The cardiac manifestation of Becker muscular dystrophy is characterized by early right ventricular involvement associated or not with left ventricular impairment. Exon 49 deletion is associated with cardiac disease.
The purpose of this study was to define the history and prognosis of 12 patients (8 males, 4 females) with syncope of unknown origin (5 to 15 episodes), who developed prolonged asystole or complete AV block during the upright tilt test (UTT). The mean age (+/- SD) of the patients was 29 +/- 7.4 years, and all had normal neurological and cardiological findings on evaluation. These patients were selected from a larger group of 92 cases with positive UTT out of a total of 136 subjects who were referred for recurrence of syncope. Neither clinical nor autonomic nervous system evaluation distinguished these 12 patients from those with positive UTT. Following UTT, therapy was initiated and consisted of transdermal scopolamine in four, disopyramide in two, and beta-blockers in four patients. During follow-up (mean, 17 +/- 5.4 months), four patients had recurrences but none experienced episodes of life-threatening syncope. These patients do not show an enhanced risk of sudden death, and drug therapy seems to improve their clinical course. Only long-term follow-up would correctly identify a subgroup at higher risk.
SUMMARYIn this paper we report the first adult case of an "idiopathic" ventricular bidirectional tachycardia (BT), in a 57 year old woman. The tachycardia, at the time of our observation, was incessant in type and had a slightly irregular frequency of about 140 bpm. BT initiated and terminated abruptly, without any temporal relationship to the preceding RR interval, or the QRS morphology. The interval between the two alternating QRS patterns often varied over a wide range of values. The BT could be interrupted only by overdrive atrial and ventricular stimulation, but promptly reappeared as pacing was discontinued. Therapy with quinidine associated with propranolol was effective on a long term trial. The vectorcardiographic analysis and the electrophysiologic investigation demonstrated a ventricular origin of the BT, localizing its site of origin to common myocardial tissue, probably near the two left hemifascicles. Our data could not elucidate the electrogenetic mechanism of this ventricular arrhythmia, because of its chaotic behavior.Additional Indexing Words: Bidirectional tachycardia Ventricular tachycardia BIDIRECTIONAL tachycardia (BT), is an uncommon rhythm disturbance, the origin and mechanism of which are still disputed. 1),3),5)-8) In the majority of cases it occurs as a manifestation of digitalis toxicity, particularly in the presence of severe myocardial disease. This report describes the clinical, electro-vectorcardiographic and electrophysiologic findings in a 57 year old woman with incessant tachycardia, not caused by digitalis or other drugs.
CASE REPORTClinical history: A 57 year old woman was referred because of an incessant BT. The past cardiac history included 17 years of frequent paroxysmal
Twenty six patients (aged 46-80, mean age 64) with bifascicular block in the presence of prolonged H-V interval (trifascicular block), were followed for an average of 31 months after inserting an R-wave inhibited pacemaker (PM) because of syncope and/or dizzy attacks. The underlying rhythm was evaluated at 4-6-month intervals by three different techniques: 1) 12-lead ECG when intrinsic patient rate was faster than PM rate; 2) abrupt PM inhibition (APMI) by the rapid chest-wall stimulation technique, and 3) progressive PM inhibition (PPMI) using a programmed chest-wall stimulation technique capable of decreasing the PM rate gradually to 30 beats/min before complete PM inhibition. In addition, the PPMI allowed the underlying rhythm to be induced and sustained and properly evaluated without any discomfort to the patient. Following PM insertion, 4 patients (15%) developed complete heart block after a mean follow-up of 43 months, and one patient (4%) developed 2nd degree 2:1 A-V block (VX) after 83 months. The P-R interval increased in 5 patients (19%) and decreased in 2 (8%). No change of A-V conduction was found in 9 patients (34%). Three patients developed low atrial rhythm, atrial flutter and atrial fibrillation, respectively (12%). After PM insertion 2 patients still complained of dizziness. None reported syncope. Two patients died during follow-up, both of congestive heart failure (8%). By detection of intrinsic rhythm it was recognized that a long symptomatic paroxysmal phase may precede the development of chronic complete A-V block. Therefore, the insertion of a permanent PM is recommended in patients with unexplained neurologic symptoms and trifascicular disease, without waiting for documented episodes of complete A-V block.
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