Estimulação DDD em pacientes idosos / DDD pacing in elderly patients

Devido ao número crescente de pessoas idosas que são candidatas à estimulação, os fatores relacionados ao uso de marcapassos em idades avançadas têm importantes implicações clínicas. Neste estudo prospectivo, descrevemos nossa experiência com o implante e o seguimento de 66 pacientes com idade igual ou superior a 70 anos (média de 76 anos) e com marcapassos DDD, com a finalidade de avaliar a ocorrência de complicações, a estabilidade da estimulação DDD e a qualidade de vida. O tempo médio até o último seguimento foi de 10,5 meses, com variação de 326 meses. Na maioria dos casos, a qualidade de vida dos pacientes melhorou significantemente após o implante. Dois marcapassos (3,3por cento) foram reprogramados para o modo VVI em decorrência de fibrilação atrial. Cinco pacientes (7,5por cento) tiveram complicações relacionadas ao eletrodo atrial, sendo que em dois foi necessária a reoperação. Sessenta e um dos 66 pacientes (92,5por cento), cujo estado era minuciosamente conhecido em fevereiro de 2000, permaneceram funcionalmente no modo DDD até o último seguimento. Concluímos que a estimulação de dupla-câmara é estável, apresenta baixo risco e pode melhorar a qualidade de vida em um grande espectro de pacientes idosos.

The relationship between renal sympathetic nerve activity and arterial pressure after selective denervation of baroreceptors and chemoreceptors

The relationship between an acute increase in arterial pressure and renal sympathetic nerve activity produced in rats under chloralose anesthesia after carotid and sinoaortic denervation was analyzed by quantifying the nerve activity associated with arterial pressure changes. After sinus denervation there was no change in arterial pressure (125 ñ 2.3 vs 124.6 ñ 5 mmHg, N +6), but the renal sympathetic nerve activity (10.8 ñ 0.9 vs 8.0 ñ 1.1 bars s-1 cycle-1, N+6) was significantly decreased. In spite of this, baroreflex control of renal sympathetic nerve activity was the same as during the control period. After sinoaortic denervation, there were simultaneous increases in arterial pressure (from 124 ñ 2.3 to 188 ñ 6m Hg, N +6) and renal sympathetic nerve activity (from 10.8 ñ 0.9 to 13.7 ñ 2.9 bars s-1 cycle-1) with marked attenuation of the baroreflexes. Spectral analysis of arterial blood pressure after sinus denervation showed a shift of a 1-Hz peak to 0.7 Hz, probably related to a respiratory frequency. The results suggest that after sinoaortic denervation the acute in arterial pressure is only due to aortic denervation

Regression pattern of amplitude of electrocardiographic waves during intravenous infusion in intact, buffer nerve denervated and spinal dogs.

Electrocardiographic (ECG) amplitude changes during clinically feasible rate of infusion of normal saline (NS), Ringer-Locke (RL) solution and tender coconut water (TCW) upto a dose of 100 ml/kg in paraldehyde (PLD) and chloralose and urethane (C&U) anaesthetised dogs were studied. The infusion caused a net decrease in P and QRS amplitudes but had varied effect on T wave amplitude in intact PLD and C&U anaesthetised dogs. Infusion of RL in vagotomised and/or carotid sinus (CS) denervated dogs and in spinal dogs indicated that these neural pathways had a significant effect on basal amplitude of ECG waves but their influence on infusion induced ECG changes was only marginal; in this the vagi seem to have a greater influence than the other pathways. The T wave changes during infusion were independent of simultaneous P and QRS changes and appeared to depend on the ionic composition of the infusion fluid. TCW infusion was very well tolerated, particularly by the C&U anaesthetised dogs. It would seem that the evaluation of ECG from patients on parenteral fluid be done in the context of the present observation that infusion per se decreases the amplitude of ECG.