Spatial vectorcardiography. II.
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A realistic computer model of propagation of ventricular activation was used to study the effects of varying the position of specific conduction system terminations in the left ventricle and the septum, representing the sites of initial activation, on the resulting simulated spatial heart vectors. Three differently localized foci of initial activation, each of them represented by one model element, were considered: in the central part of the left septal surface, posteriorly at about one third of the distance from the apex to the base, and in the upper part of the anterior free wall. During the model experiments, the positions of the initial activation were shifted +/- 5 model units (ca 5 mm) in the vertical and lateral direction either separately or in different mutual combinations. Small variations of the initial activation site in the basal parts of the left ventricle led to significantly smaller changes of the vectorcardiographic loop than variations of the same extent with the initial activation site located more apically.
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In 44 consecutive patients undergoing elective open heart surgery (OHS), serial electrocardiograms (ECG), vectorcardiograms (VCG), serum CPK, cardiac isoenzymes (CPKMB), and myocardial images using Tc-99m pyrophosphate were obtained, before and after the operation, for the detection of acute myocardial infarction (AMI). Twenty-nine patients developed one or more positive tests postoperatively. Two patients had positive myocardial scintiscans; both had other evidence of infarction. Conversely, the appearance of CPKMB, or new ECG and VCG changes, occurred frequently without evidence of infarction, and were not associated with the development of a positive scintiscan. The results show that false-negative results are infrequent in patients imaged early after OHS, and that cardiac surgical procedures do not cause a high incidence of false-positive scintigrams. Consequently, radionuclide imaging for AMI offers an important adjunct for excluding acute infarction following open heart surgery.
In order to improve the evaluation of the site and extent of the necrosis in acute myocardial infarction without Q wave (IMNQ), we used a multiparametric method taking into account the enzymatic values of the total CK, a score derived from Frank's VCG and a kinetic score of the VG segments estimated by echo-2D. The literature data have shown, according to the clinical and anatomical correlations, the frequency of the transmural lesions in the IMNQ cases and, on the contrary, of the lesions limited to the endocardial region and partially transmural in infarctions with new pathological Q waves. The heterogeneousness of the anatomo-pathological data can be explained by the mechanisms of the ischaemia, the site of the coronary occlusion, the presence or not of a spasm, the compensation by the collateral flux and eventually the effects of a treatment by fibrinolytic drugs.
The topographic diagnoses of Kent's bundles obtained from vectorcardiograms with maximum preexcitation in 33 patients (dynamic VCH) were compared with those obtained using Franck's new algorithm. Only three cases disagreed, and the three anteroseptal topographies were identified a posteriori. This simple method therefore shows very satisfactory sensitivity (82%) and provides worthwhile orientation for later investigations.
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