Le syndrome d’Andersen : une forme particulière de paralysie périodique avec dysrythmie cardiaque

Andersen syndrome includes a clinical triad with periodic paralysis, cardiac arrhythmia and dysmorphic features most often mild but relevant. It is a potassium channelopathy due to mutation of KCJN2 gene coding for Kir 2.1 protein. We report a familial case with mutation R218W of Kir 2.1 and discuss the main phenotypic and genetic aspects of Andersen syndrome. Muscle manifestations are essentially a periodic paralysis most often of hypokaliemic type. Muscle biopsy reveals tubular aggregates but can be normal as it is shown in the same patient in our kindred. Our proband complained of paralytic attacks since childhood and at adult age she demonstrated a mild permanent deficit of pelvic girdle muscles as it has been described in other types of periodic paralysis after a long duration course. Cardiac manifestations may include in a variable manner a long QT syndrome, premature ventricular contractions, complex ventricular ectopy, polymorphic or bidirectional ventricular tachycardia. Imipramine had a positive effect on arrhythmia in our case. Dysmorphic features are often mild and have to be cautiously looked for as a clue to the diagnosis of Andersen syndrome. They can be easily overlooked if not systematically looked for. Clinical expressivity is variable including in the same family. In our observation, the daughter showed a complete triad, early expressed, which allowed the diagnosis. Her father was late diagnosed on ventricular dysrhytmia but without muscle manifestations and dysmorphic features. Since KCJN2 gene mutation identification, locus heterogeneity of Andersen syndrome was shown. Andersen syndrome kindreds without mutations in KCNJ2 were clinically indistinguishable from KCNJ2-associated subjects. KCNJ2 gene encodes the inward rectifier K+ channel Kir2.1 which plays an important role in maintaining membrane potential and during the terminal phase of cardiac action potential repolarization. Several studies showed a dominant negative effect of the mutation on Kir 2.1 channel function.

Cochlear implantation in a pacemaker patient

The authors present their experience with cochlear implantation in a 22-year-old patient who had a cardiac pacemaker because of complete atrioventricular block. The question of compatibility between the cochlear implant (multichannel Digisonic DX10AE) and the pacemaker (Biotronik Nanos-01AE) was raised. After consulting the two manufacturers regarding the risk of electrical interference, the authors decided to program the pacemaker in a locked mode (VOO) and then perform cochlear implantation. When the cochlear implant was switched on for the first time, electrocardiograms were obtained to ensure that the two devices were compatible. Absolutely no interference was detected. After a 3-year follow-up, cochlear implant performance remains excellent.

[Left ventricular involvement in mucoviscidosis after 2 years of age]

BACKGROUND

The cardiac involvement in cystic fibrosis includes the rare cardiomyopathy seen in infants and changes in left ventricular performance in older children.

POPULATION AND METHODS

67 patients, 6 to 34 months-old (mean: 16.7), 37 male and 30 female, with cystic fibrosis, were studied. Their Shwachman score was < 70. None showed any clinical manifestations of left ventricular insufficiency, but 6 patients had right ventricular insufficiency. Echocardiography was performed on 58 patients; it showed dilation of the right ventricle in 32 of them. Left ventricular perfusion was studied with thallium 201 tomoscintigraphy and left ventricular ejection fraction with 99mTc ventriculography.

RESULTS

The left ventricular ejection fraction was < 45% in 17 patients and scintigraphy showed hypofixation in 6 of them. In contrast, only 4 of the 50 patients with left ventricular ejection fraction > 45% had thallium hypofixation.

CONCLUSIONS

Resting perfusion abnormalities are more frequent in patients with a low left ventricular ejection fraction. These perfusion abnormalities suggest that myocardial fibrosis complicates the advanced stages of cystic fibrosis.

[New developments of antiplatelet drugs]

A better knowledge of platelet activation mechanisms has made it possible to develop antiplatelet agents that are capable of inhibiting primary haemostasis at very precise levels. Many of these agents block the synthesis or receptor of an hemostasis I agonist. Thus, the thromboxane A2 receptor can be blocked, or its synthesis can be interrupted, by thromboxane synthetase inhibitors, by cyclooxygenase inhibitors, or by omega 3 fatty acids which are competitive inhibitors. Inhibitors of thrombin (hirudin), PAF acether and serotonin (ketanserin) also are available. Other antiplatelet agents secreted by endothelial cells act as haemostasis I antagonists by elevating platelet cAMP or cGMP levels (prostacyclins and analogues, nitrate derivatives). Monoclonal antibodies and RGD peptides directly inhibit the glycoproteins that are responsible for platelet adhesion or aggregation, but their users are faced with problems of cost and route of administration. Of all these new antiplatelet agents, only ticlopidine, which has an imperfectly known mode of action, has proved effective in multiple situations, but its use is limited by its side-effects.

Efficacy and safety of intravenous and oral diltiazem for Wolff-Parkinson-White syndrome

The electrophysiologic effects and safety of diltiazem administered either intravenously or orally were studied in 14 patients with Wolff-Parkinson-White syndrome during orthodromic reentrant tachycardia and atrial fibrillation (AF). Anterograde and retrograde effective refractory periods of the accessory pathway did not change significantly from baseline during either i.v. or oral administration. Administration by either route prevented induction of sustained reentrant tachycardia in 8 patients. In 6 patients, the reentrant tachycardia was either nonsustained (2 patients) or sustained at much slower rates than the baseline rates (mean +/- standard deviation, baseline, 290 +/- 41 ms; i.v., 355 +/- 40 ms [p less than 0.001]; and oral, 377 +/- 33 ms [p less than 0.001]). In these patients anterograde atrioventricular conduction was prolonged significantly from the mean baseline value of 163 +/- 36 ms to 212 +/- 35 ms with i.v. administration (p less than 0.005) and 225 +/- 33 ms with oral administration (p less than 0.005). Retrograde conduction via the accessory pathway did not change significantly after administration of diltiazem. The shortest preexcited RR intervals during AF were significantly reduced during i.v. but not during oral administration: control, 327 +/- 47 ms; i.v., 270 +/- 28 ms (p less than 0.001); and oral, 323 +/- 44 ms (difference not significant). In 5 patients AF was sustained for a mean of 20 minutes after i.v. and for 12 minutes after oral administration (p less than 0.20), compared with a baseline mean value of 0.83 minute.(ABSTRACT TRUNCATED AT 250 WORDS)

Alternate ventriculo-atrial Wenckebach conduction during ventricular tachycardia

Although pacing-induced ventriculo-atrial (VA) Wenckebach conduction has been previously described, the occurrence of this phenomenon during ventricular tachycardia has received little attention. The latter is defined as 2:1 VA block in which the conducted beats show progressive lengthening of VA conduction until the sequence is terminated by two or three blocked ventricular beats. This phenomenon was observed in a 16-year-old boy who underwent electrophysiologic study for ventricular tachycardia as a late complication of surgical correction of tetralogy of Fallot. During pacing-induced ventricular tachycardia with a morphology similar to that of the spontaneous tachycardia, 8:4 alternating VA block was observed. This sequence suggested that the AV node was the site of block, the 2:1 block being located at the upper level, and the VA Wenckebach block at the lower level. Alternate VA Wenckebach conduction appears as a possible cause of variation in atrial depolarization intervals during ventricular tachycardias with short cycle lengths.

Bepridil for recurrent sustained ventricular tachycardias: assessment using electrophysiologic testing

Bepridil was found to possess electrophysiologic properties common to class I and IV antiarrhythmic agents. Intravenous and oral bepridil were evaluated using serial electrophysiologic studies in a selected group of 9 patients with recurrent sustained ventricular tachycardia (VT) unresponsive to usual therapy, including amiodarone therapy in 15 patients. Intravenous bepridil treatment terminated sustained, well tolerated, pacing-induced VT in 3 of 6 patients and prevented the initiation of VT in 2 of these and in a patient in whom the drug failed to restore sinus rhythm. Oral bepridil was administered at a loading dose of 800 mg on day 1, and 500 to 600 mg the following days, and programmed electrical stimulation was repeated 2 to 6 days after initial study. Oral bepridil therapy prevented VT initiation in 6 patients (66%). The tachycardia cycle length was prolonged (30 to 105 ms) in 2 patients in whom VT remained inducible. In 1 patient the tachycardia cycle length significantly shortened after bepridil and prompt cardioversion was required. Five of the 6 patients with successful results underwent long-term oral treatment with bepridil. VT recurred in 1 patient during the hospitalization period and an adverse effect (paralytic ileus) in another patient required drug discontinuation. Three patients remain symptom-free over a follow-up of 4 to 13 months. These data suggest that bepridil may be useful in patients with recurrent, sustained VT.