Human atrial repolarization: effects of sinus rate, pacing and drugs on the surface electrocardiogram.

OBJECTIVES: We studied the effects of rate and some cardioactive drugs on the atrial surface electrocardiogram (ECG). BACKGROUND: In atrioventricular block, atrial surface ECG is unmasked. The effect of rate alone permits detection of the effect of other exogenous stimulations such as drugs in the presence of rate alterations. METHODS: High fidelity, high gain ECG leads I, II and III were recorded from 51 patients with heart block. Durations of P and Ta waves and the total PTa interval were measured from nonconducted atrial events. RESULTS: No relationship was found between sinus cycle length and PTa, P or Ta in 31 patients. In 20 patients, progressively decreasing the atrial pacing cycle length from 853 ms to 381 ms resulted in a linear reduction of the PTa interval from 444 to 291 ms (rho = 0.76, slope = 0.24). This was largely due to shortening of Ta. A linear rate correction formula was derived: corrected PTa = PTa - 0.24 (PP - 1000). Atropine (0.02 mg/kg) shortened the PP interval (p < 0.001) and the PTa interval (p < 0.01). Propranolol (0.1 mg/kg) prolonged the PP interval (p < 0.001) but did not alter the PTa interval. Neither disopyramide (2.0 mg/kg) nor flecainide acetate (2.0 mg/kg) altered the PP interval, but both prolonged the PTa interval (p < 0.001). This was largely due to P wave lengthening after flecainide (p < 0.001) and to Ta prolongation after disopyramide (p < 0.001). CONCLUSIONS: In heart block, PTa, P and Ta waves can be measured reliably. The effects of pacing and some antiarrhythmic drugs on the atrial myocardium are similar to those known at the ventricular level.

Successful radiofrequency ablation of a true paraHissian accessory pathway.

Radiofrequency catheter ablation seems to become a first-line therapy for patients with paroxysmal tachycardias using an accessory pathway. We report the case of a 31-year-old woman who suffered from drug-resistant recurrent reciprocating tachycardia, using an uncommon accessory pathway. The 12-lead electrocardiogram in sinus rhythm showed the following characteristics: a positive delta waves in leads I, II, aVL, aVF, QRS axis = 0 degrees, R/S in lead V1 < 1, and a special QRS pattern in the precordial leads (QS or Qr in V1-V3 and QRS transition > V3). A deep septal parahissian accessory pathway has been localized using classic endocardial mapping procedures and has been confirmed during successful radiofrequency catheter ablation. Normal auriculo-ventricular conduction has been totally preserved. No complications or recurrence were observed during the follow-up. We have reviewed the electrophysiologic criteria to confirm this rare accessory pathway location.

[Arrhythmogenic dysplasia of the right ventricle in a 16-month-old child]. / Dysplasie arythmogène du ventricule droit chez un enfant de 16 mois.

The clinical history of a 16-month old child with an arrhythmogenic right ventricular dysplasia is reported. This is one of the youngest patients described in the literature. The pitfalls of the diagnosis and the particularities of the treatment of recurrent ventricular tachycardias are underlined.