Organophosphates and Torsade de Pointes Ventricular Tachycardia

Magnesium sulfate in organophosphorus compound poisoning: A prospective open-label clinician-initiated intervention trial with historical controls

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Conclusion:

Cardiotoxicity of some pesticides and their amelioration

Pesticides are used to control pests that harm plants, animals, and humans. Their application results in the contamination of the food and water systems. Pesticides may cause harm to the human body via occupational exposure or the ingestion of contaminated food and water. Once a pesticide enters the human body, it may create health consequences such as cardiotoxicity. There is not enough information about pesticides that cause cardiotoxicity in the literature. Currently, there are few reports that summarized the cardiotoxicity due to some pesticide groups. This necessitates reviewing the current literature regarding pesticides and cardiotoxicity and to summarize them in a concrete review. The objectives of this review article were to summarize the advances in research related to pesticides and cardiotoxicity, to classify pesticides into certain groups according to cardiotoxicity, to discuss the possible mechanisms of cardiotoxicity, and to present the agents that ameliorate cardiotoxicity. Approximately 60 pesticides were involved in cardiotoxicity: 30, 13, and 17 were insecticides, herbicides, and fungicides, respectively. The interesting outcome of this study is that 30 and 13 pesticides from toxicity classes II and III, respectively, are involved in cardiotoxicity. The use of standard antidotes for pesticide poisoning shows health consequences among users. Alternative safe medical management is the use of cardiotoxicity-ameliorating agents. This review identifies 24 ameliorating agents that were successfully used to manage 60 cases. The most effective agents were vitamin C, curcumin, vitamin E, quercetin, selenium, chrysin, and garlic extract. Vitamin C showed ameliorating effects in a wide range of toxicities. The exposure mode to pesticide residues, where 1, 2, 3, and 4 are aerial exposure to pesticide drift, home and/or office exposure, exposure due to drinking contaminated water, and consumption of contaminated food, respectively. General cardiotoxicity is represented by 5, whereas 6, 7, 8 and 9 are electrocardiogram (ECG) of hypotension due to exposure to OP residues, ECG of myocardial infraction due to exposure to OPs, ECG of hypertension due to exposure to OC and/or PY, and normal ECG respectively.

Serum High-sensitivity C-reactive Protein Level and Corrected QT Interval in Agricultural Workers in Myanmar Exposed to Chronic Occupational Organophosphate Pesticides

Although acute organophosphate (OP) pesticide poisoning is associated with the risk cardiovascular diseases (CVD), the association between chronic occupational OP pesticide exposure and CVD risk is limited. We investigated serum high-sensitivity C-reactive protein (hs-CRP) levels and QTc intervals in 45 agricultural workers who were chronically exposed to OP pesticides and 45 non-exposed subjects. Serum hs-CRP level was determined by enzyme-linked immunosorbent assay (ELISA) and a level >1.0 mg/l was regarded as CVD risk. The QT interval was measured by routine 12-lead Electrocardiogram (ECG) with Lead II rhythm, and QTc was calculated. The median value of the serum hs-CRP level [1.20 (0.67-2.38) vs 0.74 (0.41-1.17) mg/l, P <0.05] and the mean QTc interval (422.71 ± 23.73 vs 396.27 ± 18.48 ms, P <0.0001) was significantly higher in the OP pesticide exposed subjects. Pesticide exposure was significantly associated with CVD risk (Chi-Square χ² = 6.480, P = 0.011) and QTc interval prolongation (χ² = 13.846, P <0.001). A higher risk of CVD (odds ratio = 3.030; 95% confidence interval = 1.276 - 7.197) was observed in the OP pesticide exposed subjects. This study suggested that OP pesticide exposure should be considered as one of the significant risk factors for CVDs.

Cardiac injury in organophosphate poisoning after acute ingestion

Introduction

Sparse data and conflicting evidence exist on the prevalence and prognosis of organophosphate (OP)-related cardiac toxicity. We aimed to characterize the cardiac abnormalities of OP after an acute cholinergic crisis in adults without previous cardiovascular conditions.

Patients and Methods

We did a prospective observational study in a tertiary-care hospital of north India (Postgraduate Institute of Medical Education and Research, Chandigarh) in 74 patients aged ≥ 13 years admitted with acute OP poisoning after self-ingestion. A systemic evaluation, including clinical characteristics, electrocardiography, and echocardiography, was performed to estimate the prevalence and prognosis of cardiac injury. A rate-corrected QT interval was calculated using Bazett's method, and >440 milliseconds was used to define prolongation.

Results

Chlorpyrifos was the most commonly ingested OP (n = 29). The patients had a similar occurrence of hypotension (n = 10) and hypertension (n = 9) at admission, and electrocardiography demonstrated sinus tachycardia in 38 (51.3%) and sinus bradycardia in one case. During the hospital stay, 3 out of 74 patients had a prolonged rate-corrected QT interval (457, 468, and 461 milliseconds), and one patient developed supraventricular tachycardia. Eight (10.8%) patients developed the intermediate syndrome, and six (8.1%) died. None of the hemodynamic or electrocardiographic abnormalities was associated with in-hospital mortality or intermediate syndrome development on univariant analysis. Baseline echocardiography at hospital discharge was performed in 27 patients (admitted during 2018) and normal in all except mild tricuspid regurgitation in one. At a 6-month follow-up, 23 cases were available for cardiovascular screening (including echocardiography) and had a normal evaluation.

Conclusion

Cardiac toxicity is uncommon after acute OP self-ingestion and lacks prognostic significance.

Structural and kinetic evidence of aging after organophosphate inhibition of human Cathepsin A

Human Cathepsin A (CatA) is a lysosomal serine carboxypeptidase of the renin-angiotensin system (RAS) and is structurally similar to acetylcholinesterase (AChE). CatA can remove the C-terminal amino acids of endothelin I, angiotensin I, Substance P, oxytocin, and bradykinin, and can deamidate neurokinin A. Proteomic studies identified CatA and its homologue, SCPEP1, as potential targets of organophosphates (OP). CatA could be stably inhibited by low µM to high nM concentrations of racemic sarin (GB), soman (GD), cyclosarin (GF), VX, and VR within minutes to hours at pH 7. Cyclosarin was the most potent with a kinetically measured dissociation constant (K_I) of 2 µM followed by VR (K_I = 2.8 µM). Bimolecular rate constants for inhibition by cyclosarin and VR were 1.3 × 10³ M^-1sec^-1 and 1.2 × 10³ M^-1sec^-1, respectively, and were approximately 3-orders of magnitude lower than those of human AChE indicating slower reactivity. Notably, both AChE and CatA bound diisopropylfluorophosphate (DFP) comparably and had K_I^DFP = 13 µM and 11 µM, respectively. At low pH, greater than 85% of the enzyme spontaneously reactivated after OP inhibition, conditions under which OP-adducts of cholinesterases irreversibly age. At pH 6.5 CatA remained stably inhibited by GB and GF and <10% of the enzyme spontaneously reactivated after 200 h. A crystal structure of DFP-inhibited CatA was determined and contained an aged adduct. Similar to AChE, CatA appears to have a "backdoor" for product release. CatA has not been shown previously to age. These results may have implications for: OP-associated inflammation; cardiovascular effects; and the dysregulation of RAS enzymes by OP.

Increased morbidity and mortality in acute human organophosphate-poisoned patients treated by oximes: a meta-analysis of clinical trials

Organophosphates are one of the most common causes of poisoning, especially in the Third world, with high morbidity and mortality. The treatment of this type of poisoning involves the use of atropine and oximes. Atropine has been used successfully in large doses to counteract the muscarinic effects of organophosphate poisoning, but the efficacy of oximes in the management of this poisoning remains under question. In this study, we undertook a meta-analysis by reviewing all clinical trials to evaluate the efficacy of oximes in the management of organophosphate poisoning. The databases of PUBMED, EMBASE, Cochrane, SCOPUS, and the search engine of Google were searched for all clinical trials on the use of oximes in organophosphate poisoning. The inclusion criteria were death, development of intermediate syndrome, and need for ventilation. Six clinical trials met the inclusion criteria and were included in the metaanalysis. The x2 tests for heterogeneity (P–0.25, 0.16, and 0.33, respectively) indicated that the included studies were not significantly heterogeneous and could be combined. A significant relative risk (P–0.0017) for death among oxime-exposed was 2.17 (95% CI of 1.34 / 3.51). The ‘need for ventilation’ in patients who received oxime was higher (P–0.03) than those who did not receive oxime with a relative risk of 1.53 (1.16 / 2.02). The incidence of ‘intermediate syndrome’ for oximeexposed patients was significantly higher (P–0.01) than oxime non-exposed patients with a relative risk of 1.57 (95% CI 1.11 / 2.11). It can be concluded that oximes are not effective in the management of organophosphate-poisoned patients and, surprisingly, they can be dangerous and worsen the patient's clinical situation.

Organophosphorus and carbamate insecticide poisoning

Both organophosphorus (OP) and carbamate insecticides inhibit acetylcholinesterase (AChE), which results in accumulation of acetylcholine (ACh) at autonomic and some central synapses and at autonomic postganglionic and neuromuscular junctions. As a consequence, ACh binds to, and stimulates, muscarinic and nicotinic receptors, thereby producing characteristic features. With OP insecticides (but not carbamates), "aging" may also occur by partial dealkylation of the serine group at the active site of AChE; recovery of AChE activity requires synthesis of new enzyme in the liver. Relapse after apparent resolution of cholinergic symptoms has been reported with OP insecticides and is termed the intermediate syndrome. This involves the onset of muscle paralysis affecting particularly upper-limb muscles, neck flexors, and cranial nerves some 24-96 hours after OP exposure and is often associated with the development of respiratory failure. OP-induced delayed neuropathy results from phosphorylation and subsequent aging of at least 70% of neuropathy target esterase. Cramping muscle pain in the lower limbs, distal numbness, and paresthesiae are followed by progressive weakness, depression of deep tendon reflexes in the lower limbs and, in severe cases, in the upper limbs. The therapeutic combination of oxime, atropine, and diazepam is well established experimentally in the treatment of OP pesticide poisoning. However, there has been controversy as to whether oximes improve morbidity and mortality in human poisoning. The explanation may be that the solvents in many formulations are primarily responsible for the high morbidity and mortality; oximes would not be expected to reduce toxicity in these circumstances. even if given in appropriate dose.

Clinical Toxicology of Insecticides

Some insects compete for our food, some damage construction materials and some are important disease vectors in humans and animals. Hence, it is not surprising that chemicals (insecticides) have been developed that kill insects and other arthropods. More recently introduced insecticides, such as the neonicotinoids, have been produced with the intent that humans and animals will not be harmed by their appropriate use. This chapter reviews the clinical features and management of exposure to organophosphorus (OP) and carbamate insecticides, neonicotinoids, phosphides and pyrethroids. In the developing world where the ambient temperature is often high and personal protection equipment often not worn, poisoning particularly from OP and carbamate insecticides is common in an occupational setting, though more severe cases are due to deliberate ingestion of these pesticides. Both of these insecticides produce the cholinergic syndrome. The neonicotinoids, a major new class of insecticide, were introduced on the basis that they were highly specific for subtypes of nicotinic receptors that occur only in insect tissues. However, deliberate ingestion of substantial amounts of a neonicotinoid has resulted in features similar to those found in nicotine (and OP and carbamate) poisoning, though the solvent in some formulations may have contributed to their toxicity. Phosphides interact with moisture in air (or with water or acid) to liberate phosphine, which is the active pesticide. Inhalation of phosphine, however, is a much less frequent cause of human poisoning than ingestion of a metal phosphide, though the toxicity by the oral route is also due to phosphine liberated by contact of the phosphide with gut fluids. It is then absorbed through the alimentary mucosa and distributed to tissues where it depresses mitochondrial respiration by inhibiting cytochrome c oxidase and other enzymes. Dermal exposure to pyrethroids may result in paraesthesiae, but systemic toxicity usually only occurs after ingestion, when irritation of the gastrointestinal tract and CNS toxicity, predominantly coma and convulsions, result.

Cardiac effects of magnesium sulfate pretreatment on acute dichlorvos-induced organophosphate poisoning: an experimental study in rats

Although atropine and oximes are traditionally used in the management of organophosphate poisoning, investigations have been directed to finding additional therapeutic approaches. Thus, the aim of this study was to evaluate the cardiac effects of magnesium sulfate pretreatment on dichlorvos intoxication in rats. Rats were randomly divided into three groups as control, dichlorvos, and magnesium sulfate groups. After 6 h of dichlorvos or corn oil (as a vehicle) injection, venous blood samples were collected, and cardiac tissue samples were obtained. Biochemical analyses were performed to measure some parameters on serum and cardiac tissue. Immunohistochemical analyses of apoptosis and inducible nitric oxide (NO) synthase showed no change in cardiac tissue. Serum cholinesterase levels were markedly depressed with dichlorvos, and further suppressed markedly with magnesium sulfate pretreatment. Although we have demonstrated that serum NO levels in dichlorvos and magnesium sulfate groups were lower than the control group, cardiac tissue NO levels in magnesium sulfate group were higher than the other two groups. Mortality was not significantly affected with magnesium sulfate pretreatment. Uncertainty still persists on the right strategies for the treatment of organophosphate acute poisoning; however, it was concluded that our results do not suggest that magnesium sulfate therapy is beneficial in the management of acute dichlorvos-induced organophosphate poisoning, and also further studies are required.

[Cardiac complications associated with organophosphate poisoning]

INTRODUCTION

The clinical picture of organophosphate poisoning is dominated by respiratory and neurological signs. Cardiac complications are rare, serious and little known by clinicians.

OBSERVATION

F.B, 17 years, was addressed intubated, at the emergencies after an organosphorus poisoning. At admission, the patient was comatose with a muscarinic syndrome. Her hemodynamic was stable. Chest radiography and ECG of admission were normal. A gastric washing and a treatment by atropine were quickly started. The toxicological analysis of gastric liquid showed presence of malathion. After 20hours, the patient presented a cardiogenic shock. Chest radiography showed signs of acute pulmonary edema and ECG: a circumferential endocardic ischaemia. In spite of vasopressors and positive inotropic treatment, the patient quickly died. The autopsies revealed multiple necrosis of the heart.

DISCUSSION

The cardiac symptoms are caused by many mechanisms often associated. The cardiac attack appears primarily by many electrocardiographic modifications: arrhythmias, disturb of repolarisation, conduction's disorder... On the hemodynamic plan, a circulatory insufficiency is possible. The ventricular arrhythmias, which are not treated by lidocaine or electric cardioversion are treated effectively by injection of isoproterenol and/or ventricular stimulation, and recently by the use of magnesium salts.

CONCLUSION

If the clinical picture of the IOP is dominated by neurological and respiratory signs, it is always necessary to remember the possibility of cardiac complications (early or late) whose pronostic is very often bad.

Guidelines for treating cardiac manifestations of organophosphates poisoning with special emphasis on long QT and Torsades De Pointes

Organophosphate poisoning may precipitate complex ventricular arrhythmias, a frequently overlooked and potentially lethal aspect of this condition. Acute effects consist of electrocardiographic ST-T segment changes and AV conduction disturbances of varying degrees, while long-lasting cardiac changes include QT prolongation, polymorphic tachycardia ("Torsades de Pointes"), and sudden cardiac death. Cardiac monitoring of organophosphate intoxicated patients for relatively long periods after the poisoning and early aggressive treatment of arrhythmias may be the clue to better survival. We present here a review of the literature with a focus on late cardiac arrhythmias (mainly "Torsades de pointes"), possible mechanisms, and treatment modalities, with special emphasis on postpoisoning monitoring for development of arrhythmias.

Benefits of magnesium sulfate in the management of acute human poisoning by organophosphorus insecticides

Organophosphorus chemicals (OPs) are the pesticides most often involved in serious human poisoning. Treatment of intoxication with OPs conventionally involves atropine for reduction of muscarinic signs and oximes that increase the rate of hydrolysis of the phosphorylated enzyme acetylcholinesterase (AChE). Although atropine and oximes (pralidoxime or obidoxime) are traditionally used in the management of such poisoning, their efficacy remains a major issue of debate; thus, the goal of this prospective clinical trial was to elaborate the value of magnesium sulfate (MgSO4) in the management and outcome of OP insecticide poisoning. This unicenter, randomized, single-blind trial study was conducted on patients who were acutely poisoned with OPs and admitted to the Poisoning Center of Loghman-Hakim Hospital in Tehran, Iran. In a systematic sampling, every fourth eligible patient was chosen to undergo MgSO4 treatment. Magnesium sulfate was administered at dose of 4 g/day i.v. continued for only the first 24 hours after admission. The mean daily oxime requirement and the mean daily atropine requirement were not statistically significant between two treated groups. The mortality rate and hospitalization days of patients who received MgSO4 treatment were significantly lower than those who had not received MgSO4 (P < 0.01). It is concluded that administration of MgSO4, in a dose of 4 g/day concurrent to conventional therapy, in OP acute human poisoning is beneficial by reducing the hospitalization days and rate of mortality.

Selected topics related to occupational exposures. Part V. Occupational cardiovascular disease

Cardiovascular disease is common in the United States. Several occupational exposures, such as carbon disulfide and organic nitrates, are believed to cause occupational cardiovascular disease. In addition some other agents, such as lead and cadmium, may indirectly cause cardiovascular disease through their effects on blood pressure. For other agents (ie, carbon monoxide, solvents, and chlorofluorocarbons), acute exposure and high levels may cause cardiovascular disease but may not cause cardiovascular disease through long-term or low levels. A primary care physician who has a patient with a new or unstable cardiovascular disease should obtain an occupational history to assess whether occupational exposures may be playing a role. An occupational history may indicate potential cardiovascular risks. Such risks can include exposure to certain chemicals and metals, physical factors, exertion, or psychological stress. The primary care physician should be able to assess the situation and advise the patient, as well as the employer, about restrictions or accommodations that may need to be made.

Organophosphorus poisoning and anaesthesia

Organophosphorus compounds, used as insecticides and agents of chemical warfare, are a major global cause of health problems. These irreversible inhibitors of cholinesterase produce three well-recognised clinical entities: the initial cholinergic phase, which is a medical emergency often requiring management in an intensive care unit; the intermediate syndrome, during which prolonged ventilatory care is necessary; and delayed polyneuropathy. In addition, disturbances of body temperature and endocrine function, electrolyte imbalances, immunological dysfunction and disorders of reproduction have been reported in animals and man. Vocal cord paralysis, pancreatitis, cardiac arrhythmias and a wide range of neuropsychiatric disorders are known to follow acute and chronic exposure to organophosphorus compounds. As a result of the inhibition of plasma cholinesterase, there can be increased sensitivity to drugs hydrolysed by this enzyme, e.g. suxamethonium and mivacurium. The inhibition of acetylcholinesterase causes dysfunction at the neuromuscular junction which can produce altered responses to nondepolarizing neuromuscular blockers. Anaesthetists may encounter patients exposed to organophosphorus compounds either following acute poisoning, trauma (warfare) or as patients with a wide range of nonspecific disorders presenting for surgery. The traditional use of oximes and atropine in treatment has failed to reduce the morbidity and mortality associated with poisoning. The roles of agents that have reduced the toxicity of organophosphorus compounds in animal experiments are discussed as potential therapeutic agents. There is an urgent need for accurate information on the problems associated with exposure to organophosphorus compounds. This would best be achieved by collaborative research between technologically advanced countries and developing countries, where organophosphorus compounds are a leading cause of ill health.

Magnesium and the heart: antiarrhythmic therapy with magnesium

Magnesium is an essential transmembrane and intracellular modulator of the electrical activity of cardiac cells. This review provides an up-to-date consideration of the cellular and clinical electrophysiological role of magnesium. This ubiquitous element seems to be important from both the theoretical and clinical point of view, because magnesium salts (MgSO4, MgCl2) administered intravenously are particularly effective in those arrhythmias in which the mechanism involves early or delayed after depolarization-induced triggered activity. The authors share the view that I.V. magnesium is the drug of choice in "torsade de pointes" ventricular tachycardia accompanying acquired long QT/QTU syndrome. It is complementary therapeutic agent in digitalis-induced tachycardias. Further studies are needed to elucidate magnesium's mode of action and efficacy in other types of clinical tachyarrhythmias.

QT-interval prolonging drugs: mechanisms and clinical relevance of their arrhythmogenic hazards

The antiarrhythmic principle of drug-induced QT-interval prolongation is well known. However, with the widespread use of the presently known and new Class III antiarrhythmic agents under investigation, and the growing number of agents not primarily designed as antiarrhythmic drugs that potentially cause QT prolongation, we have also become aware of the proarrhythmic hazards associated with many of these agents. The proarrhythmic risk differs markedly from one agent to another and interferes with many individual clinical variables (e.g., hypokalemia, sinus bradycardia). This paper summarizes the present data on the proarrhythmic risk of drug-induced QT prolongation, including the value and problems of the rate-corrected QT interval, the mechanisms involved in the genesis of proarrhythmia, and the clinical cofactors that facilitate the occurrence of proarrhythmic events. In addition, an extensive database provides information on the known proarrhythmic risk of all currently used QT-prolonging agents.

Torsades de Pointes

Torsades de Pointes (T.D.P.) is a ventricular dysrhythmia that is a commonly undiagnosed condition seen within Critical Care areas of most Major Metropolitan Hospitals. It is a condition that requires prompt diagnosis and treatment. Experience has shown a lack of understanding of the clinical features and the treatment of this particular life threatening dysrhythmia. This paper was compiled to increase the awareness of the health professional of Torsades de Pointes, covering areas of physiologic mechanisms, clinical features, causes of the dysrhythmia and most importantly treatment, whether it be mechanical, drug therapy or a combination of both. Controversial issues have been raised and are discussed in this paper including the use of Magnesium Sulphate as first line treatment.

Torsades de pointes: atypical rhythm, atypical treatment

For the present, treatment of the acquired Torsades de Pointes consists of removal of the causative agent, correction of the underlying electrolyte imbalance, and initiation of direct therapy. Unresponsive dysrhythmias may need magnesium therapy or cardioversion.