Low-Cost Fetal Magnetocardiography: A Comparison of Superconducting Quantum Interference Device and Optically Pumped Magnetometers.

Background Fetal magnetocardiography (fMCG) is a highly effective technique for evaluation of fetuses with life-threatening arrhythmia, but its dissemination has been constrained by the high cost and complexity of Superconducting Quantum Interference Device (SQUID) instrumentation. Optically pumped magnetometers (OPMs) are a promising new technology that can replace SQUIDs for many applications. This study compares the performance of an fMCG system, utilizing OPMs operating in a person-sized magnetic shield, to that of a conventional fMCG system, utilizing SQUID magnetometers operating in a magnetically shielded room. Methods and Results fMCG recordings were made in 24 subjects using the SQUID system with the mother lying supine in a magnetically shielded room and the OPM system with the mother lying prone in a person-sized, cylindrical shield. Signal-to-noise ratios of the OPM and SQUID recordings were not statistically different and were adequate for diagnostic purposes with both technologies. Although the environmental noise was higher using the small open-ended shield, this was offset by the higher signal amplitude achieved with prone positioning, which reduced the distance between the fetus and sensors and improved patient comfort. In several subjects, fMCG provided a differential diagnosis that was more precise and/or definitive than was possible with echocardiography alone. Conclusions The OPM-based system was portable, improved patient comfort, and performed as well as the SQUID-based system at a small fraction of the cost. Electrophysiological assessment of fetal rhythm is now practical and will have a major impact on management of fetuses with long QT syndrome and other life-threatening arrhythmias.

Non-episode-dependent assessment of paroxysmal atrial fibrillation through measurement of RR interval dynamics and atrial premature contractions.

A method is presented for classifying a single lead surface electrocardiogram recording from a Holter monitor as being from a subject with paroxysmal atrial fibrillation (PAF) or not. The technique is based on first assessing the likelihood of 30-min segments of electrocardiogram (ECG) being from a subject with PAF, and then combining these per-segment likelihoods to form a per-subject classification. The per-segment assessment is based on the output of a supervised linear discriminant classifier (LDC) which has been trained using known data from the Physionet Atrial Fibrillation Prediction Database (which consists of two hundred 30-min segments of Holter ECG, taken from 53 subjects with PAF, and 47 without). One of two LDCs is used depending on whether there is a significant correlation between observed low-frequency and high-frequency spectral power in the RR power spectral density over the 30-min segment. If there is high correlation, then the LDC uses spectral features calculated over a 10-min window; in the low-correlation case, both spectral features and atrial premature contractions are used as features. The classifier was tested for its ability to distinguish PAF and non-PAF segments using three independent data sets (representing a total of 1370 segments from 50 subjects). The cumulative sensitivity, specificity, and accuracy on a per-segment basis were 43.0, 99.3, and 80.5%, respectively on these independent test sets. By combining the results of segment classification, a per-subject classification into PAF and non-PAF classes was performed. For the 50 subjects in the independent data sets, the sensitivity and specificity of the per-subject classifier were 100%.

Predictors of persistent palpitations and continued medical utilization.

BACKGROUND: The aim of this study was to determine the predictors of persistent palpitations and continued medical utilization in a sample of medical patients referred for ambulatory electrocardiographic monitoring. METHODS: A prospective telephone follow-up was conducted with patients who had undergone ambulatory electrocardiographic monitoring 3 months earlier. At inception, patients completed in-person interviews and self-report questionnaires, assessing somatization, hypochondriacal attitudes, bodily amplification (high degree of sensitivity to bodily sensations), and two types of life stress (minor daily irritants and major life changes). At follow-up, patients completed a structured interview about their clinical course, palpitations, and utilization of medical care during the interval. RESULTS: At 3-month follow-up, 55 of the inception cohort of 67 patients were interviewed again. The mean severity of palpitations for the entire sample declined significantly, but 46 (83.6%) patients continued to experience their presenting symptoms. Stepwise multiple linear regression revealed that the interaction of bodily amplification and daily life stress at inception uniquely explained 10.0% of the variance in palpitation severity at follow-up. A four-step model composed of these two interaction terms and age and education level accounted for 21.4% of the variance in palpitations. The medical utilization findings are complementary in that the interaction of amplification and daily irritants at baseline predicted the number of unscheduled medical visits over the subsequent 3 months. The total number of ventricular premature contractions occurring during ambulatory monitoring was not a significant predictor of palpitations. CONCLUSIONS: Palpitations are more persistent in persons who are both highly sensitive to bodily sensations and who experience a greater number of minor daily irritants. The existence of either predictor alone is not sufficient to perpetrate this functional somatic symptom; it requires the combination of these predictors.

[Problems in the diagnosis and clinical assessment of atrial dissociation (a report on 2 cases and review of the literature)]. / Voprosy diagnostiki i klinicheskoi otsenki predserdnoi dissotsiatsii (soobshchenie o dvukh sluchaiakh nabliudeniia i obzor literatury).

At registration of ECG esophageal leads in two patients with ischemic heart disease an extra atrial rhythm was recorded missed by standard ECG. Similar cases from the literature are considered.