Adenosine preconditioning reduces both pre and postischemic arrhythmias in human myocardium

Role of Calcium Channel Blockers in Myocardial Preconditioning

Coronary heart disease is the leading cause of mortality and morbidity worldwide. The effects of coronary heart disease are usually attributable to the detrimental effects of acute myocardial ischaemia-reperfusion injury. Newer strategies such as ischaemic or pharmacological preconditioning have been shown to condition the myocardium to ischaemia-reperfusion injury and thus reduce the final infarct size. This review investigates the role of calcium channel blockers in myocardial preconditioning. Additionally, special attention is given to nicorandil whose mechanism of action may be associated with the cardioprotective effects of preconditioning. There are still many uncertainties in understanding the role of these agents in preconditioning, but future research in this direction will certainly help reduce coronary heart disease.

Pre-infarction angina and outcomes in non-ST-segment elevation myocardial infarction: data from the RICO survey

Background

The presence of pre-infarction angina (PIA) has been shown to confer cardioprotection after ST-segment elevation myocardial infarction (STEMI). However, the clinical impact of PIA in non-ST-segment elevation myocardial infarction (NSTEMI) remains to be determined.

Methods and Results

From the obseRvatoire des Infarctus de Côte d'Or (RICO) survey, 1541 consecutive patients admitted in intensive care unit with a first NSTEMI were included. Patients who experienced chest pain <7 days before the episode leading to admission were defined as having PIA and were compared with patients without PIA. Incidence of in-hospital ventricular arrhythmias (VAs), heart failure and 30-day mortality were collected. Among the 1541 patients included in the study, 693 (45%) patients presented PIA. PIA was associated with a lower creatine kinase peak, as a reflection of infarct size (231(109–520) vs. 322(148–844) IU/L, p<0.001) when compared with the group without PIA. Patients with PIA developed fewer VAs, by 3 fold (1.6% vs. 4.0%, p = 0.008) and heart failure (18.0% vs. 22.4%, p = 0.040) during the hospital stay. Overall, there was a decrease in early CV events by 26% in patients with PIA (19.2% vs. 25.9%, p = 0.002). By multivariate analysis, PIA remained independently associated with less VAs.

Conclusion

From this large contemporary prospective study, our work showed that PIA is very frequent in patients admitted for a first NSTEMI, and is associated with a better prognosis, including reduced infarct size and in hospital VAs. Accordingly, protecting the myocardium by ischemic or pharmacological conditioning not only in STEMI, but in all type of MI merits further attention.

Clinical study of the electrophysiological effects of ischemic post-conditioning in patients with acute myocardial infarctions

BACKGROUND

Ischemic "pre"-conditioning has been shown to have antiarrhythmic effects. The aim of this study was to investigate whether ischemic "post"-conditioning (post-CON) also has antiarrhythmic effects in ST-segment elevation myocardial infarction (STEMI) patients undergoing coronary angioplasty (PCI) as a clinical model of post-CON.

METHODS AND RESULTS

A total of 61 patients suffering from an acute myocardial infarction (AMI) were included. The QT dispersion (QTd) was measured before each balloon inflation (BI) and after deflation (BD) during PCI. The hemodynamic parameters and electrocardiogram were also assessed during PCI. All data were analyzed using a logistic regression analysis. A total of 36 of 61 STEMI patients could be analyzed according to the protocol. The QTd shortened significantly as the BI and BD were repeated (p<0.05). Prior to the PCI, frequent premature ventricular contractions (PVCs) were observed in 5 patients, and the PVCs were remarkably suppressed or disappeared entirely as the BI and BD were repeated. Non-sustained ventricular tachycardia was observed prior to the PCI in 2 patients; this also disappeared as the BI and BD were repeated. Ventricular fibrillation (VF) occurred in 1 patient prior to PCI, necessitating D-C cardioversion. After repeating the BI and BD during PCI, VF no longer recurred.

CONCLUSIONS

In the majority of the AMI patients studied, post-CON exhibited significant antiarrhythmic effects as assessed by the change in the QTd. The ventricular dysarrhythmias were also suppressed during the PCI.

EFFECTS OF ISCHEMIC PRECONDITIONING ON RAT LUNG: ROLE OF NITRIC OXIDE

Recent studies suggest that ischemic preconditioning (IP) of the lung may have a protective effect in ischemia-reperfusion (I/R) injury. The purpose of the present study was to investigate the preconditioning hypothesis in rat pulmonary vascular bed and to examine the role of nitric oxide (NO) in IP. Isolated rat lung was perfused with Krebs-Henseleit solution containing indomethacin at a constant flow rate and perfusion pressure changes was recorded by a pressure transducer. In rat pulmonary vascular bed, 2 hours of hypothermic ischemia significantly attenuated histamine-induced vasodilator responses without affecting sodium nitroprusside (SNP) vasodilation when compared to sham values. However, 2 cycles of 5 minutes of ischemia and reperfusion that were applied prior to 2 hours of ischemia (IP protocol) prevented the attenuation of histamine-induced vasodilation. On the other hand, IP failed to prevent pulmonary edema after ischemia. Histopathological examination of rat lungs demonstrated that IP was able to protect endothelial cells and type II pneumocytes in lung. Moreover, in IP group, malondialdehyde (MDA) contents of the lung tissue were significantly lower and tissue glutathione (GSH) contents were significantly higher than those in I/R group. Administration of NO synthase inhibitor, N(G)-nitro-L-arginine-methyl ester (L-NAME) prior to the IP protocol abolished the protective effects of IP, but not affected the tissue malondialdehyde and glutathione levels. These results suggest that I/R impaired endothelium-dependent vasodilatory response, whereas endothelium-independent SNP-induced responses were preserved in rat pulmonary vascular bed. IP prevented the impairment of pulmonary vascular endothelium-dependent responses, and these effects may be partially mediated by NO.

Association between AMPD1 Gene Polymorphism and Coagulation Factors in Patients with Coronary Heart Disease

The aim of this study was to investigate whether the C34T and G468T variations in the adenosine monophosphate deaminase-1 (AMPD1) gene were associated with intima-media thickness of the carotid and brachial artery, endothelial function of the brachial artery, glucose metabolism, haemostatic variables and cardiac hypertrophy in patients (n = 109) with coronary heart disease. The plasminogen activator inhibitor-1 activity and the von Willebrand factor were higher in the CC homozygote group compared to the CT/TT group (p < 0.05). There were no differences between the groups regarding intima-media complex of the carotid and brachial artery, presence of plaque in the carotid region, flow-mediated dilatation, ejection fraction or dimensions of the heart. In conclusion, there were no differences between the mutant AMPD1 allele carriers and CC homozygotes regarding surrogate values for atherosclerosis, endothelial function, dimensions and ejection fraction of the heart, glucose tolerance and other well-known cardiovascular risk factors, whereas plasminogen activator inhibitor-1 activity and von Willebrand levels were lower in the mutant AMPD1 allele carriers.

The antiarrhythmic effect and clinical consequences of ischemic preconditioning

Potentially hazardous short ischemic episodes increase the tolerance of myocardium to ischemia paradoxically. This condition decreases the infarct area markedly caused by a longer duration of coronary occlusion. This phenomenon is known as 'ischemic preconditioning' and its powerful cardioprotective effect has been shown in experimental and clinical studies. Ischemic preconditioning decreases cardiac mortality markedly by preventing the development of left ventricular dysfunction and ventricular and supraventricular arrhythmias after acute myocardial infarction. Ischemia-induced opening of ATP-sensitive potassium channels and synthesis of stress proteins via activation of adenosine, bradykinin and prostaglandin receptors seem to be the possible mechanisms. By understanding the underlying mechanisms of ischemic preconditioning, it may be possible to develop new pharmacologic agents that cause ischemic preconditioning with antiischemic and antiarrhythmic properties without causing myocardial ischemia.

Organ preconditioning: the past, current status, and related lung studies

Preconditioning (PC) has emerged as a powerful method for experimentally and clinically attenuating various types of organ injuries. In this paper related clinical and basic research issues on organ preconditioning issues were systemically reviewed. Since lung injuries, including ischemia-reperfusion and others, play important roles in many clinical results, including thromboembolism, trauma, thermal injury, hypovolemic and endotoxin shock, reimplantation response after organ transplantation, and many respiratory diseases in critical care. It is of interest to uncover methods, including the PCs, to protect the lung from the above injuries. However, related studies on pulmonary PC are relatively rare and still being developed, so we will review previous literature on experimental and clinical studies on pulmonary PC in the following paragraphs.

AMPD1 (C34T) polymorphism and clinical outcomes in patients undergoing myocardial revascularization

BACKGROUND

C34T variant of adenosine monophosphate deaminase 1 (AMPD1) gene has been associated with a prolonged survival in heart failure and coronary artery disease, hypothetically linked to an enhanced production of adenosine.

DESIGN

Since adenosine administration is a promising approach for the prevention of the ischemia-reperfusion in myocardial revascularization, the aim of this study was to investigate whether the AMPD1 (-) allele is associated with a favorable prognosis after coronary revascularization. In addition, we assessed the association between AMPD1 polymorphism and plasma adenosine levels.

METHODS

We investigated a total of 161 patients receiving coronary revascularization (70 percutaneous transluminal coronary angioplasty and 91 coronary artery bypass graft). They were investigated for a composite endpoint including recurrent angina, non-fatal MI, target vessel revascularization, heart failure and cardiac death. Plasma adenosine was also measured by high-performance liquid chromatography methods on a subset of 25 patients.

RESULTS

During the follow-up period (7.0+/-0.3 months), the overall combined endpoint accounted for 17 events (10 cardiac-related deaths, 6 revascularization procedures and 1 congestive heart failure). The composite endpoint was 9.8% for AMPD1 (-) allele carriers vs. 11.5% for non-carriers (log-rank statistic, p=n.s.). In the logistic analysis only low (</=40%) ejection fraction was an independent predictor of adverse events (p=0.01, OR=3.8, 95% CI 1.3-11.4). Plasma adenosine levels were similar for AMPD1 (-) allele patients (n=7) as compared for AMPD1 (+) allele (n=18) subjects (290.5+/-31.0 vs. 303.3+/-28.5 nM, p=n.s.).

CONCLUSIONS

Our results indicate that AMPD1 (-) allele is not associated with a more favorable outcome after coronary revascularization. Alternative cardioprotective pathways of the AMPD1 gene-involving an enhanced chronic long-term production of adenosine-might be responsible for survival.

Fibrillation in patients subjected to coronary artery bypass grafting

OBJECTIVE

Atrial fibrillation is the most frequently encountered postoperative arrhythmic complication after coronary artery bypass grafting. Ischemic preconditioning has proved a potent endogenous factor in suppressing ischemia-reperfusion-induced arrhythmias. The protective effect of ischemic preconditioning on atrial fibrillation after coronary artery bypass grafting has not been studied. The purpose of the present study was to investigate whether ischemic preconditioning had an effect on postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting.

METHODS

Eighty-five patients undergoing coronary artery bypass grafting were randomized into ischemic preconditioning and control groups. Holter data from 24-hour electrocardiography were collected 1 day before the operation to the second postoperative day. Atrial fibrillation was registered as positive if any atrial fibrillation event occurred.

RESULTS

The overall incidence of postoperative atrial fibrillation and sustained atrial fibrillation was 34.1% and 27.1%, respectively. The occurrence of atrial fibrillation was significantly lower in the ischemic preconditioning group (21.4% in patients undergoing ischemic preconditioning and 46.5% in control subjects, P =.015). Preoperative recent unstable angina did not influence the incidence of atrial fibrillation. Patients with atrial fibrillation had longer intensive care unit stays and compromised postoperative hemodynamic outcomes. Binary logistic regression analysis showed that ischemic preconditioning, preoperative mean heart rate, and postoperative pulmonary capillary wedge pressure were the independent predictors of atrial fibrillation.

CONCLUSIONS

Postcoronary artery bypass grafting atrial fibrillation is associated with more complicated postoperative outcome. Higher preoperative heart rate and postoperative pulmonary capillary wedge pressure were the independent predictors of atrial fibrillation. Recent unstable angina is not related to the occurrence of postcoronary artery bypass grafting atrial fibrillation. Ischemic preconditioning significantly suppresses postcoronary artery bypass grafting atrial fibrillation, suggesting that ischemic preconditioning can be used as an effective prophylactic method for postoperative atrial fibrillation.

Perioperative and postoperative arrhythmia in three-vessel coronary artery disease patients and antiarrhythmic effects of ischemic preconditioning

OBJECTIVE

Sudden cardiac death caused by arrhythmia remains a major unsolved problem after coronary artery bypass grafting (CABG). Ischemic preconditioning (IP) has proved effective in suppressing ischemia reperfusion arrhythmias in animals and humans. The purpose of the present study was to establish whether IP reduces postoperative arrhythmias in three-vessel coronary artery disease patients undergoing CABG.

METHODS

Forty-five patients with stable angina and three main coronary artery stenosis admitted for primary CABG surgery were randomized into an IP and a control group. The IP protocol entailed twice occluding the ascending aorta by cross-clamping for 2 min, followed by 3 min of reperfusion. Electrocardiography was continuously recorded from the day before surgery to the second postoperative day.

RESULTS

During the recording, all patients developed SVES and VES after the operation. The incidences of SVT and ventricular tachycardia (VT) after surgery were 73.3 and 77.8%, respectively. IP significantly reduced VES events per hour during 2h after reperfusion. The SVT and VT incidence and events per hour were significantly lower in the IP group during 2h after reperfusion and 24h later.

CONCLUSIONS

IP significantly reduced VES, SVT, and VT after surgery. The antiarrhythmic effect 24h after surgery indicates a delayed antiarrhythmic IP phenomenon in these patients. These findings would indicate that IP constitutes a potential additional myocardial protective strategy in multi-vessel diseased patients undergoing CABG.

Ischemic preconditioning suppresses ventricular tachyarrhythmias after myocardial revascularization

BACKGROUND

Ventricular fibrillation (VF) and tachycardia (VT) are the common and potential life-threatening complications after CABG. Ischemic preconditioning (IP) has been proved effective in reducing ischemia reperfusion arrhythmia in animals and humans. Whether IP is effective in suppressing postoperative VF/VT in patients with CABG has not been studied.

METHODS AND RESULTS

Eighty-six patients with CABG with stable and unstable 3-vessel disease were equally randomly assigned into an IP and a control group. The patients who received IP received 2 periods of 2-minute ischemia followed by 3-minute reperfusion. Twenty-four-hour electrocardiographic data were collected. IP resulted in fewer cases of VF after declamping (48.8% versus 79.1% in IP and control, P=0.004) and a shorter VF period (2.28+/-0.44 versus 4.41+/-0.51 minutes, P=0.002). The episodes of VT were significantly reduced in patients in the IP group during early reperfusion and 24 hours after reperfusion (0.65+/-0.16 versus 3.71+/-0.46, P=0.000 and 0.07+/-0.04 versus 2.12+/-1.41, P=0.002, respectively). De novo sustained VT occurred in 3 control patients as against none in the IP group after surgery. As a result, IP significantly curtailed the mechanical ventilation period and reduced the need for inotropes.

CONCLUSIONS

IP significantly reduced postoperative VF/VT in patients with CABG with 3-vessel disease. Suppression of VT during early reperfusion and 24 hours after reperfusion suggests early and delayed IP phenomena in patients undergoing CABG surgery.