Accurate electrocardiographic assessment of the QT interval: Teach the tangent

Postema, Pieter G.; Jong, Jonas S.S.G. de; Bilt, Ivo A.C. van der; Wilde, Arthur A.M.

doi:10.1016/j.hrthm.2008.03.037

Cited by 269 publications

(174 citation statements)

References 8 publications

Supporting

Mentioning

168

Contrasting

Unclassified

Order By: Relevance

“…The end of the T wave was determined as the intersection point between the isoelectric baseline and the tangent line representing the maximal downward slope of the positive T wave or maximal upward slope of the negative T wave. 28,29 The QT interval was considered the longest interval of all 12 leads, generally occurring in leads II and V 5 . The mean of 3 consecutive QT intervals was used.…”

Section: Ecg Analysismentioning

confidence: 99%

Derivation and Validation of a Simple Exercise-Based Algorithm for Prediction of Genetic Testing in Relatives of LQTS Probands

et al. 2011

View full text Add to dashboard Cite

Background-Genetic testing can diagnose long-QT syndrome (LQTS) in asymptomatic relatives of patients with an identified mutation; however, it is costly and subject to availability. The accuracy of a simple algorithm that incorporates resting and exercise ECG parameters for screening LQTS in asymptomatic relatives was evaluated, with genetic testing as the gold standard. Methods and Results-Asymptomatic first-degree relatives of genetically characterized probands were recruited from 5 centers.QT intervals were measured at rest, during exercise, and during recovery. Receiver operating characteristics were used to establish optimal cutoffs. An algorithm for identifying LQTS carriers was developed in a derivation cohort and validated in an independent cohort. The derivation cohort consisted of 69 relatives (28 with LQT1, 20 with LQT2, and 21 noncarriers).Mean age was 35Ϯ18 years, and resting corrected QT interval (QTc) was 466Ϯ39 ms. Abnormal resting QTc (females Ն480 ms; males Ն470 ms) was 100% specific for gene carrier status, but was observed in only 48% of patients; however, mutations were observed in 68% and 42% of patients with a borderline or normal resting QTc, respectively. Among these patients, 4-minute recovery QTc Ն445 ms correctly restratified 22 of 25 patients as having LQTS and 19 of 21 patients as being noncarriers. The combination of resting and 4-minute recovery QTc in a screening algorithm yielded a sensitivity of 0.94 and specificity of 0.90 for detecting LQTS carriers. When applied to the validation cohort (nϭ152; 58 with LQT1, 61 with LQT2, and 33 noncarriers; QTcϭ443Ϯ47 ms), sensitivity was 0.92 and specificity was 0.82. Conclusions-A simple algorithm that incorporates resting and exercise-recovery QTc is useful in identifying LQTS in asymptomatic relatives. (Circulation. 2011;124:2187-2194.)

show abstract

Section: Ecg Analysismentioning

confidence: 99%

Derivation and Validation of a Simple Exercise-Based Algorithm for Prediction of Genetic Testing in Relatives of LQTS Probands

et al. 2011

View full text Add to dashboard Cite

show abstract

“…13 Blinded ECG analysis was performed manually. The QT interval was defined as the interval between the onset of the QRS complex and the intersection between the isoelectric baseline and a line tangential with the maximal slope of the terminal component of the T wave, 22 averaged over 3 measurements. The lead with the longest QT interval was used for analysis.…”

Section: Exercise Protocol and Ecg Analysismentioning

confidence: 99%

Characterization of Myocardial Repolarization Reserve in Adolescent Females With Anorexia Nervosa

et al. 2016

View full text Add to dashboard Cite

Background-Patients with anorexia nervosa exhibit abnormal myocardial repolarization and are susceptible to sudden cardiac death. Exercise testing is useful in unmasking QT prolongation in disorders associated with abnormal repolarization. We characterized QT adaptation during exercise in anorexia. Methods and Results-Sixty-one adolescent female patients with anorexia nervosa and 45 age-and sex-matched healthy volunteers performed symptom-limited cycle ergometry during 12-lead ECG monitoring. Changes in the QT interval during exercise were measured, and QT/RR-interval slopes were determined by using mixed-effects regression modeling. Patients had significantly lower body mass index than controls; however, resting heart rates and QT/QTc intervals were similar at baseline. Patients had shorter exercise times (13.7±4.5 versus 20.6±4.5 minutes; P<0.001) and lower peak heart rates (159±20 versus 184±9 beats/min; P<0.001). The mean QTc intervals were longer at peak exercise in patients (442±29 versus 422±19 ms; P<0.001). During submaximal exertion at comparable heart rates (114±6 versus 115±11 beats/min; P=0.54), the QTc interval had prolonged significantly more in patients than controls (37±28 versus 24±25 ms; P<0.016). The RR/QT slope, best described by a curvilinear relationship, was more gradual in patients than in controls (13.4; 95% confidence interval,12.8-13.9 versus 15.8; 95% confidence interval, 15.3-16.4 ms QT change per 10% change in RR interval; P<0.001) and steepest in patients within the highest body mass index tertile versus the lowest (13.9; 95% confidence interval, 12.9-14.9 versus 12.3; 95% confidence interval, 11.3-13.3; P=0.026). Conclusions-Despite

show abstract

“…The corrected QT interval on 12-lead ECG forms the basis of investigation, 11 although miscalculation is common leading either to overdiagnosis and inappropriate treatment or a missed diagnosis in an at-risk individual. 5,11,12 The 99th percentile for QTc in adult males is 470 ms and in adult females 480 ms, with significant overlap between the normal spectrum and genetically affected individuals with no or only mild QT prolongation.…”

Section: Investigations Clinical Evaluationmentioning

confidence: 99%

“…5,11,12 The 99th percentile for QTc in adult males is 470 ms and in adult females 480 ms, with significant overlap between the normal spectrum and genetically affected individuals with no or only mild QT prolongation. 12 Other supportive ECG features with greater specificity but more subjectivity are T-wave morphological abnormalities and T-wave alternans (Figure 1).…”

Section: Investigations Clinical Evaluationmentioning

confidence: 99%