Vectorcardiographic diagnostic & prognostic information derived from the 12-lead electrocardiogram

This thesis consists of a number of studies revolving around the leading research theme, i.e., the derivation of new vectorcardiographic diagnostic & prognostic information from the 12-lead electrocardiogram (ECG). Various research questions have been addressed, but most studies use a similar data processing approach, consisting of initial mathematical synthesis of a vectorcardiogram (VCG) from a standard 12-lead ECG, followed by the measurement of general VCG characteristics like maximal QRS- and T vectors, QRS- and T integrals, the spatial QRS-T angle (SA) and the ventricular gradient (VG). Studies focus on methodological as well as on clinical issues, and are discussed in the thesis.Hartstichting Fysiologic ECG services B.V. LEADS Online B.V. Hartis Medisch CentrumUBL - phd migration 201

Subtraction electrocardiography: Detection of ischemia-induced ST displacement without the need to identify the J point

AbstractBackgroundWhen triaging a patient with acute chest pain at first medical contact, an electrocardiogram (ECG) is routinely made and inspected for signs of myocardial ischemia. The guidelines recommend comparison of the acute and an earlier-made ECG, when available. No concrete recommendations for this comparison exist, neither is known how to handle J-point identification difficulties. Here we present a J-point independent method for such a comparison.MethodsAfter conversion to vectorcardiograms, baseline and acute ischemic ECGs after 3minutes of balloon occlusion during elective PCI were compared in 81 patients of the STAFF III ECG database. Baseline vectorcardiograms were subtracted from ischemic vectorcardiograms using either the QRS onsets or the J points as synchronization instants, yielding vector magnitude difference signals, ΔH. Output variables for the J-point synchronized differences were ΔH at the actual J point and at 20, 40, 60 and 80ms thereafter. Output variables for the onset-QRS synchronized differences were the ΔH at 80, 100, 120, 140 and 160ms after onset QRS. Finally, linear regressions of all combinations of ΔHJ+… versus ΔHQRS+… were made, and the best combination was identified.ResultsThe highest correlation, 0.93 (p<0.01), was found between ΔH 40ms after the J point and 160ms after the onset of the QRS complex. With a ΔH ischemia threshold of 0.05mV, 66/81 (J-point synchronized differences) and 68/81 (onset-QRS synchronized differences) subjects were above the ischemia threshold, corresponding to sensitivities of 81% and 84%, respectively.ConclusionOur current study opens an alternative way to detect cardiac ischemia without the need for human expertise for determination of the J point by measuring the difference vector magnitude at 160ms after the onset of the QRS complex

Vectorcardiographic diagnostic & prognostic information derived from the 12-lead electrocardiogram

This thesis consists of a number of studies revolving around the leading research theme, i.e., the derivation of new vectorcardiographic diagnostic & prognostic information from the 12-lead electrocardiogram (ECG). Various research questions have been addressed, but most studies use a similar data processing approach, consisting of initial mathematical synthesis of a vectorcardiogram (VCG) from a standard 12-lead ECG, followed by the measurement of general VCG characteristics like maximal QRS- and T vectors, QRS- and T integrals, the spatial QRS-T angle (SA) and the ventricular gradient (VG). Studies focus on methodological as well as on clinical issues, and are discussed in the thesis

Beats: An Interactive Research Oriented ECG Analysis System

Abstract We developed BEATS (Beat Editing And Tracking Software), an interactive program to extract beat-to-beat information about the QRST complex. It is aimed at recordings of intermediate length, typically 20 minutes, corresponding to an average exercise ECG. BEATS accepts any 8-channel ECG recording which is then converted into a 3-channel vectorcardiographic X, Y, Z representation and the spatial velocity. After beat detection the user aids the program in determining the global positions of the onset QRS, J point and T apex at several different heart rates. From the global T apices the local T apex, the steepest slope in the descending limb of the T wave and the end of the T wave are determined. BEATS produces a file with baseline corrected signals and a file with the parameters for each QRST complex. These files can be used as input for other programs that run unattended and extract QRST features like QRS-and T-integrals, QRST angle, etc

Electrical remodeling after percutaneous atrial septal defect closure in pediatric and adult patients

Background: Several studies have reported changes in electrocardiographic variables after atrial septal defect (ASD) closure. However no temporal electro-and vectorcardiographic changes have been described from acute to long-term follow-up at different ages. We aimed to study electrical remodeling after percutaneous ASD closure in pediatric and adult patients. Methods: ECGs of 69 children and 75 adults (median age 6 [IQR 4–11] years and 45 [IQR 33–54] years, respectively) were retrospectively selected before percutaneous ASD closure and at acute (1–7 days), intermediate (4–14 weeks) and late (6–18 months) follow-up. Apart from electrocardiographic variables, spatial QRS-T angle and ventricular gradient (VG) were derived from mathematically-synthesized vectorcardiograms. Results: In both pediatric and adult patients, the heart rate decreased immediately post-closure, which persisted to late follow-up. The P-wave amplitude also decreased acutely post-closure, but remained unchanged at later follow-up. The PQ duration shortened immediately in children and at intermediate follow-up in adults. The QRS duration and QTc interval decreased at intermediate-term follow-up in both children and adults. In both groups the spatial QRS-T angle decreased at late follow-up. The VG magnitude increased at intermediate follow-up in children and at late follow-up in adults, after an initial decrease in children. Conclusion: In both pediatric and adult ASD patients, electrocardiographic changes mainly occurred directly after ASD closure except for shortening of QRS duration and QTc interval, which occurred at later follow-up. Adults also showed late changes in PQ duration. At 6-to-18 month post-closure, the spatial QRS-T angle decreased, reflecting increased electrocardiographic concordance. The initial acute decrease in VG in children, which was followed by a significant increase, may be the effect of action potential duration dynamics directly after percutaneous ASD closure

Electrical remodeling after percutaneous atrial septal defect closure in pediatric and adult patients

Background: Several studies have reported changes in electrocardiographic variables after atrial septal defect (ASD) closure. However no temporal electro-and vectorcardiographic changes have been described from acute to long-term follow-up at different ages. We aimed to study electrical remodeling after percutaneous ASD closure in pediatric and adult patients. Methods: ECGs of 69 children and 75 adults (median age 6 [IQR 4–11] years and 45 [IQR 33–54] years, respectively) were retrospectively selected before percutaneous ASD closure and at acute (1–7 days), intermediate (4–14 weeks) and late (6–18 months) follow-up. Apart from electrocardiographic variables, spatial QRS-T angle and ventricular gradient (VG) were derived from mathematically-synthesized vectorcardiograms. Results: In both pediatric and adult patients, the heart rate decreased immediately post-closure, which persisted to late follow-up. The P-wave amplitude also decreased acutely post-closure, but remained unchanged at later follow-up. The PQ duration shortened immediately in children and at intermediate follow-up in adults. The QRS duration and QTc interval decreased at intermediate-term follow-up in both children and adults. In both groups the spatial QRS-T angle decreased at late follow-up. The VG magnitude increased at intermediate follow-up in children and at late follow-up in adults, after an initial decrease in children. Conclusion: In both pediatric and adult ASD patients, electrocardiographic changes mainly occurred directly after ASD closure except for shortening of QRS duration and QTc interval, which occurred at later follow-up. Adults also showed late changes in PQ duration. At 6-to-18 month post-closure, the spatial QRS-T angle decreased, reflecting increased electrocardiographic concordance. The initial acute decrease in VG in children, which was followed by a significant increase, may be the effect of action potential duration dynamics directly after percutaneous ASD closure

Mitochondrial diseases in Hong Kong: prevalence, clinical characteristics and genetic landscape

Abstract Objective To determine the prevalence of mitochondrial diseases (MD) in Hong Kong (HK) and to evaluate the clinical characteristics and genetic landscape of MD patients in the region. Methods This study retrospectively reviewed the phenotypic and molecular characteristics of MD patients from participating public hospitals in HK between January 1985 to October 2020. Molecularly and/or enzymatically confirmed MD cases of any age were recruited via the Clinical Analysis and Reporting System (CDARS) using relevant keywords and/or International Classification of Disease (ICD) codes under the HK Hospital Authority or through the personal recollection of treating clinicians among the investigators. Results A total of 119 MD patients were recruited and analyzed in the study. The point prevalence of MD in HK was 1.02 in 100,000 people (95% confidence interval 0.81–1.28 in 100,000). 110 patients had molecularly proven MD and the other nine were diagnosed by OXPHOS enzymology analysis or mitochondrial DNA depletion analysis with unknown molecular basis. Pathogenic variants in the mitochondrial genome (72 patients) were more prevalent than those in the nuclear genome (38 patients) in our cohort. The most commonly involved organ system at disease onset was the neurological system, in which developmental delay, seizures or epilepsy, and stroke-like episodes were the most frequently reported presentations. The mortality rate in our cohort was 37%. Conclusion This study is a territory-wide overview of the clinical and genetic characteristics of MD patients in a Chinese population, providing the first available prevalence rate of MD in Hong Kong. The findings of this study aim to facilitate future in-depth evaluation of MD and lay the foundation to establish a local MD registry