scholarly journals The QT Interval Dynamic in a Human Experimental Model of Controlled Heart Rate and QRS Widening

2019 ◽  
Vol 8 (9) ◽  
pp. 1417 ◽  
Author(s):  
Santiago Colunga ◽  
Remigio Padrón ◽  
Daniel García-Iglesias ◽  
José Manuel Rubín ◽  
Diego Pérez ◽  
...  
Keyword(s):  
Heart Rate ◽  
Qt Interval ◽  
Qt Prolongation ◽  
Frequency Range ◽  
Linear Effect ◽  
Qt Intervals ◽  
Pearson Coefficient ◽  
St Segment ◽  
Frequency Correction ◽  
Valve Implantation

Background: there is increasing interest for computing corrected QT intervals in patients with prolonged depolarization. We aimed to analyze the effect of prolonged QRS in the QT and in the diagnostic accuracy of frequency-correction. Methods and Results: in 28 patients admitted for self-expanding aortic valve implantation, sequential pacing was performed in the AAI mode in two different phases: before and immediately after the release of the prosthesis. We evaluated the accuracy of the Bazett, Fridericia, Framingham and Hodges formulas with the reference of the QT at 60 bpm (QTc/deviation). The widening of the QRS was the main contributor to the QT prolongation (Pearson 0.79; CI95%: 0.75–0.84). Prolongation in other intervals (ST segment and T-wave) significantly contribute in the higher frequency range (p < 0.05). The Bazett’s formula displayed the highest QTc/deviation, while Framingham and Hodges retrieved the lowest QTc/deviation and the best fit (p < 0.001). In addition, the Bazett’s formula displayed the highest correlation between variations in the QTc/deviation and the widening of the QRS (Pearson coefficient −0.54; p < 0.001) in comparison with the Fridericia, Framingham and Hodges formulas (−0.51, −0.37 and −0.38 respectively; p < 0.001). There was also a linear effect of the heart rate in the QTc/deviation obtained with the Bazett’s formula (p = 0.015), not observed for other formulas. Conclusions: The prolonged depolarization of the ventricles introduces direct and linear prolongation in the QT interval, but also a non-linear distortion in cardiac repolarization that contributes for QT prolongation at the higher frequency range. The Bazett’s formula displays significantly higher sensitivity to prolongation of ECG intervals.

Electrocardiographic characteristics and associated outcomes in patients with Takotsubo syndrome. Insights from the RETAKO registry

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
I Martin-Demiguel ◽  
I Nunez-Gil ◽  
A Perez-Castellanos ◽  
O Vedia ◽  
A Uribarri ◽  
...  
Keyword(s):  
Heart Rate ◽  
Primary Endpoint ◽  
Qt Interval ◽  
Protective Factor ◽  
Independent Predictor ◽  
Prognostic Significance ◽  
Takotsubo Syndrome ◽  
St Segment Elevation ◽  
Corrected Qt Interval ◽  
St Segment

Abstract Background Our aim was to describe the prevalence and prognostic significance of electrocardiographic features in patients with Takotsubo syndrome (TTS). Methods Our data come from the Spanish Multicenter REgistry of TAKOtsubo syndrome (RETAKO). All patients with complete electrocardiogram were included. Results 246 patients were studied, mean age was 71.3±11.5 and 215 (87.4%) were women. ST-segment elevation was seen in 143 patients (59.1%) and was present in ≥2 wall leads in 97 (39.8%). Exclusive elevation in inferior leads was infrequent (5 - 2.0%). After 48 hours, 198 patients (88.0%) developed negative T-waves in a median of 8 leads with a mean amplitude of 0.7±0.5 mV. Mean corrected QT interval was 520±72 ms and it was independently associated with the primary endpoint of all-cause death and nonfatal cardiovascular events (p=0.002) and all-cause death (p=0.008). A higher heart rate at admission was also an independent predictor of the primary endpoint (p=0.001) and of developing acute pulmonary edema (p=0.04). ST-segment elevation with reciprocal depression was an independent predictor of all-cause death (p=0.04). Absence of ST-segment deviation was a protective factor (p=0.005) for the primary endpoint. Arrhythmias were independently associated with cardiogenic shock (p&lt;0.001). Conclusion Prolonged corrected QT interval, arrhythmia, heart rate at admission and broader repolarization alterations are associated with a poor outcome in TTS. Typical ECG at admission and after 48h. Funding Acknowledgement Type of funding source: None

Abstract 14311: Qt Interval Correlation Between Telemetry and 12-lead Electrocardiogram

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Mohamed Farhan Nasser ◽  
Ahmad Jabri ◽  
Saima Karim ◽  
Elizabeth Kaufman
Keyword(s):  
Qt Interval ◽  
Ventricular Arrhythmias ◽  
Qt Prolongation ◽  
T Wave ◽  
Qt Intervals ◽  
Increased Risk ◽  
Tangent Method ◽  
Wave Morphology ◽  
Monitoring Service ◽  
Inpatient Units

Introduction: QT prolongation is associated with increased risk of ventricular arrhythmias.As many patients with COVID19 may be started on QT prolonging drugs, measuring and monitoring QT is imperative to prevent fatal ventricular arrhythmias. However, we need to limit exposure of staff to patients with confirmed COVID19 and judiciously use personal protective equipment. Thus, it is important to find alternatives to doing frequent 12-lead ECGs. Hypothesis: We hypothesize that the QT interval measured from telemetry is similar to the QT interval on 12-lead ECG. Methods: Telemetry recordings and 12-lead ECGs were obtained from 15 patients at the same time and identical heart rates. Patients were from two different inpatient units with the same telemetry monitoring service. QT intervals were measured manually using calipers with the tangent method, excluding U waves. Telemetry recordings included lead I and II or a precordial lead. QT from telemetry was compared to the corresponding leads and to the longest QT on the 12-lead ECG. In cases of atrial fibrillation (AF), the QT from all the complexes was averaged. Results: Of 15 patients, 2 were in AF and 2 had RBBB. One patient had abnormal T-wave morphology and QT prolongation (abnormal repolarization). In all patients, QT intervals from the same leads as telemetry matched the QT measured from 12-lead. In 14 of 15 patients, telemetry QT matched the longest QT on the 12-lead ECG. However, in the patient with abnormal repolarization, maximum QT on 12-lead ECG was substantially longer than telemetry QT (Figure 1). Conclusion: When using the same lead, QT intervals were identical on telemetry and 12-lead ECG. However, in the patient with abnormal repolarization, the longest QT on 12-lead ECG was not represented on telemetry. In patients with abnormal repolarization on 12-lead ECG, we recommend serial 12-lead ECGs while on QT-prolonging drugs. Telemetry may suffice as a surrogate for 12-lead ECG to follow QT intervals in most patients.

Prolongation of the QT interval in heart failure occurs at low but not at high heart rates

2000 ◽  
Vol 98 (5) ◽  
pp. 603-610 ◽  
Author(s):  
P. P. DAVEY ◽  
C. BARLOW ◽  
G. HART
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Left Ventricular Hypertrophy ◽  
Qt Interval ◽  
Ventricular Hypertrophy ◽  
Left Ventricular ◽  
Qt Interval Prolongation ◽  
Qt Intervals ◽  
Ventricular Structure ◽  
And Function

Abnormal left ventricular structure and function as in, for example, left ventricular hypertrophy or chronic heart failure, is associated with sudden cardiac death and, when the ejection fraction is depressed, with prolongation of the QT interval. The dependence on heart rate of QT interval prolongation in these conditions, and the relationship of any abnormalities either to deranged autonomic nervous system function or to an adverse prognosis, has not been well studied. We therefore investigated (1) the dependence on heart rate of the QT interval, and (2) the relationship between both QT interval and the QT/heart rate slope and markers of adverse prognosis in these two conditions. The QT interval was measured at rest and during exercise in 34 subjects with heart failure, 16 subjects with left ventricular hypertrophy and 16 age-matched controls with normal left ventricular structure and function. QTc (corrected QT) intervals at rest were significantly longer in heart failure patients (471±10 ms) than in controls (421±6 ms) or in subjects with hypertrophy (420±6 ms) (P < 0.05). At peak exercise, despite the attainment of similar heart rates, the QT intervals no longer differed from each other, being 281±7 ms for controls, 296±11 ms in hypertrophy and 303±10 ms in heart failure (no significant difference). The QT/heart rate slope was significantly increased in heart failure [2.3±0.1 ms·(beats/min)-1] compared with controls [1.55±0.06 ms·(beats/min)-1] and hypertrophy [1.66±0.1 ms·(beats/min)-1] (P < 0.001). In left ventricular hypertrophy, despite animal data suggesting that QT interval prolongation should occur, no abnormalities were found in QT intervals at rest or during exercise. The QT/heart rate slope did not relate to any markers for an adverse prognosis, except that of prolongation of QT interval. Long QT intervals were associated principally with impairment of left ventricular systolic function. Our data emphasize the dynamic nature of the QT interval abnormalities found in heart failure.

scholarly journals Electrocardiographic evaluation of two anesthetic combinations in dogs

2000 ◽  
Vol 52 (2) ◽  
pp. 138-143 ◽  
Author(s):  
K.M. Tárraga ◽  
H.S. Spinosa ◽  
A.A. Camacho
Keyword(s):  
Heart Rate ◽  
Cardiac Rhythm ◽  
T Wave ◽  
Qt Intervals ◽  
St Segment ◽  
Electrocardiographic Changes ◽  
Group 2 ◽  
Group 1

This study aimed to investigate electrocardiographic changes in dogs aged 5 years or more submitted to two anesthetic combinations: atropine, levomeprazine, thiopental and halothane (ALTH), and atropine, tiletamine and zolazepam (ATZ). Forty dogs (24 males/16 females) weighing 5-24kg, were used. Dogs had no cardiac problems and were submitted to tartarectomy. All animals were submitted to two electrocardiograms (ECG), one before anesthesia and other immediately before surgery. The dogs were divided into two groups: group 1 received ALTH and group 2 received ATZ. Alterations in the ST segment, T wave, cardiac rhythm and a significant reduction of vagal tonus index were observed in both groups, but in group 2 a significant reduction of the PR and QT intervals and an increase in heart rate were also observed. These data suggest that the ALTH combination caused fewer changes in the ECG than the ATZ combination.

scholarly journals QT Prolongation in Cancer Patients

2021 ◽  
Vol 8 ◽  
Author(s):  
Peter Kim ◽  
Luke Masha ◽  
Amanda Olson ◽  
Cezar Iliescu ◽  
Kaveh Karimzad ◽  
...  
Keyword(s):  
Heart Rate ◽  
Stem Cell ◽  
Cancer Patients ◽  
Qt Interval ◽  
Large Population ◽  
Qt Prolongation ◽  
Inpatient Setting ◽  
Prescription Data ◽  
Causative Role ◽  
Normal Stem Cell

Background: QT prolongation and torsades de pointes pose a major concern for cardiologists and oncologists. Although cancer patients are suspected to have prolonged QT intervals, this has not been investigated in a large population. The purpose of this study was to analyze the QT interval distribution in a cancer population and compare it to a non-cancer population in the same institution.Methods: The study was a retrospective review of 82,410 ECGs performed in cancer patients (51.8% women and 48.2% men) and 775 ECGs performed in normal stem cell donors (47.9% women and 52.1% men) from January 2009 to December 2013 at the University of Texas MD Anderson Cancer Center. Pharmacy prescription data was also collected and analyzed during the same time period. Correction of the QT interval for the heart rate was performed using the Bazett and Fridericia formulas.Results: After QT correction for heart rate by the Fridericia formula (QTcF), the mean and 99% percentile QTc for cancer patients were 414 and 473 ms, respectively. These were significantly longer than the normal stem cell donors, 407 and 458 ms, p &lt; 0.001, respectively. Among the cancer patients, the QTc was longer in the inpatient setting when compared to both outpatient and emergency center areas. The most commonly prescribed QT prolonging medications identified were ondansetron and methadone.Conclusion: Our study demonstrates significantly longer QTc intervals in cancer patients, especially in the inpatient setting. Frequently prescribed QT prolonging medications such as antiemetics and analgesics may have a causative role in QT prolongation seen in our cancer hospital.

QT-Zeit – Was fange ich eigentlich damit an?

2020 ◽  
Vol 145 (08) ◽  
pp. 536-542
Author(s):  
Alessandro Castiglione ◽  
Katja Odening
Keyword(s):  
Heart Rate ◽  
Qt Interval ◽  
Beta Blockers ◽  
Clinical History ◽  
Interval Methods ◽  
Qt Intervals ◽  
Surface Ecg ◽  
Tangent Method ◽  
Clinical Consequences ◽  
Genetically Determined

AbstractThe assessment of the QT interval has been an integral part of ECG interpretation since the first descriptions of long QT syndrome by Wolff in 1950 and by Jervell and Lange-Nielsen in 1957. The correct measurement of the QT interval as well as a correct interpretation of the causes and of the clinical consequences of a QT prolongation, however, may be difficult even for trained internists and cardiologists. In this review, we give an overview on physiological determinants of cardiac repolarization, its marker in the surface ECG – the QT interval –, methods to correctly assess QT interval duration, causes for pathologically prolonged QT intervals, and resulting clinical consequences. A correct measurement of the QT interval should be performed by using the „tangent method“, excluding possible U waves. A heart rate correction formula should be employed to determine the heart rate corrected QT interval (QTc).Many factors, which may prolong the QT interval, should be checked whenever a QTc prolongation is observed. These include drugs, electrolyte imbalances, hormonal influence, and comorbidities. The correct management of a patient with (genetically determined) LQTS starts with a risk stratification based on genotype, ECG phenotype, clinical history, age, sex, concomitant diseases, drug therapies, and family history for syncope or sudden cardiac death. The therapeutic approaches for LQTS are multimodal. Prevention is the basis of the therapy and includes avoiding known risk factors / and potentially QT-prolonging drugs, and a pharmacological treatment with non-selective beta blockers. According to the risk profile and to the patient’s lifestyle the implantation of an ICD or a pacemaker should be considered.

Abstract P391: The Effects of Obstructive Sleep Apnea on Cardiac Arrhythmia Risk

Circulation ◽  
2020 ◽  
Vol 141 (Suppl_1) ◽  
Author(s):  
Emily Biben ◽  
Lauren Burgess ◽  
Julie Allen ◽  
Noah Jouett ◽  
John Burk ◽  
...  
Keyword(s):  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
Cardiac Disease ◽  
Qt Interval ◽  
The United States ◽  
Qt Prolongation ◽  
Qtc Interval ◽  
Sleep Study ◽  
Qt Intervals ◽  
Obstructive Sleep

Background: Over 20 million people in the United States suffer from Obstructive Sleep Apnea (OSA). Compared to the general population, OSA patients are 2.6 times more likely to experience sudden cardiac death (SCD), and it is suspected that this is due, in part, to QT prolongation leading to fatal dysrhythmias. OSA events have previously been shown to cause prolonged QT intervals compared to the post-apnea hyperventilation period, and studies have also observed increased QT dispersion in patients without cardiac disease. However, those with cardiac disease may be at the greatest risk for SCD, and it is not known what role QT prolongation plays and what factors influence these responses. Thus, the purpose of this study is to evaluate the factors that affect QT interval during periods of sleep apnea including OSA severity, time of night, and quantity of obstructive apneic events during sleep. Methods: We determined QTc intervals from the electrocardiograms of 36 patients undergoing polysomnography for diagnosis of OSA. Patients that were selected had an apnea hypopnea index >20/Hr and had no prior myocardial infarction or heart failure. Each patient’s ECG during their sleep study was analyzed to assess QT interval throughout the night. Baseline QT intervals were compared to QT intervals during obstructive apneas during the first 2 hours of sleep (Early) and last 2 hours of sleep (Late). In addition, apneas >40 seconds were analyzed in 11 patients for changes in QTc as the apnea progressed. Statistical comparisons were made with paired t tests and a one-way ANOVA analysis with repeated measures. Results: Early analyses of data showed QTc intervals in Early and Late apneas were significantly prolonged compared to awake baseline (p=0.04 and p=0.006 respectively). For patients with apneas >40 seconds, significant differences in QTc interval were observed at increasing time points during the apnea compared to the QTc immediately preceding the apnea (p<0.001). Furthermore, patients with longer apneas tend to have longer baseline QTc (p=0.07). Conclusions: Sleep apneic events are associated with periods of mild QTc prolongation despite some cardiac cycle shortening. The prolongation tends to become enhanced later in the night, implying that there is a cumulative effect of numerous prior apneas. Furthermore, prolongation tends to increase as the apnea duration progresses. Early data analyses also suggest that baseline QTc tends to be longer in patients who have more severe/longer apneic events throughout the night. Future studies will focus on QTc changes in OSA patients with prior heart disease, as these are the patients at greatest risk for serious arrhythmias during the night.

scholarly journals Problems with Bazett QTc correction in paediatric screening of prolonged QTc interval

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Irena Andršová ◽  
Katerina Hnatkova ◽  
Kateřina Helánová ◽  
Martina Šišáková ◽  
Tomáš Novotný ◽  
...  
Keyword(s):  
Heart Rate ◽  
Supine Position ◽  
Qt Interval ◽  
Qtc Interval ◽  
Healthy Children ◽  
Long Qt ◽  
Normal Children ◽  
Heart Rates ◽  
Qt Intervals ◽  
Qt Syndrome

Abstract Background Bazett formula is frequently used in paediatric screening for the long QT syndrome (LQTS) and proposals exist that using standing rather than supine electrocardiograms (ECG) improves the sensitivity of LQTS diagnosis. Nevertheless, compared to adults, children have higher heart rates (especially during postural provocations) and Bazett correction is also known to lead to artificially prolonged QTc values at increased heart rates. This study assessed the incidence of erroneously increased QTc values in normal children without QT abnormalities. Methods Continuous 12-lead ECGs were recorded in 332 healthy children (166 girls) aged 10.7 ± 2.6 years while they performed postural manoeuvring consisting of episodes (in the following order) of supine, sitting, standing, supine, standing, sitting, and supine positions, each lasting 10 min. Detailed analyses of QT/RR profiles confirmed the absence of prolonged individually corrected QTc interval in each child. Heart rate and QT intervals were measured in 10-s ECG segments and in each segment, QTc intervals were obtained using Bazett, Fridericia, and Framingham formulas. In each child, the heart rates and QTc values obtained during supine, sitting and standing positions were averaged. QTc durations by the three formulas were classified to < 440 ms, 440–460 ms, 460–480 ms, and > 480 ms. Results At supine position, averaged heart rate was 77.5 ± 10.5 beat per minute (bpm) and Bazett, Fridericia and Framingham QTc intervals were 425.3 ± 15.8, 407.8 ± 13.9, and 408.2 ± 13.1 ms, respectively. At sitting and standing, averaged heart rate increased to 90.9 ± 10.1 and 100.9 ± 10.5 bpm, respectively. While Fridericia and Framingham formulas showed only minimal QTc changes, Bazett correction led to QTc increases to 435 ± 15.1 and 444.9 ± 15.9 ms at sitting and standing, respectively. At sitting, Bazett correction identified 51, 4, and 0 children as having the QTc intervals 440–460, 460–480, and > 480 ms, respectively. At sitting, these numbers increased to 118, 11, and 1, while on standing these numbers were 151, 45, and 5, respectively. Irrespective of the postural position, Fridericia and Framingham formulas identified only a small number (< 7) of children with QT interval between 440 and 460 ms and no children with longer QTc. Conclusion During screening for LQTS in children, the use of Bazett formula leads to a high number of false positive cases especially if the heart rates are increased (e.g. by postural manoeuvring). The use of Fridericia formula can be recommended to replace the Bazett correction not only for adult but also for paediatric ECGs.

scholarly journals Response of the QT interval to mental and physical stress in types LQT1 and LQT2 of the long QT syndrome

Heart ◽  
2001 ◽  
Vol 86 (1) ◽  
pp. 39-44
Author(s):  
K J Paavonen ◽  
H Swan ◽  
K Piippo ◽  
L Hokkanen ◽  
P Laitinen ◽  
...  
Keyword(s):  
Heart Rate ◽  
Serum Potassium ◽  
Long Qt Syndrome ◽  
Qt Interval ◽  
Mental Stress ◽  
Physical Stress ◽  
Exercise Stress ◽  
Long Qt ◽  
Qt Intervals ◽  
Qt Syndrome

OBJECTIVETo study and compare the effects of mental and physical stress on long QT syndrome (LQTS) patients.DESIGNCase–control study.MAIN OUTCOME MEASURESQT intervals were measured from lead V3. Serum potassium and plasma catecholamine concentrations were also monitored.PATIENTS16 patients with type 1 LQTS (LQT1), 14 with type 2 LQTS (LQT2), both groups asymptomatic, and 14 healthy control subjects.INTERVENTIONSThree types of mental stress tests and a submaximal exercise stress test.RESULTSHeart rate responses to mental stress and exercise were similar in all groups. During mental stress, the mean QT interval shortened to a similar extent in controls (–29 ms), LQT1 patients (–34 ms), and LQT2 patients (–30 ms). During exercise, the corresponding QT adaptation to exercise stress was more pronounced (p < 0.01) in healthy controls (–47 ms) than in LQT1 (–38 ms) or LQT2 patients (–38 ms). During exercise changes in serum potassium concentrations were correlated to changes in QT intervals in controls, but not in LQTS patients. LQT1 and LQT2 patients did not differ in serum potassium, catecholamine or heart rate responses to mental or physical stress.CONCLUSIONSQT adaptation to mental and exercise stress in healthy people and in patients with LQTS is different. In healthy people QT adaptation is more sensitive to physical than to mental stress while no such diverging pattern was seen in asymptomatic LQTS patients.

scholarly journals Evaluation of Tpeak–Tend and QT intervals in Chagas’ Disease, Chronic Phase and Normal Electrocardiogram

2020 ◽  
Vol 32 (4) ◽  
pp. 230-235
Author(s):  
Abilio Augusto Fragata Filho ◽  
Claudia da Silva Fragata ◽  
Angela Maria Lourenço ◽  
Cristiane Castro Faccini ◽  
João Ítalo Dias França
Keyword(s):  
Heart Rate ◽  
Chagas Disease ◽  
Qt Interval ◽  
Statistical Significance ◽  
Chronic Phase ◽  
Qtc Interval ◽  
Mean Values ◽  
Qt Intervals ◽  
Relationship Of ◽  
The Relationship

Introduction: Chagas’ disease lacks elements to predict which carriers will evolve into cardiac form and which will remain in undetermined form. Objective: To evaluate the relationship between electrocardiographic evolution and Tpeak–Tend and QT intervals, both corrected for heart rate, in chagasic patients with normal initial electrocardiogram. Method: Chagasic patients admitted to the institution until 2002 were retrospectively evaluated, and the electrocardiogram was normal at the first consultation. The Tpeak–Tend and QT intervals were measured in milliseconds at the V2 and V5 derivations, with the mean values corrected for heart rate (Bazett). The relationship of these values with the electrocardiographic evolution of the individuals was analyzed, considering the gender, time of evolution and whether they received benznidazole or not. Results: The corrected Tpeak–Tend interval showed no statistical significance among those who maintained or not normal electrocardiogram. The corrected QT interval, the treatment with benznidazole and the time of evolution showed significance for the maintenance of normal electrocardiogram. In the multivariate evaluation, treatment with benznidazole, the QTc interval and the time of evolution were independent variables for the maintenance of normal electrocardiogram. Conclusion: The Tpeak–Tend interval showed no predictor of electrocardiographic evolution. The increased QT interval favored changes.

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