Is sinus node modification appropriate for inappropriate sinus tachycardia with features of postural orthostatic tachycardia syndrome?

Inappropriate sinus tachycardia and postural orthostatic tachycardia are ill-defined syndromes with overlapping features. Although sinus node modification has been reported to effectively slow the sinus rate, long-term clinical response has not been adequately assessed. Furthermore, whether patients with postural orthostatic tachycardia would benefit from sinus node modification is unknown.

Electrophysiologic characteristics of diverse accessory pathway locations of antidromic reciprocating tachycardia.

This study assessed antidromic reciprocating tachycardia (ART) in patients with paraseptal accessory pathways (APs). Previous clinical experience suggests that paraseptal APs are unable to serve as the anterograde limb during ART. Based on the reentry wavelength concept, we hypothesized that anatomic location of a paraseptal AP may not preclude occurrence of ART.

Vasovagal syncope.

Background: Vasovagal syncope is the most common type of syncope and is one of the most difficult types to manage.

Purpose: This article reviews the status of mechanisms, diagnosis, and management of vasovagal syncope.

Data Sources: MEDLINE search for English-language and German-language articles on vasovagal syncope published up to June 1999.

Clinical, genetic, and expression studies of mutations in the potassium channel gene KCNA1 reveal new phenotypic variability.

Episodic ataxia type 1 (EA1) is an autosomal dominant central nervous system potassium channelopathy characterized by brief attacks of cerebellar ataxia and continuous interictal myokymia. Point mutations in the voltage-gated potassium channel gene KCNA1 on chromosome 12p associate with EA1. We have studied 4 families and identified three new and one previously reported heterozygous point mutations in this gene.

Distinct hemodynamic profiles in patients with vasovagal syncope: a heterogeneous population.

Objective: The objective was to investigate mechanisms of vasovagal syncope by identifying laboratory techniques that characterize cardiovascular profiles in patients with vasovagal syncope.

Background: The triggering mechanisms of vasovagal syncope are complex. The patient population is likely heterogeneous.

Global right atrial mapping of human atrial flutter: the presence of posteromedial (sinus venosa region) functional block and double potentials : a study in biplane fluoroscopy and intracardiac echocardiography.

Background: Previous studies of atrial flutter have found linear block at the crista terminalis; this was thought to predispose the patient to the arrhythmia. More recent observations, however, have demonstrated crista conduction. We sought to characterize the posterior boundary of atrial flutter.

Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy.

Background: Hypertrophic cardiomyopathy is a genetic disease associated with a risk of ventricular tachyarrhythmias and sudden death, especially in young patients.

Methods: We conducted a retrospective multicenter study of the efficacy of implantable cardioverter-defibrillators in preventing sudden death in 128 patients with hypertrophic cardiomyopathy who were judged to be at high risk for sudden death.

Results: At the time of the implantation of the defibrillator, the patients were 8 to 82 years old (mean [+/-SD], 40+/-16), and 69 patients (54 percent) were less than 41 years old.

Mitochondria exert a negative feedback on the propagation of intracellular Ca2+ waves in rat cortical astrocytes.

We have used digital fluorescence imaging techniques to explore the interplay between mitochondrial Ca2+ uptake and physiological Ca2+ signaling in rat cortical astrocytes. A rise in cytosolic Ca2+ ([Ca2+]cyt), resulting from mobilization of ER Ca2+ stores was followed by a rise in mitochondrial Ca2+ ([Ca2+]m, monitored using rhod-2). Whereas [Ca2+]cyt recovered within approximately 1 min, the time to recovery for [Ca2+]m was approximately 30 min.

Sensitivity to orthostatic stress and beta-receptor activation in patients with isoproterenol-induced vasovagal syncope: a case controlled study.

Cardiomotor and vasomotor responses were assessed during isoproterenol tilt-induced vasovagal reaction in patients with a history of syncope. In a case controlled study, all patients and controls were subjected to a standard protocol: baseline supine (10 min), baseline tilt (70 degrees, 45 min), isoproterenol supine (0.05 microgram/kg per min, 10 min), and isoproterenol tilt (70 degrees, 10 min).

Utility of a single-stage isoproterenol tilt table test in adults: a randomized comparison with passive head-up tilt.

Objectives: This study was conducted to develop a time-efficient tilt table test.

Background: Current protocols of tilt table testing are quite time-consuming. This study was designed to assess the diagnostic value, tolerance and procedural time of a single-stage isoproterenol tilt table protocol.

A test of the "epinephrine hypothesis" in humans.

-According to the "epinephrine hypothesis," circulating epinephrine taken up by sympathetic nerves is coreleased with norepinephrine during sympathetic stimulation and binding of coreleased epinephrine to presynaptic beta-adrenoceptors augments exocytotic release of norepinephrine, contributing to high blood pressure. This study examined whether infusion of a physiologically active amount of epinephrine affects subsequent vascular responses and the estimated rate of entry of norepinephrine into regional venous plasma (norepinephrine spillover). Each of 3 experiments included intravenous infusion of 3H-norepinephrine, measurements of forearm vascular resistance, and intra-arterial infusion of epinephrine (3 ng/min per deciliter forearm volume).

[Ultra-low laparoscopic rectal resection and colo-anal anastomosis. Experimental study on swine].

Nowadays oncologic surgery is defining new criteria in the treatment of rectal cancer: preservation of sfincterial function, ultra-low resections with distal margin at only 2 cm distally to the tumor, role of mesorectum as preferential site of lymphatic diffusion, preservation of lombo-aortic and pelvic nerves. Laparoscopy is showing good results in bowel surgery so as previously got on biliary tract: less visceral manipulation, less stimulation of immunologic system, less pain, early resumption of peristalsis and food intake, better recovery, less hospital stay. We experimented on pig ultra-low laparoscopic resection of the rectum, with preservation of sfincterial function, and mechanical anastomosis at the upper edge of the sfincterial ring.

Modulation of human sympathetic periodicity by mild, brief hypoxia and hypercapnia.

We determined the influence of brief mild normocapnic hyperoxia, hypoxia, and hyperoxic hypercapnia on human muscle sympathetic nerve activity and R-R intervals, as quantified by both time- and frequency-domain analyses. We obtained measurements in nine healthy young adult men and women during uncontrolled and frequency (but not tidal volume) controlled breathing. Responses were evaluated with forward selection and backward elimination statistical models, with muscle sympathetic nerve activity as the dependent variable, and power spectral techniques.

Role of arterial chemoreceptors in mediating the effects of endogenous adenosine on sympathetic nerve activity.

Background: Exogenous adenosine has been shown to increase muscle sympathetic nerve activity (MSNA), blood pressure, heart rate, and ventilation in conscious humans, effects attributed to peripheral chemoreceptor activation.

Methods And Results: To determine whether endogenous adenosine has similar effects and whether they are mediated through chemoreceptor activation, we examined the effects of dipyridamole, an inhibitor of adenosine reuptake, on sympathetic nerve activity and ventilation. Twenty studies were conducted on separate days in 15 healthy volunteers.

Effects of fludrocortisone on sympathetic nerve activity in humans.

Fludrocortisone reduces plasma norepinephrine in healthy humans, but forearm vascular and pressor responses to norepinephrine are potentiated. The effects of fludrocortisone on sympathetic nerve activity in healthy humans are not known. To investigate these effects we evaluated muscle sympathetic nerve activity, heart rate, and arterial pressure in 11 healthy volunteers during three protocols: (1) before and on day 7 of fludrocortisone (0.

[Segmental liver transplantation. Experimental studies in swine].

Authors report the results of an experimental application of one of the more recent techniques of liver transplantation, which has the preparation ex situ as a basilar step of the procedure. 18 pig were operated on, from september 1991 to march 1993; they were divided in two groups: the first (group A) underwent an auxiliary segmental autotransplantation of left lobe to heterotopic subdiaphragmatic location; in group B an orthotopic segmental autotransplantation of right lobe after ex situ preparation of the liver according the technique of Pichlmayr was performed. The results show that a bigger application of ex situ surgery may help to find a resolution to the problem of the small number of liver donation.

Neural control mechanisms and vasovagal syncope.

Patients with recurrent unexplained syncope may have cardioinhibitory and vasodepressor responses provokable with head-up tilt with or without exogenous beta-adrenergic stimulation. Although these responses are believed to be neurally mediated, the neural mechanisms involved are poorly understood. Numerous studies have documented peripheral vasodilation, hypotension, and bradycardia at the time of syncope and several case reports have shown sudden withdrawal of vasoconstrictor sympathetic neural outflow to skeletal muscle in human subjects.

[Accidents and injuries in 4 general hospitals of the Distrito Federal].

We report the injuries for "E" code in 10191 subjects attending four general hospitals of Mexico City. Seventy-nine per cent of them were males and 29.1 per cent were females.

Alterations in reflex function contributing to syncope: orthostatic hypotension, carotid sinus hypersensitivity and drug-induced dysfunction.

Orthostatic hypotension and related neurologic symptoms are frequently encountered in clinical practice. The maintenance of appropriate blood pressure and heart rate responses upon assuming the upright posture are dependent upon: 1. intact mechanical (venous valves) mechanisms, 2.