Respiratory Rate as a Determinant of Optimal Pacing Rate

Des essais ont été faits dans ľutilisation des paramètres bialogiques pour déterminer la fréquence optimale de stimulation cardiaque. Dans cette étude, le rapport entre fréquence respiratoire et fréquence cordiaque a étéétabli chez 67 patients au cours de ľexercice. Ensuite, un système de stimulation cardiaque qui repondrait àľactivation radiotélémétrique a été posé chez onze patients. Dans deux cos un système automatique a été implanté avec succès. A present, les résultats de cette stimulation pilotée par la fréquence respiratoire sont satisfaisants.
Efforts have been made to utilize biologic parameters for determining optimal cardiac pacing rates. In this study of 67 patients, a significant relationship between heart rate and respiratory rate was observed during dynamic exercise. A system using a radiofrequency activator to modify pacing rate is described. Eleven patients have received VVI pacemakers with a similar implanted radioreceiver coil. In two patients the fully automatic system has been successfully implanted. The experience with respiratory rate as a determinant of pacing rate is encouraging.     

PULMONARY CLEARANCE OF ANAESTHETIC AGENTS A Theoretical Study

The pulmonary clearance of anaesthetic agents (Cl) representsa useful index of their elimination from the lungs. Its valuedepends on pulmonary blood flow ("), alveolar ventilation (VA),and anaesthetic blood solubility () according to equation: Cl= (VAQ)/(VA+Q). When the alveolar ventilation and pulmonaryblood flow are constant the pulmonary clearance of the anaestheticdepends on its blood solubility. In this case the lower theblood solubility is, the higher the value of pulmonary clearancebecomes. For each anaesthetic agent a change in alveolar ventilationor in pulmonary blood flow will produce a change in pulmonaryclearance which in its turn depends on anaesthetic blood solubility.When = (VA/Q)² a change in alveolar ventilation or in pulmonaryblood flow will affect the pulmonary clearance to the same extent.When the anaesthetic blood solubility value is higher than (VA/Q)²,its pulmonary clearance is predominantly affected by alveolarventilation, and when anaesthetic blood solubility is lowerthan (VA/Q)² its pulmonary clearance is predominantly dependenton pulmonary blood flow. Changes in pulmonary clearance producedby changes in alveolar ventilation (/VA) are larger with halothane,nitrous oxide and cyclopropane than with agents of greater blood-gassolubility at all VA/Q ratios in the range 0.5—2.0.     

Increasing Cardiac Rate by Tracking the Respiratory Rate

Un stimulateur asservi qui utilise la fréquence venlilatoire comme capteur a été implunté chez 22 patients, dont 19 pour la stimulation ventriculaire et 3 pour la stimulation auriculaire. Le niveau d'exercice atteint en utilisant ce système a été toiijours supérieur à celui de la stimulation ventriculaire à fréquence fixe. En plus, aucun capteur chimique ou mécanique n'était utilisé; le capteur même est simple, durable et utilise une faible énérgie. Done, ce système s'adapte facilement à chaque patient individuel.     

A New Approach to the Prevention of Endless Loop Tachycardia in DDD and VVD Pacing

Endless loop tachycardia (ELT) is a possible complication in dual chamber pacing; it is usually prevented by programming the atrial refractory period (PVARP) longer than the retrograde ventriculoatrial (VA) conduction interval; this in some patients limits the upper rate. In 15 patients with a DDD (nine patients) or a single-pass lead VDD pacemaker (six patients) and retrograde atrial activation, telemetric recording documented a significant difference in amplitude of antegrade, and retrograde atrial potentials (VDD 1.21 ± 0.32 mV vs 0.56 ± 0.23 mV, P = 0.008; DDD 2.7 ± 1 vs 1.8 ± 1 mV, P - 0.038; Student's t-test for paired data). In 3/15 patients ELT stopped after programming of atrial sensitivity to a value. greater than the retrograde P wave amplitude; in 11/15 patients this occurred at a sensing value lower than or equal to retrograde P wave amplitude with a high pass band filter operating. One patient required PVARP lengthening. Holter monitoring showed no more ELTs. In most patients with a DDD or single-pass lead VDD pacemaker with widely programmable sensing amplitude and Hi/Low bandpass filters. individual programming of atrial channel sensitivity prevents ELT without affecting the PVARP and, consequently, upper rate limit.     

Peripheral nerve regeneration and neurotrophic factors

The role of neurotrophic factors in the maintenance and survival of peripheral neuronal cells has been the subject of numerous studies. Administration of exogenous neurotrophic factors after nerve injury has been shown to mimic the effect of target organ-derived trophic factors on neuronal cells. After axotomy and during peripheral nerve regeneration, the neurotrophins NGF, NT-3 and BDNF show a well defined and selective beneficial effect on the survival and phenotypic expression of primary sensory neurons in dorsal root ganglia and of motoneurons in spinal cord. Other neurotrophic factors such as CNTF, GDNF and LIF also exert a variety of actions on neuronal cells, which appear to overlap and complement those of the neurotrophins. In addition, there is an indirect contribution of GGF to nerve regeneration. GGF is produced by neurons and stimulates proliferation of Schwann cells, underlining the close interaction between neuronal and glial cells during peripheral nerve regeneration. Different possibilities have been investigated for the delivery of growth factors to the injured neurons, in search of a suitable system for clinical applications. The studies reviewed in this article show the therapeutic potential of neurotrophic factors for the treatment of peripheral nerve injury and for neuropathies.     

Skin Angiosarcoma Arising in an Irradiated Breast: Case-Report and Literature Review

BACKGROUND: Angiosarcoma (AS) is a rare, invasive malignancy originating from endothelial cells caused by many different clinical situations. AS following radiotherapy for breast cancer after conservative surgery is a rare but well-known association. OBJECTIVE: The aim of this article is to describe a case of AS after breast conserving surgery and to review the literature to date. RESULTS: We report the case of an 84-year-old woman who developed AS four years after she was subjected to quadrantectomy for invasive ductal cancer, followed by 30 tangent field radiotherapy sessions. She presented with a one-month history or red papular skin eruptions on the operated breast. Skin lesions were submitted for biopsy, and they were positive for AS. The patients was subjected to surgical excision of the remaining breast including all AS lesions. She is alive with no evidence of disease after 10 months follow-up. CONCLUSION: Post-radiotherapy AS is rare neoplasm, but it should be considered in the case of patients with red lesions after breast conserving surgery and adjuvant radiotherapy.     

Asymptomatic Superior Vena Caval Occlusion: A Complication of Nonthoracotomy Implantation of Cardioverter Defibrillator

A patient with ischemic dilated cardiomyopathy and history of ventricular fibrillation received an implantable Cardioverter defibrillator by the nonthoracotomy approach. Four years later, during elective replacement of an exhausted pulse generator, a superior vena caval thrombotic occlusion with collateral circulation through the azygos and emiazygos vein systems was documented. This occlusion occurred despite an anticoagulant treatment in the standard therapeutic range. We speculate that thrombotic occlusion might be secondary to a mechanical vessel injury.