Integrin-Linked Kinase Activation Prevents Ventricular Arrhythmias Induced by Ischemia/Reperfusion Via Inhibition of Connexin 43 Remodeling.

Ischemia reperfusion (I/R)-induced arrhythmia is a serious complication in patients with cardiac infarction. Remodeling of connexin (Cx) 43, manifested as phosphorylation, contributes significantly to arrhythmogenesis. Integrin-linked kinase (ILK) attenuated ventricular remodeling and improved cardiac function in rats after myocardial infarction. We hypothesized that ILK, through Cx43 phosphorylation, would be protective against I/R-induced ventricular arrhythmias. Our study showed that I/R-induced ventricular arrhythmias were attenuated by an ILK agonist LPTP and worsened by the ILK inhibitor Cpd22. I/R disrupted Cx43 distribution, but it was partially normalized in the presence of LPTP. Compared with I/R, the phosphorylation of Akt was increased significantly after pretreatment with LPTP. The increase in phosphorylated Akt was physiologically significant because, in the presence of the Akt inhibitor MK2206, the protective effects of LPTP were blocked. This indicated that ILK activation prevented I/R-induced-ventricular arrhythmia, an effect potentially related to inhibition of Cx43 remodeling via Akt activation.

Role of NADPH oxidase and xanthine oxidase in mediating inducible VT/VF and triggered activity in a canine model of myocardial ischemia.

BACKGROUND: Ventricular tachycardia or fibrillation (VT/VF) of focal origin due to triggered activity (TA) from delayed afterdepolarizations (DADs) is reproducibly inducible after anterior coronary artery occlusion. Both VT/VF and TA can be blocked by reducing reactive oxygen species (ROS). We tested the hypothesis that inhibition of NADPH oxidase and xanthine oxidase would block VT/VF. METHODS: 69 dogs received apocynin (APO), 4 mg/kg intraveneously (IV), oxypurinol (OXY), 4 mg/kg IV, or both APO and OXY (BOTH) agents, or saline 3 h after coronary occlusion. Endocardium from ischemic sites (3-D mapping) was sampled for Rac1 (GTP-binding protein in membrane NADPH oxidase) activation or standard microelectrode techniques. Results (mean±SE, * p<0.05): VT/VF originating from ischemic zones was blocked by APO in 6/10 *, OXY in 4/9 *, BOTH in 5/8 * or saline in 1/27; 11/16 VT/VFs blocked were focal. In isolated myocardium, TA was blocked by APO (10(-6) M) or OXY (10(-8) M). Rac1 levels in ischemic endocardium were decreased by APO or OXY. CONCLUSION: APO and OXY suppressed focal VT/VF due to DADs, but the combination of the drugs was not more effective than either alone. Both drugs inhibited ischemic Rac1 with inhibition by OXY suggesting ROS-induced ROS. The inability to totally prevent VT/VF suggests that other mechanisms also contribute to ischemic VT.

Ca2+/calmodulin-dependent protein kinase II increases the susceptibility to the arrhythmogenic action potential alternans in spontaneously hypertensive rats.

Action potential duration alternans (APD-ALT), defined as long-short-long repetitive pattern of APD, potentially leads to lethal ventricular arrhythmia. However, the mechanisms of APD-ALT in the arrhythmogenesis of cardiac hypertrophy remain undetermined. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is known to modulate the function of cardiac sarcoplasmic reticulum and play an important role in Ca(2+) cycling. We thus aimed to determine the role of CaMKII in the increased susceptibility to APD-ALT and arrhythmogenesis in the hypertrophied heart. APD was measured by high-resolution optical mapping in left ventricular (LV) anterior wall from normotensive Wistar-Kyoto (WKY; n = 10) and spontaneously hypertensive rats (SHR; n = 10) during rapid ventricular pacing. APD-ALT was evoked at significantly lower pacing rate in SHR compared with WKY (382 ± 43 vs. 465 ± 45 beats/min, P < 0.01). These changes in APD-ALT in SHR were completely reversed by KN-93 (1 µmol/l; n = 5), an inhibitor of CaMKII, but not its inactive analog, KN-92 (1 µmol/l; n = 5). The magnitude of APD-ALT was also significantly greater in SHR than WKY and was completely normalized by KN-93. Ventricular fibrillation (VF) was induced by rapid pacing more frequently in SHR than in WKY (60 vs. 10%; P < 0.05), which was also abolished by KN-93 (0%, P < 0.05). Western blot analyses indicated that the CaMKII autophosphorylation at Thr287 was significantly increased in SHR compared with WKY. The increased susceptibility to APD-ALT and VF during rapid pacing in hypertrophied heart was prevented by KN-93. CaMKII could be an important mechanism of arrhythmogenesis in cardiac hypertrophy.

Dynamic alterations of connexin43, matrix metalloproteinase-2 and tissue inhibitor of matrix metalloproteinase-2 during ventricular fibrillation in canine.

The aim of this study is to investigate the dynamic alterations of cardiac connexin 43 (Cx43), matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-2 (TIMP-2) in the setting of different ventricular fibrillation (VF) duration. In this study, thirty-two dogs were randomly divided into sham control group, 8-min VF group, 12-min VF group, and 30-min VF group. Cx43 and phosphorylated Cx43 (p-Cx43) in tissues were detected by western blot and immunofluorescence analysis. MMP-2 and TIMP-2 were detected by western blot and immunohistochemistry analysis. The results showed that Cx43 levels in three VF groups were significantly decreased compared with sham control group. p-Cx43 levels in 12-min and 30-min VF groups were significantly reduced compared with sham control group. The ratio of p-Cx43/Cx43 was also decreased in VF groups. Compared with sham controls, no significant difference was observed between the sham control group and 8-min VF group in MMP-2 level, but MMP-2 level increased in 12-min and 30-min VF groups. The ratios of MMP-2/TIMP-2 were higher in VF groups, and were correlated with the duration of VF. A remarkable correlation was observed between the ratio of p-Cx43/Cx43 and MMP-2/TIMP-2 (r = -0.93, P < 0.01). In conclusion, the alteration of Cx43 and/or p-Cx43 levels and the imbalance of MMP-2 and TIMP-2 may contribute to the initiation and/or persistence of VF. Maneuvers managed to modulate Cx43 level or normalize the balance of MMP-2/TIMP-2 are promising to ameliorate prognosis of VF.

Circulating matrix metalloproteinases in adolescents with hypertrophic cardiomyopathy and ventricular arrhythmia.

BACKGROUND: Myocardial fibrosis is a hallmark of hypertrophic cardiomyopathy (HCM) and a risk factor for ventricular arrhythmia. Fibrosis can be reflected in circulating matrix remodeling protein concentrations. We explored differences in circulating markers of extracellular matrix turnover between young HCM patients with versus without history of serious arrhythmia. METHODS AND RESULTS: Using multiplexed and single ELISA, matrix metalloproteinases (MMPs) 1, 2, 3, and 9; tissue inhibitor of metalloproteinases (TIMPs) 1, 2, and 4; and collagen I carboxyterminal peptide (CICP) were measured in plasma from 45 young HCM patients (80% male patients; median age, 17 years [interquartile range, 15-20]). Participants were grouped into serious ventricular arrhythmia history (VA) versus no ventricular arrhythmia history (NoVA). Differences in MMPs between groups were examined nonparametrically. Relationships between MMPs and ventricular arrhythmia were assessed with linear regression, adjusted for interventricular septal thickness, family history of sudden death, abnormal exercise blood pressure, and implantable cardioverter-defibrillator (ICD). In post hoc sensitivity analysis, age was substituted for ICD. The 14 VA patients were older than 31 NoVA patients (median, 19 versus 17 years; P=0.03). All 14 VA and 12 NoVA patients had an ICD. MMP3 concentration was significantly higher in the VA group (VA median, 12.9 µg/mL [interquartile range, 5.7-16.7 µg/mL] versus NoVA, 5.8 µg/mL [interquartile range, 3.7-10.0 µg/mL]; P=0.01). On multivariable analysis, VA was independently associated with increasing MMP3 (standardized ß, 0.37; P=0.01). Post hoc adjustment for age attenuated this association. CONCLUSIONS: Circulating MMP3 may be a marker of ventricular arrhythmia in adolescent patients with HCM. Because of our role as pediatric providers, we cannot exclude age-related confounding.

Reduction of reperfusion-induced ventricular fibrillation and infarct size via heme oxygenase-1 overexpression in isolated mouse hearts.

Heme oxygenase-1 (HO-1), also known as heat shock protein 32 (hsp-32) is a stress induced cytoprotective protein. The present investigation evaluated the capacity of HO-1 to reduce the incidence of reperfusion-induced ventricular fibrillation (VF) and infarct size. HO-1 transgenic (Tg) mice were generated using a rat HO-1 genomic transgene. Isolated mouse hearts obtained from Tg and nontransgenic (NTg) groups were exposed to 20 min of global ischemia and 120 min of reperfusion. Epicardial ECG was recorded to monitor the incidence of reperfusion-induced VF and at the end of the reperfusion period, detection of HO-1 by immunohistochemistry and measurement of infarct size using the TTC method were carried out. Results shown here provide additional support for cardioprotective effects of HO-1 as evidenced by the reduced infarct size. Moreover, overexpression of the HO-1 efficiently reduced the incidence of ischemia/reperfusion (I/R)-induced VF in HO-1 Tg mice.

Rosiglitazone-induced myocardial protection against ischaemia-reperfusion injury is mediated via a phosphatidylinositol 3-kinase/Akt-dependent pathway.

1. Rosiglitazone is widely used in the treatment of Type 2 diabetes. However, in recent years it has become evident that the therapeutic effects of peroxisome proliferator-activated receptor gamma ligands reach far beyond their use as insulin sensitizers. Recently, the ability of rosiglitazone pretreatment to induce cardioprotection following ischaemia-reperfusion (I/R) has been well documented; however, the protective mechanisms have not been elucidated. In the present study, examined the role of the phosphatidylinositol 3-kinase (PI3-K)/Akt signalling pathway in rosiglitazone cardioprotection following I/R injury. 2. Mice were pretreated with 3 mg/kg per day rosiglitazone for 14 days before hearts were subjected to ischaemia (30 min) and reperfusion (2 h). Wortmannin (1.4 mg/kg, i.p.), an inhibitor of PI3-K, was administered 10 min prior to myocardial I/R. Then, activation of the PI3-K/Akt/glycogen synthase kinase (GSK)-3alpha signalling pathway was examined. The effects of PI3-K inhibition on rosiglitazone-induced cardioprotection were also evaluated. 3. Compared with control rats, the ratio of infarct size to ischaemic area (area at risk) and the occurrence of sustained ventricular fibrillation in rosiglitazone-pretreated rats was significantly reduced (P < 0.05). Rosiglitazone pretreatment attenuated cardiac apoptosis, as assessed by ELISA to determine cardiomyocyte DNA fragmentation. Rosiglitazone pretreatment significantly increased levels of phosphorylated (p-) Akt and p-GSK-3alpha in the rat myocardium. Pharmacological inhibition of PI3-K by wortmannin markedly abolished the cardioprotection induced by rosiglitazone. 4. These results indicate that rosiglitazone-induced cardioprotection in I/R injury is mediated via a PI3-K/Akt/GSK-3alpha-dependent pathway. The data also suggest that modulation of PI3-K/Akt/GSK-3alpha-dependent signalling pathways may be a viable strategy to reduce myocardial I/R injury.

Defibrillation testing and early neurologic outcome.

During implantable cardioverter-defibrillator (ICD) implantation, ventricular defibrillation testing (DFT) is considered a standard procedure. This procedure often requires multiple ventricular fibrillation (VF) inductions. These repeated short episodes of circulatory arrest with global cerebral ischemia may cause neurological damage. In the present study, patients undergoing initial ICD implantation and limited induction of VF for defibrillation safety margin testing were evaluated for pre- and postoperative cognitive and neurologic functions. In addition, the serum neuron specific enolase (NSE) level, which is a biochemical marker of cerebral injury, was evaluated. The study was performed on 16 patients undergoing initial elective transvenous insertion of an ICD. A neurologic examination and cognitive assessment tests were performed 24 to 48 hours before and after ICD. NSE was determined before (NSE 1) and at the end of the surgery (NSE 2), as well as 2 hours (NSE 3), 24 hours (NSE 4), and 48 hours (NSE 5) after implantation. A total of 29 internal shocks (average, 1.8 +/- 0.4) with energy ranging from 14 to 41 J (mean, 20 +/- 5; median, 20 J ) were delivered in the ICD group patients. In one patient, 3 external (50, 200 and 360 J) shocks were required for fast VT induced during ICD lead positioning. The mean duration of VF was 10 +/- 4 seconds and the mean cumulative time in VF was 16 +/- 5 seconds. The mean recovery time between VFs was 5.3 +/- 0.6 minutes. NSE levels were not different from the baseline at any time point in the patients of the group that completed the 48-hour observation period (P > 0.05). The patients did not report any new neurological symptoms after ICD implantation, and repeat examination after the procedure showed no abnormal findings other than those detected in the previous one. There were no statistically significant differences between the preoperative and postoperative scores obtained in the cognitive assessment. Single or two VF inductions and the brief arrest of cerebral circulation during ICD implantation are not associated with permanent neurological injury. However, further studies are needed to confirm this finding.

Effects of protein kinase C activation on cardiac repolarization and arrhythmogenesis in Langendorff-perfused rabbit hearts.

AIMS: Cardiac arrhythmias are still a major cause of mortality in western countries. Currently available antiarrhythmic drugs are limited by a low efficacy and proarrhythmic effects. The role of the protein kinase C (PKC) signalling pathway in arrhythmogenesis is still unclear. The goal of the present study was to test the effects of PKC stimulation on whole heart electrophysiology and its pro-/antiarrhythmic activity. METHODS AND RESULTS: Left ventricular (LV) action potential duration (APD 90%) was determined in 27 Langendorff-perfused rabbit hearts, using Tyrode solution plus the PKC agonist phorbol-12-myristate-13-acetate (PMA; 100 nM) alone (nine rabbits), Verapamil alone (n = 6), or PMA in combination with Verapamil (0.25 mg/L, six rabbits), or bisindolylmaleimide (0.5 microM, n = 6). Intermittent programmed extra-stimulation was performed to induce ventricular arrhythmias. Administration of PMA alone led to a significant shortening of repolarization (APD 90%, 157 +/- 8 vs. 128 +/- 5 ms, P<0.05). Non-sustained ventricular fibrillation (VF) could be induced in seven out of nine animals. After perfusion of Verapamil (156 +/- 6 vs. 169 +/- 4 ms, P>0.05) or bisindolylmaleimide, a selective inhibitor of PKC (136 +/- 4 vs. 146 +/- 4 ms, P>0.05), PMA-induced shortening of repolarization could be inhibited, and induction of VF failed. Verapamil alone did not affect APD and VF could not be induced. CONCLUSIONS: Activation of PKC facilitates induction of VF, which is most likely due to a shortening of repolarization and a prominent calcium influx. These findings demonstrate involvement of the PKC-signalling pathway in arrhythmogenesis.

Nitric oxide synthase isoform inhibition before whole body ischemia reperfusion in pigs: vital or protective?

BACKGROUND: Nitric oxide (NO) is a critical regulator of vascular tone, and signal transduction. NO is produced via three unique synthases (NOS); endothelial (eNOS), and neuronal (nNOS) are both constitutively expressed and inducible (iNOS) produced primarily after stimulation. NO has been implicated during and after ischemia reperfusion injury as both a detrimental and cardioprotective mediator. Since cardiopulmonary resuscitation (CPR) in ventricular fibrillation (VF) is a model of whole body ischemia reperfusion injury, it provides an opportunity to assess the effects of NO from the three NOS isoforms. OBJECTIVE: To determine the differential role of nitric oxide synthase isoforms inhibition in ventricular fibrillation CPR and investigate whether inhibition of the NOS isoforms afford any cardioprotection in this model. METHODS: Thirty-two pigs, weight range 25-35 kg, were assigned to four groups of eight animals each. The animals were randomized to receive (1) N(G)-nitro-L-arginine methyl ester (LNAME), a non-selective endothelial nitric oxide synthase inhibitor, (2) 1-(2-trifluoromethylphenyl) imidazole (TRIM), a selective neuronal NOS inhibitor, (3) aminoguanidine (AMINOG), a selective inducible NOS inhibitor or (4) saline control (Control) in equal volumes, 30 min before induction of ventricular fibrillation (VF). After 3 min VF with no intervention, the animals received standard chest compressions using an automated chest compression device (Thumper) for 15 min. After 18 min of VF, single doses of vasopressin and bicarbonate were given and defibrillation attempted. Hemodynamics, regional blood flows, and echocardiography and were performed, before and after drug infusion, during CPR, and after return of spontaneous circulation (ROSC). RESULTS: ROSC for 3 h occurred in 5/8 (63%), 1/8 (13%), 0/8 (0%), and 6/8 (75%) in Control, LNAME, TRIM, and AMINOG treated animals, respectively. After infusion of LNAME, there was a significant increase from baseline in blood pressure [127+/-6 mmHg versus 169+/-3 mmHg, p<0.002] and coronary perfusion pressure [119+/-6 mmHg versus 149+/-6 mmHg, p<0.003]. During CPR, there were no differences among groups in hemodynamics or regional blood flow. In surviving animals, AMINOG had significantly better myocardial function (left ventricular ejection fraction, fractional shortening, and wall motion score index) than control or LNAME treated animals, and attenuated the post-resuscitation hyperemic response in heart and brain. CONCLUSIONS: Intact basal nNOS activity is vital for survival from whole body ischemia reperfusion injury. iNOS inhibition prior to ischemia reperfusion, protects myocardial function after ROSC and decreases myocardial and brain hyperemic response after ROSC.

Erythropoietin just before reperfusion reduces both lethal arrhythmias and infarct size via the phosphatidylinositol-3 kinase-dependent pathway in canine hearts.

Although recent studies suggest that erythropoietin (EPO) may reduce multiple features of the myocardial ischemia/reperfusion injury, the cellular mechanisms and the clinical implications of EPO-induced cardioprotection are still unclear. Thus, in this study, we clarified dose-dependent effects of EPO administered just before reperfusion on infarct size and the incidence of ventricular fibrillation and evaluated the involvement of the phosphatidylinositol-3 (PI3) kinase in the in vivo canine model. The canine left anterior descending coronary artery was occluded for 90 min followed by 6 h of reperfusion. A single intravenous administration of EPO just before reperfusion significantly reduced infarct size (high dose (1,000 IU/kg): 7.7 +/- 1.6%, low dose (100 IU/kg): 22.1 +/- 2.4%, control: 40.0 +/- 3.6%) in a dose-dependent manner. Furthermore, the high, but not low, dose of EPO administered as a single injection significantly reduced the incidence of ventricular fibrillation during reperfusion (high dose: 0%, low dose: 40.0%, control: 50.0%). An intracoronary administration of a PI3 kinase inhibitor, wortmannin, blunted the infarct size-limiting and anti-arrhythmic effects of EPO. Low and high doses of EPO equally induced Akt phosphorylation and decreased the equivalent number of TUNEL-positive cells in the ischemic myocardium of dogs. These effects of EPO were abolished by the treatment with wortmannin. In conclusion, EPO administered just before reperfusion reduced infarct size and the incidence of ventricular fibrillation via the PI3 kinase-dependent pathway in canine hearts. EPO administration can be a realistic strategy for the treatment of acute myocardial infarction.

Absence of clinically important HERG channel blockade by three compounds that inhibit phosphodiesterase 5--sildenafil, tadalafil, and vardenafil.

Compounds that inhibit phosphodiesterase 5 (PDE5) have been developed for the treatment of erectile dysfunction. Because men with erectile dysfunction frequently have comorbid cardiovascular disease, they may have limited cardiac repolarization reserve and be at risk of arrhythmia if treated with medications that prolong ventricular repolarization. The human ether-a-go-go related gene (HERG) channel is important for repolarization in human myocardium and is a common target for drugs that prolong the QT interval. We studied the ability of three compounds that inhibit PDE5--sildenafil, tadalafil, and vardenafil--to block the HERG channel. Using a whole cell variant of the patch-clamp method, the HERG current was measured in a stably transfected human embryonic kidney cell line expressing the HERG channel. The compounds produced dose-dependent reductions in HERG current amplitude over a concentration range of 0.1 to 100 microM. The IC50 values were 12.8 microM for vardenafil and 33.3 microM for sildenafil. Because the maximum soluble concentration of tadalafil (100 microM) produced only a 50.9% inhibition of the HERG current amplitude, the IC50 value for tadalafil could not be determined with the Hill equation. Tadalafil had the weakest capacity to block the HERG channel, producing a 50.9% blockade at the maximum soluble concentration (100 microM), compared with 86.2% for vardenafil (100 microM) and 75.2% for sildenafil (100 microM). In conclusion, the concentrations of the PDE5 inhibitors required to evoke a 50% inhibition of the HERG current were well above reported therapeutic plasma concentrations of free and total compound. None of the three compounds was a potent blocker of the HERG channel.

Heme oxygenase-1-related carbon monoxide production and ventricular fibrillation in isolated ischemic/reperfused mouse myocardium.

Heme oxygenase-1 (HO-1)-dependent carbon monoxide (CO) production related to reperfusion-induced ventricular fibrillation (VF) was studied in HO-1 wild-type (+/+), heterozygous (+/-), and homozygous (-/-) isolated ischemic/reperfused mouse heart. In HO-1 homozygous myocardium, under aerobic conditions, HO-1 enzyme activity, HO-1 mRNA, and protein expression were not detected in comparison with aerobically perfused wild-type and heterozygous myocardium. In wild-type, HO-1 hetero- and homozygous hearts subjected to 20 min ischemia followed by 2 h of reperfusion, the expression of HO-1 mRNA, protein, and HO-1 enzyme activity was detected in various degrees. A reduction in the expression of HO-1 mRNA, protein, and enzyme activity in fibrillated wild-type and heterozygous myocardium was observed. In reperfused/nonfibrillated wild-type and heterozygous hearts, a reduction in HO-1 mRNA, protein expression, and HO-1 enzyme activity was not observed, indicating that changes in HO-1 mRNA, protein, and enzyme activity could be related to the development of VF. These changes were reflected in the HO-1-related endogenous CO production measured by gas chromatography. In HO-1 knockout ischemic/reperfused myocardium, all hearts showed VF, and no detection in HO-1 mRNA, protein, and enzyme activity was observed. Thus, interventions that are able to increase endogenous CO may prevent the development of VF.

Histochemical and ultrastructural characterisation of an arrhythmogenic substrate in ischemic pig heart.

The aim of the present study was to reveal by enzyme histochemistry and ultrastructural examination the possible anatomic substrate that may be the cause of high susceptibility of the pig heart to ischemia and/or reperfusion-induced severe arrhythmias. The heart of landrace pigs was subjected to 90 min of left coronary occlusion followed by 30 min reperfusion, whereby both conditions elicited arrhythmias and often even ventricular fibrillation. We found for the first time, besides common contractile cardiomyocytes, Purkinje fibers, and "transitional cells" in mid-myocardium. Transitional cells likely correspond to the recently described M cells. Importantly, these cells and Purkinje fibers exhibited reversible ischemia-related subcellular alterations, whereas the majority of contractile cardiomyocytes were irreversibly injured in the area of infarction. In correlation with these findings, glycogen-dependent phosphorylase activity was abolished, whereas it was still persistent in Purkinje fibers and small islands of contractile cardiomyocytes. Moreover, a distinct heterogeneity in the activity of all enzymes selected and subcellular alterations within a border zone were observed. These results suggest that particularly the preserved viability of specialized conducting cells spanning the ventricular wall may account for electrical disturbances that consequently contribute to increased susceptibility of the pig heart to ischemia- and reperfusion-induced severe arrhythmias.

The D allele of the angiotensin-converting enzyme gene and reperfusion-induced ventricular arrhythmias in patients with acute myocardial infarction.

The renin-angiotensin system may play a pivotal role in reperfusion ventricular arrhythmias (RVA). The purpose of this study was to investigate the association between angiotensin-converting enzyme (ACE) gene polymorphism and RVA in patients with acute myocardial infarction (AMI) in a case-control study. Patients who had undergone successful coronary intervention for AMI were enrolled (n= 127, male/female: 97/30, mean age, 62.6 years). The incidence of RVA was continuously monitored by ECG at a coronary care unit. The severity of ventricular arrhythmias was evaluated in terms of the Lown's grade and patients with a high risk of ventricular arrhythmias that may cause sudden cardiac death (Lown's grade > or =2) within 5 h of coronary intervention were defined as cases (n=59), and otherwise as controls (n=68). A receiver operating characteristic curve was used to determine the discriminatory ability of continuous variables and to produce dummy variables for use in a logistic regression analysis. Cases had a significantly higher body mass index, higher maximal levels of serum creatine kinase, and a shorter time preceding coronary intervention than controls. The severity of coronary atherosclerosis was similar between the 2 groups. The frequency distribution of ACE genotypes in cases differed from that in controls (II/ID/DD: 22.0%/52.6%/25.4% vs 44.1%/41.4%/14.7%, p<0.05, by the Mantel-Haenzel chi-square test). The ACE-D allele had additive and dominant effects with regard to the occurrence of significant ventricular arrhythmias after adjusting for other risk factors. The ACE-D allele may play a pivotal role in sudden cardiac death in patients with AMI.

Regulation of ventricular fibrillation by heme oxygenase in ischemic/reperfused hearts.

We have assessed the relationship between reperfusion-induced ventricular fibrillation (VF) and heme oxygenase (HO) mRNA expression using northern blotting, reverse transcription-polymerase chain reaction (RT-PCR), and enzyme activity in isolated working ischemic/reperfused rat hearts. Isolated hearts were subjected to 30 min of global ischemia followed by 120 min of reperfusion. Upon reperfusion with VF, cardiac function was registered (n = 6 in each group), and HO mRNAs and enzyme activities were measured at the end of reperfusion in hearts that showed VF or did not develop VF. The expression of HO-1 mRNA (about fourfold) was observed in ischemic/reperfused nonfibrillated myocardium in comparison with the nonischemic control hearts. In those hearts when VF was developed, the expression of HO-1 mRNA was not observed in comparison with the nonischemic control myocardium. The results measured by RT-PCR and enzyme analysis support the data obtained by northern blotting. In additional studies, we decided to approach the question from a different angle. Thus, the purpose of our work was also to study the role of HO expression and enzyme activity in electrically fibrillated hearts without the ischemic/reperfused protocol. To simulate the period of 10 min of reperfusion-induced VF, hearts were electrically fibrillated, then defibrillated, and perfused for an additional 110 min, and HO-1 mRNA expression and enzyme activities were determined. Thus, electrically induced VF resulted in about 60%, 60%, and 70% reduction in HO-1 mRNA expression, RT-PCR signal intensity, and enzyme activity, respectively, compared with the nonfibrillated ischemic/reperfused group. In conclusion, our data provide evidence that the development of reperfusion-induced VF inhibits HO-1 mRNA expression and enzyme activity in both electrically fibrillated myocardium and ischemic/reperfused fibrillated hearts. The results clearly show that HO-1 mRNA expression and enzyme activity were increased in ischemic/reperfused nonfibrillated myocardium, suggesting that interventions that are able to increase HO-1 mRNA expression and enzyme activity may prevent the development of VF.

Orthogonal analysis of aggravating effects of alpha-, beta-agonists and leukocytes on reperfusion-induced arrhythmias and ventricular fibrillation in Langendorff's rat heart.

AIM: To study the effect of leukocyte (Leu), alpha-agonist (alpha-Ago), and beta-agonist (beta-Ago) on the arrhythmias induced by ischemia and reperfusion to determine which of the 3 factors was the most important one in exacerbating arrhythmias. METHODS: Arrhythmias were induced by the reduction and subsequent resumption of perfused flow in Langendorff's perfused rat hearts. Ventricular tachycardia (VT) and ventricular fibrillation (VF) were recorded on ECG, and the results were orthogonally analyzed. RESULTS: When Leu was present, the incidence of VF induced by ischemia-reperfusion was 80%. The incidence in Leu-depleted hearts was 20%, alpha-Ago and beta-Ago elevated it to 60% and 100%, respectively. The results by orthogonal analysis demonstrated Leu or alpha-Ago+ beta-Ago increased VF incidence. With regard to arrhythmias, arrhythmia score was remarkedly increased by all of 3 factors and various combinations except beta-Ago + Leu. CONCLUSION: Among these 3 factors, Leu was the most important one in facilitating reperfusion-induced arrhythmias.

Unchanged 5'-deiodinating activity during the induction of a nonthyroidal illness.

We investigated the formation of a "nonthyroidal illness" (NTI) in pigs undergoing ventricular fibrillation (VF) and resuscitation. Seven minutes after VF twenty-one pigs received either Epinephrine (E: 45 micrograms/kg B.W.; n = 7), Norepinephrine (NE: 45 micrograms/kg B.W.; n = 7), or Vasopressin (VP: 0.8 U/kg B.W.; n = 7). We determined the serum concentrations (sc) of total T4 (TT4), FT4, total T3 (TT3) and rT3 120 min before, during (t0), and 5, 15, 60 and 120 min after VF. At the end of the observation period we figured out the in-vitro T3-generation (kM, Vmax), the in-vitro rT3-generation, the in-vitro rT3-decomposition (kM, Vmax) and the content of cytosolic sulfhydryls (total sulfhydryls, non-protein bound sulfhydryls) in liver and kidney specimen. Animals not undergoing VF served as controls (C) for parameters measured in the intracellular compartment. TT4- and TT3-sc decreased to 3.3 +/- 0.6 micrograms/dl (p < 0.05, vs. t0) and 15.2 +/- 4.1 ng/dl (p < 0.05, vs t0), resp. FT4-sc remained stable for five minutes (2.63 +/- 0.41 ng/dl) before declining to 1.8 +/- 0.39 ng/dl (p < 0.05, vs. t0). The rT3-sc raised finally to 46.9 +/- 7.3 ng/dl (p < 0.05, vs t0). Iodothyronine sc did not exhibit differences between E-, NE- and VP-treatment. Neither in-vitro T3-generation, nor in-vitro rT3-generation, nor in-vitro rT3-decomposition nor intracellular sulfhydryl content were affected by the events of VF and resuscitation as compared to the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of two strategies for myocardial management during coronary artery operations.

Despite the current trend for using blood cardioplegia, ventricular fibrillation with intermittent ischemia is still used as a strategy to manage the myocardium with impressive results. These two methods of myocardial management were compared in 40 patients undergoing elective coronary artery operations using creatine kinase MB isoforms and troponin T assays. Each patient was randomized to have either cold blood cardioplegia (n = 20) or ventricular fibrillation with intermittent ischemia (n = 20) for myocardial management during the construction of distal anastomoses. Until recently, the comparison of different methods of myocardial management has been hindered by the lack of a specific and sensitive marker of myocardial damage. Analysis of creatine kinase MB isoforms (MB2, cardiac tissue form; MB1, plasma-modified form) and cardiac-specific troponin T (a structural protein) has been shown to improve the sensitivity for the detection of myocardial damage. There were no significant differences between the two groups in age, sex ratio, extent of disease, or left ventricular function. Blood samples for analysis were collected before cross-clamp application and at time intervals up to 48 hours after. Median peak creatine kinase MB2 activity was found to be significantly higher in the blood cardioplegia group compared with ventricular fibrillation (26.5 U/L versus 19.5 U/L, respectively, p = 0.04). Although median peak troponin T concentration was higher in the blood cardioplegia group, the difference failed to reach significance (2.2 ng/mL versus 1.6 ng/mL, p = 0.15).(ABSTRACT TRUNCATED AT 250 WORDS)

[Correlation between reperfusion ventricular fibrillation and postoperative enzyme release in coronary artery bypass grafting].

Twenty patients who had undergone elective coronary artery bypass grafting were divided into two groups according to the cardiac rhythms after aortic declamping. Eight patients had ventricular fibrillation (Vf group) and 12 patients had spontaneous resumption of heart beating in regular sinus rhythm (SPB group). In Vf group, percent CK-MB and absolute value of CK-MB on the first postoperative day showed significant increase compared with those of the SPB group (p < 0.01). Furthermore, duration of ventricular fibrillation after aortic declamping tended to be positively correlated (r = 0.7018) with absolute value of CK-MB on the first postoperative day, although this did not reach statistic significance (p = 0.0523). To the contrary, between the two groups no significant difference was found in percent LDH1, absolute value of LDH1, and ratio of LDH1 to LDH2 on the first and third postoperative day. It is suggested that ventricular fibrillation after aortic declamping plays a crucial role in increasing postoperative CK-MB level, and its duration is presumably correlated with the absolute value of CK-MB on the first postoperative day.