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 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 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.

Effect of beta-blockers on the relation between QT-interval and heart rate in exercise ECG

1987 ◽  
Vol 8 (suppl D) ◽  
pp. 71-74 ◽  
Author(s):  
A. Algra ◽  
J. R. T. C. Roelandt ◽  
J. G. P. Tussen ◽  
M. L. Simoons ◽  
J. Pool
Keyword(s):  
Heart Rate ◽  
Qt Interval ◽  
Beta Blockers ◽  
Exercise Ecg

scholarly journals The association between body temperature and electrocardiographic parameters in normothermic healthy volunteers

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
G.J Hassing ◽  
B Fienieg ◽  
H.E.C Van Der Wall ◽  
G.J.P Van Westen ◽  
M.J.B Kemme ◽  
...  
Keyword(s):  
Heart Rate ◽  
Body Temperature ◽  
Healthy Volunteers ◽  
Qt Interval ◽  
Drug Induced ◽  
Mean Body Temperature ◽  
Corrected Qt Interval ◽  
Healthy Humans ◽  
Surface Ecg ◽  
Qrs Duration

Abstract Introduction Previous studies have observed that hypo- and hyperthermia are associated with several atrial and ventricular electrocardiographical parameters, including the corrected QT interval. Preclinical studies have shown that drugs that exert an effect on body temperature also exert an effect on the corrected QT interval. Therefore, increased characterization in healthy humans of the association between the corrected QT interval and body temperature within the normal body temperature range aids in understanding the mechanism behind drug induced corrected QT interval effects. The objective of this analysis was to evaluate the association between body temperature and electrocardiographical parameters in normothermic healthy volunteers. Methods Data from 3023 volunteers collected at our center were analyzed. Only subjects considered healthy after review of collected data by a physician, including a normal tympanic body temperature (35.5–37.5 °C) and in sinus rhythm, were included in the analysis. Subjects were divided into body temperature quartiles for analysis and a linear multivariate model with body temperature as a continuous was performed. Another multivariate analysis was performed with only the QT subintervals as independent variables and body temperature as dependent variable. Results Mean age was 33.8±17.5 years and mean body temperature was 36.6±0.4 °C. Body temperature was independently associated with age (standardized coefficient (SC)=−0.252, P&lt;0.001), gender (SC=+0.208, P&lt;0.001), heart rate (SC=+0.230, P&lt;0.001), J-point elevation in lead V4 (SC=−0.118, P&lt;0.001), and Fridericia corrected QT interval (SC=−0.061, P=0.002). Atrial and AV nodal parameters were not independently associated with body temperature. The effects of temperature on the surface ECG are displayed in figure 1. QT subinterval analysis revealed that only QRS duration (SC=−0.121, P&lt;0.001) was independently associated with body temperature. Conclusion Body temperature in normothermic healthy volunteers was associated with heart rate, J-point amplitude in lead V4 and ventricular conductivity, primarily through a prolongation of the QRS duration. In contrast, atrial and AV nodal ECG parameters were not independently associated with body temperature. Funding Acknowledgement Type of funding source: None

Prevalence, Management, and Clinical Consequences of QT Interval Prolongation During Treatment With Arsenic Trioxide

2014 ◽  
Vol 32 (33) ◽  
pp. 3723-3728 ◽  
Author(s):  
Gail J. Roboz ◽  
Ellen K. Ritchie ◽  
Rebecca F. Carlin ◽  
Michael Samuel ◽  
Leanne Gale ◽  
...  
Keyword(s):  
Arsenic Trioxide ◽  
Qt Interval ◽  
Interval Prolongation ◽  
Cardiac Events ◽  
Electrocardiographic Monitoring ◽  
Qt Interval Prolongation ◽  
Qt Intervals ◽  
Clinical Consequences ◽  
Study Population ◽  
Clinically Significant

Purpose Arsenic trioxide (ATO) is a highly effective agent for the treatment of acute promyelocytic leukemia (APL). QT interval prolongation is common with ATO and can pose a barrier to effective administration. The objective of this study was to characterize the prevalence, management, and clinical consequences of QT prolongation in a large cohort of patients treated with ATO. Patients and Methods We analyzed 3,011 electrocardiograms from 113 patients with non-APL acute myeloid leukemia and myelodysplastic syndrome who were treated on a previously reported clinical trial. QT intervals were assessed using four different correction formulas, and data were correlated with clinical parameters and treatment with ATO. Results There were no clinically significant cardiac events in the study population. Of those receiving ATO therapy, 29 patients (26%) had rate-uncorrected QT values above 470 ms and 13 (12%) had values exceeding 500 ms. With the commonly used Bazett rate correction formula, 102 patients (90%) had QTc greater than 470 ms, including 74 (65%) above 500 ms. By using alternative rate correction formulas, only 24% to 32% of patients had rate-corrected QT intervals above 500 ms. Conclusion QT interval prolongation is common with ATO treatment, but clinically significant arrhythmias are rare and can be avoided with appropriate precautions. Use of the Bazett correction may result in unnecessary interruptions in ATO therapy, and alternative rate correction formulas should be considered for routine electrocardiographic monitoring.

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.

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