Difference In QT Interval Research Articles

The QT interval in Parkinson's disease: a systematic review.

PD (PD) is associated with a twofold increase in the risk of death especially sudden death. A predisposing factor for cardiac sudden death is prolongation of the QT interval. This study evaluated the potential association between QT interval and PD. A systematic search was conducted of Medline and EMBASE using the search terms "PD" AND "QT interval" OR "Cardiac Repolarization" to identify articles. Seven studies with persons with PD (n = 981) and control groups were identified. There was a significant difference in QT interval comparing patients with PD and persons without PD. The odds ratio showed a significant (P < 0.001) 2.6-fold (random effect) greater QTc prolongation in PD compared to control. Overall, there was a significantly longer QT in patients with PD than controls of 10.7 ± 2.8 ms. Data analysis did not show much publication bias. Focusing only on studies that related the QT interval to the severity of PD as assessed by Hoehn-Yahr classification (n = 6), there was a significant (P = 0.004) overall correlation between QT interval and the severity of PD. There was little publication bias. The data directly examining patients with PD taking any drug than might prolong QT do not support an association between these mediations and QT prolongation. Individuals with PD have a longer QT interval than individuals without PD. The QT interval is associated with a greater severity of PD and a greater probability of developing more severe PD. The QT interval should be considered in assessment of PD and possibly as a target for the treatment of PD.

Cardiovascular safety of pimitespib in patients with advanced solid tumors: An open-label, nonrandomized, phase 1 study.

Pimitespib (TAS-116), a first-in-class, oral, selective heat-shock protein 90 inhibitor, is approved as fourth-line treatment for gastrointestinal stromal tumors in Japan. This phase 1 study evaluated the cardiac safety of pimitespib. In this open-label, nonrandomized, multicenter study, Japanese patients (aged ≥20 years) with refractory, advanced solid tumors received placebo on day -1, then pimitespib 160 mg daily on days 1-5 of the cardiac safety evaluation period. Electrocardiograms were conducted at baseline, and on days -2, -1, 1, and 5; and blood samples were collected on days 1 and 5. Patients then received once-daily pimitespib for 5 days every 3 weeks. The primary end point was the time-matched difference in QT interval corrected for heart rate using the Fridericia correction (QTcF) between pimitespib and placebo. Pharmacokinetics, safety, and preliminary efficacy were also assessed. Of the 22 patients in the cardiac safety-evaluable population, no clinically relevant QTc prolongation was observed; the upper bound of the one-sided 95% confidence interval for the time-matched difference in change from baseline in QTcF was <20 msec at all time points on days 1 and 5. Pimitespib pharmacokinetic parameters were consistent with previous data, and the time-matched difference in change from baseline in QTcF showed no marked increase as plasma concentrations increased. The safety profile was acceptable; 40% of patients experienced grade 3 or greater adverse drug reactions, mostly diarrhea (20%). The median progression-free survival was 3.1 months. In Japanese patients with refractory, advanced solid tumors, pimitespib was not associated with clinically relevant QTc prolongation, and there were no cardiovascular safety concerns. Pimitespib is a new anticancer drug that is being used to treat cancer in the stomach or intestines (gastrointestinal stromal tumors). This study demonstrated that pimitespib had no marked effect on heart rhythm or negative effects on the heart or blood vessels and had promising anticancer effects in Japanese patients with advanced solid tumors who were unable to tolerate or benefit from standard treatment.

Relationship between Alzheimer dementia and QT interval: A meta-analysis.

While the link between aging and mortality from dementia is widely appreciated, the mechanism is not clear. The objective of this study was to determine whether there is a direct relationship between Alzheimer dementia (AD) and the QT interval, because the latter has been related to cardiac mortality. A systematic review and meta-analysis were conducted after a Medline and EMBASE search using terms "Alzheimer disease or Dementia AND QT interval, QT dispersion or cardiac repolarization." Four studies with control groups were identified. There were significant differences in QT interval between individuals with AD vs individuals without dementia (controls) (odds ratio (OR)1.665 [random effects model] and 1.879 [fixed effect model]) (p < 0.001). There were significant differences in QT interval between individuals with AD vs individuals with mild cognitive impairment (MCI) (OR 1.760 [random effects] and 1.810 [fixed effect]) (p < 0.001). A significant (p <0.001) correlation exists between the QTc and the Mini-Mental State Exam (MMSE), a test of cognitive function. Two studies examined QT variability (the difference between the longest and shortest QT interval on a 12 lead ECG); the OR for QT variability AD vs MCI was 3.858 [random effects model] and 3.712 [fixed effects model] (p < 0.001). When compared to the control group, the OR for QT dispersion in AD was 6.358 [random effects model] or 5.143 ( P< 0.001) [fixed effects model]. A qualitative analysis of the data raised questions about paucity of data defining the nature of the control groups, the pathophysiologic mechanism, and the uniform use of a poor QT heart rate correction factor. The longer QT in AD, greater QT variability in AD, and the direct relationship between QT interval and AD severity supports a brain-heart connection in AD that might be fundamental to aging-induced AD and mortality. Issues with defining the control group, limited number of studies, conflicting data in population studies, and the lack of a strong electrophysiological basis underscore the need for additional research in this field.

Testosterone does not shorten action potential duration in Langendorff-perfused rabbit ventricles.

Women have longer baseline QT intervals than men. Because previous studies showed that testosterone and 5α-dihydrotestosterone shorten the ventricular action potential duration (APD) in animal models, differential testosterone concentrations may account for the sex differences in QT interval. The purpose of this study was to test the hypothesis that testosterone shortens the APD in Langendorff-perfused rabbit ventricles. We performed optical mapping studies in hearts with or without testosterone administration. Acute studies included 26 hearts using 2 different protocols, including 17 without and 9 with atrioventricular (AV) block. For chronic studies, we implanted testosterone pellets subcutaneously in 7 female rabbits for 2-3 weeks before optical mapping studies during complete AV block. Six rabbits without pellet implantation served as controls. The hearts in the acute studies were paced with a pacing cycle length (PCL) of 200-300 ms and mapped at baseline and after administration of 1 nM, 10 nM, 100 nM, and 3 μM of testosterone. There was no shortening of APD80 at any PCL. Instead, a lengthening of APD80 was noted at higher concentrations. There were no sex differences in testosterone responses. In chronic studies, heart rates were 136 ± 5 bpm before and 148 ± 9 bpm after (P = .10) while QTc intervals were 314 ± 9 ms before and 317 ± 99 ms after (P= .69) testosterone pellet implantation, respectively. Overall, ventricular APD80 in the pellet group was longer than in the control group at 300- to 700-ms PCL. Testosterone does not shorten ventricular repolarization in rabbit hearts.

Manual QT interval measurement with a smartphone-operated single-lead ECG versus 12-lead ECG: a within-patient diagnostic validation study in primary care

ObjectiveTo determine the accuracy of QT measurement in a smartphone-operated, single-lead ECG (1L-ECG) device (AliveCor KardiaMobile 1L).DesignCross-sectional, within-patient diagnostic validation study.Setting/participantsPatients underwent a 12-lead ECG (12L-ECG) for any non-acute indication...

The Changes of T-Wave Amplitude and QT Interval Between the Supine and Orthostatic Electrocardiogram in Children With Dilated Cardiomyopathy.

Objectives: Electrocardiogram (ECG) can be affected by autonomic nerves with body position changes. The study aims to explore the ECG changes of children with dilated cardiomyopathy (DCM) when their posture changes.Materials and methods: Sixty-four children diagnosed with DCM were recruited as research group and 55 healthy children as control group. T-wave amplitude and QT interval in ECG were recorded, and their differences between supine and orthostatic ECG were compared in both groups. Subsequently, the children with DCM were followed up and the differences before and after treatment compared.Results: ① Comparisons in differences: Differences of T-wave amplitude in lead II and III, aVF, and V5 and differences of QT interval in lead II, aVL, aVF, and V5 were lower in the research group than in the control group. ② Logistic regression analysis and diagnostic test evaluation: The differences of T-wave amplitude in lead III and QT interval in lead aVL may have predictive value for DCM diagnosis. When their values were 0.00 mV and 30 ms, respectively, the sensitivity and specificity of the combined index were 37.5 and 83.6%. ③ Follow-up: In the response group, the T-wave amplitude difference in lead aVR increased and the difference of QT interval in lead V6 decreased after treatment. In the non-response group, there was no difference before and after treatment. When the combined index of the differences of T-wave amplitude difference in lead aVR and QT interval difference in lead V6, respectively, were −0.05 mV and 5 ms, the sensitivity and specificity of estimating the prognosis of DCM were 44.4 and 83.3%.Conclusions: The differences of T-wave amplitude and QT interval may have a certain value to estimate DCM diagnosis and prognosis.

DOES PHYSIOLOGIC CARDIAC REMODELING IN ENDURANCE ATHLETES ALTER REPOLARIZATION OR QT DYNAMICS?

Increases in QT and QTc duration, and their alterations with changes in heart rate, are associated with dysrhythmias and increased sudden death rates in population studies. Long standing endurance sport is associated with reduced cardiac mortality. Endurance athletes are known to develop physiologic LV remodeling concomitant with increases in LV mass, which may be associated with QT prolongation. However, QT dynamics in middle-aged athletes has not been studied extensively. We sought to compare the QT interval at rest and during exercise in healthy middle-aged adults with and without a history of long-standing endurance exercise. Healthy participants on no medications, between 45-65 years old (>10 years of regular physical activity participation) were recruited, and underwent physical examination. Eligible participants, including 86 endurance athletes (EA) and 24 recreationally-active (RA) adults, had a resting baseline 12-lead ECG and a standardized graded exercise testing with a 12-lead ECG taken every 1-2 minutes during exercise until exhaustion. QT intervals were measured as the longest QT in anterior precordial lead or lead 2 by two investigators and discrepancies resolved by consensus; QT intervals were corrected for rate using Bazett’s formula (QTc=QT/√RR in sec). Seventy-five participants also had a resting cardiac magnetic resonance to evaluate cardiac structure and physiological remodeling related to exercise. Participant demographics and ECG characteristics are summarized in Table 1. The higher cardiorespiratory fitness (VO2max) and left-ventricular mass reflected normal physiological adaptation to endurance exercise training. While mean resting QT interval was longer in EA vs. RA, there was no difference when QT interval was corrected for heart rate (QTc). The QT and QTc slopes (linear relationship of QT vs. RR and QTc vs. RR during exercise) were not different between EA and RA. Among long-standing middle-aged athletes with normal physiologic remodeling, there is no difference in QT intervals in EA vs. RA when corrected for their lower resting heart rate. Despite physiologic LV remodelling, chronic endurance exercise training is associated with normal repolarization at rest and during exercise among middle-aged endurance athletes.

Does the Magnitude of the Electrocardiogram QT Interval Dispersion Predict Stroke Outcome?

BackgroundQT dispersion, maximal interlead difference in QT interval on 12-lead electrocardiogram (ECG), measures cardiac repolarization abnormalities. Data are conflicting whether QT dispersion predicts adverse outcome in acute ischemic stroke (AIS) patients. Our objective is to determine if QT dispersion predicts: (1) short-term clinical outcome in AIS, and (2) stroke location (insular versus noninsular cortex). MethodsAdmission ECGs from 412 consecutive patients with acute stroke symptoms from 2 university-based stroke centers were reviewed. QT dispersion was measured. A neuroradiologist reviewed brain imaging for insular cortex involvement. Favorable clinical outcomes at discharge were modified Rankin Scale (mRS) score of 0-1, discharge National Institutes of Health Stroke Scale (NIHSS) score less than 2, and discharge to home. Multiple logistic regressions were performed for each outcome measure and to determine the association between insular infarct and QT dispersion. ResultsOf 145 subjects in the final analysis, median age was 65 years (interquartile range [IQR] 56-75), male patients were 38%, black patients were 68%, median QT dispersion was 78 milliseconds (IQR 59-98), and median admission NIHSS score was 4 (IQR 2-6). QT dispersion did not predict short-term clinical outcome for mRS score (odds ratio [OR] = 1.001, 95% confidence interval [CI] .99-1.01, P = .85), NIHSS at discharge (OR = .994, 95% CI .98-1.01, P = .30), or discharge disposition (OR = 1.001, 95% CI .99-1.01, P = .81). Insular cortex involvement did not correlate with QT dispersion magnitude (OR = 1.009, 95% CI .99-1.02, P = .45). ConclusionsWe could not demonstrate that QT dispersion is useful in predicting short-term clinical outcome at discharge in AIS. Further, the magnitude of QT dispersion did not predict insular cortical stroke location.

Liver cirrhosis-effect on QT interval and cardiac autonomic nervous system activity.

AIMTo examine the impact of liver cirrhosis on QT interval and cardiac autonomic neuropathy (CAN).METHODSA total of 51 patients with cirrhosis and 51 controls were examined. Standard 12-lead electrocardiogram recordings were obtained and QT as well as corrected QT interval (QTc) and their dispersions (dQT, dQTc) were measured and calculated using a computer-based program. The diagnosis of CAN was based upon the battery of the tests proposed by Ewing and Clarke and the consensus statements of the American Diabetes Association. CAN was diagnosed when two out of the four classical Ewing tests were abnormal.RESULTSQT, QTc and their dispersions were significantly longer (P < 0.01) in patients with cirrhosis than in controls. No significant differences in QT interval were found among the subgroups according to the etiology of cirrhosis. Multivariate regression analysis after controlling for age, gender and duration of cirrhosis demonstrated significant association between QT and presence of diabetes mellitus [standardized regression coefficient (beta) = 0.45, P = 0.02] and treatment with diuretics (beta = 0.55, P = 0.03), but not with the Child-Pugh score (P = 0.54). Prevalence of CAN was common (54.9%) among patients with cirrhosis and its severity was associated with the Child-Pugh score (r = 0.33, P = 0.02). Moreover, patients with decompensated cirrhosis had more severe CAN that those with compensated cirrhosis (P = 0.03). No significant association was found between severity of CAN and QT interval duration.CONCLUSIONPatients with cirrhosis have QT prolongation. Treatment with diuretics is associated with longer QT. CAN is common in patients with cirrhosis and its severity is associated with severity of the disease.

THE EFFECTS OF SEDATIVE AGENTS USED IN INTENSIVE CARE UNIT ON QT INTERVAL

ABSTRACT Objective: The aim of this research is the effects of sedative drugs which are used on intensive care unit (ICU) patients on QT interval. Materials and Methods: After ethics committee and patient’s relative’s approval, 90 patients who are age of 30-90 hospitalized at ICU due to respiratory insufficiency and connected to mechanic ventilator. Only patients that have sedative requirement were included in this research. Patients that have instabil hemodynamia, acquired or congenital long QT syndrome, electrolyte imbalance and patients that have anticholinergic, antiarythmic, vasopressor, vasodilatator and hypotensive drug treatments were not included in the research. Also, patients that haven’t the relative’s approval were not included in the research. Patients that have conscious changes, hemodynamic instability, endotracheal tube changing requirement, anticholinergic, antiarythmic, vasopressor and vasodilatator drug requirement during the research were removed from the research. After the respiratory and cardiac monitorizations were enabled on patient with respiratory insufficiency in ICU, 12 derivations ECG’s were recorded, systolic blood pressure (SBP), diastolic blood pressure(DBP), mean arterial blood pressure(MABP), heart rate(HR) and peripheric oxygen saturation (SpO2) values were recorded simultaneously. These values were used as base. At 1st and 12th hours of sedation (midazolam, propofol or dexmedetomidin), 12 derivations ECG’s were recorded and again, SBP, DBP, MABP, HR and SpO2 values were recorded. ECG’s were recorded at the speed of 25mm/s and at the height of 1 mV. Among the derivations in ECG recordings, the longest QT interval was measured by 2 anesthesiologists who don’t know the groups and by measuring the RR interval on the same derivation, QTc (corrected QT) interval was measured with Bazzet formula .(QTc=QT intervali / √ RR interval) .Measured QT and QTc values were recorded. Results: Among the groups, there was no difference in terms of age, Glasgow Coma Scale and sex. (p>0,05). When the effect of sedation type on HR, MABP and SpO2 was investigated, there was no significant difference in terms of HR, MABP, SpO2 at 0th and 1st hours among different sedative drugs (p>0,05). When HR’s at 12th hour were evaluated, HR at dexmedetomidin group was lower than both midazolam and propofol groups’ HR and this was statistically significant (p 0,05). For QT interval; dexmedetomidin prolonged the interval more than the other 2 agents both at 1st and 12th hours and this was statistically significant (p<0,05). There was statistically significant difference in QT intervals between propofol and midazolam groups at 12th hours (p<0,05). When QTc intervals were evaluated; only QTc values at 12th hour were different between different sedative agents and the QTc values in these groups belong to these different sedative agents were different each other and this was statistically different (p<0,05). Dexmedetomidin prolonged QTc mostly however propofol shows favorable efficacy by shortening the QTc interval. Conclusion: Monitorization is necessary for using sedative agents in ICU because these agents can cause cardiac and respiratory changes. Dexmedetomidin is superior to propofol because it causes less hypotension. In our opinion, propofol is a good alternative sedative agent for dexmedetomidin and midazolam in patients with long QT interval because it shortens the QT interval however dexmedetomidin and midazolam can cause cardiac arrhythmia by prolonging QT interval. When making drug choice for sedation in ICU, patient’s clinical situation, hemodynamic parameters and cardiac monitorization must be considered. Keywords: Propofol, midazolam, dexmedetomidine, sedation, QT interval.

Low-Moderate Arsenic Exposure and QT Interval: the Strong Heart Study

Introduction: The etiology of arsenic-related cardiovascular disease is uncertain. A previous study of arsenic at high levels of arsenic in drinking water and QT interval found an association limited to women, while a study among elderly men found an association at low arsenic levels. Methods: We evaluated the association between arsenic exposure and QT interval in adult men and women from the original Strong Heart Study (baseline 1989-91; mean age 54 y, N=1673) and its ancillary family study (baseline 1998-03; mean age 33 y, N=2313 diabetes-free only). We measured arsenic exposure in urine (sum of inorganic and methylated metabolites) and divided by creatinine. QT interval was measured in resting 12-lead electrocardiograms with Bazett’s heart rate correction. We estimated the adjusted difference in QT interval by urine arsenic levels (modeled as quartiles and restricted cubic splines). Results: The medians of arsenic and QT interval were 9.6 µg/g creatinine and 427 ms in the original cohort and 4.8 µg/g and 414 ms in the family study. In the original cohort, the adjusted difference (95% CI) in QT interval comparing the highest to the lowest arsenic quartile was 9.3 (3.9, 14.9) ms in men and 4.8 (-0.4, 10.1) ms in women. In the family study, the corresponding difference in QT interval was 2.0 (-1.5, 5.5) ms in men and 4.3 (1.2, 7.5) ms in women. Conclusions: Low-moderate arsenic exposure was associated with higher QT interval with similar associations in both cohorts for women and a stronger association for men in the original cohort.

Increased iron stores prolong the QT interval - a general population study including 20261 individuals and meta-analysis of thalassaemia major.

The prolongation of cardiac repolarization (QT interval) has been investigated in studies of patients with secondary iron overload. However, no previous population-based study examining the effect of increased iron stores on QT interval prolongation has previously been undertaken. We tested the hypothesis that increased iron stores and haemochromatosis genotype (genetically increased iron stores) are associated with prolongation of the QT interval. We included 20261 individuals from the Danish General Suburban Population Study and examined differences in QT interval according to ferritin concentration, transferrin saturation, iron concentration, transferrin concentration and haemochromatosis genotype (C282Y/C282Y). Furthermore, we performed a meta-analysis of case-control studies on thalassaemia major patients and QT interval. Age- and C-reactive protein-adjusted mean corrected QT (QTc) intervals for ferritin concentration ≥99% vs. ≥25-<50% percentile were 418·9ms vs. 412·7ms in men (P<0·001) and 422·4ms vs. 419·1ms in women (P=0·78). Corresponding values for transferrin saturation were 417·6ms vs. 412·6ms in men (P=0·02) and 421·5ms vs. 419·4ms in women (P=0·86). The associations were not explained by inflammation and haemochromatosis genotype was not associated with QT interval length. In conclusion, increased iron stores, independent of haemochromatosis genotype and inflammation, are associated with prolongation of the QTc interval in men. This is a novel finding. In addition, the meta-analysis showed prolonged QT interval in thalassaemia major patients compared to healthy controls.

Differences in the electrocardiographic QT interval of various breeds of athletic horses during rest and exercise

ObjectivesQuantitative measurements of cardiac repolarization, defined as the electrocardiographic QT interval, have important diagnostic implications in humans, as irregularities can trigger potentially fatal ventricular tachyarrhythmia. In both humans and horses, cardiac repolarization is influenced to some extent by heart rate, age, body weight (BW), sex, autonomic tone, and environment. In horses, there is substantial inter-breed variation in size and training, and the aims of this study were therefore to determine the best model describing the QT to RR relationship in breeds of various athletic horses and to test for differences in the QT interval. AnimalsTen Icelandic horses, 10 Arabian horses, 10 Thoroughbreds, 10 Standardbreds, six Coldblood trotters, 10 Warmbloods (dressage) and 10 Warmbloods (show jumping). All horses were geldings. MethodsQT intervals were measured from resting to peak exercise level and plotted against RR intervals. Data points were fitted with relevant regression models, and the effect of breed, BW, and estimated exercise intensity was examined. ResultsFor all breeds in this study, the QT interval was best described as a function of RR by the piecewise linear regression model. The breed of horse had a significant effect on the model. There was no systematic effect of BW or estimated exercise intensity, but a high inter-horse variability was observed. ConclusionsThe equine QT interval should preferably be corrected for heart rate according to breed. In addition, the results indicate that equine studies of the QT interval must be designed to eliminate the influence of a large inter-horse variation.

Effect of metabolic acidosis on QT intervals in patients with chronic kidney disease.

There is a strong association between chronic kidney disease (CKD) and cardiovascular events. Increased arrhythmia risk in kidney disease is one of the main predominant factors in increased mortality and sudden cardiac death. To estimate this risk, noninvasive measurement of repolarization abnormalities including QT interval and its heart rate-corrected value (QTc) with surface ECG, are commonly used parameters in clinical practice. The aim of this study is to examine the effect of CKD-related problems - mainly acidosis - on QT intervals. 30 patients with stage 3-5 CKD whose serum bicarbonate concentrations below 20 mmol/L were included in the study. Alkali therapy with oral sodium bicarbonate was used to maintain the serum bicarbonate concentration in the normal range. At the beginning all patients had sinus rhythm on surface ECG records. Kidney function tests including serum urea, serum creatinine, uric acid, blood gas analysis, and electrolytes were analyzed at the beginning and at the end of alkali treatment. All patients underwent 12 lead-ECGs, recorded simultaneously. One cardiologist examined the ECGs manually in terms of QT intervals, corrected for heart rate (QTc), QT dispersion (QTd) and corrected QT dispersion (QTcd). There were statistically significant differences in QT intervals, QTc, QTd and QTcd before and after sodium bicarbonate treatment. The correlation analyses revealed that there were significant negative correlations in pretreatment ECGs of patients between QTd and QTcd with blood pH level. Multivariate analyses between biochemical parameters and QTd-QTcd intervals have revealed that pH was related to QTd and QTc. This study demonstrated that QT intervals on surface ECG are decreased after treatment of acidosis in CKD. Further studies are needed to show whether increased QT intervals cause ventricular arrhythmias in CKD.

Sex differences in the mechanisms underlying long QT syndrome

Sexual dimorphism is a well-established phenomenon, but its degree varies tremendously among species. Since the early days of Einthoven's development of the three-lead galvanometer ECG, we have known there are marked differences in QT intervals of men and women. It required over a century to appreciate the profound implications of sex-based electrophysiological differences in QT interval on the panoply of sex differences with respect to arrhythmia risk, drug sensitivity, and treatment modalities. Little is known about the fundamental mechanism responsible for sex differences in electrical substrate of the human heart, in large part due to the lack of tissue availability. Animal models are an important research tool, but species differences in the sexual dimorphism of the QT interval, the ionic currents underlying the cardiac repolarization, and effects of sex steroids make it difficult to interpolate animal to human sex differences. In addition, in some species, different strains of the same animal model yield conflicting data. Each model has its strengths, such as ease of genetic manipulation in mice or size in dogs. However, many animals do not reproduce the sexual dimorphism of QT seen in humans. To match sex linked prolongation of QT interval and arrhythmogenic phenotype, the current data suggest that the rabbit may be best suited to provide insight into sex differences in humans. In the future, emerging technologies such as induced pluripotent stem cell derived cardiac myocyte systems may offer the opportunity to study sex differences in a controlled hormonal situation in the context of a sex specific human model system.

ECG QT interval in mitral valve prolapse syndrome patients in Taiwan

Introduction: Until recently, there has been no study to assess the difference of QT interval between patients with mitral valve prolapse syndrome (MVPS) and normal Taiwanese. The QT interval is dependent on the heart rate (the faster the heart rate the shorter the QT interval) and corrected QT (QTc) can be easily calculated by computer-based ECG machines to improve the detection of ventricular arrhythmia(VA) and Sudden Cardiac Death (SCD). Different correction formulae such as Bazett, Fridericia, Framingham, Hodges etc have been adopted. MVPS has been reported to produce significantly more repolarization abnormalities and VA than normal. The aim of this study was to evaluate whether there was any differences in QT between MVPS and normal Taiwanese.

Gender differences of heart rate variability between symptomatic mitral valve prolapse syndrome and normal Taiwanese

Introduction: Until recently, there has been no study to assess the difference of QT interval between patients with mitral valve prolapse syndrome (MVPS) and normal Taiwanese. The QT interval is dependent on the heart rate (the faster the heart rate the shorter the QT interval) and corrected QT (QTc) can be easily calculated by computer-based ECG machines to improve the detection of ventricular arrhythmia(VA) and Sudden Cardiac Death (SCD). Different correction formulae such as Bazett, Fridericia, Framingham, Hodges etc have been adopted. MVPS has been reported to produce significantly more repolarization abnormalities and VA than normal. The aim of this study was to evaluate whether there was any differences in QT between MVPS and normal Taiwanese.

Choice of an alternative lead for QT interval measurement in serial ECGs when Lead II is not suitable for analysis

IntroductionConventionally, QT interval is measured in lead II. There are no data to select an alternative lead for QT measurement when it cannot be measured in Lead II for any reason. Methods and resultsWe retrospectively analyzed ECGs from 1906 healthy volunteers from 41 phase I studies. QT interval was measured on the median beat in all 12 leads. The mean difference in QT interval between lead aVR and in Lead II was the least, followed by aVF, V5, V6 and V4; lead aVL had maximum difference. The T wave was flat (<0.1 mV) in Lead II in 6.9% of ECGs; it was also flat in 20% of these ECGs (1.4% of all ECGs) in Leads aVR, aVF and V5. ConclusionsWhen QT interval cannot be measured in Lead II, the best alternative leads are aVR, aVF, V5, V6 and V4 in that sequence. It differs maximally from that in Lead II in Lead aVL.

Gender difference in QT interval in patients with primary aldosteronism

We assessed whether QT interval was still different between male and female patients with primary aldosteronism. We also assessed the gender difference in the relation between serum potassium level and QT interval. The study population consisted of 80 patients with newly diagnosed primary aldosteronism. There were 39 male and 41 female patients. There were no significant (ns) differences in serum potassium (3.6±0.7 mEq/l vs 3.8±0.5mEq/l, p=ns) and QTc interval (423±26 msec vs 427±23 msec, p=ns) between male and female patients. In overall patients, serum potassium level was inversely associated with QTc interval significantly (r=-0.36, p<0.01). In male patients, there was still a significant inverse correlation (r=-0.42, p<0.01). However, this correlation was lost in female patients (r=-0.30, p=ns). Our data suggested that QTc interval was inversely associated with serum potassium level in male patients, but was not in female patients with primary aldosteronism.

QT wave dispersion in patients with panic disorder

QT dispersion (QTd), defined as the maximal inter-lead difference in QT intervals on 12 leads of the surface electrocardiogram (ECG), reflects the regional heterogeneity of ventricular repolarization and has been suggested as an important marker for risk of arrhythmia in addition to the QT interval. Some investigators proposed that it might be a predisposing factor for arrhythmic events and sudden death. Thus, we aimed to investigate whether QTd differs in patients with panic disorder from that in healthy controls. In 40 panic disorder patients and 40 healthy controls, Q(max), Q(min), and QTd values were measured. In addition, the Hamilton depression rating scale and the panic agoraphobia scale were scored for both patients and healthy volunteers. Q(max) and Q(min) values in the panic disorder patients were significantly higher than those in healthy controls. The mean corrected QTd was significantly greater in the patients than in the controls. One-way analysis of covariance (ANCOVA; using left atrial size, age and heart rate as covariates) also corrected the significant difference. In addition, ANCOVA revealed a significant main effect for the diagnosis, indicating a significantly higher QTd for patients compared with controls. QTd might be associated with panic disorder. Future studies in larger samples evaluating the effects of treatment are required.