Corrected QT Dispersion Research Articles

Reversible Increases in Qt Dispersion and P Wave Dispersion during Carbon Monoxide Intoxication

Objectives Carbon monoxide (CO) is a potent myocardial toxin. We investigated the association between acute CO intoxication and electrocardiographic QT interval (QTmax/QTmin), corrected QT interval (cQTmax/cQTmin), QT dispersion (QTd) and corrected QT dispersion (cQTd), P wave duration (Pmax/Pmin) and P wave dispersion (Pd), which were known as predictors of ventricular arrhythmias, atrial fibrillation and sudden death. Methods Electrocardiography with 12-leads and blood gas were taken from 65 patients with CO intoxication as well as 65 control patients with similar age and gender distribution at the admission time to the emergency department and at the 4th hour post-therapy. The carboxyhaemoglobin (COHb) levels and the relationships with electrocardiographic parameters were studied. Results The mean COHb levels were 21.43±6.85% and 1.37±0.98% in intoxicated patients and in the control group respectively. QTmax, QTd, cQTmax, cQTd, Pmax, and Pd were found significantly higher in intoxicated patients when compared to the control group (373.98±40.35 vs. 355.98±32.88, p=0.006; 49.29±22.66 vs. 20.43±11.16, p<0.001; 455.38±30.72 vs. 419.57±22.27, p<0.001; 60.88±25.99 vs. 25.75±13.13, p<0.001; 107.91±13.28 vs. 96.65±12.65, p<0.001, 46.85±13.49 vs. 35.22±10.07, p<0.001 respectively). In Pearson correlation analysis, there were significant correlations between COHb level and QTmax, QTd, cQTmax, cQTd, Pmax and Pd (r=0.211, p=0.016; r=0.610, p<0.001; r=0.599, p<0.001; r=0.628, p<0.001; r=0.458, p<0.001; r=0.414, p<0.001 respectively). Conclusion A correlation between reversible increases in QTd, cQTmax, cQTd, Pmax and Pd in the electrocardiogram and COHb can be observed in acute CO intoxication patients.

Preoperative Abnormal P and QTc Dispersion Intervals in Patients with Metabolic Syndrome

We evaluated P wave dispersion (Pwd), QT, corrected QT (QTc), QT dispersion, and corrected QT dispersion (QTcd) intervals in patients with metabolic syndrome (MetS). Patients scheduled to undergo elective noncardiac surgery were included in the study. The main diagnoses, anthropometric measurements, waist circumferences, body mass index, electrocardiograms, serum levels of electrolytes, glucose, and lipids were recorded for all patients. QTc, QTcd intervals were determined with the Bazett formula. MetS (group M, n = 36) was diagnosed using the Adult Treatment Panel III. Controls (group C, n = 40) were chosen on the basis of patients with no MetS and matched for age and gender. There were no differences between groups in terms of age, sex, or serum electrolyte levels (P > 0.05). Waist circumferences, body mass index, serum glucose, and triglyceride values in group M were significantly higher than those in group C (P < 0.001). In group M, Pwd, QTc, QT dispersion and QTcd intervals were significantly longer than those in group C (P < 0.001). This finding and our retrospective analysis suggest that these patients may be at greater risk of perioperative arrhythmias.

The variations of BOP gene in hypertrophic cardiomyopathy

The observation that Bop null allele mice show underdeveloped right ventricle and excessive development of left ventricle, suggests the possible relationship between human BOP gene and hypertrophic cardiomyopathy (HCMP). In our study, we investigated this possible relationship between BOP gene variations and QT dispersion, a noninvasive arrhythmic risk marker for HCMP. This cross-sectional study consisted of 50 patients clinically diagnosed with HCMP and 60 healthy subjects. Exonic regions of BOP gene were amplified by polymerase chain reaction and amplified exonic regions were analyzed by Single-Strand Conformation Polymorphisms (SSCP). The samples with different migration patterns were sequenced through an automated sequencing system. Continuous variables were compared by unpaired t-test for independent samples or Mann-Whitney U test. Genotype-disease relationship was tested by Chi-square test. The nucleotide substitutions G275<or=A and C965<or=A in exon 2 and 7 were determined only in HCMP group. The G707<or=C, C710<or=T, T761<or=C, T1217<or=C SNPs in exon 6 and 9 are also found in the control group. Significant differences were found between two groups (p=0.002 and p=0.001). It was found that SNPs in exon 6 constitute a haplotype and that QT dispersion and corrected QT dispersion in the rare homozygote (707C/710T/761C) type carriers of HCMP patients for this haplotype were significantly lower than other genotypes (p=0.032 and p=0.030, respectively). The human BOP gene was analyzed for the first time in HCMP to investigate possible association. The result that homozygosity of 707C/710T/761C haplotype is associated with lower QT dispersion and corrected QT dispersion supports the modifier role of BOP gene in HCMP.

Anterior Mitral Valve Length is Associated with Ventricular Tachycardia in Patients with Classical Mitral Valve Prolapse

The aim of this study was to investigate the electrocardiographic and echocardiographic predictors of ventricular tachycardia (VT) in patients with classical mitral valve prolapse (MVP). Thirty patients (nine men and 21 women; mean age, 41.5 ± 15 years) in sinus rhythm with mitral valve prolapse who had VT in 24-hour Holter analysis and 30 patients with MVP without VT (eight men and 22 women; mean age, 43 ± 16 years) were included in this study. Transthoracic echocardiography, QT analyses from 12-lead electrocardiography, and 24-hour Holter electrocardiogram recordings were performed. Mitral posterior leaflet thickness (0.48 ± 0.03 cm vs 0.43 ± 0,08 cm, P = 0.025), mitral anterior leaflet length (3.2 ± 0.24 cm vs 2.9 ± 0.36, P < 0.001), mitral posterior leaflet length (2.2 ± 0.3 cm vs 1.9 ± 0.35 cm, P = 0.01), left atrium anteroposterior diameter (4.2 ± 0.8 cm vs 3.5 ± 0.5 cm, P = 0.001), and mitral annulus circumference (15.7 ± 1.3 cm vs 14.6 ± 1.6 cm, P = 0.004) were increased significantly in MVP cases with VT. No significant difference was found between the cases with and without VT in terms of frequency- and time-domain analysis. QT dispersion (72 ± 18 ms vs 55 ± 15 ms, P = 0.0002) and corrected QT dispersion (QTcD) (76 ± 18 ms vs 55 ± 15 ms, P = 0.0002) were significantly increased in cases with VT compared with those without VT. Based on logistic regression analysis for MVP cases, in the case of VT, an enhancement in QTcD (P = 0.01) and the mitral anterior leaflet length (P = 0.003) were the independent predictors of VT. Mitral anterior leaflet length and enhanced QTcD are closely related with VT in patients with classical MVP.

Impact of systemic sclerosis on electromechanical characteristics of the heart

Primary myocardial involvement is common in systemic sclerosis (SSc). We evaluated the atrial and ventricular electromechanical characteristics by using tissue Doppler echocardiography in SSc patients with subclinical cardiac involvement. Twenty-seven consecutive patients (24 women; mean age +/- SD 49.9 +/- 11.3 years) presenting with SSc without pulmonary arterial hypertension or symptomatic heart failure were prospectively studied. Electrocardiographic P-wave dispersion (Pd), corrected QT dispersion (QTcd), interatrial, intra-atrial, interventricular, and intraventricular electromechanical delays were analyzed by tissue Doppler echocardiography, and brain natriuretic peptide levels were measured. Results were compared with 17 healthy controls. There was no difference in conventional and tissue Doppler parameters between the two groups. However, patients with SSc had higher mean Pd (mean [+/-SD] 46.8 +/- 15 and 36 +/- 8 ms, respectively, P = 0.004) and mean interatrial electromechanical delay time (DT) (mean [+/-SD] 32.2 +/- 9.2 and 24.7 +/- 9.7 ms, respectively, P = 0.01), mean electromechanical delay time for all segments (Mean Ts) (mean [+/-SD] 148.8 +/- 18.8 and 129.3 +/- 13.4 ms, respectively, P < 0.001), and intraventricular DT (mean [+/-SD] 27.6 +/- 12.5 and 16.2 +/- 7.2 ms, respectively, P < 0.001). Intraventricular DT was the only parameter that correlated significantly with the Mean Ts. Brain natriuretic peptide levels were within normal limits in both groups; however, they were higher in patients with SSc than in controls (mean [+/-SD] 37.5 +/- 28.5 and 23.1 +/- 16.0 pg/ml, respectively, P = 0.03). The evaluation of atrial and ventricular electromechanical parameters by using tissue Doppler echocardiography seems to be useful for detection of subclinical cardiac involvement in SSc patients with normal conventional echocardiographic findings.

An Evaluation of P Wave Dispersion, QT, Corrected QT and Corrected QT Dispersion Intervals on the Electrocardiograms of Malnourished Adults

The aim of our study was to investigate P wave dispersion (Pwd), QT corrected QT (QTc), QT dispersion (QTd) and corrected QT dispersion (QTcd) intervals in subjects with malnutrition diagnosed in the pre-anaesthetic assessment, compared to those without malnutrition. A total of 76 adult patients were included. Main diagnoses, anthropometric measurement, body mass index, electrocardiogram and serum sodium, potassium, chloride, magnesium and calcium levels were recorded for all patients. Pwd, QT and QTd intervals were measured on all electrocardiogram records and QTc and QTcd intervals determined with the Bazett formula. Protein-energy malnutrition was diagnosed with the nutritional risk index. No statistically significant difference was found between the age, gender and malignant cancer diagnosis rates between patients with malnutrition (group M) and those not suffering from malnutrition (group N) (P > 0.05). Serum albumin, total protein, potassium, calcium, magnesium and chloride values of group M were found to be significantly lower than group N (P < 0.05). In group M, Pwd, QT, QTc, QTd and QTcd intervals were significantly longer than in group N (P < 0.001). Patients diagnosed with malnutrition during pre-anaesthetic assessment had significantly longer Pwd, QTc and QTcd interval durations than the control group. We attribute such extended Pwd, QTc and QTcd durations in these patients to malnutrition and malnutrition-related electrolyte imbalance.

Evaluation of P Wave and Corrected QT Dispersion in Subarachnoid Haemorrhage

The aim of our study was to investigate P wave dispersion (Pwd), QT corrected QT (QTc), QT dispersion (QTd) and corrected QT dispersion (QTcd) intervals in subarachnoid haemorrhage. Thirty-five subarachnoid haemorrhage patients (Group S) and 35 neurologically normal patients (Group C) were included in this retrospective study. The standard 12 derivations of the electrocardiograms of all patients were analysed and Pwd, QT and QTd intervals were measured. QTc and QTcd intervals were determined with the Bazett formula. There was no significant difference between the study groups according to demographic characteristics, hypertension and diabetes mellutus incidences (P > 0.05). The Pwd, QT, QTc, QTd and QTcd durations of Group S were significantly longer than those of Group C (P < 0.001). Subarachnoid haemorrhage patients may have a higher likelihood of arrhythmia during anaesthesia and in intensive care due to extended QTcd and Pwd durations.

Corrected QT dispersion improves diagnostic performance of exercise testing in diagnosing coronary artery disease

To determine the best combination of parameters that would improve the diagnostic performance of exercise testing, coronary angiography plus exercise testing were done on 112 patients with angina pectoris and normal electrocardiogram. The univariate predictors of coronary artery disease included: age > or = 40 years, male sex, hypertension, smoking, development of exertional chest pain, decrease in systolic blood pressure (BP) > or = 10 mmHg or systolic BP 3 min post-exercise > 90% of peak, heart rate drop < 12 beats/min 1 min postexercise, exercise-induced ST-segment depression > or = 1 mm. Multivariate logistic regression analysis showed that using either ST depression > or = 1 mm or peak exercise QTDc > 70 ms significantly improved sensitivity and negative predictive value of the test without a significant decrease in specificity.

Early Detection of Subclinical Anthracycline Cardiotoxicity on the Basis of QT Dispersion

We examined whether dobutamine-stress QT dispersion (QTd) and heart-rate corrected QT dispersion (QTcd) are useful for detecting subclinical anthracycline cardiotoxicity. The subjects were 10 control subjects and 37 patients divided into 4 groups according to cumulative anthracycline dose: non-anthracycline group (group N), 7 patients; low anthracycline cumulative dose group (group L), 8 patients (< 200 mg/m²); medium anthracycline cumulative dose group (group M), 16 patients (200 to < 400 mg/m²); and high cumulative group (group H), 6 patients (≥ 400 mg/m²). Standard 12-lead electrocardiograms were recorded. QTd and QTcd were measured and calculated at rest and after administration of dobutamine at 5 or 30 µg/kg/min. We also estimated cardiac function and cardiac reserve function at rest and after administration of dobutamine at a dose of 5 or 30 µg/kg/min. At rest, QTd and QTcd were significantly greater in groups M and H. After administration of dobutamine at 30 µg/kg/min, QTd and QTcd were significantly greater in groups L, M, and H. There was good correlation between QTd and the cumulative anthracycline dose; the correlation formula was y=0.051 x + 42.2 (r = 0.81, p < 0.001). The cumulative anthracycline dose of 152.9 mg/m², calculated from the correlation formula, was the cut-off for detection of electrophysiological cardiac abnormalities. Cardiac performance data at rest and dobutamine stress by echocardiography and pulsed Doppler echocardiography are less sensitive for detecting cardiac abnormalities than are QTd and QTcd. Dobutamine-stress QTd and QTcd are useful for detecting anthracycline cardiotoxicity and subclinical cardiac abnormality at low cumulative anthracycline doses. We must be aware of the possibility of subclinical myocardial abnormalities in patients with a cumulative anthracycline dose of ≥ 150 mg/m².

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

QT interval dispersion (QTD) is an independent predictor of outcome following acute neurological events. To explore QTD patterns and their relation to the affected cerebral region in patients with acute ischemic stroke. 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). 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). 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.

Acute Effects of Low Doses of Red Wine on Cardiac Conduction and Repolarization in Young Healthy Subjects

Moderate to high blood concentrations of ethanol have been shown to yield acute changes in cardiac electrophysiological properties, but the effect of low concentrations have never been assessed. The role of concomitant changes in clinical variables or cardiac dimensions is also still unknown. This study aimed at exploring the acute effects of low doses of ethanol, administered as Italian red wine, on conduction, depolarization, and repolarization electrocardiographic (ECG) intervals in a population of healthy subjects. Forty healthy young volunteers drank a low quantity of red wine (5 ml/kg), and an equal volume of fruit juice in separate experiments. Heart rate, P-wave duration, PR interval, QRS duration, QT interval, corrected QT interval, QT dispersion, and corrected QT dispersion were assessed at baseline and after 60 minutes from challenge. Mean blood ethanol concentration after drinking was 0.48 +/- 0.06 g/l. Compared to the control challenge, significant changes after red wine intake were observed in P-wave duration (from 101 +/- 11 to 108 +/- 14 milliseconds, p = 0.0006), PR interval (from 153 +/- 15 to 167 +/- 17 milliseconds, p < 0.0001), QT interval (from 346 +/- 28 to 361 +/- 24 milliseconds, p < 0.0001), and corrected QT interval (from 388 +/- 24 to 402 +/- 30 milliseconds, p = 0.0006). None of these changes showed correlations with modifications in clinical or echocardiographic variables. In multivariate analyses aimed at exploring predictors of ECG changes, none of the variables entered the final models. Low doses of red wine acutely slow cardiac conduction and prolong repolarization in normal individuals. These changes are poorly predictable. The potential arrhythmogenic impact of these effects is worthy of exploration.

QT Duration and Dispersion in Patients with Anomalous Origins of Coronary Arteries

Coronary artery anomalies have been reported to show various symptoms ranging from chest pain and dyspnea to cardio-respiratory arrest and sudden death. In this study, we attempted to assess the changes in QT interval duration and dispersion in anomalous origins of coronary arteries (AOCA). Nineteen AOCA patients (mean age: 52 +/- 11 years) and 30 healthy control subjects (mean age: 50 +/- 12 years) were included in the study. Minimum and maximum corrected QT intervals, and corrected QT dispersion were calculated. The two groups were compared in terms of QT dispersion and QT duration. There was no difference between the two groups in terms of baseline demographic characteristics. Maximum corrected QT intervals (QTc max), minimum corrected QT intervals (QTc min), and corrected QT dispersion were higher in AOCA patients than controls (452 +/- 38 vs 411 +/- 25 ms [P = 0.0001], 402 +/- 31 vs 383 +/- 28 ms [P = 0.048], and 51 +/- 30 vs 28 +/- 12 ms [P = 0.001], respectively). In the patients with anomalous origins of coronary arteries, QT dispersion that is an indicator of sudden cardiac death and arrhythmias frequency increased. QTc max, QTc min, and corrected QT dispersion are higher in patients with anomalous origin of the coronary artery than in control subjects.

QT Dispersion and Sleep related Breathing Disorders in Recipients of Implantable Cardioverter Defibrillator

The aim was to investigate a high risk group of patients with an implantable cardioverter defibrillator (ICD) and to evaluate the relation of QT dispersion and sleep related breathing disorders (SRBD). The study population consisted of 44 unselected ICD recipients. The patients were divided in two groups: group I consisted of 29 pts without or only with mild SRBD, group II – 15 pts with at least moderate SBBD. The groups did not differ according to the age, sex, ejection fraction and use of beta-blocking agents or amiodarone. QT dispersion (QTD) did not differ between the groups: 63.4 + 17.9 ms in group I and 60.3 + 25.7 ms in group II, p=0.64. Heart rate corrected QT dispersion (QTcD) did not differ between the groups as well (66.7 + 19.5 ms in group I and 67.6 + 30.4 ms in group II, p=0.91). Spearman correlation analysis between the QTD, QTcD and Apnea-Hypopnea Index did not show any significant correlations in this contingent. Ill. 2, bibl. 15 (in English; summaries in English, Russian and Lithuanian).

Effect of different intra-abdominal pressure levels on QT dispersion in patients undergoing laparoscopic cholecystectomy

Hemodynamic changes caused by carbon dioxide (CO(2)) insufflation occur frequently in patients who undergo laparoscopic surgery. One indicator of these changes is corrected QT dispersion (QTcd), an index of myocardial function. Prolongation of QTcd has been associated with cardiovascular morbidity and mortality. We compared the effects of high-pressure (15 mmHg) and low-pressure (7 mmHg) CO(2) pneumoperitoneums on the QT interval, the rate-corrected QT interval (QTc), the QT dispersion (QTd), and the corrected QT dispersion (QTcd) during laparoscopic cholecystectomy. Twenty consecutive patients were in a low-pressure pneumoperitoneum group and 32 were in a high-pressure pneumoperitoneum group. A 12-lead electrocardiogram was used to monitor cardiac variables. In all patients, serial electrocardiograms were recorded before anesthesia induction (baseline), immediately after the pneumoperitoneum had been created, every 15 minutes during CO(2) insufflation, and 5 minutes after deflation. Two observers measured the QT intervals independently, and the QTcd was calculated using Bazett's formula. The QT interval and the QTc interval did not change significantly during the study in either group. The QTd and QTcd in the high-pressure pneumoperitoneum group increased significantly during CO(2) insufflation and were significantly higher in the high-pressure pneumoperitoneum group compared with the low-pressure pneumoperitoneum group. Changes caused by CO(2) insufflation were reversible. Statistically significant increases of QTd and QTcd, which are associated with an increased risk of arrhythmias and cardiac events, occur during CO(2) insufflation in both high-pressure and low-pressure pneumoperitoneums. QTd and QTcd were significantly higher in the high-pressure pneumoperitoneum group than they were in the low-pressure pneumoperitoneum group. QT interval changes were not related to anesthetic agents, surgical stress, hypercapnia, or duration of CO(2) insufflation. Increased intra-abdominal pressure may have caused these changes.

A comparison of the effects of desflurane, sevoflurane and propofol on QT, QTc, and P dispersion on ECG

The aim of this prospective, randomized, and double-blinded study was to compare the effects of desflurane, sevoflurane, propofol on both atrial and ventricular wall function by measurement of QT dispersion (QTd), corrected QT dispersion (QTcd), and P dispersion (Pd) on electrocardiogram (ECG). Forty-six patients from the American Society of Anesthesiologists class I-II undergoing noncardiac surgery, were enrolled in this study. Patients were randomly allocated to receive desflurane, sevoflurane or propofol anesthesia. ECG recordings were taken before and after 5 minutes of drug administration. Induction with desflurane significantly increased the QTd compared to baseline (38 +/- 2 ms vs. 62 +/- 6 ms, P 0.05). Sevoflurane and propofol anesthesia was not associated with any changes in QTd. QTcd was increased with desflurane induction and decreased with sevoflurane and propofol induction, but this decrease was only significant in the propofol group (67 +/- 5 ms vs. 45 +/- 3 ms, P 0.05). Pd was significantly increased after induction with desflurane (34 +/- 3 vs. 63 +/- 6 ms, P 0.05). There was a significant increase in QTd and Pd in desflurane group, but this increment did not cause any dangerous arrhythmias. QTcd significantly decreased in propofol group. We believe that further investigations are required for using desflurane as safe as sevoflurane and propofol in noncardiac surgery patients who have high cardiac arrhythmia and ischemia risk.

Effect of remifentanil on QT dispersion.

QT dispersion (QT(d)) is an indirect measure of the heterogeneity of ventricular repolarization and can be used as a risk factor for complex ventricular arrhythmias. We measured the effect of remifentanil on QT(d) and heart-rate corrected QT dispersion (QT(cd)). Sixty ASA class I and II patients, who were between 20 and 60 years old, and who were scheduled for general anesthesia, were studied. After the patient entered the operating room, a 12 lead EKG recording was taken and intravenous infusion of remifentanil was started. The infusion rate was 0.1 microg/kg/min in group 1 and 0.2 microgram/kg/min in group 2. Another EKG recording was taken 10 minutes after infusion had started. In both groups, QT(d) following remifentanil infusion was not significantly different than control values (76.6 +/- 23.3 ms vs 81.8 +/- 34.9 ms, P = 0.459 in group 1; 70.7 ms +/- 29.7 ms vs 73.7 ms +/- 37.1 ms, P = 0.734 in group 2). Neither was QT(cd): (83.2 ms +/- 25.2 ms vs 89.6 ms +/- 36.2 ms, P = 0.371 in group 1; 81.0 ms +/- 35.2 ms vs 83.4 ms +/- 40.9 ms, P = 0.829 in group 2). Remifentanil infusion at a rate less than 0.2 microg/kg/min does not change QT(d) or QT(cd).

Statin therapy shortens QTc, QTcd, and improves cardiac function in patients with chronic heart failure

Although some data suggest that statins can improve cardiac mechanical function in some patients with chronic heart failure (CHF), the effects of long-term statin therapy on cardiac electrical instability remain unclear. We performed a randomized perspective analysis of the effects of 10 mg/d (statin group 1, n = 40), 20 mg/d (statin group 2, n = 38) of atorvastatin and controls (control group, n = 41) on corrected QT intervals (QTc), corrected QT dispersion (QTcd) and cardiac function in patients with CHF secondary to coronary artery disease (CAD) for one year. At 6 and 12 months, the statin groups displayed lower QTc and QTcd compared with controls. The changes were becoming more distinct in statin group 2, ( P < 0.05). In statin groups, the changes of QTc and QTcd were independent of changes of plasma low-density lipoprotein cholesterol and total cholesterol levels, and the decrease of QTcd was correlated with the increase of LVEF within 12 months. Atorvastatin shortens QTc, QTcd and improves cardiac function, and might thereby be parts of the mechanisms which atorvastatin benefited CHF patients secondary to CAD.

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

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

Acute Sleep Deprivation is Associated with Increased QT Dispersion in Healthy Young Adults

Sleep deprivation (SD) is known to be associated with worse cardiovascular outcome including mortality. We investigated the association between acute SD and electrocardiographic maximum QT interval (QTmax), QT, and corrected QT dispersion (QTd/cQTd), which are known to be among predictors of ventricular arrhythmias and sudden death. We obtained electrocardiograms of 37 healthy young volunteers (age: 28.45 +/- 7.97 years; 11 women) after a night with regular sleep and repeated after a night with sleep debt. We measured minimum QT interval (QTmin), QTmax, QTd, and cQTd in milliseconds. Average sleep time of the subjects were 7.7 +/- 0.8 hours during regular sleep and 1.7 +/- 1.6 hours during a night with sleep debt (P < 0.001). Subjects had similar values of QTmin in milliseconds after a night of sleep debt when compared to after regular sleep (347.56 +/- 29.75 vs 344.59 +/- 20.89; P = 0.51), whereas they had significantly higher values of QTmax, QTd, and cQTd (396.48 +/- 30.11 vs 378.10 +/- 23.90; P = 0.001, 49.45 +/- 9.11 vs 33.51 +/- 10.05; P < 0.001 and 54.92 +/- 10.42 vs 37.23 +/- 10.81; P < 0.001, respectively). In Pearson's correlation analysis, QTmax, QTd, and cQTd were inversely correlated with sleep time (P = 0.012, r =-0.291; P < 0.001, r =-0.625 and P < 0.001, r =-0.616, respectively) In conclusion, we clearly demonstrated that even one night of SD is associated with significant increase in QTmax, QTd, and cQTd in healthy young adults despite remaining within normal limits. These electrocardiographic changes in acute SD might contribute to development and/or recurrence of arrhythmias. This implication deserves further studies for clarifying the possible linkage between SD and arrhythmias.

The Effect of Altitude on P‐Wave and QT Duration and Dispersion

Short-term and long-term exposure to high altitude has been reported to change the surface electrocardiogram. We aimed to compare P-wave and QT parameters between healthy people living at high altitude and sea level. Twelve-lead electrocardiographies of 38 healthy people living at sea level (Antalya,Turkey) and 38 healthy people living at high altitude (Van, Turkey; 1,700-1,800 m) were obtained. Minimum and maximum P-wave durations, P-wave dispersion, minimum and maximum corrected QT intervals, and corrected QT dispersion were calculated. There was no significant difference between the two groups in respect to heart rate and QT variables. Mean Pminimum values were slightly but significantly lower in the high altitude group (P = 0.029). Mean Pmaximum values tended to be lower at high altitude but did not reach statistical significance (P = 0.085). However, there was no significant difference in respect to P-wave dispersion values. In a sample of men and women living at high altitude in Turkey, significant reduction of Pminimum and borderline reduction of Pmaximum duration, but no significant change of P-wave and QT dispersion, were observed.