Atrioventricular Node Ablation for Optimization of Pacemaker Treatment in Hypertrophic Obstructive Cardiomyopathy

Dual chamber pacing is a new indication for the treatment of drug resistant hypertrophic obstructive cardiontyopathy (HOCM) in patients with normal atrioventricular (AV) conduction. In sinus rhythm, the efficacy of the treatment is mainly related to the ability to bypass the normal AV conduction system in order to obtain a complete and permanent right ventricular (RV) capture. This is achieved by programming short AV delays. On the other hand, patients with HOCM frequently have co-existing left ventricular diastolic dysfunction, and the atrial contribution to left ventricular filling is critical. The lack of improvement, rarely encountered, is probably due to incomplete RV capture andlor to the deleterious effect of short AV delay. Instrumental AV node prolongation may he indicated in this situation. This procedure should be undertaken when previous drug-induced AV prolongation has failed. In theory, AV node modulation (i.e., creating a I ± AV block) seems ideal. However, this technique remains difficult, with disappointing chronic results. Most authors hence perform "conventional" AV node ablation. Particular attention is taken in order to perform a proximal node ablation, resulting in a complete AV block with narrow QRS escape rhythm. The reported incidence of AV node prolongation ranges from 7.5%-37.5%. The efficacy of the procedure on symptoms is explained by improved left ventricular filling and/or a further reduction in the systolic gradient evoked by complete RV capture. Another indication for AV node ablation in HOCM is the occurrence of atrial fibrillation, in order to restore adequate and permanent RV capture .     

Pulmonary aspiration of gastric contents after a priming dose of vecuronium

A case is presented of a 16-year-old girl with ectodermal dysplasia for whom dental surgery under general anaesthesia was planned. Following a priming dose of vecuronium, and immediately after injection of sodium thiopentone (5 mg·kg⁻¹) pulmonary aspiration of gastric contents occurred. It is hypothesized that, because of the rapid speed of onset of neuromuscular blocking agents on the laryngeal muscles, that partial laryngeal paralysis was present at the time of induction of anaesthesia and that this was responsible in part for the episode of pulmonary aspiration.     

Modification by Nickel of Instrumental Thermoregulatory Behavior in Rats1

Modification by Nickel of Instrumental Thermoregulatory Behaviorin Rats. WATANABE, C, WEISS, B., COX, C, AND ZIRIAX, J. (1990).Fundam. Appl. Toxicol. 14, 578–588. The effects of NiCl₂on the colonic temperature and thermoregulatory behavior (TRB)of rats were examined. TRB was evaluated in an instrumental(operant) setting in which rats were required to press a leverto obtain convectional heat (SEEK) or to avoid heat (ESCAPE).Orthogonal polynomial regression was used to describe the responsepatterns in both the SEEK and ESCAPE situations. Two milligramsper kilogram of Ni (ip) caused rapid, transient hypothermiaat an ambient temperature of 21°C. When given access toheat reinforcement, rats responded for heat at a lower rateimmediately after 2 or 5 mg/kg of Ni (up to 5–15 min)than after saline. Subsequently, response rates rose 30 minor more after Ni injection. A converse pattern was found withthe heat escape situation. These observations, confirmed bytwo contrasting procedures, indicate that the changes were thermoregulatoryin nature and cannot be explained by nonspecific sup-pressiveor excitatory effects of Ni. They further suggest that Ni-inducedhypothermia results from an altered body temperature set point.The subsequent reversal in behavior probably arises from a directaction of Ni on autonomic effector mechanisms. The origin andbiological significance of these findings require further investigation.Physical requirements and response topography are discussedas critical variables in the interpretation of experiments requiringsimilar responses under different ambient temperatures.     

Modification of Lead Distribution by Diethyldithiocarbamate

Modification of Lead Distribution by Diethyldithiocarbamate.WEISS, B., CORY-SLECHTA, D. A., AND COX, C. (1990). Fundam.Appl. Toxicol. 15, 791–799. Many reports indicate thatdithiocarbamates such as diethyldithiocarbamate (DDC), administeredin conjunction with exposure to various metals, can elevatethe brain levels of such metals at the same time that they promoteexcretion from other sites. To more clearly define the effectsof DDC on lead (Pb) distribution after prolonged exposure torelatively low levels, male Long-Evans rats were provided withdrinking water containing 0, 50, or 500 ppm Pb acetate. Duringthe 12-week experimental period, DDC was administered by ipinjection twice weekly in a dose of 100 mg/kg. Every 3–4weeks, urine and blood samples were taken 24 hr before and aftera scheduled DDC injection. DDC administration exerted no discernibleeffect on bone Pb levels and showed only an interaction withPb dose, but not independent effects on kidney levels. Bothliver and brain Pb levels attained much higher levels in theDDC-treated rats than in animals exposed to Pb alone. The sequentialmeasures of Pb in blood and urine and of -aminolevulinic acidrevealed complex patterns of change over time. One possibleexplanation, at least for the elevated levels of Pb in brain,is the lipophilic character of the Pb-DDC complex, which facilitatesentry into the central nervous system; it may also explain theelevated levels in liver. This property, common to many chelators,suggests their use in model systems to study the neurotoxicproperties of metals.     

Mode of Onset of Malignant Ventricular Arrhythmias in Idiopathic Ventricular Fibrillation

Mode of Onset of Idiopathic VF. Introduction : The mode of onset of malignant ventricular arrhythmias (ventricular tachycardia [VT] or ventricular fibrillation [VF] has been well described in patients with organic heart disease and in patients with the long QT syndromes. Less is known about the mode of onset of VF in patients with out-of-hospital VF who have no evidence of organic heart disease or identifiable etiology.
Methods and Results : We reviewed the ECGs of all our patients with Idiopathic VF. Documentation of the onset of spontaneous arrhythmias was available for 22 VK episodes in 9 patients (6 men and 3 women; age 41 ± 16 years). In all instances, spontaneous VF followed a rapid polymorphic VT, which was initiated by premature ventricular complexes (PVCs) with very short coupling intervals. The PVC initiating VF had a coupling interval of 302 ± 52 msec and a prematurity index of 0.4 ± 0.07. These PVCs occurred within 40 msec of the peak of the preceding T wave. Pause-dependent arrhythmias were never observed.
Concltision : Cardiac arrest among patients with idiopathic VF has a very distinctive mode of onset. Documentation of a polymorphic VT that is not pause dependent is of diagnostic value.     

Pneumatosis Coli Associated with Sigmoid Volvulus and Colonoscopy

A case of interstitial emphysema involving the mesentery and serosa of the sigmoid colon after volvulus reduced by colonoscopy is presented. The case is reported as a form of pneumatosis intestinalis although it does not conform to the classical clinicopathologic picture of pneumatosis cystoides intestinalis. The infrequent occurrence of this condition in association with volvulus and/or colonoscopy is discussed.