ECG Manifestations: The Poisoned Patient

Not only Van Gogh: a case of BRASH syndrome with concomitant digoxin toxicity

BACKGROUND

Bradycardia, renal failure, atrioventricular (AV) node blocking, shock, and hyperkalemia syndrome is a potentially life-threatening clinical condition characterized by bradycardia, renal failure, atrioventricular (AV) node blocking, shock, and hyperkalemia. It constitutes a vicious circle in which the accumulation of pharmacologically active compounds and hyperkalemia lead to hemodynamic instability and heart failure.

CASE PRESENTATION

A 66-year-old Caucasian female patient was admitted to the emergency department presenting with fatigue and bradycardia. Upon examination, the patient was found to be anuric and hypotensive. Laboratory investigations revealed metabolic acidosis and hyperkalemia. Clinical evaluation suggested signs of digoxin toxicity, with serum digoxin concentrations persistently elevated over several days. Despite the implementation of antikalemic measures, the patient's condition remained refractory, necessitating renal dialysis and administration of digoxin immune fab.

CONCLUSION

Bradycardia, renal failure, atrioventricular (AV) node blocking, shock, and hyperkalemia syndrome is a life-threatening condition that requires prompt management. It is important to also consider potential coexisting clinical manifestations indicative of intoxication from other pharmacological agents. Specifically, symptoms associated with the accumulation of drugs eliminated via the kidneys, such as digoxin. These manifestations may warrant targeted therapeutic measures.

Amitriptyline intoxication in bullfrogs causes widening of QRS complexes in electrocardiogram

Amitriptyline intoxication is caused by its suicidal or accidental overdose. In the present study, by intravenously injecting 1.5 or 3.0 mg/kg amitriptyline into bullfrogs, we actually revealed that amitriptyline causes the widening of QRS complexes in electrocardiogram (ECG). In simultaneous recordings of the cardiac action potential, amitriptyline decreased the slope of phase 0 in the action potential, indicating the inhibition of the inward sodium currents during this phase. The following treatment with sodium bicarbonate quickly restored the widened QRS complexes in the ECG, demonstrating the counteraction with the sodium channel blockade caused by amitriptyline. The dual recordings of ECG waveforms and the action potential in cardiomyocytes enabled us to demonstrate the mechanisms of characteristic ECG abnormalities caused by amitriptyline intoxication.

Optimising alkalinisation and its effect on QRS narrowing in tricyclic antidepressant poisoning

AIMS

The objectives were to determine the effect of NaHCO₃ and/or mechanical ventilation on the biochemical profile and serum alkalinisation in tricyclic antidepressant (TCA) poisoning and investigate the impact of effective alkalinisation therapy on the QRS interval in TCA poisoning.

METHODS

This was a retrospective review of TCA poisonings from three Australian toxicology units and a poisons information centre (Jan 2013 to Jan 2019). We included patients with TCA toxicity who ingested>10 mg/kg or had clinically significant toxicities consistent with TCA poisoning, and analysed patients' clinical, electrocardiogram and biochemical data.

RESULTS

Of 210 patients, 84 received NaHCO₃ and ventilation (dual therapy), 12 NaHCO₃ , 46 ventilation and 68 supportive care treatment. When compared with single/supportive groups, patients who received dual therapy had taken a significantly higher median dose of TCA (1.5 g vs1.3 g, P < .001), a longer median maximum QRS interval (124 ms, interquartile ranges [IQR] 108-138 vs106 ms, IQR 98-115, P < .001) and were more likely to have seizures (14% vs3%, P = .006) and arrhythmias (17% vs1%, P < .001). The dual therapy group demonstrated greater increases in serum pH (median 0.11, IQR 0.04-0.17) compared to the single/supportive therapy group (median 0.03, IQR -0.01-0.09, p < .001). A greater proportion of patients reached the target pH 7.45-7.55 in the dual therapy group (59%) compared to the single/supportive therapy group (10%) (P < .001). For each 100 mmol bolus of NaHCO₃ given, the median increase in serum sodium was 2.5 mmol/L (IQR 1.5-4.0). QRS narrowing occurred twice as quickly in the dual therapy vs single/supportive therapy group.

CONCLUSIONS

A combination of NaHCO₃ and mechanical ventilation was most effective in achieving serum alkalinisation and was associated with a more rapid narrowing of the QRS interval. We advise that the maximal dose of NaHCO₃ should be <400 mmol (6 mmol/kg).

Validation of Corrected and Dispersed QT as Predictors of Adverse Outcomes in Acute Cardiotoxicities

Acute cardiovascular poisoning is a major cause of adverse outcomes in poisoning emergencies. The prognostic validity of corrected QT (QTc) and dispersed QT (QTd) in these outcomes is still limited. The present study aimed to determine the risk factors of mortality, adverse cardiovascular events (ACVE), and intensive care unit (ICU) admission in patients with acute cardiovascular toxicities and assess the validity of QTc and QTd intervals in predicting these outcomes. This study was conducted on adult patients admitted to Tanta University Poison Control Center with a history of acute cardiotoxic drugs or toxins exposure. The demographic and toxicological data of patients were recorded. Clinical examination, routine laboratory investigations, ECG grading, and measurement of QTc and QTd were performed. The patients were grouped according to their adverse outcomes. Among the included patients, 51 (31.48%) patients died, 61 (37.65%) patients had ACVE, and 68 (41.98%) patients required ICU admission. The most common cause of poisoning is aluminum phosphide, followed by cholinesterase inhibitors. QTd and QTdc showed no significant difference among outcome groups. The best cut-off values of QTc to predict mortality, ACVE, and ICU admission were > 491.1 ms, > 497.9 ms, and ≥ 491.9 ms, respectively. The derived cut-off QTc values were independent predictors for all adverse outcomes after adjusting for poison type, serum HCO3, and pulse. The highest odds ratios for all adverse outcomes were observed in aluminum phosphide poisoning and low HCO3 < 18 mmol/L. Thus, serum HCO3 and QTc interval should be monitored for acute cardiotoxicities, especially in aluminum phosphide and cholinesterase inhibitors poisoning.

The limited utility of screening laboratory tests and electrocardiograms in the management of unintentional asymptomatic pediatric ingestions

BACKGROUND

Suspected ingestions are a common chief complaint to the emergency department although the majority of ingestions by children are insignificant.

OBJECTIVE

Assess the utility of screening laboratory tests and Electrocardiograms (ECGs) in unintentional asymptomatic pediatric poisonings.

METHODS

Retrospective chart review at a tertiary care children's hospital and a regional poison center of patients less than 12 years of age using ICD-9 codes from January 2005 through December 2008. Laboratory or ECG results requiring intervention and/or direct treatment, a non-RPC subspecialty consultation, and/or prolonged Emergency Department stay was considered changed management.

RESULTS

Five hundred ninety five suspected ingestions met our criteria. The median age was 2.6 years (IQR 1.6, 3.0 years) and 56% were male. One laboratory test or ECG was obtained in 233 patients (39%). Of 24 screening ECGs, 32 complete blood counts and 34 blood gases, none were clinically significant. Fifty-two patients received screening metabolic panels, 3 were abnormal and 2 changed management (anion gap metabolic acidosis with unsuspected salicylate ingestions). None of the 127 (21%) screening acetaminophen levels changed management. Two of sixty-five (13%) screening salicylate levels changed management. Three screening urine toxicology tests on patients with altered mental status were positive without ingestion history. No patient under the age of 12 years with normal vital signs and normal mental status had positive screening tests.

CONCLUSIONS

Screening laboratory tests and ECGs were of limited utility and rarely changed management despite being ordered in a significant number of patients. Screening tests are rarely indicated in unintentional overdoses in children who are asymptomatic.

Synthesis, characterization, and assessment of cytotoxic, antiproliferative, and antiangiogenic effects of a novel procainamide hydrochloride-poly(maleic anhydride-co-styrene) conjugate

Poly(maleic anhydride-co-styrene) (MAST) was synthesized by a free-radical polymerization reaction. A bioactive molecule, procainamide hydrochloride (PH), was then conjugated to MAST. The conjugation product was named as MAST/PH. Structural characterization of MAST and MAST/PH was carried out by Fourier Transform Infrared and Nuclear Magnetic Resonance spectroscopy. Their molecular weights were determined by size-exclusion chromatography. A mechanism was then suggested for the conjugation reaction. The results of the cytotoxicity assay, employing a mouse fibroblast cell line (L929), indicated that MAST/PH had no cytotoxicity at concentrations [Formula: see text] 62 μg mL(-1) (p > 0.05). Antiproliferative activities of MAST/PH and PH were determined by the BrdU cell proliferation ELISA assay, using C6 and HeLa cell lines. In the experiment, two anticancer chemotherapy drugs, cisplatin and 5-fluorouracil, were included as positive control. Antiproliferative activity results demonstrated that MAST/PH yielded the highest suppression profile (approximately 42%) at 20 μg/ml, while free PH exerted the same activity at 100 μg/ml. Interestingly, both MAST/PH and PH suppressed the proliferation of only one of the cell lines, C6 cells. Both cisplatin and 5-fluorouracil yielded approximately 60% antiproliferative activity on C6 cells at 20 and 100 μg/ml concentrations. Antiangiogenic capacity of both MAST and MAST/PH was also investigated by using the chicken chorioallantoic membrane assay. Results obtained indicated that while MAST/PH could be included into the category of good antiangiogenic substances, the activity score of MAST was within the weak category.

Verapamil inhibits the glucose transport activity of GLUT1

Calcium channel blocker toxicity has been associated with marked hyperglycemia responsive only to high-dose insulin therapy. The exact mechanism(s) of this induced hyperglycemia has not been clearly delineated. The glucose transporter GLUT1 is expressed in a wide variety of cell types and is largely responsible for a basal level of glucose transport. GLUT1 also is activated by cell stress. The specific purpose of this study was to investigate the effects of the calcium channel blocker verapamil on the glucose uptake activity of GLUT1 in L929 fibroblasts cells. Dose-dependent effects of verapamil on glucose uptake were studied using L929 fibroblast cells with 2-deoxyglucose. Verapamil had a dose-dependent inhibitory effect on both basal and stress-activated transport activity of GLUT1. Basal activity was inhibited 50% by 300 μM verapamil, while 150 μM verapamil completely inhibited the activation induced by the stress of glucose deprivation. These effects were reversible and required verapamil to be present during the stress. Alteration of calcium concentrations by addition of 5 mM CaCl₂ or 4 mM EDTA had no effect on verapamil action. This study reveals the unique finding that verapamil has inhibitory effects on the transport activity of GLUT1 independent of its effects on calcium concentrations. The inhibition of GLUT1 may be one of the contributing factors to the hyperglycemia observed in CCB poisoning.

Electrocardiographic abnormalities associated with poisoning

This article will review the cardiovascular toxicities of various medications, stressing the electrocardiographic presentation--both rhythm and morphological issues--and emphasizing recognition and management issues. Cardiovascular toxins are grouped into categories causing similar electrocardiographic effects, including the potassium efflux blockers, sodium channel blockers, sodium-potassium adenosine triphosphatase blockers (ie, digitalis compounds), calcium channel blockers, and beta-adrenergic blockers. This article reviews the various electrocardiographic abnormalities associated with these 5 classes of agents, ranging from morphological abnormalities and conduction blocks to brady- and tachyarrhythmias.

A Critical Reconsideration of the Clinical Effects and Treatment Recommendations for Sodium Channel Blocking Drug Cardiotoxicity

The cardiac sodium channel is comprised of proteins that span the cardiac cell membrane and form the channel pore. Depolarisation causes the proteins to move and open the sodium channel. Once the channel is open (active conformation), sodium ions move into the cell. The channel then changes from the active conformation to an inactive conformation - the channel remains open, but influx of sodium ions ceases. Recovery occurs as the channel moves from the inactive conformation back to the closed conformation and is then ready to open following the next depolarisation. Sodium channel blocking drugs (NCBDs) occupy receptors in the channel during the active and inactive conformations. The drug dissociates from most of the channel receptors during recovery, but the time it takes the drug to dissociate slows recovery. The slowed recovery prolongs conduction time, the main toxicity of NCBD overdose. Conduction time is further prolonged if heart rate increases as there are more available active and inactive conformations/unit time, which increases channel receptor binding sites for the NCBD. In addition to prolonging conduction time, NCBDs also decrease inotropy. Treatment of NCBD cardiotoxicity has been based on in vitro and animal experiments, and case reports. Assumptions based on this evidence must now be reassessed. For example, canines consistently develop ventricular tachycardia (VT) when tricyclic antidepressants (TCAs) are administered. Much of the literature discussing NCBD cardiotoxicity assumes that TCA poisoning induces VT in humans with the same regularity that occurs in canines. Seemingly, in support of this assumption was the finding that patients with remote myocardial infarction developed VT when therapeutically ingesting a NCBD. However, conduction is prolonged in myocardium that is or has been ischaemic. NCBD prolong conduction more in previously ischaemic myocardium than in normal myocardium, which causes nonuniform conduction and allows the development of re-entrant arrhythmias such as VT. Although some nonuniform conduction may occur in the healthy heart following a NCBD overdose, there is no evidence that nonuniform conduction occurs to the extent that it will cause re-entrant arrhythmias in this setting. Using various animal models and a variety of NCBDs, sodium ions, bicarbonate ions and alkalosis have been compared for the treatment of ventricular arrhythmias, hypotension and mortality. The results of these experiments have been extrapolated to NCBD overdose in humans. Animal models and single treatment approaches may have narrowed our scope. More recent evidence indicates that properties of each individual NCBD may require unique treatment. There is limited evidence that glucagon, which increases initial sodium ion influx into the cardiac cell, should be considered early in the treatment of cardiotoxicity. Another consideration may be treatment of NCBD with faster kinetics. Conduction time is decreased if a NCBD occupying the receptor is replaced by a NCBD that moves off and on the receptor more quickly. There is less evidence for this treatment, as risk may be greater. With greater understanding of the sodium channel and NCBDs, we must reassess our approach to the treatment of patients with healthy hearts who overdose on NCBD.