Heart rate variability derived from exercise ECG in the detection of coronary artery disease.

Physiol Meas. 2007 Oct;28(10):1189-200. Epub 2007 Sep 18.

Cardiovascular effects of short term exposure to electric and magnetic fields of electricity power transmission

In the electrical industry the 50 Hz electric and magnetic fields are often higher than in the average working environment. The electric and magnetic fields can be studied by measuring or by calculatingthe fields in the environment. For example, the electric field under a 400 kV power line is 1 to 10 kV/m, and the magnetic flux density is 1 to 15 µT. Electricand magnetic fields of a power line induce a weak electric field and electric currents in the exposed body. The average current density in a human being standing under a 400 kV line is 1 to 2 mA/m2. The aim of this study is to find out thepossible effects of short term exposure to electric and magnetic fields of electricity power transmission on workers' health, in particular the cardiovascular effects. The study consists of two parts; Experiment I: influence on extrasystoles, and Experiment II: influence on heart rate. In Experiment I two groups, 26 voluntary men (Group 1) and 27 transmission-line workers (Group 2), were measured. Their electrocardiogram (ECG) was recorded with an ambulatory recorder both in and outside the field. In Group 1 the fields were 1.7 to 4.9 kV/m and 1.1 to 7.1 pT; in Group 2 they were 0.1 to 10.2 kV/m and 1.0 to 15.4 pT. In the ECG analysis the only significant observation was a decrease in the heart rate after field exposure (Group 1). The drop cannot be explained with the first measuring method. Therefore Experiment II was carried out. In Experiment II two groups were used; Group 1 (26 male volunteers) were measured in real field exposure, Group 2 (15 male volunteers) in "sham" fields. The subjects of Group 1 spent 1 h outside the field, then 1 h in the field under a 400 kV transmission line, and then again 1 h outside the field. Under the 400 kV linethe field strength varied from 3.5 to 4.3 kV/m, and from 1.4 to 6.6 pT. Group 2spent the entire test period (3 h) in a 33 kV outdoor testing station in a "sham" field. ECG, blood pressure, and electroencephalogram (EEG) were measured by ambulatory methods. Before and after the field exposure, the subjects performed some cardiovascular autonomic function tests. The analysis of the results (Experiments I and II) showed that extrasystoles or arrythmias were as frequent in the field (below 4 kV/m and 4 pT) as outside it. In Experiment II there was no decrease detected in the heart rate, and the systolic and diastolic blood pressure stayed nearly the same. No health effects were found in this study.

CT and PET/CT Hybrid Imaging of Coronary Artery Disease

Coronary artery disease (CAD) is a chronic process that evolves over decades and may culminate in myocardial infarction (MI). While invasive coronary angiography (ICA) is still considered the gold standard of imaging CAD, non-invasive assessment of both the vascular anatomy and myocardial perfusion has become an intriguing alternative. In particular, computed tomography (CT) and positron emission tomography (PET) form an attractive combination for such studies. Increased radiation dose is, however, a concern. Our aim in the current thesis was to test novel CT and PET techniques alone and in hybrid setting in the detection and assessment of CAD in clinical patients. Along with diagnostic accuracy, methods for the reduction of the radiation dose was an important target. The study investigating the coronary arteries of patients with atrial fibrillation (AF) showed that CAD may be an important etiology of AF because a high prevalence of CAD was demonstrated within AF patients. In patients with suspected CAD, we demonstrated that a sequential, prospectively ECG-triggered CT technique was applicable to nearly 9/10 clinical patients and the radiation dose was over 60% lower than with spiral CT. To detect the functional significance of obstructive CAD, a novel software for perfusion quantification, CarimasTM, showed high reproducibility with 15O-labelled water in PET, supporting feasibility and good clinical accuracy. In a larger cohort of 107 patients with moderate 30-70% pre-test probability of CAD, hybrid PET/CT was shown to be a powerful diagnostic method in the assessment of CAD with diagnostic accuracy comparable to that of invasive angiography and fractional flow reserve (FFR) measurements. A hybrid study may be performed with a reasonable radiation dose in a vast majority of the cases, improving the performance of stand-alone PET and CT angiography, particularly when the absolute quantification of the perfusion is employed. These results can be applied into clinical practice and will be useful for daily clinical diagnosis of CAD.

Factors predicting mortality in type 2 diabetes. With special reference to physical exercise, blood pressure, proteinuria, inflammation and P wave duration

Background: Type 2 diabetes patients have a 2-4 fold risk of cardiovascular disease (CVD) compared to the general population. In type 2 diabetes, several CVD risk factors have been identified, including obesity, hypertension, hyperglycemia, proteinuria, sedentary lifestyle and dyslipidemia. Although much of the excess CVD risk can be attributed to these risk factors, a significant proportion is still unknown. Aims: To assess in middle-aged type 2 diabetic subjects the joint relations of several conventional and non-conventional CVD risk factors with respect to cardiovascular and total mortality. Subjects and methods: This thesis is part of a large prospective, population based East-West type 2 diabetes study that was launched in 1982-1984. It includes 1,059 middle-aged (45-64 years old) participants. At baseline, a thorough clinical examination and laboratory measurements were performed and an ECG was recorded. The latest follow-up study was performed 18 years later in January 2001 (when the subjects were 63-81 years old). The study endpoints were total mortality and mortality due to CVD, coronary heart disease (CHD) and stroke. Results: Physically more active patients had significantly reduced total, CVD and CHD mortality independent of high-sensitivity C-reactive protein (hs-CRP) levels unless proteinuria was present. Among physically active patients with a hs-CRP level >3 mg/L, the prognosis of CVD mortality was similar to patients with hs-CRP levels ≤3 mg/L. The worst prognosis was among physically inactive patients with hs-CRP levels >3 mg/L. Physically active patients with proteinuria had significantly increased total and CVD mortality by multivariate analyses. After adjustment for confounding factors, patients with proteinuria and a systolic BP <130 mmHg had a significant increase in total and CVD mortality compared to those with a systolic BP between 130 and 160 mmHg. The prognosis was similar in patients with a systolic BP <130 mmHg and ≥160 mmHg. Among patients without proteinuria, a systolic BP <130 mmHg was associated with a non-significant reduction in mortality. A P wave duration ≥114 ms was associated with a 2.5-fold increase in stroke mortality among patients with prevalent CHD or claudication. This finding persisted in multivariable analyses. Among patients with no comorbidities, there was no relationship between P wave duration and stroke mortality. Conclusions: Physical activity reduces total and CVD mortality in patients with type 2 diabetes without proteinuria or with elevated levels of hs-CRP, suggesting that the anti-inflammatory effect of physical activity can counteract increased CVD morbidity and mortality associated with a high CRP level. In patients with proteinuria the protective effect was not, however, present. Among patients with proteinuria, systolic BP <130 mmHg may increase mortality due to CVD. These results demonstrate the importance of early intervention to prevent CVD and to control all-cause mortality among patients with type 2 diabetes. The presence of proteinuria should be taken into account when defining the target systolic BP level for prevention of CVD deaths. A prolongation of the duration of the P wave was associated with increased stroke mortality among high-risk patients with type 2 diabetes. P wave duration is easy to measure and merits further examination to evaluate its importance for estimation of the risk of stroke among patients with type 2 diabetes.

Toward a Reliable Classifier For Arrhythmia Diagnosis

Illnesses related to the heart are one of the major reasons for death all over the world causing many people to lose their lives in last decades. The good news is that many of those sicknesses are preventable if they are spotted in early stages. On the other hand, the number of the doctors are much lower than the number of patients. This will makes the auto diagnosing of diseases even more and more essential for humans today. Furthermore, when it comes to the diagnosing methods and algorithms, the current state of the art is lacking a comprehensive study on the comparison between different diagnosis solutions. Not having a single valid diagnosing solution has increased the confusion among scholars and made it harder for them to take further steps. This master thesis will address the issue of reliable diagnosing algorithm. We investigate ECG signals and the relation between different diseases and the heart’s electrical activity. Also, we will discuss the necessary steps needed for auto diagnosing the heart diseases including the literatures discussing the topic. The main goal of this master thesis is to find a single reliable diagnosing algorithm and quest for the best classifier to date for heart related sicknesses. Five most suited and most well-known classifiers, such as KNN, CART, MLP, Adaboost and SVM, have been investigated. To have a fair comparison, the ex-periment condition is kept the same for all classification methods. The UCI repository arrhythmia dataset will be used and the data will not be preprocessed. The experiment results indicates that AdaBoost noticeably classifies different diseases with a considera-bly better accuracy.

Sydämen eteisvärinän tunnistaminen matkapuhelimen kiihtyvyysanturilla

Yli 140 miljoonaa ihmistä kärsii kroonisesta eteisvärinästä. Monilla ihmisillä on eteisvärinää, vaikkeivat siitä itse tiedä. Hoito on yksinkertainen, mutta hoidon piiriin eivät päädy kaikki yksinkertaisten seulontamenettelyjen tuloksena. Elektrokardiogrammi (EKG) sydämen toimintojen tunnistusmenetelmänä on tällä hetkellä yleisin vaihtoehto eteisvärinän seulontaan. EKG-laitteet ovat arvokkaita ja haasteellisia yksittäisen käyttäjän arkielämän kannalta. Vaihtoehtoinen sydämen monitorointimenetelmä on ballistokardiografinen (BKG) mittaus. EKG:n ja BKG:n ominaisia piirteitä käydään lävitse ja vertaillaan vahvuuksia sekä heikkouksia näiden kahden mittausmenetelmän välillä. BKG:ta on tutkittu jo pitkään, mutta mittaukseen soveltuvia tähän käyttökohteeseen varsinaisesti suunniteltuja laitteita ei ole paljoakaan tuotteistettu markkinoille asti. Työssä tutkitaan matkapuhelimen kiihtyvyysanturin soveltuvuutta BKG-mittauksen suorittamiseen. Tällä menetelmällä on mahdollista tuoda helposti sydänmonitori lähelle ihmisiä ja jokainen voi omalla matkapuhelimellaan tarkkailla sydämensä toimintaa. Diplomityössä selvitetään erilaisten markkinoilla olevien mobiililaitteiden soveltuvuutta kiihtyvyysanturitutkimukseen. Useampaa mallia koskevan selvitystyön tuloksena valitaan parhaiten toimiva vaihtoehto, jolla jatketaan tutkimusta suunnittelemalla mittausprosessi. Ensimmäisen vaiheen mittauksissa valitaan 20 perustervettä koehenkilöä tutkimukseen. Tutkimuksen tuloksena saadaan tutkimushypoteesin mukainen tulos ja sydämen lyönnit saadaan tunnistettua kaikilla koehenkilöillä. Ensimmäisen vaiheen aikana suoritetaan myös liikehäiriötutkimusta. Tässä suoritetaan yksinkertaiset käden, jalan ja pään liikkeiden vaikutuksen arvioinnit kiihtyvyysanturisignaaliin. Lisäksi selvitetään, miten puhuminen mittauksen aikana välittyy tutkimuslaitteeseen ja suoritetaan arvio siitä, miten tämä voidaan ottaa huomioon. Ensimmäisen vaiheen havaintojen perusteella jatkokehitetään mittausprosessia ja pyritään optimoimaan tätä, jotta laajempi otosjoukko on mahdollista saavuttaa mahdollisimman vähän aikaresursseja kuluttaen. Työssä valmistellaan laajemman, 1000 koehenkilöä sisältävän, toisen tutkimusvaiheen suoritusta. Diplomityön osana valmistellaan Varsinais-Suomen Sairaanhoitopiirin eettiselle toimikunnalle lausuntohakemus tutkimukselle. Hakemuksessa käsitellään laajasti tutkimuksen suorittamista eri osa-alueilla. Toisen vaiheen tuloksen noudattaessa tutkimushypoteesia, voidaan todeta matkapuhelimen kiihtyvyysanturin olevan soveluva menetelmä sydämen toiminnan tutkimiseen.