QTc Dispersion Research Articles

1663 Early Coronary Flow and ECG Changes Following Cardiopulmonary Bypass Surgery in Children with Congenital Heart Disease

BackgroundSurgery with cardiopulmonary bypass (CPB) remains the mainstay of therapy in children with congenital heart defects but little is known about its pathophysiologic consequences. We have recently demonstrated that CPB...

QT Interval prolongation and dispersion: Epidemiology and clinical correlates in subjects with newly diagnosed systemic hypertension in Nigeria

Background:The use of easily obtainable clinical and laboratory parameters to identify hypertensive patients with increased cardiovascular risk in resource limited settings cannot be overemphasized. Prolongation of QT intervals and increased dispersion has been associated with increased risk of cardiovascular death. The study aimed at describing the epidemiology of QT interval abnormalities among newly diagnosed hypertensive subjects and associated clinical correlates.Materials and Methods:One hundred and forty newly diagnosed hypertensive subjects and 70 controls were used for this study. Clinical and sociodemographic characteristics were obtained. Twelve lead resting electrocardiography, QT dispersion, heart rate corrected minimum and maximum QT intervals were determined manually. Increased QTcmax was defined at QTcmax >440msec. QT parameters were compared between various groups. SPSS 16.0 was used for data analysis.Results:The hypertensive subjects were well matched in age and gender distribution with controls. QTmax and QTcmax were significantly higher among hypertensive subjects than controls (379.7±45.1 vs. 356.7±35.6, 447.5± 49.0 vs. 414.5 ±34.7 ms, respectively, P<0.05). QTd and QTcd were also significantly higher among hypertensive subjects than controls (62.64±25.65 vs. 46.1±17.2, 73.8 ±30.0 vs. 52.5±18.8, respectively, P<0.05). Seventy three (52.14%) of the hypertensive subjects had QTcmax >440ms compared to 21.43% of controls, P=0.01. Increased QTc dispersion was present in 36.4% of hypertensive subjects. Hypertensive subjects with QT abnormalities had significantly higher mean waist hip ratio, mean body mass index and a higher proportion of smoking than controls.Conclusion:QT prolongation and increased QTc dispersion are common among newly diagnosed hypertensive Nigerians and seem to be significantly associated with obesity. Effective antihypertensive therapy and control of obesity are important management modality for newly diagnosed hypertensive patients.

Dispersion Durations of P-wave and QT Interval in Children With Congenital Heart Disease and Pulmonary Arterial Hypertension

This study aimed to investigate homogeneity disorders of ventricular repolarization and atrial conduction via QT dispersion and P-wave dispersion in children with congenital heart disease (CHD) and pulmonary arterial hypertension (PAH). Three groups of 20 each were generated and involved in this study. The first group included 20 children with both CHD and PAH. The second group consisted of 20 children with CHD but no PAH, and the third group was composed of 20 age- and sex-matched healthy children. Electrocardiographic records were used to determine P-wave, QT, and corrected QT (QTc) dispersions. The pulmonary hypertension group compared with the group having no pulmonary hypertension and the control group showed a significantly longer P-wave dispersion duration (39.10±9.54 vs. 26.30±4.99ms, p<0.001; and 24.80±6.94ms, p<0.001, respectively) and QT dispersion duration (52.80±15.11 vs. 37.60±6.00ms, p<0.001; and 35.00±7.77ms, p<0.001, respectively). In addition, the durations of maximum QTc and QTc dispersion were significantly longer in pulmonary hypertension group than in the other two groups. The risk of atrial and ventricular arrhythmia was found to be increased in the patients with both CHD and PAH. Physicians should pay close attention to possible atrial and ventricular arrhythmias during the treatment and follow-up evaluation of these patients.

QTc Dispersion and T-Wave Alternans as Predictors of Mortality in Dogs with Dilated Cardiomyopathy and Ventricular Tachycardia in Holter Monitoring. a Retrospective Study

Abstract The study presents a comparison of the results received from dogs with dilated cardiomyopathy (DCM) that died during the first 30 d of observation and from dogs with DCM that survived the first 30 d after the ECG. No differences were noted in the duration of QT or QTc in healthy dogs and dogs with DCM. QTcd was significantly higher in dogs with DCM and in dogs with DCM, which did not survive over 30 d of observation and dogs with DCM that died after the 30th d of observation. The presence of T-wave alternans (TWA) was more frequently observed in dogs with DCM (85% of the dogs) that died in less than 30 d during the observation. QTcd and TWA seem to be a useful non-invasive diagnostic tool to anticipate the risk of cardiac death in dogs with DCM.

Arrhythmias as trigger for acute exacerbations of chronic obstructive pulmonary disease

Acute exacerbations of chronic obstructive pulmonary disease (COPD) sometimes appear to occur without a precipitating cause. Heterogeneous repolarization and arrhythmias occur in COPD patients. Given the close inter-relation between heart and lung, we hypothesized that unrecognized arrhythmias might be precipitants of acute exacerbations. Electrocardiograms (ECG) of thirty patients during acute exacerbations were compared with ECG during stable phase. P wave dispersion was used to assess atrial depolarization heterogeneity, and dispersion of QT interval to assess ventricular repolarization. p < 0.05 was considered significant. Frequent exacerbations were defined as two or more exacerbations in a year. Mean age of patients was 70.3 ± 11.8 SD years. P wave dispersion was greater during acute exacerbation than during stable phase (56.7 ± 19.2 vs 47.7 ± 15.9 ms, p = 0.009). There was a trend toward greater QTc dispersion (108.3 ± 61.7 vs 90.3 ± 47.0 ms, p = 0.13) in acute exacerbation compared to stable phase. Sixteen (53%) had frequent exacerbations. There was a significant difference in PR interval during stable phase between those with frequent exacerbations and those without (163.9 + 17.4 vs. 145.1 + 22.8; p = 0.02). The P wave dispersion during stable phase was greater in those with frequent exacerbations, but did not reach statistical significance (52.6 + 18.8 vs. 42.2 + 9.8 ms; p = 0.06). P wave dispersion is more in the acute phase than in stable phase, and is greater in patients with more frequent exacerbations. This does not prove, but suggests an intriguing possibility that P wave dispersion predates acute exacerbations. This might be a new target for prediction, prevention and therapy of acute exacerbations of COPD.

Risperidone and Corrected QT-interval Prolongation in Surface Electrocardiogram

Risperidone is an antipsychotic medication suspected of causing QT prolongation and several cases are reported in this regard. However, available information with respect to its effect on QT interval is limited especially from different settings. The aim of this study was to assess the effect of risperidone in lengthening QT interval among psychotic patients referred to a psychiatric ward in North West of Iran. A controlled cohort study was conducted on psychotic patients referred to Razi Hospital from April 2010-2011. The treatment cohort groups were 120 patients receiving risperidone for the first time during their treatment. The comparison cohort included 60 control patients who were not receiving risperidone. An electrocardiogram was obtained from all the study participants at admission time, one week afterwards and at discharge. Corrected QT interval (QTc) was determined using Bazett's formula. QTc dispersion was calculated as Max(QTc)-Min(QTc). Data were analyzed using SPSS statistical software package. The mean change in QTc measures over time was not statistically significant in control group. However, QTc increment was statistically significant over time in V1 and V3 leads in risperidone group. Multivariate longitudinal data analysis, using between-effects model, to manage multiple measurements over time found the overall QTc trend to be different between the groups (p < 0.01). Risperidone may have significant effects on QT interval and QT dispersion. Physicians and psychiatrists should be aware that prolonged QTc interval is a potential indicator of cardiovascular risk and should be cautious in prescribing potentially QT-prolonging medications, at least to certain patients.

Selection of Patient for Cardiac Resynchronization Therapy: Role of QT Corrected Dispersion

About 30 to 50% of patients undergoing cardiac resynchronization therapy (CRT) may not show clinical or echocardiographic improvement, despite fulfilling guidelines recommendations for CRT. For this reason, we need a more accurate method to assess CRT eligibility. The aims of this study were to verify, on a 12-month follow-up, the usefulness of QT corrected dispersion (QTcD) in a patient's selection for CRT. We stratified 53 patients who underwent CRT, into two groups based on the estimation of QTcD, that is, QTcD > 60 ms and QTcD ≤ 60 ms. In all patients were performed New York Heart Association (NYHA) class determination, six-minute walking test, QtcD, and QRS measurements, and complete echocardiographic assessment at 1, 3, 6, and 12 months after implantation. At baseline, there were no significant differences in clinical, echocardiographic, and electrocardiographic parameters duration between two groups. At 12-month follow-up between the two groups, there were significant differences in NYHA (1.2 ± 0.4 vs 2 ± 0.6; P < 0.01), six-minute walking distance (422 ± 68 vs 364 ± 68; P < 0.01), left ventricular (LV) ejection fraction (34 ± 7% vs 28 ± 6%; P < 0.01), LV end-diastolic diameter (57 ± 7 vs 63 ± 8; P < 0.01), and LV intraventricular dyssynchrony (24 ± 14 vs 39 ± 23; P < 0.01). This study suggests that QTc dispersion in addition to QRS duration could improve the sensitivity of electrocardiogram in a patient's selection for CRT.

Effect of Weight Loss After Bariatric Surgery on Left Ventricular Mass and Ventricular Repolarization in Normotensive Morbidly Obese Patients

To assess the effect of weight loss on ventricular repolarization in morbidly obese patients, 39 normotensive subjects whose baseline body mass indexes were ≥40 kg/m(2) before weight loss from bariatric surgery were studied. All patients were free of underlying organic heart disease, heart failure, and conditions that might affect ventricular repolarization. Twelve-lead electrocardiography and transthoracic echocardiography were performed just before surgery and at the nadir of postoperative weight loss. The corrected QT interval (QTc) was derived using Bazett's formula. QTc dispersion was calculated by subtracting the minimum from the maximum QTc on the 12-lead electrocardiogram. Echocardiographic left ventricular (LV) mass was indexed to height(2.7). The mean body mass index decreased from 42.8 ± 2.1 to 31.9 ± 2.2 kg/m(2) (p <0.0005). For the entire group, weight loss was associated with significant reductions in mean QTc (from 428.7 ± 18.5 to 410.5 ± 11.9 ms, p <0.0001) and mean QTc dispersion (from 44.1 ± 11.2 to 33.2 ± 3.3 ms, p <0.0005). Mean QTc and QTc dispersion decreased significantly with weight loss in patients with LV hypertrophy but not in subjects without LV hypertrophy. Multivariate analysis identified pre-weight loss LV mass/height(2.7) as the most important predictor of pre-weight loss QTc and QTc dispersion and also identified weight loss-induced change in LV mass/height(2.7) as the most important predictor of weight loss-induced changes in QTc and QTc dispersion. In conclusion, LV hypertrophy is a key determinant of QTc and QTc dispersion in normotensive morbidly obese patients. Regression of LV hypertrophy associated with weight loss decreases QTc and QTc dispersion.

Clustering of cardiovascular risk factors and relation with QTc dispersion, albuminuria and elevated alanine transaminase levels

Clustering of cardiovascular risk factors and relation with QTc dispersion, albuminuria and elevated alanine transaminase levels

QT Intervals in Patients Receiving a Renal Transplant

Cardiovascular disease is the most-common cause of mortality in patients with end-stage renal disease and renal transplant. Prolongation of QTc(max) and QTc dispersion are risk factors of cardiac arrhythmias and mortality. This study compares the changes of QT parameters before hemodialysis, after hemodialysis, and after renal transplant. Patient candidates for renal transplant were selected. Mean serum electrolyte and 12-lead electrocardiogram were recorded (1) immediately, (2) before and, (3) after the last dialysis session before renal transplant, (4) and 2 weeks after a kidney transplant in 34 patients with normal graft function (plasma Cr ≤ 176.8 μmol/L). Each QT interval was corrected for the patient's heart rate using Bazett's formula. The QT parameters (QTd, QTcd, QTc(max)) were compared between prehemodialysis, posthemodialysis, and 2 weeks after renal transplant using a paired t test and a general liner model repeated measure. The correlation between QT parameter changes and serum electrolyte and acidbase alternation was analyzed. The corrected maximal QT interval (QTc(max)) decreased significantly after successful renal transplant compared to prehemodialysis (P = .002) and posthemodialysis (P = .003) with a paired t test and a General Liner Model Repeated Measure (P < .001) between the 3 groups. Also, the mean of QTc(max) decreased significantly after renal transplant (P = .001) compared to what it was before hemodialysis and after hemodialysis. There was a significant correlation (r= -0.37) between reduction of QTc(max) and serum Ca level (P = .01) in postrenal transplant period. Renal transplant with normal graft function decrease QTc(max) compared to prehemodialysis and posthemodialysis that may correlate with normalization of electrolytes from the uremic state of the normal kidney function.

Relation of the metabolic syndrome with proarrhythmogenic electrocardiographic parameters in patients without overt diabetes

Objectives We aimed to observe the relationship of the metabolic syndrome and proarrythmogenic ECG parameters and to evaluate a possible correlation of these parameters to the metabolic syndrome score in patients without overt diabetes mellitus.Methods The study population consisted of 142 patients with the metabolic syndrome and 170 age-and gender-matched control subjects. In the ECG recordings, resting heart rate, QRS duration, corrected QT duration and corrected QT dispersion were measured. Patients were classifi ed into three groups based on number of fulfi lled metabolic syndrome criteria: group 1 (three metabolic syndrome criteria), group 2 (four metabolic syndrome criteria) and group 3 (fi ve metabolic syndrome criteria).Results Patients with the metabolic syndrome had a higher increased resting heart rate, QTcd, prolonged QRS and QTc duration. Resting heart rate increases signifi cantly parallel to the increase in the metabolic syndrome score across the groups, whilst QRS duration remained unchanged. QTc duration and QTc dispersion were signifi cantly higher in groups 2 and 3 when compared to group 1. However, no signifi cant diff erences were observed between groups 2 and 3.Conclusion We demonstrated that the metabolic syndrome and its score related with increased resting heart rate and prolonged repolarization durations in patiens without overt diabetes mellitus. These pro arrhythmogenic parameters could be used in the development of risk stratifi cation schemes for sudden cardiac death in patients with the metabolic syndrome.

Assessment of Cardiac Parameters in Evaluation of Cardiac Functions in Patients with Thalassemia Major

The aim of the study was to evaluate cardiac function and early cardiac dysfunction of patients followed as thalassemia major. In this study, the authors compared 100 patients, diagnosed as thalassemia major with mean age 11.84 ± 4.35, with 60 healthy control subjects at the same age between 2008 and 2011. Early diagnosis of iron overload that may occur after repeated transfusions is important in this patient group. To detect early iron accumulation, the authors compared ferritin with the echo findings, the 24-hour Holter, and cardiac magnetic resonance imaging (MRI) T2* values in the patients of same age and sex, treated with chelators, without heart failure, nonsplenectomized, and do not differ in the presence of hepatitis C. Ferritin levels, left ventricular systolic functions (ejection fraction [EF], shortening fraction [SF]), left ventricular measurements, left ventricular diastolic functions, T2* image on cardiac magnetic resonance, heart rate variables in 24 hours, and Holter rhythm were evaluated to show the early failure of cardiac functions. In this study the authors confirmed that iron-related cardiac toxicity damages electrical activity earlier than myocardial contractility. Left ventricular diastolic diameter (LVDd), left ventricular mass (LVM), and LV systolic diameter (LVDs) levels were significantly higher in the patient group with ectopia. Patients with ectopia are the ones in whom LVM and LVDd are increased. In thalassemia major patients with ectopia, LF/HF ratio was markedly increased, QTc dispersion was clearly found higher in patients with ectopia rather than nonectopic patients. The standard deviation all normal RR interval series (SDNN) was found clearly lower in thalassemia major group with ectopia than control group because it is assumed that increase in cardiac sympathetic neuronal activity is related to exposure to chronic diastolic and systolic failure.

Clinical and Electrocardiographic Evaluation of Sickle-Cell Anaemia Patients with Pulmonary Hypertension

Pulmonary hypertension is an emerging complication of sickle cell anaemia with associated increased risk of mortality. In order to evaluate the clinical and electrocardiographic findings in adult sickle-cell patients with pulmonary hypertension, a cross sectional study was conducted on sixty two sickle cell anaemia patients and sixty two age and sex matched normal controls. Elevated pulmonary artery pressures (PAP), defined by PAP ≥ 30 mm Hg on echocardiography, was demonstrated in 41.9% of patients with sickle cell anaemia and in 3.2% of the controls; χ 2 = 26.571, P < 0.001. Right ventricular hypertrophy, increased P-wave duration, QTc interval, and QTc dispersion were significantly associated with pulmonary hypertension. Significant correlation was found between mean PAP and (1) Frequency of crisis (Spearman correlation = 0.320; P = 0.011), (2) body mass index (Pearson's correlation = −0.297; P = 0.019), and (3) QTc interval (Pearson's correlation 0.261; P = 0.040). Pulmonary hypertension in adult sickle anaemia patients is associated with electrocardiographic evidence of right ventricular hypertrophy, and correlates significantly with frequency of vaso-occlusive crisis, and QTc interval. The observations by this study tend to suggest that these parameters could be useful for early detection and prevention of pulmonary hypertension in patients with sickle cell anaemia.

Influence of gender and types of sports training on QT variables in young elite athletes

Influence of gender and sports training on QT variables such as QT interval and dispersion (QT dispersion: QTD) in young elite athletes were evaluated. Subjects included 104 male and 97 female Japanese elite athletes (mean age 21.6 years). Sports included basketball, fencing, gymnastics, judo, swimming, tennis, track and field and volleyball. Age-matched healthy non-athletes (32 men and 20 women) were enrolled as controls. QT measurements were manually obtained from a 12-lead resting electrocardiogram and QTD was calculated as the difference between the longest and shortest QT intervals. A corrected QT interval (QTc) was obtained using Bazett's formula. Subjects were divided into two groups; an endurance training group and a static training group on the basis of their training types. Results: Maximum and minimum QTc were significantly longer in female athletes than in male athletes (max: 414.2 vs. 404.5 ms, min: 375.1 vs. 359.2 ms, p<0.0001 respectively), whereas QTc dispersion (QTcD) was shorter in female athletes than in male athletes (39.2 vs. 45.3 ms, p<0.0001). QTcD was significantly shorter in female athletes than in the female control group (39.2 vs. 45.2 ms, p<0.05). However, no statistically significant difference was observed between male athletes and the male control group. Male gymnasts exhibited significantly longer QTcD than the control group (p<0.01), but female gymnasts had significantly shorter QTcD than the control group (p<0.05). Maximum QTc intervals were prolonged in the male static training group compared with non-athletes, and QTcDs in the static training group were prolonged compared with the endurance training group. However, no significant difference was observed in the female group. In conclusion, both gender and different characteristics of sports training may affect QT variables even in young elite athletes. Vigorous static exercise training may independently prolong QT variables.

The Effect of Different Dialysate Magnesium Concentrations on QTc Dispersion in Hemodialysis Patients

Background: Electrolyte changes during dialysis affect corrected QT (QTc) and QTc dispersion (QTcd), a surrogate marker of arrhythmogenicity. The impact of magnesium on QTcd is not clear. Methods: Twenty-two stable patients on maintenance hemodialysis were enrolled in this study. Each underwent two consecutive hemodialysis sessions at least 2 days apart, the first against normal magnesium dialysate (with magnesium at 1.8 mg/dL) followed by a low magnesium dialysate (with magnesium at 0.6 mg/dL). Pre- and post-dialysis weights, blood pressure, electrolytes, and 12-lead surface EKG were recorded. The QT interval and the QTcd were calculated before and after dialysis in both sessions. Results: Of 22 patients, 16 were female. The mean age ± SD was 53.7 ± 18.0 years. The mean change of QTcd (pre- vs. post-dialysis) was 9.5 ms (p = 0.120) and 9.3 ms (p = 0.145) in low and normal magnesium groups, respectively. Using univariate analysis, there was a statistically significant decrease in the mean blood pressure, weight, potassium, magnesium, and QTc interval post-dialysis (compared to pre-dialysis) in both groups (p ≤ 0.049). Post-dialysis concentrations of sodium and calcium were unchanged (compared to pre-dialysis) but bicarbonate increased with both dialysate groups (p < 0.001). The mean change of QTcd was not significant pre- versus post-dialysis by univariate analysis in either group. Multiple linear regression analysis adjusting for pertinent factors did not change the results in either of the two groups. Conclusion: Using a low magnesium dialysate bath in hemodynamically stable hemodialysis patients without preexisting advanced cardiac disease does not significantly impact QTcd.

Electrocardiographic findings in sickle cell cardiovascular autonomic neuropathy

There is a lack of data on the relationship between cardiovascular autonomic neuropathy (CAN) and electrocardiographic parameters in sickle cell anaemia. The purpose of the study was to compare the electrocardiographic findings in adult sickle cell anaemia patients with CAN with those of patients without this complication. A cross sectional study was done using 62 consecutively recruited sickle cell anaemia patients who met the inclusion criteria for the study. Cardiovascular autonomic dysfunction was determined based on abnormal values in at least two of five non-invasive tests: Valsalva manoeuver, heart rate variation during deep breathing, heart rate response to standing, blood pressure response to sustained hand grip, and blood pressure response to standing. The subjects were subsequently evaluated with electrocardiography. Sickle cell anaemia patients with CAN had statistically significantly increased P-wave duration (p < 0.001), PR-interval (p < 0.05) and QTc dispersion (p < 0.05) compared with patients without CAN. Significantly increased frequencies of Q waves and first degree atrio-ventricular block were found in patients with CAN than in those without CAN (p = 0.026, p = 0.014, respectively). Significant correlations were noted between the severity of CAN [number of abnormal autonomic function tests (AFT)] and (1) P-wave duration (p = 0.008), (2) PR- interval (p = 0.013). Significant association was found between the number of abnormal AFT and (1) presence of Q-waves, and (2) degree of anaemia (haematocrit class). Electrocardiographic features consistent with atrio-ventricular and ventricular repolarization abnormalities are associated with CAN in sickle cell anaemia. Further studies are required to evaluate the prognostic implications of these findings in sickle cell patients with cardiovascular autonomic dysfunction.

Usability of QTc dispersion for the prediction of orthostatic intolerance syndromes

BackgroundSyncope is defined as transient loss of consciousness and muscle tone, usually of short duration. Noncardiac causes of syncope are classified as orthostatic intolerance syndromes (OIS). QT and QTc (corrected QT) dispersions are the measurements of myocardial instability and show predisposition to arrhythmias. In this study; clinical findings, QT and QTc dispersions of the patients who were diagnosed as OIS were evaluated retrospectively. Also, the aim of the study is to clarify the association of clinical characteristics of unexplained syncope with the outcome of the QT and QTc dispersions in children. MethodsWe designed a retrospective study including 152 children and adolescents who had repeated unexplained syncope or presyncope between June 2002 and August 2010. Head-up Tilt table test (HUTT) were performed for all patients. Control group consisted of 67 healthy children. The QT and QTc dispersions were measured from the 12 ECG leads. ResultsEighty-four (55.2%) patients had positive and 68 (44.8%) had negative response to HUTT. QT and QTc dispersions were significantly higher in HUTT-positive group than in negative (p < 0.01, p < 0.001 respectively). Also, QTc dispersion was significantly higher in both vasovagal syncope and postural orthostatic tachycardia syndrome groups than in HUTT-negative group (p < 0.001, p < 0.05 respectively). Specifity and sensitivity of QTc dispersion for predicting positive HUTT are 76.5% and 59.5% respectively. The positive predictive value of the test calculated as 75.8%. ConclusionsThese results revealed that we can use QTc dispersion measurement as a noninvasive electrocardiographic test to evaluate OIS for predicting positive result before performing HUTT.

Disturbances of QT interval in patients with diabetic autonomic neuropathy

Introduction. Autonomic neuropathy in diabetes, being insufficiently clinically defined, is related to numerous clinical syndromes. The aim of the study was to establish the relationships between autonomic neuropathy in diabetes and QT interval disturbances in our diabetic patients group, as well as the sensitivity of certain cardiovascular tests in detection of pathologic QT dispersion. Method. 100 diabetic patients, among whom there were equal numbers of patients with type 1 and type 2 diabetes, as well as 20 healthy persons in the control group, were included in the study. Ewing cardiovascular tests were used for diagnosis of autonomic neuropathy in diabetes. In standard 12-lead ECG, QTc mean, QTc maximal, QTc minimal and QTc dispersion (difference between QTc maximal and QTc minimal) were determined. QTc dispersion higher than 43 mS was considered abnormal. Methods of descriptive statistics and hypothesis testing were used to process the data Results. There was a positive correlation between autonomic neuropathy in diabetes and QTc maximal, QTc mean and QTc dispersion. No correlation was observed between QTc dispersion and the tests assessing parasympathetic part of the autonomous nervous system. On the other hand, there was a certain relation between pathologic QT dispersion and orthostatic hypotension test. Conclusion. The tests used in this study, due to their simplicity and reliability, could be utilized in detecting patients with pathologic values of QTc dispersion within the clinical practice settings.

Increased dispersion of ventricular repolarization in emery dreifuss muscular dystrophy patients

SummaryBackgroundSudden cardiac death (SCD) is common in patients with Emery-Dreifuss muscular dystrophy (EDMD) and is attributed to the development of life-threatening arrhythmias that occur in the presence of normal left ventricular systolic function. Heterogeneity of ventricular repolarization is considered to provide an electrophysiological substrate for malignant arrhythmias. QTc dispersion (QTc-D) and JTc dispersion (JTc-D) are electrocardiographic parameters indicative of heterogeneity of ventricular repolarization. The aim of our study was to evaluate the heterogeneity of ventricular repolarization in patients with Emery-Dreifuss muscular dystrophy with preserved systolic and diastolic cardiac functionMaterial/MethodsThe study involved 36 EDMD patients (age 20±12, 26 M) and 36 healthy subjects used as controls, matched for age and sex. Heart rate, QRS duration, maximum and minimum QT and JT interval, QTc-D and JTc-D measurements were performed.ResultsCompared to the healthy control group, the EDMD group presented increased values of QTc-D (82.7±44.2 vs. 53.1±13.7; P=0,003) and JTc-D (73.6±32.3 vs. 60.4±11.1 ms; P=0.001). No correlation between QTc dispersion and ejection fraction (R=0.2, P=0.3) was found.ConclusionsOur study showed a significant increase of QTc-D and JTc-D in Emery-Dreifuss muscular dystrophy patients with preserved systolic and diastolic cardiac function.

A mouse model to study the link between hypoxia, long QT interval and sudden infant death syndrome

SUMMARYThe pathology of sudden infant death syndrome (SIDS) is poorly understood. Many risk factors, including hypoxia, have been identified. Prolongation of the ECG QTc interval is associated with elevated risk of SIDS but its aetiology in most cases remains unknown. We have characterised ECG changes in the newborn mouse in the hours and days following birth. There was a steady increase in heart rate alongside significant decreases in QTc interval, QRS duration and QTc dispersion over the first 10 postnatal days. Birth into hypoxia (10% FiO2) prevented electrocardiac maturation, downregulated cardiac ion-channel expression and led to neonatal death. We found that risk of death decreased with increasing age of exposure to hypoxia. Genetic elevation of cardiac hypoxia-signalling after birth in αMHC-Cre::VHLfl/fl mice also prevented electrocardiographic maturation, leading to arrhythmia and death before weaning. Immunohistochemistry and western blotting revealed internalisation and dephosphorylation of Connexin43. We conclude that increased ambient oxygen concentration after birth drives maturation of the cardiac electrical conduction system, failure of which leads to aberrant ion channel and Connexin43 expression and predisposes to arrhythmia and sudden death. This is consistent with known risk factors of SIDS and provides a link between neonatal hypoxia, ECG abnormalities and sudden death.