Proarrhythmic potential of antimicrobial agents

Costs are a major driver of antibacterial drug prescriptions in Germany: market analysis from 1985 to 2022

In recent years, several threatening developments regarding antibacterial drugs, such as rising bacterial resistance and delivery bottlenecks, have occurred. Since antibacterial drugs are crucial for modern medicine, understanding events and influencing factors relevant for long-term developments is essential. Therefore, we analyzed the number of prescriptions and costs, defined daily dose (DDD) and DDD costs of antibacterial drugs in Germany, based on the Arzneiverordnungsreport (AVR, Drug description report) between 1985 and 2022. Based on prescription rates in 2022, we selected the TOP15 and TOP5. For a more in-depth analysis, we analyzed data from the wissenschaftliches Institut der AOK (WidO, scientific institute of the AOK). The number of prescriptions increased between 1985 and 2013, but since 2014, there has been a declining trend with a noticeable COVID-related dip. Over the years, a shift in drug classes occurred. Once very popular drugs like penicillins and tetracyclines are no longer as important. Conversely, aminopenicillins and cephalosporins have become more relevant. Particularly, the TOP5 drugs have seen an increasing proportion. DDD costs have decreased in most substance classes over time. There is a strong association between decreasing costs and rising prescriptions. Falling costs have a stronger immediate impact on prescriptions that rising costs. When costs are very low, drugs might be prescribed excessively. Supply bottlenecks can also result. The main prescribers are mainly in primary care. Their share of prescription has changed little over the years, but is decreasing regarding total consumption. In comparison to other European countries, Germany ranks in the lower third regarding prescriptions. In most countries, the COVID pandemic has led to a reduced prescription of antibacterial drugs. In conclusion, we provided a comprehensive overview of the antibacterial drug market in Germany over the past four decades and identified costs as a major driver of antibacterial drug prescriptions. Increased costs may reduce uncritical prescription of antibacterial drugs, development of bacterial resistance, supply shortages and occurrence of adverse effects.

Torsade de pointe due to QT prolongation following erythromycin administration in a preterm infant

BACKGROUND

Neonatal sepsis is a major cause of morbidity and mortality in preterm infants. Chorioamnionitis is an important risk factor for the development of sepsis, therefore neonates born to mothers developing signs of amnionitis need to be treated with antibiotics immediately after birth. Ureaplasma spp can be a causative agent of vaginal or intra amniotic infection needing antibiotic treatment. Macrolides are frequently used to treat maternal intrauterine infection, but antibiotic treatment of the neonate should be consciously chosen with consideration of potential side effects. Indeed, macrolides are great purveyors of heart rhythm disorders.

CASE PRESENTATION

We describe the case of a 29 weeks preterm infant born to a mother with Ureaplasma spp infection. The baby was treated with erythromycin immediately after birth. During the second day of life, the baby presented some episodes of tachyarrhythmia with premature ventricular beats (PVBs) that were followed by a non-sustained ventricular tachycardia as high as 270 bpm leading to a cardiac arrest. After resuscitation, tachycardia resolved but the rhythm was characterised by numerous PVBs and an electrocardiogram (ECG) diagnosed a Long QT Syndrome (LQTS). Erythromycin was discontinued, and the rhythm normalised a few days after withdrawal.

CONCLUSIONS

Erythromycin should be administered in neonates only if no other choice is available, as although generally well tolerated, its administration can be associated with QTc interval prolongation. When no other option is available, paediatricians should be aware to perform cardiac monitoring or at least serial ECGs before and during erythromycin administration.

The proarrhythmic effects of hypothermia in atria isolated from 5-HT4-receptor-overexpressing mice

We investigated whether hypothermia would be arrhythmogenic in mice that overexpress the human 5-HT₄ receptor only in their cardiac myocytes (5-HT₄-TG). Contractile studies were performed in isolated, electrically driven (1 Hz) left and spontaneously beating right atrial preparations of 5-HT₄-TG and littermate wild-type control mice (WT). Hypothermia (23 °C) decreased the force of contraction in the mouse right and left atrial preparations. Moreover, the concentration-dependent positive inotropic effects of 5-HT were blunted but still shifted to lower 5-HT concentrations in the left 5-HT₄-TG atria in hypothermia compared to normothermia (37 °C). Furthermore, hypothermia increased the incidence of right atrial arrhythmias in 5-HT₄-TG more than in WT mice. In contrast, at 37 °C, lowering the potassium concentration from 5.2 to 2.0 mM also induced arrhythmias in the right atrium, but with a similar incidence in WT and 5-HT₄-TG mice. In contrast, 10 μM d,l-sotalol and 300 μM erythromycin did not induce arrhythmias. Hypothermia was accompanied by the increased expression of heat shock protein 70 (HSP70) in WT but not in 5-HT₄-TG mice. We concluded that without the stimulation of 5-HT₄-receptors by exogenous agonists, a simple temperature reduction can increase arrhythmias in 5-HT₄-TG mice. It is tempting to speculate that in human patients, 5-HT₄ receptors might contribute to potentially deadly hypothermia-induced arrhythmias.

Review - Treatment of Helicobacter pylori infection 2020

This review summarizes important studies regarding Helicobacter pylori therapy published from April 2019 to April 2020. The main themes that emerge involve studies assessing antibiotic resistance, and there is also growing momentum behind the utility of vonoprazan as an alternative to proton pump inhibitor (PPI) therapy and also bismuth-based regimens as a first-line regimen. Antibiotic resistance is rising wherever it is being assessed, and clarithromycin resistance in particular has reached a point where it may no longer be a viable therapy without previous testing in many regions of the world. The evidence for the efficacy of a bismuth-based quadruple therapy as a first-line therapy is now very clearly established, and there is substantial evidence that it is the best performing first-line therapy. The utility of vonoprazan as an alternative to PPI therapy, especially in resistant and difficult-to-treat groups, has also been considered in great detail this year, and it may offer an opportunity in the near future to reduce the problem of antibiotic resistance.

Risk of Adverse Drug Events Following the Virtual Addition of COVID-19 Repurposed Drugs to Drug Regimens of Frail Older Adults with Polypharmacy

Determination of the risk-benefit ratio associated with the use of novel coronavirus disease 2019 (COVID-19) repurposed drugs in older adults with polypharmacy is mandatory. Our objective was to develop and validate a strategy to assess risk for adverse drug events (ADE) associated with COVID-19 repurposed drugs using hydroxychloroquine (HCQ) and chloroquine (CQ), alone or in combination with azithromycin (AZ), and the combination lopinavir/ritonavir (LPV/r). These medications were virtually added, one at a time, to drug regimens of 12,383 participants of the Program of All-Inclusive Care for the Elderly. The MedWise Risk Score (MRSTM) was determined from 198,323 drug claims. Results demonstrated that the addition of each repurposed drug caused a rightward shift in the frequency distribution of MRSTM values (p < 0.05); the increase was due to an increase in the drug-induced Long QT Syndrome (LQTS) or CYP450 drug interaction burden risk scores. Increases in LQTS risk observed with HCQ + AZ and CQ + AZ were of the same magnitude as those estimated when terfenadine or terfenadine + AZ, used as positive controls for drug-induced LQTS, were added to drug regimens. The simulation-based strategy performed offers a way to assess risk of ADE for drugs to be used in people with underlying medical comorbidities and polypharmacy at risk of COVID-19 infection without exposing them to these drugs.

Calculated initial parenteral treatment of bacterial infections: Pharmacokinetics and pharmacodynamics

This is the third chapter of the guideline "Calculated initial parenteral treatment of bacterial infections in adults - update 2018" in the 2nd updated version. The German guideline by the Paul-Ehrlich-Gesellschaft für Chemotherapie e.V. (PEG) has been translated to address an international audience. The chapter features the pharmacokinetic and pharmacodynamics properties of the most frequently used antiinfective agents.

Electrocardiographic Effects of a Supratherapeutic Dose of WCK 2349, a Benzoquinolizine Fluoroquinolone

The purpose of this study was to measure the electrocardiographic (ECG) effects of WCK 2349 (the L‐alanine ester prodrug of levonadifloxacin) at a supratherapeutic oral dose of 2,600 mg. A total of 48 healthy volunteers were randomized to treatment with placebo, WCK 2349, or oral moxifloxacin, 400 mg, in a crossover‐designed thorough QT study. A supratherapeutic mean maximum levonadifloxacin concentration (C_max) of 43.3 μg/mL was achieved at 3.1 hours. A therapeutic dose of 1,000 mg b.i.d. in a previous study in patients resulted in a C_max of 17.8 μg/mL. WCK 2349 exerted no significant effect on baseline‐ and placebo‐corrected QTcF (QT interval corrected for heart rate (HR) by the Fridericia formula), QRS, or PR interval. HR was transiently accelerated by a maximum of 14.4 (95% confidence interval, 11.80–16.92) beats per minute (bpm) at 3 hours. Concentration–effect modeling predicted a mean increase of 8.0 bpm at C_max at the standard therapeutic dose. A therapeutic dose of 1,000 mg b.i.d. of WCK 2349 is not expected to cause clinically significant ECG effects, except for a possible transient increase in HR, which seems to be clinically insignificant.

Follow-Up (Measurement) of Corrected QT Interval in Adult Patients before and after Lung Transplantation

Background

Prolongation of the corrected QT (QTc) interval is well known for many drugs, some of which are an integral part of the therapeutic regimen after lung transplantation (LTX). Therefore, we investigated the QTc interval after LTX in the present study.

Patients and Methods

The medical records of patients after LTX were studied for demographic data, indication of LTX, medication, and baseline and follow-up ECGs. The QT interval was corrected for the patient's heart rate using the different formulae of Bazett, Fridericia, Hodges, and Framingham.

Results

Fifty-nine patients were included. The mean age ± SD was 55.6 ± 7.8 years (median 58 years). After LTX, QTc intervals showed no (relevant) changes during follow-up, even though all patients were treated with drugs (in combination) known to bear a risk of prolonged QTc interval and cortisone. The longest QTc intervals were obtained using Bazett's formula.

Conclusion

The QTc interval did not increase under immunosuppressive medication after LTX in our cohort of patients. We speculate that the concurrent use of cortisone may shorten the QT(c) intervals or cancel out drug-induced prolongation of the QTc interval.

QTc prolongation during ciprofloxacin and fluconazole combination therapy: prevalence and associated risk factors

AIM(S)

Ciprofloxacin and fluconazole combination therapy is frequently used as prophylaxis for, and treatment of, infections in patients with haematological malignancies. However, both drugs are known to prolong the heart rate-corrected QT (QTc) interval, which is a serious risk factor for torsade de pointes (TdP). Therefore, the aim of the current study was to assess the prevalence of QTc prolongation during ciprofloxacin and fluconazole use. The secondary objective was to determine associated risk factors of QTc prolongation in these patients.

METHODS

A prospective observational study was performed in patients admitted to the Erasmus University Medical Centre and treated with ciprofloxacin and fluconazole. A 12-lead electrocardiogram (ECG) was recorded at the estimated time to peak concentration (T_max ) for the last added drug. The main outcome was the proportion of patients with QTc prolongation during treatment. Data on the following potential risk factors were collected: patient characteristics, serum electrolyte levels, dosage of ciprofloxacin and fluconazole, renal and liver function and concomitant use of other QTc-prolonging drugs and cytochrome P450 3A4 inhibitors.

RESULTS

A total of 170 patients were included, of whom 149 (87.6%) were treated for haematological malignancies. The prevalence of QTc prolongation was 4.7%. No risk factors were found to be associated with QTc prolongation. The QTc interval increased by 10.7 ms [95% confidence interval (CI) 7.2, 14.1 ms] during ciprofloxacin and fluconazole combination therapy.

CONCLUSION

The prevalence of QTc prolongation in patients using ciprofloxacin and fluconazole is low compared with the prevalence in the general population, which varies from 5% to 11%. In addition, no risk factors were found. Given the low prevalence, routine ECG monitoring in patients on this therapy should be reconsidered.

Potential drug-drug interactions in paediatric outpatient prescriptions in Nigeria and implications for the future

BACKGROUND

Information regarding the incidence of drug-drug interactions (DDIs) and adverse drug events (ADEs) among paediatric patients in Nigeria is limited.

METHODS

Prospective clinical audit among paediatric outpatients in four general hospitals in Nigeria over a 3-month period. Details of ADEs documented in case files was extracted.

RESULTS

Among 1233 eligible patients, 208 (16.9%) received prescriptions with at least one potential DDI. Seven drug classes were implicated with antimalarial combination therapies predominating. Exposure mostly to a single potential DDI, commonly involved promethazine, artemether/lumefantrine, ciprofloxacin and artemether/lumefantrine. Exposure mostly to major and serious, and moderate and clinically significant, potential DDIs. Overall exposure similar across all age groups and across genders. A significant association was seen between severity of potential DDIs and age. Only 48 (23.1%) of these patients presented at follow-up clinics with only 15 reporting ADEs.

CONCLUSION

There was exposure to potential DDIs in this population. However, potential DDIs were associated with only a few reported ADEs.

Illuminating drug action by network integration of disease genes: a case study of myocardial infarction

Drug discovery has produced many successful therapeutic agents; however, most of these drugs were developed without a deep understanding of the system-wide mechanisms of action responsible for their indications. Gene-disease associations produced by molecular and genetic studies of complex diseases provide great opportunities for a system-level understanding of drug activity. In this study, we focused on acute myocardial infarction (MI) and conducted an integrative network analysis to illuminate drug actions. We integrated MI drugs, MI drug interactors, drug targets, and MI disease genes into the human interactome and showed that MI drug targets are significantly proximate to MI disease proteins. We then constructed a bipartite network of MI-related drug targets and MI disease proteins and derived 12 drug-target-disease (DTD) modules. We assessed the biological relevance of these modules and demonstrated the benefits of incorporating disease genes. The results indicate that DTD modules provide insights into the mechanisms of action of MI drugs and the cardiovascular (side) effects of non-MI drugs.

Evaluation of macrolides for possible use against multidrug-resistant Mycobacterium tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) is a major global health problem. The loss of susceptibility to an increasing number of drugs behoves us to consider the evaluation of non-traditional anti-tuberculosis drugs.

Clarithromycin, a macrolide antibiotic, is defined as a group 5 anti-tuberculosis drug by the World Health Organization; however, its role or efficacy in the treatment of MDR-TB is unclear. A systematic review of the literature was conducted to summarise the evidence for the activity of macrolides against MDR-TB, by evaluating in vitro, in vivo and clinical studies. PubMed and Embase were searched for English language articles up to May 2014.

Even though high minimum inhibitory concentration values are usually found, suggesting low activity against Mycobacterium tuberculosis, the potential benefits of macrolides are their accumulation in the relevant compartments and cells in the lungs, their immunomodulatory effects and their synergistic activity with other anti-TB drugs.

A future perspective may be use of more potent macrolide analogues to enhance the activity of the treatment regimen.

Risks of cardiac arrhythmia and mortality among patients using new-generation macrolides, fluoroquinolones, and β-lactam/β-lactamase inhibitors: a Taiwanese nationwide study

BACKGROUND

Previous studies have demonstrated increased cardiovascular mortality related to azithromycin and levofloxacin. Risks associated with alternative drugs in the same class, including clarithromycin and moxifloxacin, were unknown. We used the Taiwan National Health Insurance Database to perform a nationwide, population-based study comparing the risks of ventricular arrhythmia and cardiovascular death among patients using these antibiotics.

METHODS

Between January 2001 and November 2011, a total of 10 684 100 patients were prescribed oral azithromycin, clarithromycin, moxifloxacin, levofloxacin, ciprofloxacin, or amoxicillin-clavulanate at outpatient visits. A logistic regression model adjusted for propensity score was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for adverse cardiac outcomes occurring within 7 days after the initiation of antibiotic treatment.

RESULTS

Compared with amoxicillin-clavulanate treatment, the use of azithromycin and moxifloxacin was associated with significant increases in the risks of ventricular arrhythmia and cardiovascular death. The adjusted ORs for ventricular arrhythmia were 4.32 (95% CI, 2.95-6.33) for azithromycin, 3.30 (95% CI, 2.07-5.25) for moxifloxacin, and 1.41 (95% CI, .91-2.18) for levofloxacin. For cardiovascular death, the adjusted ORs for azithromycin, moxifloxacin, and levofloxacin were 2.62 (95% CI, 1.69-4.06), 2.31 (95% CI, 1.39-3.84), and 1.77 (95% CI, 1.22-2.59), respectively. No association was noted between clarithromycin or ciprofloxacin and adverse cardiac outcomes.

CONCLUSIONS

Healthcare professionals should consider the small but significant increased risk of ventricular arrhythmia and cardiovascular death when prescribing azithromycin and moxifloxacin. Additional research is needed to determine whether the increased risk of mortality is caused by the drugs or related to the severity of infection or the pathogens themselves.

Acquired long QT syndrome: frequency, onset, and risk factors in intensive care patients

BACKGROUND

Acquired long QT syndrome is a reversible condition that can lead to torsades de pointes and sudden cardiac death.

OBJECTIVE

To determine the frequency, onset, frequency of medications, and risk factors for the syndrome in intensive care patients.

METHODS

In a retrospective chart review of 88 subjects, hourly corrected QT intervals calculated by using the Bazett formula were collected. Acquired long QT syndrome was defined as a corrected QT of 500 milliseconds or longer or an increase in corrected QT of 60 milliseconds or greater from baseline level. Risk factors and medications administered were collected from patients' medical records.

RESULTS

The syndrome occurred in 46 patients (52%); mean time of onset was 7.4 hours (SD, 9.4) from time of admission. Among the 88 patients, 52 (59%) received a known QTc-prolonging medication. Among the 46 with the syndrome, 23 (50%) received a known QT-prolonging medication. No other risk factor studied was significantly predictive of the syndrome.

CONCLUSIONS

Acquired long QT syndrome occurs in patients not treated with a known QT-prolonging medication, indicating the importance of frequent QT monitoring of all intensive care patients.

Azithromycin: more lethal than chloramphenicol?

Azithromycin is commonly used in sexual health and respiratory medicine, often when the diagnosis is presumptive. A recent article by Ray et al. reported that 1 out of 20 000 courses of low-dose azithromycin was associated with (sudden) cardiovascular death (including 1 out of 4000 courses in high-risk cardiovascular patients), ascribing these deaths to azithromycin itself. Here, we critique the actual study and examine conflicting data from randomised control trials, animal studies and observational data.

[Molecular and genetic background of sudden cardiac death]

Despite recent findings on the functional, structural and genetic background of sudden cardiac death, the incidence is still relatively high in the entire population. A thorough knowledge on susceptibility, as well as pathophysiology behind the development of malignant arrhythmias will help us to identify individuals at risk and prevent sudden cardiac death. This article presents a review of the current literature on the role of altered intracellular Ca2+ handling, acute myocardial ischaemia, cardiac autonomic innervation, renin-angiotensin-aldosterone system, monogenic and complex heritability in the pathogenesis of sudden cardiac death.

Effect of combined fluoroquinolone and azole use on QT prolongation in hematology patients

QTc prolongation is a risk factor for development of torsades de pointes (TdP). Combination therapy with fluoroquinolones and azoles is used in patients with hematologic malignancies for prophylaxis and treatment of infection. Both drug classes are implicated as risk factors for QTc prolongation. The cumulative effect on and incidence of QTc prolongation for this combination have not been previously described. A retrospective chart review was performed with hospitalized inpatients from 1 September 2008 to 31 January 2010 comparing QTc interval data from electrocardiogram (ECG) assessment at baseline and after the initiation of combination therapy. Ninety-four patients were eligible for inclusion. The majority, 88 patients (93.6%), received quinolone therapy with levofloxacin. Fifty-three patients (56.4%) received voriconazole; 40 (42.6%) received fluconazole. The overall mean QTc change from baseline was 6.1 (95% confidence interval [CI], 0.2 to 11.9) ms. Twenty-one (22.3%) of the studied patients had clinically significant changes in the QTc while receiving combination fluoroquinolone-azole therapy. Statistically significant risk factors for clinically significant changes in QTc were hypokalemia (P = 0.03) and a left-ventricular ejection fraction of <55% (P = 0.02). Low magnesium (P = 0.11), exposure to 2 or more drugs with the potential to prolong the QTc interval (P = 0.17), and female sex (P = 0.21) trended toward significance. Combination therapy with fluoroquinolone and azole antifungals is associated with increased QTc from baseline in hospitalized patients with hematologic malignancies. One in five patients had a clinically significant change in the QTc, warranting close monitoring and risk factor modification to prevent the possibility of further QTc prolongation and risk of TdP.

Pregnancy outcome after gestational exposure to erythromycin - a population-based register study from Norway

AIMS

Erythromycin is a macrolide antibiotic indicated for respiratory tract infections, genital chlamydia and skin infections. It has recently been suggested that erythromycin use in the first trimester of pregnancy can increase the risk of congenital cardiovascular malformations. This study aimed to determine whether erythromycin exposure in the first trimester is associated with cardiovascular or other malformations.

METHODS

We studied 180 120 women in Norway who were pregnant during 2004-2007. Data on all live births stillbirths and induced abortions after 12 gestational weeks from The Medical Birth Registry of Norway (MBRN) were linked to information from the Norwegian prescription database (NorPD). We compared the pregnancy outcomes of women who had taken erythromycin (n= 1786, 1.0%), penicillin V (n= 4921, 2.7%) or amoxicillin (n= 1599, 0.9%) in their first trimester with outcomes of women who had not taken any systemic antibiotics (n= 163 653, 90.9%) during this period.

RESULTS

The risk of cardiovascular malformations was not significantly different with or without exposure to erythromycin in the first trimester (adjusted OR = 1.2 [95% CI 0.8, 1.8]) or in the most vulnerable period of heart formation (adjusted OR = 1.6 [95% CI 0.9-3.0]). Sub-analyses showed that the risk for any specific malformations was not increased with erythromycin, macrolides, penicillin V or amoxicillin compared with no antibiotic use in first trimester.

CONCLUSIONS

This large, population-based register study did not find that exposure to erythromycin or macrolides in the first trimester of pregnancy was associated with fetal cardiovascular or other malformations. These results suggest that the risk of erythromycin use during early pregnancy, if any, is low.

Azithromycin and the risk of cardiovascular death

BACKGROUND

Although several macrolide antibiotics are proarrhythmic and associated with an increased risk of sudden cardiac death, azithromycin is thought to have minimal cardiotoxicity. However, published reports of arrhythmias suggest that azithromycin may increase the risk of cardiovascular death.

METHODS

We studied a Tennessee Medicaid cohort designed to detect an increased risk of death related to short-term cardiac effects of medication, excluding patients with serious noncardiovascular illness and person-time during and shortly after hospitalization. The cohort included patients who took azithromycin (347,795 prescriptions), propensity-score-matched persons who took no antibiotics (1,391,180 control periods), and patients who took amoxicillin (1,348,672 prescriptions), ciprofloxacin (264,626 prescriptions), or levofloxacin (193,906 prescriptions).

RESULTS

During 5 days of therapy, patients taking azithromycin, as compared with those who took no antibiotics, had an increased risk of cardiovascular death (hazard ratio, 2.88; 95% confidence interval [CI], 1.79 to 4.63; P<0.001) and death from any cause (hazard ratio, 1.85; 95% CI, 1.25 to 2.75; P=0.002). Patients who took amoxicillin had no increase in the risk of death during this period. Relative to amoxicillin, azithromycin was associated with an increased risk of cardiovascular death (hazard ratio, 2.49; 95% CI, 1.38 to 4.50; P=0.002) and death from any cause (hazard ratio, 2.02; 95% CI, 1.24 to 3.30; P=0.005), with an estimated 47 additional cardiovascular deaths per 1 million courses; patients in the highest decile of risk for cardiovascular disease had an estimated 245 additional cardiovascular deaths per 1 million courses. The risk of cardiovascular death was significantly greater with azithromycin than with ciprofloxacin but did not differ significantly from that with levofloxacin.

CONCLUSIONS

During 5 days of azithromycin therapy, there was a small absolute increase in cardiovascular deaths, which was most pronounced among patients with a high baseline risk of cardiovascular disease. (Funded by the National Heart, Lung, and Blood Institute and the Agency for Healthcare Quality and Research Centers for Education and Research on Therapeutics.).

Acquired long QT interval: a case series of multifactorial QT prolongation

BACKGROUND

Acquired long QT (LQT) interval is thought to be a consequence of drug therapy and electrolyte disturbances.

HYPOTHESIS

We characterize the potential effects of polypharmacy in a case series of acquired LQT and torsades de pointes (TdP) in order to determine whether multiple risk factors play a role in the development of LQT.

METHODS

The case series consisted of 11 patients presenting to 4 tertiary care hospitals with LQT and ≥ 2 risk factors for developing LQT. Clinical characteristics, medications, electrolyte disturbances, and course in hospital were analyzed.

RESULTS

Mean age was 49.1 ± 5.8 years. Eight patients were female. Four had hypertension, 1 had a history of dilated cardiomyopathy, and 1 patient demonstrated complete atrioventricular block. Average QTc interval at presentation was 633.8 ± 29.2 ms. Nine patients developed TdP. In 3, LQT was not initially detected and amiodarone was administered, followed by development of TdP. Patients were taking an average of 2.8 ± 0.3 QT-prolonging medications-an antidepressant in 6 cases and a diuretic in 8 cases. All patients had an electrolyte abnormality; 8 patients presented with severe hypokalemia (<3.0 mmol/L). Average serum potassium and magnesium were 2.82 ± 0.10 mmol/L and 0.75 ± 0.03 mmol/L, respectively. There were no deaths.

CONCLUSIONS

This case series highlights the risks of polypharmacy in the development of LQT and TdP. It illustrates the importance of early detection of LQT in patients with multiple risk factors in ensuring appropriate treatment.