Yoshihiro Satoh

Electrophysiological and Anatomical Substrates for Late Potential Recorded by Signal Averaging in Seven‐Day‐Old Myocardial Infarction in Dogs

A filtered QRS (fQRS) was recorded by signal averaging in 7‐day‐oJd myocardial infarction (MI) in dogs to detect late potential (LP). The criteria for the LP included a duration of fQRS (D) ≥ 60 msec and a voltage in the last 15 msec (VI5) ≤ 10 μV. These parameters were determined from the control data from 15 dogs without infarction (D: 45 to 60 msec and V15: 12.0 to 83.6 μV). On the seventh day of infarction, the D had increased from 53.5 ± 4.7 to 62.2 ± 9.6 msec (P < 0.05) and the V15 decreased from 38.6 ± 19.5 to 18.4 ± 16.0 μV (P < 0.01). Of 23 dogs, 14 met the LP criteria (group A) and 9 did not (group B). Sustained ventricular tachycardia (SVT) was induced in 12 group A dogs and in none of the group B dogs. The delayed epicardial activation (DEA) was recorded after the end of QRS at 5.1 ± 4.7 sites in group A dogs and 1.3 ± 1.8 sites in group B dogs (P < 0.05). The maximum value of epicardial activation time was more prolonged in group A than in group B (70.0 ± 28.3 vs 44.4 ± 9.8 msec, P < 0.01). The area of MI was more extensive in dogs with DEA than those without (24.9 ± 5.8% vs 10.3 ± 9.0% of the total left ventricular weight, P < 0.01). In 72 of 90 sites with DEA, the thickness of the surviving epicardial muscle was ≤1 mm. The sensitivity and specificity of the criteria for LP in detecting DEA were 71.4% and 55.6%, and 100% and 81.8% for predicting inducibility of SVT. It was thus concluded that LP, reflected the DEA, was identified from infarct areas of slow conduction within a reentry circuit of SVT.

An Electromyographic and Clinical Study of the Influences of Experimental Prematurity on Masticatory System (I)

The purpose of this paper was to study clinical and electromyographic changes of masticatory system associated with experimental prematurity. This experiment was performed on 3 male subjects, age from 26 to 34 years old, and each possessing a natural dentition without any disorder of temporomandibular joint and masticatory muscles. To induce artificial prematurity on their natural dentition, single high occlusal inlay were placed in their lower molar. Before and after setting inlays, they were investigated electromyographically and clinically.Immediately after placing of inlay, all subjects experienced bruxism such as clenching and grinding, either consciously or even inconsciously. After three days of experimental period, inlays were removed and all of them showed glittered attritional surface. Electromyographically activity of masseter and temporal muscles were inhibited during chewing (peanut), particularly on experimental side. It seems that the musclar inhibition may be a protective reaction to protect the prematufy tooth from excessive forces.