[A new cardiac pacemaker stimulation technology (autocapture) allows, with unchanged life expectancy, reduction of generator size by half]. / Eine neue Herzschrittmacher-Stimulationstechnologie (Autocapture) ermöglicht bei unveränderter Lebensdauer die Reduktion der Generatorgrösse auf die Hälfte.

Energy delivery (stimulation amplitude) of a pacemaker should be adjusted to the depolarisation threshold of the heart, which is a nonconstant magnitude. As programming of the stimulation amplitude is time-consuming, many pacemakers are never adjusted to the measured threshold referring to energy delivery. The unnecessary energy loss subsequently reduces the longevity of the implanted devices and remains the weak point of modern pacemakers. Autocapture function (automatic stimulation threshold search, subsequently automatic amplitude regulation 0.3 V above measured threshold, evoked response detection to verify the efficacy of every stimulus and back up pulse in case of loss of capture) is for the first time realized in an extremely small, rate adaptive, multiprogrammable single chamber pacemaker (Microny SR+ 2425T). The pulse generator was tested in a multicentric, european clinical investigation study. These pacemakers were implanted in 8 patients (5 male, 3 female) between December 1994 and April 1995. Automatic measurement of Autocapture threshold revealed 0.7 +/- 0.15 V at implantation, 1.5 +/- 0.3 V after 1 month, 1.3 +/- 0.14 V after 6 months and 1.3 +/- 0.14 V 1 year after implantation. A safety margin of 0.3 V is added to the threshold value to secure capture, therefore mean stimulation amplitude is 1.6 V after 12 months implantation time. The Autocapture feature minimizes current drain and that means that this extremely small generator provides a comparable life as the twice as large common generators used at present time.

Subtotal rarefication of one aortic leaflet in a bicuspid aortic valve due to large aneurysm of left Valsalva's sinus.

In a 39-year-old man an isolated, unruptured extracardiac aneurysm of the left sinus of Valsalva led to almost complete rarefication of one aortic valve leaflet, causing insufficiency of the valve. At operation the aneurysm entrance was closed with a patch and prosthetic replacement of the bicuspid aortic valve was performed. The result was satisfactory.

[Successful resuscitation in severe hypothermia following near-drowning]. / Erfolgreiche Reanimation bei ausgeprägter Hypothermie nach Beinahe-Ertrinken.

A six-year-old boy fell into an ice-cold mountain stream and was immediately washed away. He was rescued 65 min later, 6 1/2 km downstream, seemingly lifeless with a rectal temperature of 16.4 degrees C. He was flown by helicopter to the surgical clinic of Innsbruck University, while resuscitation measures were undertaken by an accompanying doctor. After cannulation of the femoral artery and vein, extracorporeal circulation (ECC) with a child-size oxygenator was started and the blood rewarmed over 96 min in steps of 3 degrees C. Once circulatory stability and adequate cardiac output had been achieved ECC was gradually discontinued while the patient was still slightly hypothermic. Ten months after the accident the boy is restored to health, except for minimal residual neurological signs. There is a high chance for full neurological recovery.

Complete prosthetic valve thrombosis despite several thrombolytic treatments after tricuspid valve replacement.

We discuss the case of a 50-year-old man who underwent tricuspid valve replacement with a mechanical prosthesis (Duromedics) due to traumatic tricuspid insufficiency following a blunt chest trauma fifteen years previously. Despite correct anticoagulation therapy several events of prosthetic valve thrombosis occurred in the following years. The patient was treated four times by thrombolytic therapy. Finally, seven years after the initial operation the mechanical valve was replaced by a Carpentier-Edwards bioprosthesis because of complete blockage.

[Late valvular dysfunction after mechanical mitral valve replacement]. / Späte Klappendysfunktion nach mechanischem Mitralklappenersatz.

14 years after a Björk-Shiley prosthesis had been implanted because of combined mitral failure, a 68-year-old woman complained of progressive decrease of physical powers combined with apnoea, retrosternal feeling of pressure and tachycardiac atrial fibrillation. Five weeks later, onset of cardiac decompensation with dyspnoea at rest and signs of congested pulmonary circulation were noted. Echocardiography revealed stenosis of the mitral valve prosthesis. The patient was operated on two days later. It became evident that the patency of the prosthesis was greatly obstructed by connective tissue which had proliferated at the ventricular side. The original valve prosthesis was replaced by a St. Jude bi-leaflet valve. The likelihood of prosthesis dysfunction must always be considered if there is a deterioration in the patient's condition after a long uncomplicated postoperative course following cardiac valve replacement.

[Bioprosthesis degeneration in the aortic and mitral valve position. Results and problems from the cardiosurgical viewpoint]. / Bioprothesendegeneration in Aorten- und Mitralposition. Ergebnisse und Probleme aus kardiochirurgischer Sicht.

38 patients (20 men, 18 women) underwent reoperation between July 1989 to September 1992 because of degeneration of bioprosthetic valves implanted in aortic or/and mitral position. Retrospective analysis revealed a mean implantation time of 116.5 +/- 31.5 months for the bioprostheses (median 116). At reoperation 63.2% of them had a single valve replacement, 36.8% a more complex cardiac procedure (double or triple valve replacement, valve replacement and coronary bypass grafting). 50% (n = 9) of the reoperation cohort were symptomatic (NYHA III), 16 (42.1%) were serious symptomatic (NYHA IV). All deaths were NYHA IV preoperatively. Early mortality was 18.4% (n = 7). Mean age at the time of first operation was 51 +/- 10.7, mean age at reoperation was 60.5 +/- 10.6. There was a significantly longer aortic clamp time (AKT, p = 0.0005) and bypass time (BPT, p = 0.0000) compared to first operation, also a significantly longer BPT of the deads confronted with the survivors (p = 0.0075). Bioprosthetic valves in mitral position were significantly longer implanted (p = 0.0416) than in aortic position. But there was no difference in implantation time of commercially available Carpentier-Edwards- or Ionescu-Shiley grafts. At reoperation we changed more than 95% of the degenerated valves to mechanical devices--corresponding to international tendencies. We discuss the early tissue degeneration of bioprosthetic valves and their increasing problem during reoperation.

[Pacemaker implantation via a persistent left superior vena cava in atresia of the true superior vena cava]. / Schrittmacherimplantation über eine persistierende linke obere Hohlvene bei Atresie der eigentlichen Vena cava superior.

Implantation of a single-chamber pacemaker was planned in an 83-year-old woman with sick-sinus syndrome causing dizziness, bradycardia and tachycardia. After puncture of the right subclavian vein it proved impossible to advance a guide-wire into the superior vena cava, under fluoroscopy the wire always being seen to coil in the left subclavian vein and hence passing into a caudally directed vein. This vessel proved to be a persistent left superior vena cava (PLSVC) which connected to a markedly dilated coronary sinus (2 cm diameter) opening into the right atrium. An 85-cm electrode was then passed via the PLSVC and right atrium into the right ventricle without difficulty and was anchored in its apex. Echocardiography failed to reveal any further anomaly. Three-dimensional computed tomographic reconstruction established atresia or agenesis of the (right) superior vena cava. Normal pacemaker function freed the patient of all symptoms postoperatively.

[Possibilities for saving homologous blood in heart surgery]. / Möglichkeiten des Fremdblutsparens in der Herzchirurgie.

The risks of blood transfusion in context with the increasing number of operative open-heart procedures and the linked increased demand for blood products present a challenge to find methods of saving homologous blood. On the one hand there is increasingly less blood at the surgeon's disposal and on the other hand there is the threat of infectious complications with viruses of the HIV or the hepatitis group, as well as allergic reactions. At present we are developing the concept of blood saving as a programme which should work without excess demands on the staff and which can be adjusted to the needs of the individual patient. The programme consists of the following components: preoperative self donation, use of cell saver, acceptance of e relatively low hematocrit, medication to alter the coagulation process and blood-less priming.