Multiscale Modeling of the Ventricles: From Cellular Electrophysiology to Body Surface Electrocardiograms

This work is focused on different aspects within the loop of multiscale modeling: On the cellular level, effects of adrenergic regulation and the Long-QT syndrome have been investigated. On the organ level, a model for the excitation conduction system was developed and the role of electrophysiological heterogeneities was analyzed. On the torso level a dynamic model of a deforming heart was created and the effects of tissue conductivities on the solution of the forward problem were evaluated

Evaluation of Cardiac Circadian Rhythm Deconditioning Induced by 5-to-60 Days of Head-Down Bed Rest

Head-down tilt (HDT) bed rest elicits changes in cardiac circadian rhythms, generating possible adverse health outcomes such as increased arrhythmic risk. Our aim was to study the impact of HDT duration on the circadian rhythms of heart beat (RR) and ventricular repolarization (QTend) duration intervals from 24-h Holter ECG recordings acquired in 63 subjects during six different HDT bed rest campaigns of different duration (two 5-day, two 21-day, and two 60-day). Circadian rhythms of RR and QTend intervals series were evaluated by Cosinor analysis, resulting in a value of midline (MESOR), oscillation amplitude (OA) and acrophase (f). In addition, the QTc (with Bazett correction) was computed, and day-time, night-time, maximum and minimum RR, QTend and QTc intervals were calculated. Statistical analysis was conducted, comparing: (1) the effects at 5 (HDT5), 21 (HDT21) and 58 (HDT58) days of HDT with baseline (PRE); (2) trends in recovery period at post-HDT epochs (R) in 5-day, 21-day, and 60-day HDT separately vs. PRE; (3) differences at R + 0 due to bed rest duration; (4) changes between the last HDT acquisition and the respective R + 0 in 5-day, 21-day, and 60-day HDT. During HDT, major changes were observed at HDT5, with increased RR and QTend intervals’ MESOR, mostly related to day-time lengthening and increased minima, while the QTc shortened. Afterward, a progressive trend toward baseline values was observed with HDT progression. Additionally, the f anticipated, and the OA was reduced during HDT, decreasing system’s ability to react to incoming stimuli. Consequently, the restoration of the orthostatic position elicited the shortening of RR and QTend intervals together with QTc prolongation, notwithstanding the period spent in HDT. However, the magnitude of post-HDT changes, as well as the difference between the last HDT day and R + 0, showed a trend to increase with increasing HDT duration, and 5/7 days were not sufficient for recovering after 60-day HDT. Additionally, the f postponed and the OA significantly increased at R + 0 compared to PRE after 5-day and 60-day HDT, possibly increasing the arrhythmic risk. These results provide evidence that continuous monitoring of astronauts’ circadian rhythms, and further investigations on possible measures for counteracting the observed modifications, will be key for future missions including long periods of weightlessness and gravity transitions, for preserving astronauts’ health and mission success

The Application of Computer Techniques to ECG Interpretation

This book presents some of the latest available information on automated ECG analysis written by many of the leading researchers in the field. It contains a historical introduction, an outline of the latest international standards for signal processing and communications and then an exciting variety of studies on electrophysiological modelling, ECG Imaging, artificial intelligence applied to resting and ambulatory ECGs, body surface mapping, big data in ECG based prediction, enhanced reliability of patient monitoring, and atrial abnormalities on the ECG. It provides an extremely valuable contribution to the field

Cardiac Arrhythmias

The most intimate mechanisms of cardiac arrhythmias are still quite unknown to scientists. Genetic studies on ionic alterations, the electrocardiographic features of cardiac rhythm and an arsenal of diagnostic tests have done more in the last five years than in all the history of cardiology. Similarly, therapy to prevent or cure such diseases is growing rapidly day by day. In this book the reader will be able to see with brighter light some of these intimate mechanisms of production, as well as cutting-edge therapies to date. Genetic studies, electrophysiological and electrocardiographyc features, ion channel alterations, heart diseases still unknown , and even the relationship between the psychic sphere and the heart have been exposed in this book. It deserves to be read

Elektrokardiografiset repolarisaatiomuuttujat sydäninfarktin ja iskemian toteamisessa

The aim of the studies was to improve the diagnostic capability of electrocardiography (ECG) in detecting myocardial ischemic injury with a future goal of an automatic screening and monitoring method for ischemic heart disease. The method of choice was body surface potential mapping (BSPM), containing numerous leads, with intention to find the optimal recording sites and optimal ECG variables for ischemia and myocardial infarction (MI) diagnostics. The studies included 144 patients with prior MI, 79 patients with evolving ischemia, 42 patients with left ventricular hypertrophy (LVH), and 84 healthy controls. Study I examined the depolarization wave in prior MI with respect to MI location. Studies II-V examined the depolarization and repolarization waves in prior MI detection with respect to the Minnesota code, Q-wave status, and study V also with respect to MI location. In study VI the depolarization and repolarization variables were examined in 79 patients in the face of evolving myocardial ischemia and ischemic injury. When analyzed from a single lead at any recording site the results revealed superiority of the repolarization variables over the depolarization variables and over the conventional 12-lead ECG methods, both in the detection of prior MI and evolving ischemic injury. The QT integral, covering both depolarization and repolarization, appeared indifferent to the Q-wave status, the time elapsed from MI, or the MI or ischemia location. In the face of evolving ischemic injury the performance of the QT integral was not hampered even by underlying LVH. The examined depolarization and repolarization variables were effective when recorded in a single site, in contrast to the conventional 12-lead ECG criteria. The inverse spatial correlation of the depolarization and depolarization waves in myocardial ischemia and injury could be reduced into the QT integral variable recorded in a single site on the left flank. In conclusion, the QT integral variable, detectable in a single lead, with optimal recording site on the left flank, was able to detect prior MI and evolving ischemic injury more effectively than the conventional ECG markers. The QT integral, in a single-lead or a small number of leads, offers potential for automated screening of ischemic heart disease, acute ischemia monitoring and therapeutic decision-guiding as well as risk stratification.Perinteinen sydäninfarktin ja sepelvaltimotautikohtauksen elektrokardiografinen (EKG) diagnostiikka perustuu laadullisiin piirteisiin 12-kytkentäisessä EKG:ssa. Väitöskirjatutkimuksen tarkoituksena oli parantaa EKG-diagnostiikkaa sydäninfarktin ja iskemian havaitsemisessa.. Lopullisena päämääränä on kehittää iskeemisen sydänsairauden automaattinen seulonta- ja monitorointimenetelmä. Väitöskirjatutkimuksen osatyöt tähtäsivät sydäninfarkti- ja iskemiadiagnostiikassa parhaiden rekisteröintipaikkojen löytämiseen yksittäisissä kytkennöissä ja parhaiden kvantitatiivisten EKG-muuttujien löytämiseen. Tutkimuksen työkaluna käytettiin sydänsähkökäyrän kehokartoitusta (body surface potential mapping, BSPM), jossa sydämen tuottamaa sähköistä potentiaalia rekisteröidään koko ylävartalon alueelta lukuisten elektrodien avulla. Tutkimushenkilöinä oli 144 aiemmin sydäninfarktin sairastanutta potilasta, 79 potilasta, joilla oli äkillinen sepelvaltimotautikohtaus, 42 potilasta, joilla oli vasemman kammion hypertrofia ja 84 tervettä vapaaehtoista. Sydäninfarkti ja sepelvaltimotauti varmennettiin tai paikannettiin sepelvaltimoiden ja vasemman kammion varjoainekuvauksella, sydämen kaikukuvauksella, sydänlihasmerkkiaineilla tai sydämen magneettitutkimuksella. Osatutkimuksissa I-V tarkasteltiin sydämen sähköistä aktivoitumis- ja palautumisvaiheita eli depolarisaatio- ja repolarisaatiovaiheita kuvaavia muuttujia aiemman sydäninfarktin diagnostiikassa sekä paikannuksessa perinteiseen EKG-diagnostiikkaan verrattuna. Kuudennessa osatutkimuksessa näitä muuttujia tarkasteltiin äkillisen sepeolvaltimotautikohtauksen aikana. Sydämen sähköisen palautumis- eli repolarisaatiovaiheen muuttujat EKG:ssa osoittautuivat aktivaatio- eli depolarisaatiovaiheen muuttujia paremmiksi sekä aiemman sydäninfarktin että äkillisen sepelvaltimotautikohtauksen diagnostiikassa Yhdestä kytkennästä rekisteröitävä QT-integraali, joka käsittää sekä sähköisen aktivaatio- että palautumisvaiheen, osoittautui vakaaksi diagnostiseksi muuttujaksi ja riippumattomaksi infarktin iästä, sijainnista, vasemman kammion hypertrofiasta tai mahdollisesta Q-aallosta ja oli perinteisiä EKG:n tulkintatapoja tehokkaampi. Tämä muuttuja tarjoaa mahdollisuuksia sepelvaltimotaudin automaattiseen seulontaan ja äkillisen sepelvaltimotautikohtauksen monitorointiin hoitopäätöksiä ja riskinarviointia ajatellen