Methadone Blockade of Cardiac Inward Rectifier K+ Current Augments Membrane Instability and Amplifies U Waves on Surface ECGs: A Translational Study

Opioids-Induced Long QT Syndrome: A Challenge to Cardiac Health

The challenge posed by opioid overdose has become a significant concern for health systems due to the complexities associated with drug prohibition, widespread clinical use, and potential abuse. In response, healthcare professionals have primarily concentrated on mitigating the hallucinogenic and respiratory depressant consequences of opioid overdose to minimize associated risks. However, it is crucial to acknowledge that most opioids possess the capacity to prolong the QT interval, particularly in cases of overdose, thereby potentially resulting in severe ventricular arrhythmias and even sudden death if timely intervention is not implemented. Consequently, alongside addressing the typical adverse effects of opioids, it is imperative to consider their cardiotoxicity. To enhance comprehension of the correlation between opioids and arrhythmias, identify potential targets for prompt intervention, and mitigate the hazards associated with clinical utilization, an exploration of the interaction between drugs and ion channels, as well as their underlying mechanisms, becomes indispensable. This review primarily concentrates on elucidating the impact of opioid drugs on diverse ion channels, investigating recent advancements in this domain, and attaining a deeper understanding of the mechanisms underlying the prolongation of the QT interval by opioid drugs, along with potential interventions.

Sleep-Disordered Breathing Destabilizes Ventricular Repolarization

Rationale

Sleep-disordered breathing (SDB) increases the risk of cardiac arrhythmias and sudden cardiac death.

Objectives

To characterize the associations between SDB, intermittent hypoxemia, and the beat-to-beat QT variability index (QTVI), a measure of ventricular repolarization lability associated with a higher risk for cardiac arrhythmias, sudden cardiac death, and mortality.

Methods

Three distinct cohorts were used for the current study. The first cohort, used for cross-sectional analysis, was a matched sample of 122 participants with and without severe SDB. The second cohort, used for longitudinal analysis, consisted of a matched sample of 52 participants with and without incident SDB. The cross-sectional and longitudinal cohorts were selected from the Sleep Heart Health Study participants. The third cohort comprised 19 healthy adults exposed to acute intermittent hypoxia and ambient air on two separate days. Electrocardiographic measures were calculated from one-lead electrocardiograms.

Results

Compared to those without SDB, participants with severe SDB had greater QTVI (-1.19 in participants with severe SDB vs. -1.43 in participants without SDB, P = 0.027), heart rate (68.34 vs. 64.92 beats/minute; P = 0.028), and hypoxemia burden during sleep as assessed by the total sleep time with oxygen saturation less than 90% (TST90; 11.39% vs. 1.32%, P < 0.001). TST90, but not the frequency of arousals, was a predictor of QTVI. QTVI during sleep was predictive of all-cause mortality. With incident SDB, mean QTVI increased from -1.23 to -0.86 over 5 years (P = 0.017). Finally, exposing healthy adults to acute intermittent hypoxia for four hours progressively increased QTVI (from -1.85 at baseline to -1.64 after four hours of intermittent hypoxia; P = 0.016).

Conclusions

Prevalent and incident SDB are associated with ventricular repolarization instability, which predisposes to ventricular arrhythmias and sudden cardiac death. Intermittent hypoxemia destabilizes ventricular repolarization and may contribute to increased mortality in SDB.

Comparison of the effects of propofol and alfaxalone on the electrocardiogram of dogs, with particular reference to QT interval

Cardiac electrical activity is often altered by administration of anesthetic drugs. While the effects of propofol in this regard have previously been described in dogs, to date, there are no reports of the effect of alfaxalone. This study investigated the impact of both propofol and alfaxalone on the ECG of 60 dogs, after premedication with acepromazine and methadone. Heart rate increased significantly in both groups. The PR and QRS intervals were significantly increased following propofol while with alfaxalone the QRS duration was significantly increased and ST segment depression was observed. The QT and JT interval were significantly shorter following induction with alfaxalone, but, when corrected (c) for heart rate, QTc and JTc in both groups were significantly greater following induction. When comparing the magnitude of change between groups, the change in RR interval was greater in the alfaxalone group. The change in both QT and JT intervals were significantly greater following alfaxalone, but when QTc and JTc intervals were compared, there were no significant differences between the two drugs. The similarly increased QTc produced by both drugs may suggest comparable proarrhythmic effects.

Bistable spiral wave dynamics in electrically excitable media

We show that a positive feedback loop between sodium current inactivation and wave-front ramp-up speed causes a saddle-node bifurcation to result in bistable planar and spiral waves in electrically excitable media, in which both slow and fast waves are triggered by different stimulation protocols. Moreover, the two types of spiral wave conduction may interact to give rise to more complex spiral wave dynamics. The transitions between different spiral wave behaviors via saddle-node bifurcation can be a candidate mechanism for transitions widely seen in cardiac arrhythmias and neural diseases.

Cardiac and mortality outcome differences between methadone, buprenorphine and naltrexone prescriptions in patients with an opioid use disorder

IMPORTANCE

More than 109,000 Americans died of drug overdose in 2022, with 81,231 overdose deaths involving opioids. Methadone, buprenorphine and naltrexone are the most widely used medications for opioid use disorders (MOUD) and the most effective intervention for preventing overdose deaths. However, there is a concern that methadone results in long QT syndrome, which increases the risk for fatal cardiac arrythmias. Currently few studies have systematically evaluated both the short-term and long-term differences in cardiac and mortality outcomes between MOUD.

OBJECTIVES

To compare the risks of cardiac arrythmias, long QT syndrome and overall mortality between patients with opioid use disorders (OUD) who were prescribed methadone, buprenorphine or naltrexone.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study based on a multicenter and nationwide database of electronic health records (EHRs) in the United States. The study population was comprised of 144,141 patients who had medical encounters for OUD in 2016-2022, were prescribed MOUD within 1 month following a medical encounter for OUD diagnosis and had no diagnosis of cardiac arrythmias or long QT syndrome before any MOUD prescription. The study population was divided into three cohorts: (1) Methadone cohort (n = 40,938)-who were only prescribed methadone. (2) Buprenorphine cohort (n = 80,055)-who were only prescribed buprenorphine. (3) Naltrexone cohort (n = 5,738)-who were only prescribed naltrexone.

EXPOSURES

methadone, buprenorphine, or naltrexone.

MAIN OUTCOMES AND MEASURES

Cardiac arrythmias, long QT syndrome, and death. Hazard ratio (HR) and 95% confidence interval (CI) of outcomes at six different follow-up time frames (1-month, 3-month, 6-month, 1-year, 3-year, and 5-year) by comparing propensity-score matched cohorts using Kaplan-Meier survival analysis.

RESULTS

Patients with OUD who were prescribed methadone had significantly higher risks of cardiac arrhythmias, long QT syndrome and death compared with propensity-score matched patients with OUD who were prescribed buprenorphine or naltrexone. For the 1-month follow-up, the overall risk for cardiac arrythmias was 1.03% in the Methadone cohort, higher than the 0.87% in the matched Buprenorphine cohort (HR: 1.20, 95% CI: 1.04-1.39); The overall risk for long QT syndrome was 0.35% in the Methadone cohort, higher than the 0.15% in the matched Buprenorphine cohort (HR: 2.40, 95% CI: 1.75-3.28); The overall mortality was 0.59% in the Methadone cohort, higher than the 0.41% in the matched Buprenorphine cohort (HR: 1.48, 95% CI: 1.21-1.81). The increased risk persisted for 5 years: cardiac arrhythmias (HR: 1.31, 95% CI: 1.23-1.38), long QT syndrome (HR: 3.14, 95% CI: 2.76-3.58), death (HR: 1.50, 95% CI: 1.41-1.59).

CONCLUSIONS AND RELEVANCE

Methadone was associated with a significantly higher risk for cardiac and mortality outcomes than buprenorphine and naltrexone. These findings are relevant to the development of guidelines for medication selection when initiating MOUD treatment and inform future medication development for OUD that minimizes risks while maximizing benefits.