[Radiofrequency ablation in the treatment of supraventricular arrhythmias in pediatrics. Experience with 203 consecutive patients]. / Ablación con radiofrecuencia en tel tratamiento de las arritmias supraventriculares en pediatría. Experiencia en 203 Pacientes consecutivos.

We report the results of radiofrequency catheter ablation in 203 patients under 18 years of age with supraventricular tachyarrhythmias between April 1992 and June 1997. The presence of an accessory pathway caused the tachyarrhythmia in 181 patients (89.1%) with a total of 187 accessory pathways; atrioventricular nodal reentry caused the arrhythmia in 18 patients (8.8%) and atrial flutter in only 4 patients (1.9%). We eliminated the accessory pathway in 171 patients (91.4%), 23 patients showed recurrence of the tachycardia and we had complications in 4 patients (2.1%). The procedure was successful in the treatment of the atrioventricular nodal reentry in the 18 cases, with ablation of the slow pathway in 17 cases and in only one patient of the fast pathway, one patient showed total A-V block, and recurrence of the arrhythmia in 3 cases (16.6%). Finally the procedure was successful in the 4 cases of atrial flutter with one recurrence (25%). In the total of the series, the radiofrequency catheter ablation was successful in 193 patients (95%), with recurrence of the arrhythmia in 27 cases (13.3%) and with complications in only 5 patients (2.6%). Radiofrequency catheter ablation is a safe and effective procedure for the definitive treatment of supraventricular tachyarrhythmias in children.

[Usefulness of exercise test in programming dual chamber pacemakers]. / Utilidad de la prueba de esfuerzo en la programación de los marcapasos bicamerales.

Prospectively, we studied 42 patient to evaluate the usefulness of treadmill exercise to programme pacemaker DDD in relation to the functioning upper frequency (relation between block frequency of pacemaker and the upper rate frequency). We excluded patient who had no treadmill exercise test after implant pacemaker. During stress 7 (17%) patient presented AV conduction 1:1 (group I); 16 (38%) second degree AV block type Wenckebach (group II); 14 (33%) second degree AV block 2:1 (group III); and 5 (12%) showed inhibition of the pacemaker by intrinsic activity (group IV). Block frequency of the pacemaker in group I and II was superior in regard of the upper rate frequency, 156.85 +/- 22.16 vs 141.43 +/- 20.82 and 135.25 +/- 11.54 vs 121.25 +/- 5.9, respectively. In group III and IV, it was lower, 120.36 +/- 15.31 vs 138.57 +/- 13.29 and 121.0 +/- 7.38 vs 142.0 +/- 14.39. The comparative analysis of the block frequency of the pacemaker in relation with the upper rate frequency showed statistically significant differences (p < 0.05) between groups I and II, and between the group I and III. The appearance of second degree AV block 2:1 is nonphysiologic, is rather due to an abrupt falling in the cardiac output. This phenomenon is able to be predicted and corrected by programming with the use the telemetry with parameters as the AV delay, as well as upper rate frequency and post-ventricular refractory atrial period.

[Positive exercise test in hypertensive patients correlated with coronary angiography]. / Prueba de esfuerzo positiva en pacientes hipertensos en correlación con coronariografía.

With the purpose of evaluate the state of the coronary arteries in hypertensive patients with positive exercise test, 82 patients were selected, 50 male and 32 female with mean age of 56.9 +/- 13.2 years. Angiography was normal in 25 patients thirteen patients had a single coronary arteries narrow of less than 50% and 44 cases with significant coronary arteries lesions of more than 50%. The parameters obtained in the exercise test are not significant for statistic purposes. Systolic hypertension or flat response was more frequent in the group with advanced coronary lesions with a predicted positive value in coronary obstructions of 66 and 75%. We conclude that 70% of hypertensive patients have obstructive coronary lesions of some degree.

[Hemodynamic study in hypertensive cardiopathy under ischemia induced by atrial stimulation in the absence of fixed coronary obstructions]. / Estudio hemodinámico en la cardiopatía hipertensiva bajo isquemia inducida por estimulación auricular en ausencia de obstrucciones coronarias fijas.

With the purpose to study the haemodynamic changes that occur with myocardial ischaemia induced by atrial pacing (AP) in hypertensive heart disease, we studied 7 patients with such condition, all of them with a long time history of systemic hypertension, electrocardiographic signs at rest of left ventricular hypertrophy and ST-segment depression, at least of 0.5 mm. All the patients showed normal coronary arteries in angiocardiogram. AP was started 10 beats above the basal heart rate with increments of 10 beats every 2 minutes until a ST-segment depression at least of 2 mm was obtained which occurred in all the cases studied. After every 2 minutes of AP a simultaneous 12-leads electrocardiogram recording and left ventricular and aortic pull-back pressure were obtained. At the desired end point the AP was abruptly stopped and the same parameters were registered at 3, 5, 10 and 15 minutes until recovery. During AP the left ventricular systolic pressure (LVSP) did not show any significant change, with the exception of a patient who experienced angor pectoris during the proceeding. The left ventricular end-diastolic pressure (LVEDP) increased in 3.4 +/- 1.7 mmHg, change that was statistically significant (p less than or equal to 0.01) but not hemodynamically important since only in one patient it increased above the normal levels (from 13 mmHg basal to 17 mmHg during AP). In contrast, LVEDP markedly rose above normal when AP was stopped. It is concluded that neither LVEDP nor LVSP play an important role in the genesis of the ST segment depression seen in these patients. It is showed that, similar as in patients with obstructive coronariopathy, these cases work on a depressed Starling curve during AP and its recovery for what is thought that the functional meaning of ischaemia for both entities is similar no matter that their pathogenetic mechanisms are different.

[Electrophysiological studies in permanent atrial paralysis]. / Estudios electrofisiológicos en la parálisis auricular permanente.

Permanent atrial paralysis is a very rare entity characterized by absence of electrical and mechanical activity of the atria which persists for months or years. We present a patient with congestive cardiomyopathy and chronic atrial paralysis. The phonomechanocardiographic study confirmed the absence of mechanical contraction of the atrium and did not show atrial electrical activity in the superficial electrocardiogram nor in the intracavitary tracing. In the electrophysiological study of the biopsy of the atrial myocardium an unexcitable tissue was found with an important diastolic despolarization of 30 mv. The histologic and ultrastructural studies showed nonspecific changes, with the replacement of the myocardial cells by fibrous tissue.