Nicorandil, a potent cardioprotective agent, reduces QT dispersion during coronary angioplasty

KATP channels are regulators of programmed cell death and targets for the creation of novel drugs against ischemia/reperfusion cardiac injury

BACKGROUND

The use of percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI) is associated with a mortality rate of 5%-7%. It is clear that there is an urgent need to develop new drugs that can effectively prevent cardiac reperfusion injury. ATP-sensitive K+ (KATP ) channel openers (KCOs) can be classified as such drugs.

RESULTS

KCOs prevent irreversible ischemia and reperfusion injury of the heart. KATP channel opening promotes inhibition of apoptosis, necroptosis, pyroptosis, and stimulation of autophagy. KCOs prevent the development of cardiac adverse remodeling and improve cardiac contractility in reperfusion. KCOs exhibit antiarrhythmic properties and prevent the appearance of the no-reflow phenomenon in animals with coronary artery occlusion and reperfusion. Diabetes mellitus and a cholesterol-enriched diet abolish the cardioprotective effect of KCOs. Nicorandil, a KCO, attenuates major adverse cardiovascular event and the no-reflow phenomenon, reduces infarct size, and decreases the incidence of ventricular arrhythmias in patients with acute myocardial infarction.

CONCLUSION

The cardioprotective effect of KCOs is mediated by the opening of mitochondrial KATP (mitoKATP ) and sarcolemmal KATP (sarcKATP ) channels, triggered free radicals' production, and kinase activation.

Effects of nicorandil infusion on ECG parameters in patients with unstable angina pectoris and percutaneous coronary intervention

Background

Percutaneous coronary intervention (PCI) is effective in treating patients with acute coronary syndrome (ACS) but is associated with some serious complications. Nicorandil is an anti‐anginal agent acting to improve microvascular circulation and to increase coronary blood flow. The objective of this article is to evaluate the effects of intracoronary injection followed with continuous intravenous injection of nicorandil on ECG parameters in patients with unstable angina pectoris (UA) undergoing PCI.

Methods

A single‐center, self‐controlled clinical trial was conducted at the Second Hospital of Tianjin Medical University between January 2019 and April 2019. Sixty‐three consecutive patients with UA who received coronary angiography and selective PCI were enrolled. ECG was recorded and analyzed before and 24 hr after nicorandil infusion.

Results

Patients were divided into three groups: control group (n = 23, aged 63.43 ± 12.55 years), short‐term, and prolonged use with nicorandil group (n = 20 and 20, aged 66.45 ± 8.06 years and 65.80 ± 9.49 years, respectively). Clinical characteristics and ECG parameters were similar before PCI among three groups (p > .05). In nicorandil treatment groups, intervals of QTd and Tp‐e in patients post‐PCI were significantly shorter than that in control and pre‐PCI (p < .05).

Conclusions

Nicorandil infusion reduces QTd and Tp‐e interval in patients with UA. Further studies will be needed to determine whether these electrophysiological changes are associated with a reduction of ventricular arrhythmias and improved outcomes.

New advances in perioperative cardioprotection

With the increasing age of the general population, medical conditions necessitating a surgical intervention will increase. Concomitant with advanced age, the prevalence of type 2 diabetes mellitus will also increase. These patients have a two- to three-fold higher risk of occurrence of cardiovascular events and are at higher risk of perioperative myocardial ischemia. This review will discuss recent advances in the field of perioperative cardioprotection and focus specifically on strategies that have aimed to protect the diabetic and the aged myocardium. This review will not deal with potential putative cardioprotective effects of opioids and anesthetic agents, as this is a very broad area that would necessitate a dedicated overview.

Effect of nicorandil on QT dispersion in patients with stable angina pectoris undergoing elective angioplasty: A triple-blind, randomized, placebo-controlled study

Background

Nicorandil leads to the relaxation of fine vascular smooth muscle, and thus causes vasodilatation of major epicardial. Also, it has anti-arrhythmic and cardio-protective effects by improving reperfusion, and ultimately leads to a reduction in microvascular damage caused by percutaneous coronary intervention (PCI).

Objective

The aim of this study was to determine the effect of nicorandil on QT interval dispersion (QTd) in patients with stable angina pectoris during elective angioplasty.

Methods

This triple-blind and randomized clinical trial was performed on patients with stable angina pectoris, candidates for elective angiography referred to Imam Reza and Ghaem hospitals in Mashhad, Iran, between January and October 2016. The patients were randomly assigned to one of two groups receiving nicorandil (60 mg as 20 mg before and 40 mg after PCI) and placebo. All the patients underwent electrocardiography 12 hours before and 12 hours after PCI. The values of maximal corrected QT interval (QTc max) and QTd in these intervals, and the levels of changes in the QTd (QTd difference before angiography and after PCI) were compared between the two groups. Data were analyzed statistically using SPSS version 18 software via Chi-square and Independent-samples t-test.

Results

This study was performed on 90 patients (55 males and 35 females) with a mean age of 58.6±10.8 years, on two groups of 45 people. The two groups were matched for age, body mass index, cardiovascular risk factors and baseline testing. The QTd before angiography had no statistically significant difference between the patients of both groups (control: 77.7±17.1 vs. nicorandil: 80.7±14.2 ms; p=0.371). The QTd after PCI in the nicorandil group was lower than the control group (48.1±14.2 vs. 59.2±15.6 ms; p=0.000). The decrease rate in QTd had a statistically significant difference between the two groups (control: 18.9±11.0 vs. nicorandil: 33.5±9.5 ms; p=0.000).

Conclusions

The results of this study showed that oral administration of nicorandil around the PCI could further reduce QTd following PCI, compared to the control group.

Trial registration

The trial was registered at the Iranian Registry of Clinical Trials (http://www.irct.ir) with the Irct ID: IRCT2016120631159N1

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Cardioprotective Effects of Nicorandil on Coronary Heart Disease Patients Undergoing Elective Percutaneous Coronary Intervention

Background

Nicorandil is a nicotinamide ester commonly prescribed for treatment of patients with coronary heart disease (CHD). In the present study, we aimed to explore the cardioprotective effects of nicorandil on CHD patients undergoing elective percutaneous coronary intervention (PCI).

Material/Methods

One hundred patients with CHD undergoing PCI were randomly divided into a control group (n=48) and a nicorandil group (n=52). Patients in the control group received traditional therapy, and while patients in the nicorandil group received nicorandil before PCI in addition to the traditional therapy. After PCI, all patients underwent coronary angiogram, and TIMI frame count (TFC) was calculated. Plasma levels of cardiac troponin I (cTnI), creatine kinase-MB (CK-MB), myeloperoxidase (MPO), and malondialdehyde (MDA) were determined before and at 6, 18, and 24 h after PCI. Moreover, systolic blood pressure (SBP), mean blood pressure (DBP), heart rate (HR), and left ventricular ejection fractions (LVEF) were recorded before and 3 months after PCI.

Results

There was a significant difference in the rate of no-reflow (P=0.036) between the 2 groups. The blood frames and levels of cTnI, CK-MB, MPO, and MDA in the nicorandil group were significantly decreased compared to the control group (all P<0.05). Moreover, administration of nicorandil markedly decreased SBP, MBP, and HR, but obviously increased LVEF at 3 months after PCI (P<0.05 or P<0.01).

Conclusions

Nicorandil exerts cardioprotective effects on CHD patients undergoing elective PCI by decreasing PCI-related myocardial injury and rate of no-reflow and improvement of LVEF.

Nicorandil Attenuates Reperfusion Injury after Long Cardioplegic Arrest

The cardioprotective efficacy of nicorandil in cardiac surgery was determined using a surgically relevant 4-hr cardioplegic arrest model. Each isolated rabbit heart was parabiotically blood-perfused using a modified Langendorff column. The magnitude of left ventricular developed pressure and rate of change of developed pressure over time were measured before (baseline) and after ischemia. Nicorandil was administered either pre-ischemia, post-ischemia, pre/post-ischemia, or continuously (before, during, and after ischemia). The endothelium of the coronary artery was observed by scanning electron microscopy. Serum myeloperoxidase activities were also measured. Although pretreatment with nicorandil did not affect recovery of developed pressure, administration of nicorandil after ischemia, or before and after ischemia, enhanced the recovery of developed pressure. Serum myeloperoxidase activity was decreased in the pre/post-ischemia and continuous groups. Endothelial reperfusion injury decreased in all nicorandil-treated groups. Administration of nicorandil attenuated ischemia-reperfusion injury of the myocardium and coronary endothelium while ameliorating leukocyte activation. In the event of unexpected prolonged cardioplegic arrest, administration of nicorandil, even just after declamping, may improve cardiac function. However, pre-ischemia administration alone was not helpful in the heart subjected to prolonged cardioplegic arrest.

Nicorandil Versus Nitroglycerin for Symptomatic Relief of Angina in Patients With Slow Coronary Flow Phenomenon: A Randomized Clinical Trial

OBJECTIVE

Patients with the coronary slow flow phenomenon frequently experience angina episodes. The present study aimed to compare the efficacy of nicorandil versus nitroglycerin for alleviation of angina symptoms in slow flow patients.

METHODS

In a single-center, single-blind, parallel-design, comparator-controlled, randomized clinical trial (NCT02254252), 54 patients with slow flow and normal or near-normal coronary angiography who presented with frequent angina episodes were randomly assigned to 1-month treatment with nicorandil 10 mg, 2 times a day (n = 27) or sustained-release glyceryltrinitrate 6.4 mg 2 times a day (n =27). Frequency of angina episodes, pain intensity, and the Canadian Cardiovascular Society (CCS) grading of angina pectoris were assessed at baseline and after 1 month of treatment.

RESULTS

In all, 25 patients in the nicorandil arm and 24 patients in the nitroglycerin arm were analyzed. After 1 month, patients treated with nicorandil had fewer angina episodes (adjusted mean number of episodes per week, nicorandil versus nitroglycerin; 1.68 ± 0.15 vs 2.29 ± 0.15, P = .007, effect size = 14.6%). Patients also reported greater reductions in pain intensity with nicorandil versus nitroglycerin (adjusted mean of self-reported pain score; 3.03 ± 0.29 vs 3.89 ± 0.30, P = .046, effect size = 8.4%). A significantly higher proportion of patients in the nicorandil arm were categorized in CCS class I (76% vs 33.3%, P = .004) or class II (16.0% vs 45.8%, P = .032).

CONCLUSION

In slow flow patients, nicorandil provides better symptomatic relief of angina than nitroglycerin.

Cardioprotective effects of oral nicorandil use in diabetic patients undergoing elective percutaneous coronary intervention

OBJECTIVE

This study sought to evaluate the cardioprotective role of oral nicorandil (a hybrid between the nitrates and adenosine triphosphate [ATP] sensitive potassium channel activators) in diabetic patients undergoing elective percutaneous coronary intervention (PCI).

BACKGROUND

Myocardial injury commonly occurs during PCI. Several agents that mimic ischemic preconditioning could help minimize this phenomenon.

METHODS

One hundred diabetic patients with stable angina were prospectively enrolled, then randomly assigned to receive oral nicorandil: 20 mg once daily (group A, 50 patients) or placebo (group B, 50 patients) 1 week before and 6 months after PCI. Cardiac troponin I (cTnI) and creatine kinase-MB (CK-MB) levels were measured before and 6, 12, and 24 hours post-PCI.

RESULTS

Mean age of the study cohort was 59.8 ± 5.8 years (males = 68%). cTnI level was significantly lower in group A (6 hours: 7.3 ± 0.3 vs. 14.5 ± 0.4 pg/mL; 12 hours: 12.7 ± 0.7 vs. 25.3 ± 0.5 pg/mL; and 24 hours: 7.7 ± 0.5 vs. 15.0 ± 0.4 pg/mL, P < 0.001). After 6 months, the same group showed significantly higher left ventricle ejection fraction (LVEF%), that is, 63.5 ± 7.7% versus 56.5 ± 8.3% (P < 0.05), with a trend toward lower incidence of major adverse cardiac events (MACE).

CONCLUSION

In diabetic patients undergoing elective PCI, nicorandil intake was associated with decreased incidence of PCI-related myocardial injury and improvement of LVEF% after 6 months.

Cardioprotective effects of single oral dose of nicorandil before selective percutaneous coronary intervention

Objective:

Nicorandil, an opener of ATP-sensitive K+ channels, was used to treat angina in patients with coronary artery disease. In this study, we aim to investigate the cardioprotective effects of single oral dose of nicorandil in patients undergoing selective percutaneous coronary intervention (PCI).

Methods:

One hundred and thirty-eight patients with acute coronary syndrome undergoing PCI from July 2011 to October 2012 were randomly divided into control group (group 1, n=47), 10 mg oral nicorandil group (group 2, n=45), and 20 mg oral nicorandil group (group 3, n=46) about 2 hours before procedure, respectively. Cardiac troponin I (cTnI) levels were determined at 20 ~ 24 hours after PCI.

Results:

There was a significant difference in the rate of any cTnI elevation among the three groups (group 1: 36.17%, group 2: 20.00%, group 3: 15.22%, p=0.0176). With respect to the frequency of cTnI elevation ≥3 and 5×the upper limit of normal (ULN), there also had statistical difference among the three groups (17.02% in group 1, 8.89% in group 2, and 4.35% in group 3, respectively for cTnI elevation ≥3× ULN, p=0.0428; 12.77% in group 1, 6.67% in group 2, and 2.17% in group 3, respectively, for cTnI elevation ≥5× ULN, p=0.0487). Logistic regression analysis showed that LVEF (OR=0.915, 95% CI=0.853-0.981) and the use of nicorandil (OR=0.516, 95% CI=0.267-0.996) before PCI were independent protective factors of myocardial injury.

Conclusion:

Single oral dose of nicorandil (10 mg, 20 mg) 2 hours before the PCI procedure could decrease the incidence of peri-procedure myocardial injury and PCI-related myocardial infarction.

Nicorandil suppressed myocardial injury after percutaneous coronary intervention

BACKGROUND

Nicorandil exerts beneficial effects as an adjunctive therapy for patients with ischemic heart disease. This study was designed to assess the effects of nicorandil on the myocardial protective benefits of elective percutaneous coronary intervention (PCI).

METHODS

We randomly divided 49 patients scheduled to undergo elective PCI into two groups, nicorandil and control. Before PCI, the former received an intravenous bolus injection of nicorandil (4 mg), followed by continuous infusion at 6 mg/h for 24 h after intervention. Oral administration of nicorandil was continued until follow-up coronary angiography (CAG). Serial venous blood samples, for measurement of creatine kinase (CK), creatine kinase MB isoform (CK-MB), troponin I (TnI) and myoglobin, were obtained before PCI, and at 0 h, 4 h, 24 h and 48 h after PCI. Left ventricular function and left ventricular wall motion were evaluated by means of contrast ventriculography before PCI and follow-up CAG.

RESULTS

At 24 h after PCI, elevations of cardiac enzymes were significantly suppressed in the nicorandil as compared to the control group; CK (78.1+/-34.9 versus 117.4+/-137.9 U/l, P=0.0141), CK-MB (1.57+/-1.90 versus 2.67+/-4.50 U/l, P=0.0485) and TnI (0.37+/-0.55 versus 0.86+/-1.65 ng/ml, P=0.0101). Regional left ventricular wall motion was significantly improved at follow-up in the nicorandil as compared to the control group.

CONCLUSIONS

Nicorandil suppressed elevations of cardiac enzymes after elective PCI and left ventricular wall motion was also significantly improved at follow-up, suggesting that nicorandil enhances the myocardial protective effect of PCI against angioplasty-related myocardial injury.

QT dispersion and left ventricular function after stent placement in acute myocardial infarction

BACKGROUND

QT dispersion is increased in acute myocardial infarction (AMI), but the relation of QT dispersion to left ventricular (LV) function has not yet been fully elucidated. The purpose of this study was to evaluate the relationship between QT dispersion and LV function in patients with successful coronary stenting in AMI.

METHODS

Seventy five patients with AMI who underwent percutaneous transluminal coronary angioplasty (PTCA) were enrolled in this study. Corrected QT dispersion was measured before, immediately after, 24 h after, 48 h after, and 6 months after PTCA. Left ventricular ejection fraction (LVEF) was evaluated by left ventriculography at 6 months after PTCA.

RESULTS

Corrected QT dispersion at 24 h after and 48 h after PTCA were significantly related to LVEF by univariate analysis (r=-0.282, p<0.05 and r=-0.326, p<0.01, respectively). In multiple regression model, corrected QT dispersion at 24 h after and 48 h after PTCA revealed significant associations with LVEF (R(2)=0.441, coefficient=-0.283, p=0.006 and R(2)=0.411, coefficient=-0.225, p=0.039, respectively), but corrected QT dispersion before, immediately after, and 6 months after PTCA were not associated with LVEF.

CONCLUSIONS

Corrected QT dispersion at 24 h after and 48 h after PTCA in AMI correlate with LVEF at 6 months after PTCA.

Tachyarrhythmias in percutaneous coronary interventions

Accompanying the clear benefits, there are certain risks of tachyarrhythmias in percutaneous coronary interventions (PCI), including serious ventricular arrhythmias and atrial fibrillation (AF). Ventricular arrhythmias may result from excess catheter manipulation, intracoronary dye injection, new ischemic events, or reperfusion. In patients with heart failure such kind of arrhythmias can occur more frequently. Atrial dysfunction, sino-atrial and nodal ischemia, congestive heart failure, sympathetic stimulation, iatrogenic factors are the possible causes of AF especially in patients undergoing primary PCI. Atrial fibrillation, on the other hand, can cause clinical squeal in the setting of a rapid ventricular response or if the loss of atrial systole results in hypotension, as in a patient with mitral stenosis or diastolic ventricular dysfunction. Majority of the ventricular arrhythmias and AF tend to revert spontaneously. However, the special treatment must be given, when necessary.

Continuous Administration of Nicorandil Decreases QT Dispersion During the Chronic Phase of Acute Myocardial Infarction

We previously reported that continuous intravenous (IV) administration of nicorandil (NIC) inhibits QT dispersion (QTd). However, no prior study has evaluated the efficacy of NIC when administered orally to acute myocardial infarction (AMI) patients following continuous IV administration. Thirty patients with anteroseptal infarction in whom revascularization was performed successfully within 6 hours of AMI onset were included in the study and assigned to one of 3 groups: group A (continuous IV administration of NIC), group B (continuous IV and oral administration of NIC), and group C (no treatment with NIC). After 24 hours, QTd in groups A and B was significantly decreased compared to QTd in group C (P < 0.01) (group A, 58.1; group B, 58.2; and group C, 81.3). The QTd obtained 3 months later was significantly shorter in group B subjects who were orally administered NIC, and QTd before percutaneous coronary intervention (PCI) was restored in group A, in which no NIC had been administered orally [group A, 66.7; group B, 54.1; and group C, 73.9; P < 0.05 (group A versus group B) and P < 0.01 (group B versus group C)]. The effects were evaluated by comparing different routes of administration. Continuous IV and subsequent oral administration of NIC inhibited prolongation of QTd, suggesting that these effects may prevent the occurrence of cardiac events during both the acute and chronic phases of AMI.

Nicorandil attenuates NF-kappaB activation, adhesion molecule expression, and cytokine production in patients with coronary artery bypass surgery

Nicorandil (NCR), a KATP channel opener, has been reported to preserve microvascular integrity in patients with reperfused myocardial infarction. We tested the hypothesis that NCR suppresses myocardial ischemia and reperfusion injury via the attenuation of cytokine production. Forty patients who underwent coronary artery bypass graft surgery were studied. The patients were randomly divided into two groups, i.e., the patients with NCR (4-6 mg/h; N group, n = 20) or without NCR (C group, n = 20). Cardiac surgery was performed under anesthesia using fentanyl and propofol. Blood were sampled at the time of induction of anesthesia, pre-cardiopulmonary bypass, 60 min after aortic occlusion, and 60, 120, and 180 min after declamping the aorta. The activation of NF-kappaB, expression of adhesion molecules, and cytokine production were evaluated in blood samples from the control volunteers by flow cytometric analysis with or without lipopolysaccharide (LPS) stimulation in vitro. Serum IL-6 and IL-8 levels in both groups increased 60 min after declamping the aorta compared with the preoperative value (P < 0.001); the increases of these parameters in N group were lower than those in C group (P < 0.05). Serum creatine kinase with muscle and brain subunits and troponin-T levels increased 60 min after declamping the aorta in two groups (P < 0,001), but the increases of both parameters in N group were lower than those in C group (P < 0.05). NF-kappaB activation, CD11b/CD18 expression, and the production of TNF-alpha, IL-8, and IL-6 in monocytes and granulocytes were inhibited by NCR in vitro. NCR suppressed the increase of inflammatory cytokines such as IL-6 and IL-8 levels, and reduced myocardial reperfusion injury. The inhibition on NF-kappaB activation, adhesion molecule expression, and cytokine production may be one of the important mechanisms of myocardial protection of NCR.

Myocardial protective effects of nicorandil during percutaneous coronary intervention in patients with unstable angina

BACKGROUND

The purpose of the study was to prospectively evaluate the protective effect of nicorandil during percutaneous coronary intervention (PCI) in patients with unstable angina (UAP).

METHODS AND RESULTS

Two hundred patients (61+/-10 year-old, male 143) diagnosed with UAP at an emergency medical center were randomly assigned to 2 groups: intravenous isosorbide dinitrate, Group I (n=100), or intravenous nicorandil, Group II (n=100). PCI was performed 12-48 h after infusion of each agent. Serum concentrations of creatine kinase-MB (CK-MB), cardiac troponin T (cTnT), and I (cTnI) were measured before and 6, 12, 24 h after PCI. Patients with non-coronary chest pain, requiring emergency coronary angiogram, temporary pacemaker or glycoprotein IIb/IIIa receptor blocker were excluded. PCI was successfully performed in 96 patients (Group I=54, 61.7+/-8.2 years, 32 males; Group II=42, 60.4+/-11.7 years, 27 males). No significant differences in clinical or coronary angiographic characteristics were observed between the 2 groups. The concentration of CK-MB was elevated in 9 patients (17%) of Group I and 6 (14%) of Group II, cTnT in 16 (30%), 6 (14%) and cTnI in 25 (46%), 9 (21%) after PCI. Elevation of any troponin was less frequent in Group II [28/54 (52%) vs 10/42 (24%) patients, p=0.01]. Major adverse coronary events during the 6-month clinical follow-up occurred in 9 (17%) of Group I and 5 patients of Group II (12%, p=NS). Follow-up echocardiography revealed lower left ventricular ejection fraction in Group I than in Group II (65.4+/-7.2% vs 71.0+/-6.7%, p=0.03).

CONCLUSION

Nicorandil has a myocardial protective effect during PCI in patients with UAP.

Cardiac Preconditioning during Percutaneous Coronary Interventions

Ischemic preconditioning (PC) is a polygenic defensive cellular adaptive phenomenon of the heart to ischemic stress, whereby the heart changes its phenotype to become more resistant to subsequent ischemia. Early and late of PC represent two chronologically and pathophysiologically distinct phases of this phenomenon, which can be recruited pharmacologically. We represent a post hoc analysis examining the late PC-mimetic effects of nitroglycerin (NTG) on peri-procedural myocardial necrosis during percutaneous coronary intervention (PCI). A group of 66 patients presenting with angina were randomized, 24 h prior to a scheduled PCI for single obstructive CAD, to a 4 h pretreatment with intravenous NTG or saline. Measurements of electrocardiographic ST-segment shifts, echocardiographic regional wall motion and angina scores demonstrated that NTG pre-treatment preconditioned the heart by rendering it resistant to ischemia during balloon inflations. NTG-pretreated patients exhibited trends towards lower average peak CK (131.1 vs. 188.6 U/L, P = 0.38) and CK-MB levels (7.1 vs. 12.6 ng/ml, P = 0.40). NTG, however, had no significant impact on the incidence of post-procedural MI or any cardiac enzyme elevation. The exploitation of ischemic and pharmacological PC may prove a useful strategy to confer cardioprotection during high-risk PCI and is worth exploring.

Nicorandil: a review of its use in the management of stable angina pectoris, including high-risk patients

Nicorandil (Adancor, Angicor, Dancor, Nikoril [Europe], Ikorel [Europe and Oceania], Sigmart [Japan, Korea and Taiwan]) is an adenosine triphosphate (ATP)-sensitive potassium (KATP) channel agonist with nitrate-like properties used in the management of stable angina pectoris. With well established monotherapeutic antianginal activity and a beneficial effect (when added to optimal antianginal therapy) on clinical outcomes in high-risk patients with stable angina, twice-daily oral nicorandil is a useful alternative or addition to other antianginal therapy.

Ischaemic preconditioning and outcomes after angioplasty: effects of drug therapy

Ischaemic preconditioning is one of the mechanisms by which human myocardium and human life are protected from ischaemic insults. One of the clinical situations in which we can discuss preconditioning is repetitive coronary occlusions by balloon inflation during elective percutaneous transluminal coronary angioplasty (PTCA) for stable angina pectoris. The severity of myocardial ischaemia assessed by ST-segment elevation or chest pain is less during the second balloon inflation compared with the first, if the duration of the first coronary occlusion is sufficient to precondition the myocardium. Many drugs have been identified that produce a reduction or induction in indices of preconditioning during PTCA. Preconditioning-mimetic drugs include adenosine, bradykinin, nitroglycerin and nicorandil. It is of paramount importance that we investigate and develop preconditioning-mimetic drugs which may enable an increased tolerance to effort angina, limit infarction size in susceptible patients, and decrease the incidence of sudden cardiac death as a result of ventricular tachyarrhythmias.

Nicorandil enhances myocardial tolerance to ischemia without progressive collateral recruitment during coronary angioplasty

Nicorandil, a hybrid nitrate and ATP-sensitive potassium channel opener, has had a preconditioning effect in some coronary angioplasty studies. The present study investigated whether the cardioprotective effects of nicorandil involve coronary collateral function. Thirty-two patients with stable angina pectoris were randomized to receive a 1-min intravenous infusion of nicorandil (100 microg/kg) or normal saline. Five minutes later they underwent three 2-min balloon inflations 5-min apart. The maximum ST-segment elevation (deltaSTmax), the sum of ST-segment elevations in all leads (sigmaST), and the chest pain score were determined at the end of each balloon inflation. The collateral flow index (CFI) was derived from simultaneous measurement of the mean aortic pressure and the coronary wedge pressure obtained from a pressure guidewire during balloon inflation. The deltaSTmax, sigmaST, and chest pain score decreased progressively during the 3 sequential balloon inflations in both groups, and the deltaSTmax and sigmaST were less in the nicorandil group than in the control group during each inflation. The CFI did not change during the 3 inflations in either group and was similar in the 2 groups during each inflation. In conclusion, pretreatment with intravenous nicorandil enhances myocardial tolerance to ischemia without progressive collateral recruitment during coronary angioplasty.

Clinical and therapeutic aspects of congenital and acquired long QT syndrome

The long QT syndrome is characterized by prolongation of the corrected QT (QTc) interval on the surface electrocardiogram. It is associated with precipitation of a polymorphic ventricular tachycardia, torsade de pointes, which may cause sudden death. The syndrome is a disorder of cardiac repolarization caused by the alterations in the transmembrane potassium and sodium currents. Six genetic loci for the congenital forms of the syndrome have been identified; sporadic cases occur because of spontaneous mutations. Acquired causes of the long QT syndrome include drugs, electrolyte imbalance, toxins, marked bradycardia, subarachnoid hemorrhage, stroke, myocardial ischemia, protein-sparing fasting, autonomic neuropathy, and human immunodeficiency virus disease. Clinical symptoms are the result of the precipitation of torsade de pointes and range from such minor symptoms as dizziness to syncope and sudden death. Short-term treatment is aimed at preventing the recurrences of torsade de pointes and includes intravenous magnesium and potassium administration, temporary cardiac pacing, and correction of electrolyte imbalance; rarely, intravenous isoproterenol is indicated. Long-term management includes use of beta-blockers, permanent pacemaker placement, and cardioverter-defibrillator implantation. Asymptomatic patients are treated if under the age of 40 years at the time of diagnosis.