X‐linked hereditary motor sensory neuropathy (type 1) presenting with a stroke‐like episode

X‐linked hereditary motor sensory neuropathy type 1 (CMTX 1) is caused by mutation in the GJB1 gene that codes for the connexin 32 protein. Central nervous system involvement with or without white matter changes on magnetic resonance imaging (MRI) has rarely been reported in this condition. We report the case of a 7‐year‐old, previously well male who presented with a stroke‐like episode that manifested as left hemiparesis and dysphasia. An initial brain MRI showed white matter signal changes affecting the corpus callosum and periventricular areas with a posterior predominance. Our patient made a complete clinical recovery in 36 hours. Clinical examination at this stage showed no evidence of a peripheral neuropathy. A repeat brain MRI 6 weeks later showed almost complete resolution of the changes seen initially. Subsequent investigations showed a Val177Ala mutation in the GJB1 gene. This mutation has so far not been described in the Caucasian population and has been only described once before. Electrophysiological studies showed a mixed demyelinating and axonal sensorimotor neuropathy in keeping with CMTX 1. Five months after the initial presentation our patient developed clinical evidence of a peripheral neuropathy in the form of absent ankle reflexes, weak dorsiflexors, and evertors of both feet.     

Phosphate Partition in the Erythrocytes of Normal Newborn Infants and Infants with Erythroblastosis Fetalis. III. P32 Uptake and Incorporation

The uptake and incorporation of P³²O₄ by the cord blood erythrocytes ofnormal and erythroblastotic infants and the erythrocytes of adults was studiedby incubating specimens in ACD at 37 C. in air. The uptake of p³² from theplasma was slower in the infants than in the adults. It was possible to demonstrate an initial "fast" phase followed by a "slow" phase in all the plasma p³²uptake experiments. The half-value time and the percentage turnover perminute indicated greater activity in the adults compared to the infants. Thebalance of movement of phosphorus was from red cells to plasma in all theexperiments. No striking differences in phosphate metabolism were demonstrated between the normal and erythroblastotic newborns, except for thelarge turnover in µM of P per minute by the red cells of the latter during thefirst 20 minutes of incubation.

Labeling of intraerythrocytic inorganic phosphorus (P_i), adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (2,3-DPG) proceeded more slowlyin the infants than in the adults. The labeling of the erythrocyte 2,3-DPG of allthe infants lagged far behind P_i and ATP whereas in the adults the r.s.a. of2,3-DPG had equalled or exceeded the r.s.a. of P_i and ATP in four hours. Itis suggested that there is decreased synthesis of phosphoglycerates by theerythrocytes of the newborn which may be due to a lower level of glyceraldehyde-3-phosphate dehydrogenase activity.

Accepted on January 11, 1962     

RESOLUTION OF HYPERGASTRINAEMIA AFTER PARATHYROIDECTOMY IN MULTIPLE ENDOCRINE NEOPLASIA SYNDROME TYPE I (MEN TYPE I)

The treatment of choice for gastric acid hypersecretion in MEN type I has now changed from total gastrectomy to the long-term administration of H2 receptor blockers or similar agents. However, the importance of parathyroidectomy for the concomitant hypercalcaemia is not fully realized. A case is reported of a subject with MEN type I, who was initially treated with parathyroidectomy and H2 receptor blockade. Following parathyroidectomy, there was a rapid fall of the markedly elevated gastrin levels to the upper limit of the normal range. During follow-up of 2.5 years, there has been no increase in serum gastrin, and the subject's gastric symptoms have resolved, despite the cessation of H2 blockade. Infusion of calcium to pre-operative levels and superimposed secretin stimulation after this period of time closely reproduced the pre-operative hypergastrinaemia. On screening, the subject's only child was found to have hypercalcaemia but normal serum gastrin levels and pituitary function; parathyroidectomy has been carried out. No abnormality of gastrin secretion has been found during follow-up. This case highlights the importance of early parathyroidectomy in this syndrome.     

Detection of Atrial Fibrillation During Sinus Tachycardia Induced by Exercise in Patients with Implantable Atrial Defibrillators

Accurate detection of atrial fibrillation (AF) is essential for appropriate operation of an implantable atrial defibrillator (IAD). However, during episodes of sinus tachycardia, distinction between AF and sinus rhythm (SR) using the "quiet interval" and "baseline crossing" analysis in the detection algorithm of the IAD may be difficult. The efficacy of this AF detection algorithm was tested in five patients implanted with an IAD (MFTRIX, Model 3000 or 3020, InControl Inc.) during treadmill exercise testing. The IADs were programmed to Monitor Mode with a wake up cycle of 1 minute for AF detection using the device nominal parameters or modified parameters, and to mark rhythms appropriate for shock delivery. A mean peak heart rate of 137 ± 26 beats/min was reached during maximum exercise, and one patient developed transient AF. Seventy-eight (75 in SR, 3 in AF) and 91 (89 in SR, 2 in AF) runs of AF detection were performed using the nominal and modified parameters, respectively. The IAD detected AF and SR accurately, except for one episode of false-positive AF detection during sinus tachycardia at the nominal settings, but inappropriate shocks were prevented by minimum RR interval criteria that limited discharge at high heart rate. These results indicate that the AF detection algorithm in the IAD may become more vulnerable to false-positive AF detection during sinus tachycardia, which were avoided by reprogramming the Quiet Interval and minimum RR interval criteria for AF detection. Exercise testing appeared useful to program optimal settings of the IAD in preparation for daily activities.     

Preimplant Atrial Defibrillation Testing with a Temporary Catheter in Sheep

Prior to implantation of an atrial defibrillator, its effectiveness should be tested in each patient. A new catheter design for temporary use with electrodes for atrial defibrillation, electrogram sensing, and pacing was tested in this study. Atrial defibrillation thresholds defined using this temporary catheter were compared to the ones defined by catheters intended for chronic use with an implantable atrial defibrillator. Atrial defibrillation threshold was determined in six sheep using both types of catheters. Each animal was subjected to studies on 2 consecutive days. On the first day, shocks were applied between two of the temporary catheters. On the following day, permanent leads were inserted and atrial defibrillation threshold was redetermined. In both cases, defibrillation electrodes were positioned in the same heart location with one electrode in the distal coronary sinus and the second electrode in the right atrium. Atrial defibrillation threshold was obtained using 10 V increments or decrements to determine the lowest shock intensity needed to defibrillate the atria. Threshold was defined as the shock intensity at which 20 shock percent success was at or between 15 % and 85%. Statistical analysis showed no significant difference (P < 0.05) between atrial defibrillation threshold energy (0.53 J vs 0.55 J), voltage (122 V vs 120 V) or current (2.2 A vs 2.6 A) measured with the temporary catheters and the permanent leads, respectively. These data indicate that temporary catheters can be used for efficacy testing prior to implant of an atrial defibrillator, and that they predict atrial defibrillation threshold adequately for chronic leads.     

Atrial Fibrillation Induction and Determination of Atrial Vulnerable Period Using Very Low Energy Synchronized Biatrial Shock in Normal Subjects and in Patients with Atrial Fibrillation

The atrial vulnerable periods (A VP)for shock induction of atrial fibrillation (AF) in humans have not been clearly defined. Furthermore, the safety and efficacy of using low energy biatrial shock delivered transvenously for AF induction are unknown. We tested the safety and efficacy of using very low energy biatrial shocks, delivered between the right atrium and the coronary sinus for AF induction and used this technique to characterize the A VP in nine controls and nine patients with AF. Thirty-volt and 60-V 3/3-ms biphasic shocks were delivered, starting from 50 ms before the atrial effective refractory period with 20-ms increments until the end of the QRS interval to determine the AVP front, AVP end, and the AVP duration. Successful AF induction could be achieved in eight (89%) of the nine controls and in nine (100%) of the nine patients with AF without any complication. In patients with AF, the AVP front started significantly earlier within the QRS complex, and the AVP duration and the AVP duration/QRS percent ratios were also significantly greater as compared to controls. Furthermore, a higher induction shock energy in patients with AF was associated with an increase in AF inducibility and significantly increased the AVP duration and A VP duration/QRS percent ratio as compared to the controls. This study demonstrated the safe and efficacy of delivering a very low energy biatrial shock during the AVP within the R wave for AF induction. The characteristics of A VP in patients with AF were significantly different from normal subjects.     

Is the Automatic Atrial Defibrillator a Promising Approach?

Automatic Atrial Defibrillator. Atrial fibrillation is a common arrhythmia, accounting for more consumption of medical resources than any other arrhythmia. The impact of the disease results from the combination of a loss of atrial contraction, and atrial control over cardiac rate. Studies in animals demonstrated the basic feasibility of atrial defibrillation using electrodes passed intravenously. Subsequent studies in patients confirmed that low-energy shocks were effective in converting atrial fibrillation and were safe if delivered synchronous to the R wave in the absence of a short preceding RR interval. Preliminary experience suggests that a small implanted device might provide beneficial therapy for patients with recurring episodes of persistent, drug-refractory, atrial fibrillation.