Automated versus manual measurement of the QT interval and corrected QT interval.

BACKGROUND: The International Conference on Harmonization E14 Guideline specifies detailed assessment of QT interval or corrected QT interval prolongation when developing new drugs. We recently devised new software to precisely measure the QT interval. METHODS AND RESULTS: The QT intervals of all leads for a selected single heart beat were compared between automated measurement with the new software from Fukuda Denshi and manual measurement. With both automated and manual measurement, QT intervals obtained by the tangent method were shorter than those obtained by the differential threshold method, but the extent of correction was smaller. QT interval data obtained by the differential threshold method were more similar to values obtained by visual measurement than were data obtained by the tangent method, but the extent of correction was larger. Variability was related to the T-wave amplitude and to setting the baseline and tangent in the tangent method, while skeletal muscle potential noise affected the differential threshold method. Drift, low-amplitude recordings, and T-wave morphology were problems for both methods. Among the 12 leads, corrections were less frequent for leads II and V(3) -V(6) . CONCLUSION: We conclude that, for a thorough assessment of the QT/QTc interval, the tangent method or the differential threshold method appears to be suitable because of smaller interreader differences and better reproducibility. Correction of data should be done by readers who are experienced in measuring the QT interval. It is also important for electrocardiograms to have little noise and for a suitable heart rate and appropriate leads to be selected.

Classification and assessment of computerized diagnostic criteria for Brugada-type electrocardiograms.

BACKGROUND: Although a Brugada-type electrocardiogram (ECG) is occasionally detected in mass health screening examinations in apparently healthy individuals, the automatic computerized diagnostic criteria for Brugada-type ECGs have not been established. OBJECTIVE: This study was performed to establish the criteria for the computerized diagnosis of Brugada-type ECGs and to evaluate their diagnostic accuracy. METHODS: We examined the ECG parameters in leads V1 to V3 in patients with Brugada syndrome and cases with right bundle branch block. Based on the above parameters, we classified the ECGs into 3 types of Brugada-type ECGs, and the conditions for defining each type were explored as the diagnostic criteria. The diagnostic effectiveness of the proposed criteria was assessed using 548 ECGs from 49 cases with Brugada-type ECGs and the recordings from 192,673 cases (36,674 adults and 155,999 school children) obtained from their annual health examinations. RESULTS: The Brugada-type ST-segment elevation in V1 to V3 was classified into 3 types, types 1, 2/3, and a suggestive Brugada ECG (type S). The automatic diagnostic criteria for each type were established by the J-point amplitude, ST-segment elevation with its amplitude and configuration, as well as the T-wave morphology in leads V1 to V3. CONCLUSION: The proposed criteria demonstrated a reasonable accuracy (type 1: 91.9%, type 2/3: 86.2%, type S: 76.2%) for diagnosing Brugada-type ECG in comparison to the macroscopic diagnosis by experienced observers. Moreover, the automatic criteria had a comparable detection rate (0.6% in adults, 0.16% in children) of Brugada-type ECGs to the macroscopic inspection in the health screening examinations.

Automated detection of Brugada-type electrocardiogram using diagnostic criteria of the European Society of Cardiology and the American Heart Association.

The diagnostic criteria of Brugada syndrome were reported from the European Society of Cardiology (ESC) and the American Heart Association in 2002. We examined the automated detection of Brugada-type electrocardiogram (ECG) on 12-lead ECG analysis program by modifying ESC criteria and evaluated it. In ESC criteria, Brugada-type ECG was classified into 3 types of ST-segment abnormalities of V1 to V3 leads. We modified these criteria and determined automated detection criteria as follows: type 1: STj>or=0.2 mV and STj>ST1>ST2 and T<0 mV; type 2: STj>or=0.2 mV and STj>STmin>or=0.1 mV and T>0 mV and T<1.8xR' and Sor=0.2 mV and 0.1 mV>STmin>0 mV and T>0 mV and T<1.8xR' and S>or=3.0 mV; STj, ST1, and ST2 are amplitude of the ST segment (STj: J point, ST1: J point +40 milliseconds, ST2: J point +80 milliseconds). We evaluated these criteria with 97 ECGs from 27 patients, which are diagnosed as Brugada syndrome in university hospital. Brugada-type ECGs were detected correctly in 85 of total 97 ECGs (sensitivity, 88.7%, type 1: 32/32, type 2: 50/61, type 3: 4/4). As compared with 5 cardiologists interpretation of Brugada-type ECGs, computer classified incorrectly in 20 ECGs (type 1: 2, type 2: 17, type 3: 1) in 21,524 cases.

New holter monitoring analysis system: a calculation of the lead vectors.

BACKGROUND: A new system of synthesizing a 12-lead electrocardiogram (Syn-ECG) with practically identical waveforms to the standard 12-lead ECG (Stn-ECG) from 3-channel ECGs recorded by Holter monitoring has been developed. METHODS AND RESULTS: The study group comprised 16 healthy individuals and 13 patients with abnormal ECGs. The bipolar eV1, eV5 and eVF leads were recorded using digital Holter monitoring and nine Syn-ECGs, corresponding to each lead of the Stn-ECG, were synthesized. The 9 ECGs consisted of a theoretical Syn-ECG and 8 Syn-ECGs positioned around the theoretical Syn-ECG at 3 cm intervals on the Frank's image surface. Of the 9 ECGs, the Syn-ECG with the maximum product of the cross-correlation coefficient of the QRS wave and that of the T wave, was automatically selected as the optimal Syn-ECG. The amplitude data from the QRS wave, R wave, T wave, and ST level, and also the amplitude ratio of the R wave, T wave to the QRS wave, were significantly well correlated between the Syn-ECG and Stn-ECG. CONCLUSIONS: A practically identical ECG morphology, comparable with a Stn-ECG, was successfully created using this system.

QT dispersion correlates with systolic rather than diastolic parameters in patients receiving anthracycline treatment.

OBJECTIVE: The aim of this study was to investigate the relation of QT dispersion to left ventricular (LV) systolic and diastolic function in patients undergoing anthracycline therapy. METHODS: We used echocardiography to evaluate LV systolic and diastolic function and electrocardiography to evaluate QT dispersion and corrected QT dispersion (QTcD) in patients with hematological diseases, who received anthracycline therapy. PATIENTS: Seventy-two patients with hematological diseases who were receiving anthracycline treatment were enrolled in the present study. RESULTS: LV end-diastolic diameter or LV end-systolic diameter had a significant positive correlation to QTcD (r = 0.35, p < 0.01, r = 0.43, p < 0.01). Also left ventricular ejection fraction of (LVEF) or fractional shortening had a significant negative correlation to QTcD (r = -0.46, p < 0.001, r = -0.27, p = 0.02). The highest QTcD group had a significantly larger LV end-diastolic diameter or LV end-systolic diameter than the lowest QTcD [48.5 +/- 5.7 vs. 44.4 +/- 4.5 (mm), p < 0.001, 34.1 +/- 6.4 vs. 28.8 +/- 4.3 (mm), p < 0.001] and the highest QTcD group had a significantly lower LVEF than the lowest QTcD [57.5 +/- 8.0 vs. 65.5 +/- 6.4 (%), p < 0.001]. On the other hand, none of the diastolic function markers were significantly correlated with QTcD. CONCLUSION: We concluded that increased QTcD is correlated with LV dilation and systolic dysfunction induced by anthracycline therapy, and does not reflect a dispersion of ventricular repolarization or asynchronous motion.