJECTIVE: To outline the changes of the patient population undergoing redo-coronary artery bypass surgery (RECABG). METHODS: Preoperative data of 582 first RECABGs, January 1987-June 2000 were analyzed. Group A: 1987-1991 (n=193); group B: 1992-1995 (n=201); and group C: 1996-June 2000 (n=188). RESULTS: These 582 RECABGs represent about 8.5% of the performed bypass surgeries during this period. Mean age (P=<0.001), percentage of patients with kidney disease (P=0.001), a preoperative PTCA (P<0.001) increased. Significant more elective operations (P<0.001) and lesser urgent operations (P=0.001) were performed in group C. There is a significant different distribution of vessel disease over the three periods (P=0.04). Significant more patients had a patent IMA graft (P<0.001). The angina-free period after CABG (P<0.001), the time period between both operations (P<0.001) and the period between the new onset of angina and the RECABG (P=0.012) increased significantly. Despite the importance of progression of atherosclerosis of any sort decrease significantly (P<0.001) over the whole study, there is a significant increase of patients reoperated for isolated progression of the disease in the native coronary arteries (P<0.001) in group C. The impact of late GF was not different for the total group (P=0.82), however, the percentage of RECABGs for isolated late GF increased significantly between group A and B (P<0.001) but there was a decrease from B to C, however, not significant (P=0.067). CONCLUSION: During the past few years there is a trend in RECABG of older patients, with more coexisting diseases. There are an increasing number of patients with patent arterial grafts, an increase of the event-free period after the CABG, the period between the CABG and RECABG and of the time period between the onset of new angina and the RECABG. Although the impact of atherosclerosis, as angiographic indication, decreased over the total group, there is the significant increase of the percentage of patients reoperated because of isolated progression of atherosclerosis in the native coronary arteries.

[An unknown but potentially serious side effect of proton pump inhibitors: hypomagnesaemia]. / Een onbekende, maar potentieel ernstige bijwerking van protonpompremmers: hypomagnesiëmie.

Long-term use of proton pump inhibitors can lead to serious hypomagnesaemia. Intestinal magnesium absorption takes place by passive paracellular and active transcellular transport. It has been hypothesized that proton pump inhibitors impair the active transcellular magnesium transport. The resulting hypomagnesaemia may cause hypoparathyroidism, hypocalcaemia and hypokalaemia. Proton pump inhibitor-induced hypomagnesaemia is reversible: it resolves when proton pump inhibitors are stopped. The indication for long-term proton pump inhibitor treatment should be evaluated periodically.

[Patients with a haematological malignancy in intensive care]. / Patiënten met een hematologische maligniteit op de Intensive Care.

In this case report we describe 2 patients with acute leukaemia, a 38-year-old and a 21-year-old woman who were both admitted to the intensive care unit (ICU) twice for different complications of underlying disease and chemotherapy. Although the survival rates for patients with haematological malignancies requiring admission to intensive care have increased in the last two decades, many physicians are still reluctant to admit these patients to intensive care. However, 50% of these patients are successfully discharged from intensive care, regardless of age or underlying haematological disease. The length of stay in the ICU does not correlate with mortality in the ICU either. Intensive mechanical ventilation and multiple organ failure increase mortality in patients with haematological malignancies undergoing intensive treatment in an ICU.

Conductivity-based hematocrit measurement during cardiopulmonary bypass.

OBJECTIVE: In a recent clinical study on the reliability of a point-of-care (POC) analyzer, we described a downward bias in hematocrit measurement during cardiopulmonary bypass leading potentially to overtreatment with packed red cells. We hypothesized that the detected deviation is caused by variations in electrolyte concentration rather than by colloids used. METHODS: Blood was sampled from patients before cardiac surgery to obtain undiluted anticoagulated whole blood samples (n = 53). From each sample, four dilution series covering a hematocrit range of 15-30% were made using NaCl (0.9%), modified gelatine (4%), hydroxyethylstarch (6%), or a potassium-based (16 mEq/l) solution, respectively. In each dilution series, hematocrit was measured by POC and via the "golden standard" microcentrifugal method to determine whether the deviation of the POC-analyzer to the microcentrifuge was dependent on the type and dilution level of the solution used. RESULTS: In contrast to the colloid-based dilution series, the crystalloids revealed a significant downward bias of the POC-analyzer with respect to the microcentrifuge (p < 0.05). Due to the correction algorithm for sodium in the POC-analyzer, this deviation was nearly constant for NaCl (mean of difference: -1.8 +/- 0.1%), but increased significantly in case of the potassium-based solution (up to -8.2 +/- 0.4% after 1.5-times dilution). The starch- and gelatine-based solutions led to a significant upward bias (p < 0.05) that increased with progressing dilution (up to 1.2 +/- 0.1% for hydroxyethylstarch and up to 1.3 +/- 0.1% for modified gelatine after 1.5-times dilution). CONCLUSIONS: Conductivity-based POC hematocrit measurement suffers from biases due to changes of the plasma constituents. The downward bias in hematocrit as often seen during cardiopulmonary bypass is driven by changes of different electrolyte concentration rather than by colloids used per se.

Diaphragm single-fiber weakness and loss of myosin in congestive heart failure rats.

Diaphragm weakness commonly occurs in patients with congestive heart failure (CHF) and is an independent predictor of mortality. However, the pathophysiology of diaphragm weakness is poorly understood. We hypothesized that CHF induces diaphragm weakness at the single-fiber level by decreasing myosin content. In addition, we hypothesized that myofibrillar Ca(2+) sensitivity is decreased and cross-bridge kinetics are slower in CHF diaphragm fibers. Finally, we hypothesized that loss of myosin in CHF diaphragm weakness is associated with increased proteolytic activities of caspase-3 and the proteasome. In skinned diaphragm single fibers of rats with CHF, induced by left coronary artery ligation, maximum force generation was reduced by approximately 35% (P < 0.01) compared with sham-operated animals for slow, 2a, and 2x fibers. In these CHF diaphragm fibers, myosin heavy chain content per half-sarcomere was concomitantly decreased (P < 0.01). Ca(2+) sensitivity of force generation and the rate constant of tension redevelopment were significantly reduced in CHF diaphragm fibers compared with sham-operated animals for all fiber types. The cleavage activity of the proteolytic enzyme caspase-3 and the proteasome were approximately 30% (P < 0.05) and approximately 60% (P < 0.05) higher, respectively, in diaphragm homogenates from CHF rats than from sham-operated rats. The present study demonstrates diaphragm weakness at the single-fiber level in a myocardial infarct model of CHF. The reduced maximal force generation can be explained by a loss of myosin content in all fiber types and is associated with activation of caspase-3 and the proteasome. Furthermore, CHF decreases myofibrillar Ca(2+) sensitivity and slows cross-bridge cycling kinetics in diaphragm fibers.

Caffeine prevents protection in two human models of ischemic preconditioning.

OBJECTIVES: We studied whether caffeine impairs protection by ischemic preconditioning (IP) in humans. BACKGROUND: Ischemic preconditioning is critically dependent on adenosine receptor stimulation. We hypothesize that the adenosine receptor antagonist caffeine blocks the protective effect of IP. METHODS: In vivo ischemia-reperfusion injury was assessed in the thenar muscle by 99mTc-annexin A5 scintigraphy. Forty-two healthy volunteers performed forearm ischemic exercise. In 24 subjects, this was preceded by a stimulus for IP. In a randomized double-blinded design, the subjects received caffeine (4 mg/kg) or saline intravenously before the experiment. At reperfusion, 99mTc-annexin A5 was administered intravenously. Targeting of annexin was quantified by region-of-interest analysis, and expressed as percentage difference between experimental and contralateral hand. In vitro, we assessed recovery of contractile function of human atrial trabeculae, harvested during heart surgery, as functional end point of ischemia-reperfusion injury. Field-stimulated contraction was quantified at baseline and after simulated ischemia-reperfusion, in a paired approach with and without 5 min of IP, in the presence (n=13) or absence (n = 17) of caffeine (10 mg/l). RESULTS: Ischemic preconditioning reduced annexin targeting in the absence of caffeine (from 13 +/- 3% to 7 +/- 1% at 1 h, and from 19 +/- 2% to 9 +/- 3% at 4 h after reperfusion, p = 0.006), but not after caffeine administration (targeting 11 +/- 2% and 16 +/- 3% at 1 and 4 h). In vitro, IP improved post-ischemic functional recovery in the control group, but not in the caffeine group (8 +/- 3% vs. -8 +/- 5%, p=0.003). CONCLUSIONS: Caffeine abolishes IP in 2 human models at a dose equivalent to the drinking of 2 to 4 cups of coffee. (The Effect of Caffeine on Ischemic Preconditioning; http://clinicaltrials.gov/ct/show/NCT00184912?order=1; NCT00184912).