Evaluation of autonomic influences on QT dispersion using the head-up tilt test in healthy subjects

Analysis of Factors Relevant to the Severity of Symptoms in Children and Adolescents with Postural Orthostatic Tachycardia Syndrome

Objectives: The current study aims to investigate the factors associated with the severity of conditions for pediatric cases with postural orthostatic tachycardia syndrome (POTS). Methods: Patients hospitalized and first diagnosed with POTS were retrospectively included and reviewed. The severity of symptoms was evaluated by symptom scores (SSs). Multiple Spearman correlation analyses and multiple linear regression analyses were used to determine factors independently associated with SS. Patients were divided into the mild (SS ≤ P25) and severe (SS ≥ P75) groups to test the distinguishing efficiency of the candidate factors. The efficiency of each independently correlated factor in indicating the condition of children with POTS was assessed by the receiver operating characteristic (ROC) curve. Results: A series of 296 pediatric patients aged 5-17 years suffering from POTS were included. Multiple Spearman correlation analyses and multiple linear regression analyses showed that corrected QT interval dispersion (QTcd) was independently correlated with SS (p < 0.05). QTcd can be used to suggest the severity of POTS symptoms, and the area under the curve (AUC) was 0.986 (95% CI 0.976-0.997). At a threshold of QTcd = 45 ms, the sensitivity and specificity were, respectively, 94.0% and 91.8% for symptom severity indication. Conclusions: In pediatric cases with POTS, QTcd was positively correlated with their symptom severity and exhibited a strong indicative value. A QTcd of 45 ms was a valid cut-off value for indicating symptom severity.

Predictor of Syncopal Recurrence in Children With Vasovagal Syncope Treated With Metoprolol

Objective

To explore the predictors for syncopal recurrence in a pediatric population with vasovagal syncope (VVS) treated with metoprolol.

Study Design

This study was conducted retrospectively among children suffering from VVS with or without syncopal recurrence. Data on the detailed medical history and auxiliary examinations were obtained from the electronic medical records. The risk factors for syncopal recurrence were studied by cox regression analyses and the corresponding best cutoff values were determined using receiver operating characteristic analysis. Kaplan-Meier curves were plotted to determine the trends of the syncopal recurrence-free survival rate.

Results

Forty-two consecutive VVS children were enrolled in the study. At the end of a median follow-up duration of 9.0 (4.8, 19.1) months, 12 patients (29%) experienced ≥1 syncopal episode. Cox regression analyses revealed that the number of previous syncopal episodes before treatment was a risk factor for syncopal recurrence (hazard ratio = 1.027, 95% confidence interval 1.009 - 1.045, P = 0.003). Moreover, 4 previous syncopal episodes were certified as the best cutoff value, and the Kaplan-Meier curves showed that the syncopal recurrence-free survival rate over time in patients with > 4 previous syncopal episodes was significantly lower than that in patients with ≤4 episodes (P = 0.019 at the log-rank test).

Conclusion

In a pediatric population with VVS while on the treatment of metoprolol, the number of previous syncopal episodes before treatment played a significant role in predicting syncopal recurrence.

Baseline Corrected QT Interval Dispersion Is Useful to Predict Effectiveness of Metoprolol on Pediatric Postural Tachycardia Syndrome

OBJECTIVES

The study was designed to explore the role of baseline-corrected QT interval dispersion (QTcd) in predicting the effectiveness of metoprolol on pediatric postural tachycardia syndrome (POTS).

METHODS

There were two groups in the study, the discovery group and the validation group. The children with POTS in the discovery group were treated with oral metoprolol, with the completed necessary medical records, head-up tilt test (HUTT), blood chemistry, and 12-lead ECG before treatment at the pediatrics of Peking University First Hospital, China. According to whether the symptom score (SS) was reduced by more than 2 points after administration with oral metoprolol as compared with that before treatment, the children with POTS were separated into responders and non-responders. The demographic characteristics, hemodynamic indicators, and the QTcd of the two groups were compared, and the estimate of the baseline QTcd in predicting the treatment response to metoprolol was tested through a receiver operating characteristic (ROC) analysis. Other 24 children suffering from POTS who were, administrated with metoprolol at the pediatrics of Peking University First Hospital were included in the validation group. The sensitivity, specificity, and accuracy of the baseline QTcd in the prediction of the effectiveness of metoprolol on POTS were validated in children.

RESULTS

The pre-treatment baseline QTcd in responders treated with metoprolol was longer than that of the non-responders in the discovery group [(66.3 ± 20.3) ms vs. (45.7 ± 19.9) ms, p = 0.001]. The baseline QTcd was negatively correlated with SS after metoprolol treatment (r = -0.406, p = 0.003). The cut-off value of baseline QTcd for the prediction of the effectiveness of metoprolol on pediatric POTS was 47.9 ms, yielding a sensitivity of 78.9% and a specificity of 83.3%, respectively. The validation group showed that the sensitivity, specificity, and accuracy of the baseline QTcd ≥ 47.9 ms before treatment for estimating the effectiveness of metoprolol on POTS in children were 73.7, 80.0, and 75.0%, respectively.

CONCLUSION

Baseline QTcd is effective for predicting the effectiveness of metoprolol on pediatric POTS.

Repolarization disparity as a predictor of response to Head up Tilt-table Test in pediatric syncope

BACKGROUND

Head up Tilt-table Test (HUTT) is a practical examination of the most common type of pediatrics syncope. The electrocardiographic (ECG) changes during this test, show the autonomic defects that cause neuraly-mediated syncope in response to tilting process.

METHODS

All pediatric syncope patients referred to our center in a 1-year period, were included in the study. HUTT was performed and patients were classified into two groups of Negative and Positive HUTT results, and the latter group was subclassified as three subgroups of "vasodepressor", "cardioinhibitory" and "mixed type" responses to HUTT. QT and corrected QT (QTc) dispersion was measured by the baseline standard 12-lead ECG obtained before HUTT.

RESULTS

Eighty-six patients with a mean age of 12.19 ± 5.34 were included. Patients with positive HUTT were significantly younger and male gender was more prevalent in this group. Mean QT dispersion was significantly higher in patients with positive HUTT result and also in patients with mixed response to HUTT compared to isolated vasodepressor response. Duration of QTc interval did not change between different study groups. Reciever-Operating-Characteristic (ROC) analysis showed that QT dispersion higher than 32 ms is a significant predictor of positive HUTT result (with 92% sensitivity and 98% specificity) and values higher than 40 ms can predict the mixed type of response to HUTT (with 84% sensitivity and 63% specificity).

CONCLUSIONS

Baseline myocardial repolarization disparity significantly correlates with susceptibility to symptomatic vasovagal syncope. This pathology seems to play its role mainly via excessive vagotonic response to sympathetic activation during HUTT process (known as cardioinhibitory response).

Portable single-lead electrocardiogram device is accurate for QTc evaluation in hospitalized patients

Background

Many commonly used drugs can prolong the QTc interval (QTc), which can lead to potentially life-threatening arrhythmias. In the current era of the COVID-19 pandemic, it is worth mentioning that the disease itself and several drugs used for its treatment have been associated with QTc prolongation.

Objective

To evaluate the agreement and clinical precision of a portable single-lead electrocardiogram (ECG) device to measure the QTc interval compared to the standard 12-lead ECG.

Methods

In sequential tests, QTc of ECG recordings obtained with the KardiaMobile (KM-1L) device (AliveCor, San Francisco, CA) were compared to QTc obtained with conventional 12-lead ECG. Agreement was evaluated using Bland-Altman plots and Lin’s concordance coefficient. Consistency between the 2 devices in determining QTc prolongation (QTc ≥470 ms in males or ≥480 ms in females) was evaluated with kappa statistics.

Results

A total of 128 patients with a presumed or confirmed diagnosis of COVID-19 admitted to a university hospital were included. QTc intervals measured with KM-1L were similar to QTc measured with conventional ECG (442.45 ± 40.5 vs 441.65 ± 40.3 ms, P = .15). Bland–Altman analysis showed no significant difference in QTc values (average difference of -0.797, 95% limits of agreement:-13.179; 11.585). Lin’s concordance coefficient showed an excellent agreement (0.988, P < .001). Concordance between the 2 devices for determining QTc prolongation was excellent (kappa >0.90).

Conclusion

ECG recordings obtained with KM-1L allow an accurate QTc interval assessment. Considering its simplicity of use, this approach has advantages over conventional ECG and can provide an alternative for the evaluation of QTc in hospitalized patients, during the current time of the COVID-19 pandemic and beyond.

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.

Alterations in Plasma Oxidative Stress Markers After Laparoscopic Operations of the Upper and Lower Abdomen

The patient’s position during laparoscopic surgery can have a clinically relevant effect on lower limb and splanchnic circulation; this factor has not yet been investigated with respect to oxidative stress markers. In order to assess this effect, a prospective clinical trial was designed wherein 2 groups of patients were studied. In group A, 15 patients underwent upper abdominal nonhepatobiliary operations (13 modified Nissen fundoplications and 2 Taylor vagotomies) in the head-up position. In group B, 15 patients underwent lower abdominal operations (10 laparoscopic colectomies and 5 inguinal hernia repairs) in the head-down position. The pneumoperitoneum was maintained at 14 mm Hg in all cases. Plasma concentrations of thiobarbituric-acid reactive substances (TBARS), a marker of lipid peroxidation, plasma total antioxidant status (TAS), and serum uric acid concentrations were measured preoperatively, 5 minutes after deflation of the pneumoperitoneum, and 24 hours postoperatively. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) serum activities were measured preoperatively and 24 hours postoperatively. In group A, there was a significant increase in TBARS levels (p<0.005) immediately after deflation of the pneumoperitoneum and a significant decrease in TAS and uric acid levels (p<0.005) in the first postoperative day. There was also a significant postoperative elevation in both ALT and AST activities (p<0.001). In group B, no significant increase was found in postoperative TBARS or transaminase levels. TAS and uric acid levels decreased significantly in the first postoperative day (p<0.05) and (p<0.005, respectively). In conclusion, these results show that a combination of pneumoperitoneum and the head-up position causes significant increase in lipid peroxidation, decrease in plasma TAS, and increase in transaminases. The mechanism responsible for these events could be the low-flow ischemia-reperfusion syndrome induced by the pneumoperitoneum and aggravated by the head-up position.

Electrocardiography-Derived Predictors for Therapeutic Response to Treatment in Children with Postural Tachycardia Syndrome

OBJECTIVE

To explore whether electrocardiography (ECG) variables could be used to predict responses to physical treatment in children with postural tachycardia syndrome (POTS).

STUDY DESIGN

Forty children with POTS and 32 healthy controls were enrolled in this study. General information and hemodynamic and supine ECG variables, including QT interval dispersion (QTd), were collected. The children with POTS received physical treatment and 3 months of follow-up. A receiver-operating characteristic curve was used to evaluate the value of ECG variables for predicting the effectiveness of physical treatment.

RESULTS

Compared with the healthy children, the children with POTS had longer baseline QTd and heart rate (HR)-corrected QTd (QTcd), but shorter minimum QT intervals (QTmin) and minimum HR-corrected QT intervals (P < .05). In children with POTS, responders to physical treatment had a longer baseline time between QRS complexes (RR) interval of minimum QT interval and a longer QTcd compared with nonresponders. A longer QTcd was a significant risk factor for the presence of POTS (OR, 1.022; P = .02) and for undesirable responses to physical treatment in children with POTS (OR, 1.044; P = .03). Baseline QTcd was positively correlated with the HR elevation from supine to upright seen in children with POTS (r = 0.348; P = .003). Receiver operating characteristic curve analysis demonstrated an area under the curve of 0.73, and using 43.0 msec as a cutoff of QTcd yielded a sensitivity of 90% and a specificity of 60%.

CONCLUSION

QTcd might be useful for predicting the effectiveness of physical treatment for POTS in children.

Increased P-wave and QT dispersions necessitate long-term follow-up evaluation of Down syndrome patients with congenitally normal hearts

Reports state that Down syndrome (DS) patients with congenitally normal hearts might experience the development of cardiac abnormalities such as cardiac autonomic dysfunction, valvular lesions, bradycardia, and atrioventricular block. However, the presence of any difference in terms of P-wave dispersion (PWd) and QT dispersion (QTd) was not evaluated previously. This study prospectively investigated 100 DS patients with structurally normal hearts and 100 age- and sex-matched healthy control subjects. Standard 12-lead electrocardiograms were used to assess and compare P-wave and QT durations together with PWd and QTd. The median age of the DS patients and control subjects was 48 months. Heart rates and P-wave and QT dispersions were significantly greater in the DS group than in the control group (113 ± 22.9 vs 98.8 ± 16.6 bpm, p < 0.001; 31.3 ± 9.5 vs 24 ± 8.6 ms, p < 0.001; and 46.6 ± 15.9 vs 26 ± 9.1 ms, p < 0.001, respectively). A positive correlation was found between PWd and age in the DS patients (p < 0.05; r = 0.2). All children with DS should be followed up carefully with electrocardiography in terms of increased P-wave and QT dispersions even in the absence of concomitant congenital heart disease for management of susceptibility to arryhthmias.

QT wave dispersion in patients with panic disorder

OBJECTIVE

QT dispersion (QTd), defined as the maximal inter-lead difference in QT intervals on 12 leads of the surface electrocardiogram (ECG), reflects the regional heterogeneity of ventricular repolarization and has been suggested as an important marker for risk of arrhythmia in addition to the QT interval. Some investigators proposed that it might be a predisposing factor for arrhythmic events and sudden death. Thus, we aimed to investigate whether QTd differs in patients with panic disorder from that in healthy controls.

METHODS

In 40 panic disorder patients and 40 healthy controls, Q(max), Q(min), and QTd values were measured. In addition, the Hamilton depression rating scale and the panic agoraphobia scale were scored for both patients and healthy volunteers.

RESULTS

Q(max) and Q(min) values in the panic disorder patients were significantly higher than those in healthy controls. The mean corrected QTd was significantly greater in the patients than in the controls. One-way analysis of covariance (ANCOVA; using left atrial size, age and heart rate as covariates) also corrected the significant difference. In addition, ANCOVA revealed a significant main effect for the diagnosis, indicating a significantly higher QTd for patients compared with controls.

CONCLUSION

QTd might be associated with panic disorder. Future studies in larger samples evaluating the effects of treatment are required.

Heart rate-corrected QT interval predicts mortality in glyphosate-surfactant herbicide-poisoned patients

BACKGROUND

Glyphosate-surfactant herbicide is promoted by the manufacturer as having no risks to human health. Glyphosate surfactant has recently been used with increasing frequency in suicide attempts, so clinical toxicologists occasionally encounter cases of severe systemic toxicity. The purpose of this study was to identify the early predictive factors of patients at risk for mortality and the usefulness of the corrected QT interval (QTc interval) for predicting mortality from glyphosate-surfactant intoxication.

METHODS

This was a retrospective cohort study conducted from January 2005 to December 2012. A total of 153 patients with acute glyphosate-surfactant ingestion were included. To identify the predictive factors for mortality, objective variables easily assessed at presentation including previously reported predictive factors for mortality and severity were retrospectively analyzed for their association with mortality using univariate and multiple logistic analyses.

RESULTS

The average age of the patients was 56 years (range, 19-93 years). Of the 153 patients, 19 (12.4%) died. The most common abnormal electrocardiogram findings were prolonged QTc interval followed by intraventricular conduction delay and first-degree atrioventricular block. Nonsurvivors had a significantly more prolonged QTc interval when compared with that of survivors (survivors: 453.4 ± 33.6 milliseconds vs nonsurvivors: 542 ± 32.0 milliseconds, P < .001). Corrected QT interval and age were associated with a significantly increased risk of death in a multiple logistic regression. In a receiver operating curve analysis, the QTc interval had significant discriminatory power.

CONCLUSION

Prolonged QTc interval seems to be a useful prognostic factor for mortality in patients intoxicated with glyphosate-surfactant herbicide.

QT interval dispersion pattern in patients with acute ischemic stroke: Does the site of infarction matter?

BACKGROUND

QT interval dispersion (QTD) is an independent predictor of outcome following acute neurological events.

OBJECTIVES

To explore QTD patterns and their relation to the affected cerebral region in patients with acute ischemic stroke.

METHODS

Thirty patients with first acute ischemic stroke (the first stroke the patients had ever experienced) (study group) and 30 healthy controls (control group) were enrolled. Patients underwent magnetic resonance imaging to confirm and localize cerebral damage. Patients in the study group were further subdivided according to the site of infarction into four subgroups - namely, cortical, subcortical, brain stem and cerebellar infarctions, as well as according to insular involvement. All included subjects underwent 12-lead electrocardiography to measure QTD and corrected QT dispersion (QTcD).

RESULTS

In the study group, both QTD and QTcD on the first hospitalization day were significantly higher than in the control group (P<0.05 for both). Similarly, in the study group, both QTD and QTcD values on the first hospitalization day were significantly higher than the respective values on the third day (P<0.001 for both). No significant differences were found among the four territorial subgroups, or between right- and left-sided subgroups, regarding QT interval measurements, whether on the first or third day (P>0.05 for all). However, 'first-day' QTD and QTcD of patients with insular involvement were significantly higher than in those without such involvement (P<0.001 for both).

CONCLUSIONS

Both QTD and QTcD increased significantly in patients with acute ischemic stroke during the first hospitalization day. This increase of 'first-day' QTD and QTcD was significantly higher in patients with insular involvement than in those without such involvement.

Hypotensive bradycardic events during shoulder arthroscopic surgery under interscalene brachial plexus blocks

Sudden, profound hypotensive and bradycardic events (HBEs) have been reported in more than 20% of patients undergoing shoulder arthroscopy in the sitting position. Although HBEs may be associated with the adverse effects of interscalene brachial plexus block (ISBPB) in the sitting position, the underlying mechanisms responsible for HBEs during the course of shoulder surgery are not well understood. The basic mechanisms of HBEs may be associated with the underlying mechanisms responsible for vasovagal syncope, carotid sinus hypersensitivity or orthostatic syncope. In this review, we discussed the possible mechanisms of HBEs during shoulder arthroscopic surgery, in the sitting position, under ISBPB. In particular, we focused on the relationship between HBEs and various types of syncopal reactions, the relationship between HBEs and the Bezold-Jarisch reflex, and the new contributing factors for the occurrence of HBEs, such as stellate ganglion block or the intraoperative administration of intravenous fentanyl.

QTc values among children and adolescents presenting to the emergency department

OBJECTIVE

Long-QT syndrome (LQTS) is both underdiagnosed and overdiagnosed. Many patients are incorrectly diagnosed as having LQTS after presenting to an emergency department (ED) with presyncope/syncope and demonstrating "borderline" QT-interval prolongation (QTc ≥ 440 milliseconds) in a sentinel ED-obtained electrocardiogram (ECG). We sought to evaluate the distribution and clinical significance of QT intervals in the ED.

METHODS

We retrospectively reviewed data for all patients 22 years of age or younger (N = 626; 369 females; age, mean ± SD: 17 ± 5 years) who had ECGs obtained in our ED between July 1, 2007, and June 30, 2008. A total of 223 patients were excluded because of known structural heart disease, arrhythmias, electrolyte abnormalities, or exposure to QT-interval-prolonging medications.

RESULTS

The average QTc was 428 ± 28 milliseconds (range: 344-566 milliseconds), and approximately one-third of patients had QTc values of ≥440 milliseconds (females: 41%; males: 21%). Overall, 104 patients presented with presyncope/syncope, of whom 14 (13%) had follow-up ECGs. On follow-up, these patients demonstrated significant decreases in QTc values of 33 ± 43 milliseconds (P < .04). Only 8 (31%) of 26 patients with presyncope/syncope with borderline QT values had follow-up ECGs performed, in 5 of which the QTc values were decreased significantly. No patients ultimately received LQTS diagnoses.

CONCLUSIONS

In the ED setting, approximately one-third of pediatric patients exhibited QTc values of ≥440 milliseconds and had significant normalization of QTc values in follow-up evaluations. First-time ECGs obtained after a syncopal episode must be interpreted with caution, particularly in the context of so-called borderline QT intervals.

Intravenous fentanyl during shoulder arthroscopic surgery in the sitting position after interscalene block increases the incidence of episodes of bradycardia hypotension

Background

Episodes of bradycardia hypotension (BH) or vasovagal syncope have a reported incidence of 13-29% during arthroscopic shoulder surgery in the sitting position after an interscalene block (ISB). This study was designed to investigate whether intravenous fentanyl during shoulder arthroscopy in the sitting position after ISB would increase or worsen the incidence of BH episodes.

Methods

In this prospective study, 20 minutes after being in a sitting position, 160 patients who underwent ISB were randomized to receive saline (S, n = 40), 50 µg of fentanyl (F-50, n = 40), 100 µg of fentanyl (F-100, n = 40) or 30 mg of ketorolac (K-30, n = 40) randomly. We assessed the incidence of BH episodes during the operation and the degree of maximal reduction (Rmax) of blood pressure (BP) and heart rate (HR).

Results

The incidence of BH episodes was 10%, 15%, 27.5% and 5% in the S, F-50, F-100 and K-30 groups, respectively. Mean Rmax of systolic BP in the F-100 group was significantly decreased as compared to the S group (-20.0 ± 4.5 versus -6.3 ± 1.6%, P = 0.004). Similarly, mean Rmax of diastolic BP in the F-100 group was also significantly decreased (P = 0.008) as compared to the S group.

Conclusions

These results suggest that fentanyl can increase the incidence of BH episodes during shoulder arthroscopic surgery in the sitting position after ISB.

QT dispersion in patients with pulmonary embolism

BACKGROUND

Various ECG patterns have been associated with acute pulmonary embolism. However, there is no data regarding the association between QT interval measurements and pulmonary embolism. We aimed to investigate the association between QT dispersion and the severity of pulmonary embolism (PE).

METHODS

One hundred twenty-nine pulmonary embolism patients (mean age 58 ± 16.5 years) with ECGs obtained within the first 24 hours of hospital admission were included in the study. Patients were classified into low, intermediate and high-risk groups. We retrospectively measured ECG scores; maximum and minimum corrected QT intervals (QTc(max) and QTc(min)) and corrected QT interval dispersion (QTcd) in each risk group of patients.

RESULTS

There was an increasing ECG score through from low to high-risk PE [3 (Interquartile Range, IQR: 2), 5 (IQR: 6) and 10 (IQR: 7) p < 0.0001]. QT interval analysis showed that QTcd was higher in high-risk group than in low and intermediate-risk groups (59.5 ± 23.4, 69.2 ± 21, 95.9 ± 33.2, p <0.001 and p = 0.01, respectively). Patients who died after diagnosis had significantly higher QTcd values at baseline compared with the QTcd values of surviving patients (89.1 ± 45.5 to 65 ± 22.9, p = 0.001). The sensitivity of QTcd > 71.5 ms for prediction of mortality was 71% with a specificity of 73% (p = 0.001). We observed a strong correlation between QTcd and ECG score values (r = 0.69, p< 0.001). There was also a correlation between QTcd values and pulmonary artery pressure (PAP) (r = 0.27, p = 0.05).

CONCLUSION

QTcd is significantly increased in high-risk PE patients compared to intermediate and low-risk patients. In addition, QTcd is significantly correlated with ECG score and PAP.

Alterations in QT dispersion in the surface electrocardiogram of female adolescent inpatients diagnosed with bulimia nervosa

Increased QT dispersion (QTd) reflects cardiac autonomic imbalance and indicates elevated risk for cardiac arrhythmias. In the present study, we assessed heart rate, QT and corrected QT intervals, and QTd in 20 acutely ill bulimia nervosa adolescent inpatients on admission and discharge. A significant decrease in QTd was found between admission and discharge (67 +/- 13 milliseconds vs 55 +/- 12 milliseconds, respectively; P = .0005). The decrease in QTd values correlated significantly with the decrease in the frequency of bingeing/purging behaviors (r = 0.51, P = .022). No significant correlations were found between the electrocardiographic indices and other clinical and laboratory measures. The elevated QTd in malnourished bulimia nervosa patients might indicate a cardiac autonomic imbalance that is most likely corrected after symptomatic improvement.

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.

Factors contributing to episodes of bradycardia hypotension during shoulder arthroscopic surgery in the sitting position after interscalene block

Background

Arthroscopic shoulder surgery has been performed in the sitting position under interscalene block (ISB). Bradycardia hypotension (BH) episodes have a reported incidence of 13-29% in this setting. We performed a retrospective study to investigate contributing factors to the occurrence of BH episodes.

Methods

According to BH episodes, we divided 63 patients into two groups: BH group (n = 13) and non-BH group (n = 50). Anesthetic records and block data sheets were reviewed for demographic data, intraoperative medications, sites of ISB, use of epinephrine in local anesthetics, degree of sensory blockade, and percent change of heart rate or systolic blood pressure (SBP). Statistical analysis was done using Chi square test and Student's t-test.

Results

There were no significant differences in the use of epinephrine in local anesthetics between the two groups. The location of ISB site was different between the two groups in that there were relatively more right-sided ISBs in the BH group than in the non-BH group (P = 0.048). The degree of sensory blockade was lower, but not significantly, in the C8 and T1 dermatomes of the BH group than in the non-BH group (P = 0.060 and 0.077, respectively). There was a relatively higher incidence of fentanyl supplementation in the BH group than in the non-BH group (P = 0.000).

Conclusions

These results suggest that right ISB and perioperative supplementation of fentanyl due to incomplete block are possible contributing factors to the occurrence of BH episodes in the sitting position during shoulder surgery using ISB.

Effect of telmisartan on QT interval variability and autonomic control in hypertensive patients with left ventricular hypertrophy

OBJECTIVES

The aim of the study was to examine the effect of the antihypertensive AT1 receptors antagonist telmisartan on cardiovascular autonomic function and QT dispersion in hypertensive patients with LVH.

METHODS

Twenty-five patients (18 males and seven women, mean age 49.8±5.2 years) with mild essential arterial hypertension and LVH were compared with 25 age-matched healthy controls. All the participants underwent a complete clinical examination, including electrocardiogram for QT interval measurements and 24h ambulatory ECG monitoring for measurement of heart rate variability. The ECG, 24h ambulatory ECG, and echocardiogram were repeated after eight weeks of treatment.

RESULTS

At baseline, hypertensive patients showed QT dispersion (p<0.001) and QTc dispersion (p<0.001) significantly higher than control subjects. An eight-week telmisartan treatment significantly reduced blood pressure (p<0.0001), without significant change in left ventricular mass. Telmisartan-based treatment induced an increased vagal activity without significant change of sympathetic activity and a reduction of QT dispersion (p<0.001) and QTc dispersion (p<0.001).

CONCLUSIONS

These data suggest that therapy with telmisartan significantly improves the sympathovagal balance increasing parasympathetic activity, and cardiac electrical stability reducing the heterogeneity of ventricular repolarization in hypertensive subjects. These effects could contribute to reduce arrhythmias as well as sudden cardiac death in at-risk hypertensive patients.

Changes in autonomic regulation and ventricular repolarization induced by subclinical hyperthyroidism

The aim of the present study was to evaluate the effect of subclinical hyperthyroidism (SHT) on cardiovascular autonomic function and ventricular repolarization.

METHODS

Thirty subjects (25 females; mean age 49.6 ± 9.8 years) with SHT, as judged by reduced TSH serum levels and normal free T4 and T3 serum levels, and 30 age and sex-matched control subjects underwent standard 12-lead ECG, and 24h ambulatory ECG monitoring. The dispersion of the QT interval, an index of inhomogeneity of repolarization, and the heart rate variability (HRV), a measure of cardiac autonomic modulation, were studied.

RESULTS

Patients with SHT showed higher QT dispersion (p<0.001) and lower HRV measures (0.01>p<0.001) than controls. In SHT patients, QT dispersion was inversely related to HRV (r=-0.47, p<0.01).

CONCLUSION

The results of the present study demonstrated that SHT is associated with a sympathovagal imbalance, characterized by increased sympathetic activity in the presence of diminished vagal tone, and with an increased inhomogeneity of ventricular recovery times. The assessment of HRV and QT dispersion in patients with SHT may represent a useful tool in monitoring the cardiovascular risk of this condition.

Assessment of QT intervals and prevalence of short QT syndrome in Japan

BACKGROUND

Long QT syndrome causes ventricular tachyarrhythmias and sudden death. Recently, a short QT interval has also been shown to be associated with an increased risk of tachyarrhythmia and sudden death. However, the prevalence of short QT syndrome is not well-known.

HYPOTHESIS

The aim of this study was to assess the distribution of corrected QT intervals (QTc) and prevalence of short QT syndrome.

METHODS

This study comprised 12,149 consecutive subjects who received a consultation at Kanazawa University Hospital, Kanazawa, Japan, and had an electrocardiogram (ECG) between February 2003 and May 2004. Of these subjects, 1,165 subjects were excluded because of inappropriate ECGs, while the remaining 10,984 subjects had their last-recorded ECGs analyzed.

RESULTS

The QTc values showed a nearly normal distribution (408 +/- 25 msec(1/2)), and were significantly longer in females (412 +/- 24 msec(1/2)) than in males (404 +/- 25 msec(1/2)) (p < 0.05). Among 5,511 males, 69 subjects (1.25%) exhibited QTc < 354 msec(1/2) (2 standard deviations [SDs] below the mean in males), and among 5,473 females, 89 subjects (1.63%) exhibited QTc < 364 msec(1/2) (2 SDs below the mean in females). Only 3 subjects (0.03% in all subjects and 0.05% in males) exhibited QTc < 300 msec(1/2), however, none had clinical symptoms of short QT syndrome.

CONCLUSIONS

Short QT syndrome may be very rare.

Effect of mood states on QT interval and QT dispersion in eating disorder patients

AIM

Prolonged QT interval and QT dispersion have been reported in patients with eating disorders. Although the factors that cause prolongation remain unclear, mood states such as anxiety have been reported to influence QT interval and dispersion, probably via the autonomic nervous system. Therefore the aim of the present paper was to investigate mood effect on prolonged QT interval and QT dispersion.

METHOD

The subjects were 47 female anorexia nervosa (AN) and 48 female bulimia nervosa (BN) patients. In all of the patients, serum electrolyte levels were normal. QT interval and QT dispersion were measured from 12-lead electrocardiographic recordings. Mood states in each patient were measured using a Profile of Mood States (POMS) evaluation, and the patients were divided into high- and low-score groups for each POMS subscale. The differences in QT variables were compared between the two groups for each subscale.

RESULTS

In the BN group, QT interval and QT dispersion in the high depression score group were significantly longer than those in the low depression score group, and QT dispersion was significantly greater in the high anxiety score group than in the low anxiety score group. In addition, QT interval and QT dispersion were significantly correlated with depression scores. In the AN group there were no significant differences in QT interval or QT dispersion between the high- and low-score groups for any POMS subscale.

CONCLUSIONS

BN patients with worse states of depression or anxiety had longer QT intervals and larger QT dispersion. In BN patients, mood disturbance might increase the risk of arrhythmias.

Changes in heart rate variability and QT dispersion in patients with overt hypothyroidism

OBJECTIVE

The aim of the present study was to evaluate the effect of clinical hypothyroidism on cardiovascular autonomic function and ventricular repolarization.

DESIGN AND METHODS

We studied 31 patients (22 females and 9 males; mean age 53.6+/-11.8 years) with overt hypothyroidism (TSH=56.2+/-14.7 microU/ml, low free thyroxine (T4), free tri-iodothyronine (T3)) and 31 euthyroid controls, to investigate the dispersion of the QT interval in electrocardiogram (ECG) (an index of inhomogeneity of repolarization) and heart rate variability (HRV; a measure of cardiac autonomic modulation). The hypothyroid patients and controls underwent a full medical examination, standard 12-lead ECG, and 24-h ambulatory ECG monitoring. The hypothyroid patients were re-examined after 6 months of treatment with L-T4.

RESULTS

Patients with hypothyroidism showed higher QT dispersion and lower HRV measures than controls (P<0.01 or P<0.001). In hypothyroid patients, standard deviation of all R-R intervals was inversely related (by simple regression) to serum (log)TSH levels (r=-0.47, P=0.008), while QT dispersion (r=0.50, P=0.004) and QTc dispersion (r=0.46, P=0.008) were directly related to (log)TSH. Parameters of HRV improved after 6 months of L-T4 treatment, with the correction of hypothyroidism, becoming comparable with those of the control subjects, whereas the QT and QTc dispersion results were found to be only partially restored, remaining higher than the controls.

CONCLUSIONS

The results of the study demonstrate that hypothyroidism is associated with a decreased sympatho-vagal modulation of the heart rate and with an increased inhomogeneity of ventricular recovery times. The assessment of HRV and QT dispersion in patients with overt hypothyroidism may represent a useful tool in monitoring the cardiovascular risks.

Alterations in QT dispersion in the surface electrocardiogram of female adolescents diagnosed with restricting-type anorexia nervosa

OBJECTIVE

QT dispersion (QTd), defined as the difference between the longest interval and the shortest interval in the 12-lead electrocardiogram (ECG), is a measure of myocardial repolarization inhomogeneity. We assessed QTd in malnourished anorexia nervosa (AN) inpatients and following weight restoration.

METHODS

QTd analysis, anthropometric evaluations, and laboratory tests were carried out in 30 malnourished female adolescent AN restricting-type (AN-R) inpatients and following weight restoration.

RESULTS

A significant increase was found in weight/height ratio and body mass index from malnourished stage to weight restoration, paralleled by a significant decrease in QTd (70+/-16 vs. 47+/-16 ms; P<.0001). No correlations were found between ECG indices and anthropometric and laboratory measures.

CONCLUSION

Elevated QTd in malnourished AN-R inpatients may indicate possible cardiac autonomic imbalance and/or myocardial damage, likely corrected following weight restoration.

QT interval and dispersion in very young children treated with antipsychotic drugs: a retrospective chart review

OBJECTIVES AND BACKGROUND

QT dispersion (QTd) is a measure of interlead variations of the surface 12-lead electrocardiogram (ECG). Increased QTd, found in various cardiac diseases, reflects cardiac instability and risk for lethal cardiac arrhythmias. Research suggests a link between psychotropic treatment, ECG abnormalities (QT prolongation), and increased sudden cardiac mortality rates. Reports of sudden death in children treated with psychotropic drugs have raised concerns about cardiovascular monitoring and risk stratification. QTd analysis has not been investigated in very young children treated with antipsychotic drugs. In the present retrospective chart review study, we calculated QT interval, QTd, and their rate-corrected values in very young children treated with antipsychotics.

METHODS

The charts of 12 children (ages 5.8 +/- 0.98 yr; 4 girls, 8 boys) were examined before initiation of antipsychotic treatment [risperidone (n = 7), clotinapine (n = 1), and propericiazine (n = 4)] and during the maintenance period after achieving a positive clinical response. Three children were concomitantly maintained on methylphenidate. QT interval, QTd, and their rate-corrected values were calculated.

RESULTS

QT interval, QTd, and their rate-corrected values were all within normal values both before and after successful drug treatment.

CONCLUSIONS

This preliminary, naturalistic, small-scale study suggests that antipsychotic treatment, with or without methylphenidate, in very young children is not commonly associated with significant alterations of QT interval and dispersion, suggesting the relative safety of these agents in this unique age group.

Effects of Positioning in Laparoscopic Adnexal Surgery on QT Dispersion and Heart Rate Variability Under Sevoflurane Anesthesia

PURPOSE

This study compared the intraoperative changes in the corrected QT dispersion and heart rate variability, predictors of autonomic cardiac function, in laparotomic and laparoscopic adnexal surgery.

MATERIALS AND METHODS

The study was conducted on 46 American Society of Anaesthesiologists class I/II patients, aged 33-51 years, randomized to one of two groups, for elective gynecologic laparotomy or laparoscopy for a benign adnexal mass. Anesthesia was induced and maintained with sevoflurane. Corrected QT dispersion and spectral powers of heart rate variability were measured at baseline, before the induction of anesthesia, and intraoperatively during the adnexal surgery for 15 minutes. The lithotomy and Trendelenburg positions were set at 145 degrees and 30 degrees between thigh and body, respectively. Pneunoperitoneum was established at 12 mm Hg. Laparoscopic surgery was performed via one principal and two ancillary ports. Data were analyzed using the Wilcoxon and Mann-Whitney tests.

RESULTS

A significant increase was observed in intraoperative standard deviation of RR interval values of heart rate variability in both groups compared to preoperative values (P < 0.05). The corrected QT dispersion and low and high frequency heart rate variability showed no significant changes between the two groups.

CONCLUSION

Gynecologic laparoscopy with pneumoperitoneum in the lithotomy and Trendelenburg positions is as safe as laparatomy and seems not to deteriorate the autonomic cardiac function.

Beneficial effect of deep breathing on premature ventricular complexes: can it be related to the decrease in QT dispersion?

It has been reported that deep breathing at 6 breaths/min is associated with reduction of premature ventricular complexes. The beneficial effect of deep breathing is supposed to be due to vagal modulation of sinoatrial and atrioventricular node. Beside the modulating effects of deep breathing, we believe that deep breathing, which is also used in yoga training, might have additional effects via decreasing QT dispersion.

An evaluation of the impact of gender and age on QT dispersion in healthy subjects

OBJECTIVES

To determine if gender, age, and gender per age category, have an impact on QT and QTc dispersion in healthy volunteers.

METHODS

This study was undertaken in 150 patients (50 per age group, 75 males, 75 females). The age groups included young (20-40 years), middle-aged (41-69 years) and elderly (> 70 years) subjects. The QT intervals on a 12 lead ECG were determined and Bazett's formula was used to derive the QTc intervals. The QT and QTc dispersion were determined by subtracting the shortest QTc interval from the longest on each 12-lead recording.

RESULTS

Males had higher QT dispersion than females (50 +/- 22 vs 42 +/- 18 ms, P = 0.017) but QTc dispersion was not significantly changed. No significant differences were seen among the different age categories for QT or QTc dispersion. In elderly subjects, males had higher QT and QTc dispersion than females (54 +/- 23 vs 42 +/-15 ms, P = 0.039 and 63 +/- 23.7 vs 48 +/- 21 ms, P = 0.032, respectively).

CONCLUSIONS

When evaluating the effect of gender in different age categories, elderly males have significantly greater QT and QTc dispersion than elderly female subjects. No other gender differences were noted for QT or QTc dispersion in the other two age categories. When evaluating a population of healthy volunteers, regardless of age, gender has an impact on QT dispersion but no significant interaction with QTc dispersion. Evaluating age without dividing the data by gender yields no significant differences in QT or QTc dispersion.

Heart rate variability and QT dispersion in patients with subclinical hypothyroidism

The effect of subclinical hypothyroidism (SH) on cardiovascular autonomic function and ventricular repolarization has not been yet elucidated. The aim of the present study was to evaluate the dispersion of QT interval, i.e. an index of inhomogeneity of repolarization, and heart rate variability (HRV), i.e. a measure of cardiac autonomic modulation, in SH patients.

METHODS

The study included 42 patients (29 women and 13 men; mean age 53.2+/-14.2 years; body surface area 1.76+/-0.14 m2) with SH, as judged by elevated serum TSH levels (>3.6 mIU/l; range, 3.8-12.0) and normal free thyroid hormones (FT4 and FT3) and 30 euthyroid volunteer. Subjects with cardiac, metabolic, neurological disease or any other systemic disease that could affect autonomic activity were excluded from the study. Patients with SH and control subjects underwent a full history, physical examination, standard 12-lead ECG, and 24-h ambulatory ECG monitoring. To evaluate the effect of treatment with L-thyroxine on QT dispersion and HRV, 15 patients with SH were randomly assigned to receive therapy with L-thyroxine. All the subjects were evaluated at enrolment and after 6 months.

RESULTS

Patients with SH showed higher QT dispersion and lower HRV measures than healthy controls (P<0.01 for all). In SH patients, the standard deviation of N-Ns (SDNN) was negatively related to TSH (r=-0.42, P=0.006), while low frequency (LF)/high frequency (HF) ratio was positively related to TSH (r=0.42, P=0.006). Moreover, in SH patients both QT dispersion and QTc dispersion were positively related to TSH (r=0.64 and r=0.63, P<0.001 for both). After 6 months, the patients treated with L-tiroxine exhibited a reduction of QT dispersion and an increase of HRV parameters.

CONCLUSION

The results of the present study demonstrated that SH can alter autonomic modulation of heart rate and cause increased inhomogeneity of ventricular recovery times. Accordingly, early L-thyroxine treatment may be advised not only to prevent progression to overt hypothyroidism but also to improve abnormal cardiac autonomic function and ventricular repolarization inhomogeneity.

Comparison Between Intraperitoneal CO2 Insufflation and Abdominal Wall Lift on QT Dispersion and Rate-corrected QT Dispersion During Laparoscopic Cholecystectomy

This study compared the effect of intraperitoneal CO2 insufflation with abdominal wall lift on RR interval, QT interval, the rate-corrected QT (QTc) interval, QT dispersion (QTD), and the rate-corrected QTD (QTcD) using computerized measurement during laparoscopic cholecystectomy. Thirty patients scheduled for laparoscopic cholecystectomy were randomly assigned to 2 groups: intraperitoneal CO2 insufflation (CO2 group) or abdominal wall lift (lift group). A 12-lead electrocardiogram was monitored to measure parameters. The RR interval, QT interval, and QTc interval did not change significantly during the study in both groups. The QTD and QTcD in the CO2 group increased significantly during CO2 insufflation, and were significantly higher than those of the lift group. Statistically significant increases of QTD and QTcD, which are associated with an increased risk of arrhythmias and cardiac events, occur during CO2 insufflation, and QTD and QTcD in the CO2 group were significantly higher than those of the lift group.

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

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

Circadian rhythm of the QT interval dispersion in healthy subjects. Correlation with heart rate variability circadian pattern

Circadian variation of QT interval dispersion (QTd) and heart rate variability spectral indices was evaluated in healthy persons in 24-hour 3-lead electrocardiogram. Mean values, SD, and SD/mean were evaluated for 24 hours, each hour separately and in night, day, and morning periods. Table Curve 2D and multiple regression were applied to find correlations between parameters. In 50% of subjects, a significant negative correlation was revealed between QTd and HF. Also, in 50% of persons, a significant positive correlation was found between QTd and low frequency/high frequency. After adjustment for periods, correlations were only observed during morning hours. With Table Curve 2D, 2 models of correlations between QTd and HF were found. Multiple regression analysis revealed relations between mean QTd and R-R as well as mean QTd and HF. It is possible that it is sympathovagal balance, as reflected in heart rate variability, and not the tone of both autonomic components that affects QTd variability.

Regulation of QT indices mediated by autonomic nervous function in patients with type 2 diabetes

Both the QT interval and QT dispersion in diabetic patients have been reported to increase with the progression of cardiac autonomic neuropathy and to have a prognostic value. We assessed the cardiac autonomic influences on QT indices using the measurements of baroreflex sensitivity, heart rate variability, and cardiac (123)I-metaiodobenzylguanidine scintigraphic findings in patients with type 2 diabetes mellitus. Forty-two consecutive patients with type 2 diabetes (mean+/-SD: 54+/-10 years, 22 women and 20 men) were studied. Baroreflex sensitivity negatively correlated with the maximum and minimum QTc intervals as well as QT/QTc dispersion. However, the high-frequency power and the ratio of low-frequency power to high-frequency power of heart rate variability did not correlate with any QT indices. The percent washout rate of (123)I-metaiodobenzylguanidine positively correlated with QT/QTc dispersion, but not with maximum and minimum QTc intervals. Our findings suggest that cardiac vagal dysfunction is related to QT interval prolongation while both sympathetic and vagal dysfunctions are related to increased QT dispersion in type 2 diabetic patients. Baroreflex sensitivity and percent washout rate of (123)I-metaiodobenzylguanidine may be useful parameters indicating the abnormalities of the cardiac ventricular repolarization in this population.

Alterations in QT dispersion in medicated schizophrenia patients following electroconvulsive therapy

QT dispersion (QTd) is a measure of interlead variations of the surface 12-lead electrocardiogram (ECG). Increased QTd, found in various cardiac diseases, reflects cardiac instability and is associated with increased risk for cardiac death. Research suggests a link between antipsychotics, ECG abnormalities (QT prolongation) and increased sudden cardiac mortality rates. However, QTd analysis has been scarcely investigated in schizophrenia patients. We calculated QTd in 20 medicated psychotic inpatients with schizophrenia, before and 3 days after electroconvulsive therapy (ECT), concomitantly with Brief Psychiatric Rating Scale (BPRS) assessment. QT interval and the rate-corrected QT (QTc) were abnormally prolonged before ECT. However, although QT was significantly shortened, QTc showed only a marginal decrease after ECT. QTd, the rate-corrected QTd, as well as BPRS, showed a significant decrease after ECT. Further large-scale studies are warranted to determine if QTd can serve as a marker for response to ECT, and if it is a risk factor for sudden cardiac death in schizophrenia patients.

QT dispersion in patients with social phobia

BACKGROUND

QT dispersion (QTd) is the maximal interlead difference in QT interval on the surface 12-lead electrocardiogram (ECG). An increase in QTd is found in various cardiac diseases and reflects cardiac autonomic imbalance. It has recently been associated with increased anxiety levels, thereby predisposing affected individuals to fatal heart disease. This is the first study to assess QTd in social phobia, as a marker of anxiety-induced cardiac dysregulation.

METHODS

QTd and rate-corrected QTd were measured in 16 physically healthy and non-depressed outpatients with long-term (mean 28+/-12.2 years; age 37.9+/-9.6 years) social phobia (SP) and in 15 physically and mentally healthy age- and gender-matched controls. The Liebowitz Social Anxiety Scale (LSAS) was scored concomitantly. The intra- and inter-observer reproducibilities of QTd were highly correlated (r=0.96, P<0.001; r=0.74, P=0.002, respectively).

RESULTS

QTd and rate-corrected QTd were significantly higher in the patients with SP compared to the controls (70+/-21 versus 43+/-10 ms, P<0.001 and 75+/-23 versus 46+/-10 ms, P<0.001, respectively), and highly correlated with the two LSAS subscores.

CONCLUSIONS

Prolonged SP is associated with an increase in QTd. This association may result from prolonged anxiety and, in turn, a decrease in vagal modulation and/or increase in sympathetic modulation. Further large-scale epidemiological studies are needed to determine if increased QTd can serve as a trait/state marker, and if it is a risk factor for sudden cardiac death in patients with SP.

QT interval and QT dispersion increase in the elderly during laparoscopic cholecystectomy: a preliminary study

PURPOSE

To compare the influence of a longer duration of intraperitoneal CO2 insufflation with head-up tilt on electrocardiogram indices during laparoscopic cholecystectomy between elderly and younger patients.

METHODS

Twelve elderly and 12 younger patients were studied. In all patients, intraperitoneal CO2 insufflation was performed for more than 150 min in the head-up position. RR interval, QT interval, the rate-corrected QT (QTc) interval, QT dispersion (QTD) and the rate-corrected QTD (QTcD) were measured.

RESULTS

The QT interval and the QTc interval increased significantly from 120 to 150 min after CO2 insufflation in the elderly. The QTD and QTcD increased significantly during CO2 insufflation in both groups. Those were significantly greater in the elderly than in younger patients from 120 to 150 min after CO2 insufflation.

CONCLUSION

Longer duration of CO2 insufflation with head-up tilt is associated with a prolongation of the QT interval and the QTD in elderly patients. The clinical significance of these findings remains to be determined.

Correlation between QT dispersion and burn severity

QT dispersion, defined as the maximal-minus-minimal QT interval on a 12-lead electrocardiogram, has emerged as a non-invasive measurement for quantifying the spatial inhomogeneity of ventricular repolarization under various conditions, including acute stress. Because burn injuries elicit acute stress reactions, it was hypothesized that QT dispersion increases with the severity of the burn injury. To test the hypothesis, 13 burned patients (age range of 22-76 years, nine males, ranging from 4.0 to 75.0% of total body surface area burned) in whom a measurable 12-lead electrocardiogram had been obtained within 4h after arrival at the emergency department were identified retrospectively, and their QTc intervals, i.e. QT intervals corrected for heart rate by the standard Bazett formula, were measured. QTc dispersion (QTcd) was then calculated, and correlations were assessed with burn severity (burn index, BI; prognostic burn index, PBI). Of the 13 patients, nine patients had a prolonged QTcd (>40 ms), and linear correlation analyses showed significant positive correlations between QTcd and both BI and PBI (r=0.61 and 0.62, respectively). In conclusion, QT dispersion was greater in the burned patients, and although the pathophysiology was unclear from the present study, the findings suggested that acute stress contributed to the spatial inhomogeneity of ventricular repolarization.

Development of a new method for assessing the cardiac baroreflex: response to downward tilting in patients with diabetes mellitus

OBJECTIVE

To investigate the clinical value of a new non-invasive method for assessing baroreflex sensitivity using downward tilting.

PATIENTS

34 patients with diabetes mellitus, mean (SD) age, 53.6 (11.8) years.

DESIGN

Arterial blood pressure and ECG were recorded simultaneously while the patients were on a tilt table. After 20 minutes at a 70 degrees upright tilt, the patients were returned to the supine position at a speed of 3.2 degrees /s (downward tilting baroreflex sensitivity test, DT-BRS). A beat to beat systolic blood pressure increase associated with a corresponding lengthening of the RR interval was noted during downward tilting. Baroreflex sensitivity was also assessed using the conventional method of an intravenous injection of phenylephrine (Phe-BRS). Heart rate variability was analysed during rest and tilting.

RESULTS

The slope of the regression line for systolic blood pressure v RR interval during downward tilting was highly correlated with Phe-BRS (r = 0.83, p < 0.0001). Both DT-BRS and Phe-BRS were correlated with the high frequency (HF) component of resting heart rate variability (p < 0.005) and with the ratio of the low frequency to the high frequency component (LF/HF) during upright tilting (p < 0.005). DT-BRS and Phe-BRS were also correlated with the difference between rest and tilting values of HF and LF/HF (p < 0.005).

CONCLUSIONS

DT-BRS provides a physiological, non-invasive method for determining baroreflex sensitivity and may be a useful index of reflex cardiac vagal and sympathetic function in patients with diabetes mellitus.