Maximum QT Research Articles

The phenomenon of “QT stunning”: The abnormal QT prolongation provoked by standing persists even as the heart rate returns to normal in patients with long QT syndrome

Patients with long QT syndrome (LQTS) have inadequate shortening of the QT interval in response to the sudden heart rate accelerations provoked by standing-a phenomenon of diagnostic value. We now validate our original observations in a cohort twice as large. We also describe that this abnormal QT-interval response persists as the heart rate acceleration returns to baseline. To describe a novel observation, termed "QT stunning" and to validate previous observations regarding the "QT-stretching" phenomenon in patients with LQTS by using our recently described "standing test." The electrocardiograms of 108 patients with LQTS and 112 healthy subjects were recorded in the supine position. Subjects were then instructed to stand up quickly and remain standing for 5 minutes during continuous electrocardiographic recording. The corrected QT interval was measured at baseline (QTc(base)), when heart rate acceleration without appropriate QT-interval shortening leads to maximal QT stretching (QTc(stretch)) and upon return of heart rate to baseline (QTc(return)). QTc(stretch) lengthened significantly more in patients with LQTS (103 ± 80 ms vs 66 ± 40 ms in controls; P <.001) and so did QTc(return) (28 ± 48 ms for patients with LQTS vs -3 ± 32 ms for controls; P <.001). Using a sensitivity cutoff of 90%, the specificity for diagnosing LQTS was 74% for QTc(base), 84% for QTc(return), and 87% for QTc(stretch). The present study extends our previous findings on the abnormal response of the QT interval in response to standing in patients with LQTS. Our study also shows that this abnormal response persists even after the heart rate slows back to baseline.

The effect of levosimendan and dobutamine treatment on QT dispersion in patients with decompensated heart failure: a prospective study

We investigated the effect of intravenous levosimendan on QT dispersion compared with intravenous dobutamine in patients with acute decompensated heart failure. This prospective cohort study included 38 patients who were admitted with acute decompensated heart failure (New York Heart Association functional class III-IV). Twenty-five patients (11 men, 14 women; mean age 70.5 ± 11.13 years) were treated with levosimendan infusion and 13 patients (5 men, 8 women; mean age 71.08 ± 6.86 years) were treated with dobutamine infusion. Intravenous levosimendan was administered with an initial bolus dose of 12 μg/kg for 10 min, followed by a continuous infusion of 0.1 μg/kg/min for 1 hour and 0.1 μg/kg/min 23 hours. Intravenous dobutamine was administered with a continuous dose of 10 μg/kg /min for 24 hours. Transthoracic echocardiography was performed and electrocardiograms were obtained before and after drug infusions. QTc dispersion was defined as the difference between the maximum and the minimum QT intervals and the value was corrected for heart rate. Chi-square test, Wilcoxon test and Mann-Whitney U tests were used for data analysis. No significant differences were found before and after treatment of both levosimendan and dobutamine with respect to minimum QT intervals, maximum QT and QT dispersions. (Pretreatment and 24th hour values of levosimendan group were; 0.43 ± 0.04 s, 0.44 ± 0.04s; 0.49 ± 0.05s, 0.50 ± 0.05s; 0.06 ± 0.03s, 0.06 ± 0.03s; in dobutamine group values are - 0.39 ± 0.05 s, 0.41 ± 0.05s; 0.45 ± 0.05s, 0.48 ± 0.05s; 0.06 ± 0.04s, 0.06 ± 0.04s, respectively) (p>0.05). No side effects related to drugs were seen during follow-up in all two treatment groups. Our results suggest that, therapeutic doses of levosimendan infusion do not have a significant effect on QT parameters - the predictors of arrhythmias-, in patients with decompensated heart failure when compared with dobutamine infusion.

Electrocardiographic Findings in Patients With Primary Dysmenorrhea

IntroductionPrimary dysmenorrhea (PD), which is characterized by painful menstrual cycles, is one of the common clinical problems in young adult women. The aim of this study was to investigate the risk of cardiac arrhythmias in PD patients by using the electrocardiographic (ECG) parameters. MethodsForty patients diagnosed with PD and 30 age-matched normal controls were included in this study. ECGs were performed by using 12-leads with 10mV amplitude and 25mm/sec velocity. P and QT waves were manually marked along the isoelectric line. P maximum, P minimum, QT maximum and QT minimum were measured on the surface 12-leads ECG, and the P wave and QT dispersions were calculated. ResultsThere was not any significant correlation of P wave dispersion and QT dispersion between the age, sex, body mass index, hemoglobin, fasting blood glucose or any other laboratory parameters. P wave dispersion was significantly longer in the PD group than the control group (61.4±19msec versus 57±14 msec, P=0.01). The P minimum duration was significantly shorter in the PD group compared with the control group (36±16msec versus 41±9 msec, P=0.03). QT dispersion was significantly higher in the PD group compared with normal controls (76±23msec versus 58±16 msec, P=0.02). ConclusionThese results show that PD can be associated with cardiac arrhythmias, especially atrial fibrillation, by increasing P wave dispersion and ventricular arrhythmia risk because of an increased QT interval.

Effect of ovulation induction on QT dispersion in electrocardiography

To investigate whether ovulation induction resulting in supra-physiological concentration range of ovarian hormones has an effect on interlead ventricular depolarization heterogeneity via QT dispersion measurements. Estrogens influence the duration of cardiac repolarization but there is no significant change in the QT interval duration within the range of physiological estradiol variations. Materials and methods: Included in the study were 40 subjects, in whom ovulation induction was planned, and 20 volunteers. During the study, a 12-lead electrocardiogram of each woman was carried out 3 times: for the first time on day 2-3 of the menstrual cycle (menstrual day), for the second time 36 h after hCG administration (ovulatory day), and for the third time at 6-8 days following ovulation (mid-luteal day). The RR and QT wave distances were measured. The QT interval corrected for heart rate (corrected QT) was calculated for each derivation. The difference between the longest and shortest corrected QT intervals was determined as corrected QT dispersion. Results: No difference was seen in the mean QT and corrected QT interval duration and the maximum corrected QT interval duration between menstrual phases. On the ovulatory day at peak estrogen level, the corrected QT dispersion was found to be lower than on mid-luteal and menstrual day. Conclusion: QT dispersion demonstrates the regional repolarization heterogeneity of the myocardium, which reflects the propensity of ventricular arrhythmia decreases on the ovulatory day of the ovulation induction cycle.

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.

Serial Monitoring of the Physiological Effects of the Standard Pico-Salax® Regimen for Colon Cleansing in Healthy Volunteers

Sodium picosulfate⁄magnesium oxide⁄citric acid (Pico-Salax, Ferring Inc, Canada) is used widely in Canada and other countries for colon cleansing before colonoscopy. It is a low-volume osmotic⁄stimulant agent with the potential to deplete intravascular volume and alter electrolyte balance, yet there are little data regarding its effects on these clinically important end points. To serially measure parameters of intravascular volume and electrolyte status in healthy volunteers over a 24 h period using the standard two-sachet dosing. Twenty volunteers were given one sachet of Pico-Salax at time 0 h and another sachet 5 h later, as per usual bowel cleansing protocol. Subjects were continually monitored during the first 12 h of the study with postural vital signs, serum electrolytes and electrocardiograms obtained at intervals throughout this initial period and again at 24 h postingestion. No adverse events were reported nor were there any signs of intravascular volume depletion observed. There were decreases in potassium and calcium levels from baseline to 12 h, but these appeared minor and were corrected by 24 h. The proportions of patients with hypermagnesmia at 0 h, 5 h, 12 h and 24 h were 5%, 35%, 35% and 20%, respectively (P<0.05). However, the maximal values were only minimally elevated. Mean serum sodium, phosphate and creatinine levels remained within their respective reference ranges. There was a trend toward an increase in maximum corrected QT intervals from time 0 h (418 ms) to 5 h (430 ms) (P=0.06), but no significant change was seen subsequently at 12 h (419 ms). The subjects tolerated the medication well. The mean number of bowel movements per subject was 8.15 (range four to 15). Subjects consumed a mean (± SD) of 3.49±1.53 L of fluids during the observation period. The proportion of individuals with hypokalemia, hypocalcemia and hypermagnesemia following two sachets of Pico-Salax is significant, but the magnitude of the changes was not clinically relevant in this relatively small group, and both calcium and potassium levels normalized at 24 h. Nonetheless, this could have implications in patients with pre-existing electrolyte abnormalities and the safety of dosing with more than two sachets.

Effect of Pranayama (Breathing Exercise) on Arrhythmias in the Human Heart

Cardiac arrhythmias, especially ventricular tachyarrhythmias are an important public health problem. QT dispersion (QTd), defined as the difference between maximal and minimal QT intervals, reflects the regional inhomogeneity of ventricular repolarization dispersion and may mark the presence of malignant ventricular arrhythmias. To determine the effects of Pranayama (breathing exercise) on QTd in patients with arrhythmia. Fifteen patients with arrhythmia and ejection fractions <40% (mean = 28 ± 9%) who were on a stable medical regimen. Standardized 12-lead surface ECGs were obtained at the beginning and end of the Pranayama session, and QT and JT intervals were measured manually and corrected for heart rate by using Bazett's formula. QTd, heart rate-corrected QTd (QTc-d), JT dispersion (JTd), and heart ratecorrected JTd (JTc-d) were measured in at least eight ECG leads in each patient. Following the Pranayama session, patients with arrhythmia had only slight improvements in exercise capacity (results were not significant). However, these patients had marked improvements in QTd (71 ± 11 to 59 ± 17 ms; P < .02), QTc-d (82 ± 28 to 63 ± 17 ms; P < .01), JTd (76 ± 19 to 57 ± 18 ms; P < .002), and JTc-d (84 ± 23 to 61 ± 18 ms; P < .001) following the Pranayama session. These data indicate that Pranayama significantly reduces the indices of ventricular repolarization dispersion in patients with arrhythmia. Further studies are needed to evaluate how effectively this reduction in ventricular repolarization dispersion decreases the risk of malignant ventricular arrhythmias and sudden death in patients with arrhythmia.

Effects of aliskiren on QT duration and dispersion in hypertensive patients with type 2 diabetes mellitus

To evaluate the effect of aliskiren compared to amlodipine on QT duration and dispersion in hypertensive patients with type 2 diabetes. A total of 170 outpatients aged 50-75 years with mild to moderate hypertension (SBP >130 and <180 mmHg and DBP >80 and <100 mmHg) and type 2 diabetes were randomly treated with aliskiren 300 mg or amlodipine 10 mg, both given once daily for 24 weeks, according to a prospective, open label, blinded-end point, parallel group design. At the end of the placebo run-in, and after 12, and 24 weeks of treatment blood pressure (BP) measurements (by mercury sphygmomanometer, Korotkoff I and V), plasma biochemistry and a standard 12-lead surface ECG were evaluated. Both aliskiren and amlodipine significantly reduced systolic blood pressure (SBP)/diastolic blood pressure (DBP) values (-27.2/-14.3 mmHg, p < 0.001 vs. placebo and -27.8/-14.2 mmHg, p < 0.001 vs. placebo, respectively), with no statistical difference between the two drugs. Aliskiren, but not amlodipine, significantly reduced maximum QT interval (QTmax) (-14 ms at 12 weeks and -17 ms at 24 weeks, both p < 0.05 vs. placebo) and corrected QT max (QTc max) (-26 ms and -31 ms, p < 0.01) as well as the dispersion of both QT (-11 ms and -13 ms, p < 0.01) and QTc (-18 ms and -19 ms, p < 0.01). Despite similar BP lowering effect, aliskiren, but not amlodipine, reduced QT duration and dispersion, which might be related to the ability of aliskiren to interfere with mechanisms underlying myocardial electrical instability in the heart of diabetic hypertensive patients.

QT dispersion and cardiac involvement in children with Familial Mediterranean fever

Familial Mediterranean fever is a hereditary disease characterised by recurrent and self-terminated attacks of fever and polyserositis. An earlier study found that adult patients of Familial Mediterranean fever had an abnormally longer QT dispersion and corrected QT dispersion, markers for ventricular arrhythmogenicity. QT dispersion is a simple non-invasive arrhythmogenic marker that can be used to assess homogeneity of cardiac repolarisation; however, it has not been studied in children with Familial Mediterranean fever before. The aim of this study was to assess QT dispersion and corrected QT dispersion, and their relationship with systolic and diastolic function of the left ventricle in a group of children with Familial Mediterranean fever. We performed electrocardiography and Doppler echocardiography on patients and controls. Maximum QT, minimum QT, QT dispersion, corrected QT, maximum corrected QT, minimum corrected QT, and corrected QT dispersion intervals were measured from standard 12-lead electrocardiography. No statistically significant differences were found between the groups in QT dispersion, corrected QT dispersion, and systolic-diastolic function of the left ventricle parameters. During the 12 months of follow-up, no ventricular arrhythmias were documented in either group.

Heterogeneity of Ventricular Repolarization in Newborns With Severe Aortic Coarctation

Sudden death is a possible occurrence for newborns younger than 1 year with severe aortic coarctation (CoA) before surgical correction. Basic research and animal experiments have shown electrophysiologic changes during mechanical ventricular pressure overload. The current study aimed to evaluate the effect of severe CoA on the heterogeneity of ventricular repolarization by examining corrected QT and JT interval dispersion (respectively, QTc-D and JTc-D) and electrocardiographic parameters of spatial heterogeneity of ventricular repolarization in newborns with no associated congenital cardiac malformations. The study enrolled 30 isolated severe CoA neonates (age, 45 ± 15 days; 17 males) with normal size and wall thickness of the left ventricle before surgical correction and 30 age- and sex-matched healthy newborns used as control subjects. Heart rate, QRS duration, maximum and minimum QT and JT intervals, and QTc-D and JTc-D measurements were performed. The healthy control group did not significantly differ from the CoA group in terms of heart rate, weight, height, and echocardiographic parameters. Compared with the healthy control group, the CoA group presented significantly increased values of QTc-D (109.7 ± 43.4 vs. 23 ± 15 ms; P = 0.03) and JTc-D (99.1 ± 43.3 vs. 65.8 ± 24.1 ms; P = 0.04). A statistically significant correlation was found between the Doppler peak pressure gradient across the coarctation site and the values of QTc-D (r = 0.48; P = 0.03) and JTc-D (r = 0.42; P = 0.04). Our study showed significantly increased QTc-D and JTc-D in isolated CoA newborns with normal left ventricular geometry.

QT Dispersion is Not Increased in Familial Mediterranean Fever

Familial Mediterranean fever (FMF) is an autoimmune disease inherited as an autosomal recessive trait and is characterized by recurrent attacks of fever and sterile polyserositis. This study examined electrocardiographic ventricular repolarization parameters (QT interval and QT dispersion) in 38 FMF patients and 35 healthy controls. The QT interval was measured manually from the onset of QRS to the end of the T wave (return to the TP baseline). QT dispersion was defined as the difference between the maximum and minimum QT values, and corrected QT was calculated according to the Bazett formula. There were no significant differences between FMF patients and healthy control subjects in any parameter of ventricular repolarization; hence QT dispersion was not affected by FMF. Electrocardiographic assessment of QT interval and QT dispersion are, therefore, of little value for the evaluation of cardiac impairment and risk of arrhythmia in FMF patients.

QT dispersion before and after coronary artery angioplasty: A case study from Iran

AimIn this study, we investigated the changes in QT dispersion (QTd) after successful coronary artery revascularization. BackgroundQTd, as a marker of regional variability of myocardial repolarization, increases following impaired myocardial perfusion and is associated with increased risk of ischemia-induced arrhythmia. MethodsIn 45 consecutive patients (mean age 54.39±11.49 years) undergoing elective percutaneous coronary intervention (PCI), QTd was measured from a 12-lead electrocardiogram 6–12hours before and 6hours after the procedure. QTd was defined as the difference between maximum and minimum QT interval in the 12 leads. QT changes were analyzed regarding preoperative ejection fraction (EF), type and number of involved vessels, type and number of revascularized coronary arteries and history of Q-wave MI using SPSS software. ResultsQTd significantly decreased postoperatively from 55.48±20.03 to 42.00±19.96 in the study population (P=0.001). Subgroup analyses showed that QTd did not decrease significantly in patients with two-vessel disease and those with low EF (<50%); however, the reduction was significant for other subgroups. ConclusionSuccessful PCI results in improved regional heterogeneity of myocardial repolarization, evidenced as decreased QTd after the procedure.

The Relation Between Early Ventricular Tachycardia and QT Dispersion in Patients with Acute Myocardial Infarction Treated with Thrombolytic Therapy.

In this study, we investigated the influence of increased QT dispersion (defined as maximal QT interval minus minimal QT interval) on the occurrence of early nonsustained ventricular tachycardia (NSVT) in patients with acute myocardial infarction (AMI) who received thrombolytic therapy. In the retrospective analysis of 96 patients with clinical reperfusion criteria, 36 had NSVT within the first 12 hours after the onset of thrombolytic therapy (group A), and 60 patients did not have NSVT during the same period (group B). On admission ECG, QT and QT(c) dispersion and the amount of jeopardized myocardial area (Aldrich score) were calculated. In group A, Aldrich score was significantly higher (21.4 +/- 7.2% vs 14.2 +/- 4.9%; p < 0.005). There were significantly higher QT dispersion values on admission (83.3 +/- 23.4 vs 67.5 +/- 23.7 msec; p < 0.005), at 24th hour (87.1 +/- 12.6 vs 72.1 +/- 27.4 msec; p < 0.005) and on the 10th day (63.5 +/- 31.2 vs 49.5 +/- 14.3 msec; p < 0.005) in group A. In subgroup analysis of group A, patients with NSVT between 6-12 hours (group A2) had significantly higher Aldrich score and QT dispersion values at all above time points compared to patients with NSVT between 0-6 hours (group A1) after AMI. In conclusion, in this study we found a strong relation between the occurrence of NSVT within 12 hours and increased QT dispersion on admission ECG in patients with AMI who received thrombolytic therapy. This relation was even stronger for the subgroup of patients with NSVT within 6-12 hours. Thus, these results may indicate that NSVT is related to increased QT dispersion which is secondary to larger jeopardized myocardial area in patients with AMI. </hea

QT interval analysis in type 2 diabetic patients

Background: The electrocardiographic QT interval has been extensively studied in diabetes mellitus. Recently, there has been increasing interest in the relationship between diabetes and QT abnormalities .The QT interval, which is easily obtained from a standard resting electrocardiogram( ECG), reflected the total duration of ventricular myocardial depolarization and repolarization. The heart rate corrected QT interval (QTc) by Bazett's formula on the electrocardiogram has been proposed as a risk factor for ventricular arrhythmias in diabetes mellitus. Dispersion of QT(QTd) is defined as the difference between maximum and minimum QT interval QT interval on 12 lead ECG, which reflected spatial ventricular repolarization in homogeneity ,has been report to increase in diabetic subjects compare with non diabetic subjects.Patients and Methods: Type 2 diabetic patients (n=80) and healthy subjects (n=25) were required to have 12-lead ECG suitable for QT analysis ,QT interval was measured in each lead tofound(maximum, minimum, and mean ).QT interval vary according to the heart rate, it can be corrected using Bazett's formula to give QTc interval, and to found (maximum, minimum, and mean).Dispersion of QT interval(QTd) was calculate using the difference between the maximum and minimum QT interval duration as same as for dispersion of corrected QT interval(QTcd).Result: There were significant difference in QT interval indices between type 2 diabetic and healthy subjects (P&lt;0.05) as well as the correct QT interval indices. ROC curve analysis of QT and QTc interval duration parameters demonstrated that no QT parameters performs better than maximum and minimum of QT and QTc, areas under ROC curve were(0.69 and 0.66 P&lt;0.001)for maximum and mean QT respectively and (0.80 and 0.75 P&lt;0.001) for maximum and mean QTc respectively. From this result we can say that QTc parameters better than QT parameters in context of patients and control differences. In multiple linear regression models, maximum, mean, and dispersion of QT interval were significantly affect by diabetes mellitus after adjustment for age, gender, body mass index (BMI), and heart rate. Whereas, only maximum and mean QTc were significantly affected by diabetes mellitus after adjustment for age, gender, and BMI. Prolongation of QT interval (QTc and QTd) also seen in a diabetic subjects which significant different as compare to the healthy subjects.Conclusion: The result of this study indicate that corrected QT interval (maximum and mean)in a routine ECG is a useful marker to identify the QT abnormalities differentiating diabetes type 2 from healthy subjects.

Clinical determinants of electrocardiographic and spatial vectorcardiographic descriptors of ventricular repolarization in healthy children.

Although the association of repolarization alterations to the development of life-threatening ventricular arrhythmias has received considerable research attention, there is paucity of data regarding what may be considered as normal, especially in children. To define electrocardiographic (ECG) and vectorcardiographic (VCG) descriptors of ventricular repolarization in healthy school-age children, 12-lead digital ECGs were obtained from 646 children (348 males/298 females, mean age 8.54 ± 1.86 years). All QT intervals were measured manually using the digitally stored ECGs. Orthogonal X, Y, and Z leads were reconstructed from the standard 12-lead ECGs and the maximal amplitudes of the spatial QRS and T vectors were calculated, as well as the spatial QRS-T angle. The mean heart rate was 95.3 ± 15.8 bpm and the QRS duration was 83.4 ± 9.3 ms. Mean QT interval was 334.1 ± 24.2 ms and the corrected QT interval was 436.5 ± 23.8 ms (Bazzet) and 404.3 ± 19.4 ms (Fridericia). Although the uncorrected maximum and mean QT intervals were significantly higher in boys (P values 0.011 and 0.009, respectively), there was no difference in the rate-corrected QT interval. The spatial QRS and T-vector amplitudes were 1512.0 ± 365.7 μV and 478.8 ± 149.3 μV, respectively. The spatial QRS-T angle was 14.1 ± 8.0 degrees. Although the mean QT interval showed significant increase with age (P = 0.014), all VCG parameters did not show significant variance with age. A range of ECG and VCG descriptors of ventricular repolarization was determined in a large sample of healthy school-age children to provide a data basis of normal values for future reference.

Factors associated with a prolonged QT interval in liver cirrhosis patients

The aim of this study was to identify factors associated with prolonged QT interval in liver cirrhosis patients. Thirty-eight patients with liver cirrhosis were enrolled in this study. The maximal QT interval (QTmax), heart rate-corrected QT interval (QTc), QT interval in lead DII (QTII), and mean QT interval (QTm) were determined manually, using 12-lead electrocardiogram. Additional laboratory tests were also performed. The following values were obtained: QTmax, 435 ± 43 milliseconds; QTc, 493 ± 46 milliseconds; QT interval in lead DII, 405 ± 46 milliseconds; and mean QT interval, 400 ± 40 milliseconds. Ten (6%) patients had a prolonged QTmax, and 27 (71%) had a prolonged QTc. The highest values were obtained for QTc and QTmax in patients with alcoholic cirrhosis and Child-Pugh class C, respectively. A moderate correlation was observed between QTmax and serum uric acid (URCA; r = 0.504), and multiple linear regression analysis revealed that URCA was significantly associated with QTc and heart rate. Liver disease severity, alcoholic etiology, and URCA are associated with prolonged QT interval in patients with liver cirrhosis.

05 The electro-mechanical window as Torsade de Pointes risk marker in conscious and anaesthetised dogs after IKS blockade

The electro-mechanical window (EMw) is a recently proposed biomarker describing the temporal difference between electrical and mechanical events in beating hearts and is a precursor to identify Torsade de Pointes...

The effects of perindopril on QT duration and dispersion in patients with coronary slow flow

Coronary slow flow (CSF) is characterized by delayed opacification of coronary arteries in the absence epicardial occlusive disease. QT duration and dispersion have been reported to be longer in patients with CSF. ACE inhibitors may improve CSF through positive effects on endothelial function. The study included 32 patients having CSF and 25 subjects having normal coronary arteries in coronary angiography. The patients were evaluated with 12-leads electrocardiography and echocardiography before and 3 months after treatment with perindopril. Compared to the control group, maximum corrected QT duration (QTcmax) (432.0 ± 28.9 vs. 407.0 ± 39.1 ms, p = 0.008) and QT dispersion (QTcD) (64.0 ± 16.5 vs. 37.3 ± 12.1 ms, p < 0.001), mitral inflow deceleration time (DT) (251.3 ± 49.4 vs. 218.8 ± 44.5 ms, p = 0.013), and isovolumetric relaxation time (IVRT) (115.8 ± 18.4 vs. 107.2 ± 22.9 ms, p < 0.001) were significantly longer and E/A ratio 0.85 ± 0.2 vs. 1.1 ± 0.3, p = 0.004) was lower in patients with CSF. QTcmax (to 407.0 ± 28.0 ms, p = 0.001), QTcD (to 44.5 ± 11.4 ms, p < 0.001), DT (to 221.6 ± 37.7 ms, p < 0.001) and IVRT (to 103.8 ± 16.1 ms, p < 0.001) were significantly decreased and E/A ratio (to 0.98 ± 0.3, p < 0.001) was significantly increased after treatment with perindopril. Coronary slow may be associated with prolonged QT interval and increased QT dispersion and impaired diastolic filling. Perindopril may be helpful in restoration of these findings.

QT dispersion in patients with pulmonary embolism

Various ECG patterns have been associated with acute pulmonary embolism. However, there is no data regarding the association between QT interval measurements and pulmonary embolism. We aimed to investigate the association between QT dispersion and the severity of pulmonary embolism (PE). One hundred twenty-nine pulmonary embolism patients (mean age 58 ± 16.5 years) with ECGs obtained within the first 24 hours of hospital admission were included in the study. Patients were classified into low, intermediate and high-risk groups. We retrospectively measured ECG scores; maximum and minimum corrected QT intervals (QTc(max) and QTc(min)) and corrected QT interval dispersion (QTcd) in each risk group of patients. There was an increasing ECG score through from low to high-risk PE [3 (Interquartile Range, IQR: 2), 5 (IQR: 6) and 10 (IQR: 7) p < 0.0001]. QT interval analysis showed that QTcd was higher in high-risk group than in low and intermediate-risk groups (59.5 ± 23.4, 69.2 ± 21, 95.9 ± 33.2, p <0.001 and p = 0.01, respectively). Patients who died after diagnosis had significantly higher QTcd values at baseline compared with the QTcd values of surviving patients (89.1 ± 45.5 to 65 ± 22.9, p = 0.001). The sensitivity of QTcd > 71.5 ms for prediction of mortality was 71% with a specificity of 73% (p = 0.001). We observed a strong correlation between QTcd and ECG score values (r = 0.69, p< 0.001). There was also a correlation between QTcd values and pulmonary artery pressure (PAP) (r = 0.27, p = 0.05). QTcd is significantly increased in high-risk PE patients compared to intermediate and low-risk patients. In addition, QTcd is significantly correlated with ECG score and PAP.

QT dispersion in childhood obstructive sleep apnoea syndrome

The difference between maximal and minimal QT interval and corrected QT interval defined as QT dispersion and corrected QT dispersion may represent arrhythmogenic risks. This study sought to evaluate QT dispersion and corrected QT dispersion in childhood obstructive sleep apnoea syndrome. Forty-four children (34 male) with obstructive sleep apnoea syndrome, aged 6.2 plus or minus 3.5 years along with 38 healthy children (25 male), 6.6 plus or minus 2.1 years underwent electrocardiography to measure QT and RR intervals. Means QT dispersion and corrected QT dispersion were significantly higher in obstructive sleep apnoea syndrome than controls, 52 plus or minus 27 compared to 40 plus or minus 14 milliseconds (p equal to 0.014), and 71 plus or minus 29 compared to 57 plus or minus 19 milliseconds (p equal to 0.010), respectively. Interestingly, QT dispersion and corrected QT dispersion in obstructive sleep apnoea syndrome with obesity, 57 plus or minus 30 and 73 plus or minus 31 milliseconds, were significantly higher than in control, 40 plus or minus 14 and 57 plus or minus 19 milliseconds (p equal to 0.009 and 0.043, respectively). However, QT dispersion and corrected QT dispersion in obstructive sleep apnoea syndrome without obesity, 43 plus or minus 20 and 68 plus or minus 26 milliseconds, were not significantly different. In conclusion, QT dispersion and corrected QT dispersion were significantly increased only in childhood obstructive sleep apnoea syndrome with obesity. Obesity may be the factor affecting the increased QT dispersion and corrected QT dispersion.