Tricyclic antidepressants directly depress human myocardial mechanical function independent of effects on the conduction system

In-depth mechanistic analysis including high-throughput RNA sequencing in the prediction of functional and structural cardiotoxicants using hiPSC cardiomyocytes

BACKGROUND

Cardiotoxicity remains one of the most reported adverse drug reactions that lead to drug attrition during pre-clinical and clinical drug development. Drug-induced cardiotoxicity may develop as a functional change in cardiac electrophysiology (acute alteration of the mechanical function of the myocardium) and/or as a structural change, resulting in loss of viability and morphological damage to cardiac tissue.

RESEARCH DESIGN AND METHODS

Non-clinical models with better predictive value need to be established to improve cardiac safety pharmacology. To this end, high-throughput RNA sequencing (ScreenSeq) was combined with high-content imaging (HCI) and Ca2+ transience (CaT) to analyze compound-treated human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).

RESULTS

Analysis of hiPSC-CMs treated with 33 cardiotoxicants and 9 non-cardiotoxicants of mixed therapeutic indications facilitated compound clustering by mechanism of action, scoring of pathway activities related to cardiomyocyte contractility, mitochondrial integrity, metabolic state, diverse stress responses and the prediction of cardiotoxicity risk. The combination of ScreenSeq, HCI and CaT provided a high cardiotoxicity prediction performance with 89% specificity, 91% sensitivity and 90% accuracy.

CONCLUSIONS

Overall, this study introduces mechanism-driven risk assessment approach combining structural, functional and molecular high-throughput methods for pre-clinical risk assessment of novel compounds.

Psychiatric conditions as predictors of rehospitalization among African American patients hospitalized with heart failure

INTRODUCTION

African Americans (AAs) have the highest risk of developing heart failure (HF) among all ethnicities in the United States and are associated with higher rates of readmissions and mortality. This study aims to determine the prevalence and relationship of common psychiatric conditions to outcomes of patients hospitalized with HF.

HYPOTHESIS

Psychiatric conditions lead to worse outcomes in HF patients.

METHODS

This single-center retrospective study enrolled 611 AA patients admitted to an urban teaching community hospital for HF from 2010 to 2013. Patient demographics, clinical variables, and history of psychiatric disorders were obtained. Cox proportional hazards regression was used to assess impact of psychiatric disorders on readmission rates and mortality.

RESULTS

The mean age was 66 ± 15 years; 53% were men. Median follow-up time from index admission for HF was 3.2 years. Ninety-seven patients had a psychiatric condition: 46 had depression, 11 had bipolar mood disorder (BMD), and 40 had schizophrenia. After adjustment of known risk factors and clinical metrics, our study showed that AA HF patients with a psychiatric illness were 3.84× more likely to be admitted within 30 days for HF, compared with those without (P < 0.001). Individually, adjusted Cox multivariable logistic regression analysis also showed that, for 30-day readmission, schizophrenia had a hazard ratio (HR) of 4.92 (P < 0.001); BMD, an HR of 3.44 (P = 0.02); and depression, an HR 3.15 (P = 0.001). No associations were found with mortality.

CONCLUSIONS

Psychiatric conditions of schizophrenia, BMD, and depression were significantly associated with a higher 30-day and overall readmission rate for HF among AA patients.

Case report: successful lipid resuscitation in multi-drug overdose with predominant tricyclic antidepressant toxidrome

We report a case of profound neurologic and cardiovascular manifestations of tricyclic antidepressant intoxication following self-poisoning with multiple pharmaceuticals including amitriptyline in excess of 43 mg/kg, in a 51-year-old male. Institution of mechanical ventilation, volume expansion, systemic alkalinisation (pH 7.51), and intermittent bolus metaraminol resulted in QRS narrowing but failed to resolve the developed shock. One 100-ml bolus of 20% lipid emulsion followed by a further 400 ml over 30 min was administered with restoration of haemodynamic stability, thereby curtailing the need for ongoing vasopressor medications. Assayed blood levels were consistent with the 'lipid sink' being a major effecter in the observed improvement.

Current and Emerging Detoxification Therapies for Critical Care

Toxicity resulting from prescription drugs such as tricyclic antidepressants and cardioactive steroids, as well as drugs of abuse and exposure to environmental chemicals, represents a major need for detoxification treatments. Particles and colloids, antibody fragments (Fab), and indirect treatment methods such as macroemulsions, are currently being developed or employed as detoxification therapies. Colloids, particles, and protein fragments typically mitigate toxicity by binding to the toxin and reducing its concentration in vital organs. Indirect methods such as macroemulsions and sodium bicarbonate act directly on the affected organs, rather than the toxin. In this review, key design parameters (i.e. binding affinity, biocompatibility, pharmacokinetics) are discussed for each type of detoxification treatment. In addition, some of the latest research in each area is reviewed.

Amitriptyline activates cardiac ryanodine channels and causes spontaneous sarcoplasmic reticulum calcium release

Patients taking amitriptyline (AMT) have an increased risk of sudden cardiac death, yet the mechanism for AMT's proarrhythmic effects remains incompletely understood. Here, we hypothesize that AMT activates cardiac ryanodine channels (RyR2), causing premature Ca(2+) release from the sarcoplasmic reticulum (SR), a mechanism identified by genetic studies as a cause of ventricular arrhythmias and sudden cardiac death. To test this hypothesis, we measured the effect of AMT on RyR2 channels from mice and sheep and on intact mouse cardiomyocytes loaded with the Ca(2+) fluorescent indicator Fura-2 acetoxymethyl ester. AMT induced trains of long channel openings (bursts) with 60 to 90% of normal conductance in RyR2 channels incorporated in lipid bilayers. The [AMT], voltage, and open probability (P(o)) dependencies of burst frequency and duration indicated that AMT binds primarily to open RyR2 channels. AMT also activated RyR2 channels isolated from transgenic mice lacking cardiac calsequestrin. Reducing RyR2 P(o) by increasing cytoplasmic [Mg(2+)] significantly inhibited the AMT effect on RyR2 channels. Consistent with the single RyR2 channel data, AMT increased the rate of spontaneous Ca(2+) releases and decreased the SR Ca(2+) content in intact cardiomyocytes. Intracellular [AMT] were approximately 5-fold higher than extracellular [AMT], explaining AMT's higher potency in cardiomyocytes at clinically relevant concentrations (0.5-3 muM) compared with its effect in lipid bilayers (5-10 muM). Increasing extracellular [Mg(2+)] attenuated the effect of AMT in intact myocytes. We conclude that the heretofore unrecognized activation of RyR2 channels and increased SR Ca(2+) leak may contribute to AMT's proarrhythmic and cardiotoxic effects, which may be counteracted by interventions that reduce RyR2 channel open probability.

Intralipid outperforms sodium bicarbonate in a rabbit model of clomipramine toxicity

STUDY OBJECTIVE

Previous investigators have demonstrated amelioration of lipid-soluble drug toxidromes with infusion of lipid emulsions. Clomipramine is a lipid-soluble tricyclic antidepressant with significant cardiovascular depressant activity in human overdose. We compare resuscitation with Intralipid versus sodium bicarbonate in a rabbit model of clomipramine toxicity.

METHODS

Thirty sedated and mechanically ventilated New Zealand White rabbits were infused with clomipramine at 320 mg/kg per hour. At target mean arterial pressure of 50% initial mean arterial pressure, animals were rescued with 0.9% NaCl 12 mL/kg, 8.4% sodium bicarbonate 3 mL/kg, or 20% Intralipid 12 mL/kg. Pulse rate, mean arterial pressure, and QRS duration were sampled at 2.5-minute intervals to 15 minutes. In the second phase of the experiment, 8 sedated and mechanically ventilated rabbits were infused with clomipramine at 240 mg/kg per hour to a mean arterial pressure of 25 mm Hg. Animals received either 2 mL/kg 8.4% sodium bicarbonate or 8 mL/kg 20% Intralipid as rescue therapy. External cardiac compression and intravenous adrenaline were administered in the event of cardiovascular collapse.

RESULTS

Mean difference in mean arterial pressure between Intralipid- and saline solution-treated groups was 21.1 mm Hg (95% confidence interval [CI] 13.5 to 28.7 mm Hg) and 19.5 mm Hg (95% CI 10.5 to 28.9 mm Hg) at 5 and 15 minutes, respectively. Mean difference in mean arterial pressure between Intralipid- and bicarbonate-treated groups was 19.4 mm Hg (95% CI 18.8 to 27.0 mm Hg) and 11.5 mm Hg (95% CI 2.5 to 20.5 mm Hg) at 5 and 15 minutes. The rate of change in mean arterial pressure was greatest in the Intralipid-treated group at 3 minutes (6.2 mm Hg/min [95% CI 3.8 to 8.6 mm Hg/min] Intralipid versus -0.25 mm Hg/min [95% CI -1.9 to 1.4 mm Hg/min] saline solution) and 5 minutes (4.4 mm Hg/min [95% CI 3.0 to 5.9 mm Hg/min] Intralipid versus 0.06 mm Hg/min [95% CI -0.9 to 1.1 mm Hg/min] saline solution). In the second phase of the experiment spontaneous circulation was maintained in all Intralipid-treated rabbits (n=4). All animals in the bicarbonate-treated group developed pulseless electrical activity and proved refractory to resuscitation at 10 minutes (n=4, P=.023).

CONCLUSION

In this rabbit model, Intralipid infusion resulted in more rapid and complete reversal of clomipramine-induced hypotension compared with sodium bicarbonate. Additionally, Intralipid infusion prevented cardiovascular collapse in a model of severe clomipramine toxicity.

Tricyclic antidepressant poisoning : cardiovascular toxicity

Tricyclic antidepressants remain a common cause of fatal drug poisoning as a result of their cardiovascular toxicity manifested by ECG abnormalities, arrhythmias and hypotension. Dosulepin and amitriptyline appear to be particularly toxic in overdose. The principal mechanism of toxicity is cardiac sodium channel blockade, which increases the duration of the cardiac action potential and refractory period and delays atrioventricular conduction. Electrocardiographic changes include prolongation of the PR, QRS and QT intervals, nonspecific ST segment and T wave changes, atrioventricular block, right axis deviation of the terminal 40 ms vector of the QRS complex in the frontal plane (T 40 ms axis) and the Brugada pattern (downsloping ST segment elevation in leads V1-V3 in association with right bundle branch block). Maximal changes in the QRS duration and the T 40 ms axis are usually present within 12 hours of ingestion but may take up to a week to resolve. Sinus tachycardia is the most common arrhythmia due to anticholinergic activity and inhibition of norepinephrine uptake by tricyclic antidepressants but bradyarrhythmias (due to atrioventricular block) and tachyarrhythmias (supraventricular and ventricular) may occur. Torsade de pointes occurs uncommonly. Hypotension results from a combination of reduced myocardial contractility and reduced systemic vascular resistance due to alpha-adrenergic blockade. Life-threatening arrhythmias and death due to tricyclic antidepressant poisoning usually occurs within 24 hours of ingestion. Rapid deterioration is common. Level of consciousness at presentation is the most sensitive clinical predictor of serious complications. Although a QRS duration >100 ms and a rightward T 40 ms axis appear to be better predictors of cardiovascular toxicity than the plasma tricyclic drug concentration, they have at best moderate sensitivity and specificity for predicting complications.

Association between depression and elevated C-reactive protein

OBJECTIVE

Depression has been related to a higher risk of developing coronary heart disease, but the mechanism that accounts for this association is unclear. Because atherosclerosis is an inflammatory process, depression could increase the risk of coronary heart disease by inducing or promoting inflammation. The objective of the present study was to investigate the association between history of major depressive episode and presence of low-grade systemic inflammation as measured by serum C-reactive protein (CRP).

METHODS

We analyzed data from the Third National Health and Nutrition Examination Survey, a representative sample of the US population from 1988 to 1994. Participants included a total of 6149 individuals aged 17 to 39 years who were free of cardiovascular diseases and chronic inflammatory conditions. The main predictor variable of interest was lifetime history of a major depressive episode as assessed by means of the Diagnostic Interview Schedule. The main outcome variable was the presence or absence of an elevated CRP level (> or =22 mg/dl).

RESULTS

Among men, history of a major depressive episode was associated with elevated CRP, particularly for recent episodes (up to 6 months before assessment). In multivariate analyses, men with a history of major depressive episode had 2.77 times higher odds of elevated CRP compared with never-depressed men (95% confidence interval, 1.43-5.26). The adjusted odds ratio was 3.81, 3.98, 1.51, and 1.52 for men who had their last major depressive episode less than 1 month before, 1 to 6 months before, 7 to 12 months before, and more than 12 months before assessment, respectively (p for trend =.004). In women, a comparable association between depression and CRP was quite weak and not significant.

CONCLUSIONS

A recent history of major depressive episode is strongly associated with elevated CRP in men aged 17 to 39. In this group, low-grade systemic inflammation could represent a mechanism linking depression to cardiovascular risk.