Automatic identification of a stable QRST complex for non-invasive evaluation of human cardiac electrophysiology.

Background: A vectorcardiography approach to electrocardiology contributes to the non-invasive assessment of electrical heterogeneity in the ventricles of the heart and to risk stratification for cardiac events including sudden cardiac death. The aim of this study was to develop an automatic method that identifies a representative QRST complex (QRSonset to Tend) from a Frank vectorcardiogram (VCG). This method should provide reliable measurements of morphological VCG parameters and signal when such measurements required manual scrutiny.

Spatial peak and mean QRS-T angles: A comparison of similar but different emerging risk factors for cardiac death.

Background: The spatial peak and mean QRS-T angles are scientifically but not clinically established risk factors for cardiovascular events including cardiac death. The study aims were to compare these angles, assess their association with hypertension (HT) and diabetes mellitus (DM), and explore the relation between the mean QRS-T angle and the ventricular gradient (VG; reflecting electrical heterogeneity), which both are derived from the QRSarea and Tarea vectors.

Methods: Altogether 1094 participants (aged 50-65 years, 550 women) from the pilot of the population-based Swedish CArdioPulmonary bioImage Study with Frank vectorcardiographic recordings were included and divided into 5 subgroups: apparently healthy n = 320; HT n = 311; DM n = 33; DM + HT n = 53; miscellaneous conditions n = 377.

Ventricular repolarization duration and dispersion adaptation after atropine induced rapid heart rate increase in healthy adults.

Background: Proper adaptation of ventricular repolarization (VR) to rapid heart rate (HR) increase is crucial for cardiac electro-mechanical function. The pattern and temporal aspects of this adaptation and its components (duration and dispersion) during normal conduction are, however, incompletely known in humans and were the topic of this study.

Methods & Results: The VR duration (QT & QTpeak) and dispersion (Tamplitude, Tarea & ventricular gradient; VG) responses were studied by continuous vectorcardiogram after a bolus injection of atropine 0.

Instability of repolarization in LQTS mutation carriers compared to healthy control subjects assessed by vectorcardiography.

Background: Potassium channel dysfunction in congenital and acquired forms of long QT syndrome types 1 and 2 (LQT1 and LQT2) increases the beat-to-beat variability of the QT interval.

Objective: To study about the little known variability (instability) of other aspects of ventricular repolarization (VR) in humans by using vectorcardiography.

Methods: Beat-to-beat analysis was performed regarding vectorcardiography derived RR, QRS, and QT intervals, as well as T vector- and T vector loop-based parameters during 1-minute recordings of uninterrupted sinus rhythm at rest in 41 adult LQT1 (n = 31) and LQT2 (n = 10) mutation carriers and 41 age- and sex-matched control subjects.