Treating arrhythmias with adjunctive magnesium: identifying future research directions

The Impact of Chronic Magnesium Deficiency on Excitable Tissues-Translational Aspects

Neuromuscular excitability is a vital body function, and Mg2+ is an essential regulatory cation for the function of excitable membranes. Loss of Mg2+ homeostasis disturbs fluxes of other cations across cell membranes, leading to pathophysiological electrogenesis, which can eventually cause vital threat to the patient. Chronic subclinical Mg2+ deficiency is an increasingly prevalent condition in the general population. It is associated with an elevated risk of cardiovascular, respiratory and neurological conditions and an increased mortality. Magnesium favours bronchodilation (by antagonizing Ca2+ channels on airway smooth muscle and inhibiting the release of endogenous bronchoconstrictors). Magnesium exerts antihypertensive effects by reducing peripheral vascular resistance (increasing endothelial NO and PgI2 release and inhibiting Ca2+ influx into vascular smooth muscle). Magnesium deficiency disturbs heart impulse generation and propagation by prolonging cell depolarization (due to Na+/K+ pump and Kir channel dysfunction) and dysregulating cardiac gap junctions, causing arrhythmias, while prolonged diastolic Ca2+ release (through leaky RyRs) disturbs cardiac excitation-contraction coupling, compromising diastolic relaxation and systolic contraction. In the brain, Mg2+ regulates the function of ion channels and neurotransmitters (blocks voltage-gated Ca2+ channel-mediated transmitter release, antagonizes NMDARs, activates GABAARs, suppresses nAChR ion current and modulates gap junction channels) and blocks ACh release at neuromuscular junctions. Magnesium exerts multiple therapeutic neuroactive effects (antiepileptic, antimigraine, analgesic, neuroprotective, antidepressant, anxiolytic, etc.). This review focuses on the effects of Mg2+ on excitable tissues in health and disease. As a natural membrane stabilizer, Mg2+ opposes the development of many conditions of hyperexcitability. Its beneficial recompensation and supplementation help treat hyperexcitability and should therefore be considered wherever needed.

An Update on the Use of Natural Pigments and Pigment Nanoparticle Adducts for Metal Detection Based on Colour Response

Natural pigments occur in plants as secondary metabolites and have been used as safe colourants in food. Studies have reported that their unstable colour intensity might be related to metal ion interaction, which leads to the formation of metal-pigment complexes. This underlines the need for further investigations on the use of natural pigments in metal detection using colorimetric methods, since metals are important elements and can be hazardous when present in large amounts. This review aimed to discuss the use of natural pigments (mainly betalains, anthocyanins, curcuminoids, carotenoids, and chlorophyll) as reagents for portable metal detection based on their limits of detection, to determine which pigment is best for certain metals. Colorimetric-related articles over the last decade were gathered, including those involving methodological modifications, sensor developments, and a general overview. When considering sensitivity and portability, the results revealed that betalains are best applied for copper, using a smartphone-assisted sensor; curcuminoids are best applied for lead, using a curcumin nanofiber; and anthocyanin is best applied for mercury, using anthocyanin hydrogel. This provides a new perspective on the use of colour instability for the detection of metals with modern sensor developments. In addition, a coloured sheet representing metal concentrations may be useful as a standard to support on-site detection with trials on masking agents to improve selectivity.

The Role of Hypomagnesemia in Cardiac Arrhythmias: A Clinical Perspective

The importance of magnesium (Mg²⁺), a micronutrient implicated in maintaining and establishing a normal heart rhythm, is still controversial. It is known that magnesium is the cofactor of 600 and the activator of another 200 enzymatic reactions in the human organism. Hypomagnesemia can be linked to many factors, causing disturbances in energy metabolism, ion channel exchanges, action potential alteration and myocardial cell instability, all mostly leading to ventricular arrhythmia. This review article focuses on identifying evidence-based implications of Mg²⁺ in cardiac arrhythmias. The main identified benefits of magnesemia correction are linked to controlling ventricular response in atrial fibrillation, decreasing the recurrence of ventricular ectopies and stopping episodes of the particular form of ventricular arrhythmia called torsade de pointes. Magnesium has also been described to have beneficial effects on the incidence of polymorphic ventricular tachycardia and supraventricular tachycardia. The implication of hypomagnesemia in the genesis of atrial fibrillation is well established; however, even if magnesium supplementation for rhythm control, cardioversion facility or cardioversion success/recurrence of AF after cardiac surgery and rate control during AF showed some benefit, it remains controversial. Although small randomised clinical trials showed a reduction in mortality when magnesium was administered to patients with acute myocardial infarction, the large randomised clinical trials failed to show any benefit of the administration of intravenous magnesium over placebo.

The Role of Magnesium in the Management of Atrial Fibrillation with Rapid Ventricular Rate

Background

Atrial fibrillation is currently managed with a variety of rate controlling and antiarrhythmic agents. Often, magnesium is used as adjunctive therapy, however, the benefit it provides in managing Afib with RVR has been debated. This study aimed to determine if IV MgSO4 administration in conjunction with standard therapy provides any synergistic effect in acute and prolonged control of Afib with RVR.

Methods

This was a retrospective study involving ninety patients with episodes of Afib with RVR during their hospitalization. The treatment group included those that had received magnesium (n=32) along with standard management and the control group (n=58) received only standard management. Heart rates at different time intervals were collected. Dose dependent effects of IV MgSO4 on heart rates were also evaluated.

Results

Patients that received magnesium had a lower mean heart rate (85 BPM versus 96 BPM, P<0.05) 24 hours after onset of the episode. Also, in the last 16 hours of observation, it appeared that administration of higher levels of magnesium resulted in statistically lower heart rates. In the group of patients that received 2 grams of magnesium, the mean heart rate at 8 hours was 103.4 beats/min and 84.8 beats/min at 24 hours (p<0.01). This same trend was not seen in patients that received 1 gram of magnesium or in the control group.

Conclusions

Overall, the use of IV MgSO4 as an adjunctive treatment permitted normalization of the heart rate progressively that continued to at least 24 hours.

Successful management of massive lamotrigine extended-release intoxication in a dog

A 3-year-old spayed female Siberian Husky presented for evaluation following ingestion of approximately 429 mg/kg of lamotrigine extended-release. She demonstrated severe neurologic and cardiac signs and was treated with lipid emulsion, anticonvulsants, antiarrhythmics and aggressive decontamination and supportive care. She was successfully discharged from the hospital 5 days later.

Ionized Hypomagnesemia Is Associated With Increased Incidence of Postoperative Atrial Fibrillation After Esophageal Resection: A Retrospective Study

Introduction: Postoperative atrial fibrillation (POAF) is common after surgery for esophageal cancer and may prolong hospitalization and elevate mortality. POAF and hypomagnesemia are linked, but this is based on studies showing an association of POAF with serum total magnesium (tMg). In contrast, the relationship of POAF with ionized magnesium (iMg), which has physiological activity, has not been examined. In this study, the association between hypomagnesemia and POAF was investigated retrospectively to examine iMg as a possible predictive factor for POAF.

Methods: The subjects were 151 patients who underwent right transthoracoabdominal subtotal esophagectomy at Saitama Medical Center between January 2011 and December 2020. The incidence of POAF and predictive factors were examined retrospectively. Perioperative predictive factors were subjected to univariate analysis, and items with P<0.1 were then included in multivariate analysis, along with five potential POAF predictors reported in the literature (age, gender, body mass index, hypertension, and diabetes mellitus). P<0.05 was regarded as significant in the multivariate analysis.

Results: Of the 151 patients, 34 (23%) developed POAF. In univariate analysis, six factors with P<0.1 (oral statin, dyslipidemia, iMg level after anesthesia induction, maximum and minimum iMg during surgery, and iMg level immediately before admission to ICU) were identified. In multivariate analysis including these and the five literature factors as explanatory variables, iMg immediately before admission to ICU emerged as a predictive factor for POAF (iMg≥0.46 mmol/L, OR 0.32, 95%CI 0.14-0.74, p=0.01) (standard iMg range: 0.48-0.60 mmol/L).

Conclusion: The iMg level immediately before admission to ICU may be associated with the development of POAF. A further study is needed to evaluate changes in iMg in the ICU and iMg at the time of onset of POAF.

Magnesium Citrate Increases Pain Threshold and Reduces TLR4 Concentration in the Brain

Magnesium is being investigated in various clinical conditions and has shown to be effective in some chronic pain models. However, it is not clear if oral magnesium use affects pain perception in acute pain. TLR4's (toll-like receptor) role in pain perception has emerged through its role in immune pathways and ion channels. The aim of this study is to investigate the effect of a single oral dose of magnesium citrate on pain conduction and whether with magnesium, the expression of TLR4 changes in the acute phase. Following a single dose of 66-mg/kg magnesium citrate administration to male Balb-c mice, pain perception (via hot-plate test), motor conduction (via electrophysiological recording, forelimb grip strength, rotarod and open-field tests), and emotional state (via elevated plus maze and forced swim test) were evaluated. In behavioral experiments, the control group was compared with applied magnesium for three different time groups (4, 8, 24 h). TLR4 expression was measured in four groups: control, magnesium (Mg), hot plate (HP), and Mg + HP. Hot plate latency was prolonged in the magnesium group (p < 0.0001) and electrophysiological recordings (p < 0.001) and forelimb grip strength measurement (p < 0.001) determined motor latency. Compared with the untreated hot plate group, TLR4 levels was lower in the brain (p = 0.023) and higher in the sciatic nerve (p = 0.001) in the magnesium-treated hot plate group. Consequently, the study indicated a single dose of magnesium citrate appeared to cause weakening in the transmission and perception of nociceptive pain. TLR4 may act as a regulator in magnesium's effects on pain perception.

Magnesium, Oxidative Stress, Inflammation, and Cardiovascular Disease

Hypomagnesemia is commonly observed in heart failure, diabetes mellitus, hypertension, and cardiovascular diseases. Low serum magnesium (Mg) is a predictor for cardiovascular and all-cause mortality and treating Mg deficiency may help prevent cardiovascular disease. In this review, we discuss the possible mechanisms by which Mg deficiency plays detrimental roles in cardiovascular diseases and review the results of clinical trials of Mg supplementation for heart failure, arrhythmias and other cardiovascular diseases.

Ionized or Total Magnesium levels, what should we measure in critical ill patients?

Monitoring and measuring magnesium (Mg) values are essential to prevent the development of numerous complications in perioperative medicine and critically ill patients. Although previous studies suggest that measuring free ionized magnesium (iMg) is more useful for estimating Mg status, clinicians currently rely on measurement of total serum magnesium to determine if supplemental magnesium is needed. In this review, we analyzed the recent literature to decide whether it is better to measure ionized serum Mg or total serum Mg when assessing magnesium status, whether iMg predicts clinical outcome, and what are the difficulties in measuring serum iMg levels in intensive care patients and perioperative medicine.

Ibutilide with magnesium for conversion of atrial fibrillation or flutter in rheumatic heart disease patients: Ibutilide with magnesium for chemical cardioversion of atrial fibrillation or flutter

Background

Data on adjunctive use of magnesium with ibutilide for conversion of persistent rheumatic atrial fibrillation and flutter to sinus rhythm is lacking.

Aim

We aimed to study the efficacy of adjunctive supplementation of intravenous magnesium with ibutilide for conversion of persistent rheumatic atrial fibrillation and flutter to sinus rhythm and to define a definite level of serum magnesium which leads to significant increase in rates of such conversion.

Methods and results

This was a prospective study including 33 Rheumatic heart disease patients (13 males and 20 females) with mean age of 49.27 ± 11.4 years and persistent AF or AFl. All patients received intravenous magnesium to raise serum magnesium level in range of 4 mg/dl to 4.5 mg/dl prior to administration of Ibutilide. 25 out of 33 (76%) patients converted to sinus rhythm. Upon univariate analysis, presence of background beta blocker therapy, serum potassium and magnesium at time of Ibutilide injection were found to have significant relation with conversion to sinus rhythm. Upon multivariate analysis serum magnesium level at the time of Ibutilide injection was found to have significant contribution on post injection rhythm reversal (p-value = 0.006).

The level of magnesium at 3.8 mg/dl was found to have maximum sensitivity of 96% and specificity of 62.5% for conversion to sinus rhythm by ibutilide with magnesium (p-value< 0.05).

Conclusions

Ibutilide is highly effective in cardioversion of persistent rheumatic atrial fibrillation/flutter patients. Raising Serum Magnesium levels above 3.8 mg/dl significantly improves efficacy of ibutilide.

Mg2+ restriction downregulates NCC through NEDD4-2 and prevents its activation by hypokalemia

Hypomagnesemia is associated with reduced kidney function and life-threatening complications and sustains hypokalemia. The distal convoluted tubule (DCT) determines final urinary Mg²⁺ excretion and, via activity of the Na⁺-Cl^- cotransporter (NCC), also plays a key role in K⁺ homeostasis by metering Na⁺ delivery to distal segments. Little is known about the mechanisms by which plasma Mg²⁺ concentration regulates NCC activity and how low-plasma Mg²⁺ concentration and K⁺ concentration interact to modulate NCC activity. To address this, we performed dietary manipulation studies in mice. Compared with normal diet, abundances of total NCC and phosphorylated NCC (pNCC) were lower after short-term (3 days) or long-term (14 days) dietary Mg²⁺ restriction. Altered NCC activation is unlikely to play a role, since we also observed lower total NCC abundance in mice lacking the two NCC-activating kinases, STE20/SPS-1-related proline/alanine-rich kinase and oxidative stress response kinase-1, after Mg²⁺ restriction. The E3 ubiquitin-protein ligase NEDD4-2 regulates NCC abundance during dietary NaCl loading or K⁺ restriction. Mg²⁺ restriction did not lower total NCC abundance in inducible nephron-specific neuronal precursor cell developmentally downregulated 4-2 (NEDD4-2) knockout mice. Total NCC and pNCC abundances were similar after short-term Mg²⁺ or combined Mg²⁺-K⁺ restriction but were dramatically lower compared with a low-K⁺ diet. Therefore, sustained NCC downregulation may serve a mechanism that enhances distal Na⁺ delivery during states of hypomagnesemia, maintaining hypokalemia. Similar results were obtained with long-term Mg²⁺-K⁺ restriction, but, surprisingly, NCC was not activated after long-term K⁺ restriction despite lower plasma K⁺ concentration, suggesting significant differences in distal tubule adaptation to acute or chronic K⁺ restriction.

Main Considerations of Cardiogenic Shock and Its Predictors: Systematic Review

The mortality rate of post-infarction cardiogenic shock (CS) was 80.0-90.0%. Recent studies show a significant reduction of hospital mortality to approximately 50.0%. CS is defined as systemic tissue hypoperfusion resulting from systolic and/or diastolic heart dysfunction, the main cause of which is acute myocardial infarction (AMI). The main predictors are biological markers such as troponin, CKMB and lactate. A systematic literature review and meta-analysis is performed in order to present and correlate the main literary findings on CS and its evolution with possible changes in biomarkers such as troponin, lactate and CKMB. After criteria of literary search with the use of the mesh terms: cardiogenic shock; acute myocardial infarction; biomarkers; troponin; CKMB; lactate; clinical trials and use of the bouleanos "and" between the mesh terms and "or" among the historical findings. In the main databases such as Pubmed, Medline, Bireme, EBSCO, Scielo, etc., a total of 96 papers that were submitted to the eligibility analysis were collated and, after that, 41 studies were selected, following the rules of systematic review - PRISMA (Transparent reporting of systematic reviews and meta-analyzes-http://www.prisma-statement.org/). Some risk factors for its development in AMI are advanced age, female gender, anterior wall infarction, diabetes mellitus, systemic arterial hypertension, previous history of infarction and angina. The CS associated with AMI depends on its extent and its complications, being the main ones: mitral regurgitation, rupture of the interventricular septum and rupture of the free wall of the left ventricule. The diagnosis is based on the clinical manifestations, such as mental confusion, oliguria, hypotension, tachycardia, fine pulse, sweating, and cold extremities; in hemodynamic aspects: systolic blood pressure was < 90.0 mm Hg or 30 mm Hg below baseline, pulmonary capillary pressure was > 18.0 mm Hg and cardiac index was < 2.2 L/min/m². Laboratory and imaging exams should be requested to evaluate the possible etiology of CS, its systemic repercussions and comorbidities. The treatment aims at the rapid reestablishment of the blood flow in the affected artery, to improve the patient's prognosis. The biomarkers dosage in the daily clinical practice of the different cardiological centers can facilitate the diagnosis and the conduction of the dubious cases and the best evaluation of the degree of myocardial suffering after CS.

Enhanced Late Na and Ca Currents as Effective Antiarrhythmic Drug Targets

While recent advances clarified the molecular and cellular modes of action of antiarrhythmic drugs (AADs), their link to suppression of dynamical arrhythmia mechanisms remains only partially understood. The current classifications of AADs (Classes I, III, and IV) rely on blocking peak Na, K and L-type calcium currents (I_Ca,L), with Class II with dominant beta receptor blocking activity and Class V including drugs with diverse classes of actions. The discovery that the calcium and redox sensor, cardiac Ca/calmodulin-dependent protein kinase II (CaMKII) enhances both the late Na (I_Na-L) and the late I_Ca,L in patients at high risk of VT/VF provided a new and a rational AAD target. Pathological rise of either or both of I_Na-L and late I_Ca,L are demonstrated to promote cellular early afterdepolarizations (EADs) and EAD-mediated triggered activity that can initiate VT/VF in remodeled hearts. Selective inhibition of the I_Na-L without affecting their peak transients with the highly specific prototype drug, GS-967 suppresses these EAD-mediated VT/VFs. As in the case of I_Na-L, selective inhibition of the late I_Ca,L without affecting its peak with the prototype drug, roscovitine suppressed oxidative EAD-mediated VT/VF. These findings indicate that specific blockers of the late inward currents without affecting their peaks (gating modifiers), offer a new and effective AAD class action i.e., “Class VI.” The development of safe drugs with selective Class VI actions provides a rational and effective approach to treat VT/VF particularly in cardiac conditions associated with enhanced CaMKII activity such as heart failure.