The automatic implantable cardioverter-defibrillator: effect of patch polarity on defibrillation threshold

An automatic implantable cardioverter-defibrillator (AICD) was implanted in 40 patients with sudden cardiac arrest (n = 29), sustained monomorphic ventricular tachycardia (n = 10) or recurrent syncope (n = 1) who were unsuitable for direct ablative surgery or had had unsuccessful medical therapy. The effect of patch electrode polarity on the defibrillation threshold was prospectively evaluated. Two large epicardial patches were used. Initial polarity was selected at random. Ventricular fibrillation was induced by direct current and a preestablished defibrillation protocol employed to assess the minimal energy that would reproducibly defibrillate the heart. Nineteen patients had a lower defibrillation threshold with the inferior left ventricular patch as an anode and nine patients had a lower defibrillation threshold with this patch as a cathode. In general, the defibrillation threshold was lower when this patch was used as an anode than when it was used as a cathode (18 +/- 10 versus 22.6 +/- 12.2 J; p less than 0.01). No preoperative variable predicted optimal polarity. Therefore, the effect of patch polarity on defibrillation threshold should be assessed in each patient at the time of AICD implantation so that the safety margin for satisfactory device function can be maximized.     

The haemochromatosis gene: A co-factor for chronic liver diseases?

There is increasing evidence that hepatotoxins, such as alcohol and the hepatitis viruses, act as co-factors in causing hepatic fibrosis and cirrhosis. For example, alcohol aggravates the hepatic damage produced by iron in hereditary haemochromatosis. We present evidence that the reverse is also true, that is, that iron loading of mild to moderate degree due to heterozygosity or homozygosity for the haemochromatosis genetic mutations acts as a significant hepatotoxin aggravating hepatic damage from other causes of liver disease. These include non-alcoholic steatohepatitis, chronic hepatitis C, porphyria cutanea tarda and possibly primary liver cell cancer. However, any additional hepatotoxic effect is due to the hepatic iron concentration and not the mutations in the haemochromatosis genes.     

Cardiac effects of lead in drinking water of rats.

1. There is no known cause for the increased mortality due to ischaemic heart disease in soft water areas. Since the lead concentration of soft water is elevated in houses with lead plumbing, studies have been carried out to determine the effects of lead on the heart of rats. 2. Rats were given drinking water containing lead for 1 year at concentrations similar to those found previously in Glasgow, which has a soft water supply. 3. There was increasing deposition of lead in the heart and a fall in the cardiac levels of the enzymes ferrochelatase and delta-aminolaevulinic acid dehydratase. These changes are maximal after 6 months, when there were marked electron-microscopic changes in the myocardium and myocardial mitochondria. 4. Further studies are needed to determine whether lead is a cause of the increased mortality from ischaemic heart disease in soft water areas.     

The effect of steering on the physiological energy cost of wheelchair propulsion

Previous studies of the energy cost of wheelchair propulsion have used ergometers or tracks requiring little steering. We have measured minute ventilation (VE), oxygen consumption (VO2), carbon dioxide output (VCO2) and heart rate (HR) during exercise in a two arm, hand-rim propulsion wheelchair on a treadmill, and on three tracks of increasing tortuosity in eight able-bodied subjects. During propulsion at 0.6 m/sec, VE, VO2, and VCO2 were significantly greater on the track with the maximal steering component than on that with the minimal steering component, or on the treadmill with no steering component. Heart rate was significantly higher on the maximal compared to minimal steering component track. Exercise at speeds varying from 0.2 to 1.0 m/sec showed that VO2 and VCO2 were significantly higher on the medium steering component track than on the treadmill at speeds of 0.6 m/sec and above. We conclude that the effort of steering contributes significantly to the energy cost of wheelchair propulsion particularly at higher speeds.     

Lipoprotein concentrations in untreated adult onset diabetes mellitus and the relationship of the fasting plasma triglyceride concentration to insulin secretion.

Plasma lipoprotein concentrations in 64 untreated adult onset diabetics were compared to the lipoprotein levels found in non diabetics. No significant difference was found. The relationship of the fasting plasma triglyceride concentration to the plasma immunoreaction insulin response to 50 g glucose orally was investigated. Using correlation analysis a significant and insulin response in the non diabetics but not in the diabetics.     

P21Therapeutic Efficacy of Plasmapheresis for the Treatment of Refractory Pruritis of Primary Billiary Cirrhosis: 2 Case Reports.

Primary billiary cirrhosis (PBC), a chronic cholestatic disease of presumed autoimmune aetiology, is characterised by progressive intrahepatic bile duct destruction, liver cirrhosis, failure, and death, unless treated by liver transplantation. Distressing pruritis (skin itch), fatigue and metabolic bone diseases frequently complicate this disease, significantly reducing quality of life. The pathogenesis of pruritis remains uncertain. Some unknown pruritogen(s) produced by the liver have been implicated which accumulate in the plasma as a result of chronic cholestasis. Recent evidence also suggests a central mechanism, with increased neurotransmission/neuromodulation mediated by endogenous opioid agonists. Therapeutic interventions include unabsorbable oral resins, urso-deoxycholeic acid, opiate antagonists and rifampicin. More experimental therapies include: partial diversion of bile; charcoal haemoperfusion; UVA; plasmapheresis and albumin-based dialysis (for patients with renal impairment). We used plasma exchange for the treatment of intractable pruritis in two patients with primary billiary cirrhosis. Both were females between ages of 50–60 years, refractory to all medical treatments and severely disabled by intractable pruritis and fatigue. In the first patient, weekly to fortnightly plasmapheresis considerably reduced the intensity of itch and stabilized her condition until her liver transplant. The second patient was treated for a relapse of PBC following her liver transplant. She significantly improved with more than 50% reduction in the intensity of her generalized itch with healing of excoriations, and was able to sleep for 4 h undisturbed after only one procedure. We suggest that plasmapheresis may be helpful for the pruritis of chronic cholestasis refractory to medical management. It could also be considered for the initial treatment of selected patients in combination with other therapies.     

Effect of Variation in Diacylglycerol Kinase Eta (DGKH) Gene on Brain Function in a Cohort at Familial Risk of Bipolar Disorder

Several lines of evidence indicate that the diacylglycerol kinase eta (DGKH) gene is implicated in the etiology of bipolar disorder (BD). However, the functional neural mechanisms of DGKH''s risk association remain unknown. Therefore, we examined the effects of three haplotype-tagging risk variants in DGKH (single nucleotide polymorphisms rs9315885, rs1012053, and rs1170191) on brain activation using a verbal fluency functional magnetic resonance imaging task. The subject groups consisted of young individuals at high familial risk of BD (n=81) and a comparison group of healthy controls (n=75). Individuals were grouped based on risk haplotypes described in previous studies. There was a significant risk haplotype*group interaction in the left medial frontal gyrus (BA10, involving anterior cingulate BA32), left precuneus, and right parahippocampal gyrus. All regions demonstrated greater activation during the baseline condition than sentence completion. Individuals at high familial risk for BD homozygous for the DGKH risk haplotype demonstrated relatively greater activation (poor suppression) of these regions during the task vs the low-risk haplotype subjects. The reverse pattern was seen for the control subjects. These findings suggest that there are differential effects of the DGKH gene in healthy controls vs the bipolar high-risk group, which manifests as a failure to disengage default-mode regions in those at familial risk carrying the risk haplotype.