The electrocardiographic manifestations of cyclic antidepressant therapy and overdose: a review

Antidotal Sodium Bicarbonate Therapy: Delayed QTc Prolongation and Cardiovascular Events

BACKGROUND

Sodium bicarbonate therapy (SBT) is currently indicated for the management of a variety of acute drug poisonings. However, SBT effects on serum potassium concentrations may lead to delayed QTc prolongation (DQTP), and subsequent risk of adverse cardiovascular events (ACVE), including death. Emergency department (ED)-based studies evaluating associations between SBT and ACVE are limited; thus, we aimed to investigate the association between antidotal SBT, ECG changes, and ACVE.

METHODS

This was a secondary data analysis of a consecutive cohort of ED patients with acute drug overdose over 3 years. Demographic and clinical data as well as SBT bolus dosage and infusion duration were collected, and outcomes were compared with an unmatched consecutive cohort of patients with potential indications for SBT but who did not receive SBT. The primary outcome was the occurrence of ACVE, and secondary outcomes were delayed QTc (Bazett) prolongation (DQTP), and death. Propensity score and multivariable adjusted analyses were conducted to evaluate associations between adverse outcomes and SBT administration. Planned subgroup analysis was performed for salicylates, wide QRS (> 100 ms), and acidosis (pH < 7.2).

RESULTS

Out of 2365 patients screened, 369 patients had potential indications for SBT, of whom 31 (8.4%) actually received SBT. In adjusted analyses, SBT was found to be a significant predictor of ACVE (aOR 9.35, CI 3.6-24.1), DQTP (aOR 126.7, CI 9.8-1646.2), and death (aOR 11.9, CI 2.4-58.9). Using a propensity score model, SBT administration was associated with ACVE (OR 5.07, CI 1.8-14.0). Associations between SBT and ACVE were maintained in subgroup analyses of specific indications for sodium channel blockade (OR 21.03, CI 7.16-61.77) and metabolic acidosis (OR: 6.42, 95% CI: 1.20, 34.19).

CONCLUSION

In ED patients with acute drug overdose and potential indications for SBT, administration of SBT as part of routine clinical care was an independent, dose-dependent, predictor of ACVE, DQTP, and death. This study was not designed to determine whether the SBT or acute overdose itself was causative of ACVE; however, these data suggest that poisoned patients receiving antidotal SBT require close cardiovascular monitoring.

Opipramol Overdose Presented with Wide-Complex Tachycardia to the Emergency Department

Opipramol is an antidepressant and anxiolytic drug similar in structure to tricyclic antidepressants (TCAs) but it is primarily used for the treatment of generalized anxiety disorders. Unlike many TCAs, opipramol has no reuptake-inhibiting properties. Opipramol acts as a high affinity sigma receptor agonist. Opipramol acts as a low to moderate affinity antagonist for the dopamine-2 (D2), 5-hydroxtryptamine (5-HT2), histamine 1 (H1), histamine 2 (H2), and muscarinic acetylcholine receptors accounting for its antihistamine effects, and muscarinic anticholinergic properties. Here, we report a rare case of opipramol overdose case involving a 18-year-old woman, presenting to our emergency department (ED) with loss of consciousness and wide-complex tachycardia. A firm diagnosis of opipramol overdose was made on the basis of clinical, laboratory and electrocardiogram findings.

Clinical utility of aVR-The neglected electrocardiographic lead

BACKGROUND

Several studies suggest that electrocardiographers tend to neglect lead aVR during the reading of electrocardiograms (ECGs). Our objective was to provide a systematic review of the most important diagnostic and prognostic uses of lead aVR.

METHODS

We performed a thorough review of the literature about the lead aVR using PubMed, MEDLINE and the archives of the University at Buffalo libraries.

RESULTS

We found that lead aVR may provide important additional information in the diagnosis of coronary artery disease. It may provide a clue to the location of a lesion as well as the possibility of three vessel disease during an acute coronary syndrome. Lead aVR was found useful in the locus of arrhythmias and in differentiation of narrow and wide QRS complex tachycardias. It provides useful prognostic information for patients with the Brugada syndrome and tricyclic antidepressant toxicity. Lead aVR provides alternative criteria for the electrocardiographic diagnosis of left ventricular hypertrophy and left anterior fascicular block.

CONCLUSION

Lead aVR provides very important additional diagnostic and prognostic information in multiple cardiac conditions and can be used either alone or in conjunction with other electrocardiographic leads.

Application of microarray technology in psychotropic drug trials

Microarrays can be manufactured to detect hundreds of thousands of polymorphisms in DNA from patients in psychotropic drug trials. Some of these polymorphisms may be useful as pharmacogenetic predictors of treatment outcomes. We tested a microarray designed to detect common polymorphisms in the CYP2D6 gene that encodes debrisoquine hydroxylase (DH). DH is involved in the hepatic metabolism of many psychotropics. CYP2D6 genotypes predicted plasma steady state concentrations of nortriptyline, a classic DH substrate, in a sample of geriatric patients with major depression. However, in a sample of 246 geriatric patients treated with paroxetine or mirtazapine, both of which are metabolized in part by DH, CYP2D6 genotypes determined with microarrays did not predict discontinuations due to adverse events or severity of adverse events. For modern antidepressants such as paroxetine and mirtazapine, pharmacokinetic factors that are regulated by CYP2D6 such as plasma drug concentrations may be less important than pharmacodynamic factors in determining outcomes. Studies of single candidate genes such as CYP2D6 have only begun to utilize the potential of microarrays for pharmacogenetic prediction. Yet, there is controversy as to whether genome-wide studies designed to detect millions of genotypes with microarrays will lead to new pharmacogenetic discoveries, or whether a more focused, hypothesis-driven approach is better.

Are one or two dangerous? Tricyclic antidepressant exposure in toddlers

Tricyclic antidepressants (TCA), increasingly prescribed for multiple indications in children and adults, are responsible for many pediatric poisonings. Though the majority of TCA exposures in this age group remain asymptomatic, several reports in the English language literature reveal significant morbidity as well as fatalities in toddlers, primarily from imipramine and desipramine. These few cases indicate that doses of 10-20 mg/kg (one to two pills) have the potential for toxicity and fatalities. More recent studies have focused on the relative safety of small exposures suggesting that with doses less than 5 mg/kg the patient may be safely observed at home. Though further studies are necessary to determine the exact dosing that places the child at risk, the authors recommend a 6-h Emergency Department observation period for children who ingest more than 5 mg/kg of most TCAs, as clinical toxicity becomes evident within this time frame.

The Clinical Value of the ECG in Noncardiac Conditions

The ECG is an indispensable tool in the ICU for the detection and diagnosis of heart disease. ECG abnormalities however can be present in a wide variety of noncardiac conditions, complicating the differential diagnosis with primary cardiac pathology. This overview discusses the ECG abnormalities and their pathophysiologic basis in the most frequently encountered noncardiac conditions, such as electrolyte abnormalities, pulmonary embolism, CNS diseases, esophageal disorders, hypothermia, and drug-related and other conditions. Knowledge of the characteristic ECG changes may provide early clues to the presence of these disorders, the prompt recognition of which can be life saving.

Electrocardiographic changes associated with beta-blocker toxicity

STUDY OBJECTIVE

We sought to characterize the ECG changes associated with symptomatic beta-blocker overdose.

METHODS

The study population consisted of a prospective cohort of patients reporting to 2 regional poison centers with beta-blocker overdose. Each patient received an ECG on presentation and a structured follow-up. The inclusion criteria for symptomatic overdose included heart rate of less than 60 beats/min or systolic blood pressure of less than 90 mm Hg; symptoms consistent with decreased end-organ perfusion; therapeutic intervention with cardioactive medication; and corroboration by 2 of the authors that this was a clear-cut case of symptomatic beta-blocker overdose with cardiovascular toxicity. Exclusion criteria included cardioactive coingestants, age younger than 6 years, and no available ECG.

RESULTS

Of 167 patients, 13 were determined to have symptomatic exposures. First-degree heart block (>200 ms) was the most common ECG finding (10/12) and also had the greatest likelihood ratio (5.31) when comparing those with symptomatic exposures with those with asymptomatic exposures. Comparing the asymptomatic with the symptomatic groups, the mean PR interval was 167 ms (95% confidence interval [CI] 162 to 171 ms) versus 216 ms (95% CI 193 to 238 ms), the mean QRS interval was 89 ms (95% CI 87 to 91 ms) versus 112 ms (95% CI 92 to 132 ms), the mean QTc interval was 422 ms (95% CI 417 to 428) versus 462 ms (95% CI 434 to 490 ms), and the mean heart rate was 72 beats/min (95% CI 69 to 74 beats/min) versus 66 beats/min (95% CI 59 to 73 beats/min). Two cases of symptomatic acebutolol exposure appeared unique by demonstrating disproportionate prolongation of the QTc interval, an RaVR height of 3 mm or greater, and associated ventricular tachydysrhythmia.

CONCLUSION

The majority of clinically significant beta-blocker intoxications demonstrate negative dromotropic effects on ECG. Several ECG differences in acebutolol intoxication might reflect unique pathophysiologic processes relative to other beta-blockers.

Serial electrocardiographic changes as a predictor of cardiovascular toxicity in acute tricyclic antidepressant overdose

Tricyclic antidepressant agents continue to be a leading cause of significant morbidity and mortality in reported poisonings involving pharmaceutical agents. Although the history and physical examination play an important role in the assessment of patients with tricyclic antidepressant overdose, the presence of anticholinergic features on examination cannot predict the severity of the overdose. Several clinical variables, in particular electrocardiographic (ECG) changes, have been proposed as a guide to determine the severity of the tricyclic antidepressant poisoning. The authors describe a patient with tricyclic antidepressant overdose who presented with altered mental status and whose serial ECG changes played a significant role in diagnosing and predicting the impending cardiovascular toxicity. The role of ECG changes in making the diagnosis and assessing the severity of the tricyclic antidepressant overdose is reviewed.

Serum levels and cardiovascular effects of tricyclic antidepressants and selective serotonin reuptake inhibitors in depressed patients

Tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) are used to treat depression. Whereas cardiovascular effects have occasionally been reported during controlled studies with SSRIs, TCA treatment poses a well-known problem in this respect. To investigate the putative correlation between antidepressant dose or serum levels and adverse effects, the authors devised a naturalistic study to evaluate the tricyclic antidepressants' and SSRIs' effect on the cardiovascular system. The authors also compared antidepressant serum levels to adverse effects. Inpatients treated with TCAs or SSRIs were included; an electrocardiogram (ECG) and a Schellong test were carried out on the day patients entered the hospital and during steady-state treatment with antidepressant drugs when blood was drawn for therapeutic drug monitoring. The patient population consisted of 114 acutely depressed patients; 81 patients were treated with TCAs and 33 with SSRIs. The TCAs comprised amitriptyline (n = 43), clomipramine (n = 11), doxepin (n = 19) and imipramine (n = 8); the SSRIs comprised fluvoxamine (n = 14) and paroxetine (n = 19). In TCA-treated patients, the authors observed the same type of abnormalities in conduction and orthostatic hypotension as had been observed earlier. The authors also observed cases of first-degree atrioventricular block, prolonged QTc interval, and orthostatic hypotension in SSRI-treated patients. Thus SSRIs also appear to affect the cardiovascular system, which might pose a problem for patients with preexisting conduction disease. The authors observed a strong correlation between the decrease in systolic pressure and antidepressant serum concentration (except for clomipramine and paroxetine), suggesting that antidepressant serum level is a better correlate than dose.

Antidepressants, old and new. A review of their adverse effects and toxicity in overdose

The newer antidepressants are as efficacious as the older agents in the treatment of depression. They have a side effect profile that is different from the older drugs and are generally better tolerated. Drug-drug interactions do exist with some of these agents and can usually be predicted from knowledge of their metabolism. When taken in overdose as the sole agents they are rarely fatal; seizures, nausea, vomiting, decreased level of consciousness, and tachycardia are common. In combination with other drugs, toxicity can be more severe. The serotonin syndrome can occur with many of these drugs, and the emergency physician must be vigilant in the evaluation of the overdose patient. CAs and older MAOIs are still in use and remain dangerous when taken in overdose. Patients asymptomatic after a period of observation in the ED usually can be discharged after psychiatric evaluation, when it is required.

Electrocardiographic assessment of antianxiety medication in dogs and correlation with serum drug concentration

OBJECTIVES

To determine effects of tricyclic antidepressants (TCA) on the ECG of dogs treated for behavioral conditions and to examine correlations between ECG findings and serum concentrations of these medications.

DESIGN

Repeated-measures study.

ANIMALS

39 client-owned dogs with behavioral problems.

PROCEDURE

Two groups of dogs with behavioral problems were evaluated. In group 1 (n = 20), ECG tracings were recorded before starting treatment with TCA and again after treatment for > or = 1 month. Dogs in group 2 were already on long-term maintenance amounts of antianxiety medication when ECG tracings were recorded and serum concentrations of medications were obtained.

RESULTS

Significant differences were not detected for dogs in group 1 between ECG values measured before and after TCA administration. The ECG values for dogs in group 2 did not differ significantly from the mean of group-1 dogs before receiving medication or from the reference range used at our facility. Duration of the P wave had a significant positive correlation with serum concentrations of clomipramine but significant negative correlation with serum concentrations of amitriptyline. The QT interval corrected for heart rate had a significant negative correlation with serum concentrations of amitriptyline.

CONCLUSIONS AND CLINICAL RELEVANCE

Amitriptyline and clomipramine administered at standard dosages apparently do not cause ECG abnormalities in healthy dogs with behavioral problems. These medications should be used cautiously in dogs with conduction abnormalities, and clinicians should periodically monitor ECG and use good clinical judgment to weigh risks and benefits of medications for the safety of each dog.

Fluoxetine versus tricyclic antidepressants: a prospective multicenter study of antidepressant drug overdoses. The Antidepressant Study Group

This study compares the clinical course of tricyclic antidepressant and fluoxetine overdose. The study was a prospective case series of 9 urban hospital systems. Consecutive sampling of overdose patients presenting to emergency departments provided the participants for the study. The therapy was determined by each institution. Clinical, laboratory, economic impact, and coroners' information was gathered. Of 622 patients, 482 were excluded because of significant coingestants or lack of laboratory confirmation, leaving 124 tricyclic antidepressant and 16 fluoxetine cases. Twenty-seven percent of tricyclic antidepressant patients were alert on arrival to the emergency department; only 12.9% remained alert. The following were significantly more frequent after tricyclic antidepressant overdose: agitation, tachycardia, QRS prolongation, terminal R-wave deviation, intubation, coma, and admission to the intensive care unit. The mean tricyclic plus metabolite level was 777.6 ng/mL (range = 20-5260 ng/ mL), and the mean fluoxetine plus metabolite level was 496.4 ng/mL (range = 120-1930 ng/mL). There were two tricyclic antidepressant deaths. Of 179 total drug-ingestion deaths from the coroners' records, 38 were from tricyclic antidepressants and none from fluoxetine. Thus, tricyclic antidepressant overdoses resulted in more toxicity and more frequent admissions to the intensive care unit than did fluoxetine overdoses.

Dibenzepin overdose causing pulmonary edema

OBJECTIVE

To report a case of pulmonary edema due to dibenzepin overdose.

CASE SUMMARY

A 39-year-old woman was hospitalized 24 hours after she ingested eight tablets of dibenzepin hydrochloride delayed-release 240 mg/tablet (approximately 35 mg/kg body weight). On admission the patient was confused, and physical examination revealed sinus tachycardia (HR 130 beats/min). Forty-five hours after ingestion of the dibenzepin she developed pulmonary edema and was treated with furosemide, morphine, and mechanical ventilation through an endotracheal tube for 48 hours. Repeated echocardiography revealed left ventricular dysfunction that resolved as the medical condition of the patient improved. Appropriate studies excluded pneumonia, pneumonitis, adult respiratory distress syndrome, myocardial infarction, and pulmonary emboli as contributing factors to this patient's condition.

DISCUSSION

Tricyclic antidepressant overdose is known to cause cardiopulmonary complications, including pulmonary edema. To the best of our knowledge, this is the first reported case of pulmonary edema as a result of dibenzepin overdose. The most probable mechanism for this complication is depression of the left ventricular function.

CONCLUSIONS

As with other tricyclic antidepressants, dibenzepin toxicity may cause pulmonary edema. Close patient monitoring is essential for at least 48-72 hours after the overdose.

Does a sodium-free buffer affect QRS width in experimental amitriptyline overdose?

STUDY OBJECTIVES

We carried out this study to determine the effects of pH alteration on QRS width with administration of tromethamine, a non-sodium-containing buffering agent, in experimental amitriptyline overdose.

DESIGN

Prospective, nonblinded trial.

PARTICIPANTS

Adult mongrel dogs.

INTERVENTIONS

Pentobarbital-anesthetized dogs were overdosed with amitriptyline 5 mg/kg followed by infusion at 1.0 mg/kg/minute until the QRS width doubled, then decreased to .5 mg/kg/minute until the end of the experiment. At two defined points of toxicity, the dose of tromethamine required to raise the pH to 7.50 +/- 4 was given. pH and QRS width at a speed of 100 mm/second were measured over a 30-minute period after each tromethamine dose. Data were analyzed with non-linear-regression analysis.

RESULTS

At toxicity 1 the mean pH was 7.32, with a QRS width of 11.6 mm. Two minutes after the tromethamine dose the pH rose to 7.51, with narrowing of the QRS width to 8.4 mm. At toxicity 2 the pH was 7.40, with QRS width of 10.6 mm. Two minutes after tromethamine, the pH rose to 7.49 and the QRS width decreased to 9.7 mm. Regression analysis showed a correlation between pH and QRS width; as pH increased, QRS width decreased (P = .0001).

CONCLUSION

Cardiac toxicity of amitriptyline overdose, as manifested by QRS widening, is reversible by pH changes alone.

Cyclic antidepressant toxicity in children and adolescents

We retrospectively evaluated the clinical and laboratory findings of all patients admitted to our facility during a 6.5-year period with a history of cyclic antidepressant ingestion (CAD). Outcome parameters [admission CAD concentration, arterial pH, and corrected QT (QTc) and QRS intervals] used in adult populations to predict morbidity after CAD ingestion were applied to our study population. During the study period, 45 patients (mean +/- SD age of 11.8 +/- 5.6 years) were admitted with CAD ingestion. Conduction delays were present in 17 patients, 9 of whom had QTc intervals greater than 0.43 seconds. Seven patients had generalized seizures; 7 required mechanical ventilation; 14 had Glasgow Coma Scores of 8 or lower on presentation; and one required pharmacologic support for hypotension. In our cohort, the mean admission serum CAD concentration was 461.5 +/- 477.4 ng/mL. Correlations were found between the arterial pH, the QRS interval, the QTc interval, and the admission CAD serum concentration. In an analysis of three subsets of patients (i.e., those with seizures, coma, and respiratory insufficiency), only patients who presented with seizures were found to have a significant prolongation in the QRS and QTc intervals. Pediatric patients who have ingested CADs and present with seizures would appear to be at increased risk for having conduction delays, cardiac dysrhythmias, and, presumably, attendant morbidity and mortality associated with an ingestion.

Magnesium potentiates imipramine toxicity in the isolated rat heart

STUDY OBJECTIVE

To study the effect of magnesium on cardiac function and hemodynamics during imipramine toxicity.

DESIGN

After stabilization, isolated, beating rat hearts were perfused with Krebs-Henseleit bicarbonate buffer (KHB) solution containing 2.0 mg/L imipramine (IMIP) and 2.4 mEq [Mg2+] until toxicity, defined as 25% widening of the ventricular depolarization duration (VDD). Experiments were performed at either constant coronary perfusion pressure or flow.

SETTING

Animal research laboratory of a large, urban hospital.

MEASUREMENTS

Heart rate, VDD, left ventricular pressure and +/- dP/dt, and coronary flow.

INTERVENTIONS

On onset of toxicity, KHB+IMIP was switched to either control (KHB+IMIP), magnesium (KHB+IMIP+4.0 or 6.0 mEq/L [Mg2+]), or hypertonic alkaline treatment (165 mEq/L [Na+], pH 7.55).

RESULTS

At a constant coronary perfusion pressure of 100 mm Hg, magnesium at 6.0 mEq produced significant decreases in heart rate, left ventricular pressure, +dP/dt, and increase in VDD versus control. With coronary flow held constant, magnesium reduced left ventricular pressure and +dP/dt but not heart rate or VDD. Incidences of electromechanical dissociation and asystole were higher with magnesium versus control. Hypertonic alkaline treatment tended to improve all parameters in constant pressure and constant flow experiments.

CONCLUSION

Magnesium potentiates IMIP-induced negative inotropic effects and cardiac conduction defects in isolated rat hearts.

Experimental amitriptyline poisoning: treatment of severe cardiovascular toxicity with cardiopulmonary bypass

STUDY OBJECTIVE

To compare cardiopulmonary bypass (CPB) with more conventional therapy in the treatment of severe amitriptyline poisoning.

DESIGN

Prospective, randomized, controlled, laboratory investigation.

INTERVENTIONS

Profound cardiovascular toxicity was induced in 20 anesthetized Yorkshire swine (72 +/- 8.3 kg) by amitriptyline infusion at 0.5 mg/kg/min. Ventilation was adjusted to keep arterial pH at 7.50 +/- 0.05 and the PCO2 at 35 mm Hg. The swine were randomized in a 1:1 ratio to one of two groups, CPB or control. Both groups received amitriptyline infusion until they experienced near-lethal toxicity, defined as a systolic blood pressure below 30 mm Hg for one minute. The control group was then given supportive treatment, including IV fluids, sodium bicarbonate, vasopressors, and standard pharmacologic (advanced cardiac life support) interventions. Control animals failing to respond to supportive measures after five minutes were given open-chest cardiac massage for 30 minutes or until the return of spontaneous circulation. The CPB group received only mechanical support by CPB for 90 to 120 minutes. No sodium bicarbonate, antiarrhythmics, or cardiotonic agents were provided to the CPB group during this resuscitation.

RESULTS

All 20 animals experienced cardiac conduction delays, dysrhythmias, and progressive hypotension within 30 minutes of receiving IV amitriptyline at 0.5 mg/kg/min. The ten swine receiving CPB as treatment for cardiovascular toxicity were able to completely correct the dysrhythmias, cardiac conduction abnormalities, and hypotension produced by the amitriptyline; however, only one of ten control animals could be resuscitated (P = .0001). Nine of ten swine treated with CPB were easily weaned off bypass without any pharmacologic intervention; however, one required norepinephrine to be weaned. All 11 resuscitated swine were able to be salvaged.

CONCLUSION

CPB improved survival in our swine model of severe amitriptyline poisoning.