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QT Interval Prolongation (qt + interval_prolongation)
Selected AbstractsQT Interval Prolongation and BeyondANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2006Jean-Philippe Couderc Ph.D., M.B.A. No abstract is available for this article. [source] Torsade de pointes in a patient with complex medical and psychiatric conditions receiving low-dose quetiapineACTA PSYCHIATRICA SCANDINAVICA, Issue 4 2005W. V. R. Vieweg Objective:, Describe potential cardiac complications of low-dose quetiapine and other atypical antipsychotic drugs. Method:, We present a case report of a 45-year-old Black woman with multiple medical and psychiatric problems taking low-dose quetiapine. Results:, Coincident with a generalized seizure, the patient developed ,ventricular fibrillation'. She was countershocked with restoration of normal sinus rhythm. The initial electrocardiogram showed QT interval prolongation. Shortly thereafter, classical torsade de pointes appeared, lasted 10 min, and resolved spontaneously. Hypomagnesemia was present. A cardiac electrophysiologist was concerned that the very slow shortening of the prolonged QTc interval after magnesium replacement implicated quetiapine as a risk factor for QTc interval prolongation and torsade de pointes. A psychosomatic medicine consultant asserted that the fragmented medical and psychiatric care almost certainly contributed to the patient's medical problems. We discuss other cases of QT interval prolongation by newer antipsychotic drugs and previous reports by our group concerning the association of psychotropic drugs, QT interval prolongation, and torsade de pointes. Conclusion:, Atypical antipsychotic drug administration, when accompanied by risk factors, may contribute to cardiac arrhythmias including torsade de pointes. [source] QT interval prolongation in association with impaired circadian variation of blood pressure and heart rate in adolescents with Type 1 diabetesDIABETIC MEDICINE, Issue 11 2007K. Karavanaki Abstract Aims, The aim of our study was to assess diurnal blood pressure (BP) and heart rate variability and their possible relationship to the duration of the QT interval in adolescents with Type 1 diabetes. Methods, In 48 normotensive, normoalbuminuric diabetic adolescents, with a mean (± sd) age of 17.3 (± 4.1) years and a mean (± sd) diabetes duration of 8.5 (± 3.3) years, 24-h ambulatory BP was recorded. In addition, 24-h heart rate (HR) monitoring was performed and QT and corrected QT (QTc) intervals were estimated as indices of autonomic function. The patients were divided into two groups according to the absence of a decrease (non-dippers) or the presence of a decrease (dippers) in nocturnal diastolic BP (DBP). Results, In comparison with the dippers, the non-dippers showed reduced mean 24-h HR (79.6 vs. 84.0 beats/min, P = 0.05) and reduced mean daytime HR (81.3 vs. 86.0 beats/min, P = 0.05). The QT interval was prolonged in the non-dippers (366.3 vs. 347.5 ms, P = 0.015), and end systolic (28.7 vs. 25.9 mm, P = 0.004) and end diastolic left ventricular diameters (47.8 vs. 45.5 mm, P = 0.037) were greater. In stepwise multiple regression, HR variables were the most important factors affecting DBP ratio or the duration of the QT interval. Conclusions, In conclusion, normotensive diabetic adolescents with impaired nocturnal BP reduction also have impaired autonomic function tests, in association with prolonged QT interval and increased left ventricular diameters. These findings suggest that diabetic adolescents who have the ,non-dipper' phenomenon may need close follow-up for the possible development of vascular complications, such as cardiac arrhythmias and left-ventricular hypertrophy. [source] Prevalence and clinical relevance of corrected QT interval prolongation during methadone and buprenorphine treatment: a mortality assessment studyADDICTION, Issue 6 2009Katinka Anchersen ABSTRACT Aims To determine the prevalence of corrected QT interval (QTc) prolongation among patients in opioid maintenance treatment (OMT) and to investigate mortality potentially attributable to QTc prolongation in the Norwegian OMT programme. Participants and setting Two hundred OMT patients in Oslo were recruited to the QTc assessment study between October 2006 and August 2007. The Norwegian register of all patients receiving OMT in Norway (January 1997,December 2003) and the national death certificate register were used to assess mortality. Mortality records were examined for the 90 deaths that had occurred among 2382 patients with 6450 total years in OMT. Design and measures The QTc interval was assessed by electrocardiography (ECG). All ECGs were examined by the same cardiologist, who was blind to patient history and medication. Mortality was calculated by cross-matching the OMT register and the national death certificate register: deaths that were possibly attributable to QTc prolongation were divided by the number of patient-years in OMT. Findings In the QTc assessment sample (n = 200), 173 patients (86.5%) received methadone and 27 (13.5%) received buprenorphine. In the methadone group, 4.6% (n = 8) had a QTc above 500 milliseconds; 15% (n = 26) had a QTc interval above 470 milliseconds; and 28.9% (n = 50) had a QTc above 450 milliseconds. All patients receiving buprenorphine (n = 27) had QTc results <450 milliseconds. A positive dose-dependent association was identified between QTc length and dose of methadone, and all patients with a QTc above 500 milliseconds were taking methadone doses of 120 mg or more. OMT patient mortality, where QTc prolongation could not be excluded as the cause of death, was 0.06/100 patient-years. Only one death among 3850 OMT initiations occurred within the first month of treatment. Conclusion Of the methadone patients, 4.6% had QTc intervals above 500 milliseconds. The maximum mortality attributable to QTc prolongation was low: 0.06 per 100 patient-years. [source] Iloperidone for schizophrenia: a review of the efficacy and safety profile for this newly commercialised second-generation antipsychoticINTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 8 2009L. Citrome Summary Objective:, The aim of the study was to describe the efficacy and safety of iloperidone for the treatment of schizophrenia. Data sources:, The pivotal registration trials were accessed by querying http://www.pubmed.gov, http://www.fda.gov and http://www.clinicaltrials.gov for the search term ,iloperidone'. Study selection:, Four published primary reports of phase III studies were identified as well as preclinical animal and receptor affinity studies that describe potential mechanisms of action and pharmacogenomic studies that identify potential genetic biomarkers for efficacy and tolerability. Product labelling provided additional data. Data extraction:, Descriptions of the principal results and calculation of number needed to treat (NNT) and number needed to harm (NNH) for relevant dichotomous outcomes were extracted from the study reports. Additional safety outcomes subject to NNH analysis were obtained from product labelling. Data synthesis:, Iloperidone is a second-generation antipsychotic agent indicated for the acute treatment of schizophrenia in adults. Iloperidone has been evaluated in several double-blind placebo-controlled clinical trials. The oral formulation has demonstrated efficacy in reducing the symptoms of acute schizophrenia at fixed daily doses ranging from 12 to 24 mg. Data reported for categorical definitions of response using the Positive and Negative Syndrome Scale were limited to one study and specifically to rates of achieving a , 20% decrease in the positive subscale from baseline; significantly more patients receiving iloperidone 24 mg/day (72%) than placebo (52%) met this criterion, yielding a NNT of five. Iloperidone should be titrated slowly to avoid orthostatic hypotension, potentially delaying the achievement of a therapeutic dose level. There appears to be a dose relationship for adverse events such as dizziness, somnolence and dry mouth; for example NNH vs. placebo for somnolence was 25 for iloperidone 10,16 mg/day and 10 for 20,24 mg/day. There is a possibility of a therapeutic dose response as well. Iloperidone is essentially free of extra-pyramidal side effects. Iloperidone is associated with weight gain comparable with risperidone. Long-term double-blind maintenance studies have demonstrated iloperidone's non-inferiority to haloperidol for relapse prevention. Product labelling includes a warning about the potential for QT interval prolongation. At present there are no efficacy studies available that are powered to directly compare iloperidone with other second-generation antipsychotics. The development of a depot formulation of iloperidone as well as efforts to identify genetic biomarkers for prediction of both efficacy and tolerability are in progress. Conclusions:, Aside from paliperidone, iloperidone is the first new second-generation antipsychotic to be commercialised in the USA since 2002. From the limited registration data, iloperidone appears to be relatively well tolerated once titrated to a therapeutic level and can be a useful option to consider. The development of a depot formulation and potential for genetic biomarkers may make this agent compelling. Further comparisons with other available agents among patients with schizophrenia in the ,real world' are needed. [source] The role of methadone in cancer pain treatment , a reviewINTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 7 2009W. Leppert Summary Background:, Methadone is an opioid analgesic of step 3 of the World Health Organization (WHO) analgesic ladder. Aim and Methods:, To outline pharmacodynamics, pharmacokinetics, drug interactions, equianalgesic dose ratio with other opioids, dosing rules, adverse effects and methadone clinical studies in patients with cancer pain. A review of relevant literature on methadone use in cancer pain was conducted. Results:, Methadone is used in opioid rotation and administered to patients with cancer pain not responsive to morphine or other strong opioids when intractable opioid adverse effects appear. Methadone is considered as the first strong opioid analgesic and in patients with renal impairment. Methadone possesses different pharmacodynamics and pharmacokinetics in comparison to other opioids. The advantages of methadone include multimode analgesic activity, high oral and rectal bioavailability, long lasting analgesia, lack of active metabolites, excretion mainly with faeces, low cost and a weak immunosuppressive effect. The disadvantages include long and changeable plasma half-life, high bound to serum proteins, metabolism through P450 system, numerous drug interactions, lack of clear equianalgesic dose ratio to other opioids, QT interval prolongation, local reactions when administered subcutaneously. Conclusions:, Methadone is an important opioid analgesic at step 3 of the WHO analgesic ladder. Future controlled studies may focus on establishment of methadone equianalgesic dose ratio with other opioids and its role as the first strong opioid in comparative studies with analgesia, adverse effects and quality of life taken into consideration. [source] Sotalol and a Broken HeartJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2010F.H.R.S., PETER L. FRIEDMAN M.D., Ph.D. Sotalol and a Broken Heart., An 82-year-old woman with persistent atrial fibrillation underwent successful electrical cardioversion and was begun on sotalol. After 3 days of in-hospital observation she had only mild lengthening of the QT interval. Two weeks later in clinic, the day after her husband's unexpected death, she was noted to have profound QT interval prolongation. Although she was asymptomatic and echocardiography did not disclose regional wall motion abnormalities consistent with takotsubo cardiomyopathy, she probably had a forme fruste of stress cardiomyopathy. Following emotional trauma, a period of heightened vigilance for ventricular proarrhythmia is probably warranted in women treated with antiarrhythmic drugs that lengthen repolarization. (J Cardiovasc Electrophysiol, Vol. 21, pp. 207-210, February 2010) [source] QT Interval Correction in Patients with CirrhosisJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2007ANDREA ZAMBRUNI M.D. Introduction: QT interval prolongation is a common electrophysiological abnormality in patients with cirrhosis. As QT interval varies with the heart rate, many QT correction formulas have been proposed, the Bazett's one being the most criticized because it overcorrects the QT interval and may be misleading. This study focused on the QT-RR relationship in patients with cirrhosis to derive a population-specific QT correction formula. Methods: One hundred cirrhotic patients of different etiology and severity and 53 healthy controls comparable for age and sex were enrolled. The QT-RR relationship was analyzed in patients by five regression analysis models to derive the population-specific QT-RR equation. The QTc was calculated and compared with those calculated by four common QT correction formulas (Bazett, Fridericia, Framingham, and Hodges). The correlation coefficient QTc-RR was calculated as a measure of the independence of QTc from the original RR interval. Results: In patients the QT-RR relationship was best described by the power equation "QT = 453.65 × RR1/3.02" (R2= 0.41), similar to the Fridericia's formula. Bazett's formula led to the longest QTc (P < 0.0001), which was still significantly influenced by the RR interval (R =,0.39; P < 0.0001), while the estimated equation led to a QTc value not influenced by RR (R =,0.014). Conclusion: Bazett's correction should be avoided in patients with cirrhosis because it still provides a rate-dependent QTc value and might be misleading, particularly when assessing the overall preoperative cardiac risk and the effect of drugs affecting the QT interval. In its place, our formula or that of Fridericia can be confidently employed. [source] Comparative Pharmacology of Guinea Pig Cardiac Myocyte and Cloned hERG (IKr) ChannelJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2004CHRISTINA DAVIE Ph.D. Introduction: This study used whole-cell, patch clamp techniques on isolated guinea pig ventricular myocytes and HEK293 cells expressing cloned human ether-a-go-go-related gene (hERG) to examine the action of drugs causing QT interval prolongation and torsades de pointes (TdP) in man. Similarities and important differences in drug actions on cardiac myocytes and cloned hERG IKr channels were established. Qualitative actions of the drugs on cardiac myocytes corresponded with results obtained from Purkinje fibers and measurement of QT interval prolongation in animal and human telemetry studies. Methods and Results: Adult guinea pig ventricular myocytes were isolated by enzymatic digestion. Cells were continuously perfused with Tyrode's solution at 33,35°C. Recordings were made using the whole-cell, patch clamp technique. Action potentials (APs) were elicited under current clamp. Voltage clamp was used to study the effect of drugs on IKr (rapidly activating delayed rectifier potassium current), INa (sodium current), and ICa (L-type calcium current). Dofetilide increased the myocyte action potential duration (APD) in a concentration-dependent manner, with a pIC50 of 7.3. Dofetilide 1 ,M elicited early afterdepolarizations (EADs) but had little affect on ICa or INa. E-4031 increased APD in a concentration-dependent manner, with a pIC50 of 7.2. In contrast, 10 ,M loratadine, desloratadine, and cetirizine had little effect on APD or IKr. Interestingly, cisapride displayed a biphasic effect on myocyte APD and inhibited ICa at 1 ,M. Even at this high concentration, cisapride did not elicit EADs. A number of AstraZeneca compounds were tested on cardiac myocytes, revealing a mixture of drug actions that were not observed in hERG currents in HEK293 cells. One compound, particularly AR-C0X, was a potent blocker of myocyte AP (pIC50 of 8.4). AR-C0X also elicited EADs in cardiac myocytes. The potencies of the same set of drugs on the cloned hERG channel also were assessed. The pIC50 values for dofetilide, E-4031, terfenadine, loratadine, desloratadine, and cetirizine were 6.8, 7.1, 7.3, 5.1, 5.2, and <4, respectively. Elevation of temperature from 22 to 35°C significantly enhanced the current kinetics and amplitudes of hERG currents and resulted in approximately fivefold increase in E-4031 potency. Conclusion: Our study demonstrates the advantages of cardiac myocytes over heterologously expressed hERG channels in predicting QT interval prolongation and TdP in man. The potencies of some drugs in cardiac myocytes were similar to hERG, but only myocytes were able to detect important changes in APD characteristics and display EADs predictive of arrhythmia development. We observed similar qualitative drug profiles in cardiac myocytes, dog Purkinje fibers, and animal and human telemetry studies. Therefore, isolated native cardiac myocytes are a better predictor of drug-induced QT prolongation and TdP than heterologously expressed hERG channels. Isolated cardiac myocytes, when used with high-throughput patch clamp instruments, may have an important role in screening potential cardiotoxic compounds in the early phase of drug discovery. This would significantly reduce the attrition rate of drugs entering preclinical and/or clinical development. The current kinetics and amplitudes of the cloned hERG channel were profoundly affected by temperature, significantly altering the potency of one drug (E-4031). This finding cautions against routine drug testing at room temperature compared to physiologic temperature when using the cloned hERG channel. [source] Heterogeneous Regional Endocardial Repolarization is Associated with Increased Risk for Ischemia-Dependent Ventricular Fibrillation after Myocardial InfarctionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2003Michael H. Swann M.SC. Introduction: The aim of this study was to investigate whether the characteristics of endocardial ventricular repolarization are associated with differential risk for sudden death. Prolonged surface QT interval is associated with increased arrhythmic risk after myocardial infarction (MI), but the underlying mechanism of QT prolongation and its relation to lethal arrhythmias are unclear. Methods and Results: Ventricular fibrillation (VF) risk was assessed in 12 dogs 1 month after anterior MI during an exercise test coupled with brief circumflex coronary occlusion. Susceptible dogs (n = 5) developed VF during the brief ischemic episode, whereas resistant dogs did not (n = 7). Surface QT interval was measured at rest. Endocardial electroanatomic catheter maps of left ventricular repolarization were obtained in four unique regions identified by echocardiography and compared between groups. Compared to resistant dogs, susceptible dogs were characterized by prolonged surface QT intervals (240 ± 10 msec vs 222 ± 7 msec, P = 0.04). In addition, they had lower baroreflex sensitivity (9.7 ± 1.5 msec/mmHg vs 28 ± 9.8 msec/mmHg, P < 0.01) and a tachycardic response to acute ischemia suggesting higher propensity for stronger sympathetic reflexes. Surface QT interval prolongation in susceptible dogs was due to a marked heterogeneity of endocardial left ventricular repolarization (239 ± 42 msec, basal anterior wall vs 197 ± 35, lateral wall; P < 0.001). Resistant animals had no regional differences in endocardial repolarization. Conclusion: Sympathetic activation following MI not only produces adverse structural remodeling but also contributes to adverse electrophysiologic remodeling resulting in heterogeneous ventricular repolarization and in a myocardial substrate conducive to lethal reentrant arrhythmias. (J Cardiovasc Electrophysiol, Vol. 14, pp. 873-879, August 2003) [source] The effects of droperidol and ondansetron on dispersion of myocardial repolarization in childrenPEDIATRIC ANESTHESIA, Issue 10 2010DISHA MEHTA BSc Summary Objectives:, To compare the effects of droperidol and ondansetron on electrocardiographic indices of myocardial repolarization in children. Aim:, To refine understanding of the torsadogenic risk to children exposed to anti-emetic prophylaxis in the perioperative period. Background:, QT interval prolongation is associated with torsades des pointes (TdP), but is a poor predictor of drug torsadogenicity. Susceptibility to TdP arises from increased transmural dispersion of repolarization (TDR) across the myocardial wall, rather than QT interval prolongation per se. TDR can be measured on the electrocardiogram as the time interval between the peak and end of the T wave (Tp-e). Tp-e may therefore provide a readily available, noninvasive assay of drug torsadogenicity. The perioperative period is one of high risk for TdP in children with or at risk of long QT syndromes. Droperidol and ondansetron are two drugs commonly administered perioperatively, for prophylaxis of nausea and vomiting, which can prolong the QT interval. This study investigated their effects on myocardial repolarization. Methods:, One hundred and eight ASA1-2 children undergoing elective day-case surgery were randomized to receive droperidol, ondansetron, both or neither. Pre- and post-administration 12-lead electrocardiogram (ECGs) were recorded. QT and Tp-e intervals were measured and compared within and between groups, for the primary endpoint of a 25 ms change in Tp-e. Results:, Eighty children completed the study. There were no demographic or baseline ECG differences between groups. QT intervals lengthened by 10,17 ms after allocated treatments, with no between-group differences. Values remained within normal limits for all groups. Tp-e intervals increased by 0,7 ms, with no between-group differences. There were no instances of dysrhythmia. Conclusions:, Droperidol and ondansetron, in therapeutic anti-emetic doses, produce equivalent, clinically insignificant QT prolongation and negligible Tp-e prolongation, suggesting that neither is torsadogenic in healthy children at these doses. 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