In vivo degradation of polymers. II. Change of mechanical properties and cross-link density in silicone rubber pacemaker lead insulations during long-term implantation in the human body.

The results of mechanical testing, microscopic examinations and swelling of the explanted clinically used silicone rubber pacemaker lead insulations are presented. An experimental set of 100 lead insulations implanted for times ranging from 3 d to 11 yr were evaluated for change of mechanical properties and cross-link density during clinical use. The results show that the silicone rubber tubing suffers a gradual structural change due to its exposure to the physiological environment of the human body. A spiral deformation pattern due to the permanent set of the silicone rubber tubing in contact with the electrode leading wire was observed.

In vivo degradation of polymers. I. Change of mechanical properties in polyethylene pacemaker lead insulations during long-term implantation in the human body.

The results of mechanical testing and microscopic examination of explanted clinically-used polyethylene pacemaker lead insulations are presented. An experimental set of 98 lead insulations implanted for times ranging from 7 d to 11 yr was evaluated for changes in mechanical properties during clinical use. The results showed that the polyethylene tubing suffered a gradual structural change, due to its exposure to the physiological environment of the human body. The decline of the mechanical properties with implantation time is described by empirical formulae. Abrasive deterioration was also observed and is discussed.

Long-term experience with the automatic implantable cardioverter-defibrillator in a patient with ventricular tachyarrhythmias.

The authors offer a retrospective appraisal of a technique for the treatment of malignant ventricular tachyarrhythmias using the automatic implantable cardioverterdefibrillator (AICD) in a patient with right ventricular arrhythmogenic dysplasia. Device function after the first implantation and reimplantation was checked by repeated (63 times) outpatient 24-hr ECG monitoring. All recordings suggested a reliable detecting and defibrillating function of the AICD. The patient died two years after the first implantation. The probable cause of death was failure of the mechanical myocardial function.

The automatic implantable cardioverter-defibrillator in the treatment of severe tachyarrhythmias.

The automatic implantable cardioverter-defibrillator constitutes a new therapeutic alternative in malignant ventricular tachyarrhythmias unresponsive to drug therapy. In Czechoslovakia, the device was first implanted to a 29-year-old patient on 31 October, 1984. The article, apart from presenting his case report and a description of the therapeutic procedure, includes the electrocardiograms attesting to the device's effective performance as registered by continuous Holter monitoring.

Intraaortic balloon counterpulsation.

The authors summarize their experience with intraaortic balloon counterpulsation (IABC) at the Institute for Clinical and Experimental Medicine between 1978-1984. A total of 756 cardiac surgery procedures were performed for ischaemic heart disease (IHD), and 266 procedures for rheumatic heart disease (RHD). Of patients operated on for IDH, IABC was used in 38 (5%) and, of those undergoing surgery for RHD, in 38 cases (14%). Overall, IABC was employed in 76 patients, i.e., 7%. Ventricular assistance using IABC was successful in 55% of patients. The technique was significantly more successful in IHD (68%) than in RHD (42%) patients. IABC was less successful in IHD patients suffering myocardial infarction intraoperatively. Moreover, the success of IABC depended on its early initiation. Eleven patients (14%) developed complications associated with IABC. The data do not differ from results reported by world's leading centres.

Laser surgery of a digital angiosarcoma: report of a case and six-year follow-up study.

A single digital angiosarcoma was excised by a carbon dioxide laser with small portions of this tumor excised by the scalpel and the high-frequency electrosurgical knife. The patient has been followed for 6 years without any local recurrence or additional lesions. There is a brief summary of investigative studies with lasers in benign and malignant vascular tumors.