[Mechanical complications of temporary pacemakers. Criteria for the diagnosis of perforation and dislodgement (author's transl)]. / Complicaciones mecánicas de los marcapasos temporales. Criterios diagnósticos de perforación y desenclavamiento.

The methods used in the early diagnosis of catheter malposition are compared in 31 patients with temporary endovenous pacemaker. In all cases the heart and the pericardial space were observed either at surgery or at post-mortem examination. The patients were divided into three groups: Group A: eight patients with proof of perforation of the free wall of the right ventricule. Group B: eight patients with dislodgement of the catheter and dysfunction of demand and stimulation without signs of perforation. Group C: fifteen patients without neither dysfunction or perforation. Clinical, radiological and electrocardiographic data were evaluated in each group. With the exception of cardiac tamponade, there were no clinical symptoms distinguishing perforation from dislodgement. Radiologically, only important changes in catheter position had diagnostic value. ECG changes were not diagnostic. Endocavitary ECG permits to locate the catheter with respect to the right ventricular wall. A good contact with the endocardium determines the appearance of a pathologic wave in the distal electrogram which diminishes or disappears after perforation or dislodgement. In the group A patients the QRS was predominantly positive, a feature that was not observed in the other two groups. When the catheter backed up to the atrium, high voltage atrial potentials were registered. Although the analysis of endocavitary recordings constitutes the most useful method to detect catheter malposition, only the total clinical, radiological, and electrocardiographic data provide a firm diagnosis.

[Late potentials analysis in patients with malignant ventricular arrhythmia]. / Análise de potenciais tardios em pacientes com arritmias ventriculares malignas.

PURPOSE: To assess the relationship between late potentials and spontaneous ventricular arrhythmias, organic heart disease, inducibility of arrhythmias at electrophysiological study and ejection fraction. METHODS: The population is comprised by 52 patients (41 men, 11 women with mean age 50 +/- 16 years) with spontaneous clinically documented ventricular tachycardia or ventricular fibrillation. An electrophysiological study was performed with conventional programmed stimulation. Within a week of the test a study of late potentials was also performed. RESULTS: Late potentials were documented in 73% of the patients with ventricular tachycardia and only in 17% of the patients with ventricular fibrillation. Sixty-eight percent of the patients with ischemic cardiopathy presented late potentials and in these, ventricular tachycardia was inducible in 93%. Only one from a group of 7 patients with ventricular arrhythmias and no organic heart disease, presented late potentials. In patients with late potentials, 84% have inducible ventricular tachycardia, but only 26% of patients without late potentials have inducible ventricular tachycardia. The incidence of late potentials was inversely correlated with left ventricular ejection fraction. CONCLUSION: The presence of late potentials was more frequent in patients with ventricular tachycardia than in patients with ventricular fibrillation. The presence of late potentials has a sensibility of 81.5% and a specificity of 78% to detect patients with inducible ventricular tachycardia.