Nicorandil and Long-acting Nitrates: Vasodilator Therapies for the Management of Chronic Stable Angina Pectoris

Effects of Nicorandil, Isosorbide Mononitrate, or Diltiazem on Radial Artery Grafts After CABG: The Randomized ASRAB-Pilot Trial

BACKGROUND

The optimal antispastic treatment after coronary artery bypass grafting using radial artery (RA) grafts is controversial. This clinical trial aimed to generate pilot comparative data on the effects of nicorandil, isosorbide mononitrate, or diltiazem on RA grafts.

METHODS

This was a single-center, randomized, open-label, parallel-group pilot trial. Eligible patients who underwent coronary artery bypass grafting using RA grafts were randomized in a 1:1:1 ratio to receive oral nicorandil (15 mg daily), isosorbide mononitrate (50 mg daily), or diltiazem (180 mg daily) for 24 weeks post-coronary artery bypass grafting. The primary outcome was RA graft failure (modified Fitzgibbon grade B, S, or O) at 1 and 24 weeks, assessed by coronary computed tomography angiography.

RESULTS

Among 150 randomized participants, 149 (mean age, 56.8 years; 13.4% women) with 177 RA grafts were assessed at least once by coronary computed tomography angiography, including 50 participants with 64 RA grafts in the nicorandil group, 50 participants with 57 RA grafts in the isosorbide mononitrate group, and 49 participants with 56 RA grafts in the diltiazem group, respectively. At 1 week post-coronary artery bypass grafting, the RA graft failure rates were lower with nicorandil versus diltiazem (19.4% versus 25.0%; difference, -5.6% [95% CI, -20.6% to 9.3%]) and isosorbide mononitrate versus diltiazem (18.2% versus 25.0%; difference, -6.8% [95% CI, -21.8% to 8.6%]). The RA graft failure rates were slightly higher with nicorandil versus isosorbide mononitrate (19.4% versus 18.2%; difference, 1.2% [95% CI, -13.3% to 15.2%]). At 24 weeks, RA graft failure rates were lower with nicorandil versus diltiazem (16.1% versus 27.8%; difference, -11.7% [95% CI, -26.6% to 3.4%]), and isosorbide mononitrate versus diltiazem (12.5% versus 27.8%; difference, -15.3% [95% CI, -29.8% to -0.2%]), and slightly higher with nicorandil versus isosorbide mononitrate (16.1% versus 12.5%; difference, 3.6% [95% CI, -9.6% to 16.4%]).

CONCLUSIONS

In this pilot trial, treatment with nicorandil or isosorbide mononitrate was associated with a lower RA graft failure rate compared with diltiazem. Larger hypothesis-testing trials are warranted.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04310995.

Preventive effects of nitric oxide donors in contrast-induced nephropathy in patients undergoing coronary artery angiography: an updated systematic review and meta-analysis of 13 randomized controlled trials

BACKGROUND

Contrast-induced nephropathy (CIN) is associated with increased mortality and morbidity in patients undergoing coronary angiography (CAG) and percutaneous coronary intervention (PCI). We aimed to assess the latest evidence on the preventive effects of nitric oxide (NO) donors in CIN patients undergoing CAG/PCI.

METHODS

We conducted a comprehensive systematic review and meta-analysis of RCTs from PubMed, Web of Science, Scopus, Embase, and Cochrane searches until May 5th, 2024. Dichotomous data were pooled using risk ratio (RR), and continuous data were pooled using mean difference (MD), both with a 95% confidence interval (CI), using (R version 4.3).

RESULTS

Our analysis included 13 RCTs encompassing 3,550 patients. NO donors were significantly associated with a decreased incidence of CIN compared to placebo either as an oral administration (RR: 0.33 with 95% CI [0.26, 0.42], P < 0.01) or IV infusions (RR: 0.56 with 95% CI [0.40, 0.78], P < 0.01). Moreover, NO donors were significantly associated with decreased serum creatinine levels compared to placebo either as an oral administration (MD: - 0.07 with 95% CI [- 0.10, - 0.04], P < 0.01) or IV infusions (MD: - 0.07 with 95% CI [- 0.09, - 0.04], P < 0.01). In terms of safety, NO donors were significantly associated with a decreased incidence of major adverse cardiac events (MACE) compared to placebo as an oral administration (RR: 0.64 with 95% CI [0.45, 0.89], P < 0.01). However, there was no significant difference between NO donors as IV infusions and placebo in MACE (RR: 0.68 with 95% CI [0.38, 1.21], P = 0.18). Finally, NO donors were significantly associated with a decreased incidence of all-cause mortality compared to placebo as an oral administration (RR: 0.58 with 95% CI [0.36, 0.94], P = 0.03). Nevertheless, there was no statistically significant difference in all-cause mortality between IV infusions of NO donors and placebo (RR: 1.84 with 95% CI [0.40, 8.52], P = 0.44).

CONCLUSION

NO donors as adjunct therapy are associated with reduced incidence of CIN and decreased serum creatinine levels, either as an oral or IV administration. They were also associated with reduced incidence of MACE, all-cause mortality, and recurrent myocardial infarction as an oral administration, which makes this simple, low-cost intervention an important therapeutic option in patients undergoing CAG/PCI.

Nicorandil antiallodynic activity in a model of neuropathic pain is associated with the activation of ATP-dependent potassium channels and opioidergic pathways, and reduced production of cytokines and neutrophils recruitment in paw, sciatic nerve, and dorsal root ganglia

BACKGROUND

Recently, we demonstrated that nicorandil inhibits mechanical allodynia induced by paclitaxel. In the present study, we evaluated the effect induced by nicorandil in a model of neuropathic pain induced by chronic constriction injury (CCI) in mice. We also investigated putative mechanisms underlying such an effect.

METHODS

CCI was induced by three ligatures of the left sciatic nerve. Mechanical allodynia was evaluated by measuring the paw withdrawal threshold with an electronic von Frey apparatus. Concentrations of cytokines and myeloperoxidase activity were determined in the paw tissue, sciatic nerve, and dorsal root ganglia (DRG).

RESULTS

Oral administration of two doses of nicorandil (150 mg/kg po), but not equimolar doses of nicotinamide or nicotinic acid, attenuated mechanical allodynia induced by CCI. Nicorandil activity was reduced by previous administration of glibenclamide (40 mg/kg) or naltrexone (5 mg/kg or 10 mg/kg). Two doses of nicorandil (150 mg/kg, po) reduced tumor necrosis factor-α, interleukin-1β and interleukin-6, but not CXCL-1, concentrations in the paw tissue of CCI mice. Two doses of nicorandil (150 mg/kg, po) reduced concentrations of all these mediators in the sciatic nerve and DRG. Two doses of nicorandil (150 mg/kg, po) also reduced the myeloperoxidase activity in the paw tissue, sciatic nerve, and DRG.

CONCLUSIONS

Nicorandil exhibits antiallodynic activity in a model of neuropathic pain induced by CCI. Inhibition of cytokines production and reduction of neutrophils recruitment in paw tissue, sciatic nerve, and DRG as well as activation of ATP-dependent potassium channels and opioidergic pathways, underlie nicorandil antiallodynic activity.

The clinical value of β-blockers in patients with stable angina

Stable angina, one manifestation of chronic coronary syndrome (CCS), is characterised by intermittent episodes of insufficient blood supply to the myocardium, provoking symptoms of myocardial ischaemia, particularly chest pain. These attacks usually occur during exercise or stress. Anti-ischaemic drugs are the mainstay of pharmacologic management of CCS with symptoms of angina. β-blockers reduce heart rate and myocardial contractility, thus reducing myocardial oxygen consumption. These drugs have been shown to ameliorate the frequency of anginal attacks and to improve exercise capacity in these patients. Current management guidelines include β-blockers as a first-line management option for most patients with CCS and symptoms of myocardial ischaemia, alongside dihydropyridine calcium channel blockers (CCB). The presence of comorbid angina and heart failure is a strong indication for starting with a β-blocker. β-blockers are also useful in the management of angina symptoms accompanied by a high heart rate, hypertension (with or without a renin-angiotensin-aldosterone-system [RAS] blocker or CCB), or microvascular angina (with a RAS blocker and a statin). A β-blocker is not suitable for a patient with low heart rate (<50 bpm), although use of a β-blocker may be supported by a pacemaker if the β-blocker is strongly indicated) and should be used at a low dose only in patients with low blood pressure.

Mechanism of action and neuroprotective role of nicorandil in ischemic stroke

Nicorandil is a dual mechanism anti-anginal agent that acts as a nitric oxide (NO) donor and a potassium (K+) channel opener. Recent studies have evaluated the effect of nicorandil on ischemic stroke. Neurons have a low tolerance to hypoxia and therefore the brain tissue is significantly vulnerable to ischemia. Current approved treatments for ischemic stroke are tissue plasminogen activators and clot retrieval methods. The narrow therapeutic time window and lack of efficacy in restoring the dying neurons urge researchers to develop an alternative approach. In the terminal stages of anoxia, K+ channels induce hyperpolarization in various types of neuronal cells, leading to decreased neuronal activity and the preservation of the brain's energy. Nicorandil can open these K+ channels and sustain the hyperpolarization phase, which may have a neuroprotective effect during hypoxia. Additionally, we review how nicorandil can improve overall stroke outcomes through its anti-inflammatory, anti-oxidative, and edema-reducing effects. One of the major components evaluated in stroke patients is blood pressure. Studies have demonstrated that the effect of nicorandil on blood pressure is related to both its K+ channel opening and NO donating mechanisms. Since both hypertension and hypotension need correction before stroke intervention, it's crucial to consider the role of nicorandil and its impact on blood pressure. Previously published studies indicate that the right dosage of nicorandil can improve cerebral blood flow without significant changes in hemodynamic profiles. In this review, we discuss how nicorandil may contribute to better stroke outcomes based on previously published literature and laboratory findings.

Coronary spasm and vasomotor dysfunction as a cause of MINOCA

Increasing evidence has shown that coronary spasm and vasomotor dysfunction may be the underlying cause in more than half of myocardial infarctions with non-obstructive coronary arteries (MINOCA) as well as an important cause of chronic chest pain in the outpatient setting. We review the contemporary understanding of coronary spasm and related vasomotor dysfunction of the coronary arteries, the pathophysiology and prognosis, and current and emerging approaches to diagnosis and evidence-based treatment.

Management of Coronary Artery Spasm

Calcium channel blockers (CCBs) are the first-line treatment for coronary artery spasm (CAS). When CAS-related angina symptoms are not well controlled by CCB therapy, long-acting nitrates or (where available) nicorandil can be added as second-line medications. In the case of CAS refractory to standard treatments, several other alternative drugs and interventions have been proposed, including the Rho-kinase inhibitor fasudil, anti-adrenergic drugs, neural therapies and percutaneous coronary interventions. In patients with syncope or cardiac arrest caused by CAS-related tachyarrhythmias, or even bradyarrhythmias, implantation of an ICD or pacemaker, respectively, should be considered according to the risk of recurrence and efficacy of vasodilator therapy.

Dibazol-induced relaxation of ophthalmic artery in C57BL/6J mice is correlated with the potency to inhibit voltage-gated Ca2+ channels

We aimed to explore the effect of dibazol on the ophthalmic artery (OA) and ophthalmic artery smooth muscle cells (OASMCs) of C57BL/6J mice as well as the underlying mechanisms. The OA of C57BL/6J mice was isolated under a dissecting microscope for primary OASMCs culture and myogenic tests. OASMCs were identified through morphological and immunofluorescence analyses. Morphology changes in the OASMCs were examined by staining using rhodamine-phalloidin. We performed a collagen gel contraction assay to measure the contractile and relaxant activities of the OASMCs. The molecular probe Fluo-4 AM was used to examine intracellular free Ca²⁺ levels ([Ca²⁺]_in). The myogenic effects of OA were examined using wire myography. Additionally, the whole-cell patch-clamp technique was used to investigate the mechanisms underlying the relaxant effect of dibazol on L-type voltage-gated Ca²⁺ channels (LVGC) in isolated cells. 10^-5 M dibazol significantly inhibited the contraction of OASMCs and increased the [Ca²⁺]_in response to 30 mM KCl in a concentration-dependent manner. Dizabol had a more significant relaxant effect than 10^-5 M isosorbide dinitrate (ISDN). Similarly, dibazol showed a significant dose-dependent relaxant effect on OA contraction induced by 60 mM KCl or 0.3 μM 9,11-Dideoxy-9α,11α-methanoepoxy prostaglandin F_2α (U46619). The current-voltage (I-V) curve revealed that dibazol decreased Ca²⁺ currents in a concentration-dependent manner. In conclusion, dibazol exerted relaxant effects on the OA and OASMCs, which may involve the inhibition of the Ca²⁺ influx through LVGC in the cells.

In Vitro Drug Repurposing: Focus on Vasodilators

Drug repurposing aims to identify new therapeutic uses for drugs that have already been approved for other conditions. This approach can save time and resources compared to traditional drug development, as the safety and efficacy of the repurposed drug have already been established. In the context of cancer, drug repurposing can lead to the discovery of new treatments that can target specific cancer cell lines and improve patient outcomes. Vasodilators are a class of drugs that have been shown to have the potential to influence various types of cancer. These medications work by relaxing the smooth muscle of blood vessels, increasing blood flow to tumors, and improving the delivery of chemotherapy drugs. Additionally, vasodilators have been found to have antiproliferative and proapoptotic effects on cancer cells, making them a promising target for drug repurposing. Research on vasodilators for cancer treatment has already shown promising results in preclinical and clinical studies. However, additionally research is needed to fully understand the mechanisms of action of vasodilators in cancer and determine the optimal dosing and combination therapy for patients. In this review, we aim to explore the molecular mechanisms of action of vasodilators in cancer cell lines and the current state of research on their repurposing as a treatment option. With the goal of minimizing the effort and resources required for traditional drug development, we hope to shed light on the potential of vasodilators as a viable therapeutic strategy for cancer patients.

Angina in 2022: Current Perspectives

Angina is the main symptom of ischemic heart disease; mirroring a mismatch between oxygen supply and demand. Epicardial coronary stenoses are only responsible for nearly half of the patients presenting with angina; whereas in several cases; symptoms may underlie coronary vasomotor disorders; such as microvascular dysfunction or epicardial spasm. Various medications have been proven to improve the prognosis and quality of life; representing the treatment of choice in stable angina and leaving revascularization only in particular coronary anatomies or poorly controlled symptoms despite optimal medical therapy. Antianginal medications aim to reduce the oxygen supply-demand mismatch and are generally effective in improving symptoms; quality of life; effort tolerance and time to ischemia onset and may improve prognosis in selected populations. Since antianginal medications have different mechanisms of action and side effects; their use should be tailored according to patient history and potential drug-drug interactions. Angina with non-obstructed coronary arteries patients should be phenotyped with invasive assessment and treated accordingly. Patients with refractory angina represent a higher-risk population in which some therapeutic options are available to reduce symptoms and improve quality of life; but robust data from large randomized controlled trials are still lacking.

Endocrine disruption: Reproductive toxicity of glyceryl trinitrate and isosorbide mononitrate in male Wistar rats

Glyceryl trinitrate (GTN) and isosorbide mononitrate (IM) are organic nitrates which release nitric oxide upon metabolism with potential to adversely affect male reproductive function. Therefore, this study was designed to evaluate the sub-chronic effect of these organic nitrates on reproductive system in male rats. Wistar rats were separately treated with GTN and IM at 2.5, 5 and 7.5 mg/kg/day by oral gavage for 45 days. At the end of treatment, serum blood samples were taken from anaesthetized rats for assessment of hormonal profile. Epididymis was removed to analyse sperm parameters. Rat testes were dissected to perform histopathological evaluation and oxidative stress biomarkers. The GTN and IM treated groups showed a significant decrease in sperm parameters (count, motility and viability) and serum testosterone in comparison to normal control group. The GTN and IM treatment also altered sperm morphology such as bent tail and head deformities as compared to control. A significant decrease in catalase activity and, increase in nitric oxide and malondialdehyde were observed in high dose drug treated groups. Moreover, a significant increase in follicle stimulating hormone and decrease in testosterone levels were evident in all drug treated groups. The level of luteinizing hormone was raised in rats treated with medium doses of drugs while it decreased at the highest dose of both drugs. Histological study showed vacuolization and degeneration of seminiferous tubules. It is concluded that GTN and IM treatment adversely affected the male reproductive function by altering sperm parameters and disrupting the reproductive hormone profile which may be attributed to the increased level of nitric oxide and oxidative stress.

The Diverse Biological Activity of Recently Synthesized Nitro Compounds

The search for new and efficient pharmaceuticals is a constant struggle for medicinal chemists. New substances are needed in order to treat different pathologies affecting the health of humans and animals, and these new compounds should be safe, effective and have the fewest side effects possible. Some functional groups are known for having biological activity; in this matter, the nitro group (NO2) is an efficient scaffold when synthesizing new bioactive molecules. Nitro compounds display a wide spectrum of activities that include antineoplastic, antibiotic, antihypertensive, antiparasitic, tranquilizers and even herbicides, among many others. Most nitro molecules exhibit antimicrobial activity, and several of the compounds mentioned in this review may be further studied as lead compounds for the treatment of H. pylori, P. aeruginosa, M. tuberculosis and S. mutans infections, among others. The NO2 moiety triggers redox reactions within cells causing toxicity and the posterior death of microorganisms, not only bacteria but also multicellular organisms such as parasites. The same effect may be present in humans as well, so the nitro groups can be considered both a pharmacophore and a toxicophore at the same time. The role of the nitro group itself also has a deep effect on the polarity and electronic properties of the resulting molecules, and hence favors interactions with some amino acids in proteins. For these reasons, it is fundamental to analyze the recently synthesized nitro molecules that show any potential activity in order to develop new pharmacological treatments that enhance human health.

Nicorandil Improves Left Ventricular Myocardial Strain in Patients With Coronary Chronic Total Occlusion

Background

Nicorandil is recommended as a second-line treatment for stable angina; however, randomized-controlled trials to evaluate the benefit of nicorandil for patients with chronic total occlusion (CTO) are lacking.

Objective

To determine whether nicorandil can improve left ventricular (LV) myocardial strain in patients with CTO.

Methods

Patients with CTO were included and randomized to the nicorandil group (n = 31) and the control group (n = 30). Nicorandil was given orally at 15 mg/day for 3 months in the nicorandil group. Three-dimensional speckle-tracking echocardiography and the Seattle Angina Questionnaire (SAQ) survey were performed at baseline and at 3 months. The primary study endpoint was the LV global area strain (GAS) at 3 months.

Results

The nicorandil and the control groups were well-matched at baseline, including the mean GAS and SAQ scores. At 3 months, GAS in the nicorandil group was significantly higher than that in the control group (−23.7 ± 6.3% vs. −20.3 ± 5.6%, respectively; p = 0.033). There were no significant differences in LV global longitudinal strain, global circumferential strain, global radial strain, LV ejection fraction, LV end-diastolic volume, and LV end-systolic volume at 3 months between the two groups. At 3 months, the SAQ scores for angina stability, angina frequency, and treatment satisfaction in the nicorandil group were significantly higher than those in the control group.

Conclusion

Nicorandil treatment can improve GAS and angina symptoms in patients with CTO.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier: NCT05087797.

Clinical Implications of Nicorandil Combined with Trimetazidine in Patients with Coronary Heart Disease: A Real-World Observational Study

INTRODUCTION

Coronary heart disease (CHD) remains the leading cause of mortality in China. The treatment strategies, especially for patients with ischemic angina pectoris, are still far from satisfactory. Hence, this study was carried out to evaluate the long-term potential of nicorandil in Chinese patients with CHD.

METHODS

Adult patients with CHD were reviewed retrospectively from three hospitals in Central China to obtain relevant data. The primary outcome was the rate of major adverse cardiovascular events (MACE) which is the composite outcome of stroke, myocardial infarction (MI), and mortality at 3 years while the secondary outcomes included rates of MACE, stroke, MI, and mortality at 1 and 2 years. The rates of MACE were estimated using Kaplan-Meir survival curves and compared by log-rank test. The association between various treatment regimens and hazards of MACE was estimated using Cox proportional hazards model. All analyses were carried out using SAS 9.4.

RESULTS

A total of 5504, 1674, and 3923 patients treated with the nicorandil-trimetazidine combination, nicorandil, and trimetazidine were included in the study, respectively. At 3-year follow-up, the rate of MACE [hazard ratio (HR) 0.85; 95% CI 0.74-0.97; P = 0.017] and stroke (HR 0.58, 95% CI 0.48-0.71; P < 0.0001) was lower in the combination group compared to trimetazidine group. Similarly, the rate of stroke was significantly lower (HR 0.69; 95% CI 0.52-0.93; P = 0.0146) at 3 years in the nicorandil group compared to the trimetazidine group. The rate of stroke (HR 0.65; 95% CI 0.52-0.83; P = 0.0004) was significantly lower among the combination group compared with the trimetazidine group at 1-year follow-up. Similarly, the rate of stroke was significantly lower at 1 year (HR 0.70; 95% CI 0.50-0.97; P = 0.03) but not at 2 years (HR 0.70; 95% CI 0.52-0.94; P = 0.0177), while the rate of other outcomes, though lower in the nicorandil group than the trimetazidine group, was not statistically significant at 1 and 2 years respectively.

CONCLUSION

Nicorandil in combination with trimetazidine can be considered as an effective and potential treatment strategy in reducing the rate of MACE in patients with CHD in the Chinese population.

Effectiveness and Tolerability of Trimetazidine 80 Mg Once Daily in Patients with Stable Angina Uncontrolled with Bisoprolol-Based Therapy: The Modus Vivendi Observational Study

Introduction

Modus Vivendi was conducted in routine clinical practice to evaluate the effect of adding trimetazidine 80 mg once daily (TMZ 80 OD) to treat patients with persistent symptoms despite treatment with background antianginal therapies including maximally tolerated bisoprolol.

Methods

This multicenter, prospective, observational, open-label, uncontrolled study recruited adult outpatients with a confirmed diagnosis of stable angina to whom physicians had decided to prescribe TMZ 80 OD. All patients were symptomatic despite treatment, including maximally tolerated doses of bisoprolol. Data on number of angina attacks, use of short-acting nitrates, and quality of life (QoL) were collected at baseline (V1) and at 1-month (V2) and 3-month (V2) follow-up visits. Two sub-analyses assessed efficacy in patients who remained on a stable bisoprolol dose throughout the study, and in patients in whom background antianginal therapy was known.

Results

A total of 1939 patients were recruited (57.2% women). The mean age was 65.6 ± 8.8 years; 73.8% had class II and 26.2% class III angina. At V1, the mean number of angina attacks per week was 6.2 ± 6.5 despite antianginal therapy including maximally tolerated bisoprolol dosage. Following the addition of TMZ 80 OD, this decreased to 3.4 ± 4.2 attacks per week at V2, and 1.6 ± 2.6 at V3 (P < 0.05 at V2 and V3), with concomitant reductions in short-acting nitrate use (P < 0.05). Significant improvements in QoL were observed throughout the study. Subgroup analyses showed that the addition of TMZ 80 OD to guideline-recommended antianginal therapy was associated with significant reductions in the mean number of weekly angina attacks and consumption of short-acting nitrates and improvements in QoL whether patients were treated with maximally tolerated bisoprolol and TMZ 80 OD alone, or maximally tolerated bisoprolol and TMZ 80 OD on top of other antianginal therapies. Treatment was well tolerated.

Conclusion

The study findings support the addition of TMZ 80 OD to bisoprolol with or without other antianginal therapies for patients with persistent angina.

Trial Registration

This study was retrospectively registered under the number ISRCTN29992579.

A pathophysiological compass to personalize antianginal drug treatment

Myocardial ischaemia results from coronary macrovascular or microvascular dysfunction compromising the supply of oxygen and nutrients to the myocardium. The underlying pathophysiological processes are manifold and encompass atherosclerosis of epicardial coronary arteries, vasospasm of large or small vessels and microvascular dysfunction - the clinical relevance of which is increasingly being appreciated. Myocardial ischaemia can have a broad spectrum of clinical manifestations, together denoted as chronic coronary syndromes. The most common antianginal medications relieve symptoms by eliciting coronary vasodilatation and modulating the determinants of myocardial oxygen consumption, that is, heart rate, myocardial wall stress and ventricular contractility. In addition, cardiac substrate metabolism can be altered to alleviate ischaemia by modulating the efficiency of myocardial oxygen use. Although a universal agreement exists on the prognostic importance of lifestyle interventions and event prevention with aspirin and statin therapy, the optimal antianginal treatment for patients with chronic coronary syndromes is less well defined. The 2019 guidelines of the ESC recommend a personalized approach, in which antianginal medications are tailored towards an individual patient's comorbidities and haemodynamic profile. Although no antianginal medication improves survival, their efficacy for reducing symptoms profoundly depends on the underlying mechanism of the angina. In this Review, we provide clinicians with a rationale for when to use which compound or combination of drugs on the basis of the pathophysiology of the angina and the mode of action of antianginal medications.

Aging-Induced Impairment of Vascular Function: Mitochondrial Redox Contributions and Physiological/Clinical Implications

Significance: The vasculature responds to the respiratory needs of tissue by modulating luminal diameter through smooth muscle constriction or relaxation. Coronary perfusion, diastolic function, and coronary flow reserve are drastically reduced with aging. This loss of blood flow contributes to and exacerbates pathological processes such as angina pectoris, atherosclerosis, and coronary artery and microvascular disease. Recent Advances: Increased attention has recently been given to defining mechanisms behind aging-mediated loss of vascular function and development of therapeutic strategies to restore youthful vascular responsiveness. The ultimate goal aims at providing new avenues for symptom management, reversal of tissue damage, and preventing or delaying of aging-induced vascular damage and dysfunction in the first place. Critical Issues: Our major objective is to describe how aging-associated mitochondrial dysfunction contributes to endothelial and smooth muscle dysfunction via dysregulated reactive oxygen species production, the clinical impact of this phenomenon, and to discuss emerging therapeutic strategies. Pathological changes in regulation of mitochondrial oxidative and nitrosative balance (Section 1) and mitochondrial dynamics of fission/fusion (Section 2) have widespread effects on the mechanisms underlying the ability of the vasculature to relax, leading to hyperconstriction with aging. We will focus on flow-mediated dilation, endothelial hyperpolarizing factors (Sections 3 and 4), and adrenergic receptors (Section 5), as outlined in Figure 1. The clinical implications of these changes on major adverse cardiac events and mortality are described (Section 6). Future Directions: We discuss antioxidative therapeutic strategies currently in development to restore mitochondrial redox homeostasis and subsequently vascular function and evaluate their potential clinical impact (Section 7). Antioxid. Redox Signal. 35, 974-1015.

Nicorandil Decreases Renal Injury in Patients With Coronary Heart Disease Complicated With Type I Cardiorenal Syndrome

ABSTRACT

Cardiorenal syndrome (CRS) is a group of disorders in which heart or kidney dysfunction worsens each other. This study aimed to explore the improvement effect of nicorandil on cardiorenal injury in patients with type I CRS. Patients with coronary heart disease complicated with type I CRS were enrolled. Based on the conventional treatment, the patients were prospectively randomized into a conventional treatment group and a nicorandil group, which was treated with 24 mg/d nicorandil intravenously for 1 week. Fasting peripheral venous blood serum and urine were collected before and at the end of treatment. An automatic biochemical analyzer and enzyme linked immunosorbent assay were used to detect B-type brain natriuretic peptide (BNP), serum creatinine (Scr) and cystatin C (Cys-C), renal injury index-kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and interleukin-18 (IL-18) levels. The left ventricular ejection fraction was measured by echocardiography. All measurements were not significantly different between the nicorandil and conventional treatment groups before treatment (all P > 0.05), and BNP, Scr, Cys-C, NGAL, KIM-1, and IL-18 were decreased in the 2 groups at the end of treatment (all P < 0.05). Compared with the conventional treatment group, BNP, Scr, Cys-C, NGAL, KIM-1, and IL-18 were more significantly decreased in the nicorandil group (all P < 0.05) and left ventricular ejection fraction was more significantly increased (P < 0.05). Therefore, nicorandil could significantly improve the cardiac and renal function of patients with type I CRS. This may prove to be a new therapeutic tool for improving the prognosis and rehabilitation of type I CRS.

Cardiovascular Drugs and Osteoarthritis: Effects of Targeting Ion Channels

Osteoarthritis (OA) and cardiovascular diseases (CVD) share many similar features, including similar risk factors and molecular mechanisms. A great number of cardiovascular drugs act via different ion channels and change ion balance, thus modulating cell metabolism, osmotic responses, turnover of cartilage extracellular matrix and inflammation. These drugs are consumed by patients with CVD for many years; however, information about their effects on the joint tissues has not been fully clarified. Nevertheless, it is becoming increasingly likely that different cardiovascular drugs may have an impact on articular tissues in OA. Here, we discuss the potential effects of direct and indirect ion channel modulating drugs, including inhibitors of voltage gated calcium and sodium channels, hyperpolarization-activated cyclic nucleotide-gated channels, β-adrenoreceptor inhibitors and angiotensin-aldosterone system affecting drugs. The aim of this review was to summarize the information about activities of cardiovascular drugs on cartilage and subchondral bone and to discuss their possible consequences on the progression of OA, focusing on the modulation of ion channels in chondrocytes and other joint cells, pain control and regulation of inflammation. The implication of cardiovascular drug consumption in aetiopathogenesis of OA should be considered when prescribing ion channel modulators, particularly in long-term therapy protocols.

Metoprolol combined with nicorandil on unstable angina pectoris can reduce incidence of cardiovascular events and inflammatory reactions

OBJECTIVE

This research was designed to investigate the efficacy of metoprolol combined with nicorandil on unstable angina pectoris (UAP).

METHODS

Totally 174 UAP patients treated in the Laixi City People's Hospital from May 2017 to December 2019 were taken as the research objects. They were divided into the control (n=79, CG) and joint (n=95) groups (JG). Patients in the CG were treated with metoprolol, while those in the JG were treated with nicorandil. The clinical efficacy, adverse events and inflammatory reactions were observed.

RESULTS

The effective rate of the JG was better than that of the CG after treatment. There were no additional adverse reactions, and the incidence of cardiovascular events reduced. The changes of cardiac function manifested that the left ventricular end systolic diameter (LVESD) and left ventricular end diastolic diameter (LVEDD) in the JG were lower than those in the CG, while the left ventricular ejection fraction (LVEF) was higher. In addition, the serum levels of total cholesterol (TC), triglyceride (TG), high-sensitivity C-reactive protein (hs-CRP) and interleukin-6 (IL-6) in the JG were lower than those in the CG.

CONCLUSION

Metoprolol combined with nicorandil is effective for UAP patients, which reduces the incidence of cardiovascular adverse events and inhibits inflammatory reactions.

Protective Effect of Nicorandil on Cardiac Microvascular Injury: Role of Mitochondrial Integrity

A major shortcoming of postischemic therapy for myocardial infarction is the no-reflow phenomenon due to impaired cardiac microvascular function including microcirculatory barrier function, loss of endothelial activity, local inflammatory cell accumulation, and increased oxidative stress. Consequently, inadequate reperfusion of the microcirculation causes secondary ischemia, aggravating the myocardial reperfusion injury. ATP-sensitive potassium ion (KATP) channels regulate the coronary blood flow and protect cardiomyocytes from ischemia-reperfusion injury. Studies in animal models of myocardial ischemia-reperfusion have illustrated that the opening of mitochondrial KATP (mito-KATP) channels alleviates endothelial dysfunction and reduces myocardial necrosis. By contrast, blocking mito-KATP channels aggravates microvascular necrosis and no-reflow phenomenon following ischemia-reperfusion injury. Nicorandil, as an antianginal drug, has been used for ischemic preconditioning (IPC) due to its mito-KATP channel-opening effect, thereby limiting infarct size and subsequent severe ischemic insult. In this review, we analyze the protective actions of nicorandil against microcirculation reperfusion injury with a focus on improving mitochondrial integrity. In addition, we discuss the function of mitochondria in the pathogenesis of myocardial ischemia.

Enabling patient-reported outcome measures in clinical trials, exemplified by cardiovascular trials

OBJECTIVES

There has been limited success in achieving integration of patient-reported outcomes (PROs) in clinical trials. We describe how stakeholders envision a solution to this challenge.

METHODS

Stakeholders from academia, industry, non-profits, insurers, clinicians, and the Food and Drug Administration convened at a Think Tank meeting funded by the Duke Clinical Research Institute to discuss the challenges of incorporating PROs into clinical trials and how to address those challenges. Using examples from cardiovascular trials, this article describes a potential path forward with a focus on applications in the United States.

RESULTS

Think Tank members identified one key challenge: a common understanding of the level of evidence that is necessary to support patient-reported outcome measures (PROMs) in trials. Think Tank participants discussed the possibility of creating general evidentiary standards depending upon contextual factors, but such guidelines could not be feasibly developed because many contextual factors are at play. The attendees posited that a more informative approach to PROM evidentiary standards would be to develop validity arguments akin to courtroom briefs, which would emphasize a compelling rationale (interpretation/use argument) to support a PROM within a specific context. Participants envisioned a future in which validity arguments would be publicly available via a repository, which would be indexed by contextual factors, clinical populations, and types of claims.

CONCLUSIONS

A publicly available repository would help stakeholders better understand what a community believes constitutes compelling support for a specific PROM in a trial. Our proposed strategy is expected to facilitate the incorporation of PROMs into cardiovascular clinical trials and trials in general.

Relief of Ischemia in Ischemic Cardiomyopathy

PURPOSE OF THE REVIEW

Ischemic heart disease is among the most common causes of morbidity and mortality worldwide. In its stable manifestation, obstructing coronary artery stenoses prevent myocardial blood flow from matching metabolic needs of the heart under exercise conditions, which manifests clinically as dyspnea or chest pain. Prolonged bouts of ischemia may result in permanent myocardial dysfunction, heart failure, and eventually reduced survival. The aim of the present work is to review currently available approaches to provide relief of ischemia in stable coronary artery disease (CAD).

RECENT FINDINGS

Several pharmacological and interventional approaches have proven effectiveness in reducing the burden of ischemia in stable CAD and allow for symptom control and quality of life improvement. However, substantial evidence in favor of improved survival with ischemia relief is lacking, and recently published randomized controlled trial suggests that only selected groups of patients may substantially benefit from this approach. Pharmacological treatments aimed at reducing ischemia were shown to significantly reduce ischemic symptoms but failed to provide prognostic benefit. Myocardial revascularization is able to re-establish adequate coronary artery flow and was shown to improve survival in selected groups of patients, i.e., those with significant left main CAD or severe left ventricular dysfunction in multivessel CAD. Outside the previously mentioned categories, revascularization appears to improve symptoms control over medical therapy, but does not confer prognostic advantage. More studies are needed to elucidate the role of systematic invasive functional testing to identify individuals more likely to benefit from revascularization and to evaluate the prognostic role of chronic total occlusion recanalization.

Effect of intravenous application of nicorandil on area of myocardial infarction in patients with STEMI during the perioperative stage of PCI

OBJECTIVE

The aim of the present study was to evaluate the effectiveness and safety of nicorandil in improving the area of myocardial infarction in patients with acute myocardial infarction (AMI).

METHODS

One hundred and twenty patients with acute ST-segment elevation myocardial infarction (STEMI) admitted to our hospital between December 1, 2018 and December 31, 2019 were selected and randomly allocated to the experimental group (group A, n = 60) and the control group (group B, n = 60). In the experimental group, an infusion of nicorandil was given intravenously before the first balloon dilation or 1 minute before the stent placement, and with the completion of the infusion, nicorandil maintenance infusion was given. In the control group, only balloon dilation and stent placement were undertaken.

RESULTS

The postoperative peak levels of myoglobin, creatine kinase isoform and hypersensitive troponin T were significantly lower in group A than in group B (p < 0.05). Moreover, the left ventricular ejection fraction (LVEF) on the 180th day post operation was substantially greater in group A than in group B (p < 0.01), and the area of myocardial infarction was significantly smaller in patients in group A than those in group B on the 180th day post operation (p < 0.01). In terms of the safety, there were no statistically significant differences in the incidence of slow flow/no reflow, malignant arrhythmias, and hypotension within 24 hours post operation between the two groups (p > 0.05), and no major adverse cardiovascular event (MACE) occurred in either group during the postoperative follow-up period of 180 days (p > 0.05).

CONCLUSION

Intravenous administration of nicorandil in patients with STEMI during the perioperative percutaneous coronary intervention (PCI) period was effective in reducing the area of myocardial infarction and myocardial injury without increasing the incidence of malignant arrhythmias, hypotension, or composite cardiovascular events during the drug administration period.

Pathobiology and evolving therapies of coronary artery vasospasm

Coronary artery vasospasm is a known cause of chest pain and requires a high level of clinical suspicion for diagnosis. It also remains in the differential diagnosis for patients presenting with type 2 myocardial infarction. There are few randomized controlled trials for guideline-based prevention and treatment for coronary artery vasospasm. In this article, we review updated concepts in coronary artery vasospasm. Specifically, our aim is to provide current evidence of pathophysiology, identify the risk factors, propose a diagnostic algorithm, review available evidence of evolving therapies, and identify patients who would benefit from automatic implantable cardioverter defibrillators.

Цукровий діабет і хронічний коронарний синдром

Хронічний коронарний синдром (ХКС) характеризується розвитком епізодів ішемії внаслідок дисбалансу між потребами та кровопостачанням міокарда. Зазвичай такі епізоди провокуються фізичними або емоційними навантаженнями чи іншими стресовими ситуаціями, проте можуть виникати й спонтанно. Класичним проявом ішемії міокарда є напади стенокардії. У деяких випадках захворювання певний час може бути безсимптомним і дебютувати одразу гострим коронарним синдромом. ХКС може мати довготривалий доклінічний період на тлі підтвердженого коронарного атеросклерозу. В огляді проведений аналіз літературних джерел, присвячених сучасному стану проблеми цукрового діабету (ЦД) і ХКС. Зокрема, аналізуються питання, пов’язані з особливостями оцінки ризику, основних чинників, що зумовлюють дуже високий ризик атеросклеротичних серцево-судинних захворювань, класифікацією, основними характеристиками ХКС та його особливостями при ЦД, діагностикою ХКС (дозоване фізичне навантаження (велоергометрія, тредміл-тест) або стрес-тести, однофотонна емісійна комп’ютерна томографія, стрес-ехокардіографія; стрес-магнітно-резонансна томографія, позитронно-емісійна томографія із застосуванням радіоактивних маркерів). Аналізуються питання консервативної терапії ХКС на тлі ЦД (призначення антиагрегантів, блокаторів β-адренорецепторів, блокаторів кальцієвих каналів, нітратів, інгібіторів ангіотензинперетворювального ферменту, міокардіальних цитопротекторів, статинів). Лікування пацієнта з поєднанням ЦД і ХКС буде успішним лише в тому випадку, якщо призначено адекватну, безпечну в плані гіпоглікемій і можливих серцево-судинних ризиків цукрознижувальну терапію, з одного боку, і метаболічно нейтральну антиангінальну терапію— з іншого. Без сумніву, необхідно звернути увагу на корекцію факторів ризику ССЗ, АГ і ХСН.

The Role of Nicorandil in the Management of Chronic Coronary Syndromes in the Gulf Region

Chronic coronary syndromes (CCS) and stable angina are a growing clinical burden worldwide. This is of particular concern in the Gulf region given its high prevalence of cardiovascular risk factors, especially diabetes mellitus and smoking. Despite recommendations on the use of first- and second-line anti-anginal medication, management challenges remain. Current guidelines for pharmacologic treatment are not determined by the range of pathophysiological mechanisms of ischaemia and consequent angina, which may occur either in isolation or co-exist. In this article, we highlight the need to improve knowledge of the epidemiology of chronic coronary syndromes in the Middle East and Gulf region, and the need for studies of stratified pharmacologic approaches to improve symptomatic angina and quality of life in the large and growing number of patients with coronary artery disease from this region. We discuss the role of nicorandil, currently recommended as a second-line anti-anginal drug in CCS patients, and suggest that this may be a particularly useful add-on therapy for patients in the Gulf region.

Pre- and Post-Conditioning of the Heart: An Overview of Cardioprotective Signaling Pathways

Since the discovery of ischemic pre- and post-conditioning, more than 30 years ago, the knowledge about the mechanisms and signaling pathways involved in these processes has significantly increased. In clinical practice, on the other hand, such advancement has yet to be seen. This article provides an overview of ischemic pre-, post-, remote, and pharmacological conditioning related to the heart. In addition, we reviewed the cardioprotective signaling pathways and therapeutic agents involved in the above-mentioned processes, aiming to provide a comprehensive evaluation of the advancements in the field. The advancements made over the last decades cannot be ignored and with the exponential growth in techniques and applications. The future of pre- and post-conditioning is promising.

Efficacy and Safety of Nicorandil in Preventing Contrast-Induced Nephropathy after Elective Percutaneous Coronary Intervention: A Pooled Analysis of 1229 Patients

Background

Nicorandil in reducing contrast-induced nephropathy (CIN) following elective percutaneous coronary intervention (PCI) is an inconsistent practice. This article aims to evaluate the efficacy and safety of nicorandil in preventing CIN after elective PCI.

Methods

This is a pooled analysis of patients treated with elective PCI. The primary outcome was the incidence of CIN. The secondary outcomes were major adverse events, including mortality, heart failure, recurrent myocardial infarction, stroke, and renal replacement therapy.

Results

A total of 1229 patients were recruited in our study. With statistical significance, nicorandil lowered the risk of CIN (odds ratio = 0.26; 95% confidence interval = 0.16–0.44; P < 0.00001; I² = 0%) in patients who underwent elective PCI. In addition, no significant differences were observed in the incidence of mortality, heart failure, recurrent myocardial infarction, stroke, and renal replacement therapy between the two groups (P > 0.05).

Conclusions

Our article indicated that nicorandil could prevent CIN without increasing the major adverse events. Furthermore, sufficiently powered and randomized clinical studies are still needed in order to determine the role of nicorandil in preventing CIN after elective PCI.

Nicorandil for Periprocedural Myocardial Injury in Elective Percutaneous Coronary Intervention: A Meta-Analysis of 10 Randomized Controlled Trials

The clinical outcomes of nicorandil in percutaneous coronary intervention (PCI) are conflicting. We sought to evaluate the effects of nicorandil on periprocedural myocardial injury (PMI) in elective PCI. Eligible studies that reported the effect of nicorandil on PMI in elective PCI were obtained from PubMed, Web of Science, and Cochrane Library (up to October 28, 2019). The outcomes were PMI and major adverse cardiovascular and cerebrovascular events (MACCEs). Ten randomized controlled trials with 1304 patients undergoing elective PCI were evaluated. Nicorandil significantly reduced the incidence of PMI (odds ratio [OR] = 0.48; P = .0003); however, there was no significant difference in MACCEs (OR = 0.80; P = .45) between the 2 groups. Subgroup analyses showed that nicorandil significantly lowered the PMI risk when only patients with stable coronary artery disease (OR = 0.41; P = .0008) were considered and when nicorandil was administered intravenously (OR = 0.41; P = .0007) or orally (OR = 0.33; P = .0001). This meta-analysis suggests that nicorandil could reduce the incidence of PMI without increasing the occurrence of MACCEs in elective PCI. The effect of nicorandil in lowering the PMI risk is associated with the diagnosis of the patients and the route of nicorandil administration.

Nicorandil alleviates apoptosis in diabetic cardiomyopathy through PI3K/Akt pathway

Nicorandil exerts myocardial protection through its antihypoxia and antioxidant effects. Here, we investigated whether it plays an anti‐apoptotic role in diabetic cardiomyopathy. Sprague‐Dawley rats were fed with high‐fat diet; then single intraperitoneal injection of streptozotocin was performed. Rats with fasting blood glucose (FBG) higher than 11.1 mmol/L were selected as models. Eight weeks after the models were built, rats were treated with nicorandil (7.5 mg/kg day and 15 mg/kg day respectively) for 4 weeks. H9c2 cardiomyocytes were treated with nicorandil and then stimulated with high glucose (33.3 mmol/L). TUNEL assay and level of bcl‐2, bax and caspase‐3 were measured. 5‐HD was used to inhibit nicorandil. Also, PI3K inhibitor (Miltefosine) and mTOR inhibitor (rapamycin) were used to inhibit PI3K/Akt pathway. The results revealed that nicorandil (both 7.5 mg/kg day and 15mg/kg day) treatment can increase the level of NO in the serum and eNOS in the heart of diabetic rats compared with the untreated diabetic group. Nicorandil can also improve relieve cardiac dysfunction and reduce the level of apoptosis. In vitro experiments, nicorandil (100 µmol) can attenuate the level of apoptosis stimulated by high glucose significantly in H9C2 cardiomyocyte compared with the untreated group. The effect of nicorandil on apoptosis was blocked by 5‐HD, and it was accompanied with inhibition of the phosphorylation of PI3K, Akt, eNOS, and mTOR. After inhibition of PI3K/Akt pathway, the protective effect of nicorandil is restrained. These results verified that as a NO donor, nicorandil can also inhibit apoptosis in diabetic cardiomyopathy which is mediated by PI3K/Akt pathway.

Advances in small-molecule therapy for managing angina pectoris in the elderly

Introduction: As our population ages, the prevalence of angina is growing, leading to increased morbidity and decreased quality of life. The management of angina in the elderly is challenging due to drug intolerance and/or drug resistance as well as frailty. Over the past decades, many new therapeutic small molecules have been investigated for the management of angina. Although none of these studies have specifically focused on the therapies for the elderly, they offer promising new avenues for the treatment of angina in the elderly. Areas covered: Herein, the authors provide a review of the recently published literature on the use of small-molecule therapies for angina management in the elderly and provide a brief overview of these therapies. Expert opinion: A variety of therapeutic classes of existing and newer small molecules are emerging for the management of angina in the elderly. An individualized approach to the management of angina in this growing population is critical for good outcomes. Many small molecules are in their initial stages of clinical use, and further research should be conducted on their utility, especially in the elderly.

Nicorandil prior to primary percutaneous coronary intervention improves clinical outcomes in patients with acute myocardial infarction: a meta-analysis of randomized controlled trials

Background: Nicorandil prior to reperfusion by primary percutaneous coronary intervention (PCI) in patients with ST-segment elevated myocardial infarction (STEMI) has been suggested to be beneficial. However, results of previous randomized controlled trials (RCTs) were not consistent. We aimed to perform a meta-analysis to systematically evaluate the effect of periprocedural nicorandil in these patients. Methods: Related studies were obtained by searching PubMed, Embase and Cochrane's Library. Effects of perioperative nicorandil on the incidence of no-reflow phenomenon (NRP), corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC), wall motion score (WMS), left ventricular ejection fraction (LVEF), heart failure (HF) exacerbation of rehospitalization and incidence of major cardiovascular adverse events (MACE) were analyzed. Results: Eighteen RCTs with 2,055 patients were included. Treatment of nicorandil prior to PCI significantly reduced the incidence of NRP (risk ratio [RR]: 0.47, P<0.001), and reduced CTFC (weighed mean difference [WMD]: -4.54, P<0.001) immediately after PCI. Moreover, although nicorandil did not significantly affect WMS (WMD: 0.04, P=0.91), treatment of nicorandil significantly increased LVEF in STEMI patients undergoing primary PCI (WMD: 1.89%, P<0.001). In addition, nicorandil significantly reduced the risk of HF exacerbation or rehospitalization (RR: 0.44, P=0.001) and the incidence of MACE (RR: 0.68, P<0.001). Further analyses showed that effects of nicorandil on LVEF, HF exacerbation and MACE were consistent within one month after PCI and during follow-up. Conclusions: Periprocedural nicorandil improves coronary blood flow, cardiac systolic function and prognosis in STEMI patients receiving primary PCI.

Potassium channels in vascular smooth muscle: a pathophysiological and pharmacological perspective

Potassium (K⁺ ) ion channel activity is an important determinant of vascular tone by regulating cell membrane potential (MP). Activation of K⁺ channels leads to membrane hyperpolarization and subsequently vasodilatation, while inhibition of the channels causes membrane depolarization and then vasoconstriction. So far five distinct types of K⁺ channels have been identified in vascular smooth muscle cells (VSMCs): Ca⁺² -activated K⁺ channels (BK_{C a} ), voltage-dependent K⁺ channels (K_V ), ATP-sensitive K⁺ channels (K_ATP ), inward rectifier K⁺ channels (K_ir ), and tandem two-pore K⁺ channels (K₂ P). The activity and expression of vascular K⁺ channels are changed during major vascular diseases such as hypertension, pulmonary hypertension, hypercholesterolemia, atherosclerosis, and diabetes mellitus. The defective function of K⁺ channels is commonly associated with impaired vascular responses and is likely to become as a result of changes in K⁺ channels during vascular diseases. Increased K⁺ channel function and expression may also help to compensate for increased abnormal vascular tone. There are many pharmacological and genotypic studies which were carried out on the subtypes of K⁺ channels expressed in variable amounts in different vascular beds. Modulation of K⁺ channel activity by molecular approaches and selective drug development may be a novel treatment modality for vascular dysfunction in the future. This review presents the basic properties, physiological functions, pathophysiological, and pharmacological roles of the five major classes of K⁺ channels that have been determined in VSMCs.