QT Dispersion Ratio Research Articles

Abstract 14577: Electrocardiogram Parameters for Predicting the Severity of Coronary Artery Disease in Non-ST Segment Elevation Acute Coronary Syndrome

Background: Quantitative electrocardiogram (ECG) parameters have been found to correlate with severity of coronary artery disease (CAD). Thus, it may serve the purpose of risk stratifying patients with non-ST segment elevation acute coronary syndrome (NSTEACS). But little is known about the accuracy of each parameter.So, this study was done to assess the correlation of ECG parameters with severity of CAD in patients with NSTEACS and to compare the diagnostic accuracy among them. Methods: 178 patients with NSTEACS with left ventricular ejection fraction >50% were selected for the study after excluding patients with heart failure, arrhythmia, prior myocardial infarction or revascularisation. P wave peak time (PWPT), corrected QT dispersion (cQTd) and QT dispersion ratio (QTDR) was calculated in all patients. CAD severity was assessed visually by coronary angiography and calculating the syntax score. Results: PWPT, cQTd and QTDR were increased significantly in patients with left main (LM) or triple vessel disease (TVD) than others. These parameters also showed a strong positive correlation with the syntax score ( P<.001 ). Among these parameters, cQTd showed the best diagnostic accuracy (76% sensitivity and 64% specificity) to detect LM or TVD with a cut-ff value of 74 ms. Conclusion: PWPT, cQTd and QTDR may help to identify high risk patients with NSTEACS and early invasive procedure can be done to salvage a large area of myocardium at jeopardy. These may be particularly helpful to the physicians in periphery who have limited resources. Keywords: coronary artery disease, non-ST segment elevation acute coronary syndrome, P wave peak time, corrected QT dispersion, QT dispersion ratio

Repolarization dispersion in patients with systemic sclerosis.

Systemic sclerosis (SSc) is associated with increased cardiac morbidity and mortality. Whether some electrocardiographic markers of arrhythmias predispose to early cardiogenic death in SSc remains controversial. This study evaluated the occurrence of previously reported as well as unstudied markers of repolarization in patients with SSc and assessed their prognostic implications. A total of 21 patients with SSc and 31 unaffected controls were included in this prospective study. Electrocardiograms were conducted under strict standards. Repolarization and dispersion parameters and markers of late ventricular potentials were determined using designated computer software. Results of multiple beats were averaged. There were no significant differences between the SSc and control groups in average QT intervals, average corrected QT intervals, average QT interval dispersion (QTd), average QT corrected dispersion (QTcd), and QT dispersion ratio. However, average QT apex dispersion, average JT dispersion, average JT corrected dispersion, and Tpeak-Tend corrected were significantly higher in patients with SSc than in controls. Late ventricular potentials were not found in patients with SSc or in controls. Increased QTd and QTcd were recorded in 1 patient who experienced ventricular arrhythmia before inclusion in the study. None of the remaining patients with SSc or the controls developed arrhythmia during the 9-year follow-up. Abnormal repolarization parameters may be observed in patients with SSc. However, their prognostic significance with regard to increased risk for repolarization-associated ventricular arrhythmias and increased cardiac death could not be determined in this study. Our findings endorse additional studies on this matter.

Effects of Antipsychotics on Arrhythmogenic Parameters in Schizophrenia Patients: Beyond Corrected QT Interval.

PurposeAntipsychotic drugs have been implicated as risk factors for QT prolongation, which is a predictor of sudden cardiac death. However, the QT interval is considered an imperfect marker for proarrhythmic risk. Recently, improved methods, namely, QT dispersion (QTD), QTD ratio (QTDR), T wave peak-to-end interval (Tp-e), Tp-e/QT ratio and Tp-e/QTc ratio, have been regarded as proarrhythmic risk markers. We attempted to reevaluate the risk of sudden cardiac death due to antipsychotics use by measuring these improved evaluation methods.Patients and MethodsWe retrospectively evaluated QTc, QTD, QTDR, Tp-e, Tp-e/QT ratio and Tp-e/QTc ratio from the medical records of 410 patients with schizophrenia diagnosed by the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision, or 5th Edition. Information on drugs administered was obtained from medical records. We investigated the correlation between each index on ECG and medication, such as antipsychotics, prescribed to participants with linear regression analysis. We also compared each index between 235 healthy controls and 235 patients matched for age and sex.ResultsPositive correlations between QTc and levomepromazine and brexpiprazole were identified. Levomepromazine and lithium were positively correlated with QTD. Levomepromazine, quetiapine, asenapine, clozapine and carbamazepine were positively correlated with QTDR. Levomepromazine, olanzapine, brexpiprazole and lithium were positively correlated with Tp-e. Olanzapine, brexpiprazole and lithium were positively correlated with the Tp-e/QT ratio. Olanzapine, brexpiprazole and lithium were positively correlated with Tp-e/QTc ratio. Significant differences in all indexes were noted between the patients and healthy controls.ConclusionAccording to our results, the prediction of the risk of sudden cardiac death by each index was inconsistent. We should evaluate the predictive factor of ventricular arrhythmia according to various electrocardiogram indexes because QTc alone could not identify the risk of sudden cardiac death.

QT Interval Derived Measurements in Patients with Cardiac Syndrome X Compared to Coronary Artery Disease.

Previous studies assessing effect of ischemia on ventricular repolarization are mostly directed toward patients with coronary artery disease (CAD); however, similar reports on cardiac syndrome X (CSX) are scarce. Whether microvascular dysfunction of CSX and ischemia induced by CAD produce comparable effect on ventricular repolarization is unclear and deserve further studies. In the present study, ECG measures of ventricular repolarization were compared between CAD and CSX patients (40 subjects in each group). Following evaluation of sociodemographic characteristics, medical and past medical history, a resting ECG was used to assess measurements of ventricular repolarization in each patient, namely, QT interval (QT), corrected QT interval (QTc), QT dispersion (QTd), corrected QT dispersion (QTcd), adjacent QT dispersion (AdQTd), QT dispersion ratio (QTdR), JT dispersion (JTd), and Corrected JT dispersion (JTcd). Results showed comparable QT intervals and QTd in CAD and CSX patients even after adjustment for the possible variations in gender, age and body mass index of the studied groups. Although JTd was increased in CSX subjects (26.6 ± 7.2 ms) compared with CAD patients (22.7 ± 6.5 ms, p = 0.019), statistical significance disappeared after correcting JT for variations in heart rate. QT and QTc were significantly below 440 ms in CAD as well as CSX patients (p < 0.001). In contrast, maximum QTd, maximum QTcd and AdQTd of CAD and CSX patients were significantly above 440 ms (p < 0.001). The means of JTd and JTcd were significantly above 22 ms and 24 ms respectively (p < 0.001, p = 0.001) in CSX but not CAD patients (p = 0.529, p = 0.281). The present findings clearly demonstrate comparable measures of ventricular repolarization in CAD and CSX patients and consequently an equal risk of cardiac events in both groups.

The Relationship between P & QT Dispersions and Presence & Severity of Stable Coronary Artery Disease.

Background and ObjectivesThe study aimed to evaluate the correlation between electrocardiographic (ECG) parameters and presence and extent of coronary artery disease (CAD) to indicate the usefulness of these parameters as predictors of severity in patients with stable CAD.Subjects and MethodsTwo hundred fifty patients, without a history of any cardiovascular event were included in the study. The ECG parameters were measured manually by a cardiologist before coronary angiography. The patients were allocated into five groups: those with normal coronary arteries (Group 1), non-critical coronary lesions (Group 2), one, two and three vessel disease (Group 3, Group 4 and Group 5, respectively.ResultsGroup 1 had the lowest P wave dispersion (PWD) and P wave (Pmax), QT interval (QTmax), QT dispersion (QTd), corrected QT dispersion (QTcd) and QT dispersion ratio (QTdR), while the patients in group 5 had the highest values of these parameters. Gensini score and QTmax, QTd, QTcmax, QTcd, QTdR, Pmax, and PWD were positively correlated. QTdR was the best ECG parameter to differentiate group 1 and 2 from groups with significant stenosis (groups 3, 4, and 5) (area under curve [AUC] 0.846). QTdR was the best ECG parameter to detect coronary arterial narrowing lesser than 50% and greater than 50%, respectively (AUC 0.858).ConclusionPresence and severity of CAD can be determined by using ECG in patients with stable CAD and normal left ventricular function.

Electrocardiography changes in bipolar patients during long-term lithium monotherapy

ObjectiveCardiovascular side effects of lithium have been reported to occur mainly at higher-than-therapeutic serum levels. We aimed to investigate the impact of the long-term lithium use on electrocardiogram (ECG) parameters in association with the serum levels in patients with bipolar disorder (BD) and in healthy controls (HCs) serving as the reference group. MethodsThe study sample consisted of 53 euthymic BD type I patients on lithium monotherapy at therapeutic serum levels (M=0.76, S.D.=0.14, range=0.41–1.09 mmol/l) for at least 12 months and 45 HCs. A 12-lead surface ECG was obtained from all participants at resting state for at least half an hour for 5-min recording. Heart-rate, Pmax, Pmin, QRS interval, QT dispersion, QT dispersion ratio (QTdR) and Tpeak-to-end interval (TpTe) were measured. ResultsRegression analyses revealed that QTdR (B=14.17, P=.001), TpTe (B=18.38, P<.001), Pmax (B=17.84, P<.001) and Pmin (B=25.10, P<.001) were increased in BD patients who were on chronic lithium treatment than in HCs after controlling for age, sex and strict Bonferroni correction for multiple testing. There were no associations between serum lithium levels and ECG parameters. ConclusionOur findings suggest that the use of lithium is associated with both atrial and ventricular electrical instability, even when lithium levels are in the therapeutic range.

Prolonged QTc Dispersion Correlates with Coronary Artery Disease in Acute ST Elevated Myocardial Infarction (STEMI)

Background: It has been found that there is strong association of QT dispersion and QT dispersion ratio with extent and severity of coronary artery disease. Qualitative importance of QTc dispersion on the base line ECG in patients with MI is recognized clinically but quantification of this phenomenon is less commonly used in clinical practice, which might be a better independent risk predictor of this group of patients. Methods: A total of 100 patients were selected, Study populations sub-divided into two groups on the basis of QTc dispersion. In group I (comparison group): QTc dispersion is &lt;60 milliseconds (msec) in group II (study group) : QTc dispersion e”60milliseconds(msec). 50 patients in each group. QT dispersion was calculated on standard resting 12 lead ECGs. QT interval was measured from the beginning of the inscription of the QRS complex to the point at which the T wave returned to the isoelectric line. Angiographic severity of coronary artery disease was assessed by- Vessel score, Friesinger score and Leaman score. Interpretation of coronary angiogram was reviewed by at least two cardiologists. . Results: The mean vessel score for group I patients was 1.16±0.68 and that of group II patients was 2.30±0.64 and the mean difference was statistically significant (p&lt;0.05). Patients those had single vessel involvement had mean QTc dispersion 57.05, patients those had double vessel disease mean QTc dispersion was 102.00 and patients those had triple vessel involvement had mean QTc dispersion 177.60. There was a strong positive correlation with the QTc dispersion and increasing number of vessel involvement (Pearson’s correlation coefficient). The mean Friesinger score for group I patients was 4.84±2.56 and that of group II patients was 9.80±2.60. The mean difference was significantly (p&lt;0.05) higher in group II patients. There was a strong positive correlation between the QTc dispersion and Leaman score (Pearson’s correlation coefficient). In group I patients 56% had insignificant coronary artery disease and 44% had significant coronary artery disease defined by Friesinger index (n=100). In group II patients 6% had Insignificant coronary artery disease &amp; had 94% significant coronary artery disease. Conclusion: QTc dispersion&gt;60 ms had independent predictive value for the severity of coronary artery disease. The greater the QTc dispersion the higher the number of coronary artery involvement. We observed that there is a positive correlation between prolonged QT dispersion and coronary artery disease severity in terms of Vessel score, Friesinger score, Leaman score. DOI: http://dx.doi.org/10.3329/cardio.v5i2.14322 Cardiovasc. j. 2013; 5(2): 173-181

Normal QT dispersion in colchicine-resistant familial Mediterranean fever (FMF)

The association between familial Mediterranean fever (FMF) and subclinical cardiac disease remains controversial. The aim of the current study was to evaluate whether FMF patients, who do not respond to colchicine treatment, and thereby endure persistent inflammation, have increased QT dispersion (QTd) values. Twenty-two FMF patients and 22 age- and sex-matched control subjects were included in the study. Repolarization and QT dispersion parameters were computed from 12-lead ECG recording using designated computer software, and results of five beats were subsequently averaged. Both FMF patients and controls had similar comorbidities, similar values of average QT, average corrected QT interval length, average QTd interval, average QT corrected dispersion, QT dispersion ratio, JT dispersion (JTd), and JT corrected dispersion. In conclusion, FMF patients who were unresponsive to colchicine treatment and did not develop amyloidosis had normal QTd and JTd parameters, indicating a non-increased risk for repolarization-associated ventricular arrhythmias.

QT dispersion in amyloidosis due to familial Mediterranean fever

Cardiac amyloid deposition in FMF may cause increased QT dispersion (QTd), a marker for cardiac arrhythmias. The aim of this study was to further evaluate repolarization dispersion in familial Mediterranean fever (FMF) with amyloidosis. Findings on 12-lead electrocardiography were compared between 18 patients with FMF-amyloidosis and 18 age- and sex-matched control subjects. Repolarization and dispersion parameters were computed with designated computer software, and results of the 5 beats were subsequently averaged. There were no statistically significant differences between the groups as to average corrected QT interval length, average QTd interval, average QT corrected dispersion, or QT dispersion ratio. JT dispersion and JT corrected dispersion were also similar in both groups. In conclusion, patients with FMF-amyloidosis seem to have QT and JT dispersion parameters similar to those of healthy subjects. Future research and longer follow-ups should be conducted in order to evaluate the prognostic importance of repolarization dispersion parameters in amyloidosis of FMF.

QT dispersion in uncomplicated familial Mediterranean fever

The aim of the study was to further evaluate repolarization dispersion in familial Mediterranean fever (FMF). Findings on 12-lead electrocardiography were compared with 32 patients with uncomplicated FMF and age- and sex-matched control subjects. All procedures followed stringent standards. Repolarization and dispersion parameters were computed with designated computer software, and results of the five beats were subsequently averaged. There were no statistically significant differences between the groups in average QT and average corrected QT interval length, average QT interval dispersion, average QT corrected dispersion, or QT dispersion ratio. During 6 months of follow-up, no cases of sudden death or arrhythmia were documented in either group. Patients with FMF who are continuously treated with low-dose colchicine and have not developed amyloidosis seem to have QT dispersion parameters similar to those of healthy subjects and therefore apparently have no increased risk of adverse cardiac events associated with abnormal repolarization.

The Association of QT Dispersion and QT Dispersion Ratio with Extent and Severity of Coronary Artery Disease

Although prolongation of the QT intervals in acute ischemic conditions, such as acute myocardial infarction, intracoronary balloon inflation, and exercise induced ischemia, has been shown, association of rest QT intervals with extent and severity of stable coronary artery disease (CAD) has not been assessed so far. The effects of extent and severity of stable CAD on rest QT interval were analyzed in this study. Rest 12-lead electrocardiograms (ECG) were recorded in 162 clinically stable subjects undergoing coronary angiography before the angiography for measurement of corrected QT dispersion (cQTd) and the QT dispersion ratio (QTdR) defined as QT dispersion divided by cycle length and expressed as a percentage. Angiographic "vessel score,""diffuse score," and "Gensini score" were used to evaluate the extent and severity of coronary atherosclerosis. Subjects were grouped as follows: those with normal angiogram (Group 1), those with insignificant (<50%) coronary stenosis (Group 2), and those with 1- (Group 3), 2- (Group 4), or 3-vessel disease (Group 5). cQTd and QTdR were higher in Group 3 compared with Group 1 (P < 0.001 and P = 0.001, respectively), in Group 4 compared with Group 1 (P < 0.001 for both) and Group 2 (P = 0.001 and P = 0.003, respectively), and in Group 5 compared with Group 1 (P < 0.001 for both) and Group 2 (P < 0.001 and P = 0.003, respectively). cQTd and QTdR were positively correlated with the vessel score (r = 0.422, P < 0.001; r = 0.358, P < 0.001, respectively), diffuse score (r = 0.401, P < 0.001; r = 0.357, P < 0.001, respectively) and Gensini score (r = 0.378, P < 0.001; r = 0.373, P < 0.001, respectively). In multiple linear regression analyses, cQTd was found to be independently associated only with diffuse score (beta= 0.325, P = 0.038). Also, QTdR was independently associated with diffuse score (beta= 0.416, P = 0.006) and Gensini score (beta= 0.374, P = 0.011). Rest cQTd and QTdR are increased, and related to the extent and severity of coronary atherosclerosis in patients with stable CAD.

New parameters in the interpretation of exercise testing in women: QTc dispersion and QT dispersion ratio difference.

It has been reported that the increase of QT dispersion (QTD) that occurs due to increased inhomogeneity of the ventricular repolarization because of transient ischemia obtained by standard 12-lead electrocardiogram (ECG), the changes during exercise, and the differences between exercise and rest increase the accuracy of exercise test in the diagnosis of coronary artery disease (CAD). This study was designed to investigate the value of QTD parameters, which are reported to increase the diagnostic accuracy of exercise test in women. Ninety-seven women who had undergone coronary angiography and exercise test were evaluated for diagnosis of chest pain. QT dispersion was calculated using the measurements of the highest and lowest values of QT interval obtained by ECG during peak exercise. The QTc using Bazett's equation, and the QTD ratio (QTDR) using QT/RR were calculated, and QTcD and QTD ratios were obtained. The difference between QTcD and QTDR was determined by extracting the rest values from the exercise values. The groups with normal coronaries (n = 48), single-vessel CAD (n = 24), and multivessel CAD (n = 25) were compared. The obtained QTD parameters at peak exercise and their differences between exercise and rest were found to be significantly increased in patients with CAD (p <0.001). Furthermore, these parameters were found to be higher in the patients with multivessel CAD than in those with single-vessel disease (p < 0.05). With the parameters QTcD > 60 ms and QTDR > 10%, greater sensitivity and specificity were obtained compared with ST-segment depression. The highest diagnostic accuracy was obtained with the QTD parameters calculated from the differences between rest and exercise values. The diagnostic accuracy of the difference of QTcD > 15 ms and the difference of QTDR > 5% was relatively higher than the other parameters (sensitivity, specificity, and negative and positive predictor values are 84, 88, 84, 87% and 84, 96, 85, 95%, respectively). The use of QTD parameters as variables of ECG, which is easily obtainable in the evaluation of exercise ECG in women, increases the diagnostic accuracy of the exercise test. In addition, the evaluation of QTD variables may provide information about the incidence of CAD.

QT dispersion ratio in patients with unstable angina pectoris (a new risk factor?).

QT dispersion has been shown to be associated with fatal arrhythmias and sudden death in coronary artery disease. A recent study indicated that marked QT dispersion in electrocardiograms (ECGs) obtained during acute ischemia demonstrated a significant correlation with ventricular fibrillation. This study investigated the ECG parameters for repolarization (QT dispersion, corrected QT, corrected QT dispersion, and QT dispersion ratio) and their interrelation with acute ischemia. QT parameters as well as a newly developed repolarization index, QT dispersion ratio [(QT dispersion/RR interval) x 100] were calculated digitally during rest and ischemia in 32 patients with coronary artery disease (rest angina, Braunwald class III). Results were correlated with clinical consequences, mainly arrhythmias, within a follow-up period of 5 +/- 2 days. While most patients had an increase in all four parameters, only the QT dispersion ratio showed a significant difference when correlated with ventricular arrhythmias (p < 0.001, F ratio = 38). QT dispersion ratio appears to be a new and promising parameter in predicting ventricular arrhythmias in patients with acute ischemia.

Propafenone During Acute Myocardial Ischemia in Patients: A Double-Blind, Randomized, Placebo-Controlled Study

Objectives. The proarrhythmic risk of class I antiarrhythmic agents in combination with myocardial ischemia is mainly the result of their effects on ventricular repolarization. This study was designed to evaluate the effect of class Ic antiarrhythmic agents on QT dispersion during myocardial ischemia.Background. QT interval dispersion on the 12-lead electrocardiogram (ECG) has been suggested as a noninvasive marker of inhomogeneous ventricular repolarization and susceptibility to ventricular arrhythmias.Methods. In a randomized, double-blind study, 98 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) were pretreated with propafenone or placebo. QT dispersion was defined as a maximal minus minimal QT interval on the 12-lead ECG before and after PTCA. The power of the study to detect clinically meaningful differences in QT dispersion was 0.75, and a twofold increase in QT dispersion in the propafenone group compared with the placebo group was considered clinically relevant.Results. The QT and corrected QT (QTc) intervals increased significantly during occlusion of the left anterior descending coronary artery (LAD) (9% and 11%, respectively, p < 0.05), whereas occlusion of the circumflex and right coronary arteries had no effect. QTc dispersion increased significantly in the propafenone group during ischemia (+52%, p = 0.002, vs. +23%, p = 0.15). The most considerable effect on QT dispersion was observed during LAD occlusion and ischemia of the anterior wall (+74%, p = 0.025). Corrected JT dispersion (+57%, p = 0.017, vs. +24%, p = 0.23) and the QT dispersion ratio (+1.6%, p = 0.031, vs. 0.9%, p = 0.34) showed similar effects. Plasma levels of propafenone (522 ± 165 μg/liter) did not influence the results.Conclusions. During myocardial ischemia, particularly during LAD occlusion, propafenone results in a significant increase in QT dispersion. The results indicate that QT interval prolongation and enhanced QT dispersion reflect inhomogeneous ventricular repolarization generated by the ischemic anterior wall of the myocardium. These observations may demonstrate a clinically important interaction between myocardial ischemia, repolarization variables and propafenone.(J Am Coll Cardiol 1997;29:561–7)