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A controversy arose some 10 years ago over the reliability of polyurethane lead insulation. On the basis of one of the longest standing and largest databanks worldwide, the authors compare the cumulative survival of several thousand polyurethane, standard silastic, and high-performance silastic electrodes as it pertains to the failure criterion described as insulation degradation. With the possible exception of the Medtronic 6972 (Medtronic, Inc.) electrode, polyurethane electrodes have a 100% reliability at 84 months, which is similar to silastic electrodes.

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In a previous work we showed an alteration of erythrocyte filtration ability in patients with Alzheimer's disease according to their age and illness duration. This study has for aim to find a criteria of deformability that would be constant in all Alzheimer patients and would show a modification of red cell membranes. The erythrocyte filterability was studied in this present paper, in accord to Reid and Dormandy method using two values of depression (5 and 0 cm of water). These depressions correspond to the physiological values of blood pressure at the level of precapillary and capillary systems. The ratio between the result obtained at 5 cm and the result at 0 cm is constant in normal patient without organic disease and it is independent of age. At the opposite, this ratio increase very significantly in all Alzheimer patients, and this is not correlated to the initial value of filtrability. This ratio could be an index of the alteration of red cell membranes.

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Over a 17-year period (1970-1987) 75 patients, 3% of overall valvular surgery (VS) patients have been permanently paced at the time of VS (group 1), nine have been paced long after (group 2), 12 were already paced at the time of valve replacement (group 3), and 81 had a permanent pacing lead inserted during VS without further need for permanent pacing (group 4). Based on pre-, per- and post-operative clinical and electrocardiographic data we studied these four groups (GR). Aortic disease and especially calcified aortic stenosis (CAS) are the main valvular pathologies in all GR. The survival rate in GR 1 is lower than the survival rate of our overall VS PT5 due to older average ages and more severe cardiac conditions. In five patients GR 2 a myocardial pacing lead placed during VS was used long after for permanent stimulation. Patients in GR 3 were older than in other GR at the time of VS. The mortality was high in the patients operated on between 1973 and 1978 (average survived 3.5 years after pacing/2 years after VS) thus demonstrating the benefit of myocardial protection. For GR 4 the ratio of permanent lead implantation during VS was high in the late seventies (10%), it is now around 0.5%. In cases where the evolution of peroperative conduction disturbances is doubtful, it seems to us simpler to place a myocardial lead avoiding subsequent endocardial pacing if necessary, later, especially in patients with tricuspid disease.

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The influence of aging and the effects of treatment with dihydrogenated rye ergot alkaloid on cerebral hemodynamics and metabolism were studied in Long-Evans rats. Cerebral blood flow (CBF) was not affected by aging whereas the vascular bed and the uptake of deoxyglucose were significantly lower in aged than in young rats. 20 days after ligation of a carotid artery the blood flow on the same side of the brain, the vascular bed and the uptake of deoxyglucose were significantly lowered in aged rats as opposed to young rats. The second carotid artery was ligated 1 h before the animals were sacrificed: in the corresponding cerebral hemisphere the blood flow was found to be significantly lowered in young rats and even more so in aged rats. These results show that young rats are more likely to adapt to an acute or chronic circulatory deficiency than aged rats. Dihydroergocryptine ( DHEC , 0.1 mg/kg/day for 5 days, p.o.) reduces CBF and the vascular bed in aged rats, as opposed to dihydroergotoxine ( DHET , 5 X 0.1 mg/kg/day p.o.). The uptake of deoxyglucose was not influenced by the treatments. After ligation of the carotid arteries, treatment with DHEC and DHET induced an increase in CBF without any change in the vascular bed and, in the case of DHEC only, there was a significant increase in the uptake of deoxyglucose in the cerebral hemisphere submitted to acute circulatory deficiency. DHEC and DHET thus exerted significant effects on cerebral metabolism and hemodynamics in the aged rats after repeated oral treatment.

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In Long Evans rats, the vertebral arteries supply only the brain stem. Simultaneous application of clamps to both carotid arteries results in a considerable fall of cerebral blood flow and eventually death. If an interval of about 4 days is allowed between the clamping of the 2 carotids, redistribution of blood flow takes place. Owing to this mechanism, 50% of the rats survive with a satisfactory restoration of cerebral blood flow.

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Simultaneous ligature of both carotid arteries in Long Evans rats results in death for all animals. 50% of the animals survive if the ligatures are separated by a four-day interval. Studies of variations in cerebral blood flow according to the time interval between the two ligatures show that alternative vascularization develops and that the balance between both hemibrains is restored. After giving L-dopa3H to animals with ligature of both carotids, increased synthesis of cerebral dopamine 3H and norepinephrine 3H can be demonstrated. When animals are given extracts of Ginkgo biloba leaves prior to carotid ligatures, survival rate is improved and dopamine synthesis increased, without marked changes in cerebral blood flow. This is related to increased brain cell activity in spite of hypoxia due to carotid ligature.

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Transient ischemia results in changes in the cerebral blood flow at the level of microinfarcts, enzymatic and metabolic changes and the development of a cerebral edema; all these disorders regress in the week following ischemia. Besides, the observed functional disorders disappear as the cerebral edema regresses. The brain functional activity is protected by the use of treatments which reduce the development of the cerebral edema and/or a quicker regression of the edema.

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Analysis of the long-term survival of pacemaker carriers showed a parallelism between two curves: that of the survival in patients treated with a pacemaker as from the second month, and that of a control group with the same age and physical structure. Treatment in the first few years was made problematical by defects in surgical technique: while in 17% of reoperations, the reason was straightforward substitution of the pacemaker owing to wear on the battery, 83% were the consequences of complications. Of these, 23% consisted of shifts in the intracavitary probe, electrode failures, or increase in the threshold. The frequency of infections due to implantation or reoperation was 7,4%, in certain cases with fatal outcome. Bearing in mind that mortality from Adam-Stokes disease was 50% prior to the introduction of pacemakers, it can be maintained that this therapy represents a considerable step forward in cardiology. Mortality was 27% in all patients submitted to implantation.

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A comparison between the life expectancy of patients with pacemakers and that of a control population of similar structure shows a parallel course, although originally, after a postoperative phase of 2 months, the mortality rate of the patients with pacemakers was higher. Today the results are considerably better. Implantation of pacemakers is one of the greatest cardiological advances in the last 10 years for the effective treatment and prevention of cardiac arrest in atrioventricular block. The significance of this type of therapy becomes understandable if the fact that the mortality of Adams-Stokes attacks used to be about 50% is taken into consideration. In France, about 5000 persons each year have Adams-Stokes attacks.

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