QT dispersion and mortality after myocardial infarction

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.

Acute Mesenteric Ischemia: The Diagnostic Value of QT Parameters and their Relationship with CT Findings

BACKGROUND

One of the greatest challenges in the diagnosis of acute mesenteric ischemia (AMI) is the lack of specific laboratory tests that support multidetector computed tomography (CT). Our aim is to investigate the diagnostic value of electrocardiographic QT parameters in AMI and their relationship with CT findings.

MATERIALS AND METHODS

Patients who were admitted to the emergency department with abdominal pain were recruited retrospectively from the hospital information system. Grouping was carried out on the basis of AMI (n=78) and non-AMI (n=78). In both groups, the corrected QT (QTc) and QT dispersion (QTD) were measured on electrocardiographs, and the qualitative and quantitative CT findings were evaluated on CT examinations.

RESULTS

The QTc and QTD values were higher in the AMI group. The median QTc values were 456.16 (IQR: 422.88-483.16) for the AMI group and 388.83 (IQR: 359.74-415.83) for the control group (p<0.001), and the median QTD values were 58 (IQR: 50.3-68.25) for the AMI group and 46 (IQR: 42-50) for the control group (p<0.001). In the CT analysis, the QTc values were significantly higher among AMI patients, with images of paper-thin bowel walls and the absence of bowel wall enhancement (p=0.042 and p=0.042, respectively). Meanwhile, the QTD values were significantly higher among patients with venous pneumatosis findings on CT (p=0.005). In the regression analysis, a significant relationship was found between the QT parameters and AMI (p<0.001). For QTc, an AUC of 0.903 (95% CI: 0.857-0.950, p<0.001), a sensitivity of 80.8%, and a specificity of 82.3% were found. For QTD, an AUC of 0.821 (95% CI: 0.753-0.889, p<0.001), a sensitivity of 73.1%, and a specificity of 82.3% were found.

CONCLUSION

We found the QTc and QTD values to be significantly higher among AMI patients. Furthermore, we found a significant relationship between the CT findings and QTc and QTD and a significant relationship between survival and QTc in the AMI group.

Epicardial adipose tissue as a mediator of cardiac arrhythmias

Obesity is associated with higher risks of cardiac arrhythmias. Although this may be partly explained by concurrent cardiometabolic ill-health, growing evidence suggests that increasing adiposity independently confers risk for arrhythmias. Among fat depots, epicardial adipose tissue (EAT) exhibits a proinflammatory secretome and, given the lack of fascial separation, has been implicated as a transducer of inflammation to the underlying myocardium. The present review explores the mechanisms underpinning adverse electrophysiological remodeling as a consequence of EAT accumulation and the consequent inflammation. We first describe the physiological and pathophysiological function of EAT and its unique secretome and subsequently discuss the evidence for ionic channel and connexin expression modulation as well as fibrotic remodeling induced by cytokines and free fatty acids that are secreted by EAT. Finally, we highlight how weight reduction and regression of EAT volume may cause reverse remodeling to ameliorate arrhythmic risk.

Non-invasive Monitoring of Three Glucose Ranges Based On ECG By Using DBSCAN-CNN

Autonomic nervous system (ANS) can maintain homeostasis through the coordination of different organs including heart. The change of blood glucose (BG) level can stimulate the ANS, which will lead to the variation of Electrocardiogram (ECG). Considering that the monitoring of different BG ranges is significant for diabetes care, in this paper, an ECG-based technique was proposed to achieve non-invasive monitoring with three BG ranges: low glucose level, moderate glucose level, and high glucose level. For this purpose, multiple experiments that included fasting tests and oral glucose tolerance tests were conducted, and the ECG signals from 21 adults were recorded continuously. Furthermore, an approach of fusing density-based spatial clustering of applications with noise and convolution neural networks (DBSCAN-CNN) was presented for ECG preprocessing of outliers and classification of BG ranges based ECG. Also, ECG's important information, which was related to different BG ranges, was graphically visualized. The result showed that the percentages of accurate classification were 87.94% in low glucose level, 69.36% in moderate glucose level, and 86.39% in high glucose level. Moreover, the visualization results revealed that the highlights of ECG for the different BG ranges were different. In addition, the sensitivity of prediabetes/diabetes screening based on ECG was up to 98.48%, and the specificity was 76.75%. Therefore, we conclude that the proposed approach for BG range monitoring and prediabetes/diabetes screening has potentials in practical applications.

Increased QT Dispersion Is Linked to Worse Outcomes in Patients Hospitalized for Out-of-Hospital Cardiac Arrest

Background The incidence and mortality of out-of-hospital cardiac arrest (OHCA) remains high, but predicting outcomes is challenging. Being able to better assess prognosis of hospitalized patients after return of spontaneous circulation would enable improved management of survival expectations. In this study, we assessed the predictive value of ECG indexes in hospitalized patients with OHCA. Methods and Results PR interval and QT interval corrected by the Bazett formula (QTc) for all leads were calculated from standard 12-lead ECGs 24 hours after return of spontaneous circulation in 93 patients who were hospitalized following OHCA. PR interval and QT and QTc duration did not differentiate OHCA survivors and nonsurvivors. However, QT and QTc dispersion was significantly increased in patients who died during hospitalization compared with survivors discharged from the hospital (P<0.01). Logistic regression indicated a strong association between increased QT dispersion and in-hospital mortality (P<0.0001; area under the curve, 0.8918 for QT dispersion and 0.8673 for QTc dispersion). Multinomial logistic regression indicated that the increase of QTc dispersion correlated with worse Cerebral Performance Category scores at discharge (P<0.001; likelihood ratio, 51.42). There was also significant correlation between dispersion measures and serum potassium at the time of measurement and between dispersion measures and cumulative epinephrine administration. No difference existed regarding the number of measurable leads. Conclusions Lesser QT and QTc dispersion at 24 hours after return of spontaneous circulation was significantly associated with survival and neurologic status at discharge. Routine evaluation of QT and QTc dispersion during hospitalization following return of spontaneous circulation might improve outcome prognostication for patients hospitalized for OHCA.

Statin Use in the Early Phase of ST-Segment Elevation Myocardial Infarction Is Associated With Decreased QTc Dispersion

BACKGROUND

Although there is strong evidence supporting the use of statin therapy after myocardial infarction (MI), some mechanistic gaps exist regarding the benefits of this therapy at the very onset of MI. Among the potential beneficial mechanisms, statins may improve myocardial electrical stability and reduce life-threatening ventricular arrhythmia, as reported in stable clinical conditions. This study was designed to evaluate whether this mechanism could also occur during the acute phase of MI.

METHODS

Consecutive patients with ST-segment elevation MI were treated without statin (n = 57) or with a simvastatin dose of 20 to 80 mg (n = 87) within the first 24 hours after MI symptom onset. Patients underwent digital electrocardiography within the first 24 hours and at the third and fifth days after MI. The QTC dispersion (QTcD) was measured both with and without the U waves.

RESULTS

Although QTcD values were equivalent between the groups at the first day (80.6 ± 36.0 vs 80.0 ± 32.1; P = 0.36), they were shorter among individuals using simvastatin than in those receiving no statins on the third (90.4 ± 38.6 vs 86.5 ± 36.9; P = .036) and fifth days (73.1 ± 31 vs 69.2 ± 32.6; P = .049). We obtained similar results when analyzing the QTcD duration including the U wave. All values were adjusted by an ANCOVA model after propensity-score matching.

CONCLUSIONS

Statins administered within 24 hours of ST-segment elevation MI reduced QTc dispersion, which may potentially attenuate the substrate for life-threatening ventricular arrhythmias.

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.

An Easy and Reliable Way to Prevent Electrocardiographic Deteriorations of Patients Undergoing Off-Pump Coronary Artery Bypass Surgery: Preoperative Anxiolytic Treatment

OBJECTIVE

To investigate the effects of preoperative anxiety relieving on electrophysiological changes in patients undergoing off-pump coronary artery bypass surgery.

METHODS

A total of 61 patients at ASA III risk group in the age range of 18-65 years were enrolled in the present study. Patients were randomly divided into two groups. Group S (Sedation group) was administered 0.04 mg/kg lorazepam per os (PO) twice before the operation. Group C (control group) was not administered with any anxiolytic premedication. State Trait Anxiety Inventory (STAI-I) and Beck Anxiety Inventory (BAI) were used to evaluate the level of anxiety. Electrocardiography (ECG), pulse oximeter and standard monitoring were performed for each patient. QT and P dispersions in each derivation of all ECGs were calculated.

RESULTS

Preoperative STAI-I scores were significantly lower in sedation group compared to the controls. Mean values of QT dispersion measured before induction, at the 1st minute of induction, 30th second of intubation and 4th minute of intubation in sedation group were significantly reduced compared to controls (P=0.024; P=0.027; P=0.001; P=0.033, respectively). The mean values of P dispersion measured before induction, at the 3rd minute of induction, 30th second of intubation and 4th minute of intubation in sedation group were significantly reduced compared to controls (P=0.001; P=0.020; P=0.023; P=0.005, respectively).

CONCLUSION

Elevated anxiety levels in patients undergoing coronary bypass surgery have a negative effect through prolonged QT and P-wave dispersion times. Anxiolytic treatment before surgery may be useful to prevent ventricular and atrial arrhythmias and associated complications through decreasing the QT and P-wave dispersion duration.

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

BACKGROUND

QT dispersion, maximal interlead difference in QT interval on 12-lead electrocardiogram (ECG), measures cardiac repolarization abnormalities. Data are conflicting whether QT dispersion predicts adverse outcome in acute ischemic stroke (AIS) patients. Our objective is to determine if QT dispersion predicts: (1) short-term clinical outcome in AIS, and (2) stroke location (insular versus noninsular cortex).

METHODS

Admission ECGs from 412 consecutive patients with acute stroke symptoms from 2 university-based stroke centers were reviewed. QT dispersion was measured. A neuroradiologist reviewed brain imaging for insular cortex involvement. Favorable clinical outcomes at discharge were modified Rankin Scale (mRS) score of 0-1, discharge National Institutes of Health Stroke Scale (NIHSS) score less than 2, and discharge to home. Multiple logistic regressions were performed for each outcome measure and to determine the association between insular infarct and QT dispersion.

RESULTS

Of 145 subjects in the final analysis, median age was 65 years (interquartile range [IQR] 56-75), male patients were 38%, black patients were 68%, median QT dispersion was 78 milliseconds (IQR 59-98), and median admission NIHSS score was 4 (IQR 2-6). QT dispersion did not predict short-term clinical outcome for mRS score (odds ratio [OR] = 1.001, 95% confidence interval [CI] .99-1.01, P = .85), NIHSS at discharge (OR = .994, 95% CI .98-1.01, P = .30), or discharge disposition (OR = 1.001, 95% CI .99-1.01, P = .81). Insular cortex involvement did not correlate with QT dispersion magnitude (OR = 1.009, 95% CI .99-1.02, P = .45).

CONCLUSIONS

We could not demonstrate that QT dispersion is useful in predicting short-term clinical outcome at discharge in AIS. Further, the magnitude of QT dispersion did not predict insular cortical stroke location.

Multiclass Classifier based Cardiovascular Condition Detection Using Smartphone Mechanocardiography

Cardiac translational and rotational vibrations induced by left ventricular motions are measurable using joint seismocardiography (SCG) and gyrocardiography (GCG) techniques. Multi-dimensional non-invasive monitoring of the heart reveals relative information of cardiac wall motion. A single inertial measurement unit (IMU) allows capturing cardiac vibrations in sufficient details and enables us to perform patient screening for various heart conditions. We envision smartphone mechanocardiography (MCG) for the use of e-health or telemonitoring, which uses a multi-class classifier to detect various types of cardiovascular diseases (CVD) using only smartphone's built-in internal sensors data. Such smartphone App/solution could be used by either a healthcare professional and/or the patient him/herself to take recordings from their heart. We suggest that smartphone could be used to separate heart conditions such as normal sinus rhythm (SR), atrial fibrillation (AFib), coronary artery disease (CAD), and possibly ST-segment elevated myocardial infarction (STEMI) in multiclass settings. An application could run the disease screening and immediately inform the user about the results. Widespread availability of IMUs within smartphones could enable the screening of patients globally in the future, however, we also discuss the possible challenges raised by the utilization of such self-monitoring systems.

Impacts of Glycoprotein IIb/IIIa Inhibition on QT Dispersion After Successful Percutaneous Coronary Intervention

Coronary ischemia augments inhomogeneity in ventricular repolarization. Decrease in the QT dispersion (QTd) following restoration of coronary blood flow to the ischemic myocardium by successful percutaneous coronary intervention (PCI) is an expected outcome. The purpose of the study was to seek whether glycoprotein IIb/IIIa (GP IIb/IIIa) inhibition has additional beneficial effects on QT dispersion after angiographically successful PCI. The study involved 111 consecutive patients scheduled for elective coronary balloon angioplasty with or without stent implantation. Sixty patients (mean age 58 ±9) were randomized to receive standard therapy including preprocedural aspirin, ticlopidine, and IV heparin, and 51 patients (mean age 54 ±10) were randomized to receive additional IV tirofiban infusion before the lesion was crossed with the guidewire. Standard 12-lead simultaneous ECG recordings for the measurement of QTd and corrected QTd (QTcd) (calculated by using Bazett’s formula) were obtained before and immediately after the procedure, and at the 6th, and 24th hours. Blood samples for detection of postprocedural myocardial damage (CK-MB and cTn-I) were taken before and immediately after the procedure, at the 6th, 12th, and 24th hours. In total, 128 stenoses were treated with PCI. Seventy of these lesions were in the standard therapy group and 58 in the tirofiban group. QTd and QTcd were not statistically different between the 2 groups before and immediately after the procedure and at the 6th hours, but at the 24th hour QTd and QTcd were significantly longer in the standard therapy group (p=0.047 and p=0.001, respectively). Postprocedural troponin-I elevation (B=0.692, p=0.037), maximum inflation pressure (B=0.182, p=0.001), and previous myocardial infarction (MI) (B=0.885, p=0.004) were defined as the predictors of the final QT dispersion at the 24th hour. QT dispersion significantly decreased after successful percutaneous coronary intervention. GP IIb/IIIa inhibition therapy was not superior by means of recovery of increased QT dispersion during the early hours of the intervention, but it prevented minor myocardial necrosis and provided more long-lasting recovery in QT dispersion as compared with heparin therapy. This impact of GP IIb/IIIa receptor inhibition on QTd may be a possible mechanism by which these drugs reduce cardiovascular events after PCI.

Review: Diabetes and the QT interval: time for debate

The electrocardiographic QT interval has been extensively studied in ischaemic heart disease. Recently, there has been increasing interest in the relationship between diabetes and QT abnormalities. QT prolongation and increased QTd have been shown to predict cardiac death in both type 1 and type 2 diabetes mellitus. Although there is general agreement that QT interval is affected by cardiac ischaemia, the effect of hyperglycaemia on QT measures is controversial. There are also problems surrounding QTd. First, there is controversy as to whether the measure has any physiological meaning; secondly, there is no universally accepted method of measurement and hence no consensus about the upper limit of normal. Nevertheless, several studies have shown increased QTd in diabetic patients suggesting that assessment of the QT interval could be a cost effective way of stratifying aggressive treatment could be directed appropriately to such patients according to cardiovascular risk so that improve outcome.

Electrocardiologic and Echocardiographic Features of Patients Exposed to Scorpion Bite

The purpose of this study is to examine clinical progress and hemodynamic and electrocardi ologic features (QT depression and heart rate variability [HRV]) of patients exposed to a scorpion bite.

Seventeen patients bitten by scorpions, and, as a control group, 15 healthy subjects were included in the study. Standard electrocardiograph (ECG) records, 24-hour Holter-ECG, and Doppler echocardiographic examinations were performed.

Holter ECG indicated sinus tachycardia, sinus bradycardia, paroxysmal supraventricular tachycardia, atrial fibrillation, first-degree and second-degree atrioventricular block not requiring treatment, early atrial beats, and early ventricular beats in the patients at frequen cies of 82%, 12%, 35%, 12%, 8%, 70%, and 47%, respectively.

HRV parameters that reflected parasympathetic activity (SD 35 ±13-43 ±16, RMS-SD: 20 ±9-30 ± 12, high frequency: 7.8 ±2-4.3 ±3, p<0.05) were significantly lower (p<0.05). Low frequency, which especially showed sympathetic activity (LF: 11 ± 13-11 ±23, p>0.05), was similar in both groups. In addition, the LF/HF ratio, which reflected sympathovagal balance, was significantly increased in the patient group (1.5 ±1-3.0 ±2, p = 0.005).

Corrected QT and QT dispersion values were not significantly different with respect to the control (p>0.05).

In the patient group compared to the control, a significant decrease was determined in the proportion of mitral E velocity to mitral A velocity (mEv/mAv), diastolic filling period (DFP), and left ventricular ejection fraction (LVEF), while a significant increase was noticed in pulmonary artery pressure (PAP) (mEv/mAv: 0.9 ±0.4-1.7 ±0.6, DFP: 362 ±8.5-425 ±89, LVEF: 53.1 ±6.7-68.6 ±5.8, PAP: 38.1 ±13-27.2 ±6, p<0.05).

Scorpion bite leads to serious cardiovascular disorders, associated with decreased HRV, decreased systolic and diastolic functions, increased arrhythmic events, and hemodynamic disturbance with sympathetic and parasympathetic balance disturbance.

Effect of obesity and weight loss on ventricular repolarization: a systematic review and meta-analysis

We performed a systematic review and meta-analysis of the effects of obesity ± overweight and weight loss on the corrected QT interval (QTc) and QT or QTc dispersion (indices of ventricular repolarization). Mean difference for both QTc and QT or QTc dispersion with 95% confidence intervals (CIs) was calculated comparing obese ± overweight subjects and normal weight controls and QTc and QT or QTc dispersion before and after weight loss from diet ± exercise or bariatric surgery. A total of 22 studies fulfilled the selection criteria. Compared with normal weight controls, there was a significantly longer QTc in obese ± overweight subjects (mean difference of 21.74 msec, 95% CI: 18.76 to 22.32) and significantly longer QT or QTc dispersion (mean difference of 15.17 msec, 95% CI: 13.59 to 16.74). Weight loss was associated with a significant decrease in QTc (mean difference -25.77 msec, 95% CI: -28.33-23.21) and QT or QTc dispersion (mean difference of -13.46 msec, 95% CI: -15.60 to -11.32 in obese ± overweight subjects. Thus, obesity ± overweight is associated with significant prolongation of QTc and QT or QTC dispersion. Weight loss in obese ± overweight subjects produces significant decreases in these variables. © 2016 World Obesity.

Clinical significance of changes in the corrected QT interval in stress-induced cardiomyopathy

BACKGROUND/AIMS

Although transient changes in the electrocardiogram (ECG) of patients with stress-induced cardiomyopathy (SCMP) are common, there are little data about ECG changes in patients with SCMP and the clinical implications of these variations.

METHODS

We investigated a total of 128 patients (age, 63.2 ± 15.4 years; female, 60.9%) diagnosed with SCMP. We compared the ECGs taken after SCMP diagnosis and during the recovery phase to those taken before SCMP diagnosis under baseline conditions. All patients were divided into two groups according to corrected QT (QTc) interval changes: recovered QTc group (QTc in SCMP > QTc in recovery phase, n = 77) and nonrecovered QTc group (QTc in SCMP ≤ QTc in recovery phase, n = 51).

RESULTS

In comparison of baseline, SCMP, and recovery phase, we found the mean heart rate (81.5 ± 18.7, 96.8 ± 25.3, and 83.0 ± 19.4/min, respectively; p < 0.001), frequencies of ST segment elevation (0.0%, 8.6%, and 1.6%, p = 0.004), ST segment depression (0.0%, 6.3%, and 1.6%, p = 0.007), T wave inversion (4.4 %, 43.8%, and 61.7%, p < 0.001), and QTc (447.4 ± 35.3, 488.9 ± 67.1, and 468.0 ± 49.5, p < 0.001) showed significant changes. In-hospital mortality (9.1% vs. 25.5%, p = 0.012) and critical care (54.5% vs. 72.5%, p = 0.040) occurred more frequently in the nonrecovered QTc group than in recovered QTc group.

CONCLUSIONS

The QTc can be prolonged in patients with SCMP. Short-term mortality was increased in patients where the QTc did not recover.

Defective recovery of QT dispersion following transcatheter aortic valve implantation: frequency, predictors and prognosis

Background

Corrected QT dispersion (cQTD) has been correlated with non-uniform ventricular repolarisation and increased mortality. In patients with aortic stenosis, cQTD has been shown improved after surgical valve replacement, but the effects of transcatheter aortic valve implantation (TAVI) are unknown. Therefore, we sought to explore the frequency, predictors and prognostic effects of defective cQTD recovery at 6 months after TAVI.

Methods

A total of 222 patients underwent TAVI with the Medtronic-CoreValve System between November 2005 and January 2012. Patients who were on class I or III antiarrhythmics or on chronic haemodialysis or who developed atrial fibrillation, a new bundle branch block or became pacemaker dependent after TAVI were excluded. As a result, pre-, post- and follow-up ECG (median: 6 months) analysis was available in 45 eligible patients. Defective cQTD recovery was defined as any progression beyond the baseline cQTD at 6 months.

Results

In the 45 patients, the mean cQTD was 47 ± 23 ms at baseline, 45 ± 17 ms immediately after TAVI and 40 ± 16 ms at 6 months (15% reduction, P = 0.049). Compared to baseline, cQTD at 6 months was improved in 60% of the patients whereas defective cQTD recovery was present in 40%. cQTD increase immediately after TAVI was an independent predictor of defective cQTD recovery at 6 months (per 10 ms increase; OR: 1.89, 95% CI: 1.15–3.12). By univariable analysis, defective cQTD recovery was associated with late mortality (HR: 1.52, 95% CI: 1.05–2.17).

Conclusions

Despite a gradual reduction of cQTD after TAVI, 40% of the patients had defective recovery at 6 months which was associated with late mortality. More detailed ECG analysis after TAVI may help to avoid late death.

Relationship between QT interval dispersion in acute stroke and stroke prognosis: a systematic review

BACKGROUND

QT dispersion (QTd) has been proposed as an indirect electrocardiography (ECG) measure of heterogeneity of ventricular repolarization. The predictive value of QTd in acute stroke remains controversial. We aimed to clarify the relationship between QTd and acute stroke and stroke prognosis.

METHODS

A systematic review of the literature was performed using prespecified medical subjects heading terms, Boolean logic, and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Eligible studies included ischemic or hemorrhagic stroke and provided QTd measurements.

RESULTS

Two independent reviewers identified 553 publications. Sixteen articles were included in the final analysis. There were a total of 888 stroke patients: 59% ischemic and 41% hemorrhagic. There was considerable heterogeneity in study design, stroke subtypes, ECG assessment time, control groups, and comparison groups. Nine studies reported a significant association between acute stroke and baseline QTd. Two studies reported that QTd increases are specifically related to hemorrhagic strokes, involvement of the insular cortex, right-side lesions, larger strokes, and increases in 3,4-dihydroxyphenylethylene glycol in hemorrhagic stroke. Three studies reported QTd to be an independent predictor of stroke mortality. One study each reported increases in QTd in stroke patients who developed ventricular arrhythmias and cardiorespiratory compromise.

CONCLUSIONS

There are few well-designed studies and considerable variability in study design in addressing the significance of QTd in acute stroke. Available data suggest that stroke is likely to be associated with increased QTd. Although some evidence suggests a possible prognostic role of QTd in stroke, larger and well-designed studies need to confirm these findings.

Heart rate variability parameters and ventricular arrhythmia correlate with pulmonary arterial pressure in adult patients with idiopathic pulmonary arterial hypertension

OBJECTIVE

This aim of this study was to correlate heart rate variability (HRV) parameters to pulmonary arterial pressure (PAP) in patients with purely idiopathic pulmonary arterial hypertension (IPAH).

BACKGROUND

HRV is decreased in patients with PAH. Whether HRV indices can be used to assess PAP in IPAH patients remains unclear.

METHODS

HRV parameters obtained by 24-h ECG were evaluated in 26 IPAH patients and 51 controls.

RESULTS

Time-domain HRV parameters (SDNN, p < 0.0001; SDANN, p < 0.0001; RMSSD, p = 0.006) were lower in IPAH patients. Frequency-domain indices (high-frequency power, HFP, p = 0.001; low-frequency power, LFP, p = 0.003; total power, TP, p = 0.001) were also decreased in IPAH patients. In IPAH patients, RMSSD (p = 0.001), HFP (p = 0.015), and LFP (p = 0.027) were significantly correlated with PAP. IPAH patients had longer QTc intervals (p < 0.0001) and more premature ventricular contractions (p < 0.0001) than controls.

CONCLUSIONS

IPAH is associated with autonomic dysfunction. RMSSD, HFP, and LFP may be used as a supplemental tool to assess PAP in IPAH patients. IPAH patients with autonomic dysfunction are at high risk for ventricular arrhythmia.

New electrocardiographic criteria to differentiate acute pericarditis and myocardial infarction

OBJECTIVE

Transmural myocardial ischemia induces changes in QRS complex and QT interval duration but, theoretically, these changes might not occur in acute pericarditis provided that the injury is not transmural. This study aims to assess whether QRS and QT duration permit distinguishing acute pericarditis and acute transmural myocardial ischemia.

METHODS

Clinical records and 12-lead electrocardiogram (ECG) at ×2 magnification were analyzed in 79 patients with acute pericarditis and in 71 with acute ST-segment elevation myocardial infarction (STEMI).

RESULTS

ECG leads with maximal ST-segment elevation showed longer QRS complex and shorter QT interval than leads with isoelectric ST segment in patients with STEMI (QRS: 85.9 ± 13.6 ms vs 81.3 ± 10.4 ms, P = .01; QT: 364.4 ± 38.6 vs 370.9 ± 37.0 ms, P = .04), but not in patients with pericarditis (QRS: 81.5 ± 12.5 ms vs 81.0 ± 7.9 ms, P = .69; QT: 347.9 ± 32.4 vs 347.3 ± 35.1 ms, P = .83). QT interval dispersion among the 12-ECG leads was greater in STEMI than in patients with pericarditis (69.8 ± 20.8 ms vs 50.6 ± 20.2 ms, P <.001). The diagnostic yield of classical ECG criteria (PR deviation and J point level in lead aVR and the number of leads with ST-segment elevation, ST-segment depression, and PR-segment depression) increased significantly (P = .012) when the QRS and QT changes were added to the diagnostic algorithm.

CONCLUSIONS

Patients with acute STEMI, but not those with acute pericarditis, show prolongation of QRS complex and shortening of QT interval in ECG leads with ST-segment elevation. These new findings may improve the differential diagnostic yield of the classical ECG criteria.

Impact of myocardial reperfusion status on QT dispersion after successful recanalization of the infarct-related artery in acute myocardial infarction

OBJECTIVE

To determine whether adequate myocardial perfusion status after transluminal recanalization is associated with prompt improvement of QT dispersion (QTd).

BACKGROUND

Transluminal recanalization of the infarct-related coronary artery in acute myocardial infarction aims to promptly restore myocardial perfusion, to maximize electrical and mechanical recovery. QTd represents the heterogeneity of ventricular repolarization, which may affect electrical stability.

METHODS

Forty patients who underwent primary percutaneous coronary intervention for their first anterior acute ST-elevation myocardial infarction were prospectively enrolled. Myocardial reperfusion status was assessed by myocardial blush grade (MBG) on the final angiogram after successful recanalization (Thrombolysis In Myocardial Infarction Grade 3 flow).

RESULTS

Preprocedural QTd was similar in patients with final MBG 0-1, 2, and 3 (76 ± 24, 67 ± 13, and 69 ± 13 milliseconds, respectively; P = 0.661). After recanalization, QTd decreased in patients with MBG 3 (39 ± 16 milliseconds, P < 0.001) but not in patients with MBG 0-1 (74 ± 20 milliseconds) or MBG 2 (82 ± 16 milliseconds). Multivariate analysis showed that postprocedural MBG was an independent predictor of QTd after recanalization (standardized regression coefficient = -0.628, P < 0.001).

CONCLUSIONS

Adequate tissue perfusion may be crucial for electrical stability of the myocardium after reperfusion.

Potential pro-arrhythmic effect of cardiac resynchronization therapy

A decline in mortality due to pump failure has been clearly documented after cardiac resynchronization therapy (CRT), however the impact on sudden cardiac death and the development of malignant ventricular arrhythmias remains questionable. Our study aims to investigate this alleged pro-arrhythmic effect of CRT using surface electrocardiogram (ECG) markers of pro-arrhythmia.

METHODS

Seventy five patients, who received CRT were included in this study. Manual measurement of corrected QT interval (QTc), Tpeak-end (Tp-e) interval, QT dispersion (QTd) and Tpeak-end dispersion during baseline 12 lead surface ECG and after applying atrial-biventricular pacing were done. Arrhythmias post CRT was recorded from ECG, 24 h holter monitoring or pacemaker programmer event recorder.

RESULTS

QTc interval showed significant prolongation after CRT (498.9 ± 50.8 vs. 476.2 ± 41.6 msec, P = 0.0001). Comparing patients with major arrhythmogenic events (MAE) and increased frequency of premature ventricular contractions (PVCs) post CRT pacing to those patients without arrhythmias, there was a significant prolongation of the QTc interval (527 ± 63.29 vs. 496.95 ± 45.2 msec, P = 0.043) and Tp-e interval (94.16 ± 9 vs. 87.41 ± 16.37 msec, P = 0.049). While in the arrhythmogenic group, there was an insignificant decrease in QTd and Tpeak-end dispersion.

CONCLUSION

QTc and Tp-e intervals are a potential predictor of occurrence of MAE and PVCs. On the other hand, Tp-e dispersion and QTd did not show a predictive potential for arrhythmia.

QT dispersion in patients with systemic lupus erythematosus: the impact of disease activity

Background

Patients with systemic lupus erythematosus (SLE) have increased cardiovascular morbidity and mortality. Although autopsy studies have documented that the heart is affected in most SLE patients, clinical manifestations occur in less than 10%. QT dispersion is a new parameter that can be used to assess homogeneity of cardiac repolarization and autonomic function. We compared the increase in QT dispersion in SLE patients with high disease activity and mild or moderate disease activity.

Methods and Results

One hundred twenty-four patients with SLE were enrolled in the study. Complete history and physical exam, ECG, echocardiography, exercise test and SLE disease activity index (SLEDAI) were recorded. Twenty patients were excluded on the basis of our exclusion criteria. The patients were divided to two groups based on SLEDAI: 54 in the high-score group (SLEDAI > 10) and 50 in the low-score group (SLEDAI < 10).

QT dispersion was significantly higher in high-score group (58.31 ± 18.66 vs. 47.90 ± 17.41 respectively; P < 0.004). QT dispersion was not significantly higher in patients who had received hydroxychloroquine (54.17 ± 19.36 vs. 50.82 ± 15.96, P = 0.45) or corticosteroids (53.58 ± 19.16 vs. 50.40 + 11.59, P = 0.47). There was a statistically significant correlation between abnormal echocardiographic findings (abnormalities of pericardial effusion, pericarditis, pulmonary hypertension and Libman-Sacks endocarditis) and SLEADI (P < 0.004).

Conclusions

QT dispersion can be a useful, simple noninvasive method for the early detection of cardiac involvement in SLE patients with active disease. Concerning high chance of cardiac involvement, cardiovascular evaluation for every SLE patient with a SLEDAI higher than 10 may be recommended.

Trial registration

Clinicaltrial.gov registration NCT01031797

Electrocardiographic findings in sickle cell cardiovascular autonomic neuropathy

BACKGROUND

There is a lack of data on the relationship between cardiovascular autonomic neuropathy (CAN) and electrocardiographic parameters in sickle cell anaemia.

AIMS AND OBJECTIVES

The purpose of the study was to compare the electrocardiographic findings in adult sickle cell anaemia patients with CAN with those of patients without this complication.

METHODS

A cross sectional study was done using 62 consecutively recruited sickle cell anaemia patients who met the inclusion criteria for the study. Cardiovascular autonomic dysfunction was determined based on abnormal values in at least two of five non-invasive tests: Valsalva manoeuver, heart rate variation during deep breathing, heart rate response to standing, blood pressure response to sustained hand grip, and blood pressure response to standing. The subjects were subsequently evaluated with electrocardiography.

RESULTS

Sickle cell anaemia patients with CAN had statistically significantly increased P-wave duration (p < 0.001), PR-interval (p < 0.05) and QTc dispersion (p < 0.05) compared with patients without CAN. Significantly increased frequencies of Q waves and first degree atrio-ventricular block were found in patients with CAN than in those without CAN (p = 0.026, p = 0.014, respectively). Significant correlations were noted between the severity of CAN [number of abnormal autonomic function tests (AFT)] and (1) P-wave duration (p = 0.008), (2) PR- interval (p = 0.013). Significant association was found between the number of abnormal AFT and (1) presence of Q-waves, and (2) degree of anaemia (haematocrit class).

CONCLUSION

Electrocardiographic features consistent with atrio-ventricular and ventricular repolarization abnormalities are associated with CAN in sickle cell anaemia. Further studies are required to evaluate the prognostic implications of these findings in sickle cell patients with cardiovascular autonomic dysfunction.

QT dispersion and rate-corrected QT dispersion during electroconvulsive therapy in elderly patients

BACKGROUND

Electroconvulsive therapy (ECT) induces increase of QT dispersion (QTD) and the rate-corrected QTD (QTcD), which are associated with increased risk of ventricular arrhythmias and cardiovascular mortality. The effects of electrical stimulus during ECT on QTD and QTcD in elderly patients are of considerable interest.

OBJECTIVE

The purpose of this study was to clarify the differential effects of electrical stimulus caused by ECT on interbeat interval, QT interval, the rate-corrected QT (QTc) interval, QTD, and the QTcD under propofol anesthesia between younger and elderly patients with major depression.

METHODS

Twenty younger psychiatric patients (aged 30-40 years) and 20 elderly patients (aged 65-75 years) scheduled for ECT were studied under propofol anesthesia. A 12-lead electrocardiogram was monitored to measure parameters. Muscle paralysis was achieved by administering 1-mg/kg succinylcholine intravenously, and the efficacy of ECT was determined by the tourniquet technique.

RESULTS

The mean arterial pressure in the elderly was significantly higher than that of the younger patients from immediately to 2 minutes after electrical stimulus. The interbeat interval in the elderly was significantly lower than that of the younger patients from immediately to 1 minute after electrical stimulus. There was no statistically significant difference in the QT interval between the groups. The baseline value of QTc interval was higher than the normal limits, and the QTc interval in the elderly was significantly lower than that of the younger patients from immediately to 1 minute after electrical stimulus. The baseline value of QTD was higher than the normal limits, and the QTD in the elderly was significantly higher than that of the younger patients from immediately to 7 minutes after electrical stimulus. The baseline value of QTcD was higher than the normal limits, and the QTcD in the elderly was significantly higher than that of the younger patients from immediately to 7 minutes after electrical stimulus.

CONCLUSIONS

The QTc interval, QTD, and QTcD may be higher than the normal limits before anesthesia in patients with major depression. The QTD and QTcD in the elderly, which are associated with increased risks of ventricular arrhythmias, are higher than those of the younger patients after electrical stimulus during ECT. Electrical stimulus may induce further increased risks of cardiac events in elderly patients.

Clinical study of the electrophysiological effects of ischemic post-conditioning in patients with acute myocardial infarctions

BACKGROUND

Ischemic "pre"-conditioning has been shown to have antiarrhythmic effects. The aim of this study was to investigate whether ischemic "post"-conditioning (post-CON) also has antiarrhythmic effects in ST-segment elevation myocardial infarction (STEMI) patients undergoing coronary angioplasty (PCI) as a clinical model of post-CON.

METHODS AND RESULTS

A total of 61 patients suffering from an acute myocardial infarction (AMI) were included. The QT dispersion (QTd) was measured before each balloon inflation (BI) and after deflation (BD) during PCI. The hemodynamic parameters and electrocardiogram were also assessed during PCI. All data were analyzed using a logistic regression analysis. A total of 36 of 61 STEMI patients could be analyzed according to the protocol. The QTd shortened significantly as the BI and BD were repeated (p<0.05). Prior to the PCI, frequent premature ventricular contractions (PVCs) were observed in 5 patients, and the PVCs were remarkably suppressed or disappeared entirely as the BI and BD were repeated. Non-sustained ventricular tachycardia was observed prior to the PCI in 2 patients; this also disappeared as the BI and BD were repeated. Ventricular fibrillation (VF) occurred in 1 patient prior to PCI, necessitating D-C cardioversion. After repeating the BI and BD during PCI, VF no longer recurred.

CONCLUSIONS

In the majority of the AMI patients studied, post-CON exhibited significant antiarrhythmic effects as assessed by the change in the QTd. The ventricular dysarrhythmias were also suppressed during the PCI.

Arsenic-induced QT dispersion is associated with atherosclerotic diseases and predicts long-term cardiovascular mortality in subjects with previous exposure to arsenic: A 17-Year follow-up study

Chronic arsenic poisoning is a major worldwide public health problem. Recently, we had reported chronic arsenic poisoning was dose-dependently associated with ventricular abnormalities quantified by electrocardiographic QT prolongation linking to atherosclerotic diseases. An association of chronic arsenic poisoning with ventricular repolarization inhomogeneity quantified by QT dispersion (QTD) is of particular interest from a theoretical and practical perspective. We aimed to further elucidate (1) the association of chronic arsenic exposure with ventricular abnormalities quantified by QTD, (2) the association of QTD with atherosclerotic diseases and (3) the predictability of QTD for long-term mortality in subjects with chronic arsenic poisoning. We followed up 280 men and 355 women living in arseniasis-endemic area in southwestern coast in Taiwan for 17 years. QTD in electrocardiogram and carotid intima-media thickness by ultrasonography were measured. Coronary artery disease was diagnosed by an abnormal electrocardiogram and a definite history. Cumulative arsenic exposure was significantly associated with QTD showing a dose-response relationship (P < 0.001). Significant associations of the QTD with coronary artery disease and carotid atherosclerosis existed after adjustment for potential confounders in the multiple linear regression analysis (all P values < 0.05). In the multivariate Cox regression analyses, the hazard ratios (95% confidence interval, P value) of cumulative cardiovascular and all-cause mortality were 3.9 (2.1-6.2, P = 0.002) and 1.4 (0.9-2.3, P = 0.10), respectively, for QTD > or = 65 ms compared with QTD < 65. QTD may be indicated as an early biomarker for atherosclerotic diseases and a significant and strong predictor of cardiovascular mortality in population with chronic arsenic exposure.

Assessment of QT interval and QT dispersion during electroconvulsive therapy using computerized measurements

BACKGROUND

Electroconvulsive therapy (ECT) used in the treatment of severe psychiatric disorders induces stimulation of the autonomic nervous system with initial parasympathetic outflow immediately followed by a sympathetic response. These responses induce an initial bradycardia, arrhythmias, and hypertension. QT dispersion (QTD), defined as maximal QT interval minus minimal QT interval on 12 leads of the surface electrocardiogram, reflects regional heterogeneity of ventricular repolarization. The effects of electrical stimulus due to ECT on QT interval and QTD are of considerable interest.

OBJECTIVE

: This study was designed to investigate the effects of electrical stimulation caused by ECT on RR interval, QT interval, the rate-corrected QT (QTc) interval, QTD, and the rate-corrected QTD (QTcD) under general anesthesia using computerized measurements.

METHODS

Thirty psychiatric patients scheduled for ECT were studied under propofol anesthesia. A 12-lead electrocardiogram was monitored to measure parameters. Muscle paralysis was achieved by administering succinylcholine 1 mg/kg intravenously, and the efficacy of ECT was determined by the tourniquet technique.

RESULTS

The RR interval and QT interval decreased significantly immediately after electrical stimulus, and returned to the baseline level 1 minute after electrical stimulus. In 25 out of 30 patients, the baseline value of QTc interval was higher than the normal limits, and the QTc interval decreased significantly for 2 minutes after electrical stimulus. In 27 out of 30 patients, the baseline values of QTD and QTcD were higher than the normal limits, and the QTD and QTcD increased significantly from immediately after electrical stimulus to 5 minutes after electrical stimulus.

CONCLUSIONS

The QTc interval, QTD, and QTcD, which were associated with increased risks of ventricular arrhythmias, increased significantly before anesthetic induction in patients with major depression. Electrical stimulus during ECT induced further increases of the QTD and QTcD.

Late potentials and QT dispersion after high-dose chemotherapy in patients with non-Hodgkin lymphoma

The most common cardiotoxic effects of high-dose cyclophosphamide (CY) are electrocardiographic changes and transient arrhythmias. Therefore, we prospectively assessed serial electrocardiogram (ECG) and signal-averaged electrocardiogram (SAECG) recordings in 30 adult patients with non-Hodgkin lymphoma (NHL) receiving high-dose CY as part of high-dose chemotherapy (HDT) regimen. All patients were treated with anthracyclines earlier. Heart-rate-corrected QT interval and QT dispersion (QTc and QTc dispersion) were measured from ECG. QRS duration and late potentials (LPs) were analysed from SAECG. Both ECG and SAECG were recorded 1 day (d) prior to HDT (d-7) at baseline, and 1 day (d-2), 7 days (d+7), 12 days (+12) and 3 months (m+3) after HDT. Stem cells were infused on day 0 (d0). Cardiac systolic and diastolic function were assessed on (d-7), (d+12) and (m+3) by radionuclide ventriculography. At baseline, four patients presented with LPs. Cardiac systolic function decreased significantly (53 +/- 2; 49 +/- 2%, P = 0.009 versus baseline), whilst no patient developed acute heart failure. QRS duration prolonged and RMS(40) reduced significantly versus baseline (104 +/- 3; 107 +/- 3 ms, P = 0.003; 41 +/- 4; 38 +/- 3 microV, P = 0.03), and six patients (21%) presented with LPs after CY treatment. Both QTc interval and QTc dispersion increased versus baseline (402 +/- 5; 423 +/- 5 ms, P<0.001; 32 +/- 2; 44 +/- 3 ms, P = 0.012), and six patients (20%) developed abnormal QT dispersion. In conclusion, high-dose CY causes subclinical and transient electrical instability reflected by occurrence of LPs as well as increased QTc interval and QT dispersion. Thus, longer follow-up is required to confirm the meaning of these adverse effects on cardiac function and quality of life.

The association between T-wave morphology and life-threatening ventricular tachyarrhythmias in patients with congestive heart failure

BACKGROUND

Whether T-wave morphology descriptors on the 12-lead electrocardiogram (ECG) can predict the occurrence of life-threatening ventricular arrhythmia in patients with advanced congestive heart failure is unclear.

METHODS

Standard 12-lead ECGs were photoscanned and digitized for analysis in 27 heart failure patients with ventricular tachycardia/ventricular fibrillation (VT/VF; study group), as well as in 54 age- and sex-matched heart failure patients without life-threatening ventricular arrhythmia as a control group. Novel T-wave morphology descriptors were compared.

RESULTS

The results showed that the temporal descriptor, the lead dispersion (LD; 426.5 +/- 279.8 vs 189.0 +/- 125.7, P < 0.001), was significantly higher in the study than in the control group. The other T-wave morphology parameters, such as the T-wave morphology dispersion (45.7 +/- 20.1 vs 44.9 +/- 18.6), the total cosine between QRS and T wave (TCRT; -0.4 +/- 0.4 vs -0.5 +/- 0.3), and the normalized T-loop area (NTLA; 0.5 +/- 0.1 vs 0.4 +/- 0.1), were not significantly different between the two groups (all P value > 0.05). After an adjustment for other clinical variables, increased LD (odds ratio: 9.9, 95% confidence interval [CI]: 2.9-33.4, P < 0.001) or decreased NTLA (odds ratio: 0.4, 95% CI: 0.1-1.0, P =0.05) was associated with VT/VF.

CONCLUSION

The novel T-wave morphology analysis may help in identifying heart failure patients at high risk for VT/VF.

Prognostic evaluation of QT-dispersion in elderly hypertensive and normotensive patients

BACKGROUND

QT-corrected interval dispersion (QTcD) is an indirect index of increased heterogeneity of ventricular repolarization. However, the prognostic value of (QTcD) in elderly hypertensive and normotensive patients has not been thoroughly investigated yet.

METHODS

The study population consisted of 60 consecutive patients (34 males/26 females; mean age: 63+/-11 years) with mild to moderate essential arterial hypertension and 48 consecutive age-matched healthy subjects (24 males/24 females; 65+/-16 years). QTcD was measured by a 12-lead electrocardiogram (ECG) as the difference between maximum and minimum QT-interval, corrected for heart rate. Ventricular arrhythmias were recorded by a 24-hour Holter ECG and classified by a modified Lown's score (range: 0-6). Left ventricular mass was measured echocardiographically and indexed by body surface area [left ventricular mass index (LVMI)]. Nine patients were lost during the follow-up period. Patients were followed up for 54+/-9 months, and the primary end-point was the major cardiovascular events (including cardiac mortality).

RESULTS

Major cardiovascular events occurred in 22 patients (22%). Patients with QTcD>or=45 ms (n=35) had a higher rate of major cardiovascular events (43% vs 11%; log rank: 14.8; P<0.001), a higher LVMI (146+/-29 vs 104+/-21 g/m2; P<0.001), greater values of systolic and diastolic blood pressure (154+/-16 vs 144+/-18 mmHg; P<0.01 and 92+/-10 vs 88+/-8 mmHg; P<0.05, respectively), a higher number of premature ventricular beats (354+/-870 vs 113+/-301; P<0.05), and a greater Lown's score (3.7+/-1.9 vs 1.4+/-1.8; P<0.05) than patients with QTcD<45 ms. QTcD (>or=or<45 ms) was an independent predictor of major cardiovascular events (odds ratio: 4.9; 95% confidence interval: 2.0-12.1; P=0.001) after adjustment for LVMI, Lown's score (>or=or<3), age (>or=or<65 years), and QTc max (>or=or<437 ms).

CONCLUSIONS

QTcD is an independent predictor of major cardiovascular events in elderly hypertensive and normotensive patients and might be used in their risk stratification.

Heart rate-corrected QT interval and QT dispersion in patients with pulmonary hypertension

OBJECTIVE

Heart rate-corrected QT interval (QTc) and QTc dispersion (QTcd) are increased and associated with ventricular arrhythmia and an increase in sudden death in a variety of diseases. This study aimed to examine QTc and QTcd in pulmonary hypertension and assess their relationship with pulmonary arterial pressure.

PATIENTS AND METHODS

A total of 201 patients who had undergone right heart catheterization for a preliminary diagnosis of pulmonary hypertension between December 2003 and July 2008 were included in the study. Resting 12-lead electrocardiogram was recorded. QT interval was measured manually and corrected using Bazett's formula. Patients were divided into groups with mild-to-moderate and severe pulmonary hypertension and a control group according to mean pulmonary arterial pressure.

RESULTS

In all observed cases, mean QTc was higher in severe pulmonary hypertension than in controls (428.6 +/- 32.8 ms vs. 411.1 +/- 28.4 ms, P = 0.018) and QTcd was higher in mild-to-moderate (60.1 +/- 17.2 ms) and severe pulmonary hypertension (63.9 +/- 20.5 ms) than in controls (47.3 +/- 10.6 ms) (P = 0.031; P = 0.004). In men, there was no significant difference in mean QTc and QTcd. In women, mean QTc was higher in severe pulmonary hypertension than in controls (436.1 +/- 39.4 ms vs. 407.6 +/- 24.8 ms, P = 0.037) and QTcd was higher in severe pulmonary hypertension (68.5 +/- 20.9 ms) than in both the controls (45.1 +/- 12.6 ms) and patients with mild-to-moderate pulmonary hypertension (58.6 +/- 14.7 ms) (P = 0.002; P = 0.003). In addition, in women with pulmonary hypertension, mean QTc and QTcd were positively correlated to mean pulmonary arterial pressure (r = 0.207, P = 0.03; r = 0.236, P = 0.012).

CONCLUSIONS

In women with pulmonary hypertension, mean QTc and QTcd are positively correlated to mean pulmonary arterial pressure and are significantly increased in patients with severe pulmonary hypertension.

Angioplasty decreases prolonged QT dispersion in patients with angina pectoris but not in patients with prior myocardial infarction

BACKGROUND AND HYPOTHESIS

Prolonged QT dispersion (QTd) is shortened by successful percutaneous transluminal coronary angioplasty (PTCA) in patients with ischemic heart disease. Particularly, QTd plays an important role in the prognostication in patients with prior myocardial infarction (MI). However, whether the effect of PTCA on QTd differs in patients with and without prior MI is not clear, and this study sought to clarify this question.

METHODS

In 41 consecutive patients with ischemic heart disease, we measured QTd from a routine 12-lead electrocardiogram taken at 72 h before and after successful PTCA. Patients were divided into two groups based on the presence or absence of prior MI: Group 1 consisted of 24 patients with angina (61 +/- 11 years old) without prior MI and Group 2 was comprised of 17 patients (69 +/- 10 years old) with prior MI. QTd was calculated as the difference between the maximum and minimum QT and QT corrected for heart rate (QTc), using Bazett's formula for calculating QTcd. All measurements were obtained manually and blindly.

RESULTS

In Group 1, 15 of 24 patients (63%) demonstrated multivessel disease and 16 of 24 (67%) patients had high QTd > 60 ms. Percutaneous transluminal coronary angioplasty decreased QTd and QTcd in Group 1 (QTd, from 83 +/- 35 to 57 +/- 19 ms, p < 0.05 ; QTcd, from 89 +/- 37 to 63 +/- 33 ms, p < 0.05), whereas no changes were observed in Group 2 (QTd, from 73 +/- 25 to 69 +/- 22 ms, NS; QTcd, from 80 +/- 30 to 79 +/- 28 ms, NS). QTd is more sensitive to decrease by successful PTCA in patients with angina than in patients with prior MI.

CONCLUSIONS

The effect of successful PTCA on inhomogeneity of ventricular repolarization reflected by QTd in patients with prior MI is different from that in patients without prior MI.

QT dispersion and transmural dispersion of repolarization in patients with familial Mediterranean fever

Familial Mediterranean fever (FMF) is a disease characterized by sporadic, paroxysmal attacks of fever and serosal inflammation. QT dispersion (QTd) and transmural dispersion of repolarization (TDR), simple noninvasive arrhythmogenic markers, that can be used to assess homogeneity of cardiac repolarization, have not been studied in FMF patients before. The aim of our study was to evaluate the QTd and TDR in FMF patients without overt cardiac involvement. A total of 50 patients with FMF (30 men, 20 women, 29.4 +/- 11.8 years) and 50 controls (30 men, 20 women; mean age 31.3 +/- 11.9 years) were included. QTd, corrected QTd (cQTd), maximum QT (QTmax), maximum corrected QT (cQTmax), minimum QT (QTmin), and minimum corrected QT intervals (cQTmin) and TDR were measured from standard 12-lead electrocardiography (ECG). We found that QTd, QTmax, and TDR were greater in FMF patients than in the control group (36.0 +/- 11.4 vs. 20 +/- 11.2, P < 0.001 and 354.8 +/- 30.9 vs. 342.8 +/- 18.0, P = 0.02; 62.0 +/- 16.0 vs. 49.0 +/- 9.5 P < 0.001, respectively), as were cQTd and cQTmax (40.4 +/- 13.5 vs. 21.9 +/- 12.4, P < 0.001 and 397.7 +/- 40.2 vs. 375.5 +/- 25.4 P = 0.001). A modest positive correlation was found between cQTd and C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) (r = 0.30, P < 0.001; r = 0.40, P < 0.001; respectively). QTd, which is an index of inhomogeneity of ventricular repolarization and an important predictor of cardiovascular mortality, and TDR, which is a better marker of cardiac repolarization, increased in FMF patients similarly as in other rheumatologic diseases.

Changes in QT dispersion during adenosine infusion

BACKGROUND

QT dispersion (QTd) measurement during treadmill stress testing has been to shown to improve the accuracy of exercise electrocardiogram (ECG) in the detection of significant coronary artery disease (CAD).

HYPOTHESIS

The aim of this study was to determine whether adenosine-induced changes in QTd could predict significant CAD and to assess its efficacy as a diagnostic index in patients undergoing adenosine stress test.

METHODS

QT interval measurements were made in 57 consecutive patients undergoing adenosine sestamibi stress test. Patients with an abnormal stress test underwent coronary angiography. Patients with significant disease by coronary angiography (> 70% stenosis) were classified as having CAD (Group 1), and those with normal stress images and/or normal coronaries by angiography were classified as having no CAD (Group 2).

RESULTS

QT dispersion increased from 28.2 +/- 4.5 to 43.8 +/- 4.5 ms with a delta QTd of 15.53 +/- 3.68 in Group 1 (p = 0.001) and from 28.4 +/- 2.6 to 34.8 +/- 2.8 ms with a delta QTd of 6.58 +/- 2.21 ms in Group 2 (p = 0.006). Patients in Group 1 had a significantly higher increase in QTd (delta QTd) than the patients in Group 2 (p < 0.03). Addition of delta QTd (> 10 ms) to the ST depression during adenosine infusion would increase the sensitivity of the ECG from 23 to 65% and decrease the specificity from 91 to 70% for diagnosis of significant CAD.

CONCLUSIONS

delta QTd is significantly more prolonged in patients with CAD during adenosine infusion. It increases the sensitivity of the stress ECG in diagnosis of CAD during adenosine infusion when used as an adjuvant index.

Effect of balloon inflation-induced acute ischemia on QT dispersion during percutaneous transluminal coronary angioplasty

BACKGROUND

QT dispersion (QTd = QTmax-QTmin) measured as interlead variability of QT interval reflects the spatial inhomogeneity of ventricular repolarization times, and increased QTd may provide a substrate for malignant ventricular arrhythmias. Ischemia is associated with regional abnormalities of conduction and repolarization.

HYPOTHESIS

This study aimed to investigate the effect of acute ischemia on QTd during successful percutaneous transluminal coronary angioplasty (PTCA).

METHODS

Forty-three patients (10 women, 33 men, mean age 56 years) were enrolled in the study. Electrocardiogram (ECG) recordings were taken before PTCA and during balloon inflation period. QT maximum (QTmax), QT minimum (QTmin), and QTd (QTmax-QTmin) values were calculated from the surface ECG.

RESULTS

There was no difference among QTmax values (p = 0.6). Mean QTmin during balloon inflation was lower than before PTCA (368 +/- 45 vs. 380 +/- 41 ms, p = 0.002). The difference between QTd values before and during balloon inflation was statistically important (65 +/- 9 vs. 76 +/- 10 ms, p = 0.001). This difference is caused by a decrease in QTmin during balloon inflation.

CONCLUSION

Acute reversible myocardial ischemia induced by balloon inflation causes an increase in QTd value, and this increment is the result of a decrease in QTmin interval. Therefore, QTd may be a marker of reversible myocardial ischemia.

Effect of amiodarone on QT dispersion in the 12-lead standard electrocardiogram and its significance for subsequent arrhythmic events

BACKGROUND AND HYPOTHESIS

QT dispersion, measured as interlead variability of QT intervals in the surface electrocardiogram, has been demonstrated to provide an indirect measurement of the inhomogeneity of myocardial repolarization. The purpose of the present study was twofold: (1) to analyze the effect of amiodarone on QT dispersion measured in the 12-lead standard ECG, and (2) to examine the association between QT dispersion on amiodarone and subsequent arrhythmic events.

METHODS

To determine the effect of amiodarone on QT dispersion and its clinical significance for subsequent arrhythmic events, QT dispersion was measured in the 12-lead standard electrocardiogram (ECG) in 52 patients before and after administration of empiric amiodarone for ventricular tachyarrhythmias.

RESULTS

QT intervals increased from 401 +/- 44 ms before amiodarone to 442 +/- 53 ms after amiodarone therapy, and rate corrected QT intervals (QTc) increased from 452 +/- 43 ms to 477 +/- 37 ms, respectively (p < 0.01). QT dispersion, QTc dispersion, and adjusted QTc dispersion, which take account of the number of leads measured, were not significantly different before and after initiation of amiodarone therapy (58 +/- 24 ms vs. 61 +/- 26 ms, 68 +/- 29 vs. 66 +/- 26 ms, and 22 +/- 8 vs. 22 +/- 8 ms, respectively, p = NS). During 31 +/- 25 months follow-up after initiation of amiodarone therapy, arrhythmic events defined as sustained ventricular tachycardia, ventricular fibrillation, or sudden death occurred in 11 of 52 study patients (21%). QT dispersion, QTc dispersion, and adjusted QTc dispersion on amiodarone were not different between patients with and without arrhythmic events during follow-up (65 +/- 14 vs. 59 +/- 29 ms, 73 +/- 15 vs. 64 +/- 28 ms, and 25 +/- 6 vs. 21 +/- 8 ms, respectively, p = NS).

CONCLUSIONS

We conclude that (1) amiodarone increases QT intervals and QTc intervals during sinus rhythm but does not significantly change measures of QT dispersion; and (2) QT dispersion measured in the 12-lead standard ECG after initiation of amiodarone therapy does not appear to be a useful marker for subsequent arrhythmic events.

Changes of the T-wave amplitude and angle: an early marker of altered ventricular repolarization in hypertension

BACKGROUND

The heterogeneity of ventricular repolarization is an important proarrhythmic factor. QT dispersion has been proposed to reflect the inhomogeneity of ventricular repolarization, but a poor reproducibility limits its clinical applicability. Reliable noninvasive methods to quantify abnormalities in ventricular repolarization are still lacking. The T-loop morphology analysis is a novel method aimed at quantifying ventricular repolarization.

HYPOTHESIS

To test the ability of the T-loop morphology analysis to discriminate between hypertensive patients and healthy subjects, 105 hypertensive patients (mean age 63.6 +/- 12.3 years) and 110 healthy controls (mean age 49.7 +/- 14.3 years) were evaluated.

METHODS

The maximum QT interval (QT maximum), the minimum QT interval (QT minimum), and their difference (QT dispersion) were calculated from a digitally recorded 12-lead electrocardiogram (ECG) in both study groups. X, Y, and Z leads were reconstructed from the 12-lead ECG, and the amplitude of the maximum T vector (T amplitude) and the angle between the maximum T vector and X axis (T angle) were calculated from the projection of the T loop in the frontal plane.

RESULTS

T amplitude (p < 0.001), T angle (p = 0.05), and QT dispersion (p = 0.04) were significantly different between hypertensive patients and controls, while QT maximum (p = 0.14) and QT minimum (p = 0.35) did not differ between the groups. T amplitude was the only marker which differed between hypertensive patients without ECG criteria for left ventricular hypertrophy and controls (p = 0.002).

CONCLUSIONS

T-loop features and particularly T amplitude are significantly different between hypertensive patients and healthy controls and may serve as early markers of repolarization abnormalities in a hypertensive population.

Effects of acute alcohol infusion on duration and dispersion of QT interval in male patients with coronary artery disease and in healthy controls

BACKGROUND AND HYPOTHESIS

Alcohol consumption may have advantageous epidemiologic effects but ethanol also increases the risk of sudden coronary death. Prolongation of QT interval has been reported in chronic alcoholics. Long QT period predisposes to serious arrhythmias, and therefore we studied whether acute alcohol intoxication prolongs repolarization in patients with stable coronary artery disease (CAD).

METHODS

The effects of acute ethanol steady-state intravenous infusion (0.72 g/kg body weight within 60 min) on QT interval and QT dispersion, assessed by 12-lead electrocardiograms (ECG), were studied in 22 men with stable CAD and in 10 controls. Heart rate variability was measured by Holter recordings.

RESULTS

Mean blood alcohol rose to 26.1 +/- 4.3 mmol/l(1.2 +/- 0.2/1000), and was maintained for 2 h. Heart rate was 56 +/- 7 beats/min before and 54 +/- 8 beats/min during ethanol infusion (NS). The heart rate-adjusted QT interval increased on the average 13-23 ms over the 12-lead ECG (p < 0.005). The QT dispersion remained unaltered. The was no difference in the repolarization response in the patients with CAD compared with the controls. The high- and low-frequency components of heart rate variability remained unaltered.

CONCLUSIONS

In middle aged men, regardless of the presence of CAD, moderate amounts of alcohol cause prolongation of ventricular repolarization. Changes in the activity of the autonomic nervous system do not seem to explain the observed phenomenon.

QT dispersion and left ventricular hypertrophy in elderly hypertensive and normotensive patients

Inhomogeneity of ventricular repolarization as detected by QT dispersion may be a potential leading mechanism of sudden death in hypertensive and normotensive (age related) left ventricular hypertrophy. Aim of this study was to investigate QT dispersion, ventricular arrhythmias, and left ventricular mass index in elderly hypertensive and normotensive patients. Study population consisted of 60 consecutive patients (sex: 34 men/26 women; age: 63 +/- 11 years) with essential arterial hypertension and 48 age and sex-matched control subjects (24 men/24 women; 64 +/- 16 years). Measurements included QTc dispersion, ventricular arrhythmias, and left ventricular hypertrophy. Hypertensive patients had greater left ventricular mass index (P = .006) and higher QTc dispersion (P = .004) than controls. Left ventricular hypertrophy was diagnosed in 57 (31 men/26 women) of all subjects. These patients had higher blood pressure (P < .05), Lown's score (P < .001), and QTc dispersion (P < .001). QTc dispersion and Lown's score were independent predictors of left ventricular mass index (P < .001). Conclusively, QTc dispersion is a strong indicator of left ventricular mass index and might be used in risk stratification of hypertensive and normotensive elderly patients.

Assessment and key targets for therapy in the post-myocardial infarction patient with left ventricular dysfunction

In the post-myocardial infarction (MI) patient with coronary artery disease (CAD) and left ventricular dysfunction (LVD), ischemia and adverse remodeling hinder myocardial performance and increase electrical instability. Collectively, the coronary arteries, myocardium, and conduction system represent the principal pathophysiologic targets in MI complicated by LVD. Consequently, an accurate assessment of disease severity in these targets is essential for the design of an effective therapeutic program. This review describes the current modalities for assessing the key pathophysiologic targets in post-MI patients with LVD and the effects of systemic factors on cardiac disease severity.

Structural barrier increases QT-peak dispersion in swine left ventricle in vivo

QT dispersion (QTD) is thought to represent the regional nonuniformity of ventricular repolarization and can serve as a prognostic marker for vulnerability to ventricular arrhythmias and risk for sudden cardiac death (SCD). In this study, we used an in vivo swine model to investigate the change of QT-peak dispersion before and after the introduction of a left-ventricular (LV) free-wall structural barrier (SB). Baseline and post-ablation pacing were delivered to: (i) the epicardial LV base, (ii) the epicardial LV apex, and (iii) the right ventricular (RV) endocardium. Four unipolar electrograms were measured from LV free wall epicardial sites referenced to an intrathorax electrode. An SB (approximately 4 x 1 x 1 cm (length, width, depth)) was created by cryoablation in the middle of the two electrode pairs. QTD was computed as the difference between QT-peak intervals for each beat from two electrodes across the SB region from one another. A significant increase of QTD occurred (p<0.05) after the introduction of the SB in all six animals. These results may reflect the accentuation of anatomical repolarization heterogeneity due to SB disruption of electrotonic coupling. Given the link between dispersion of repolarization and initiation of reentry, these findings are consistent with the increased arrhythmia risk of structural heart disease.

Circadian variation in QT dispersion determined from a 12-lead Holter recording: a methodological study of an age- and sex-stratified group of healthy subjects

BACKGROUND

QT dispersion is considered to reflect inhomogeneity of myocardial repolarization.

METHOD

The circadian variation of QT interval dispersion was examined in 95 healthy subjects using 24-hour Holter monitoring. Three different methods of lead selection were applied: all 12 leads (QTdisp 12), only precordial leads (QTdisp 6), and the pair of leads selected at 3 a.m. in which the longest and shortest QT intervals were found in each individual subject (QTdisp 2).

RESULTS

A preliminary methodological study including measurements from every minute in 10 subjects revealed no significant circadian variation using mean values of QTdisp 12, QTdisp 6, or QTdisp 2 obtained every hour, every 2, or every 4 hours, except in QTdisp 6, which demonstrated a significant circadian variation (P < 0.01) in 1-hour measurements. Analysis of all 95 subjects using measurements obtained every 4 hours revealed a significant circadian variation in QTdisp 12 and QTdisp 6 (P < 0.0001), whereas no circadian variation was seen in QTdisp 2. A subdivision into 10-year age groups revealed that subjects at age >50 years had a significant circadian variation in QTdisp 12 and QTdisp 6, but not in QTdisp 2. Only in males a significant circadian variation was seen in QTdisp 12 (P < 0.0001), whereas QTdisp 6 demonstrated a circadian variation both in females (P < 0.001) and in males (P < 0.0001).

CONCLUSIONS

Selection of leads is of crucial importance for repetitive measurements of QT dispersion. Circadian variation was detected in subjects over 50 years of age, when all 12 or only the 6 precordial leads were taken into account.

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.