A forgotten cause of wide complex tachycardia.

Wide complex tachycardia secondary to an acute overdose from TCA's is a well-documented phenomenon. In this case we present a wide complex tachycardia after clear documentation of no acute overdose, which responded to standard treatment for TCA toxicity. These findings combined with chronic electrocardiographic abnormalities were suggestive of an acute on chronic TCA toxicity.

Muscle interstitial calcium during head-up tilt in humans.

Background: During head-up tilt (HUT), peripheral vasoconstriction occurs. This response requires appropriate communication between the sympathetic nerve terminal and vascular smooth muscle cell in the neurovascular space. Both of these cell types require extracellular calcium ([Ca2+]o) for proper activation and function.

Oral class III antiarrhythmics: what is new?

Purpose Of Review: This review describes the latest developments in the clinical usage of class III antiarrhythmics. It also discusses some new studies providing insight into the mechanism of action of these drugs.

Recent Findings: New data suggest that amiodarone is one of the most effective drugs for management of ventricular as well as supraventricular tachyarrhythmias.

Autonomic and vascular responses to reduced limb perfusion.

The purpose of this study was to examine hemodynamic responses to graded muscle reflex engagement in human subjects. We studied seven healthy human volunteers [24 +/- 2 (SE) yr old; 4 men, 3 women] performing rhythmic handgrip exercise [40% maximal voluntary contraction (MVC)] during ambient and positive pressure exercise (+10 to +50 mmHg in 10-mmHg increments every minute). Muscle sympathetic nerve activity (MSNA), mean arterial blood pressure (MAP), and mean blood velocity were recorded.

Aging and the exercise pressor reflex in humans.

Background: Blood flow limitation to exercising muscles engages the muscle reflex during exercise, evoking an increase in heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA).

Methods And Results: In the current study, we examined forearm flow and autonomic responses to ischemic handgrip in young and older subjects. We studied 6 younger subjects (mean age 23.

Effects of graded LBNP on MSNA and interstitial norepinephrine.

Exposure to lower body negative pressure (LBNP) leads to an increased activation of the sympathetic nervous system (SNS) and an increase in muscle sympathetic nerve activity (MSNA). In this study, we examined the relationship between MSNA and interstitial norepinephrine (NE(i)) concentrations during LBNP. Twelve healthy volunteers were studied (26 +/- 6 yr).

Attenuated sympathetic nerve responses after 24 hours of bed rest.

Bed rest reduces orthostatic tolerance. Despite decades of study, the cause of this phenomenon remains unclear. In this report we examined hemodynamic and sympathetic nerve responses to graded lower body negative pressure (LBNP) before and after 24 h of bed rest.