Comparison of Clinical Benefits and Outcome in Patients with Programmable and Nonprogrammable Implantable Cardioverter Defibrillators

Technological advances in implantable cardioverter defibrillators (ICDs) have provided a variety of programmable parameters and antitachycardia therapies whose utility and impact on clinical outcome is presently unknown. ICDs have capabilities for cardioversion defibrillation alone (first generation ICDs), or in conjunction with demand ventricular pacing (second generation ICDs), or with demand pacing and antitachycardia pacing (third generation ICDs). We examined the pattern of antitachycardia therapy use and long-term survival in 110 patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Group I included 62 patients with nonprogrammable first generation ICDs that delivered committed shock therapy after ventricular tachyarrhythmia detection based on electrogram rate and/or morphology was satisfied. Group II included 48 patients with multiprogrammable ICDs (including second and third generation ICDs) that had programmable tachyarrhythmia detection based on rate and tachycardia confirmation prior to delivery of electrical treatment with either programmable shocks and/or, as in the third generation ICDs, antitachycardia pacing. Incidence and patterns of antitachycardia therapy use and long-term survival were compared in the two groups. The incidence of appropriate shocks in patients who completed 1 year of follow-up was significantly greater in group I (30 of 43 patients = 70% vs 11 of 26 patients = 42%; P less than 0.05). In the total follow-up period, a significantly larger proportion of group I patients as compared to group II patients used the shock therapies (46 of 62 patients = 74% vs 25 of 48 patients = 52%; P less than 0.01), with the majority doing so within the first year of implantation (96% and 92%, respectively). Although the frequency of antitachycardia therapy activation was similar, the number of shocks delivered per patient was lower in group II, particularly in the initial 3 months of follow-up (P = 0.06). No clinical variable aided in identifying users from nonusers of antitachycardia therapy. Arrhythmic mortality was virtually eliminated in both groups. Two-year actuarial cardiac survival in the two groups was similar (group I = 78% vs group II = 84%; P greater than 0.2). Survival from cardiac mortality in users and nonusers of antitachycardia therapies was also similar in both groups (P greater than 0.2) and in the total patient group (P greater than 0.2). We conclude that programmable ICDs continue to confer advantages in prevention of sudden death that were observed with nonprogrammable ICDs and can be expected to improve patient tolerance and physician acceptance of device therapy for VT/VF.     

Fibrin(ogen) degradation product peptide 6A increases femoral artery blood flow in dogs

To determine the effects of peptide 6A (a fibrinogen-degradation product) on femoral blood flow, anaesthetized dogs were given saline or peptide 6A intravenously in random order. Bolus injection of peptide 6A (10, 20 or 50pmoles) caused a short-lasting dose-dependent decrease in femoral bed resistance and an increase in femoral blood flow. Continuous infusion of peptide 6A (50 μmoles min^-1) resulted in a sustained decrease in resistance and an increase in femoral artery blood flow (54 ± 33%), with a small, insignificant decrease in femoral artery mean pressure. Indomethacin pretreatment caused only slight attenuation of the peptide 6A-induced increase in femoral blood flow. In in vitro experiments, peptide 6A relaxed rings of femoral artery, and this effect was associated with an increase in 6-keto-PGF1α in the vascular ring supernatants and in the tissue cyclic GMP concentrations. Peptide 6A-induced relaxation was abolished by de-endothelialization, but not by treatment with indomethacin. These observations suggest that peptide 6A induces vasorelaxation largely by stimulating release of endothelium-derived relaxing factor. PGI₂ release appears to play only a minor role in the vasodilator effects of peptide 6A in the femoral bed.     

The role of the anaesthetist in chronic pain management

The role of the anaesthetist in the continuing care of patients suffering from chronic pain has been discussed. Many of the techniques, both invasive and non-invasive, which are currently available for the treatment of chronic pain have been reviewed.     

Undernutrition and Immunity: Smallpox Vaccination in Chronically Starved, Undernourished Subjects and Its Immunologic Evaluation

This study illustrates the specific immune response of chronically starved, undernourished adults after inoculation of live smallpox vaccine. It produced no adverse effect, and major vaccinial reaction was observed in all. 63% of undernourished individuals showed a fourfold or greater rise of the neutralizing antibody titre. In contrast, only 9% of normal healthy subjects could show similar response. However, the prevaccination titre was much lower in the undernourished group than in the control group, and the postvaccination titre also remained persistently lower in the former than in the latter group. Furthermore, whereas the specific humoral antibody response in the undernourished subjects was partially adequate, the development of specific cellular immunity against vaccinia was remarkably poor, indicating that smallpox vaccination in these subjects might be less effective against variola infection. This observed profound effect of chronic starvation and severe undernutrition on the immune apparatus was possibly multifactorial, protein depletion being the most important factor, as proved by the significantly low serum albumin level. The significantly low peripheral blood lymphocyte count and spectacular unresponsiveness to many antigens in these individuals suggested profound depression of the thymolymphatic system. Further, the significantly low level of neutralizing antibody in the malnourished subjects suggested that the formation of this protective antibody might necessitate the cooperation of T lymphocytes.     

The treatment of chronic back pain

Structures innervated by the dorsal primary ramus play a significant part in the genesis of chronic backache and associated leg pain. The features of this syndrome are described and compared with those in the more familiar clinical picture following intervertebral disc degeneration. However these clinical entities are seldom entirely separate and the diagnosis is often also complicated by psychosomatic factors and the consequences of previous back surgery. A technique of percutaneous facet denervation with a radiofrequency probe, although by no means successful in every case, is entirely safe and a very wothwhile procedure. It has helped many patients, who would otherwise have been disabled by pain and restricted in their activities.