Abnormal QT Interval Research Articles

Critical Volume of Human Myocardium Necessary to Maintain Ventricular Fibrillation.

Abnormal QT intervals, long QT or short QT, have been epidemiologically linked with sudden cardiac death because of ventricular fibrillation (VF). Consequently, Food and Drug Administration recommends testing all pharmacological agents for QT toxicity as a risk factor for cardiac toxicity. Such tests assess QT/QTc interval, which represents ventricular depolarization and repolarization. However, the current QT toxicity analysis does not account for the well-known anisotropy in cardiac tissue conductivity. Mines demonstrated in 1913 that cardiac wavelength (λ) determines inducibility of reentrant arrhythmia, where both repolarization time or action potential duration and conduction velocity determine λ=action potential duration×conduction velocity. We aimed to determine the role of anisotropic wavelength in inducibility of VF in explanted human left ventricular preparations. We tested the hypothesis that 3-dimensional cardiac wavelength, which takes into account anisotropic cardiac tissue conductivity, can accurately predict VF sustainability. We conducted panoramic optical mapping of coronary perfused human left ventricular wedge preparations subjected to pharmacologically induced shortening and prolongation of action potential duration, by IK,ATP agonist pinacidil and antagonist glybenclamide, respectively. This measured action potential duration, conduction velocity, and thus determined pacing cycle length-dependent wavelengths in longitudinal (λL), transverse (λTV), and transmural (λTM) directions using S1S1 pacing protocol, from which wavelength volume (Vλ) was determined, as Vλ=λL×λTV×λTM, and compared with tissue volume. We tested a hypothesis that tissue volume/Vλ ratio can predict VF sustainability. At baseline, at pacing rate of 240 beats per minute, the wavelengths were λL=9.6±0.6 cm, λTV=4.2±0.3 cm, and λTM=5.8±0.2 cm, respectively (n=7), and thus Vλ=246.4±42.1 cm3. Administration of pinacidil at escalating concentrations progressively decreased Vλ, and VF became sustained, when tissue volume/Vλ was above safety factor κ=4.4±0.6 (n=9) during rapid pacing. Treatment with glybenclamide decreased VT/Vλ below κ at any pacing rate and prevented VF sustainability. Sustained VF was only sustained in ventricular volume exceeding critical Vλ=λL×λTV×λTM.

Serum albumin level and abnormal corrected QT interval in patients with coronary artery disease and chronic kidney disease.

Lower concentrations of serum albumin appear to be associated with an increased risk of all-cause and cardiovascular mortality, coronary heart disease, heart failure and stroke. However, little is known about the relationship between serum albumin level and prolonged QT interval. To investigate whether lower serum albumin is associated with prolonged QT interval by recording 12-lead electrocardiography in patients with coronary artery disease and chronic kidney disease. This study included 1383 consecutive patients with coronary artery disease and chronic kidney disease (841 with acute coronary syndrome and 542 with elective percutaneous coronary intervention patients) who were enrolled in a disease management programme. Twelve-lead electrocardiography was recorded in each subject. We assessed the relationship between albumin levels (both as a continuous variable and stratified by tertile) at admission and corrected QT (QTc) prolongation. Patients with abnormal QTc interval had lower serum albumin levels than those with normal and borderline QTc intervals. Statistically significant negative associations were observed between serum albumin levels and QTc interval (β = -0.211, P < 0.0001). Using multivariate and trend analyses, a lower concentration of serum albumin was independently associated with QTc prolongation in both the patients with acute coronary syndrome and elective percutaneous coronary intervention patients. Concentrations of serum albumin were significantly lower in the patients with an abnormal QTc interval and were associated with QTc prolongation. Further studies are needed to clarify whether lower serum albumin plays a role in the pathogenesis of QTc prolongation.

Comparative efficacy and safety between amisulpride and olanzapine in schizophrenia treatment and a cost analysis in China: a systematic review, meta-analysis, and cost-minimization analysis

BackgroundAmisulpride was introduced into China in 2010 as a second-generation atypical antipsychotic, while olanzapine has been on the market since 1999 as one of the leading treatments for schizophrenia in China. Since more Chinese patients are gaining access to amisulpride, the study aims to compare the efficacy, safety, and costs between amisulpride and olanzapine for schizophrenia treatment in China.MethodsPubMed, Embase, the Cochrane library, China National Knowledge Infrastructure (CNKI) and WanFang database were systematically searched for randomized controlled trials (RCTs) up to July 2018. The Cochrane Risk of Bias tool was utilized to assess the quality of included studies. A meta-analysis was performed to compare the efficacy and safety of amisulpride and olanzapine, followed by a cost-minimization analysis using local drug and medical costs reported in China.ResultsTwenty RCTs with 2000 patients were included in the systematic review. There were no significant differences between amisulpride and olanzapine on efficacy measures based on scores from the Positive and Negative Syndrome Scale, the Scale for the Assessment of Negative Symptoms, the Brief Psychiatric Rating Scale and the Clinical Global Impressions-Severity or Improvement. For safety outcomes, amisulpride was associated with lower fasting blood glucose and less abnormal liver functions as well as significantly lower risks of weight gain, constipation, and somnolence; olanzapine was associated with significantly lower risks of insomnia and lactation/amenorrhea/sexual hormone disorder. No significant differences were found in risks of extrapyramidal symptoms (EPS), tremor, akathisia, abnormal corrected QT interval. Cost-minimization analysis showed that amisulpride was likely to be a cost-saving alternative in China, with potential savings of 1358 Chinese Yuan (CNY) per patient for a three-month schizophrenia treatment compared with olanzapine.ConclusionAs the first meta-analysis and cost-minimization analysis comparing the efficacy, safety and cost of amisulpride and olanzapine within a Chinese setting, the study suggests that amisulpride may be an effective, well-tolerated, and cost-saving antipsychotic drug alternative in China.

QT interval prolongation in opioid agonist treatment: analysis of continuous 12-lead electrocardiogram recordings.

AimsMethadone is a widely used opioid agonist treatment associated with QT prolongation and torsades de pointes. We investigated the QT interval in patients treated with methadone or buprenorphine using continuous 12‐lead Holter recordings.MethodsWe prospectively made 24‐h Holter recordings in patients prescribed methadone or buprenorphine, compared to controls. After their normal dose a continuous 12‐lead Holter recorder was attached for 24 h. Digital electrocardiograms were extracted hourly from the Holter recordings. The QT interval was measured automatically (H‐scribe software, Mortara Pty Ltd) and checked manually. The QT interval was plotted against heart rate (HR) on the QT nomogram to determine abnormality. Demographics, dosing, medical history and laboratory investigations were recorded.ResultsThere were 58 patients (19 methadone, 20 buprenorphine and 19 control); median age 35 years (20–56 years); 33 males. Baseline characteristics were similar. Median dose of methadone was 110 mg day–1 (70–170 mg day–1) and buprenorphine was 16 mg day–1 (12–32 mg day–1). Seven participants had abnormal QT intervals. There was a significant difference in the proportion of prescribed methadone with abnormal QT intervals, 7/19 (37%; 95% confidence interval: 17–61%), compared to controls 0/19 (0%; 95% confidence interval: 0–21%; P = 0.008), but no difference between buprenorphine and controls (0/20). QT vs. HR plots showed patients prescribed methadone had higher QT‐HR pairs over 24 h compared to controls. There was no difference in dose for patients prescribed methadone with abnormal QT intervals and those without.ConclusionsMethadone is associated with prolonged QT intervals, but there was no association with dose. Buprenorphine did not prolong the QT interval. Twenty four‐hour Holter recordings using the QT nomogram is a feasible method to assess the QT interval in patients prescribed methadone.

Desvenlafaxine overdose and the occurrence of serotonin toxicity, seizures and cardiovascular effects

Context: Desvenlafaxine is used to treat major depression. Desvenlafaxine is also the active metabolite of venlafaxine. Venlafaxine overdose can cause serotonin toxicity, seizures and cardiovascular effects, but there is limited information on desvenlafaxine overdose.Objective: We aimed at investigating the clinical effects and complications from desvenlafaxine overdose.Materials and methods: This was a retrospective observational study of desvenlafaxine overdoses over a six-year period. Demographic details, dose and timing of the overdose, together with clinical effects, treatment and complications were extracted from a local hospital network database or the medical records of patients following hospital admission with a desvenlafaxine overdose.Results: There were 182 cases of desvenlafaxine overdose included in the study. From the 182 cases, 75 were desvenlafaxine (± alcohol) only ingestions and 107 included one or more co-ingested drugs. In single-agent desvenlafaxine ingestions, median age was 25 years (range: 13–68 years) with a median ingested dose of 800 mg (range: 250–3500 mg; interquartile range (IQR): 600–1400 mg), and 54/75 (72%) were female. The Glasgow Coma Score (GCS) was 15 in 68/74 (92%) patients, 13–14 in 5/74 (7%), and was seven in one patient following aspiration. Mild hypertension (systolic blood pressure [BP] > 140–180 mmHg) occurred in 23/71 patients (32%), and tachycardia occurred in 29/74 (39%) patients. There were no abnormal QT intervals and no QRS >120 m s. Serotonin toxicity was diagnosed by the treating physician in 7/75 (9%) patients, but only one of these met the Hunter Serotonin Toxicity Criteria. None of the 75 patients who took desvenlafaxine only (± alcohol) had seizures, were admitted to intensive care or died. In comparison, the 107 patients taking desvenlafaxine in overdose with other medications developed more pronounced toxicity. Generalised seizures occurred in 5/107 (5%), but in three of these cases co-ingestants were possible proconvulsants. Fifteen patients had a GCS ≤9 and none had an abnormal QT or QRS. Severe effects appeared to be associated with coingestants.Conclusion: Desvenlafaxine overdose causes minor effects with mild hypertension and tachycardia. The risk of seizures or serotonin toxicity is low.

Transient Long QT Development in a Patient with Takotsubo Cardiomyopathy

Abstract QT interval prolongation on the electrocardiogram is considered a precursory sign for imminent, potentially lethal ventricular arrhythmias. Beside the inherited condition of long QT syndrome, numerous drugs, certain electrolyte disturbances and early transmural ischemia have been identified to induce reversible prolongation of the QT interval, collectively called as acquired long QT syndrome. Herein we describe a case of a patient with transient QT prolongation and Takotsubo cardiomyopathy, a rather infrequent cause of long QT development. Serial changes of the repolarization pattern were documented to demonstrate progression and resolution of the abnormal QT interval.

Clinical conditions associated with abnormal QT interval: clinical implications

Impressive progress has been made in the last 40 years in the understanding of the role of QT interval and its genetic basis in sudden cardiac death risk. The present review will provide a first practical part on QT measurement and its correction for heart rate. Subsequently, the long QT syndrome and short QT syndrome will be described, as the two main arrhythmogenic congenital heart diseases characterized by abnormal QT length. Furthermore, we will discuss about prolonged QT in the pathogenesis of sudden infant death syndrome and the preventive role of neonatal ECG screening. The prognostic role of QT interval will be presented also in the context of myocardial infarction and hypertrophic cardiomyopathy. The last part of the review is devoted to future perspectives and latest results on modifier genes.

Prevalence of QT interval prolongation in inflammatory bowel disease.

There is growing evidence linking various cardiac complications with inflammatory bowel disease (IBD). Electrolyte abnormalities, chronic inflammation, and medication use (such as Infliximab) that are associated with IBD are all independent risk factors for QT interval prolongation. Given that malignant ventricular arrhythmias are associated with QT interval prolongation, it is important to risk stratify this subset of patients. Our objective was to evaluate the prevalence of abnormal QT interval prolongation (defined by a QT interval of >450 ms in men and >460 ms in women) in an IBD population. A retrospective chart review of patients with IBD from the Metro Hospital database was performed. Patients' demographic characteristics and laboratory data were abstracted. "RR" and "QT" intervals were measured from the last available electrocardiogram, and corrected QT (QTc) interval was calculated from lead II using Bazett's formula. Of 142 eligible patients, 42.3% (n=22/52) of males and 48.9% (n=44/90) of females had a prolonged QTc interval. Patients with IBD having a prolonged QTc interval had a higher body mass index than those with a normal QTc interval (29.7±6.9 vs. 26.2±5.9, p=0.005). Our study demonstrates that patients with IBD are at a higher risk of developing QTc interval prolongation.

The Safety and Effectiveness of Droperidol for Sedation of Acute Behavioral Disturbance in the Emergency Department

We investigate the safety and effectiveness of droperidol for sedation of acute behavioral disturbance in the emergency department (ED). This was a prospective observational study in 6 EDs (August 2009 to April 2013). Adult patients requiring parenteral sedation for acute behavioral disturbance received droperidol 10 mg. If this did not sedate the patient within 15 minutes, further sedation was allowed but droperidol 10 mg was recommended as part of a sedation protocol. The primary outcome was the proportion of patients with an abnormal QT interval, defined by the at-risk line on the QT nomogram. Secondary outcomes were effectiveness determined by the time to sedation measured on the Sedation Assessment Tool, use of additional sedation, adverse events, and injury to staff or patients. There were 1,009 patients with an ECG performed within 2 hours of droperidol administration, with a median dose of 10 mg (interquartile range [IQR]10 to 17.5 mg). Thirteen of the 1,009 patients had an abnormal QT (1.3%; 95% confidence interval 0.7% to 2.3%), but 7 of these had another cause attributed for prolonged QT (methadone, escitalopram, amiodarone, or preexisting). In 1,403 patients sedated with a median total dose of droperidol of 10 mg (IQR 10 to 20 mg), the median time to sedation was 20 minutes (IQR 10 to 30 minutes) and 97% were sedated within 120 minutes. Additional sedation was required for 435 patients (31.0%; 95% confidence interval 28.6% to 33.5%). Adverse events occurred in 70 patients (5%) and oversedation without complications in 109 (8%), the latter more common for patients receiving benzodiazepines as additional sedation (16/109 [15%]). There were no cases of torsades de pointes. Injuries occurred in 34 staff members and 4 patients. The study supports the use of high-dose droperidol as a safe sedating agent for patients with acute behavioral disturbance in the ED. There is no evidence of increased risk for QT prolongation with the doses used in this study.

QTc interval prolongation predicts the ablation outcome in hypertensive patients with paroxysmal atrial fibrillation

An abnormal corrected QT (QTc) interval is associated with the development of atrial fibrillation (AF). It is unclear whether QTc interval is a marker of arrhythmia recurrence after radiofrequency catheter ablation (RFCA) in patients with AF. This study sought to determine the relationship between abnormal QTc interval and the recurrence after RFCA in hypertensive patients with paroxysmal AF. Two hundred and forty-two hypertensive patients with paroxysmal AF who underwent first time RFCA were retrospectively evaluated. Baseline data and QTc before the procedure were collected. Ninety-eight patients had AF recurrence after a mean follow-up of 17.0 ± 9.4 months. Those experiencing recurrence had a longer QTc interval than those without recurrence (429 ± 26 vs. 419 ± 23 ms, P = 0.004). Multivariate Cox regression analysis demonstrated the QTc interval and left atrial diameter (LAD) as independent predictors of AF recurrence. Patients with a long QTc interval were at an increased risk of AF recurrence (hazard ratio 2.757, 95% CI 1.661–4.611, P < 0.001) after adjustment for multiple factors. The QTc interval had an incremental value combined with the LAD in predicting AF recurrence after RFCA. The patients with a large LAD and a long QTc interval had a much higher AF recurrence rate compared with those with a small LAD and a non-long QTc interval (78 vs. 27%, P < 0.001). QTc interval prolongation is an independent risk factor for AF recurrence after RFCA in hypertensive patients. It provides a simple predictor for identifying the patients with hypertension likely to have AF recurrence after RFCA.

Risk assessment of drug-induced QT prolongation.

Drugs can cause prolongation of the QT interval, alone or in combination, potentially leading to fatal arrhythmias such as torsades de pointes. When prescribing drugs that prolong the QT interval, the balance of benefit versus harm should always be considered. Readouts from automated ECG machines are unreliable. The QT interval should be measured manually. Changes in heart rate influence the absolute QT interval. Heart rate correction formulae are inaccurate, particularly for fast and slow heart rates. The QT nomogram, a plot of QT interval versus heart rate, can be used as a risk assessment tool to detect an abnormal QT interval.

Prolonged QT Risk Assessment in Antipsychotic Overdose Using the QT Nomogram

Antipsychotic drugs are frequently reported to cause QT prolongation and torsade de pointes. We aim to investigate the potential risk of torsade de pointes in antipsychotic overdose by assessing the QT interval with the QT nomogram. All presentations to a toxicology service between January 1987 and May 2013 were reviewed. Admissions with single ingestions of an antipsychotic greater than maximum daily dose were extracted. Demographics, dose, ECG, and outcomes (arrhythmias and death) were obtained. QT intervals in multiple leads were manually measured and the median taken. QT-heart rate (QT-HR) pairs were plotted on the QT nomogram and defined as prolonged if above the abnormal line. The QTcF (Fridericia's HR correction) was calculated and compared with dose. From 2,356 antipsychotic overdoses, 494 were included. There were no abnormal QT-HR pairs in 4 aripiprazole, 31 pericyazine, 14 trifluoperazine, and 7 haloperidol overdoses. Abnormal QT intervals occurred in 9 of 16 amisulpride overdoses (56%; 95% confidence interval [CI] 31% to 79%), 16 of 57 thioridazine overdoses (28%; 95% CI 17% to 42%), and 5 of 29 chlorpromazine overdoses (17%; 95% CI 7% to 36%). Abnormal QT intervals occurred in 5 of 41 risperidone overdoses (12%; 95% CI 5% to 27%), 10 of 202 quetiapine overdoses (5%; 95% CI 3% to 9%), and 2 of 76 olanzapine overdoses (3%; 95% CI 0.5% to 10%), but there was no correlation between dose and QTcF, and most abnormal QT intervals were at fast HR. An additional 186 single antipsychotic ingestions with noncardiotoxic coingestants had similar proportions of abnormal QT. There was 1 case of torsade de pointes in a thioridazine overdose. There appeared to be significant risk of QT prolongation with amisulpride and thioridazine overdoses. Although there were abnormal QT intervals for quetiapine, olanzapine, and risperidone overdoses, they were associated with tachycardia and not dose dependent, and so were unlikely to be associated with increased torsade de pointes risk.

Serum total p-cresylsulfate level is associated with abnormal QTc interval in stable angina patients with early stage of renal failure

Backgroundp-Cresylsulfate (PCS), a protein-bound uraemic retention solute, is known to cause endothelial dysfunction and possibly plays a role in coronary atherosclerosis. Furthermore, the association among serum total PCS, major adverse cardiovascular events, and all-cause mortality were also found in previous studies. However, little is known about the relationship between total PCS level and prolonged QT interval. We assessed whether serum total PCS level is related with prolonged QT interval by measuring 12-lead electrocardiogram (ECG) recording in stable angina patients with early stage of renal failure. MethodsSerum total PCS concentrations were measured by using the Ultra Performance LC System in 154 consecutive stable angina patients. A 12-lead ECG recording was obtained from each subject. ResultsPatients with abnormal corrected QT (QTc) interval have higher median serum total PCS levels than patients with normal QTc interval. Statistically significant associations were observed between the serum total PCS levels and the QTc interval (r=0.217, P=0.007). Using multivariate and trend analyses, serum total PCS level was independently associated with QTc prolongation. ConclusionsThis study indicates that serum total PCS levels are significantly higher in the presence of abnormal QTc interval and are associated with the QTc prolongation. Whether total PCS plays a role in the pathogenesis of QTc prolongation requires future investigation.

Amiodarone-Induced Life- Threatening Ventricular Arrhythmias in a Patient with Cerebrogenic QT Interval Prolongation. Clinical Implications

Amiodarone-Induced Life- Threatening Ventricular Arrhythmias in a Patient with Cerebrogenic QT Interval Prolongation. Clinical Implications Acquired causes of abnormal QT interval prolongation include drug effect, toxins, electrolyte imbalance, hypothermia, severe bradyarrhythmias, myocardial ischemia, heart failure, altered nutritional states, hypothyroidism, Coxsackie B3 myocarditis, immunodeficiency virus syndrome.

Prevalence of Conduction Abnormalities in a Systolic Heart Failure Population by Race, Ethnicity, and Gender

There is paucity of data regarding conduction abnormalities in the Hispanic population with systolic heart failure (HF). We aimed to evaluate the prevalence of electrocardiogram (ECG) abnormalities in a systolic HF population, with attention to the Hispanic population. A cross sectional study of 926 patients enrolled in a systolic HF disease management program. ECGS were obtained in patients with an ejection fraction (EF) ≤ 40% by echocardiography at enrollment. Univariate and multivariate analysis adjusted by ethnicities was performed. White patients exhibited higher prevalence of atrial fibrillation (14.7%) than black patients (8.0%, P = 0.01) whereas Hispanics presented higher prevalence of paced rhythm (14.3% in Hispanics vs. 6.5% in whites and 5.2% in blacks, P<0.01 for both comparisons), higher prevalence of left bundle branch block (LBBB, 14.5% in Hispanics vs. 8.8% in whites and 5.8% in blacks, P = 0.002) and increased frequency of abnormal QT intervals (76.7% in Hispanics) than whites (59.6%) and blacks (69%) patients (P< 0.01 for both comparisons). A QRS interval greater than 120 ms was less prevalent among blacks (15.8% vs. 26.0% in whites and 25.3% in Hispanics, P = 0.01 for both comparisons). Univariate and multivariate analysis disclosed no influence of other characteristics (age, sex, coronary artery disease, hypertension, ejection fraction, medications) in the ECG findings. Hispanics with Systolic HF presented with increased prevalence of paced rhythm, LBBB, and abnormal QT intervals. Attention should be addressed to these ECG variations to recommend additional guidance for therapeutic interventions and provide important prognostic information.

Abstract P344: Prevalence of Conduction Abnormalities in a Systolic Heart Failure Disease Management Population by Race, Ethnicity, and Gender

While there have been several studies evaluating the prevalence of electrocardiogram (ECG) conduction abnormalities such as left bundle branch block (LBBB) and atrial fibrillation (AF) in the general population, there are none currently describing that of the Hispanic population in patients with systolic heart failure. Given the need for examining race and ethnic differences in ECG abnormalities, the primary purpose of this study is to compare the prevalence of ECG abnormalities in three systolic heart failure populations from two indigent heart failure clinics. The study examines EKG difference among three ethnic groups: Caucasians, African-Americans, and Hispanics. We also investigated ECG differences between genders. This is a cross sectional study. A total of 926 patients were enrolled in a systolic heart failure disease management program in two safety net hospitals in Florida and Louisiana. Inclusion criteria was an ejection fraction (EF) &lt; or equal to 40% by echocardiography, and ECGs which were obtained closest to the date of enrollment. Caucasian patients had more atrial fibrillation than African-American patients. Hispanics had more paced rhythm, left bundle branch block and abnormal QT intervals than Caucasian or African-American patients. A QRS interval greater than 120 milliseconds (ms) was less prevalent among African-Americans. ECG conduction abnormalities vary across race, ethnicity, and gender. Adequate medical attention should be addressed to these variations since relevant ECG findings can offer additional guidance for therapeutic interventions, as well as provide important prognostic information and potentially modify morbidity and mortality rates.

Prediction of Torsade de Pointes From the QT Interval: Analysis of a Case Series of Amisulpride Overdoses

Electrocardiograms (ECGs) from a case series of 86 amisulpride overdose events in 66 patients were reviewed for abnormal QT intervals and torsade de pointes (TdP). Eight patients exhibited TdP. In this investigative case series, the magnitude of prolongation of the QT interval was a stronger predictor of TdP than the mere presence of a prolongation per se.

Gauging the Risk of Arrhythmic Death by Common Genetic Variants

The holy grail of personalized medicine in clinical cardiac electrophysiology is to establish a reproducible genetic imprint or the associated intermediate phenotype (“endophenotype”) that would with high accuracy predict arrhythmic death in an individual. Although we are far from it, the study in this issue of Circulation: Cardiovascular Genetics by Noseworthy et al1 is another step in the right direction. It is well established that an abnormal QT interval (ie, too long or too short) is a predictor of arrhythmogenic risk in patients with the rare syndromes caused by ion channel mutations. However, the role of QT in gauging the risk of death in the general population is recent,2 complex,3,4 and laced with fundamental questions that remain unanswered. Noseworthy et al tackle this problem straight on and investigate the value of common genetic variants for predicting QT duration and sudden cardiac death (SCD) risk. Article see p 305 The QT interval is an inexpensive, easily measurable, generally reproducible endophenotype, which makes it attractive for predicting risk of SCD as shown by present and prior studies.2 However, the QT is a “read-out” of complex interactions between multiple genes encoding both ion channel1 and non–ion channel proteins5 and multiple environmental factors (drugs, electrolytes, hormones, body temperature, etc). As a result, the QT duration can fluctuate widely …

Utilidad del cribado electrocardiográfico en población neonatal

Introduction Congenital long QT syndrome is a rare disease, but is responsible for nearly 10% of Sudden Infant Death Syndrome. It is characterized by an abnormal prolonged QT interval in the basal electrocardiogram (ECG) with life-threatening arrhythmias which occur in previously asymptomatic patients and are preventable with an appropriate treatment. Aims The impact of introducing ECG-screening in newborns is studied and main ECG-measurements are described in our population. Material and methods Twelve-lead ECG was carried out. Measurements: RR, PR and QT interval, heart rate corrected QT interval, R wave voltage in V1, AVR and AVL, Q wave in I and AVL, P amplitude and voltage, right bundle branch block and ST elevation (Brugada pattern) and delta wave. It was considered pathological: QTc >0.44 or <0.30 seconds; R >12 in V1 and >8 mm in AVR; R >7.5 mm in AVL; Q >25% QRS in I and AVL; Brugada pattern; delta wave. Results A total of 1061 healthy children were born in our hospital between 29 May 2007 and 12 December 2008, of which 50.3% were males. An ECG was performed on 1006 (94.8%). Five ECG were pathological (0.5%): 2 long QT interval, 2 Wolf-Parkinson-White, 1 pathological Q-wave. A second ECG confirmed except for 2 long QT. No structural heart disease was found. Conclusions ECG-screening in newborns is an innocuous, low-cost and parent-well-accepted test that allows us to diagnose asymptomatic but potentially lethal and preventable heart disease; main intervals and waves in our population are describes in this study.

Abnormal repolarization dynamics revealed in exercise test in long QT syndrome mutation carriers with normal resting QT interval

The identification of affected family members with long QT syndrome (LQTS) is often difficult due to their normal-or only marginally lengthened-QT interval duration. We examined whether physical exercise test could increase the ability to detect the mutation carrier status in phenotypically normal LQTS family members. Sixty-six subjects were included: 15 were carriers of KCNQ1 (LQT1); 15 of KCNH(2) (LQT2); and 9 of SCN5A (LQT3) gene mutations with no, or borderline, QT lengthening; and 27 were healthy controls. Multiple electrograms over the precordial area were recorded during workload and recovery phases of exercise test. QT intervals and T peak to T end intervals (Tpe intervals) were determined using an automatic algorithm at specified heart rates (HR).The LQT1 mutation carriers had QT interval most prolonged during exercise and recovery, whereas the LQT2 carriers had QT interval longest at low exercise HR. The LQT3 carriers had QT interval longest at rest. The Tpe interval remained nearly unchanged during exercise in LQT1, but shortened in LQT2 and in LQT3 carriers. The Tpe interval was longest in LQT2 carriers at the end of the recovery phase. Tentative dichotomizing values of QT and Tpe intervals improved sensitivity and specificity in distinguishing LQTS subtypes, compared with the QT interval duration alone. LQTS mutation carriers lacking diagnostic QT interval prolongation exhibit abnormal QT and Tpe interval adaptations during physical exercise test. Looking for subtype-specific adaptations might facilitate the identification of LQTS mutation carriers when molecular genetic analysis is not available.