No abstract

The object was to study the relationships between calf muscle size and strength in 85 patients an average of 3.1 years after repair of achilles tendon rupture. The isokinetic calf muscle strength results were excellent or good for 73% of the patients, whereas calf muscle size was normal in only 30%. The average plantar flexion peak torque per unit muscle cross-sectional area was higher on the injured side than on the uninjured side. The average calf muscle cross-sectional area deficit was 15+/-9% (p<0.001) of that on the unaffected side, while the average plantar flexion peak torque deficit was speed-dependent, being 9+/-18%, 10+/-18 and 2+/-13% of that on the unaffected side at 30, 90, and 240 degrees/sec (p<0.001). The correlation between cross-sectional area and peak torque varied in the range 0.52-0.61 at 30, 90 and 240 degrees/sec (p<0.001).

This study was performed to evaluate the accuracy of magnetocardiography in non-invasive localization of the ventricular pre-excitation site in patients suffering from the Wolff-Parkinson-White (WPW) syndrome. Twelve WPW patients were studied, in whom the pre-excitation caused serious supraventricular arrhythmias refractory to drug therapy. Magnetocardiographic measurements were performed in a magnetically shielded room, and non-invasive localization was computed from preprocessed magnetic signals using a current dipole source in a realistically shaped digital torso. All patients underwent intra-operative multicatheter mapping and subsequent dissection of the accessory atrioventricular connection. The intra-operative localization results were marked on magnetic resonance images of the heart, where magnetocardiographic results were also superimposed to allow comparison. The average of the three-dimensional differences between the magnetocardiographic and the invasive results was 2.1 +/- 0.9 cm. In all cases, the computed localization result was in the same or adjacent anatomical region as the intra-operative result. The present results show that the magnetocardiographic method using a realistic torso model is capable of localizing pre-excitation sites with sufficient accuracy to provide extra information so that non-pharmacological therapeutic interventions can be applied.

In our magnetocardiographic (MCG) localisation studies, two modelling approaches have been applied: (a) modelling the sources with dipole and quadrupole moments in a general multipole expansion and using a homogeneous, semi-infinite volume conductor, and (b) using a single current dipole source in a homogeneous, realistically shaped torso. Both approaches have been successfully applied in localising the premature ventricular excitation site in patients suffering from the Wolff-Parkinson-White syndrome. In addition, we have participated in developing a model of propagation of electrical activation in the ventricles. Anisotropic conductivity properties and spiral arrangement of myocardial fibres are included in the model.