QT dispersion as a predictor of long-term mortality in patients with acute myocardial infarction and clinical evidence of heart failure

Prognostic Value of QTc Dispersion in Acute Myocardial Infarction

Introduction Acute myocardial infarction (AMI) is linked to an increased risk of sudden cardiac death (SCD), with malignant ventricular arrhythmias, sustained ventricular tachycardia (VT) and ventricular fibrillation (VF), complicating STEMI (ST-segment elevation myocardial infarction) cases and accounting for a significant proportion of in-hospital SCDs. While advanced risk stratification techniques such as the GRACE (Global Registry of Acute Coronary Events) score depend on laboratory biomarkers and complex algorithms, their need for specialized equipment limits widespread use. Corrected QT (QTc) dispersion (QTd), the difference between the longest and shortest QT intervals on a 12-lead ECG, provides a simple alternative for assessing ventricular repolarization heterogeneity and predicting arrhythmic risk in AMI patients. Previous studies have assessed QTd in AMI populations, reporting associations with ventricular arrhythmias and mortality. However, the definition and measurement of QTd are subject to variability, with controversies surrounding manual versus automated measurement, correction formulas, and ECG lead selection, resulting in reported inter- and intra-observer variability. Methods A prospective observational study was conducted in an emergency and cardiac care setting, enrolling patients diagnosed with STEMI who underwent reperfusion therapy. Demographic data, clinical presentation, and medical history were recorded. Serial 12-lead ECGs were obtained at three time points: admission, post-reperfusion, and 24 hours later. QT intervals were measured manually using calipers, and the QTc interval was calculated using Bazett's formula. QTd was calculated as the difference between maximum and minimum QTc values across the ECG leads. To assess inter-observer variability, a randomly selected subset of ECGs was re-measured by a second cardiologist, and the intraclass correlation coefficient (ICC) was used to quantify agreement. Data analysis was performed using statistical software. Results The study population had a mean age of approximately 61 years, with a majority being male. QTd was significantly elevated in anterior wall myocardial infarction (AWMI) patients, with mean QTd values of 98.96 ± 2.95 ms at admission compared to 85.08 ± 17.02 ms in non-AWMI patients (p < 0.0001), particularly at admission and post-reperfusion. Inferior wall myocardial infarction (IWMI) patients exhibited an initial increase in QTd, which significantly reduced after reperfusion. Posterior wall myocardial infarction (PWMI) patients showed consistently lower QTd across all time points. While this was interpreted as correlating with fewer arrhythmic events, the study did not present actual data on arrhythmia frequency by infarct location. This lack of direct event correlation limits the strength of QTd as a prognostic marker. No significant variations were observed based on comorbidities. Conclusion QTd serves as a useful prognostic marker in AMI. Elevated QTd at admission is linked to a higher arrhythmic risk, particularly in AWMI. A reduction in QTd post-reperfusion supports its potential role in assessing therapeutic effectiveness. Routine QTd measurement may enhance risk stratification and inform clinical decision-making in AMI patients.

Clinical phenotypes in acute and chronic infarction explained through human ventricular electromechanical modelling and simulations

Sudden death after myocardial infarction (MI) is associated with electrophysiological heterogeneities and ionic current remodelling. Low ejection fraction (EF) is used in risk stratification, but its mechanistic links with pro-arrhythmic heterogeneities are unknown. We aim to provide mechanistic explanations of clinical phenotypes in acute and chronic MI, from ionic current remodelling to ECG and EF, using human electromechanical modelling and simulation to augment experimental and clinical investigations. A human ventricular electromechanical modelling and simulation framework is constructed and validated with rich experimental and clinical datasets, incorporating varying degrees of ionic current remodelling as reported in literature. In acute MI, T-wave inversion and Brugada phenocopy were explained by conduction abnormality and local action potential prolongation in the border zone. In chronic MI, upright tall T-waves highlight large repolarisation dispersion between the border and remote zones, which promoted ectopic propagation at fast pacing. Post-MI EF at resting heart rate was not sensitive to the extent of repolarisation heterogeneity and the risk of repolarisation abnormalities at fast pacing. T-wave and QT abnormalities are better indicators of repolarisation heterogeneities than EF in post-MI.

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.

COVID-19 and arrhythmia: The factors associated and the role of myocardial electrical impulse propagation. An observational study based on cardiac telemetric monitoring

Background

The heart is commonly involved in COVID-19, and rhythm disorders have been largely reported.

Objective

To evaluate the association of some non-cardiac and cardiac comorbidities and QT dispersion with arrhythmias and their impact on outcomes in hospitalized patients with COVID-19.

Methods

Each patient underwent cardiac telemetry monitoring through the entire hospitalization period, laboratory analyses, 12-lead ECG, and lung imaging examination. Patients with arrhythmia were divided into three groups (bradyarrhythmias, tachyarrhythmias, and tachy- and bradyarrhythmias).

Results

Two-hundred patients completed the study (males, 123; mean age, 70.1 years); of these, 80 patients (40%) exhibited rhythm disorders on telemetry. Patients with arrhythmia were older (p &lt; 0.0001), had a greater number of comorbidities (p &lt; 0.0001), higher values of creatinine (p = 0.007), B-type natriuretic peptide (p &lt; 0.0001), troponin (p &lt; 0.0001), C-reactive protein (p = 0.01), ferritin (p = 0.001), D-dimer (p &lt; 0.0001), procalcitonin (p = 0.0008), QT interval (p = 0.002), QTc interval (p = 0.04), and QTc dispersion (p = 0.01), and lower values of sodium (p = 0.03), magnesium (p = 0.04), glomerular filtration rate (p &lt; 0.0001), and hemoglobin (p = 0.008) as compared to patients without arrhythmia. By comparing the three subgroups of patients, no significant differences were found. At multivariate analysis, age [odds ratio (OR) = 1.14 (95% CI: 1.07–1.22); p = 0.0004], coronary artery disease [OR = 12.7 (95% CI: 2.38–68.01); p = 0.005], and circulating troponin [OR = 1.05 (95% CI: 1.003–1.10); p = 0.04] represented risk factors independently associated with arrhythmia. All-cause in-hospital mortality was ∼40-fold higher among patients with arrhythmia [OR = 39.66 (95% CI: 5.20–302.51); p = 0.0004].

Conclusion

Arrhythmias are associated with aging, coronary artery disease, subtle myocardial injury, hyperinflammatory status, coagulative unbalance, and prolonged QTc dispersion in patients with COVID-19, and confer a worse in-hospital prognosis. Given its usefulness, routinary use of cardiac telemetry should be encouraged in COVID wards.

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.

Association of QT dispersion with mortality and arrhythmic events-A meta-analysis of observational studies

BACKGROUND

The risk stratification of coronary heart disease (CHD) and/or heart failure (HF) patients with easily measured electrocardiographic markers is of clinical importance. The aim of this meta-analysis is to indicate whether increased QT dispersion (QTd) is associated with fatal and nonfatal outcomes in patients with CHD and/or HF.

METHODS

We systematically searched MEDLINE and Cochrane databases without restrictions until August 15, 2018 using the keyword "QT dispersion". Studies including data on the association between QTd and all-cause mortality, sudden cardiac death (SCD) or arrhythmic events in patients with HF and/or CHD were classified as eligible.

RESULTS

In the analysis including patients with CHD and/or HF, we found that QTd did not differ significantly in patients with SCD compared to no SCD patients while QTd was significantly greater in the group of all-cause mortality patients and in patients who experienced a sustained ventricular arrhythmia. Subgroup analysis showed that in myocardial infarction studies, QTd was significantly higher in patients with an arrhythmic event compared to arrhythmic event-free patients while a nonsignificant difference was found in QTd in patients who died from any cause compared to survivors. Similarly, in HF patients, the QTd was significantly greater in patients with an arrhythmic event while a nonsignificant difference was found regarding all-cause mortality and SCD outcomes.

CONCLUSIONS

QTd has a prognostic role for stratifying myocardial infarction or HF patients who are at higher risk of arrhythmic events. However, no prognostic role was found regarding all-cause mortality or SCD in this patient population.

Increased QT Interval Dispersion is Associated with Coronary Artery Involvement in Children with Kawasaki Disease

Objectives

Coronary artery (CA) involvement is the most well known complication of Kawasaki disease (KD). Previous studies have suggested that QT dispersion has a predictive value in diagnosing cardiac ischemia, ventricular arrhythmia, and sudden cardiac death. However, limited data exits regarding the application of QT dispersion in KD. Therefore, we sought to determine whether there is a relationship between QT dispersion and CA involvement in patients with KD.

Methods

We performed a cross-sectional study of all consecutive patients with KD who were followed-up at the Pediatric Rheumatology Department (Pediatrics Center of Excellence affiliated to Tehran University of Medical Sciences, Tehran, Iran) from September 2013 to November 2015. Patients who met the criteria for KD, based on the American Heart Association guideline, were enrolled in the study. We collected data regarding patients' demographics, clinical manifestations, laboratory, and echocardiographic findings.

Results

A total of 70 KD patients were identified, including 43 males (61.4%) and 27 females (38.6%). The median age of patients was 21.0 (11.0-48.0) months. We found statistically significant differences between age, gender, and platelet count among patients with and without CA involvement (p < 0.050). Median corrected QT dispersion in patients with CA involvement calculated from 12 leads in the acute phase was significantly higher compared to the non-CA involvement group (108.0 (89.5-138.5) ms vs. 63.0 (54.0-74.5) ms, respectively (p < 0.001)).

Conclusions

Prolonged QT dispersion (corrected or non-corrected) during the acute and convalescence phases in patients with KD is associated with coronary involvement.

Determinants of cardiac repolarization and risk for ventricular arrhythmias during mild therapeutic hypothermia

PURPOSE

We aimed to investigate the factors that modulate the extent of QTc prolongation and potential arrhythmogenic consequences during mild therapeutic hypothermia (MTH).

METHODS

We studied 205 patients after out-of-hospital cardiac arrest (131 underwent MTH). QTc was measured at baseline, 3h, 6h, 12h, 24h (end of hypothermia), 48h and 72h, and ventricular arrhythmias quantified.

RESULTS

During MTH, the QTc interval increased progressively peaking at 12h (mean increase 42ms, 95% CI 30-55). There was a strong gender effect (P<0.001) and a significant gender-by-MTH interaction (P=0.004). At 12h, the QTc interval was markedly longer in women as compared with men (mean difference 50ms [95% CI 27-73]. Anoxic brain injury (P=0.002) was also positively associated with QTc prolongation. The risk for ventricular arrhythmic events was not higher with MTH compared with no hypothermia (incidence rate ratio 0.57, 95% CI 0.32-1.02, P=0.06). However, typical cases of Torsade de pointes occurred in association with AV block and LQT2.

CONCLUSION

QTc prolongation during MTH is strongly affected by female gender and moderately by concomitant anoxic brain injury. Although the overall risk for ventricular arrhythmias is not greater with MTH, Torsade de pointes may develop when other contributing factors coexist.

Improvement of increased cQTd is associated with heart function in patients with ischemic heart failure

Background

Chronic heart failure (CHF) is life-threatening without timely or effective intervention. In this study, we investigated the association between QT dispersion corrected for heart rate (cQTd) and heart function in patients with CHF.

Methods

From January 2013 to December 2015, we continuously enrolled 240 patients categorized as New York Heart Association functional class (NYHA) III-IV with a left ventricular ejection fraction (LVEF) < 40%. Based on the etiology, the patients were divided into a dilated cardiomyopathy (DCM) group (n = 120) and an ischemic cardiomyopathy (ICM) group (n = 120). Then, based on the cQTd width, the ICM group was divided into two subgroups: a QS group (cQTd ≤ 60 ms, n = 70) and a QL group (cQTd > 60 ms, n = 50). All patients were examined by echocardiography and 12-lead electrocardiography (ECG) at 1, 3, 6, and 12 months after enrollment.

Results

After one year of optimized medical treatment, patients in both groups showed significant improvement in LVEF and NYHA classification from baseline. However, the cQTd in the ICM group, especially the QL, was significantly shorter than that in the DCM group at each time point. In addition, the cQTd was negatively correlated with LVEF and 6-min walking test and positively correlated with NYHA class in the ICM group.

Conclusions

The present findings clearly demonstrate that cQTd is a meaningful parameter for assessing heart function in the follow-up of ICM patients.

QT Indexes in Cirrhotic Patients: Relationship with Clinical Variables and Potential Diagnostic Predictive Value

BACKGROUND AND AIMS

A wide spectrum of cardiovascular changes characterizes cirrhosis, ranging from subclinical alterations to hyperkinetic syndrome. We looked for ECG markers of ventricular repolarization in a population of patients with cirrhosis in comparison to patients without cirrhosis and we investigated the relationship between these and other clinical and laboratory variables.

METHODS

In 149 patients with cirrhosis and 152 controls, we measured QT maximum interval (QTmax), QT corrected interval (QTc), QT minimum interval (QTmin), QT dispersion (QTdisp), QT peak and T peak-to-end (TpTe).

RESULTS

In subjects with cirrhosis, in comparison with controls, we observed a higher mean QTmax, mean QTc, mean QTmin, mean QTdisp and mean TpTe. At Cox regression analysis, diastolic blood pressure and beta-blocker treatment were significantly associated with mean QTmax, hypertension with mean QTmin and mean QTc, diastolic blood pressure, beta-blockers and ACE-inhibitors/ARBs with QT disp, and beta-blockers with TpTe. Analysis of ROC curves showed a significant area under curve towards cirrhosis diagnosis, respectively, for a cut-off value of > 400 msec of QTmax, > 360 msec of QTmin, > 450 msec of QTc, > 105 msec of TpTe and > 55 msec of QTdisp.

CONCLUSIONS

Our study shows that QT indexes are altered in cirrhotic patients and have a potential diagnostic predictive value.

ECG in patients with acute heart failure can predict in-hospital and long-term mortality

Initial risk stratification in patients with acute heart failure (AHF) is poorly validated. Previous studies tended to evaluate the prognostic significance of only one or two selected ECG parameters. The aim of this study was to evaluate the impact of multiple ECG parameters on mortality in AHF. The Acute Heart Failure Database (AHEAD) registry collected data from 4,153 patients admitted for AHF to seven hospitals with Catheter Laboratory facilities. Clinical variables, heart rate, duration of QRS, QT and QTC intervals, type of rhythm and ST-T segment changes on admission were collected in a web-based database. 12.7 % patients died during hospitalisation, the remainder were discharged and followed for a median of 16.2 months. The most important parameters were a prolonged QRS and a junctional rhythm, which independently predict both in-hospital mortality [QRS > 100 ms, odds ratio (OR) 1.329, 95 % CI 1.052-1.680; junctional rhythm, OR 3.715, 95 % CI 1.748-7.896] and long-term mortality (QRS > 120 ms, OR 1.428, 95 % CI 1.160-1.757; junctional rhythm, OR 2.629, 95 % CI 1.538-4.496). Increased hospitalisation mortality is predicted by ST segment elevation (OR 1.771, 95 % CI 1.383-2.269) and prolonged QTC interval >475 ms (OR 1.483, 95 % CI 1.016-2.164). Presence of atrial fibrillation and bundle branch block is associated with increased unadjusted long-term mortality, but mostly reflects more advanced heart disease, and their predictive significance is attenuated in the multivariate analysis. ECG in patients admitted for acute heart failure carries significant short- and long-term prognostic information, and should be carefully evaluated.

Selection of patient for cardiac resynchronization therapy: role of QT corrected dispersion

AIMS

About 30 to 50% of patients undergoing cardiac resynchronization therapy (CRT) may not show clinical or echocardiographic improvement, despite fulfilling guidelines recommendations for CRT. For this reason, we need a more accurate method to assess CRT eligibility. The aims of this study were to verify, on a 12-month follow-up, the usefulness of QT corrected dispersion (QTcD) in a patient's selection for CRT.

METHODS

We stratified 53 patients who underwent CRT, into two groups based on the estimation of QTcD, that is, QTcD > 60 ms and QTcD ≤ 60 ms. In all patients were performed New York Heart Association (NYHA) class determination, six-minute walking test, QtcD, and QRS measurements, and complete echocardiographic assessment at 1, 3, 6, and 12 months after implantation.

RESULTS

At baseline, there were no significant differences in clinical, echocardiographic, and electrocardiographic parameters duration between two groups. At 12-month follow-up between the two groups, there were significant differences in NYHA (1.2 ± 0.4 vs 2 ± 0.6; P < 0.01), six-minute walking distance (422 ± 68 vs 364 ± 68; P < 0.01), left ventricular (LV) ejection fraction (34 ± 7% vs 28 ± 6%; P < 0.01), LV end-diastolic diameter (57 ± 7 vs 63 ± 8; P < 0.01), and LV intraventricular dyssynchrony (24 ± 14 vs 39 ± 23; P < 0.01).

CONCLUSION

This study suggests that QTc dispersion in addition to QRS duration could improve the sensitivity of electrocardiogram in a patient's selection for CRT.

QTc prolongation is associated with impaired right ventricular function and predicts mortality in pulmonary hypertension

BACKGROUND

In rodent models of pulmonary hypertension (PH) and right ventricular hypertrophy (RVH), the QTc interval is prolonged, reflecting downregulation of repolarizing Kv channels in RV myocytes. The significance of QTc prolongation in human PH is unknown. We hypothesized that QTc prolongation occurs in human PH, is associated with RVH and decreased RV function, and predicts adverse prognosis.

METHODS

Patients receiving a PAH-specific therapy (a prostanoid, endothelin-receptor antagonist and/or a phosphodiesterase-5 inhibitor), who had a 12-lead electrocardiogram (ECG) (n=202) were compared to age- and sex-matched controls (n=100). The duration of QTc on ECG was correlated with invasive hemodynamics (n=156) and with the status of the RV, as measured by Brain Natriuretic Peptide (NT-proBNP, n=145) and magnetic resonance imaging (n=24). Survival of the entire PH cohort and a subgroup with WHO Groups 1 and 4 PAH was prospectively determined from the Social Security Death Index.

RESULTS

QTc intervals were longer in PH vs. controls (454.8 ± 29 ms vs. 429.8 ± 18 ms, p<0.001) and did not differ based on PAH-specific therapy. NT-proBNP increased proportionately with QTc and was higher for those in the upper quintile (QTc ≥ 480 ms) vs. those with QTc<480 ms (4004 ± 6682 pg/mL vs. 1501 ± 1822 pg/mL, p<0.001). The QTc interval also correlated directly with increasing RV end-diastolic volume (r=.67, p<0.001) and mass (r=.0.51, p<0.05), and inversely with RV ejection fraction (r=-.49, p<0.05). In the entire PH cohort and WHO Groups 1 and 4 subgroup, QTc ≥ 480 ms and cardiac index were independent predictors of mortality.

CONCLUSIONS

QTc prolongation in PH patients reflects the status of the RV and is an independent predictor of mortality.

Electrocardiogram-based predictors of sudden cardiac death in patients with coronary artery disease

Current recommendations on which patients with coronary artery disease (CAD) should be offered an implantable cardioverter defibrillator for the primary prevention of sudden cardiac death (SCD) rely heavily on the presence of depressed left ventricular ejection fraction. Because the majority of SCD victims with CAD have preserved left ventricular function, additional cardiac investigations are likely to play an increasing role in the risk stratification of CAD patients. A number of studies have demonstrated that certain parameters on the traditional 12-lead electrocardiogram (ECG) and other ECG-based investigations (such as signal-averaged ECG, heart rate turbulence, T-wave alternans) can provide important information on the underlying cardiac substrate abnormality that may predispose to ventricular arrhythmias and SCD. This article reviews some of the evidence for these ECG-based tests as predictors of SCD in patients with CAD and addresses their advantages and limitations.

Intermediate-term effects of transcatheter secundum atrial septal defect closure on cardiac remodeling in children and adults

The study aimed to investigate the intermediate-term effects of transcatheter atrial septal defect (ASD) closure on cardiac remodeling in children and adult patients. Between December 2003 and February 2009, 117 patients (48 males, 50 adults) underwent transcatheter ASD closure with the Amplatzer septal occluder (ASO). The mean age of the patients was 15 years, and the mean follow-up period was 25.9 +/- 12.4 months. New York Heart Association (NYHA) class, electrocardiographic parameters, and transthoracic echocardiographic (TTE) examination were evaluated before the ASD closure, then 1 day, 1 month, 6 months, 12 months, and yearly afterward. Transcatheter ASD closure was successfully performed for 112 (96%) of the 117 patients. The mean ASD diameter measured by transesophageal echocardiography (TEE) was 14.0 +/- 4.2 mm, and the mean diameter stretched with a sizing balloon was 16.6 +/- 4.8 mm. The mean size of the implanted device was 18.6 +/- 4.9 mm. The Qp/Qs ratio was 2.2 +/- 0.8. The mean systolic pulmonary artery pressure was 40 +/- 10 mmHg. At the end of the mean follow-up period of 2 years, the indexed right ventricular (RV) end-diastolic diameter had decreased from 36 +/- 5 to 30 +/- 5 mm/m(2) (p = 0.005), and the indexed left ventricular (LV) end-diastolic diameter had increased from 33 +/- 5 to 37 +/- 6 mm/m(2) (p = 0.001), resulting in an RV/LV ratio decreased from 1.1 +/- 0.2 to 0.8 +/- 0.2 (p = 0.001). The New York Heart Association (NYHA) functional capacity of the patients was improved significantly 24 months after ASD closure (1.9 +/- 0.5 to 1.3 +/- 0.5; p = 0.001). At the 2-year follow up electrocardiographic examination, the P maximum had decreased from 128 +/- 15 to 102 +/- 12 ms (p = 0.001), the P dispersion had decreased from 48 +/- 11 to 36 +/- 9 ms (p = 0.001), and the QT dispersion had decreased from 66 +/- 11 to 54 +/- 8 ms (p = 0.001). Five of six patients experienced resolution of their preclosure arrhythmias, whereas the remaining patient continued to have paroxysmal atrial fibrillation. A new arrhythmia (supraventricular tachycardia) developed in one patient and was well controlled medically. Transcatheter ASD closure leads to a significant improvement in clinical status and heart cavity dimensions in adults and children, as shown by intermediate-term follow-up evaluation. Transcatheter ASD closure can reverse electrical and mechanical changes in atrial myocardium, resulting in a subsequent reduction in P maximum and P dispersion times.

Association of corrected QT dispersion with symptoms improvement in patients receiving cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is theoretically expected to affect repolarization as well as depolarization. We studied the effects of CRT on corrected QT (QTc) dispersion in association with symptomatic improvement. QTc dispersion was analyzed in 26 consecutive patients (67 +/- 6 years old, 18 men and 8 women) who underwent CRT. CRT responders and nonresponders were defined as patients showing and not showing > or = 1 class New York Heart Association symptomatic improvement 3 months after CRT, respectively. QTc interval, QRS width, and QTc dispersion were measured automatically from digital data using an analyzing system. There were 18 CRT responders and 8 nonresponders among the patients. CRT responders showed significantly larger QTc dispersion than CRT nonresponders before CRT (102 +/- 26 vs 40 +/- 12 ms, P < 0.01). A significant decrease in QTc dispersion by CRT was observed in responders (102 +/- 26 to 52 +/- 15 ms, P < 0.01). In contrast, QTc dispersion was not decreased by CRT in nonresponders (40 +/- 12 to 39 +/- 11 ms, not significant). The difference observed before CRT was thus abolished after CRT (52 +/- 15 vs 39 +/- 11 ms, not significant). Baseline values and changes in QRS width or QTc, as well as asynchrony of wall motion determined by tissue Doppler imaging, were not different between CRT responders and nonresponders before CRT. The present study with a small number of patients shows the potential utility of QTc dispersion for distinguishing CRT responders from CRT nonresponders before CRT, and warrants further study with a greater number of patients.

Coronary calcium score from multislice computed tomography correlates with QT dispersion and left ventricular wall thickness

Coronary calcium score is a marker of coronary atherosclerosis and is an important factor of cardiac events. Ventricular hypertrophy and QT dispersion increase the risk of cardiac events. The purpose of the study was to investigate whether coronary calcium score may be related to the changes of QT, QT dispersion, heart chamber size, and wall thickness. The coronary calcium score was studied in 97 patients through multislice computed tomography (MSCT). There were 32 patients with high calcium score (> or =200), 29 patients with low calcium score (1-199), and 36 patients with zero calcium score. The gender, age, incidence of hypertension, diabetics, smoking, and dyslipidemia were similar among the three groups. The QT dispersion, QTc dispersion, and R-wave amplitude in the high calcium score group were larger than those in the other two groups. There were similar P-wave duration. QRS duration, and PR interval among the three groups. The left ventricular anterior-posterior diameter and left ventricular wall thickness in the high coronary calcium score group were larger than those in the other two groups. Coronary calcium score had strong correlations with QT dispersion and left ventricular wall thickness. These findings may contribute further evidence regarding the increased risk of cardiac events in those patients with high coronary calcium score.

The electrocardiogram as a prognostic tool for predicting major cardiac events

Among patients with cardiac disease, the identification of those who are at low risk and those who are at high risk for major cardiac events is crucial for a rational clinical management of individual patients. A correct noninvasive risk stratification of cardiac patients, in particular, has relevant clinical implications because it would avoid unnecessary exposure to potentially risky invasive diagnostic or interventional procedures in low-risk patients, whereas it would allow an appropriate aggressive diagnostic and therapeutic approach in high-risk patients. Furthermore, the appropriate identification of low- and high-risk patients would also have social and economic implications by favoring optimization of resource distribution and costs. A large number of studies in previous decades provided evidence that several methods and variables derived from the analysis of the electrocardiogram (ECG) are powerful predictors of major cardiac events in several clinical conditions. Despite that, there has been limited attention about how several of these findings can be used in clinical practice. Furthermore, in recent years, most studies about risk stratification of cardiac patients have mainly been focused on the use of a number of serum/plasma biomarkers with reduced attention to ECG variables. Surprisingly, however, there have been few attempts to establish whether the various proposed risk markers add any significant information to that obtainable from ECG methods. In this article, the evidence for the prognostic value of variables derived from the assessment of the ECG signal by several methods and techniques will be briefly reviewed. Because of the largeness of the topic, this review will be necessarily incomplete. Because most of the clinical research in this field concerned risk stratification of patients with coronary artery disease, the article will be largely focused on this population of patients. The role of ECG methods in specific cardiac diseases and, in particular, in the general population of asymptomatic subjects will be briefly discussed when believed appropriate and helpful. Furthermore, only major clinical events (ie, cardiac death, arrhythmic events, acute myocardial infarction) will be taken into account as end points in this article. Minor clinical events (eg, coronary revascularization procedures, coronary artery restenosis, recurrences of symptoms) are indeed less robust as end points because they are widely biased by subjective judgments.

QT dispersion and prognosis after coronary stent placement in acute myocardial infarction

BACKGROUND

QT dispersion is increased in acute myocardial infarction (AMI), but the relation of QT dispersion to prognosis has not yet been fully elucidated.

HYPOTHESIS

The purpose of this study is to evaluate prospectively whether QT dispersion is associated with the risk of major adverse cardiac events (MACEs) and mortality after successful coronary stenting in AMI.

METHODS

One hundred and forty-two patients with AMI and undergoing successful percutaneous coronary intervention (PCI) were enrolled in this study. Corrected QT dispersion was measured before and 24 h after PCI.

RESULTS

During a period of 4477 person-months, we confirmed 21 cases of MACE. Univariate analysis indicated that corrected QT dispersion before and 24 h after PCI, age, number of Q waves, and Killip class > or = 2 were related to MACE and mortality. By multivariate analysis, corrected QT dispersion before PCI was an independent predictor of MACE and mortality, but corrected QT dispersion at 24 h after PCI was not statistically associated with MACE and mortality. Multiple-adjusted hazard ratios for a 1 standard deviation (SD) magnitude increase in corrected QT dispersion before PCI were 2.24 (95% confidence interval, 1.36-3.68, p = 0.001) for MACE and 2.71 (95% confidence interval, 1.50-4.89, >) for mortality after adjustment for age, gender, ejection fraction, and Killip class > or = 2.

CONCLUSIONS

Corrected QT dispersion before PCI is associated with an increased risk of MACE and mortality after successful PCI in patients with AMI.

Identifying heart failure patients at high risk for near-term cardiovascular events with serial health status assessments

BACKGROUND

Identification of heart failure outpatients at increased risk for clinical deterioration remains a critical challenge, with few tools currently available to assist clinicians. We tested whether serial health status assessments with the Kansas City Cardiomyopathy Questionnaire (KCCQ) can identify patients at increased risk for mortality and hospitalization.

METHODS AND RESULTS

We evaluated 1358 patients with heart failure after an acute myocardial infarction in the Eplerenone's Neurohormonal Efficacy and Survival Study, a multicenter randomized trial that included serial KCCQ assessments. Cox proportional-hazards models were used to examine whether changes in KCCQ scores during successive outpatient visits were independently associated with all-cause mortality and cardiovascular mortality or hospitalization. Change in KCCQ (deltaKCCQ) was linearly associated with all-cause mortality (hazard ratio [HR], for each 5-point decrease in deltaKCCQ, 1.11; 95% CI, 1.04 to 1.19) and the combined outcome of cardiovascular mortality or hospitalization (HR for each 5-point decrease in deltaKCCQ, 1.12; 95% CI 1.07 to 1.18). In Kaplan-Meier survival analysis, all-cause mortality among patients with deltaKCCQ of < or = -10, > -10 to < 10, and > 10 points was 26%, 16%, and 13%, respectively (P=0.008). After multivariable adjustment, the linear relationship between deltaKCCQ and both all-cause mortality and combined cardiovascular death and hospitalization persisted (HR, 1.09; 95% CI, 1.00 to 1.18; and HR, 1.11; 95% CI, 1.05 to 1.17 for each 5-point decrease in deltaKCCQ, respectively).

CONCLUSIONS

In heart failure outpatients, serial health status assessments with the KCCQ can identify high-risk patients and may prove useful in directing the frequency of follow-up and the intensity of treatment.

QRS and QTc interval prolongation in the prediction of long-term mortality of patients with acute destabilised heart failure

OBJECTIVES

To quantify the prognostic utility of QRS and QTc interval prolongation in patients presenting with acute destabilised heart failure (ADHF) to the emergency department (ED).

DESIGN

Prospective cohort study among patients enrolled in the B-Type Natriuretic Peptide for Acute Shortness of Breath Evaluation (BASEL) study. QRS and QT intervals were measured in 173 consecutive patients with ADHF. QT interval was corrected using the Bazett formula. The primary end point was all-cause mortality during the 720-day follow-up.

RESULTS

QRS interval was prolonged (> or =120 ms) in 27% of patients, and QTc interval was prolonged (> or =440 ms) in 72% of patients. Baseline demographic and clinical characteristics were comparable in patients with normal and prolonged QRS or QTc intervals. A total of 78 patients died during follow-up. Interestingly, the 720-day mortality was similar in patients with prolonged and normal QTc (44% vs 42%, p = 0.546), but was significantly higher in patients with prolonged QRS interval than in those with normal QRS (59% vs 37%, p = 0.004). In Cox proportional hazards analysis, prolonged QRS interval was associated with a nearly twofold increase in mortality (HR 1.94, 95% CI 1.22 to 3.07; p = 0.005). This association persisted after adjustment for variables routinely available in the ED.

CONCLUSIONS

Prolonged QRS interval, but not prolonged QTc interval, is associated with increased long-term mortality in patients with ADHF.

The prognostic value of QTc interval and QT dispersion following myocardial infarction in patients treated with or without dofetilide

BACKGROUND

Acute myocardial infarction (MI) is associated with an increased risk of death, with a 1-year mortality close to 10% in patients discharged from hospital alive. During the first year following MI, close to 50% of deaths are assumed to be due to arrhythmic events.

HYPOTHESIS

The study was undertaken to determine the interaction between dofetilide treatment and pretreatment QTc interval and QT dispersion regarding mortality in patients with left ventricular (LV) dysfunction and a recent MI.

METHODS

The study population consisted of 894 patients with a recent MI and LV systolic dysfunction, who were randomized to receive dofetilide or placebo. The study was a substudy of the Danish Investigations of Arrhythmia and Mortality on Dofetilide-MI (DIAMOND-MI).

RESULTS

During a minimum of 1-year follow-up, 261 (29%) patients died. Baseline QTc interval did not hold any prognostic value on mortality for placebo-treated patients. When pretreatment QTc interval was <429 ms, dofetilide resulted in a 45% reduction of mortality (hazard ratio 0.55, 95% confidence limits 0.34-0.88, p<0.02) compared with placebo. When QTc interval was >429 ms, dofetilide did not influence mortality significantly. This study revealed no statistically significant relation between QT dispersion, dofetilide treatment, and mortality.

CONCLUSION

In patients with a recent MI, LV dysfunction, and a short baseline QTc interval, dofetilide is associated with significant survival benefit. This benefit is not seen with a longer QTc interval. QT dispersion is not a risk factor in this population.

The immediate and short-term effect of successful percutaneous coronary intervention on repolarization in acute myocardial infarction patients

OBJECTIVES

The primary objective was to assess the immediate and short-term impact of successful percutaneous coronary intervention (PCI) on QT dispersion (QT disp) and corrected QT dispersion (QTc disp). Secondarily, the impact of PCI on QT and QTc disp within different infarct-related arteries and the impact of successful PCI in these different arteries were evaluated.

METHODS

Patients (n = 140, age 61.6 +/- 12.9, 69% male) undergoing direct primary PCI for acute MI were evaluated. Twelve-lead ECGs were obtained before (baseline), immediately after (0 h), 24hours after, and 3 days after PCI. The QT and QTc interval in each of the 12-leads were measured and the shortest interval was subtracted from the longest to derive the QT disp and QTc disp, respectively.

RESULTS

Angiography showed blockages in the left anterior descending, right coronary artery, and circumflex in 37.1, 48.9, and 15.0% of patients, respectively. Overall, 97 patients achieved successful reflow. QT and QTc disp were significantly improved in the group with successful reflow at each follow-up time after PCI versus baseline and corresponding values in the unsuccessful reflow group. QT disp was improved among patients with successful reflow irrespective of which infarct artery was responsible for the acute myocardial infarction.

CONCLUSIONS

Successful reflow with PCI is associated with a rapid reduction in QT disp and QTc disp that is maintained for at least 3 days after the event. Conversely, unsuccessful reflow was not associated with significant reductions in QT or QTc disp.

Role of shortened QTc dispersion in in-hospital cardiac events in patients undergoing percutaneous coronary intervention for acute coronary syndrome

BACKGROUND

QT dispersion (QTD) refers to the difference between maximal and minimal QT values on the electrocardiogram (ECG). QTD values are calculated and corrected with Bazett's formula (corrected QTD = QTcD = QTD/square root of RR). QTcD increases in patients with acute coronary syndrome (ACS). Recovery of increased QTcD (shortened QTcD) develops after successful revascularization, but prolonged QTcD occurs in certain patients. The aim of this study is to ascertain the clinical significance between shortened and prolonged QTcD groups after percutaneous coronary intervention (PCI).

METHODS

We retrospectively enrolled 128 patients with ACS who had received PCI. The values of QTcD were measured manually on 12-lead standard ECGs obtained within 3 days before and after PCI (pre-PCI QTcD and post-PCI QTcD). All the patients were divided into 2 groups. The shortened QTcD group was defined as those patients with a decrease in QTcD after PCI and the prolonged QTcD group as those with an increase in QTcD after PCI. The underlying diseases, various clinical classifications and some prognostic factors were taken into comparison and statistical analysis between these 2 groups.

RESULTS

The shortened QTcD group showed a significantly higher rate of in-hospital cardiac death (13% vs. 0%, p = 0.006) and a greater pre-PCI QTcD (100.8 +/- 39.5 vs. 61.3 +/- 24.1 ms, p < 0.001) than the prolonged QTcD group. There was a significantly greater pre-PCI QTcD in patients with cardiac death than those without cardiac death (111.6 +/- 38.3 vs. 83.3 +/- 38.3ms, p = 0.027). Furthermore, the patients with in-hospital cardiac death presented with a significantly more frequent occurrence of in-hospital ventricular arrhythmia, compared with those without cardiac death (30.0% vs. 4.0%, p = 0.014).

CONCLUSION

Among the patients with ACS undergoing PCI, directly divided into shortened and prolonged QTcD groups regardless of initial pre-PCI QTcD, the shortened QTcD group showed a higher occurrence of in-hospital cardiac death and a greater pre-PCI QTcD. Shortened QTcD might be 1 risk factor for in-hospital cardiac death.

QT dispersion is determined by the relative extent of normal, hibernating, and scarred myocardium in patients with chronic ischemic cardiomyopathy. A dobutamine stress echocardiography study before and after surgical revascularization

INTRODUCTION

The aim of the present study was to evaluate a possible association between QT dispersion (QTd) and the amount of viable and scarred myocardial tissue after revascularization in patients with coronary artery disease and impaired left ventricular (LV) function.

METHODS

Twenty-two patients with ischemic LV dysfunction underwent dobutamine stress echocardiography (DSE) before and 6 months after surgical revascularization. Mean corrected QT-interval value and QTd were calculated at baseline and follow-up. Segments consisting of transmural scar were determined as the segments that remained akinetic in all stages of DSE despite reperfusion. Patients were divided into 2 groups according to the number of definitive segments consisting of transmural scar (minor scar group, < or =2 scarred segments; major scar group, >2 scarred segments).

RESULTS

QTd was significantly lower in the minor compared with the major scar group at baseline and follow-up (mean [SD], 61 [22] vs 98 [33] milliseconds, P = .008, and 45 [18] vs 68 [21] milliseconds, P = .01, respectively). Segments consisting of transmural scar positively correlated to QTd at baseline (r = 0.53, P = .01) and follow-up (r = 0.62, P = .002).

CONCLUSIONS

QTd is positively correlated with the extent of scarred myocardial tissue assessed by DSE. Surgical revascularization results in reduction of QTd in all patients with hibernating myocardium and LV dysfunction.

Genetics of acquired long QT syndrome

The QT interval is the electrocardiographic manifestation of ventricular repolarization, is variable under physiologic conditions, and is measurably prolonged by many drugs. Rarely, however, individuals with normal base-line intervals may display exaggerated QT interval prolongation, and the potentially fatal polymorphic ventricular tachycardia torsade de pointes, with drugs or other environmental stressors such as heart block or heart failure. This review summarizes the molecular and cellular mechanisms underlying this acquired or drug-induced form of long QT syndrome, describes approaches to the analysis of a role for DNA variants in the mediation of individual susceptibility, and proposes that these concepts may be generalizable to common acquired arrhythmias.

QT dispersion failed to estimate the global dispersion of ventricular repolarization measured using monophasic action potential mapping technique in swine and patients

The aim of this study was to evaluate whether the QT dispersion measured from 12-lead electrocardiogram (ECG) can estimate the global dispersion of ventricular repolarization (DVR) measured using a monophasic action potential (MAP) mapping technique. Monophasic action potentials were recorded from 75 +/- 12 left ventricular sites in 10 pigs and from 48 +/- 16 left or right ventricular sites in 15 patients using the CARTO mapping system. The maximum DVRs in both end-of-repolarization and MAP duration among all the mapped sites were calculated and termed as global DVR for each measurement. QT intervals, QT peak and QT end , were measured from the 12-lead ECG, and QT dispersions; namely the differences between the maximum and the minimum of the QT peak and QT end were calculated. We found that QT dispersions were significantly smaller than (P < .05) and poorly correlated with the global DVRs both in pigs and patients. Bland-Altman agreement analysis demonstrated a marked variation of the differences and an obvious lack of agreement between the results obtained using the ECG and the MAP methods. In our patients, the global DVR increased markedly during ventricular tachycardia as compared with that during sinus rhythm (P < .05), whereas there was no significant difference in QT dispersion between these 2 subgroups. In conclusion, QT dispersion on the surface ECG could not estimate the global DVR measured using the MAP mapping technique. These findings are not consistent with some previously reported observations, suggesting the need for reappraisal of the electrophysiological implications of QT dispersion.

Effect of coronary artery bypass grafting and aneurysmectomy on QT dispersion in moderate or severe left ventricular dysfunction

BACKGROUND

The aim of the study was to evaluate the effect that coronary artery bypass grafting (CABG) and aneurysmectomy in the same session have on QT dispersion (QTd) in moderate or severe left ventricular dysfunction.

METHODS

Forty-four patients underwent QT interval analyses before and 1 month after aneurysmectomy and CABG. QT interval and QTd were corrected for heart rate using the square root formula of Bazett (QTCB), the cubic root formula of Fridericia (QTCF), and the linear formula of Sagie et al (QT CS ).

RESULTS

The mean pre- and postsurgery QTd results were 65.29 +/- 29.25 and 51.76 +/- 18.49 milliseconds, respectively; the corresponding findings for QT CF were 68.06 +/- 31.26 and 55.16 +/- 24.56 milliseconds; and the corresponding findings for QT CS were 66.53 +/- 32.22 and 51.10 +/- 18.29 milliseconds. With these 3 methods, the postoperative findings were significantly lower than the preoperative findings ( P < .05 for all). In contrast, the opposite was true with the QT CB method (preoperative 71.1 +/- 65.80 vs postoperative 76.43 +/- 7.96 milliseconds, P < .05).

CONCLUSION

The study showed that based on the methods of Fridericia (QT CF ) and Sagie et al (QT CS ), QT intervals are significantly decreased after CABG and aneurysmectomy.

Principal Component Analysis of the T Wave in Patients with Chest Pain and Conduction Disturbances

There is a need for markers reflecting the increased risk in patients with conduction disturbances. Conduction disturbances presumably cause inhomogeneous repolarization that may create an arrhythmogenic substrate. In patients with normal conduction, parameters derived from principal components analysis (PCA) of the T wave contain prognostic information. The nondipolar PCA components are assumed to reflect repolarization inhomogeneity. This study examined the PCA parameters in relation to conduction disturbances. PCA was performed on continuously recorded 12-lead ECGs in 800 patients with chest pain and nondiagnostic ECG on admission. The patients with conduction disturbance on admission were classified into separate groups and related to comparison groups without conduction disturbance recruited from the same series. For each patient, the dipolar and nondipolar components were quantified by medians of the ratio of the two largest eigenvalues (S2/S1 Median), the residue that summarizes the eigenvalues S4-S8 (TWRabsMedian) and the ratio of this residue to the total power of the T wave (TWRrelMedian). The parameters were assessed with respect to common clinical and ECG parameters, discharge diagnosis, and total mortality during a 35-month follow-up. TWRabsMedian increased with increasing conduction disturbance. In 135 patients with conduction disturbances, ROC curves for TWRabsMedian as indicator of mortality exhibited areas under a curve of 0.66, 0.65, and 0.56 at 6-month, 24-month, and 35-month follow-up. Conduction disturbances were associated with increased nondipolar PCA component and, thus, with increased repolarization inhomogeneity. The nondipolar PCA component contained a moderate amount of prognostic information not present in a simple ECG diagnosis of a conduction disturbance.

QT interval dispersion analysis in patients undergoing left partial ventriculectomy (Batista operation)

BACKGROUND

QT interval dispersion (QTd) has been valued as a marker of increased vulnerability for cardiac arrhythmias. QTd was analyzed in patients undergoing the left partial ventriculectomy (LPV) or Batista operation, a palliative surgery for patients in the line for heart transplantation, which is associated with complex arrhythmia and death from sustained ventricular tachyarrhythmia (SVT).

METHODS

Pre- and postoperative R-R, QT, QTc, JT (QT - QRS), and aT (apex to end of T wave) intervals were obtained by 87-lead body surface mapping from 24 patients (18 male), mean age 46.4 +/- 9.15 years. Dispersions of QT, QTc, JT, and aT intervals were calculated, and the total number of arrhythmic events were assessed, aiming to verify a possible risk predictor for the occurrence of SVTs. Subgroups of patients who survived and who died after LPV were also compared, aiming to obtain a QTd cutoff value that could be used prognostically.

RESULTS

No difference between pre- and postoperative mean values were found, but a very significant difference was seen when comparing QTd and QTcD values for surviving and dead patients: QTd, cutoff value was 95 ms, while QTcD value was 114 ms.

CONCLUSION

There were no significant differences between pre- and postoperative variables or the number of arrhythmic events, but there were significant differences between both pre- and postoperative QTd and QTcD data from surviving and dead patients; this enabled the determination of cutoff values that we believe may be useful for the prognosis of the LPV outcome.

Influence of i.v. haloperidol on ventricular repolarization and monophasic action potential duration in anesthetized dogs

INTRODUCTION

i.v. haloperidol is used commonly for sedation in critically ill patients. However, i.v. haloperidol has been shown to cause the life-threatening ventricular tachyarrhythmia torsades de pointes. Mechanisms by which haloperidol causes torsades de pointes have not been widely investigated in controlled studies.

STUDY OBJECTIVES

To determine the effects of i.v. haloperidol on electrophysiologic parameters known to promote torsades de pointes.

INTERVENTIONS

Monophasic action potential catheters were guided under fluoroscopy into the right and left ventricles of 14 chloralose-anesthetized dogs (haloperidol, nine dogs; placebo, five dogs). Effective refractory period (ERP), action potential duration at 90% repolarization (APD90), and QTc interval measurements were performed at baseline and after each of four doses of haloperidol (0.15, 0.5, 2.0, and 3.0 mg/kg) or placebo at three different pacing cycle lengths (450, 300, and 250 ms).

MEASUREMENTS AND RESULTS

i.v. haloperidol significantly prolonged left and right ventricular ERP by a magnitude of 12 to 20% at all pacing cycle lengths. ERP values in the placebo group did not change significantly from pretreatment values in either ventricle. Haloperidol significantly prolonged left ventricular APD90 at a pacing cycle length of 300 ms. The effects of haloperidol on right ventricular APD90 approached significance at a cycle length of 450 ms. Overall, haloperidol prolonged APD90 by 7 to 11%, with less consistent and more variable effects than those for the ERP. APD90 was not significantly altered in the placebo groups. Haloperidol produced significant prolongation in QTc intervals. The electrophysiologic effects of haloperidol were related to dose, with a plateau reached at the 0.5 mg/kg dose for ERP measurements and at the 2 mg/kg dose for the APD90 and QTc interval measurements.

CONCLUSIONS

i.v. haloperidol prolongs ventricular ERP and APD90 in intact canine hearts. These electrophysiologic effects are likely associated with the clinical torsades de pointes-inducing actions of i.v. haloperidol in critically ill patients.

Right lateral decubitus position reduces QT dispersion in patients with chronic heart failure

A greater QT dispersion in patients with chronic heart failure (CHF) appears to be a non-invasive marker of susceptibility to malignant ventricular arrhythmias. We evaluated whether QT dispersion in CHF patients is modified by the patients' recumbent position. In 12 CHF patients, and age and sex-matched 12 normal subjects, a single 12-lead surface ECG was recorded in each postural position [left lateral decubitus position (L), supine position (S), and right lateral decubitus position (R)]. In normal subjects, the QT dispersion was comparable in the three recumbent positions [L: 47+/-15 (SD) ms, S: 40+/-9 ms, R: 38+/-14 ms, P=NS]. In contrast, in CHF patients, QT dispersion was significantly shorter in R than those in L and S (L: 93+/-42 ms*, S: 81+/-29 ms*, R: 63+/-24 ms, *P <.05 vs. R). In conclusion, reclining in R reduces the prolonged QT dispersion in CHF patients.

QT dispersion correlates with systolic rather than diastolic parameters in patients receiving anthracycline treatment

OBJECTIVE

The aim of this study was to investigate the relation of QT dispersion to left ventricular (LV) systolic and diastolic function in patients undergoing anthracycline therapy.

METHODS

We used echocardiography to evaluate LV systolic and diastolic function and electrocardiography to evaluate QT dispersion and corrected QT dispersion (QTcD) in patients with hematological diseases, who received anthracycline therapy.

PATIENTS

Seventy-two patients with hematological diseases who were receiving anthracycline treatment were enrolled in the present study.

RESULTS

LV end-diastolic diameter or LV end-systolic diameter had a significant positive correlation to QTcD (r = 0.35, p < 0.01, r = 0.43, p < 0.01). Also left ventricular ejection fraction of (LVEF) or fractional shortening had a significant negative correlation to QTcD (r = -0.46, p < 0.001, r = -0.27, p = 0.02). The highest QTcD group had a significantly larger LV end-diastolic diameter or LV end-systolic diameter than the lowest QTcD [48.5 +/- 5.7 vs. 44.4 +/- 4.5 (mm), p < 0.001, 34.1 +/- 6.4 vs. 28.8 +/- 4.3 (mm), p < 0.001] and the highest QTcD group had a significantly lower LVEF than the lowest QTcD [57.5 +/- 8.0 vs. 65.5 +/- 6.4 (%), p < 0.001]. On the other hand, none of the diastolic function markers were significantly correlated with QTcD.

CONCLUSION

We concluded that increased QTcD is correlated with LV dilation and systolic dysfunction induced by anthracycline therapy, and does not reflect a dispersion of ventricular repolarization or asynchronous motion.

Correlation between dispersion of repolarization (QT dispersion) and ventricular ectopic beat frequency in patients with acute myocardial infarction: a marker for risk of arrhythmogenesis?

BACKGROUND

QT dispersion (QTd) has evoked a lot of interest in recent years as regards the basic concept of dispersion of repolarization, which it is supposed to reflect on a surface ECG, as being a marker or substrate for arrhythmogenesis. QTd has been shown to be high in patients with ventricular fibrillation and tachycardia. But there is still some debate about its possible role as a marker or substrate for arrhythmogenesis. We studied whether it has any correlation with simple benign ventricular ectopic beats (VEB) after acute myocardial infarction.

STUDY

We studied four different dispersion parameters (QTd, QTcd, JTcd, AQTd) on 2 different days after AMI and also obtained a 24-h ambulatory ECG on the 2nd day after admission in 64 out of a total of 90 patients. Patients were divided into five groups based on VEB frequency/h on a 24-h ambulatory ECG.

RESULTS

We found a gradual increase in dispersion parameters across the five groups with increasing frequency of VEB. A significant difference was noticed between group 1 (VEB 0.0-0.9/h) and group V (>30/h) on the day of admission: QTd 88.8+/-28.5 versus 123.3+/-23.4, P<0.02; QTcd 100.5+/-27.6 versus 160.3+/-30.7, P<0.01; JTcd 95.5+/-31.0 versus 160.4+/-30.9, P<0.01; AQTd 29.6+/-8.2 versus 48.6+/-13.7, P<0.01. We also noticed a significant positive correlation between VEB frequency and dispersion parameters on both days.

CONCLUSION

We hypothesize that with increasing dispersion of repolarization the chances or the frequency of ventricular arrhythmias increase. Our findings also point to a definite role of QTd as an arrhythmogenic marker or substrate.

Multivariate associates of QT interval parameters in diabetic patients with arterial hypertension: importance of left ventricular mass and geometric patterns

The aim of the study was to assess the determinants of increased QT interval parameters in diabetic patients with arterial hypertension and, in particular, the strength of their relationships to echocardiographically derived left ventricular mass (LVM) and geometric patterns. In a cross-sectional study with 289 hypertensive type 2 diabetic outpatients, maximal QT and QTc (heart rate-corrected) intervals, and QT, QTc, and number-of-leads-adjusted QT interval dispersions were manually measured from standard baseline 12-lead ECGs. Electrocardiographic criteria for left ventricular hypertrophy (LVH) were either Sokolow-Lyon or Cornell sex-specific voltages. LVM and geometric patterns were determined by 2D echocardiography. Statistical analyses involved bivariate tests (Mann-Whitney, chi2, Spearman's correlation coefficients, ANOVA and receiver-operating-characteristic (ROC) curve analyses) and multivariate tests (multiple linear and logistic regressions). QT dispersion measurements showed significant correlations with echocardiographic LVM (r=0.26-0.27). ROC curves demonstrated a poor isolated predictive performance of all QT parameters for detection of LVH (areas under curve: 0.58-0.59), comparable to that of electrocardiographic voltage criteria. Only patients with concentric hypertrophy had significantly increased QT dispersion (QTd) when compared to those with normal geometries (64.24+/-21.09 vs 53.20+/-15.35, P<0.05). In multivariate analyses, both electrocardiographic and echocardiographic LVH were independent predictors of increased QTd, as well as only QTd and gender were determinants of LVM. In conclusion, increased QT interval dispersion is associated with LVM and concentric hypertrophy geometric pattern in diabetic hypertensive patients, although in isolation neither QTd nor any QT parameter presents enough predictive performance to be recommended as screening procedures for detection of LVH.

Prognostic value of QT interval parameters for mortality risk stratification in Chagas' disease: results of a long-term follow-up study

BACKGROUND

QT interval parameters are potential prognostic markers of arrhythmogenicity risk and cardiovascular mortality and have never been evaluated in Chagas' disease.

METHODS AND RESULTS

Outpatients (738) in the chronic phase of Chagas' disease were enrolled in a long-term follow-up study. Maximal heart rate-corrected QT (QTc) and T-wave peak-to-end (TpTe) intervals and QRS, QT, JT, QTapex, and TpTe dispersions and variation coefficients were measured manually and calculated from 12-lead ECGs obtained on admission. Clinical, radiological, and 2-dimensional echocardiographic data were also recorded. Primary end points were all-cause, Chagas' disease-related, and sudden cardiac mortalities. During a follow-up of 58+/-39 months, 62 patients died, 54 of Chagas' disease-related causes and 40 suddenly. Multivariate Cox survival analysis revealed that the QT-interval dispersion (QTd) (hazard ratio, 1.45; 95% confidence interval, 1.29 to 1.63; P<0.001, for 10-ms increments) and left ventricular (LV) end-systolic dimension (hazard ratio, 1.36; 95% confidence interval, 1.21 to 1.53; P<0.001, for 5-mm increments) were the strongest independent predictors for all end points. The maximum QTc interval (QTcmax) could substitute for QTd with a worse predictive performance. Other predictors were heart rate, presence of pathological Q waves, frequent premature ventricular contractions (PVCs), and isolated left anterior fascicular block (LAFB) on the ECGs. Kaplan-Meier survival curves demonstrated that a QTd > or =65 ms or a QTcmax > or =465 ms1/2 discriminated the 2 groups with significantly different prognoses.

CONCLUSIONS

Electrocardiographic QTd and echocardiographic LV end-systolic dimension were the most important mortality predictors in patients with Chagas' disease. Heart rate, the presence on ECG of pathological Q waves, frequent PVCs, and isolated LAFB refined the mortality risk stratification.

Imaging electrocardiographic dispersion of depolarization and repolarization during ischemia: simultaneous body surface and epicardial mapping

BACKGROUND

Myocardial ischemia creates abnormal electrophysiological substrates that result in life-threatening ventricular arrhythmias. Identifying patients at risk of such abnormalities by use of body surface electrical measures is controversial. We investigated the sensitivity of torso measures, recorded simultaneously with epicardial electrograms, to changes in dispersion of depolarization and repolarization during localized ventricular ischemia.

METHODS AND RESULTS

Ventricular epicardial electrograms were recorded from 5 anesthetized pigs with a 127-electrode sock. A controllable suture snare was used to ligate the left anterior descending coronary artery (LAD). The chest was reclosed, and a vest with 256 ECG electrodes was fitted to the torso. Simultaneous arrays of epicardial electrograms and torso ECGs were recorded during LAD occlusion and reperfusion. Activation-recovery intervals (ARIs), QTu and RTu dispersion (where u indicates upstroke), and QRST integrals were calculated, and these data were fitted to anatomically customized computational models of the swine ventricular epicardium and torso. LAD occlusion caused the epicardial ARI dispersion to steadily increase, whereas the location of shortest ARI shifted from the posterobasal ventricular tissue (control) to the anteroapical myocardium, distal to the suture snare. These changes were associated with a steady increase in the torso RTu dispersion as the shortest RTu interval moved from the right shoulder (control) to the sternum. QTu and RTu dispersion determined from the 12-lead ECG did not consistently reflect the myocardial changes.

CONCLUSIONS

Although changes in myocardial repolarization dispersion resulting from localized ischemia are not reliably reflected in temporal indices derived from the 12-lead ECG, they can be readily identified with high-resolution torso ECG mapping.

Prolonged QTc interval and high B-type natriuretic peptide levels together predict mortality in patients with advanced heart failure

BACKGROUND

The role of QTc interval prolongation in heart failure remains poorly defined. To better understand it, we analyzed the QTc interval duration in patients with heart failure with high B-type natriuretic peptide (BNP) levels and analyzed the combined prognostic impact of prolonged QTc and elevated BNP.

METHODS AND RESULTS

QTc intervals were measured in 241 patients with heart failure who had BNP levels >400 pg/mL. QT interval duration was determined by averaging 3 consecutive beats through leads II and V4 on a standard 12-lead ECG and corrected by using the Bazett formula. QTc intervals were prolonged (>440 ms) in 122 (51%) patients and normal in 119 (49%). The BNP levels in these 2 groups were not significantly different (786+/-321 pg/mL in the prolonged QTc group versus 733+/-274 pg/mL in the normal QTc group, P=0.13). During 6 months of follow-up, 46 patients died, 9 underwent transplantation, and 17 underwent left ventricular assist device implantation. The deaths were attributed to pump failure (n=24, 52%), sudden cardiac death (n=18, 39%), or noncardiac causes (n=4, 9%). Kaplan-Meier survival rates were 3 times higher in the normal QTc group than in the prolonged QTc group (P<0.0001). On multivariate analysis, prolonged QTc interval was an independent predictor of all-cause death (P=0.0001), cardiac death (P=0.0001), sudden cardiac death (P=0.004), and pump failure death (P=0.0006).

CONCLUSIONS

Prolonged QTc interval is a strong, independent predictor of adverse outcome in patients with heart failure with BNP levels >400 pg/mL.

QT dispersion has no prognostic value in patients with symptomatic heart failure: an ELITE II substudy

This study prospectively investigated 3,118 standard 12-lead ECGs recorded in 1,804 patients, who participated in the Losartan Heart Failure Survival Study--ELITE II clinical trial. After exclusion of patients with rhythms other than sinus, or atrioventricular block, or poor quality ECGs, 986 (703 men, mean age 71 +/- 7 years) with baseline ECGs were retained, of whom 615 patients had follow-up ECGs 4 months after randomization. QT intervals were manually measured with a digitizing board. Heart rate, QRS duration, maximum QT and JT intervals, QT and JT dispersion (the interval ranges across all measurable ECG leads) were analyzed. In the overall population, there were 140 (14%) deaths from all causes, including 119 (12%) cardiac and 59 (6%) sudden deaths during a follow-up of 540 +/- 153 days. The mean heart rate was significantly faster in nonsurvivors than in survivors (77 +/- 16 vs 74 +/- 14 beats/min, P = 0.006), and in patients who died of cardiac death (76 +/- 16 beats/min, P = 0.04 vs survivors). Mean QRS duration was significantly longer in nonsurvivors (107 +/- 25 ms), and in the subgroups who died of cardiac (107 +/- 24 ms) or sudden death (112 +/- 23 ms) than in survivors (99 +/- 24 ms, P < 0.01 for all). The maximum and corrected (QTc) QT intervals were similar for nonsurvivors, regardless of cause of death, and in survivors (P = NS for all comparisons). Significantly shorter maximum and corrected (JTc) JT intervals were observed in victims of any mode of death compared to survivors (P < 0.05 for all). There was no significant difference in QT or JT dispersion between patients with any mode of death and survivors (P > 0.1 for all). Neither losartan nor captopril significantly modified QT or JT dispersion. In conclusion, increased QT dispersion is not associated with increased mortality in patients with heart failure, and is not suitable to examine drug efficacy in these patients.

Monitoring of cardiac function by serum cardiac troponin T levels, ventricular repolarisation indices, and echocardiography after conditioning with fractionated total body irradiation and high-dose cyclophosphamide

OBJECTIVES

Highly differing rates of cardiac complications associated with high-dose cyclophosphamide (CY) have been reported, and only one clinical study has been performed on the cardiotoxic effects of CY monotherapy following total body irradiation (TBI).

PATIENTS AND METHODS

We prospectively evaluated the potential cardiotoxic effects of conditioning with fractionated total body irradiation and high-dose cyclophosphamide (TBI/CY) by serial measurement of serum cardiac troponin T (cTnT), assessment of systolic and diastolic echocardiographic parameters and analysis of ventricular repolarisation indices (QT-dispersion and corrected QT-dispersion) in 30 adult patients with haematological malignancies undergoing haematopoietic stem cell transplantation.

RESULTS

There was no evidence of pretreatment cardiac dysfunction in any patient. Although cTnT was determined serially for a median of 14 d after completion of conditioning, no elevated levels were observed. Echocardiographic parameters did not show any significant change at a median follow-up of 5 months except for one patient with evidence of impaired diastolic filling. No significant differences for mean values before and after high-dose CY were noted for ventricular repolarisation indices. Two patients had a significant increase in corrected QT-dispersion after CY without any other signs of cardiotoxicity. Congestive heart failure or arrhythmias were not observed.

CONCLUSIONS

These data suggest that TBI/CY is safe with respect to cardiotoxicity in patients without pre-existing cardiac dysfunction. Hitherto unknown synergistic cardiotoxic effects of CY with other cytostatic drugs may constitute the major pathogenic factor of myocardial dysfunction after high-dose chemotherapy.

QT dispersion measured by an automatic continuous method early in patients admitted for chest pain

BACKGROUND

There is a need for risk markers in patients with acute chest pain. QT dispersion (QTd) is a prognostic marker in several groups of patients. A problem with the manual measurement of QTd is operator dependency. This can be avoided by using an automatic method. We investigated QTd, derived from multiple automatic measurements, as a risk marker in a population with chest pain.

METHODS

In 548 patients admitted to the coronary care unit for chest pain and nondiagnostic ECG, 12-lead ECG recordings were collected each minute during the initial 17 h. From recordings with > or =10 valid leads, mean QTd (QTdMean), QTd in the first satisfactory recording and estimates of variability of QTd were computed and correlated to outcome.

RESULTS

In the group with QTdMean > or =40 ms (n=277), 10 patients died during the initial 30 days; one patient died in the group with QTdMean <40 ms (n=271) (P=0.07). During follow-up (median 6 months), 19 vs. five patients died in each group (P=0.03). The figures for the triple endpoint death/myocardial infarction/revascularisation were 52 vs. 27 events during the initial 30 days (P=0.018) and 76 vs. 41 events during follow-up (P=0.003). QTd in the first recording did not predict new cardiac events.

CONCLUSIONS

QTd measured as the mean value of multiple recordings was found to be a powerful marker for cardiac events during follow-up. It was superior to the analysis of QTd in a single ECG. It can be used for the selection of low-risk patients, but was not effective in identifying high-risk patients.

Relation of early changes of QT dispersion to changes in left ventricular systolic and diastolic function after a first acute myocardial infarction

OBJECTIVE

To describe the relation between changes of left ventricular systolic and diastolic function and changes of QT dispersion (difference in duration between longest and shortest QT interval) following acute myocardial infarction.

DESIGN

QT dispersion was determined at admission, hospital discharge, and 1 and 3 months following myocardial infarction in 64 consecutive 1-year survivors. Patients were divided into Group A where QT dispersion was < 52 ms at all recordings or initially > 52 ms but decreased during follow-up, and Group B where QT dispersion remained increased > or = 52 ms at all measurements. Doppler-Echocardiography was carried out on day 1, day 5, and after 1, 3, and 12 months.

RESULTS

In 26 patients QT dispersion remained increased > or = 52 ms during the first 3 months after infarction. Among these a significant increase of end-systolic volume was seen whereas low or rapid normalized QT dispersion was associated with a significant decrease of ventricular volumes. After 1 year end-systolic (70 +/- 32 ml vs 49 +/- 16 ml, p = 0.006) and end-diastolic volumes (138 +/- 41 ml vs 105 +/- 22 ml, p = 0.001) were higher in Group B. In a multivariate model Group B was significantly related to an increase of end-diastolic volume (p = 0.01). In Group A diastolic function improved in eight patients and in two it deteriorated, whereas improvement was seen in one patient and deterioration in nine patients from Group B (p < 0.01).

CONCLUSION

Following myocardial infarction low QT dispersion is associated with preserved left ventricular function, whereas persistently increased dispersion is associated with left ventricular dilation and deterioration of diastolic function.

Investigation of QT-interval dispersion in the electrocardiogram of 81 dogs

QT-interval dispersion (QT dispersion) is a marker of the inhomogeneity of ventricular repolarisation. In human beings an increase in QT dispersion has been linked to sudden death and arrhythmias in several cardiac diseases. In dogs it has yet to be evaluated, and this study aimed to establish a normal reference range for QT dispersion and to assess the effects of cardiac disease upon it. Ten-lead ECGS were recorded from 81 dogs at two hospitals; satisfactory traces were obtained from 68 dogs, 32 of them normal and 36 with cardiac disease. The mean (sd) QT dispersion was 20.8 (18.2 ms) and the mean heart rate-corrected QT dispersion was 26.1 (23.6 ms). There was no significant effect of cardiac disease. The accuracy of the results may be questioned owing to the identification of several potential errors in the measurements.

Increased QTc dispersion and mortality in uremic patients with acute myocardial infarction

QT dispersion (the difference between maximum and minimum QT across the 12-lead electrocardiogram [ECG]), which reflects regional variations in ventricular repolarization, is a predictor of arrhythmia and cardiovascular mortality. The present study was undertaken to assess the difference in QT dispersion between uremic and nonuremic patients with acute myocardial infarction (AMI) and its relationship to post-AMI clinical outcome. Twelve-lead ECG recordings were obtained the first and third days after the onset of AMI in 21 uremic and 21 nonuremic patients. QT intervals were measured on 12-lead ECGs and corrected by heart rate (QTc). Our findings show that uremic patients with AMI had greater QTc dispersion (84 +/- 35 versus 55 +/- 15 milliseconds; P < 0.001), a greater 1-year mortality rate (48% versus 18%; P = 0.003), and underwent fewer reperfusion therapies (5 of 21 versus 17 of 21 patients; P = 0.002) compared with nonuremic patients with AMI. Patients with AMI who died had greater QTc dispersion than those who survived (102 +/- 40 versus 67 +/- 40 milliseconds; P = 0.015). An optimal QTc dispersion cutoff value of 60 milliseconds had a sensitivity of 100% and specificity of 55% in predicting 1-year mortality in uremic patients with AMI. Uremic patients with AMI administered thrombolytic therapies (n = 5) had reduced 1-year mortality rates (0% versus 63%; P = 0.003) and shortened QTc dispersion from days 1 to 3 (changes in QTc dispersion between days 1 and 3, 29% +/- 9% decrease versus 13% +/- 5% increase; P = 0.001) compared with those without therapies (n = 16). Our findings suggest that greater QT dispersion is associated with greater total mortality, and thrombolytic therapies could reduce QTc dispersion and mortality in uremic patients with AMI. It is prudent to refine our current management regimen for uremic patients with AMI to improve the poor clinical outcome.

Calmodulin inhibitor W-7 unmasks a novel electrocardiographic parameter that predicts initiation of torsade de pointes

BACKGROUND

We have shown that the calmodulin inhibitor W-7 suppresses torsade de pointes (TdP) without shortening the QT interval, which is consistent with other findings that QT prolongation, per se, is insufficient to generate TdP. ECGs were analyzed from a well-characterized animal model of TdP to identify more reliable predictors of this life-threatening ventricular arrhythmia.

METHODS AND RESULTS

TdP was induced using methoxamine and clofilium in 12 of 14 rabbits pretreated with vehicle control, whereas pretreatment with W-7 (50 micromol/kg), an inhibitor of the intracellular Ca2+-binding protein calmodulin, significantly suppressed TdP induction (1 of 11 rabbits with TdP, P<0.001). W-7 did not affect heart rate, increases in QT intervals, or dispersion compared with measurements in vehicle-treated control animals. However, a progressive and significant increase in the ratio of U-wave to T-wave amplitude (UTA) occurred before TdP onset in control animals, and this was prevented by W-7.

CONCLUSIONS

Selective suppression of TdP inducibility by W-7, without shortening the duration of cardiac repolarization, allowed identification of the UTA ratio as a new electrocardiographic index for predicting TdP onset. These findings are consistent with the idea that prolonged repolarization is not the proximate cause of arrhythmia initiation, and they suggest that an increased UTA ratio reflects activation of intracellular Ca2+/calmodulin-dependent processes that are required for triggering TdP in this model.

A Benefit-Risk Assessment of Class III Antiarrhythmic Agents

With beta-blockers as the exception, increasing doubt is emerging on the value of antiarrhythmic drug therapy following a series of trials that have either shown no mortality benefit or even an excess mortality. Vaughan Williams class I drugs are generally avoided in patients with structural heart disease, and class IV drugs are avoided in heart failure. Unfortunately, arrhythmias are a growing problem due to an increase in the incidence of atrial fibrillation and sudden death. The population is becoming older and more patients survive for a longer time period with congestive heart failure, which again increases the frequency of both supraventricular as well as ventricular arrhythmias. Class III antiarrhythmic drugs act by blocking repolarising currents and thereby prolong the effective refractory period of the myocardium. This is believed to facilitate termination of re-entry tachyarrhythmias. This class of drugs is developed for treatment of both supraventricular and ventricular arrhythmias. Amiodarone, sotalol, dofetilide, and ibutilide are examples of class III drugs that are currently available. Amiodarone and sotalol have other antiarrhythmic properties in addition to pure class III action, which differentiates them from the others. However, all have potential serious adverse events. Proarrhythmia, especially torsade de pointes, is a common problem making the benefit-risk ratio of these drugs a key question. Class III drugs have been evaluated in different settings: primary and secondary prevention of ventricular arrhythmias and in treatment of atrial fibrillation or flutter. Based on existing evidence there is no routine indication for antiarrhythmic drug therapy other than beta-blockers in patients at high risk of sudden death. Subgroup analyses of trials with amiodarone and dofetilide suggest that patients with atrial fibrillation may have a mortality reduction with these drugs. However, this needs to be tested in a prospective trial. Similarly, subgroups that will benefit from prophylactic treatment with class III antiarrhythmic drugs may be found based on QT-intervals or - in the future - from genetic testing. Class III drugs are effective in converting atrial fibrillation to sinus rhythm and for the maintenance of sinus rhythm after conversion. This is currently by far the most important indication for this class of drugs. As defined by recent guidelines, amiodarone and dofetilide have their place as second-line therapy except for patients with heart failure where they are first line therapy being the only drugs where the safety has been documented for this group of high risk patients.