Multiple dipole electrocardiography: A clinical study
Başlık:
Multiple dipole electrocardiography: A clinical study
Yazar:
Baxter, Ronald Henry, author.
ISBN:
9780438059030
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (208 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: T. D.V Lawrie.
Özet:
The majority of this thesis was concerned with the clinical evaluation of an electrocardiographic technique called the multiple dipole electrocardiogram (MDECG), Although conventional 12 lead electrocardiography has bean the basic technique for studying surface activity of the heart since the early 20th century, its shortcomings in detection of myocardial infarction and ischaemia in coronary artery disease, have been recognised. This has led to a search for new electrocardiographic techniques (Chapter l). In this thesis the conventional 12 lead EGG (ECG) with its theoretical basis of the equivalent cardiac generator or single dipole theory, was compared to the MDECG which was based on the concept of the heart as a multiple dipole source. Derivation of the MDECG was achieved by studying QRS potentials at 126 points on the surface of the chest by using a computer and a mathematical model of ventricular depolarisation. The MDECG was displayed both as a set of non negative dipole strength curves representing 10 individual areas of the heart, and numerically as average dipole activity in the same areas. The activation sequence of individual dipoles during the QRS period in normal subjects was similar to the observed spread of depolarisation wavefronts reported from experimental studies. The hypothesis that the dipole strength or activity reflected the amount pf viable myocardium was supported by the similarity of measured dipole activity in the right ventricle, the left ventricle and septum (16%, 54%, 30%) to the known weight of myocardium in those areas, (Chapter 2) and the finding of a significant increase in dipole activity in patients with left ventricular hypertrophy and a significant decrease in myocardial infarction. Furthermore it was found that all patients in the training group with ventricular hypertrophy had abnornially high dipole activity in the left ventricle and all those with recent anterior infarction had low activity. Some limitation in detection of inferior infarction was encountered as only 86% of the training group had low dipole activity. It was noted, however, that the technique appeared to detect infarction affecting the right ventricle in both anterior and inferior infarcts (Chapter 5). In general the MDECG performed more favourably than the EGG in detection of old infarction. This conclusion was based on a study of 91 patients with stable angina due to coronary artery disease. The MDECG suggested the presence of areas of infarction in 73%, but by comparision only 42% had Q waves on the EGG. Within this group 3B patients had a history of a previous myocardial infarction but the diagnosis could be confirmed by the current EGG in only 79% (on the basis of abnormal Q waves) whereas by MDECG in 81% (on the basis of low dipole activity). It was noted that many anginal subjects (40%) had normal resting EGGs, even in the presence of triple vessel coronary disease, but often had low dipole activity on the MDECG, (Chapter 4). The study then turned to the pre-infarction syndromes. Initially a retrospective study of out-patients with chest pain referred to a diagnostic out-patient EGG service showed that many had symptoms of unstable angina, but frequently had a normal EGG and seldom any evidence of myocardial infarction. However, a close study of 16 patients with acute coronary insufficiency who lacked conventional evidence of infarction or enzyme analysis of serial ECGs, showed that 63% had abnormal MDECGs, characterised by several areas of low dipole activity (Chapter 5). The MDECG with its ability to study discrete areas of the heart was then used in a detailed investigation of 34 patients after coronary artery surgery. It was found that whereas 14% developed post-operative infarction by EGG criteria, 56% had low dipole activity by MDECG, Fresh infarction (on MDECG criteria]) was particularly common in patients with persistence or recurrence of angina whereas, its absence was usually associated with relief of symptoms (87%). This suggested that the operation produced relief of symptoms due to improved coronary blood flow and not due to development of myocardial infarction in a previously ischaemic zone, (Chapter 6).
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684680.1) | 684680-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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