Effect of dipyridamole on QT dispersion in vasospastic angina pectoris

Relationship between a Prolonged Corrected QT Interval and Mortality in Patients Presenting with Syncope at the Emergency Department

Background

Syncope is a common symptom in emergency department patients. Among various etiological factors, cardiac causes have the highest risk of mortality. The corrected QT interval is considered an independent predictor of mortality for many diseases.

Objectives

Analyze QT interval analysis of patients presenting to the emergency department with syncope.

Methods

In this prospective observational study, patients who presented to the emergency department with syncope between January 1, 2018, and January 1, 2019 were included.

Results

The median age was 64 (49-78) years, and 58.8% of patients were male. The corrected QT interval (QTc) in patients with coronary artery disease and chronic obstructive pulmonary disease was longer than those without. There was no statistically significant association between hypertension, diabetes, stroke, thyroid disease, and prolonged QTc. Patients who did not survive had significantly prolonged QT intervals. According to ROC analysis, sensitivity of >440.5 ms QTc values in predicting mortality was 86% and specificity was 71% (AUC = 0.815; 95%CI = 0.71 − 0.91; p < 0.001).

Conclusions

Patients admitted to emergency department with syncope and a prolonged QTc are associated with a higher mortality rate and thus can provide us with an important guide for the management of these patients.

Tpeak-Tend dispersion as a predictor for malignant arrhythmia events in patients with vasospastic angina

BACKGROUND

Tpeak-Tend interval (Tp-e interval) in electrocardiogram (ECG) has been reported to predict malignant arrhythmia events (MAE) in ST-segment elevation myocardial infarction and ion channelopathy. Tp-e interval and other ECG parameters as predictors for MAE was evaluated in patients with vasospastic angina (VA).

METHODS AND RESULTS

Sixty-two patients with VA (Non-MAE group) and 20 patients with VA complicated by MAE (MAE group) were enrolled in our Division of Cardiology between January 2010 and December 2015. Continuous variables were analyzed by t-test and categorical variables by Chi-square analysis. Patients with MAE showed greater QTc (corrected QT interval) dispersion (P=0.005), Tp-ec (corrected Tp-e) interval (P=0.001), Tp-ec dispersion (P<0.001) and Tp-e/QT ratio (P<0.001) than those in non-MAE groups when ST-segment elevated. After elevated ST-segment returned, there were no significant differences in these ECG parameters between two groups (All P>0.05). At univariate binary logistic regression analysis QTc dispersion (odds ratio(OR)=1.133; P=0.013), Tp-ec (OR=1.058; P=0.003), Tp-e/QT (OR=1.403; P=0.001), and Tp-ec dispersion (OR=1.497; P=0.004) were significantly associated with MAE. At multivariable logistic regression analysis, Tp-ec dispersion remained a predictor of MAE. Receiver operating characteristic (ROC) curve analysis showed that only AUC (Area under curve) of Tp-ec dispersion had significant difference with those in QTc dispersion (P<0.001), Tp-ec (P=0.003), and Tp-e/QT ratio (P=0.012), respectively.

CONCLUSIONS

QTc dispersion, Tp-ec, Tp-e/QT and Tp-ec dispersion were significantly increased in VA patients with MAE than those without MAE when coronary spasm was onset. Prolonged Tp-ec dispersion was the best discriminators and a strong independent predictor of MAE in VA patients.

Effect of nicorandil on QT dispersion in patients with stable angina pectoris undergoing elective angioplasty: A triple-blind, randomized, placebo-controlled study

Background

Nicorandil leads to the relaxation of fine vascular smooth muscle, and thus causes vasodilatation of major epicardial. Also, it has anti-arrhythmic and cardio-protective effects by improving reperfusion, and ultimately leads to a reduction in microvascular damage caused by percutaneous coronary intervention (PCI).

Objective

The aim of this study was to determine the effect of nicorandil on QT interval dispersion (QTd) in patients with stable angina pectoris during elective angioplasty.

Methods

This triple-blind and randomized clinical trial was performed on patients with stable angina pectoris, candidates for elective angiography referred to Imam Reza and Ghaem hospitals in Mashhad, Iran, between January and October 2016. The patients were randomly assigned to one of two groups receiving nicorandil (60 mg as 20 mg before and 40 mg after PCI) and placebo. All the patients underwent electrocardiography 12 hours before and 12 hours after PCI. The values of maximal corrected QT interval (QTc max) and QTd in these intervals, and the levels of changes in the QTd (QTd difference before angiography and after PCI) were compared between the two groups. Data were analyzed statistically using SPSS version 18 software via Chi-square and Independent-samples t-test.

Results

This study was performed on 90 patients (55 males and 35 females) with a mean age of 58.6±10.8 years, on two groups of 45 people. The two groups were matched for age, body mass index, cardiovascular risk factors and baseline testing. The QTd before angiography had no statistically significant difference between the patients of both groups (control: 77.7±17.1 vs. nicorandil: 80.7±14.2 ms; p=0.371). The QTd after PCI in the nicorandil group was lower than the control group (48.1±14.2 vs. 59.2±15.6 ms; p=0.000). The decrease rate in QTd had a statistically significant difference between the two groups (control: 18.9±11.0 vs. nicorandil: 33.5±9.5 ms; p=0.000).

Conclusions

The results of this study showed that oral administration of nicorandil around the PCI could further reduce QTd following PCI, compared to the control group.

Trial registration

The trial was registered at the Iranian Registry of Clinical Trials (http://www.irct.ir) with the Irct ID: IRCT2016120631159N1

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Life-threatening arrhythmias leading to syncope in patients with vasospastic angina

The coronary artery diseases (CAD) that can lead to the occurrence of a syncopal attack include acute coronary syndrome, vasospastic angina, effort angina, and prior myocardial infarction. The possible mechanisms considered to lead to syncope in patients with CAD are pump failure, tachyarrhythmia, bradycardia, and vagal stimulation. Coronary artery spasm, in particular, is occasionally observed in patients with unexplained syncope in Japan. Life-threatening arrhythmias are among the most serious complications of an ischemic attack caused by coronary spasm, and are associated with an increased risk of syncope and/or sudden cardiac death (SCD). Therefore, during the initial evaluation of unexplained syncope, the diagnosis of vasospastic angina (VSA) needs to be made promptly, to avert the risk of SCD as a consequence of syncope triggered by the lethal arrhythmia. The inducibility of polymorphic ventricular tachycardia or ventricular fibrillation, increased QT dispersion, T-wave alternans, and early repolarization during the asymptomatic period are considered risk markers for ventricular arrhythmias during coronary spasm. In view of the conclusions from several studies, implantable cardioverter/defibrillator therapy should be considered in patients who are at high risk for recurrence of syncope due to a fatal ventricular arrhythmia triggered by coronary spasm, despite appropriate medical therapy.

Morphine Post-Conditioning Effect on QT Dispersion in Patients Undergoing Primary Percutaneous Coronary Intervention on Anterior Descending Cardiac Artery: A Cohort Study

Introduction

QT dispersion is the difference between the maximum and minimum QTc interval in a 12-lead electrocardiogram (ECG). Some researchers have demonstrated the effects of an increase of QT-d in STEMI and its reduction with successful therapy. The aim of this study was to investigate the morphine post-conditioning effect on the QT dispersion in patients undergoing primary percutaneous coronary intervention (PCI) on anterior descending cardiac artery.

Methods

This cohort study was conducted on STEMI patients admitted to the Hospital of Imam Reza (AS), Mashhad, Iran, from March 2015 to February 2016 who were undergoing primary angioplasty on the anterior descending cardiac artery. The patients were divided into two groups based on the intake or non-intake of morphine (5 mg morphine for the period of 30 minutes prior to PCI). Parameters, including age, gender, history of diabetes, and blood pressure as well as admission and 24 hours after PCI ejection fraction (EF) and QT-d, were recorded in all patients and compared between the two intervention and control groups. Independent and paired t-tests and chi-square test were used to compare the qualitative and quantitative data between the two groups using SPSS version 19 software.

Results

The present research was performed on 77 patients (61 males) with mean age of 58.71±11.84 years in the two groups of morphine consumption before PCI (n=46) and control (n=31). No statistical difference was found among the groups in age, gender, diabetes, hypertension, and onset of symptoms until primary PCI. Admission electrocardiogram QT-d value in the positive exposure group showed no significant difference with the control group, but QT-d value at 24 hours after PCI was lower in the positive exposure group than in the control group (morphine versus control: 40.32±6.98 versus 59.64±8.89; p=0.000). QT-d value 24 hours after PCI compared with the admission QT-d value was significantly reduced in both groups. The mean decrease of admission QT-d relative to QT-d 24 hours after PCI was higher in the positive exposure group than in the control group, and this difference was also statistically significant (morphine versus control: 48.65±9.95 versus 25.74±6.66; p=0.000).

Conclusion

The findings of the current survey demonstrated that morphine consumption before PCI can further reduce QT-d value in an electrocardiogram for PCI as compared to patients who did not take morphine before PCI.

Pain frequency, severity and QT dispersion in adult patients with sickle cell anemia: correlation with inflammatory markers

Background

Inflammatory markers are increased during vaso-occlusive crisis (VOC) in adult patients with sickle cell anemia (SCA), but this is not clear in clinical steady state.

Aim

The present study aims to establish the frequency and intensity of bone pain episodes in adult patients with SCA in clinical steady state and to determine the correlation between different inflammatory markers, other variables including QT dispersion (QTd) and pain frequency and intensity in SCA.

Patients and methods

Patients were classified into two groups: group 1, those with more than three hospital admissions in the last 6 months, and group 2, those with no hospital admission. Pearson correlation between variables such as body mass index (BMI), level of tumor necrosis factor (TNF-α), interleukin-1 (IL-1), C-reactive protein (CRP), hemoglobin (Hb), reticulocyte count, white blood cell count (WBC), ferritin, lactate dehydrogenase (LDH), parathormone (PTH), vitamin D3 (25-OH cholecalciferol) and bone pain frequency with severity was evaluated.

Results

Forty-six patients were enrolled in this study with a mean age of 18.47±5.78 years, with 23 patients in each group. Vitamin D3 and Hb were lower (17.04±5.77 vs 37.59±4.83 ng/L, P<0.01 and 7.96±0.3 vs 8.44±0.27 g/dL, P<0.01, respectively); the inflammatory markers showed significantly higher level of TNF-α, IL-1 and CRP (56.52±5.43 pg/ml, 44.17±4.54 pg/ml and 3.20±0.72 mg/L, respectively, P<0.05); WBC, LDH and reticulocyte count were also significantly higher and the QTd was higher (45.0±2.22 vs 41.55±0.8 ms, P<0.05) in group 1 when compared with group 2. Pearson correlation coefficient showed significant positive correlation between serum level of TNF-α and bone pain frequency (r=0.414, P<0.005) and serum level of IL-1 (r=0.39, P<0.008).

Conclusion

There is a strong positive correlation between TNF-α, IL-1 and WBC and bone pain frequency in steady state in adult patients with SCA. CRP and low hemoglobin had weak positive correlation. QTd was significantly longer in patients who had hospitalizations with VOC.

Early repolarization and positive T-wave alternans as risk markers for life-threatening arrhythmias in patients with vasospastic angina

BACKGROUND

Several arrhythmogenic markers have been suggested as predictors for risk of life-threatening arrhythmias during symptom-free periods in vasospastic angina (VSA), but no definite conclusion has been drawn.

OBJECTIVE

To investigate prevalence of fatal ventricular tachyarrhythmia in VSA and its relation to appearance of early repolarization (ER) and positive T wave alternans (p-TWA) in patients with VSA during symptom-free periods.

METHODS

We studied 116 consecutive patients with chest pain who underwent an acetylcholine provocation test for VSA diagnosis. Patients were divided into two groups with positive (VSA group; 66 cases) and negative (control group; 50 cases) provocation test results. The presence of ER on electrocardiogram and the modified moving average analysis of TWA during symptom-free periods were explored.

RESULTS

The incidences of ER and p-TWA were higher in the VSA than in the control group (P=0.001 and P=0.006, respectively). Multivariate analysis revealed that ER and p-TWA were independent predictors of VSA (odds ratio, 5.65 and 4.94; 95% confidence interval: 1.11-28.9 and 1.22-19.9, respectively). The incidence of coexisting baseline ER and p-TWA was significantly higher in VSA patients with life-threatening arrhythmic events (3/3 vs. 6/38; P<0.001) than in those without.

CONCLUSIONS

VSA patients with arrhythmic events showed a high incidence of ER and p-TWA during symptom-free periods. Therefore, baseline ER and p-TWA may help to identify VSA patients at high risk for life-threatening arrhythmias.

Use of QT intervals for a more accurate diagnose of syncope and evaluation of syncope severity

BACKGROUND

This study aimed to evaluate the use of QT intervals, their diagnostic predictive value in patients with syncope and their relationship with syncope severity.

METHODS

One hundred and forty nine patients with a diagnosis of syncope were admitted to Internal Medicine departments at the University of Palermo, Italy, between 2006 and 2012, and 140 control subjects hospitalised for other causes were enrolled. QT maximum, QT minimum, QTpeak, QT corrected, QT dispersion and Tpeak-to-Tend interval were compared between two groups. The paper medical records were used for scoring with San Francisco Syncope Rule (SFSR), Evaluation of Guidelines in SYncope Study (EGSYS) score and Osservatorio Epidemiologico sulla Sincope nel Lazio (OESIL) risk score.

RESULTS

Mean QTc (p < 0.0005), mean QTmax (p < 0.0005), mean QTdisp (p < 0.0005), mean QTpeak (p = 0.005) and mean TpTe (p = 0.018) were significantly longer in patients with syncope compared with control subjects. A QTc > 424.8 ms (sensibility: 81.88 - specificity: 57.86) showed the greatest predictive value for diagnosis of syncope. On the EGSYS score and on the OESIL score, QTc was significantly prolonged in high-risk patients compared with low-risk patients. On the San Francisco Syncope Rule, QTc and QTdisp were significantly prolonged in high-risk patients compared with low-risk patients.

CONCLUSION

Mean QTc, mean QTdisp, mean TpTe, mean QTmax and mean QTpeak were significantly longer in patients with syncope compared with control subjects. Furthermore, prolonged QTc and QTdisp were associated with major severe syncope according to San Francisco Syncope Rule, EGSYS and OESIL risk scores.

Ambulatory electrocardiogram-based T-wave alternans in patients with vasospastic angina during asymptomatic periods

T-wave alternans (TWA) is a useful method for evaluating repolarization abnormalities and as a predictor of life-threatening ventricular arrhythmias. Although life-threatening ventricular arrhythmias are occasionally observed during ischemic attacks in patients with vasospastic angina (VSA), there have been no studies to detect repolarization abnormalities using TWA analysis in these patients during the asymptomatic phase. The aim of this study was to analyze modified moving average (MMA) TWA using Holter recordings in 40 patients with VSA and in 40 control subjects. The incidence of positive TWA was higher in the VSA group than in the control group (24 of 40 [60%] vs 0 of 40 [0%], p <0.01). The value of the maximum MMA TWA was also greater in the VSA group than in the control group (68.6 ± 21 vs 34.0 ± 11 μV, p <0.01). In the VSA group, although there was no significant difference in maximum MMA TWA values between patients with multiple- and single-vessel spasm, patients with ventricular tachycardias had higher values than those without (83.0 ± 15 vs 65.9 ± 20 μV, p <0.05). Patients taking calcium channel blockers exhibited decreased values of maximum MMA TWA compared with subjects not taking these drugs (73.8 ± 18 vs 59.5 ± 21 μV, p <0.05). In conclusion, high values and incidences of TWA events were observed in patients with VSA. In the VSA group, maximum values of MMA TWA were high in patients with ventricular tachycardias but decreased in those taking calcium channel blockers. The results suggest that the patients with VSA during asymptomatic phases exhibit repolarization abnormalities leading to a potential risk for life-threatening arrhythmias.

QTc Interval and QT Dispersion in Patients with Thalassemia Major: Electrocardiographic (EKG) and Echocardiographic Evaluation

Background:

Doppler echocardiographic studies in patients with β-Thalassemia Major (β-TM) had shown different patterns of left ventricle (LV) systolic and diastolic dysfunctions.

Aim:

This cross-sectional study was designed to study the LV systolic and diastolic function in patients with β-TM using Pulsed Doppler (PD) Echocardiogram and assess the QTc interval and QT dispersion (QTd) on 12 leads ECG.

Method:

All patients were evaluated clinically as well as by echocardiography and 12 leads ECG. The study included patients with β-TM (n = 38, age 15.7 ± 8.9 years), compared with an age-matched healthy control group (n = 38, age 15.9 ± 8.9 years).

Results:

In 38 patients with β-TM Compared with healthy control group, The QTc interval and the QTd dispersion on ECG were increased with no significant difference mode echo showed that β-TM patients have thicker LV septal wall index (0.659 ± 0.23 vs. 0.446 ± 0.219 cm/M², P < 0.001), posterior wall index (0.659 ± 0.235 vs. 0.437 ± 0.214 cm/M², P < 0.01), and larger LVEDD index is (3.99 ± 0.48 vs. 2.170 ± 0.57 cm/M². P < 0.05). Pulsed Doppler showed high LV trans-mitral E wave velocity index (70.818 ± 10.139 vs. 57.532 ± 10.139, P < 0.05) and E/A ratio (1.54 vs.1.23, P < 0.01). The duration of deceleration time index (DT) and isovolumic relaxation time index (IVRT) were significantly shorter in patients with β-TM (150.234 ± 20.0.23 vs. 167.123 ± 167.123 ± 19.143 msec/M², P < 0.01) and (60.647 ± 6.77 vs. 75.474 ± 5.83 msec/M², P < 0.001), respectively. The tricuspid valve velocity in patients with β-TM was significantly higher than controls (2.993 ± 0.569 vs. 1.93 ± 0.471 m/sec, respectively, P < 0.01), with calculated pulmonary artery pressure of 2.4 times the control (36.0 vs. 14.8 mmHg). However, the LVEF% or fractional shortening were not significantly different.

Conclusion:

In this study, β-thalassemia major patients compared with controls have differences of QT dispersion and corrected QT interval that is of no statistical significance. A significantly thicker LV wall and LV diastolic filling indices are suggestive of restrictive diastolic pattern. These data indicate that LV diastolic abnormalities compromised initially in patients with β-thalassemia major.

Examination of the microcirculation damage in smokers versus nonsmokers with vasospastic angina pectoris

Endothelial dysfunction is considered one of the mechanisms underlying vasospastic angina pectoris (VSA). It is also known that smokers have abnormalities in endothelial dysfunction. Although smoking is a major risk factor for coronary artery disease, microvascular abnormalities have not been well shown. We investigated clinical characteristics and coronary reactivity with adenosine triphosphate in smokers with VSA. Twenty-two consecutive patients whose coronary spasm was documented in the left anterior descending (LAD) coronary artery with acetylcholine were enrolled. Coronary blood flow responses were also evaluated by intracoronary Doppler flow velocity recordings in the LAD coronary artery. Average peak velocities (APVs) were measured at baseline and intracoronary administration of adenosine triphosphate (50 microg) in 11 smokers (age 60+/-9 years; 8 men) and 11 nonsmokers (age 61+/-10 years, 5 men). Coronary flow reserve (CFR) was calculated by the ratio of baseline to hyperemic APV. Multivessel spasm was demonstrated in 6 smokers and only 2 nonsmokers (p<0.05). APV at rest in smokers (13.4+/-3.0 cm/s) was similar to that in nonsmokers (13.5+/-2.9 cm/s). However, CFR in smokers (2.6+/-0.7) was significantly lower than in nonsmokers (3.4+/-0.8; p<0.05). In conclusion, multivessel spasm was demonstrated in smokers in clinical settings, and microcirculation damage is prominent in smokers with VSA.

Acute reduction of ventricular volume decreases QT interval dispersion in elderly subjects with and without heart failure

To evaluate the effects of acute reduction in ventricular volume (VV) on QT interval dispersion (QTd), 14 men with heart failure (HF; 74.5 ± 2 yr of age) and 11 healthy male control subjects (68 ± 2 yr of age) were studied. For 15 min, lower body negative pressure (LBNP) was applied at −15 and −40 mmHg to reduce venous return. At baseline and during LBNP application, QTd was measured with an 87-lead, body-surface-mapping device; chamber volumes were assessed by radioisotope ventriculography; blood pressure (BP) and heart rate (HR) were continuously monitored; and blood samples were obtained for assessment of norepinephrine (Nor) levels. At −15 mmHg, LNBP application induced a significant decrease in VV but did not change BP and HR in both groups. In addition, Nor levels increased significantly ( P ≤ 0.05) in the control group (from 286.7 ± 31.5 to 388.8 ± 41.2 pg/ml) and in HF patients (from 405.8 ± 56 to 477.6 ± 47 pg/ml), and QTd was significantly ( P ≤ 0.05) decreased in the control group (57.2 ± 3.8 vs. 49.1 ± 3.4 ms) and in HF patients (67.8 ± 6 vs. 63.7 ± 5.9 ms). No additional decreases in VV or QTd were produced by −40 mmHg LNBP, but Nor levels did increase in both groups and reach 475.5 ± 34 and 586.5 ± 60 pg/ml ( P < 0.05) in the control and HF groups, respectively; BP did not change, but HR also increased in both groups. In conclusion, an acute LBNP-induced reduction in VV caused a decrease in the QTd of elderly men regardless of the existence of HF. Because increased sympathetic activity with more intense LBNP was not accompanied by additional changes in QTd, altered QTd may be better related to changes in VV than to autonomic nervous system activity.

Opening of K(ATP) channel attenuates the increase in QT dispersion produced by the first balloon inflation during coronary angioplasty

Increased QT dispersion predicts the occurrence of lethal ventricular arrhythmias complicating percutaneous transluminal coronary angioplasty (PTCA). Moreover, these arrhythmias occur more frequently at the first balloon inflation. Activation of the K(ATP) channel may influence QT dispersion and ventricular arrhythmias during coronary angioplasty, so 40 consecutive patients with stable angina were randomized to receive 3 mg/h of nicorandil infusion or placebo and QT dispersion and the incidence of ventricular ectopy were investigated before and throughout PTCA. There were no significant differences in QT dispersion at baseline between the nicorandil group (42+/-8 ms) and placebo (42+/-12ms). At the first balloon inflation, the QT dispersion in the nicorandil group (51+/-13 ms) was significantly less than that observed with placebo (76+/-16ms, p<0.001). However, the QT dispersion at the second inflation was similar in both groups (nicorandil: 45+/-12ms; placebo: 52+/-14ms). Ventricular ectopy was observed in 1 patient receiving nicorandil and 5 patients in the placebo group during the first inflation, and none in the nicorandil and 1 patient in the placebo group during the second balloon inflation. Activation of the K(ATP) channel may inhibit the development of ventricular arrhythmias during PTCA, particularly at the first balloon inflation.

Polymorphic ventricular tachycardia in patients with vasospastic angina--clinical and electrocardiographic characteristics and long-term outcome

There have been few clinical studies exploring the characteristics of spontaneous polymorphic ventricular tachycardia (VT) during a vasospastic angina attack. During a 4-year recruitment period, Holter ECG recordings were monitored for 42+/-24 h during a drug-free period in 60 consecutive patients with vasospastic angina (VSA) and of these, 8 patients had at least one episode of polymorphic VT during monitoring. Ischemic ST segment elevation was immediately preceded the spontaneous polymorphic VT in all 8 patients, 4 of whom had silent coronary vasospasm. Immediately before the onset of polymorphic VT, both R-on-T and long-short sequences were observed in 4 of the 8 patients and ST wave alternans were recorded in 2 patients. VT exhibited a pattern of torsade de pointes in 4 of the 8 patients. Five patients underwent electrophysiologic testing during a drug-free asymptomatic phase, and polymorphic VT was induced in 2 of the 5 patients, with one developing ventricular fibrillation. During a follow-up period of 73+/-17 months, there was a significant difference in the incidence of sudden death between patients with and without VT (2/8 cases [25%] vs 0/52 [0%]; p<0.01). Thus, vasospastic attacks, even if asymptomatic, that immediately precede the development of polymorphic VT may be associated with a repolarization abnormality and an increased risk of sudden death.

Measurement, interpretation and clinical potential of QT dispersion

QT dispersion was originally proposed to measure spatial dispersion of ventricular recovery times. Later, it was shown that QT dispersion does not directly reflect the dispersion of recovery times and that it results mainly from variations in the T loop morphology and the error of QT measurement. The reliability of both automatic and manual measurement of QT dispersion is low and significantly lower than that of the QT interval. The measurement error is of the order of the differences between different patient groups. The agreement between automatic and manual measurement is poor. There is little to choose between various QT dispersion indices, as well as between different lead systems for their measurement. Reported values of QT dispersion vary widely, e.g., normal values from 10 to 71 ms. Although QT dispersion is increased in cardiac patients compared with healthy subjects and prognostic value of QT dispersion has been reported, values are largely overlapping, both between healthy subjects and cardiac patients and between patients with and without adverse outcome. In reality, QT dispersion is a crude and approximate measure of abnormality of the complete course of repolarization. Probably only grossly abnormal values (e.g. > or =100 ms), outside the range of measurement error may potentially have practical value by pointing to a grossly abnormal repolarization. Efforts should be directed toward established as well as new methods for assessment and quantification of repolarization abnormalities, such as principal component analysis of the T wave, T loop descriptors, and T wave morphology and wavefront direction descriptors.