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PubMed2001

Qtc interval as a guide to select those patients with congestive heart failure and reduced left ventricular systolic function who will benefit from antiarrhythmic treatment with dofetilide.

BACKGROUND: A prolonged QTc interval is considered a contraindication for class III antiarrhythmic drugs, but the influence of a normal or a slightly increased baseline QTc interval on the risk or benefit of treatment with a class III antiarrhythmic drug is not sufficiently clarified. METHODS AND RESULTS: This prospectively defined substudy included 703 patients enrolled in the Danish Investigations of Arrhythmia and Mortality on Dofetilide-Congestive Heart Failure (DIAMOND-CHF) study. Patients included had moderate to severe CHF and reduced left ventricular systolic function. Baseline QTc interval was measured before randomization to either dofetilide, a new class III antiarrhythmic drug, or placebo. During a median follow-up of 18 months (minimum 1 year), 285 patients (41%) died. Baseline QTc interval had no prognostic value on survival in placebo-treated patients. In dofetilide-treated patients, a baseline QTc interval <429 ms was associated with a significant risk reduction (risk ratio 0.4, 95% CI 0.3 to 0.8). With increasing QTc interval, the risk increased gradually, and for QTc interval >479 ms, risk ratio was 1.3 (0.8 to 1.9). CONCLUSIONS: A baseline QTc interval within normal limits is associated with a marked reduction of mortality in patients with CHF and left ventricular systolic dysfunction treated with dofetilide. This is a potentially important indication of which patients with CHF might benefit from prophylactic treatment with an antiarrhythmic drug.

Aged↗

PubMed2002

QTc interval lengthening is related to CYP2D6 hydroxylation capacity and plasma concentration of thioridazine in patients.

Thioridazine cardiotoxicity has been associated with a prolonged heart-rate corrected QT (QTc) interval. However, no systematic studies have been performed on patients at therapeutic doses. The present study aimed to evaluate the influence of dose and plasma concentration of thioridazine and CYP2D6 enzyme status on the QTc interval in psychiatric patients. Sixty-five Spanish European psychiatric patients receiving thioridazine antipsychotic monotherapy were studied. The plasma levels of thioridazine and its metabolites were determined by high-performance liquid chromatography. All patients were phenotyped for CYP2D6 activity with debrisoquine during treatment. Thirty-five patients (54%) had a QTc interval over 420 ms. The lengthening of QTc interval was correlated with plasma concentration (p < 0.05) and daily dose (p < 0.05) of thioridazine. CYP2D6 enzyme hydroxylation capacity, evaluated by debrisoquine metabolic ratio (MR) (p < 0.05) and thioridazine/mesoridazine ratio (p < 0.05), was also correlated with QTc intervals. The present study shows the relationship between QTc interval lengthening among psychiatric patients treated at therapeutical doses with the dose and the plasma concentration of thioridazine. Since debrisoquine MR has been shown to be correlated with the QTc intervals, CYP2D6 enzyme hydroxylation capacity might be relevant in determining the risk for QTc interval lengthening. Patients with impaired CYP2D6 enzyme activity due to enzyme inhibition by thioridazine might be more prone to increased risk of sudden death due to torsade de pointes type cardiac dysrhythmia.

Adrenergic Agents↗

PubMed2001

Impaired fasting glucose, diabetes mellitus, and cardiovascular disease risk factors are associated with prolonged QTc duration. Results from the Third National Health and Nutrition Examination Survey.

BACKGROUND: Impaired glucose tolerance and diabetes mellitus have been associated with a prolonged QT interval among select populations. However, these associations remain unclear among the general population. METHODS: We examined these relationships using data from 5833 adults aged 40-90 years from NHANES III (1988-1994). Univariate differences in cardiovascular disease (CVD) risk factors were examined across tertiles of heart rate corrected QT (QTc). The association between glucose intolerance, CVD risk factors and a prolonged QTc (> or = 0.440 s) was also assessed with logistic regression adjusting for age, race, gender, education, and heart rate. RESULTS: Prolonged QTc was observed among 22.0% of persons with normal glucose tolerance (NGT), 29.9% of those with impaired fasting glucose (IFG), and among 42.2% of persons with diabetes. Hypertension, serum cholesterol, obesity, heart rate, and fasting C-peptide and serum insulin levels were associated with prolonged QTc (all: P < or = 0.05). After multivariate adjustment, persons with IFG were 1.2 times (95% CI=0.7-2.0) as likely and persons with diabetes 1.6 times (95% CI=1.1-2.3) as likely to have a prolonged QTc as persons with NGT. In addition, persons with diabetes and two or more additional CVD risk factors were 2.3 times (95% CI=1.3-4.0) as likely to have a prolonged QTc as persons with NGT and no CVD risk factors after multivariate adjustment. CONCLUSION: Diabetes was associated with an increased likelihood of prolonged QTc independent of age, race, gender, education, and heart rate. In addition, persons with diabetes and multiple CVD risk factors were more likely to have a prolonged QTc than those with NGT and no additional risk factors, suggesting that these persons may be at increased risk for cardiac arrhythmia and sudden death.

Blood Glucose↗

PubMed2001

Cisapride associated with QTc prolongation in very low birth weight preterm infants.

OBJECTIVE: No systematic study has been performed to evaluate the effect of cisapride on the QT interval in premature infants. Cisapride, which has recently been withdrawn by the Food and Drug Administration and is no longer an approved therapy, was commonly used for preterm infant care to improve the advance of enteral feedings and to reduce reflux and associated apnea. Our aim was to evaluate the effect of recommended doses of cisapride on the QT interval in this population. STUDY DESIGN: Prospective blinded evaluation of electrocardiogram for QT, JT, QTc, and JTc measurements in 25 preterm infants before and after cisapride administration. RESULTS: Twelve of 25 infants (48%) developed repolarization abnormalities with cisapride administration: 32% of the infants (8/25) studied had QTc prolongation (>/=0.450 seconds), whereas 10/25 had JTc prolongation (>/=0.360 seconds). Preterm infants <32 weeks significantly prolonged their QTc interval from 0.41 +/- 0.02 to 0.44 +/- 0.02. The QTc and/or JTc was prolonged in 54% of infants receiving 0.1 mg/kg/dose and 42% receiving 0.2 mg/kg/dose. CONCLUSIONS: The QTc and JTc interval significantly prolonged in preterm infants <32 weeks on the recommended dose of cisapride therapy. A QTc >/=0.450 seconds developed in 32% of infants treated with cisapride, whereas the JTc prolonged in 40%. A significant percentage of infants (54%) developed prolonged QTc intervals at a dose of 0.1 mg/kg/dose. From these data we conclude that there is a higher risk of prolongation of the QTc interval and risk of arrhythmias with greater prematurity.

Arrhythmias, Cardiac↗

PubMedDate not supplied

Prognostic implication of hypocalcemia and QTc interval in malaria.

Hundred confirmed cases of malaria were included in the present study to determine the clinical and prognostic implications of hypocalcemia and corrected QT interval (QTc) prolongation in malaria. Peripheral blood smear examination was done to determine the parasite species and the parasite load. Serum calcium level and QTc measurements in electrocardiogram were done for each patient. Fifty patients were of P. falciparum malaria (38 complicated and 12 uncomplicated), 40 of vivax malaria and 10 patients were having mixed (P. falciparum and P. vivax) infection. Hypocalcemia was found in 26 cases in which QTc was prolonged. Ten patients who had convulsions, all of them were having QTc prolongation and eight had hypocalcemia. A total number of eight patients had muscle spasm, of which six had QTc prolongation and four had hypocalcemia. There were 34 cases of cerebral malaria, of which 18 had hypocalcemia as well as QTc prolongation, 12 of them developed renal failure and 14 had high parasitaemia. Four patients died who had hypocalcemia and QTc prolongation due to hepatorenal syndrome. The mean parasite load, QTc interval and serum calcium were 2.69 +/- 1.0, 0.468 +/- 0.055 sec and 8.16 +/- 0.86 mg/dl respectively in complicated falciparum malaria; 1.6 +/- 0.55, 0.442 +/- 0.043 sec and 8.72 +/- 0.97 mg/dl in complicated mixed (Pf + Pv) infection. 1.33 +/- 0.52, 0.435 +/- 0.035 sec and 9.77 +/- 1.34 mg/dl in uncomplicated falciparum malaria and 1.35 +/- 0.58, 0.403 +/- 0.019 sec and 9.68 +/- 0.99 mg/dl in vivax malaria. The difference was significant between complicated falciparum and mixed (Pf + Pv) infection when compared to uncomplicated falciparum and vivax malaria (p < 0.05).

Adolescent↗

PubMed2004

Predictive factors for QTc prolongation in schizophrenic patients taking antipsychotics.

BACKGROUND AND PURPOSE: The rate-corrected electrocardiographic QT (QTc) interval may significantly increase in schizophrenic patients taking antipsychotics. QTc prolongation is a risk factor for development of arrhythmia. The objective of this study was to assess the predictors of QTc prolongation in schizophrenic patients taking antipsychotic medication. METHODS: Electrocardiograms were obtained from 138 controls and 412 schizophrenic inpatients taking antipsychotics. QTc prolongation was defined as a mean value of 2 standard deviations above the controls. Predictors were analyzed with a logistic regression model. RESULTS: Based on data obtained from controls, QTc prolongation was defined as a QTc greater than 421 ms. Logistic regression analysis showed that significant predictors for QTc prolongation were: female gender (odds ratio, 3.355 [95% CI, 1.767-6.371]); increased age (1.040 [1.011-1.069]); and increased doses of some antipsychotics, including clozapine (1.006 [1.003-1.008]), chlorpromazine (1.003 [1.002-1.005]), thioridazine (1.007 [1.003-1.011]), and sulpiride (1.001 [1.001-1.002]). CONCLUSIONS: Predictors of the QTc prolongation in schizophrenic patients taking antipsychotic medications were female gender, old age, and treatment with clozapine, chlorpromazine, thiroridazine, or sulpiride.

Antipsychotic Agents↗

PubMed1996

[Prolonged QTc intervals in Parkinson's disease--relation to sudden death and autonomic dysfunction].

Sudden death has been reported in Parkinson's disease (PD), but the cause of death has not been fully clarified. A prolonged QT interval on the electrocardiogram (ECG) of patients without cardiac dysfunction is an independent risk factor for sudden death regardless of etiology. QT prolongation is believed to be related to cardiac autonomic dysfunction. We suspected that QTc intervals, as well as QT intervals, might be related to the clinical characteristics of PD and to the function of the autonomic nervous system in PD and also postulated a relationship between QTc prolongation and sudden death in PD. We investigated the QTc intervals on the ECGs of 48 PD patients (20 males 28 females) aged 64.5 +/- 9.4 years and 44 controls aged 60.0 +/- 8.2 years, and excluded patients with heart disease. QTc intervals were determined by using ECG-8210, ECAPS12 (Nihon-Kohden). The autonomic nervous system was evaluated by measuring CVR-R and performing orthostatic tests. Since the autonomic nervous system is considered to play an important role in the mechanism of diurnal blood pressure variation (DBPV), we assessed DBPV in 19 PD patients by determining blood pressure automatically every 30 minutes for 24 hours with an ambulatory blood pressure monitor (90202, Space Lab). QTc intervals were significantly longer in the PD patients (412 +/- 26 msec) than in the controls (401 +/- 14 msec) (p < 0.02, t-test). QTc prolongation was significantly correlated with severity according to Hoehn and Yahr stage (r = 0.509, p < 0.001), orthostatic hypotension, and decreased CVR-R ratio but not with duration of PD or treatment. The incidence of QTc prolongation was higher in the PD patients with non-dipper type DBPV than in those with the dipper type. Two of the PD patients died suddenly. Their QTc intervals a year before their death were 451 msec and 470 msec, respectively, suggesting that cardiac dysautonomia may have been involved in the cause of their death. These findings suggest that cardiac autonomic dysfunction is related to the severity of PD, and that it may predispose such patients to cardiac disorders including sudden cardiac death.

Adult↗

PubMed1997

Prolongation of the QTc interval during alcohol withdrawal syndrome.

BACKGROUND: Cardiac arrhythmias might explain cases of sudden death in alcoholics during ethanol abstinence. AIM OF STUDY: To evaluate QT interval (and its outcome) in patients with alcohol withdrawal syndrome. PATIENTS AND METHODS: Sixty-two patients (52 male and 10 female, mean age 43.7 years, range 18-71 years), admitted to the hospital as a result of alcohol abstinence syndrome (tremulousness in 7 cases, agitation in 12 cases, delirium tremens in 11 cases, and seizures in 32) were studied. The QT interval was measured on 12 lead ECGs performed on admission in all cases. QTc was obtained using Bazett's formula. In 27 patients a second ECG was performed during hospital stay. Results. Mean QTc interval on admission was 439 +/- 32 ms (range 350-525 ms); 29 patients (46.8%) showed a prolonged (> 440 ms) QTc interval. No significant differences were observed between patients with normal and high QTc values as regards to age, sex, type of withdrawal syndrome, duration of abstinence, liver function tests, serum electrolytes or blood cell counts. In cases where two ECG recordings could be evaluated (n = 27), the mean QTc interval was significantly shorter in the latter than in the former (417 +/- 26 ms versus 447 +/- 30 ms, respectively, p < 0.001). Eight patients found to have prolonged QTc on admission had a second ECG performed on them after complete recovery from withdrawal symptoms. In all these cases the QTc interval eventually became normal. CONCLUSION: The QTc interval is frequently prolonged during alcohol withdrawal syndrome and tends to become normal over time, along with remission of abstinence symptoms.

Adult↗

PubMed1980

QTc intervals in acute myocardial infarction: first-year prognostic implications.

Corrected QT (QTc) intervals were measured retrospectively in 160 consecutive survivors of acute myocardial infarction under 66 years of age. Calculations were made the first 2 d in the coronary care unit (CCU), the first post-CCU day, at discharge, and at 1-3, 6, and 12 months after discharge. All patients were in sinus rhythm and without bundle branch block at discharge from the hospital. Sixteen patients died during the first follow-up year. Twenty patients suffered a reinfarction, five of whom died. The highest QTc values were registered in the CCU and the lowest at the 1-year control. Patients with subendocardial infarcts had longer QTc intervals than those with transmural infarcts, especially during the acute phase. Patients with inferior infarcts had shorter QTc intervals during the CCU period. Those who reinfarcted or died a cardiac death (particularly when sudden) during the follow-up year had longer QTc intervals during the post-CCU phase. A multivariate analysis of risk factors revealed that the QTc interval at discharge was of significant independent value for predicting major cardiac events after discharge from the hospital. It is concluded that repeated measurements of QTc may be of value when assessing prognosis after acute myocardial infarction.

Acute Disease↗

PubMed1997

QTc interval (cardiac repolarization): lengthening after meals.

Weight reduction, either by dietary or surgical means, is associated with prolongation of the heart rate corrected QT interval (QTc = QT/R-R0.5) and, on occasion, sudden death. Screening subjects with obesity before weight loss for prolonged QTc intervals is an accepted practice, although at present, there are no guidelines for whether subjects should be fasting before electrocardiogram (EKG) evaluation. The aim of this study was to test the hypothesis that EKG QTc interval duration is independent of meal ingestion. The hypothesis was tested in 11 healthy subjects who ingested a 500-kcal formula meal. A small decrease in absolute QT interval and a steady decline in R-R interval were observed for up to 60 minutes after formula ingestion. The QTc interval increased above baseline at 15 minutes (p < 0.007) after meal, a change that persisted for the 1-hour postmeal observation period. Spectral analysis of EKG R-R intervals (low-/high-frequency amplitude ratio) indicated a change in cardiac autonomic flow after meal ingestion. The QTc interval did not lengthen and R-R low-/high-frequency amplitude ratio remained unchanged in eight subjects evaluated in a similar manner but in whom isovolumic amounts of water replaced the meal. These observations suggest that (1) cardiac repolarization changes with fasting and feeding, (2) the QTc interval is influenced by meal intake, and (3) the autonomic nervous system may play a role in meal-related QTc changes. These findings have implications for the evaluation of patients with obesity before starting and during weight loss treatment.

Adult↗

PubMed2005

Effects of shift work on QTc interval and blood pressure in relation to heart rate variability.

OBJECTIVES: There is evidence that shift work contributes to excess cardiovascular mortality. The purpose of this study was to determine the effects of shift work on heart rate-corrected QT (QTc) and blood pressure in relation to heart rate variability (CV(RR)). METHODS: The study population consisted of 153 male shiftworkers and 87 male day workers who were employed at a copper-smelting plant. The QTc interval, total power spectral density (t-PSD) of 100 RR intervals, PSDs with frequencies of 0.01 Hz-0.15 Hz and 0.15 Hz-0.40 Hz (PSD(LF) and PSD(HF)), CV(RR), low frequency (LF) component variability and high frequency (HF) component variability (CCV(LF) and CCV(HF)) and %LF (PSD(LF)/(PSD(LF)+PSD(HF)) .100) were measured (LF and HF components are thought to reflect the sympathetic and parasympathetic activities, respectively). RESULTS: The QTc interval was significantly longer in the shiftworkers than in the day workers, although there was no significant difference in systolic or diastolic blood pressure between the two groups. Also, the CCV(LF) and log(PSD(LF)) were significantly depressed in the shiftworkers. In the day workers, the QTc interval was significantly related to the CV(RR), log(t-PSD), CCV(HF), log(PSD(HF)),%LF, and log(LF/HF ratio) (partial correlation coefficient r=-0.305, -0.377, -0.312, -0.355, 0.297, and 0.277, respectively). In the shiftworkers only two relations of the QTc interval to non-specific CV(RR) and log(t-PSD) were significant. CONCLUSION: The clear association between long QTc interval and reduced parasympathetic activity observed in the day workers did not exist in the shiftworkers. Rather, the shiftworkers had a selective reduction in sympathetic drive, which may have compensated for prolonged QTc interval due to shift work. On the other hand, the impact of shift work on hypertension remains unclear, although reduced sympathetic drive in the shiftworkers may explain the absence of differences in blood pressure between shiftworkers and day workers to some extent.

Adult↗

PubMed1986

Usefulness of QTc interval on the discharge electrocardiogram for predicting survival after acute myocardial infarction.

The corrected QT (QTc) interval was measured on the discharge electrocardiogram of 457 consecutive patients who had survived the first 28 days after a first acute myocardial infarction (AMI). The patients were followed for 4 years. The QTc interval was not related to long-term survival after the acute phase of AMI. Sixteen percent of the patients had a QTc interval above the normal upper limit of 440 ms. Of them, 71% survived 4 years and 77% with a shorter QTc interval survived (p = 0.31). When mortality per 100 patient-years was calculated for different QTc intervals, with 10 ms accuracy, no consistent relation between the 2 variables was seen. Results that indicate a strong relation between QTc-interval prolongation and sudden death after AMI should be reevaluated. The QTc interval is not a useful prognostic tool after AMI.

Adult↗

PubMed1995

The QTc interval, autonomic neuropathy and mortality in hypoxaemic COPD.

Patients with hypoxaemic chronic obstructive pulmonary disease (COPD) have a subclinical autonomic neuropathy. Autonomic neuropathy has been associated with a prolonged electrocardiograph QTc interval and risk of ventricular arrhythmias and death. We studied cardiovascular autonomic nerve function and QTc interval at rest and during stress (a valsalva manoeuvre) in 34 patients with hypoxaemic COPD who were followed up after 2 yr. Seventeen patients had a subclinical autonomic neuropathy (group AN) and the remaining 17 were normal (group C). Group AN were significantly more hypoxaemic (PaO2 7.3 +/- 0.3 compared to 9.2 +/- 1.8, P < 0.05), had a lower FEV1 and had a longer QTc at rest (0.43 +/- 0.01 compared to 0.40 +/- 0.01, P < 0.01) and at peak valsalva (0.44 +/- 0.01 compared to 0.41 +/- 0.01, P < 0.05). When analysed after 2 yr, there were two deaths in group C and seven deaths in group AN. The QTc was abnormal > 0.44s at rest and at peak valsalva stress in five of group AN, three of these five patients died. QTc was normal at rest but abnormal at peak valsalva stress in eight further patients. This included three further patients from group AN of whom two had died and five group C patients which included both the group C deaths. The presence of autonomic neuropathy and QTc prolongation (> 0.44s) at rest was significantly associated (P < 0.05). Likewise QTc prolongation at the peak of a valsalva stress was significantly associated with death at 2 yr follow-up (P < 0.01) with an odds ratio of 11.1.(ABSTRACT TRUNCATED AT 250 WORDS)

Autonomic Nervous System Diseases↗

PubMed2004

QTc dispersion as a prognostic factor in intracerebral hemorrhage.

QTc dispersion in the electrocardiogram (ECG) is a new important prognostic factor for many diseases, but its role in intracerebral hemorrhage (ICH) is not clear. This study was performed to investigate the prognostic significance of QTc dispersion in the acute ICH patients. We studied the differences of QTc dispersion from the initial ECG in the ED between the survival to discharge and nonsurvival patients retrospectively. We found that the patients had lesser chance to survival to discharge if they had increased QTc dispersion, longer maximal QTc interval, lower Glasgow Coma Scale (GCS), and brainstem involvement in the univariate analyses. The QTc dispersion and GCS were the statistically significant independent predictors in the multiple logistic analyses. Increased QTc dispersion in the initial ED electrocardiograph is an important prognostic factor for ICH patients. More attention to the disposition and intensive care should be given for these patients.

Acute Disease↗

PubMed2004

Circadian variation of QTc dispersion in children with vasovagal syncope.

AIMS: To assess the validity of QTc dispersion to cardiac autonomic nervous function status. METHOD AND RESULTS: Prospective comparisons of QTc dispersion measurements in 77 neurally mediated cardiac syncope (NMCS) patients (29 boys, 48 girls, mean age 13.4+/-0.78) were evaluated. Head-up tilt test (HUT) was positive in 38 patients and negative in 39 patients. QTc dispersion was significantly higher early morning and late night in HUT-positive group compared with HUT-negative group (p<0.001). Although there was a circadian rhythm in HUT-positive group, there was no change on the QTc dispersion within a day in the HUT-negative group. QTc dispersion in the HUT-positive group was high in accordance with their high sympathetic nervous stimulation. Moreover, QTc dispersion was higher during late night and early morning than the rest of the day. CONCLUSION: These results may explain why the HUT-positive patients usually have their syncope attacks early in the morning. Additionally, we can use QTc dispersion measurement as a new noninvasive electrocardiographic test to evaluate cardiac sympathetic nervous system in NMCS.

Adolescent↗

PubMed2006

Assessment of QTc interval dispersion in patients with chronic heart failure secondary to Chagas-Hypertensive cardiomyopathy.

No previous study has examined the association of clinical variables and QTc interval dispersion in patients with Chagas-Hypertensive cardiomyopathy. Sixty-four patients with Chagas-Hypertensive cardiomyopathy were entered for the study. Seventy-one chronic Chagas' disease heart failure patients and 68 patients with Hypertensive cardiomyopathy heart failure were used in the comparison of QTc interval dispersion. The QTc interval dispersion was defined as the difference between maximum and minimum QTc. Median QTc interval dispersion was 75 (55) ms in patients with Chagas' cardiomyopathy, (56) 73 ms in patients with Hypertensive cardiomyopathy, and (87.3) 98 ms in patients with Chagas-Hypertensive cardiomyopathy (p>0.05). In patients with Chagas-Hypertensive cardiomyopathy, median QTc interval was (134) 100 ms in survivors and (87) 96 ms in nonsurvivors (p>0.05). Thus, QTc interval dispersion values in patients with Chagas-Hypertensive cardiomyopathy are not associated with mortality and similar to those found in patients with Chagas' cardiomyopathy and in patients with Hypertensive cardiomyopathy.

Chagas Cardiomyopathy↗

PubMed2006

Prolonged QTc interval and risk of sudden cardiac death in a population of older adults.

OBJECTIVES: This study sought to investigate whether prolongation of the heart rate-corrected QT (QTc) interval is a risk factor for sudden cardiac death in the general population. BACKGROUND: In developed countries, sudden cardiac death is a major cause of cardiovascular mortality. Prolongation of the QTc interval has been associated with ventricular arrhythmias, but in most population-based studies no consistent association was found between QTc prolongation and total or cardiovascular mortality. Only very few of these studies specifically addressed sudden cardiac death. METHODS: This study was conducted as part of the Rotterdam Study, a prospective population-based cohort study that comprises 3,105 men and 4,878 women aged 55 years and older. The QTc interval on the electrocardiogram was determined during the baseline visit (1990 to 1993) and the first follow-up examination (1993 to 1995). The association between a prolonged QTc interval and sudden cardiac death was estimated using Cox proportional hazards analysis. RESULTS: During an average follow-up period of 6.7 years (standard deviation, 2.3 years) 125 patients died of sudden cardiac death. An abnormally prolonged QTc interval (>450 ms in men, >470 ms in women) was associated with a three-fold increased risk of sudden cardiac death (hazard ratio, 2.5; 95% confidence interval, 1.3 to 4.7), after adjustment for age, gender, body mass index, hypertension, cholesterol/high-density lipoprotein ratio, diabetes mellitus, myocardial infarction, heart failure, and heart rate. In patients with an age below the median of 68 years, the corresponding relative risk was 8.0 (95% confidence interval 2.1 to 31.3). CONCLUSIONS: Abnormal QTc prolongation on the electrocardiogram should be viewed as an independent risk factor for sudden cardiac death.

Aged↗

PubMed2005

Measurement of QTc in patients receiving chronic methadone therapy.

Recent reports suggest that methadone may prolong the QTc interval and cause torsades de pointes. This study was conducted to evaluate the prevalence of QTc prolongation during oral methadone therapy and identify factors associated with prolongation. Patients receiving oral methadone as treatment for chronic pain or addiction were eligible for the study. One hundred four patients who were receiving > or = 20 mg methadone per day for > or = 2 weeks underwent electrocardiograms to measure QTc interval duration. Sixty-three (61%) patients were male and 63 (61%) were receiving methadone maintenance for opioid addiction. The mean (+/- SD) age was 45.3 +/- 9.4 years. The median (range) methadone dose was 110 mg/day (20-1200 mg/day); median (range) number of months on methadone was 12.5 months (1-444 months). The median (range) QTc interval was 428 msec (396-494 msec). Thirty-three percent had QTc prolongation (males 40%, females 20%; P=0.03). No patient had a QTc longer than 500 msec. Significant dose response was observed in males on methadone <12 months (rho=0.60, P=0.02). Our study suggests that methadone may prolong the QTc interval in specific subpopulations but poses little risk of serious prolongation.

Electrocardiography↗