ABSTRACT
Rate-responsive pacemakers (PMs) aim at having pacing rates as similar to physiological cardiac rhythms as possible. The pacemaker INOS(2+)-CLS (Biotronik, Germany) implements a closed loop strategy (CLS) based on indirect measures of right ventricle contractility using intracardiac impedance signal. The contractility is, in turn, related to the autonomic nervous system control to the heart. Aim of this study was to evaluate the 24h beat-to-beat heart rate and blood pressure profiles in patients implanted with CLS rate adaptive PM. 24h ECG and arterial pressure waveform acquisition were performed by a digital Holter system by the Portapres equipment, respectively. A proper-designed algorithm was developed to classify PM pacing modalities. For each beat we estimated the heart rate (HR), and the systolic and diastolic pressure values (SP, DP). So far, 6 patients have been studied: 4 patients have been analyzed both with and without rate responsive modalities (DDD-R and DDD, respectively); 2 patients have been studied only with rate-responsive modality. Results obtained in 6 patients show that this rate adaptive PM accurately preserve the heart rate and blood pressure variability throughout the 24h. In particular, the rate adaptation of PM based on impedance measurements succeeds in maintaining the spontaneous HR, SP and DP on a beat-to-beat basis.
ABSTRACT
Light in the understory of a forest varies not only with season and solar elevation but also with vegetation dynamics. Seedlings of Schyzolobium parahybum (Vell) Blake, a fast-growing pioneer species, and Hymenaea stilbocarpa L., a slow-growing shade-tolerant species, were grown in pots for 90 days in a forest canopy gap (full sunlight) or in semi-shade (about 44% of full sunlight) beneath the canopy of a secondary forest. Both sites were located in Itaguai, RJ State, Brazil. Subsequently, half the seedlings grown in the canopy gap were moved to semi-shade and half the seedlings grown in semi- shade were moved to the canopy gap. After a further 90 days, seedling dry weight, height, leaf area, specific leaf area, leaf area ratio and concentration of chlorophyll a and b were measured. In response to increased irradiance, Schyzolobium parahybum responded by producing more leaf area, whereas Hymenaea stilbocarpa responded by increasing leaf mass per unit area and chlorophyll a concentration.
