[Intermittent pre-excitation after adenosine administration]. / Preexcitación intermitente tras administración de adenosina.

We describe a case of 2:1 intermittent preexcitation after adenosine administration in a patient with an accessory pathway that did not show preexcitation on the basal ECG. We review the mechanisms involved that explain this event and the possible utility of adenosine to show accessory pathways that do not show preexcitation on the ECG.

[Image of pseudocapture caused by micro-dislodgment of the electrode in a VDD pacemaker]. / Imagen de seudocaptura por microdesplazamiento del electrodo en un marcapasos VDD.

The new AV sequential pacemakers have improved the suitability for the election of the best pacing mode for each patient. The complexity of the systems may mask some dysfunctions. In the presented case, a failure to capture due to micro-dislodgment, may have been missed in a simple pacemaker control, because of the combination of several factors: the presence of normal AV conduction at that moment, the concordance between the pacemaker stimulus and the conducted QRS complex and the similar morphology of the conducted and paced QRS complex.

[Peritoneal migration of defibrillator implanted behind the rectus abdominis]. / Migración peritoneal de desfibrilador implantado tras recto abdominal.

Automatic Implantable Cardioverter Defibrillator (AICD) has become a therapeutic option to malignant ventricular tachyarrhythmias. Its bulky device responds for discomfort and the likelihood of generator extrusion or migration, when implanted under the subcutaneous tissue. Among alternative sites, pre-peritoneal location has several advantages but hides its own risks. We present a generator peritoneal migration from a pocket made behind the rectus abdominis.

[Complications associated with nonfunctioning pacemaker electrodes retained within the cardiovascular system]. / Complicaciones asociadas con electrodos de marcapasos no funcionantes retenidos en el sistema cardiovascular.

INTRODUCTION AND OBJECTIVE: The aim of the present study was to evaluate the complications in patients with functionless pacing leads retained in the cardiovascular system. PATIENTS AND METHODS: We retrospectively studied 39 patients: 31 underwent surgery for electrical or mechanical failure (group I) and eight for cutaneous pocket infection (group II). The follow-up was 45 +/- 34 months. RESULTS: Only one patient (3%) from group I presented infectious complications probably related to the retained pacing lead. Seven patients (87%) in group II presented recurrence of the infection with persistent fever and/or septicemia due to skin erosion and unnoticed pacing lead infection (p < 0.0005). Removal of the infected generator was performed in 8/39 (21%) of the patients. Thoracotomy to explant the infected retained leads was required in five of them (62%). No patient presented lead migration or venous thrombosis during the follow-up. CONCLUSIONS: Retained pacing leads in the cardiovascular system are well tolerated. However, in spite of adequate antibiotic treatment, patients with local and pacemaker system infection may present recurrence of the infection with persistent fever and/or septicemia. Early surgical pacemaker system removal is recommended in these patients due to the high morbidity.

[Mechanisms favoring and triggering atrial fibrillation]. / Mécanismes favorisant et déclenchant la fibrillation auriculaire.

Many experimental and clinical studies have demonstrated that it is possible to trigger atrial fibrillation (AF) by vagal stimulation which reduces and disperses the atrial refractory periods and decreases the threshold of fibrillation. In order to induce fibrillation, it is necessary to deliver a stimulation near to the refractory period. It has also been shown that, in these conditions, there is a delay in atrial conduction. A temporal relationship between the preceding diastole and the coupling interval increases atrial vulnerability and plays an equally important role. The decrease in the effective atrial refractory period, especially when the values are widely dispersed, and the delay in conduction predisposing to atrial reentry, may be considered to be the two most important electrophysiological mechanisms of AF. However, in order to maintain AF, the atrium must be dilated, especially when there is a concurrent cardiac disease. The presence of a shorter "wave length" of activation allowing multiple reentry circuits is an essential condition for sustaining AF. All conductions of induction and maintenance of AF may be observed without participation of S.N.A.. When no cause of AF (atrial pathology, etc.) is apparent, a short atrial refractory period with dispersion of its values and slowing of atrial conduction in presence of an extrastimulus are the probable inducing factors.

Recovery of sinus node function after pacemaker implant for sinus node disease following cardiac transplantation.

In a 4-year interval, 3/55 (7.8%) heart transplant recipients developed (greater than 4 weeks) severe sinus node dysfunction. An epicardial ventricular pacemaker was implanted at 90, 40, and 38 days after operation. Follow-up ranged from 7 to 20 months. In two of the three cases, failure of stimulation or sensing was detected at the 3rd and 4th month after pacemaker implantation. Sinus rhythm reappeared in two of the three patients at the 2nd and 4th months after transplantation. Severe sinus node disease requiring pacemaker implantation can improve following the first 3 months after transplantation. Failure of stimulation or sensing may not be uncommon.

Ventricular fibrillation in the Wolff-Parkinson-White syndrome.

Ventricular fibrillation (VF) is a well-known but rare complication of the Wolff-Parkinson-White syndrome (WPW). Clinical and electrophysiological data of 23 patients with spontaneous VF were compared with data from 100 consecutive patients with WPW without VF but with symptomatic supraventricular tachycardia. The 23 patients were collected in a multicentre retrospective study in seven European centres. VF occurred in only one patient who was receiving antiarrhythmic drugs, and was the first manifestation of the syndrome in six. No significant differences were found between those with VF and without VF in age, complaints of palpitations, syncope, and presence of structural heart disease. The retrograde effective refractory period of the accessory pathway, the atrial refractory period and the fastest atrial pacing rate with 1:1 anterograde conduction over the accessory pathway were similar in both groups. Significant differences were found for sex, permanent pre-excitation on the electrocardiogram, type of documented supraventricular tachyarrhythmias, shortest RR interval less than or equal to 220 ms during spontaneous atrial fibrillation (AF), inducibility of supraventricular tachycardias, ventricular effective refractory period less than or equal to 190 ms, mean shortest RR interval during induced AF less than or equal to 180 ms and presence of multiple accessory pathways.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of the evolution of masked bifascicular block.

Masked bifascicular block (MBB) (absent or minimal S in I and VL, high R in Vi and AQRS approximately -60 degrees) is a rare condition. We have found 16 such cases in the last 12 years, thirteen male and three female, mean age 70 +/- 9 years. The conventional electrocardiogram was tabulated and the clinical features and evolution of the patients were followed over 39.1 +/- 32 months. Ten patients required pacemakers, nine because of complete atrioventricular (AV) block or increase in the previous AV block. Seven patients died (follow-up 27.3 +/- 32 months), five from heart failure. This study shows: (1) MBB is a subgroup of patients with a high risk of advanced atrioventricular block; (2) a pacemaker implant does not significantly reduce the high mortality in this group because of the severity of the underlying disease; (3) these results should be evaluated in a larger series of patients in order to confirm our provisional results.

Interatrial conduction block and retrograde activation of the left atrium and paroxysmal supraventricular tachyarrhythmia.

We studied 16 patients with electrocardiographic evidence of advanced interatrial block and retrograde activation of the left atrium (P greater than or equal to 0.12 s, and diphasic (+/-) P waves in leads II, III, and VF). Eight patients had valvular heart disease, four had dilated cardiomyopathy and four had other forms of heart disease. Patients with valvular heart disease and cardiomyopathy were compared with a control group of 22 patients with similar clinical and echocardiographic characteristics, but without this type of interatrial block. Patients with advanced interatrial block and retrograde activation of the left atrium had a much higher incidence of paroxysmal supraventricular tachyarrhythmias (93.7%) during follow-up than did the control group, (27.7%) (P less than 0.001). Eleven of 16 patients (68.7%) with advanced interatrial block and retrograde activation of left atrium had atrial flutter (atypical in seven cases, typical in two cases, and with two or more morphologies in two cases). Six patients from the control group (27.7%) had sustained atrial tachyarrhythmias (five atrial fibrillation and one typical atrial flutter). The atrial tachyarrhythmias were due more to advanced interatrial block and retrograde activation of left atrium and frequent atrial extrasystoles than to left atrial enlargement, because the control group with a left atrium of the same size, but without advanced interatrial block and retrograde activation of left atrium and with less incidence of atrial extrasystoles, had a much lower incidence of paroxysmal tachycardia.

[Electrophysiologic characteristics of the transplanted heart]. / Características electrofisiológicas del corazón trasplantado.

The electrophysiologic characteristics of the denervated human heart were assessed in 20 cardiac transplants recipient from the Cardiology Department, at the Hospital of San Pablo, Barcelona, Spain. We studied the donor and the recipient sinus node function at rest and exercise test. Holter recording of 24 hours was performed in a few cases. At rest, in 14 patients the intrinsic heart rate of the donor atrium was slower when we used the technique of José. When we analyzed all the results we did not find statistical differences in the heart rate of either: the donor or the recipient atria (r = 0.58, p less than 0.01). However we observed a marked increase in heart rate of the donor with exercise test and normal activity (Holter), probably reflecting an increase in circulating catecholamines (exercise test: base-line 116 +/- 16 vs maximum exercise 140 +/- 10, p less than 0.001; Holter: minimal rate 64 +/- 9.66 vs maximal rate 112 +/- 23, p less than 0.001). We also describe the cardiac arrhythmias including two sudden deaths associated with ventricular tachyarrhythmias and in five patients sinus node disfunction in relation with episodes of acute rejection. We concluded that is important to perform a standard 12 lead electrocardiogram, exercise testing, Holter recording and electrophysiologic study as part of the ongoing routine evaluation of surviving cardiac transplant patients.

Utilidad de la programación temporal del marcapaso en modo VVT para el tratamiento de las taquicardias ventriculares repetitivas / Usefulness of the temporary pacemaker programming to the VVT mode in the treatment of recurrent ventricular tachicardia

Se presenta el caso de un paciente, varón de 59 años, intervenido de prótesis de Björk en posición aórtica y comisurotomía mitral, con mala función ventricular y episodios repetidos de taquicardia ventricular (TV), a pesar del tratamiento anti-arrítmico con amiodarona. El estudio electrofisiológico (EEF) puso de manifiesto que la TV por reentrada cedía con extraestímulos (EE) aplicados en el apex del ventrículo derecho . Fuera de los episodios de TV, el paciente se mantenía con arritmia completa por fibrilación auricular, con frecuencias ventriculares medias lentas. Se implantó marcapaso Medtronic Spectrax 5985, multiprogramable, con posibilidad de programar a modo VVT y con períodos refractarios efectivos (PRE) programables cortos (220mseg). Durante las crisis de TV el MP se programaba temporalmente a modo VVT con PRE de 220 mseg y a través de estimulación torácica por medio del estimulador de electrofisiología se conseguían interrumpir las crisis de TV con EE (2 ó 3) sincronizados. Gracias al mecanismo de disparo ("triggered", la estimulación tóracica obliga al buscado disparo del marcapasos, que de este modo funcional igual que un estimulador externo de electrofisiología, siempre que se tengan en cuenta sus PRE y mantegan adecuados los umbrales de percepción y estimulación

[Use of temporary pacemaker programming in VVT mode for the treatment of recurrent ventricular tachycardia]. / Utilidad de la programación temporal del marcapaso en modo VVT para el tratamiento de las taquicardias ventriculares repetitivas.

This is a report of a 59-year-old man with a Björk aortic prosthetic valve and mitral commissurotomy with left ventricular dysfunction and recurrent ventricular tachycardia (VT) in spite of antiarrhythmic therapy with amiodarone. Serial electrophysiologic studies were performed using standard ventricular extrastimulation technique. During these studies, sustained VT was induced and terminated by programmable extrastimulus pacing. The usual rhythm of the patient was atrial fibrillation with slow ventricular rate. The Medtronic Spectrax model 5985 pulse generator was implanted. A temporary program converts this device from inhibited (VVI) to triggered (VVT) mode, permitting programmed ventricular stimulation through synchronization with chest wall stimulation by a standard external programmable stimulator. During episodes of VT the pacemaker was temporary programmed to the VVT mode with a refractory period of 220 msec. With the chest wall stimulation by a electrophysiology stimulator it was possible to convert the VT with 2 or 3 synchronised extra stimulus. Thanks to the triggered mode the pacemaker will fire when the chest wall is stimulated, working as an external electrophysiology stimulator.

Concealed atrial electrical activity.

In the following paragraphs we describe a case diagnosed clinically and haemodynamically as a cardiomyopathy. Atrial flutter which was not in evidence in the standard ECG was diagnosed by the use of a new technique of amplification and filtering of special surface leads (T.A.F.). The diagnosis was later confirmed by means of special internal techniques (intra-atrial ECG and His bundle recording). The existence of a subpraventricular rhythm, probably sinusal, and also unapparent in the standard ECG, was observed by using the same method after electrical defibrillation. We comment on the extreme rareness of discovering concealed atrial rhythms and their possible explanation, and we emphasize the usefulness of the T.A.F. technique in their diagnosis.