Relation between QT intervals and heart rates from 40 to 120 beats/min in rest electrocardiograms of men and a simple method to adjust QT interval values

Karjalainen, Jouko; Viitasalo, Matti; Mänttäri, Matti; Manninen, Vesa

doi:10.1016/0735-1097(94)90654-8

Cited by 248 publications

(173 citation statements)

References 14 publications

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“…The changes in TCRT were not associated with changes in the autonomic regulation of heart rate, sympatho-adrenal activation or changes in the potassium level, suggesting that hypoglycaemia as such also exerts an influence on cardiac repolarisation patterns by other In several previous studies [3][4][5][6][7][8][9], a prolonged QT c interval and an increased QT dispersion have been reported during hypoglycaemia. According to earlier studies [10], the most often used formula, i.e. Bazett's formula, usually overadjusts the QT interval at high heart rates and undercompensates at low heart rates.…”

Section: Discussionmentioning

confidence: 99%

“…The duration of the QT interval was measured manually from the paper traces from the beginning of the QRS complex to the clear-cut end of the T-wave obtained from lead V2, with the investigator unaware of the clinical data of the participants. The heart rate-adjusted QT intervals were calculated: (1) according to Bazett's formula (QT c ) [23]; (2), as the QT interval corrected for heart rate by Fridericia's cubic root formula (QT Fc ) [24]; and (3) as the QT interval corrected for heart rate by the nomogram method (QT Nc ) [10]. The QT interval was also measured in every lead of the surface ECG and QT dispersion was calculated using the difference between the maximum and minimum of the QT interval in any of the leads.…”

Section: Methodsmentioning

confidence: 99%

“…This may partly explain the proarrhythmic effects of hypoglycaemia. The assessment of changes in cardiac repolarisation by measurements of the QT interval or QT dispersion is subject to many methodological biases, such as inaccuracies of QT heart rate correction formulas and intersubject variability in the measurement of QT dispersion [10,11]. Therefore, novel repolarisation analyses have been developed to evaluate the characteristics of cardiac repolarisation with greater accuracy.…”

Section: Introductionmentioning

confidence: 99%

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Effects of controlled hypoglycaemia on cardiac repolarisation in patients with type 1 diabetes

et al. 2007

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Aims/hypothesis Nocturnal hypoglycaemia may contribute to sudden death in diabetic patients. However, it is not well known why hypoglycaemia makes these patients prone to death. Methods We assessed the effects of controlled hypoglycaemia on cardiac repolarisation using novel electrocardiographic descriptors of T-wave and QRS complex morphology in 16 type 1 diabetic patients and eight healthy counterparts. Several electrocardiographic variables characterising repolarisation were analysed from digitised 12-lead electrocardiograms during a euglycaemic and a hypoglycaemic clamp. Results Hypoglycaemia did not result in significant changes either in the QT interval corrected for heart rate by the nomogram method or in QT dispersion. However, the morphology of the T-wave changed significantly during hypoglycaemia. The T-wave amplitude and area in precordial leads decreased significantly in both groups (p<0.05 to p<0.001). The spatial QRS-T angle (total cosine R to T) (p<0.05) and the height and the width of the T-wave loop (p<0.05 and p<0.01, respectively) were also reduced in the diabetic patients. The changes in the repolarisation parameters did not exhibit any significant association with changes in catecholamine levels or in heart rate variability in either group. Conclusions/interpretation Hypoglycaemia results in distinct alterations in cardiac repolarisation, which may increase the vulnerability to arrhythmic events.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of controlled hypoglycaemia on cardiac repolarisation in patients with type 1 diabetes

et al. 2007

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Section: Acquired Long Qt Syndrome: Frequency Onset and Risk Factormentioning

confidence: 99%

Acquired Long QT Syndrome: Frequency, Onset, and Risk Factors in Intensive Care Patients

Kozik

Wung

2012

Critical Care Nurse

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Background Acquired long QT syndrome is a reversible condition that can lead to torsades de pointes and sudden cardiac death. Objective To determine the frequency, onset, frequency of medications, and risk factors for the syndrome in intensive care patients. Methods In a retrospective chart review of 88 subjects, hourly corrected QT intervals calculated by using the Bazett formula were collected. Acquired long QT syndrome was defined as a corrected QT of 500 milliseconds or longer or an increase in corrected QT of 60 milliseconds or greater from baseline level. Risk factors and medications administered were collected from patients’ medical records. Results The syndrome occurred in 46 patients (52%); mean time of onset was 7.4 hours (SD, 9.4) from time of admission. Among the 88 patients, 52 (59%) received a known QTc-prolonging medication. Among the 46 with the syndrome, 23 (50%) received a known QT-prolonging medication. No other risk factor studied was significantly predictive of the syndrome. Conclusions Acquired long QT syndrome occurs in patients not treated with a known QT-prolonging medication, indicating the importance of frequent QT monitoring of all intensive care patients.

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“…The adequacy of Bazett's formula has been questioned because some evidence exists that the formula overcorrects the QT interval at fast heart rates and undercorrects it at low heart rates. 108 In a recent report on the value of QT C in predicting coronary heart disease in 14 548 healthy men and women, only minor differences were seen in the risk stratification provided by 3 rate correction methods, with the Bazett correction providing slightly better separation. 109 This finding supports the continued use of the Bazett correction method in clinical practice.…”

Section: General Considerations In Qt Interval Monitoringmentioning

confidence: 99%

Practice Standards for ECG Monitoring in Hospital Settings: Executive Summary and Guide for Implementation

Drew

Funk

2006

Critical Care Nursing Clinics of North America

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Abstract-The goals of electrocardiographic (ECG) monitoring in hospital settings have expanded from simple heart rate and basic rhythm determination to the diagnosis of complex arrhythmias, myocardial ischemia, and prolonged QT interval. Whereas computerized arrhythmia analysis is automatic in cardiac monitoring systems, computerized ST-segment ischemia analysis is available only in newer-generation monitors, and computerized QT-interval monitoring is currently unavailable. Even in hospitals with ST-monitoring capability, ischemia monitoring is vastly underutilized by healthcare professionals. Moreover, because no computerized analysis is available for QT monitoring, healthcare professionals must determine when it is appropriate to manually measure QT intervals (eg, when a patient is started on a potentially proarrhythmic drug). The purpose of the present review is to provide 'best practices' for hospital ECG monitoring. Randomized clinical trials in this area are almost nonexistent; therefore, expert opinions are based upon clinical experience and related research in the field of electrocardiography. This consensus document encompasses all areas of hospital cardiac monitoring in both children and adults. The emphasis is on information clinicians need to know to monitor patients safely and effectively. Recommendations are made with regard to indications, timeframes, and strategies to improve the diagnostic accuracy of cardiac arrhythmia, ischemia, and QT-interval monitoring. Currently available ECG lead systems are described, and recommendations related to staffing, training, and methods to improve quality are provided. Key Words: AHA Scientific Statements Ⅲ pediatrics Ⅲ electrocardiography Ⅲ torsade de pointes Ⅲ myocardial infarction Ⅲ tachyarrhythmias Ⅲ ischemia Ⅲ antiarrhythmic agents Ⅲ long-QT syndrome S ince the introduction of electrocardiographic (ECG) monitoring in hospital units Ͼ40 years ago, 1 the goals of monitoring have expanded from simple tracking of heart rate and basic rhythm to the diagnosis of complex arrhythmias, the detection of myocardial ischemia, and the identification of a prolonged QT interval. During the same 4 decades, major improvements have occurred in cardiac monitoring systems, including computerized arrhythmia detection algorithms, STsegment/ischemia monitoring software, improved noisereduction strategies, multilead monitoring, and reduced lead sets for monitoring-derived 12-lead ECGs with a minimal number of electrodes. 2,3 Despite these advances in technology, the need for human oversight in the interpretation of ECG monitoring data is as important today as it was 40 years ago for the following reasons. First, cardiac monitor algorithms are intentionally set for high sensitivity at the expense of specificity. As a result, numerous false alarms occur that must be evaluated by healthcare professionals so that overtreatment of patients will not occur. Examples of overtreatment are reported in the The American Heart Association makes every effort to avoid any actual or potential co...

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Relation between QT intervals and heart rates from 40 to 120 beats/min in rest electrocardiograms of men and a simple method to adjust QT interval values

Abstract: The QT-RR relation over a wide range of heart rates does not permit the use of one simple adjustment equation. A nomogram providing, for every heart rate, the number of milliseconds that the QT interval must be corrected gives excellent adjustment.

Cited by 248 publications

References 14 publications

Effects of controlled hypoglycaemia on cardiac repolarisation in patients with type 1 diabetes

Effects of controlled hypoglycaemia on cardiac repolarisation in patients with type 1 diabetes

Acquired Long QT Syndrome: Frequency, Onset, and Risk Factors in Intensive Care Patients

Practice Standards for ECG Monitoring in Hospital Settings: Executive Summary and Guide for Implementation

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