Vascular Conduction Research Articles

An 85-Year-Old Women With a History of Falls-Reply

In Reply. —Dr Landau points out the risks of carotid sinus massage in elderly patients and warns that massage of the carotid sinus region carries a risk of permanent impairment and death. Indeed, there have been case reports of prolonged asystole, stroke, and ventricular fibrillation associated with carotid sinus massage. In many of these reports, the patients were quite ill or carotid massage was performed for as long as 15 seconds. In carefully selected patients without previous cerebral vascular disease or cardiac conduction disease, this procedure has been done quite safely, as long as the duration of massage does not exceed 5 seconds. There have been several studies suggesting that carotid sinus hypersensitivity may account for as many as one quarter to one half of episodes of unexplained falls and syncope in the elderly. 1,2 One study of 100 elderly nursing home patients showed that those with carotid sinus hypersensitivity had twice

BIOMECHANICAL PROPERTIES OF PERIPHERAL NERVES

The biomechanical properties of peripheral nerves still are not completely understood or quantified. This is partly because of the nonhomogeneous nature of nerves and the variation in the proportions of the components of different nerves. The recognition and quantification of the in-situ stress and the viscoelastic behavior of nerves have been important stepping stones in understanding their mechanical behavior. The effects of stretch and compression on the vascular supply and conduction properties of normal animal nerves have been well studied. Similar studies in injured nerves will provide invaluable information for understanding the mechanics of nerve function and the prevention of stretch- and compression-related trauma.

Vascular Occlusion and Cardiac Conduction Disturbances in a Patient Undergoing Peritoneal Dialysis

Vascular Occlusion and Cardiac Conduction Disturbances in a Patient Undergoing Peritoneal Dialysis

Late results (30 to 35 years) after operative closure of isolated ventricular septal defect from 1954 to 1960

This study was designed to determine the clinical status, cause of death, and effects of pulmonary vascular disease and conduction abnormalities 30 to 35 years after surgery in 296 consecutive surviving patients of closure of ventricular septal defect. Of the 296 patients, current status was determined by contact with patient and physician in 290 cases, with 6 (2%) lost to follow-up (7,912 patient years are included). Cardiac catheterization after surgery in 168 patients showed complete closure of the defect in 80%. Death occurred in 59 patients (20%), with higher mortality rates in those operated on after the age of 5 years, those with pulmonary vascular resistance >7 units (51%), and those with complete heart block (78%). Of 37 patients with transient heart block after surgery, 8 (22%) have died (3 pulmonary vascular disease, 2 sudden death, 2 unknown causes and 1 complete heart block). Twenty other patients had a dysrrhythmia after surgery, and none of these died. Nine episodes of endocarditis occurred ( 11.4 10,000 patient years). Nine of 296 (3%) offspring had cardiac malformation. Most patients are in New York Heart Association class I, 57% attended college and 15% received an advanced degree. The data show good results for this group of patients operated on during an early era (1954 to 1960) of open cardiac surgery. They support the current trend toward operation in patients with ventricular septal defects at an early age and with low pulmonary vascular resistance.

Hemodynamic and electrophysiologic effects of amlodipine, a new calcium channel blocker

The effects of amlodpine (300 μg/kg administered intravenously), a new, long-acting, dhydropyridne class, calcium channel blocking drug, were studied in atrially paced (120 beats/min), autonomicaly blocked dogs. Hemodynmnic and electrophysiologic parameters were measured before and up to 3 hours after amlodpine. Coronary blood flow was significantly increased 10 and 30 minutes after drug administration, whereas cardiac output and mean arterial pressure were unaffected. Coronary vascular resistance was decreased but total systemic vascular resistance did not change. Atrioventricular (AV) nodal conduction was slightly prolonged, as reflected by increases in strial-His bundle and AV conduction times and PR interval, 30 minutes after administration. AN parameters returned toward their control values within 3 hours after drug administration. Comparison of coronary vascular resistance and AV conduction changes with those previously reported for other calcium channel blocking drugs where autonomic blockade existed suggests that at equivalent levels of coronary vasodilation, amlodipine's effects more closely resemble the effects of ditiazem or verapamil than other dihydropyrtdines.

Side effects of calcium channel blockers.

Calcium channel blocking drugs are a chemically heterogenous group, so it might be expected that their effects on vascular smooth muscle, cardiac contractility, and conduction tissue may differ. However, the majority of adverse reactions are predictable from their pharmacological actions and may be conveniently grouped in the following categories: 1) vasodilatation, 2) negative inotropic effects, 3) conduction disturbances, 4) gastrointestinal effects, 5) metabolic effects, and 6) drug interactions. Vasodilatory symptoms, namely, dizziness, headaches, flushing sensation, and palpitation, are more likely with nifedipine. Peripheral edema is also common with nifedipine, but the mechanism is uncertain. For a given degree of vasodilation, the greatest negative inotropic effect is seen with verapamil first, diltiazem second, and nifedipine last. Calcium channel blocking drugs are contraindicated in hypertensive patients with second and third degree heart block, sick sinus syndrome, and severe heart failure. Verapamil and diltiazem have a significant effect on cardiac conduction, whereas nifedipine, in therapeutic doses, does not. Local gastrointestinal symptoms, such as nausea and constipation, are common with verapamil. None of the calcium channel blocking drugs have been reported to adversely affect lipid or protein metabolism. However, nifedipine, verapamil, and diltiazem in high doses may inhibit liberation of insulin. The significance of this finding needs to be explored further in hypertensive diabetics. Serum digoxin levels have been shown to increase after administration of verapamil and nifedipine, but there is no evidence that this change has any clinical relevance.(ABSTRACT TRUNCATED AT 250 WORDS)

An opiate component in realization of the vascular effects of clonidine

Systemic and regional hemodynamic changes (microsphere technique) were studied in urethan-chloralose anesthetized cats after intravenous clonidine and naloxone administration in different sequence. It was shown that antihypertensive effect of clonidine was caused by a decrease in the cardiac output and an increase in the total peripheral vascular conduction. The ability of clonidine to increase total peripheral conduction was completely blocked with naloxone preadministration. It was concluded that endogenous opiate receptors take part in the vasodilating clonidine effect in abdominal organs.

A model of glomerular ultrafiltration in the rat.

A model of glomerular ultrafiltration in the rat.

PIAL CIRCULATION AND SPREADING DEPRESSION OF ACTIVITY IN THE CEREBRAL CORTEX

PIAL CIRCULATION AND SPREADING DEPRESSION OF ACTIVITY IN THE CEREBRAL CORTEX