Remote ischaemic conditioning: defining critical criteria for success-report from the 11th Hatter Cardiovascular Workshop.

The Hatter Cardiovascular Institute biennial workshop, originally scheduled for April 2020 but postponed for 2 years due to the Covid pandemic, was organised to debate and discuss the future of Remote Ischaemic Conditioning (RIC). This evolved from the large multicentre CONDI-2-ERIC-PPCI outcome study which demonstrated no additional benefit when using RIC in the setting of ST-elevation myocardial infarction (STEMI). The workshop discussed how conditioning has led to a significant and fundamental understanding of the mechanisms preventing cell death following ischaemia and reperfusion, and the key target cyto-protective pathways recruited by protective interventions, such as RIC. However, the obvious need to translate this protection to the clinical setting has not materialised largely due to the disconnect between preclinical and clinical studies. Discussion points included how to adapt preclinical animal studies to mirror the patient presenting with an acute myocardial infarction, as well as how to refine patient selection in clinical studies to account for co-morbidities and ongoing therapy. These latter scenarios can modify cytoprotective signalling and need to be taken into account to allow for a more robust outcome when powered appropriately. The workshop also discussed the potential for RIC in other disease settings including ischaemic stroke, cardio-oncology and COVID-19. The workshop, therefore, put forward specific classifications which could help identify so-called responders vs. non-responders in both the preclinical and clinical settings.

9th Hatter Biannual Meeting: position document on ischaemia/reperfusion injury, conditioning and the ten commandments of cardioprotection.

In the 30 years since the original description of ischaemic preconditioning, understanding of the pathophysiology of ischaemia/reperfusion injury and concepts of cardioprotection have been revolutionised. In the same period of time, management of patients with coronary artery disease has also been transformed: coronary artery and valve surgery are now deemed routine with generally excellent outcomes, and the management of acute coronary syndromes has seen decade on decade reductions in cardiovascular mortality. Nonetheless, despite these improvements, cardiovascular disease and ischaemic heart disease in particular, remain the leading cause of death and a significant cause of long-term morbidity (with a concomitant increase in the incidence of heart failure) worldwide. The need for effective cardioprotective strategies has never been so pressing. However, despite unequivocal evidence of the existence of ischaemia/reperfusion in animal models providing a robust rationale for study in man, recent phase 3 clinical trials studying a variety of cardioprotective strategies in cardiac surgery and acute ST-elevation myocardial infarction have provided mixed results. The investigators meeting at the Hatter Cardiovascular Institute workshop describe the challenge of translating strong pre-clinical data into effective clinical intervention strategies in patients in whom effective medical therapy is already altering the pathophysiology of ischaemia/reperfusion injury-and lay out a clearly defined framework for future basic and clinical research to improve the chances of successful translation of strong pre-clinical interventions in man.

Inhibition of myocardial reperfusion injury by ischemic postconditioning requires sirtuin 3-mediated deacetylation of cyclophilin D.

RATIONALE: How ischemic postconditioning can inhibit opening of the mitochondrial permeability transition pore (PTP) and subsequent cardiac myocytes death at reperfusion remains unknown. Recent studies have suggested that de-acetylation of cyclophilin D (CyPD) by sirtuin 3 (SIRT3) can modulate its binding to the PTP. OBJECTIVE: The aim of the present study was to examine whether ischemic postconditioning (PostC) might activate SIRT3 and consequently prevent lethal myocardial reperfusion injury through a deacetylation of CyPD. METHODS AND RESULTS: Using hypoxia-reoxygenation (H/R) in H9C2 cells, we showed that SIRT3 overexpression prevented CyPD acetylation, limited PTP opening and reduced cell death by 24%. In vitro modification of the CyPD acetylation status in MEFs by site-directed mutagenesis altered capacity of PTP opening by calcium. Calcium Retention Capacity (CRC) was significantly decreased with CyPD-KQ that mimics acetylated protein compared with CyPD WT (871 ± 266 vs 1193 ± 263 nmoles Ca(2+)/mg protein respectively). Cells expressing non-acetylable CyPD mutant (CyPD-KR) displayed 20% decrease in cell death compared to cells expressing CyPD WT after H/R. Correspondingly, in mice we showed that cardiac ischemic postconditioning could not reduce infarct size and CyPD acetylation in SIRT3 KO mice, and was unable to restore CRC in mitochondria as it is observed in WT mice. CONCLUSIONS: Our study suggests that the increased acetylation of CyPD following myocardial ischemia-reperfusion facilitates PTP opening and subsequent cell death. Therefore ischemic postconditioning might prevent lethal reperfusion injury through an increased SIRT3 activity and subsequent attenuation of CyPD acetylation at reperfusion.

No post-conditioning in the human heart with thrombolysis in myocardial infarction flow 2-3 on admission.

AIMS: Proof-of-concept evidence suggests that mechanical ischaemic post-conditioning (PostC) reduces infarct size when applied immediately after culprit coronary artery re-opening in ST-elevation myocardial infarction (STEMI) patients with thrombolysis in myocardial infarction 0-1 (TIMI 0-1) flow grade at admission. Whether PostC might also be protective in patients with a TIMI 2-3 flow grade on admission (corresponding to a delayed application of the post-conditioning algorithm) remains undetermined. METHODS AND RESULTS: In this multi-centre, randomized, single-blinded, controlled study, STEMI patients with a 2-3 TIMI coronary flow grade at admission underwent direct stenting of the culprit lesion, followed (PostC group) or not (control group) by four cycles of (1 min inflation/1 min deflation) of the angioplasty balloon to trigger post-conditioning. Infarct size was assessed both by cardiac magnetic resonance at Day 5 (primary endpoint) and cardiac enzymes release (secondary endpoint). Ninety-nine patients were prospectively enrolled. Baseline characteristics were comparable between control and PostC groups. Despite comparable size of area at risk (AAR) (38 ± 12 vs. 38 ± 13% of the LV circumference, respectively, P = 0.89) and similar time from onset to intervention (249 ± 148 vs. 263 ± 209 min, respectively, P = 0.93) in the two groups, PostC did not significantly reduce cardiac magnetic resonance infarct size (23 ± 17 and 21 ± 18 g in the treated vs. control group, respectively, P = 0.64). Similar results were found when using creatine kinase and troponin I release, even after adjustment for the size of the AAR. CONCLUSION: This study shows that infarct size reduction by mechanical ischaemic PostC is lost when applied to patients with a TIMI 2-3 flow grade at admission. This indicates that the timing of the protective intervention with respect to the onset of reperfusion is a key factor for preventing lethal reperfusion injury in STEMI patients. CLINICAL TRIAL NUMBER: NCT01483755.

Comparison of the angiographic myocardial blush grade with delayed-enhanced cardiac magnetic resonance for the assessment of microvascular obstruction in acute myocardial infarctions.

BACKGROUND: Both myocardial blush grade (MBG) and cardiac magnetic resonance (CMR) are imaging tools that can assess myocardial reperfusion after primary percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI). OBJECTIVES: We studied the relation between MBG and gadolinium-enhanced CMR for the assessment of microvascular obstruction (MVO) in patients with acute ST-elevated myocardial infarction (STEMI) treated by primary PCI. MATERIAL AND METHODS: MBG was assessed in 39 patients with initial TIMI 0 STEMI successfully treated by PCI, resulting in TIMI 3 flow grade and complete ST-segment resolution. These MBG values were related to MVO determined by CMR, performed between 2 and 7 days after PCI. Left ventricular (LV) volumes were determined at baseline and at 6-month follow-up. RESULTS: No statistical relation was found between MBG and MVO extent at CMR (P = 0.63). Regarding MBG 0 and 1 as a sign of MVO, the sensitivity and specificity of these scores were 53.8 and 75%, respectively. In this study, CMR determined MVO was the only significant LV remodeling predicting factor (beta = 31.8; P = 0.002), whatever the MBG status was. CONCLUSION: MBG underestimates MVO after an optimal revascularization in AMI compared with CMR. This study suggests the superior accuracy of delayed-enhanced magnetic resonance over MBG for the assessment of myocardial reperfusion injury that is needed in clinical trials, where the principal endpoint is the reduction of infarct size and MVO.

Presence and extent of cardiac magnetic resonance microvascular obstruction in reperfused non-ST-elevated myocardial infarction and correlation with infarct size and myocardial enzyme release.

OBJECTIVE: Microvascular obstruction (MO) is a factor of adverse outcome in patients with ST-elevated myocardial infarction (STEMI). We assessed the presence and extent of MO and its relationship with infarct size and left ventricular (LV) functional parameters after acute non-ST-elevated myocardial infarction (NSTEMI). METHODS: Twenty-five patients with first acute NSTEMI underwent a cine and first-pass perfusion cardiac magnetic resonance (CMR) study, with late gadolinium enhancement imaging 72 h after myocardial infarction. RESULTS: MO was detected in 32% of patients, and its extent comprised 0.5-3.1% of the total LV mass (mean 1.9 +/- 1.2%). Patients with MO had a significantly larger infarct size than patients without (14.1 +/- 5.9 vs. 5.3 +/- 4.1% LV mass; p < 0.001). There was no significant difference between both groups for the LV functional parameters and LV ejection fraction (58.5 +/- 6.8 vs. 62.6 +/- 9.6%; p = 0.29). Patients with MO showed a higher troponin I release (570 +/- 364 vs. 148 +/- 103 IU; p = 0.003) and a higher creatine kinase release (29,887 +/- 18,263 vs. 10,287 +/- 5,283 IU; p = 0.007). CONCLUSIONS: In patients with acute NSTEMI, MO has a frequency similar to that observed in patients with STEMI and also correlates with the infarct extent. The prognostic significance on clinical outcome remains to be shown in this specific population.

One hour reperfusion is enough to assess function and infarct size with TTC staining in Langendorff rat model.

BACKGROUND: There is not general agreement concerning the optimal time of reperfusion necessary to assess myocardial function and necrosis on isolated perfused heart model. Nevertheless, the study of cardioprotection (especially, pre- and postconditioning) requires a reliable and standardized assessment of myocardial necrosis. OBJECTIVE: The objective of this study was thus to evaluate whether 1 h of reperfusion was sufficient to assess rat heart viability on Langendorff preparation. Isolated rat hearts (n = 30) underwent 40 min of global normothermic ischemia followed by 60 or 120 min Langendorff reperfusion. In each group, hearts were also randomly assigned into the 2 following sub-groups: postconditioning (PostC, consisting in 2 episodes of 30 s ischemia and 30 s reperfusion at the onset of reperfusion), and control (no intervention). Coronary flow, heart rate, dP/dt and rate-pressure-product were measured. Myocardial necrosis was assessed by TTC staining and LDH, CK release analysis. RESULTS: Our results indicated that heart function tended to slightly decrease between 60 min and 120 min reperfusion. Infarct size was identical at 60 min and 120 min reperfusion, averaging 33-34% of total LV area in controls versus 17% in PostC (p < 0.001 between control and PostC groups). Similarly, the maximum of enzymatic releases (CK and LDH) measured in coronary effluents was at 60 min of reperfusion, followed by a progressive decrease at 90 min and 120 min. As expected, postconditioning limited enzymatic releases whatever the studied time of reperfusion. CONCLUSION: In conclusion, we showed that prolonged reperfusion beyond 60 min was not useful for function assessment and did not change infarct size measurement, on Langendorff rat model of ischemia-reperfusion.

Optimal pressure for low pressure controlled reperfusion to efficiently protect ischemic heart: an experimental study in rats.

Recent work has demonstrated the benefit of low pressure (LP) reperfusion to protect the heart undergoing an ischemic insult. The goal of the present study was to determine the optimal pressure for the application of LP reperfusion. Isolated rats hearts (n = 30) were exposed to 40 minutes of global warm ischemia followed by 70 minutes of reperfusion with a pressure fixed at 100 cm H(2)O (normal pressure [NP] = control group), 85 cm (group LP [low pressure]-85), 70 cm (group LP-70), or 55 cm (group LP-55). Cardiac function was assessed during reperfusion using the Langendorff model. Myocardial necrosis was assessed by measuring lactate dehydrogenase (LDH) and creatine kinase (CK) leakage in the coronary effluents. Functional recovery was progressively and significantly improved with decreased perfusion pressure. Rate-pressure product (RPP) averaged 3765 +/- 408, 6824 +/- 439, and 12,036 +/- 664 mm Hg/min, respectively, among the control, LP-85, and LP-70 groups (P < .001, LP-70 vs other groups). However, RPP collapsed in the LP-55 group. Similarly, necrosis as measured by LDH and CK leakage progressively reduced between LP-100 and LP-70 hearts (P < .01), with a drastic increase in enzyme in the LP-55 group. In conclusion, this study demonstrated that 70 cm H(2)O is an optimal LP to improve postischemic contractile dysfunction and attenuate necrosis during reperfusion.

Optimal time duration for low-pressure controlled reperfusion to efficiently protect ischemic rat heart.

Previous studies have shown the capacity of low-pressure (LP) reperfusion to protect the ischemic heart. The present study sought to determine the optimal time for the application of LP reperfusion. Isolated rat hearts (n = 30) were exposed to 40 minutes of global warm ischemia followed by 70 minutes of reperfusion. Reperfusion was performed under LP (LP = 70 cm H(2)O) for 0 (control group), 5 (group LP-5), 10 (group LP-10), 30 (group LP-30), or 60 (group LP-60) minutes. Following the LP period the hearts were reperfused with normal pressure (100 cm H(2)O) until the end of reperfusion. Cardiac function was assessed during reperfusion using the Langendorff model. Myocardial necrosis was assessed by measuring LDH leakage in the coronary effluents. Functional recovery was reduced among the control and LP-5 groups with rate-pressure products (RPP) averaging 3788 +/- 499 and 5333 +/- 892 mm Hg/min, respectively. RPP was significantly improved in other groups with RPP averaging 7363 +/- 1159, 7441 +/- 863, and 7269 +/- 692 mm Hg/min in LP-10, LP-30, and LP-60 (P < .01). Similarly, necrosis measured by LDH leakage was significantly reduced in LP-10, LP-30, and LP-60 hearts (P < .01). This study demonstrated that LP reperfusion improves postischemic contractile dysfunction and attenuates necrosis when applied for at least 10 minutes.

High energy compound stability during experimental brain death.

The aim of this study was to examine the effect of sudden brain death (BD) on myocardial function and high energy phosphate (HEP) stores. BD was induced by cerebral vessel ligation in six swine (BD group) that were compared to six control swine. At the end of the BD period (3 hours), harvested hearts were stored at 4 degrees C. Myocardial tissue HEP were assessed by: (i) (31)P-NMR spectroscopy of left ventricle for phosphocreatine (PCr), adenosine triphosphate (ATP), inorganic phosphate (Pi) and intracellular pH (pHi), and by (ii) HPLC for ATP, ADP, and AMP levels in left ventricle biopsies. Brain death resulted in a instantaneous major increase in catecholamines (>50-fold, P < .001) and paradoxically a significant progressive decrease in the regional contractility of the left ventricle. After cardioplegia, no significant differences on HEP compounds (ATP/Pi, PCr/Pi, ATP, energetic index) or in pHi were observed between BD and control groups. These data suggest that early heart injury occurring during BD does not seem to be an ischemic phenomenon.

A simple and reliable method to assess heart viability after hypothermic procurement.

Hearts from brain dead pigs (n = 18) were submitted to 0 (group I), 10 (group II), or 20 (group III) minutes of in situ warm ischemia (animal exsanguination). After harvesting, cold cardioplegia solution was perfused in retrograde fashion and initial coronary flow (ICF) measured. After left ventricular energetic indices were measured using NMR spectroscopy, the hearts were transplanted orthotopically. Follow-up was performed over 120 minutes after cardiopulmonary bypass. We observed a progressive decrease in ICF with increased warm ischemia times: 50 +/- 3.4 mL/min per 100 g of tissue in the group I, 36 +/- 7 and 30 +/- 3.5 in groups II and III, respectively (P < .05 and P < .01 versus group I). The ICF strongly correlated with the energetic index (r = 0.76, P < .001) and with posttransplant function of the transplanted heart. These data showed that measurement of initial coronary flow after cardioplegia was a reliable test to evaluate cardiac graft viability before transplantation.

[Postconditioning: lethal reperfusion injury as a therapeutic target]. / Postconditionnement: la nécrose de reperfusion comme cible thérapeutique.

Acute myocardial infarction is the leading cause of morbidity and mortality in western countries. Ischemic postconditioning, that consists of repeated brief episodes of ischemia-reperfusion performed just after reflow following a prolonged ischemic insult, dramatically reduces infarct size. Recent data indicate that it might involve the activation of the PI3-kinase-Akt-eNOS signalling pathway and inhibition of the opening of the permeability transition pore. A recent clinical study demonstrated that postconditioning protects the human heart. Further research is needed to find new pharmacological agents that would mimick postconditioning in order to treat all patients with ongoing acute myocardial infarction.

The apoptotic members CD95, BclxL, and Bcl-2 cooperate to promote cell migration by inducing Ca(2+) flux from the endoplasmic reticulum to mitochondria.

Metalloprotease-processed CD95L (cl-CD95L) is a soluble cytokine that implements a PI3K/Ca(2+) signaling pathway in triple-negative breast cancer (TNBC) cells. Accordingly, high levels of cl-CD95L in TNBC women correlate with poor prognosis, and administration of this ligand in an orthotopic xenograft mouse model accelerates the metastatic dissemination of TNBC cells. The molecular mechanism underlying CD95-mediated cell migration remains unknown. Here, we present genetic and pharmacologic evidence that the anti-apoptotic molecules BclxL and Bcl-2 and the pro-apoptotic factors BAD and BID cooperate to promote migration of TNBC cells stimulated with cl-CD95L. BclxL was distributed in both endoplasmic reticulum (ER) and mitochondrion membranes. The mitochondrion-localized isoform promoted cell migration by interacting with voltage-dependent anion channel 1 to orchestrate Ca(2+) transfer from the ER to mitochondria in a BH3-dependent manner. Mitochondrial Ca(2+) uniporter contributed to this flux, which favored ATP production and cell migration. In conclusion, this study reveals a novel molecular mechanism controlled by BclxL to promote cancer cell migration and supports the use of BH3 mimetics as therapeutic options not only to kill tumor cells but also to prevent metastatic dissemination in TNBCs.

The SR/ER-mitochondria calcium crosstalk is regulated by GSK3ß during reperfusion injury.

Glycogen synthase kinase-3ß (GSK3ß) is a multifunctional kinase whose inhibition is known to limit myocardial ischemia-reperfusion injury. However, the mechanism mediating this beneficial effect still remains unclear. Mitochondria and sarco/endoplasmic reticulum (SR/ER) are key players in cell death signaling. Their involvement in myocardial ischemia-reperfusion injury has gained recognition recently, but the underlying mechanisms are not yet well understood. We questioned here whether GSK3ß might have a role in the Ca(2+) transfer from SR/ER to mitochondria at reperfusion. We showed that a fraction of GSK3ß protein is localized to the SR/ER and mitochondria-associated ER membranes (MAMs) in the heart, and that GSK3ß specifically interacted with the inositol 1,4,5-trisphosphate receptors (IP3Rs) Ca(2+) channeling complex in MAMs. We demonstrated that both pharmacological and genetic inhibition of GSK3ß decreased protein interaction of IP3R with the Ca(2+) channeling complex, impaired SR/ER Ca(2+) release and reduced the histamine-stimulated Ca(2+) exchange between SR/ER and mitochondria in cardiomyocytes. During hypoxia reoxygenation, cell death is associated with an increase of GSK3ß activity and IP3R phosphorylation, which leads to enhanced transfer of Ca(2+) from SR/ER to mitochondria. Inhibition of GSK3ß at reperfusion reduced both IP3R phosphorylation and SR/ER Ca(2+) release, which consequently diminished both cytosolic and mitochondrial Ca(2+) concentrations, as well as sensitivity to apoptosis. We conclude that inhibition of GSK3ß at reperfusion diminishes Ca(2+) leak from IP3R at MAMs in the heart, which limits both cytosolic and mitochondrial Ca(2+) overload and subsequent cell death.

Tissue Doppler imaging differentiates transmural from nontransmural acute myocardial infarction after reperfusion therapy.

BACKGROUND: The evaluation of transmural extent of necrosis after acute myocardial infarction remains a major problem in clinical practice. We sought to determine whether color M-mode tissue Doppler imaging (TDI) could differentiate transmural from nontransmural myocardial infarction. METHODS AND RESULTS: Twenty-one anesthetized open-chest dogs underwent 90 or 120 minutes of left anterior descending coronary artery occlusion followed by 180 minutes of reperfusion. The transmural extension of infarct was measured by triphenyltetrazolium chloride (TTC) staining. Segment shortening in the endocardium and epicardium of the anterior and posterior walls was assessed by sonomicrometry. Regional myocardial blood flow was measured by radioactive microspheres. TDI was obtained from an epicardial short-axis view. We calculated systolic and diastolic velocities within the endocardium and epicardium of myocardial walls and the subsequent myocardial velocity gradient (MVG). TTC staining could identify 2 groups according to the transmural extent of necrosis: 15 dogs had a nontransmural (NT) necrosis (42+/-3% of wall thickness), and 6 dogs developed a transmural (T) infarct (81+/-4% of wall thickness). In both groups, ischemia resulted in a significant and similar reduction in endocardial and epicardial velocities, with a resulting low systolic MVG in the anterior wall (0.10+/-0.07 in NT and 0.10+/-0.08 s(-1) in T). At 60 minutes of reperfusion, systolic MVG failed to change significantly in the transmural group (-0.20+/-0.09 s(-1)). In contrast, it increased significantly after reflow in the NT group compared with ischemic values (-0.99+/-0.20 versus 0.10+/-0.07 s(-1), P:<0.05). CONCLUSIONS: TDI can differentiate transmural from nontransmural myocardial infarction early after reperfusion.

Assessment of nonuniformity of transmural myocardial velocities by color-coded tissue Doppler imaging: characterization of normal, ischemic, and stunned myocardium.

BACKGROUND: Transmural myocardial contractile performance is nonuniform across the different layers of the left ventricular wall. We evaluated the accuracy of color M-mode tissue Doppler imaging (TDI) to assess the transmural distribution of myocardial velocities and to quantify the severity of dysfunction induced by acute ischemia and reperfusion in the inner and outer myocardial layers. METHODS AND RESULTS: Thirteen open-chest dogs underwent 15 minutes of left anterior descending coronary artery occlusion followed by 120 minutes of reperfusion. M-mode TDI was obtained from an epicardial short-axis view. Systolic velocities were calculated within endocardium and epicardium of the anterior and posterior walls. Regional myocardial blood flow was assessed by radioactive microspheres. Segment shortening was measured by sonomicrometry in endocardium and epicardium of both the anterior and posterior walls. At baseline, endocardial velocities were higher than epicardial velocities, resulting in an inner/outer myocardial velocity gradient. Ischemia caused a significant and comparable reduction in endocardial and epicardial systolic velocities in the anterior wall with the disappearance of the velocity gradient. Systolic velocities significantly correlated with segment shortening in both endocardium and epicardium during ischemia and reperfusion. In the first minutes after reflow, endocardial velocities showed a greater improvement than epicardial velocities, and the velocity gradient resumed although to a limited extent, indicative of stunning. CONCLUSIONS: TDI is an accurate method to assess the nonuniformity of transmural velocities and may be a promising new tool for quantifying ischemia-induced regional myocardial dysfunction.

Tissue kallikrein is required for the cardioprotective effect of cyclosporin A in myocardial ischemia in the mouse.

Clinical and experimental studies suggest that pharmacological postconditioning with Cyclosporin A (CsA) reduces infarct size in cardiac ischemia and reperfusion. CsA interacts with Cyclophilin D (CypD) preventing opening of the mitochondrial permeability transition pore (mPTP). Tissue kallikrein (TK) and its products kinins are involved in cardioprotection in ischemia. CypD knockout mice are resistant to the cardioprotective effects of both CsA and kinins suggesting common mechanisms of action. Using TK gene knockout mice, we investigated whether the kallikrein-kinin system is involved in the cardioprotective effect of CsA. Homozygote and heterozygote TK deficient mice (TK(-/-), TK(+/-)) and wild type littermates (TK(+/+)) were subjected to cardiac ischemia-reperfusion with and without CsA postconditioning. CsA reduced infarct size in TK(+/+) mice but had no effect in TK(+/-) and TK(-/-) mice. Cardiac mitochondria isolated from TK(-/-) mice had indistinguishable basal oxidative phosphorylation and calcium retention capacity compared to TK(+/+) mice but were resistant to CsA inhibition of mPTP opening. TK activity was documented in mouse heart and rat cardiomyoblasts mitochondria. By proximity ligation assay TK was found in close proximity to the mitochondrial membrane proteins VDAC and Tom22, and CypD. Thus, partial or total deficiency in TK induces resistance to the infarct size reducing effect of CsA in cardiac ischemia in mice, suggesting that TK level is a critical factor for cardioprotection by CsA. TK is required for the mitochondrial action of CsA and may interact with CypD. Genetic variability in TK activity has been documented in man and may influence the cardioprotective effect of CsA.

Quantitation of reperfused myocardial infarction by Gd-DOTA-enhanced magnetic resonance imaging. An experimental study.

Because there is evidence that myocardial infarct size is modified by coronary artery reperfusion, an ex vivo experimental model of myocardial infarction was developed to determine the influence of the timing of gadolinium-tetraazacyclododecane tetraacetic acid (Gd-DOTA)-enhanced magnetic resonance imaging (MRI) on the accuracy of infarct size quantitation. Eighteen dogs underwent a 2-hour coronary occlusion followed by 1 (n = 6), 6 (n = 6), or 48 (n = 6) hours of reperfusion. Gd-DOTA was injected 10 minutes before the dogs were killed. T1 (SE 250/26) and T2 (SE 1500/78) weighted images were performed on excised hearts. Gd-DOTA concentration was measured in myocardium by atomic emission spectrometry, and correlated with myocardial blood flow evaluated by radioactive microspheres. All dogs presented with myocardial infarction (mean size 20.4% +/- 3.1% of the left ventricle), and a corresponding area of increased signal intensity on T1-weighted MR images. In none of the three groups did the area of high signal intensity correlate with the ischemic area. By contrast, after 6 and 48 hours of reperfusion, the high signal intensity area (17.9% +/- 2.4%) closely matched the area of nonreversible jeopardized tissue (16.4% +/- 2.5%), as determined on tetrazolium-stained heart slices. Although a noreflow phenomenon was observed in the jeopardized tissue, Gd-DOTA concentration was higher in the subendocardial central ischemic zone than in normally perfused myocardium. Gd-DOTA imaging enhancement seems to be the consequence of a delayed clearance of the agent from the injured tissue. Gd-DOTA-enhanced MRI accurately quantitates the size of reperfused myocardial infarction on the ex vivo heart for more than 6 hours after the beginning of reperfusion. It remains to be determined whether the in vitro results obtained here can be applied to assess the myocardial infarct size in vivo.

Biphasic response after brain death induction: prominent part of catecholamines release in this phenomenon.

BACKGROUND: The physiopathology of hemodynamic instability that occurs after brain death remains unknown. The aim of this study was to examine the initial response to brain death induction. METHODS: After anesthesia and monitoring, 16 pigs were randomized into a control group (C, n = 8) and a brain death group (BD, n = 8). We inflated a subdural catheter balloon to induce brain death. We analyzed hemodynamic and plasmatic biochemical data for 180 minutes after brain death induction. Energetic compounds were measured. We expressed the results in comparison with the C group. RESULTS: The C group remained stable. One minute after brain death, the Cushing reflex appeared, with a hyperdynamic response to plasma catecholamines levels increasing (norepinephrine and epinephrine, 3.1-fold, p = 0. 02, and 3.8-fold, p = 0.07, respectively). After a return to baseline, we recorded a second hyperdynamic profile 120 minutes later. At this time, a second peak of catecholamines appeared (6. 3-fold, p = 0.04, and 9.1-fold, p = 0.02, concerning norepinephrine and epinephrine). At the same time, we observed brief myocardial lactate production (+175%, p < 0.01), with a rise of troponine I (+64%, p = 0.03). The energetic index was similar in both groups: 0. 85 (+/-0.02) in the C group vs 0.87 (+/-0.02) in the BD group. CONCLUSIONS: In this model, biphasic plasmatic catecholamine release appears to primarily explain the physiopathology of the hemodynamic response to brain death induction.