Life-threatening cardiac arrhythmias due to drug-induced QT prolongation

Tpeak-Tend Interval during Pregnancy and Postpartum

BACKGROUND

Pregnancy is a condition in which new cardiac arrhythmias can occur or prior undiagnosed arrhythmias may provide symptoms. The occurrence of severe ventricular arrhythmias and polymorphic ventricular tachycardia that may lead to fainting or sudden cardiac death is promoted by the prolongation of the QTc interval. The post-partum adaptation period is the most arrhythmogenic. TpTe (Tpeak-Tend interval) is a novel marker of arrhythmogenesis by many considered a more sensitive marker than QTc.

OBJECTIVE

The aim of our work was to determine the TpTe interval (Tpeak-Tend) in women in the first, second and third trimester of pregnancy and the post-partum period.

MATERIALS AND METHODS

The study group consisted of 128 women in pregnancy or postpartum and a control group of 32 non-pregnant women. A standard 12-lead ECG (electrocardiograph) recording with evaluation of the duration of TpTe and QTc was performed in all patients.

RESULTS

In comparison to the non-pregnant women, higher values of QTc and TpTe were observed starting in the first trimester with highest values observed in the postpartum period. Mean duration of TpTe interval during pregnancy (81.59 ± 5.92 ms) and in the whole study group (pregnancy + postpartum) (85.46 ± 6.45 ms) was significantly longer (p < 0.001) compared to the TpTe interval in the control group (74.06 ± 6.14 ms). During pregnancy and postpartum, the increase in the TpTe interval in comparison to the increase in the QTc parameter (31.10% vs. 4.18%) was significantly higher (p < 0.001).

CONCLUSIONS

The study showed an increase in the duration of the TpTe interval and QTc parameter during pregnancy and postpartum with the highest values in the postpartum period. TpTe interval increase was significantly higher compared to QTc increase during pregnancy and postpartum. Changes of TpTe interval were not associated with any clinical outcome or measure of arrythmia burden. Further studies are needed in order to see the clinical significance of these ECG findings, in particular for larger groups of patients with automatic measurement in correlation with echocardiography.

QT interval prolongation and the rate of malignant ventricular dysrhythmia and cardiac arrest in adult poisoned patients

INTRODUCTION

Prolongation of QTc interval, a common electrocardiographic (ECG) abnormality encountered in the toxicology patient, is reportedly associated with an increased risk of malignant ventricular dysrhythmias (MVD), such as ventricular tachycardia (VT, with and without a pulse), ventricular fibrillation (VF), and/or cardiac arrest. Quantifiable cardiac arrest risk in relation to specific QTc interval length is not known in this population.

METHODS

We conducted a retrospective, observational study to assess the rate of cardiac arrest and its association with degree of QTc prolongation in a cohort of patients requiring toxicology consultation.

RESULTS

550 patients were included in our analysis (average age 36 years and 49% male). Average QTc was 453 milliseconds (ms). Overall incidence of cardiac arrest in the study cohort was 1.1% with 6 reported cases; when considering patients with QTc > 500 ms, incidence was 1.7%. Two patients with cardiac arrest experienced ventricular dysrhythmia with decompensation prior to cardiac arrest; four patients developed sudden cardiac arrest.

CONCLUSIONS

The risk of malignant ventricular dysrhythmia, including cardiac arrest, is low in this poisoned patient population with an overall rate of 1.1%. Two-thirds of cardiac arrest cases occurred in patients with normal QTc intervals. When considering patients with prolonged QTc intervals, the rate of cardiac arrest remains very low at 0.8%. Considering QTc greater than 500 ms, the rate of cardiac arrest is 1.7%. Further prospective studies are required to quantify the risk of malignant ventricular dysrhythmias, including cardiac arrest, and its relation to the degree of QTc interval in poisoned patients.

Plasma Hyperosmolality Prolongs QTc Interval and Increases Risk for Atrial Fibrillation in Traumatic Brain Injury Patients

Introduction: Hyperosmotic therapy with mannitol is frequently used for treatment cerebral edema, and 320 mOsm/kg H₂O has been recommended as a high limit for therapeutic plasma osmolality. However, plasma hyperosmolality may impair cardiac function, increasing the risk of cardiac events. The aim of this study was to analyze the relation between changes in plasma osmolality and electrocardiographic variables and cardiac arrhythmia in patients treated for isolated traumatic brain injury (iTBI). Methods: Adult iTBI patients requiring mannitol infusion following cerebral edema, and with a Glasgow Coma Score below 8, were included. Plasma osmolality was measured with Osmometr 800 CLG. Spatial QRS-T angle (spQRS-T), corrected QT interval (QTc) and STJ segment were calculated from digital resting 12-lead ECGs and analyzed in relation to four levels of plasma osmolality: (A) <280 mOsm/kg H₂O; (B) 280–295 mOsm/kg H₂O; (C) 295–310 mOsm/kg H₂O; and (D) >310 mOsm/kg H₂O. All parameters were measured during five consecutive days of treatment. Results: 94 patients aged 18-64 were studied. Increased plasma osmolality correlated with prolonged QTc (p < 0.001), intensified disorders in STJ and increased the risk for cardiac arrhythmia. Moreover, plasma osmolality >313 mOms/kg H₂O significantly increased the risk of QTc prolongation >500 ms. Conclusion: In patients treated for iTBI, excessively increased plasma osmolality contributes to electrocardiographic disorders including prolonged QTc, while also correlating with increased risk for cardiac arrhythmias.

QTc interval prolongation in critically ill patients: Prevalence, risk factors and associated medications

PURPOSE

To investigate the prevalence and risk factors of acquired long QT syndrome (LQTS) on admission to a general Intensive Care Unit (ICU), and to assess the risk of LQTS associated with prescribed medications.

METHODS

Prospective observational, cross-sectional study approved by the Institutional Review Board. Between May 2014 and July 2016, 412 patients >18 years-old consecutively admitted to the ICU of a university hospital were included. LQTS was defined as a QT interval on the admission electrocardiogram corrected using Bazett's formula (QTc) >460 ms for men and >470 ms for women. All medications administered within 24 hours before admission were recorded. Logistic regression was used.

RESULTS

LQTS prevalence was 27.9%. In LQTS patients, 70.4% had ≥ 1 LQTS-inducing drug prescribed in the 24 hours prior to ICU admission versus 70.4% in non-LQTS patients (p = 0.99). Bradycardia and Charlson morbidity index score are independent risk factors for LQTS. Haloperidol (OR 4.416), amiodarone (OR 2.509) and furosemide (OR 1.895) were associated with LQTS, as well as another drug not yet described, namely clopidogrel (OR 2.241).

CONCLUSIONS

The LQTS is highly prevalent in critically ill patients, ICU patients are often admitted with LQTS-inducing medications, and patients with slow heart rate or with high Charlson comorbidity index should be evaluated for LQTS.

Change and dispersion of QT interval during treatment with quetiapine extended release versus aripiprazole in children and adolescents with first-episode psychosis: results from the TEA trial

OBJECTIVE

The aim of this study was to compare the effect of quetiapine extended release (ER) versus aripiprazole on corrected QT interval (QTc) and QT dispersion (QTd) in youths with first-episode psychosis.

METHODS

Youths 12-17 years were randomized to quetiapine ER (daily dose range = 50 to 800 mg) or aripiprazole (daily dose range = 2.5 to 30 mg) in a 12-week double-blinded trial and examined at weeks 0, 4, and 12. Primary outcome was QTc change using Hodges formula (QTcH); secondary outcomes included QTcH > 450 ms, QTcH > 500 ms, QTcH change > 60 ms, QTd, and heart rate (HR).

RESULTS

Among 113 randomized youths, follow-up ECG was available for 93 patients (82.3%) (age = 15.8 ± 1.3 years, males = 34.4%, schizophrenia = 67.7%). Quetiapine ER treatment (n = 47) was associated with a significant increase in QTcH of + 6.8 ± 20.2 ms (p = 0.025), while the change from baseline in patients receiving aripiprazole (n = 46) was non-significant (- 3.4 ± 18.9 ms, p = 0.225). One patient in the quetiapine ER group had a QTcH change of + 62.3 ms. Age, sex, smoking, body mass index, and concomitant medication were not significantly associated with QTcH change, but higher baseline potassium was correlated to higher QTcH change in the quetiapine ER group. The HR increased significantly with quetiapine ER (+ 11.0 ± 14.2 bpm, p < 0.001) but not with aripiprazole (- 0.8 ± 12.0 bpm, p = 0.643). QTd did not significantly change with quetiapine ER or aripiprazole.

CONCLUSION

QTcH and HR increased significantly with quetiapine ER, although changes were small and likely not clinically significant in otherwise healthy patients. QTcH and HR were unchanged with aripiprazole. No significant change in QTd was seen. ClinicalTrials.gov: NCT01119014, EudraCT: 2009-016715-38.

Clinical pharmacists' opportunities to reduce inappropriate prescription of QT-prolonging medications: calls to action

All biologically active agents carry the potential to lead to adverse reactions in certain individuals, including serious cardiac adverse reactions. Since 2005, there has been an international regulatory landscape governing the investigation of a new drug's propensity to lead to the polymorphic ventricular tachycardia Torsades de Pointes (Torsades), a rare but potentially fatal occurrence. When a regulatory agency considers it appropriate, warning information is placed in a medicine's patient information leaflet (label) concerning drug-induced QT interval prolongation, a phenomenon associated with Torsades. In busy hospital settings, however, prescribers, including cardiologists, make injudicious prescribing decisions that put patients at risk. The science of cardiac safety, including the clinical trials that generate the information about QT prolongation in patient information leaflets, is frequently not part of the curriculum at Schools of Pharmacy. Given that medication-induced cardiotoxicity is extremely serious, we advocate that schools integrate the science of cardiac safety into existing therapeutics/therapeutic medication monitoring courses. Given their expert knowledge of pharmacology, pharmacists working as part of a hospital's clinical team would then be even better placed to review prescribing decisions concerning medications that prolong the QT interval, and alert prescribers in cases where reassessing their decisions seems prudent. National pharmacy societies or other pertinent professional societies could create practice guidelines to support graduates once employed as clinical pharmacists. Clinical pharmacists are well placed to be influential arbiters of safer prescribing decisions. Cardiac safety education during their pharmacy training and practice guideline support from professional societies during their careers can optimize this role.