[Ergospirometric findings in respiration- and QT-controlled pacemakers]

This study used ergospirometry with quantification of gas exchange parameters to analyze the beneficial effects of two sensors for rate responsive pacing: QT-interval and minute ventilation (MV). Bicycle exercise testing was performed with modulating VVIR pacing modes in random sequence. Rate responsiveness effected a mean increase of exercise tolerance of 31.1% in the QT group and 22.6% in the MV group. With both systems maximal oxygen uptake increased by 29.4% (QT) and 28.3% (MV). Oxygen consumption at the anaerobic threshold was improved by 28.3% (QT) and 32.1% (MV). The increase of cardiopulmonary parameters achieved by rate responsiveness was significant (p < 0.05) without significant difference in comparison between both groups. Despite the initially delayed rate increase at the onset of exercise mediated by the QT-interval, the programmed upper rate limit was satisfactorily attained by both principles. Thus, both sensors--minute ventilation and QT-interval--provide an adequate rate modulation in response to exercise and a marked improvement of cardiopulmonary work capacity.