Clinical Experience with Orthocor II Antitachycardia Pacing System for Recurrent Tachyarrhythmia Termination

Between June 1986 and December 1988, eight patients were treated with an Orthocor II 284 A antitachycardia pacemaker (Cordis Corp., Miami, FL, USA) forsupraventricular tachycardia (SVT) and ventricular tachycardia (VT) termination. Four patients had intra-AV nodal reentrant tachycardias; 1 patient had AV reentrant tachycardia with an atrio-nodal accessory bypass tract; 2 patients had AV reentrant tachycardias with concealed Kent bundle, and 1 patient had ventricular tachycardia. All patients had been treated with three or more drugs and were considered to be drug refractory. The programmed antitachycardia mechanism used for patients with SVT were: automatic overdrive in five patients and burst scanning in two patients. In the patient with VT, a critically timed double extrastimulus with fixed coupling interval was programmed. Follow-up ranged from 2 to 30 months. The pacemaker proved to be effective in terminating tachycardias in all cases with SVT; in the patient with VT, the programmed antitachycardia mechanism was effective for a long time, but after an episode of sustained VT not interrupted by the pacemaker, the patient underwent automatic cardioverter/defibrillator (AICD) implantation. Additional antiarrhythmic therapy was required in 3 patients to control their maximum sinus rate, in 1 patient to reduce tachycardia episodes and to enable termination, and in 2 patients to prevent spontaneous atrial fibrillation. It is concluded that Orthocor II is a flexible and versatile antitachycardia pacemaker providing a safe and effective control of recurrent tachycardia in selected patients.     

DIFFERENT AFFINITY OF CORTICAL GHB BINDING SITES IN SARDINIAN ALCOHOL-PREFERRING (sP) AND-NON PREFERRING (sNP) RATS

Specific gamma-hydroxybutyric acid (GHB) binding sites in corticalmembranes of selectively bred alcohol-preferring sP and alcohol-nonpreferring sNP rats were compared using [2,3³H]GHB ligand. ThesP rat line showed an increased affinity (-40% lower K_d) ofboth the high- and low-affinity sites in comparison with thesNP line. No significant difference in GHB receptor density(B_max) was detected between the two rat lines. The results raisethe possibility that differences in GHB binding sites may playa role in the genetic predisposition to ethanol preference inour rat line.     

Venous Obstruction in Permanent Pacemaker Patients: An Isotopic Study

Isotope venography was used to study the venous circulation proximal to the superior vena cava in two groups of pacemaker patients, one with a single endocavitary electrode and the other with multiple pacing catheters. A control group of patients without pacemakers was also studied. Numerous abnormalities were found, especially in the group with multiple electrodes. These findings suggest that venous obstruction is a common complication of endocardial pacing.     

Right Ventricular Tachycardia with Left Bundle Branch Block and Inferior Axis Morphology: Clinical and Arrhythmological Characteristics in 15 Patients

Fifteen patients (mean age 30) presenting with right ventricular tachycardia (VT) of the outflow tract type (left bundle branch block with inferior axis morphology), in the absence of obvious organic heart disease, were studied. Seven patients had palpitations, one presyncope and seven were asymptomatic. The echo and/or angiographic findings were normal in 11 patients (73%), suggesting arrhythmogenic right ventricular dysplasia (ARVD) in three (20%) and dubious in one (7%). The VT was sustained in three patients (20%), nonsustained (11 +/- 6 beats) in twelve (80%), inducible during exercise in two out of 15 patients (13%) and with ventricular stimulation in one out of eight (12.5%). Four patients were treated with sotalol, three with Class IC drugs and one with amiodarone. At follow-up of 36 +/- 30 months, only three patients had VT recurrences due to drug withdrawal. In conclusion: (1) abnormal echo and/or angiographic findings suggested that ARVD was observed in a minority of the patients (22%); (2) the low inducibility of VT and the good response to sotalol suggested a possible mechanism of abnormal automaticity; and (3) at a 3-year follow-up the prognosis appeared to be good in both patients with or without echo-angiographic signs suggestive of right ventricular dysplasia.     

Primary liver cancer is of multifactorial origin: Importance of hepatitis B virus infection and dietary aflatoxin

Primary liver cancer has a variable incidence worldwide, occurring most frequently in South-East Asia and China, which indicates that environmental factors are important in its aetiology. Although hepatitis B virus and chemical agents are the major risk factors for primary liver cancer, current evidence strongly suggests that it is of multifactorial origin. Aflatoxins are thought to be important because they are common food contaminants and are potent liver carcinogens in a wide variety of animal species. Evidence for the possible interactions between aflatoxin and hepatitis B infection, and their effects on the prevalence of primary liver cancer, is obtained from animal data and epidemiological studies. The risk of developing primary liver cancer following exposure to hepatitis B infection and aflatoxin is shown to be increased and the possible molecular mechanisms involved are discussed.