A heat resistant micro heater consisting of a Pt thin film and a diaphragm was developed for automotive sensors and its reliability was evaluated from the mechanical and thermal points of view. The dominant failure modes for instant overheating and longtime heating were found to be de-lamination of the Pt film and electromigration of Pt, respectively. The life time was estimated to be over 10 years when the average heater temperature was 400°C (the peak temperature was over 600°C). As automotive sensors utilized this micro heater, the developed air flow meter and air quality sensor are described with features and evaluation methods unique to these sensors.
This paper reports the case of a 76-year-old man in whom atrial flutter with varying atrioventricular block and intermittent right bundle-branch block was found. This is the first report on tachycardia-dependent right bundle-branch block associated with supernormal conduction in a case of atrial flutter. When an impulse is conducted to the ventricles beyond 0.72 s after a QRS complex of right bundle-branch block configuration, the impulse falls after the abnormally long effective refractor period of the right bundle branch and passes through the right bundle branch. When the conducted impulse occurs within 0.72 s after a QRS complex of right bundle-branch block configuration, the impulse usually falls in the refractory period and is blocked in the right bundle branch; however, only when the impulse occurs 0.48 or 0.49 s after that does it fall in the supernormal period and passes through the right bundle branch. The findings in the present report strengthen our previous suggestion that the presence of supernormal conduction plays an important role in the initiation of reentrant ventricular tachycardia.
Electrocardiograms were taken from a 44-year-old man with irregular ventricular parasystole in whom pure parasystolic cycles without any intervening nonectopic QRS complexes were found. When a sinus impulse fell late in the parasystolic cycle, it hastened occurrence of the next parasystolic discharge. This suggested that type I second degree entrance block occurred in the re-entrant pathway containing the parasystolic focus. When a sinus impulse fell early in the parasystolic cycle, it delayed occurrence of the next parasystolic discharge. This suggested that electrotonic modulation occurred in the parasystolic focus. As a result, the difference in length between the short form and the long form of the parasystolic cycle became markedly great. When the length of two adjacent sinus cycles ranged between the short and the long parasystolic cycle, manifest parasystolic QRS complexes disappeared for a long time. In true ventricular parasystole with pure ectopic cycles, such long disappearance has never been reported before.
The effects of imipramine on the Na+ current of guinea-pig ventricular myocytes were examined by the whole-cell clamp method. Imipramine inhibited the Na+ current with a dissociation constant value of 25 microM at a -130 mV holding potential. At 1 microM, imipramine caused a negative shift of the channel availability curve by 4.0 +/- 1.03 mV with its steepness unaffected. The inactivation time constants were not changed by 30 microM imipramine. Paired pulse experiments revealed that imipramine binds to the inactivated Na+ channels with time constants of 3.7 +/- 0.27 sec at -65 mV and 2.4 +/- 0.58 sec at -20 mV, and that it dissociates from the channels with time constants of 5.9 +/- 1.05 sec at -90 mV and 2.0 +/- 0.87 sec at -130 mV. From these paired pulse experiments, the dissociation constant for the interactions between imipramine and inactivated channels was calculated to be 0.67 microM, a value within its therapeutic plasma concentration. These slow interactions of imipramine with inactivated Na+ channels resulted in a slow onset of the frequency-dependent extrablock in the effects of imipramine on the Na+ current. Consequently, the imipramine-induced extrablock sufficient to terminate re-entrant tachyarrhythmias would not develop shortly after their initiation. Short depolarizations of 1- to 3-msec duration sustained appreciable extra blockage when a high concentration of 10 microM imipramine was used, or they were repeatedly applied at a high frequency. However, access of imipramine to the open channels seems to play a minor role in the drug-channel interactions.
