[Compliance of the normal-sized aorta in adolescents with Marfan syndrome: comparison of MR measurements of aortic distensibility and pulse wave velocity]. / Compliance der morphologisch unauffälligen Aorta bei Jugendlichen mit Marfan Syndrom: Vergleich von MR-Messungen der aortalen Dehnbarkeit und der Pulswellengeschwindigkeit.

PURPOSE: To compare the aortic compliance of the normal-sized aorta of adolescents with Marfan syndrome and healthy controls using MR measurements of the aortic distensibility and pulse wave velocity. MATERIALS AND METHODS: Fourteen patients (median age: 15 years) and 11 healthy subjects (23 [12 - 32] years) were examined at 1.5 T. The MR protocol included 2D steady-state free precession (SSFP)-CINE MRI of the aortic distensibility and PC-MRI of the pulse wave velocity. All measurements were positioned perpendicular to the descending aorta at the level of the diaphragm for assessing the changes in the aortic cross-sectional areas and additionally above and below this plane for assessing the pulse wave velocity. In addition contrast-enhanced 3D-MR angiography was performed in adolescents with Marfan syndrome to exclude morphologic changes and to prove normal-sized aorta. RESULTS: Compared with control subjects, adolescents with Marfan syndrome had significantly decreased distensibility and significantly increased pulse wave velocity (chi (2)-test, p = 0.0002) using an age-related non-linear regression analysis. The related aortic compliance was significantly decreased (chi (2)-test, p = 0.0002). There was a good correlation between the two methods (r = 0.86). A low intraobserver variability was found for both methods (< or = 2 %). CONCLUSIONS: MRI allows detecting abnormal elastic aortic wall properties already in the normal-sized aorta of adolescents with Marfan syndrome. Monitoring of these properties could be relevant for evaluating disease onset and progression. MRI has the potential value of compliance measurements for the follow-up and to guide therapy indications.

Effects of a new antiarrhythmic compound [2-benzal-1-(2' diisopropyl-amino-ethoxy-imino)-cycloheptane hydrogen fumarate] on the electrophysiological properties of mammalian cardiac cells.

Intracellular microelectrodes were used to study the effects of Th 494 [2-benzal-1-(2' diisopropyl-amino-ethoxy-imino)-cycloheptane hydrogen fumarate; 1-100 mumol/1) on transmembrane electrical activity of sinus node and Purkinje fibres of the rabbit as well as on atrial trabeculae and papillary muscles of the guinea pig. In the atrial and in the ventricular myocardium (32 degrees C; driving rate 0.3-0.5 Hz) Th 494 exerted the following electrophysiological actions: no change of the resting potential nor of the amplitude of the action potential; concentration- dependent reduction of the maximum rate of rise (dV/dt)max of the action potential; slight increase of the action potential duration at lower concentrations (1-20 mumol/l), loss of the plateau at higher concentrations (above 20 mumol/l). The isometric force of contraction was moderately reduced by Th 494 (about 20% reduction by 2 mumol/l). The h infinity-curve relating (dV/dt)max of the action potential to the membrane potential was depressed by Th 494 without being shifted along the voltage axis. The reduction of (dV/dt)max was considerably more pronounced at higher driving frequencies. After interruption of stimulation for various periods, (dV/dt) max of the first action potential attained a steady-state value in a two-exponential fashion, suggesting use-dependence as well as a change in the recovery kinetics of the fast Na+ channel by Th 494. In Purkinje fibres (37 degrees C) Th 494 reduced (dV/dt) max in a similar manner. The duration of the action potential was considerably decreased at the level of the plateau. In the primary pacemaker region of the sinus node (37 degrees C) Th 494 moderately reduced the rate of diastolic depolarization and diminished at higher concentrations the amplitude of the action potential. All effects of Th 494 were only slowly reversible by drug-free perfusion. In view of its effect on (dV/dt) max, Th 494 resembles quinidine in its potential-dependence, whereas its time-dependence bears greater similarity with lidocaine.

[Transesophageal electroconversion of atrial reentrant tachycardias early or late following surgery for congenital heart disease]. / Transösophageale Elektrokonversion atrialer Reentry-Tachykardien in der Früh- oder Spätphase nach Operationen angeborener Herzfehler.

Atrial reentrant tachycardias (ART) are a potentially life-threatening complication in survivors of congenital heart disease surgery. From July 1993 to December 1997, temporary transesophageal pacing was used to convert 29 tachycardia episodes in 19 patients. At the time of the first tachycardia episode, patients' ages were 1 month to 26 years (mean 9.8 yrs). Time from operation to onset of first tachycardia episode ranged from 1 day to 19 years. Onset was within the first 2 weeks postoperatively in 6 patients and occurred later in 13 patients (1 to 19 years after operation). Postoperative pacemaker implantation had been performed in 2 pts; 17 of 19 pts were receiving antiarrhythmic medication. After placing a quadripolar transesophageal catheter, atrial and ventricular signals were recorded and atrial stimulation performed. Atrial cycle length of tachycardia ranged from 160-380 ms with 1:1 to 4:1 AV conduction. Temporary transesophageal pacing was performed following an algorithm starting with 4 extrastimuli (20 ms below atrial cycle length of tachycardia). Tachycardia terminated in 27 of 29 cases (93%) without complications. In 3 cases, conversion was achieved by pacing after amiodarone 5 mg/kg i.v. After tachycardia conversion, sinus- or pacemaker rhythm was present in 20 cases. In 9 cases atrial fibrillation was recorded; spontaneous conversion to sinus rhythm occurred after a maximum of 3 min (7 cases) or persisted and required direct current cardioversion (2 cases). In conclusion, transesophageal atrial pacing is an effective, relatively noninvasive method for conversion of atrial reentrant tachycardias after operation for congenital heart disease.