Search

From a total of 1,152 consecutive patients with heart valve replacement (1964-87) 108 patients (9.4%) had to be reoperated. Mechanical valves had to be replaced (n = 89) mainly because of perivalvular leakage followed by prosthetic stenosis and dysfunction. The lowest reoperation rate was found with Björk-Shiley prostheses (3.4%). Bioprostheses (reoperation rate 8.2%) had to be reoperated predominantly as a consequence of dysfunction. Ten years following implantation 30% of bioprostheses had to be replaced. Patients with reoperations demonstrated, in comparison to patients with singular valve replacement, no significant change in early mortality during the last 6 years (6.8% vs 5.4%). Furthermore, both patient groups revealed similar survival rates (10 years; 78% vs 76%) and improvement of life quality. However, non-lethal peri- and postoperative complication rates were higher in reoperated patients compared to patients with first valve replacement.

During recent years, advances in cardiology and cardiac surgery have led to an increased number of older patients submitted for heart valve replacement. The following retrospective study analyses perioperative risk and long-term prognosis of 168 patients older than 60 years of age, compared with 942 patients younger than 60 years of age with heart valve replacement. There was no significant difference in 7-year actuarial survival, late mortality, late complications and postoperative functional improvement for both groups. However, early mortality was higher in patients over 60 years of age than in the group of patients under 60 years (7.9% vs. 4.5% from 1980-85, p less than 0.05), especially when multivalvular replacement was performed or the patients were in preoperative functional class NYHA IV. The results indicate that in patients over 60 years of age, heart valve replacement can be performed with a good long-term prognosis and a marked improvement in the quality of life. Early mortality can be reduced to an acceptable rate if the patient is operated in time.

A new rate-modulated pacemaker system optimized by combination of two sensors is described. The parameter body activity and central venous blood temperature control the pacemaker rate. The specific characteristic of each parameter determines its role within the algorithm. While the motion sensor yields a fast reaction following the onset or a change of stress intensity, central venous blood temperature corresponds better to body metabolism. An indication of increased exercise from the motion sensor results in an accordingly rapid increase in the pacing rate. Unless this increased exercise is confirmed by an increase in central venous blood temperature within 2 or 3 minutes, the new motion level will be assumed to be the new baseline motion value and the pace rate will return to a basic pacing rate. Prolonged inappropriate responses are therefore avoided. Longer lasting exercise, fever and nonphysiological signals are recognized and handled safely. Exercise tests with five volunteers under various conditions showed pacing rate behavior that was close to normal.

Several studies have shown that the capability for exercise can be increased in patients with pacemakers by means of adjusting the rate. Respiration is one of the parameters considered for rate control. The aim of our study was to determine how respiratory parameters such as ventilation, tidal volume, and respiratory rate are capable of controlling the pacemaker rate, especially when measured indirectly by means of impedance plethysmography. We examined four volunteers and eight patients with implanted cardiac pacemakers using bicycle ergometry at increasing work loads. We recorded heart rate, uptake of oxygen, and ventilation directly (by pneumotachygraphy) and indirectly (by chest wall impedance plethysmography). A good correlation of directly to indirectly measured ventilation (r = 0.8687) was found. Our study suggests that respiratory minute volume is more appropriate for rate control of physiologic pacemakers than tidal volume or respiratory rate alone. Measurement by means of impedance plethysmography is sufficiently precise to be used for this purpose. Further studies must be conducted as to the optimum realization within an implantable device.