WE have recently studied 2 patients with symptoms of cerebral ischemia in whom a reversal of blood flow through the left vertebral artery was demonstrated. In both cases the anatomic lesion producing the reversal of blood flow was a stenosis of the left subclavian artery proximal to the origin of the vertebral artery. The cause of the reversed flow in these circumstances can be attributed to a fall of pressure distal to the stenosis below that at the vertebral-basilar junction so that the pressure gradient in the vertebral artery is reversed. We had not previously encountered this phenomenon and were . . .

Reversal of Blood Flow through the Vertebral Artery and Its Effect on Cerebral Circulation

During the past decade, major progress has been made in the evolution of technology directed toward the accurate measurement of regional myocardial perfusion in patients. The deficiencies of some of the older methods (thermodilution and gas clearance) are better appreciated and improved approaches (Doppler catheters, positron-emission tomography, and digital subtraction angiography) have been developed. The new approaches should play a major role in research and for most applications the older methods will gradually be replaced. Efforts to bring these new methods to community hospitals and practicing cardiologists should be stimulated. Doppler catheters, positron-emission tomography, and digital-subtraction angiography are commercially available and Doppler catheters and digital-subtraction angiography could be easily incorporated into routine cardiac catheterization procedures. The Doppler catheter is the most inexpensive and probably the simplest to apply. In our opinion, routine measurements of coronary flow reserve will significantly improve the care of patients with coronary obstructive disease and other diseases that impair myocardial perfusion. If coronary reserve measurements are used frequently, patient selection for coronary angioplasty and bypass surgery will no longer depend entirely on visual assessment of percent diameter stenosis, a very poor criterion in many situations. Also, patients with chest pain syndromes, normal coronary vessels, and impaired coronary reserve will be identified and perhaps some effective treatment for this condition will be devised.(ABSTRACT TRUNCATED AT 250 WORDS)

Methods of measurement of myocardial blood flow in patients: a critical review.

A quantitative study of the hemodynamics in the living microvascular system.

Chronic occlusion of the circumflex branch of the left coronary artery was produced in dogs. All animals developed a collateral circulation fast and efficient enough to prevent myocardial infarction. Tracer microsphere experiments together with 133-Xenon studies showed a homogeneous distribution of flow over the entire left ventricle. Drug-induced coronary vasodilation caused a grossly non-homogenous distribution of coronary blood flow. The collateral dependent areas of the heart received much less blood than the areas which are supplied by normal arterial channels. Within the collateral-dependent area the endocardial myocardium received less blood than the epicardial layers. Previously well perfused areas can become underperfused during overperfusion of normal myocardium. Similar changes were not observed in hearts with normal coronary arteries. Nitroclycerine did not produce changes in blood flow in hearts with coronary artery occlusion. Consequently changes in the distribution of myocardial flow were not observed with this drug. A computer model is presented for the explanation of the experimental findings which facilitated the analysis of contributing factors.

Myocardial steal produced by coronary vasocilation in chronic coronary artery occlusion.

The propensity of elderly people to suffer from dose-dependent adverse drug reactions is well known. This may be largely related to reduced drug clearance. Changes in liver size and liver blood flow are probably the main reason for this decline in drug elimination with age. This review focuses on methods of measuring liver size and blood flow, on changes which have been reported in the elderly and on the clinical implications of these changes.

Age-related changes in liver size and hepatic blood flow. The influence on drug metabolism in the elderly.

The Rein “Thermostromuhr”,1 the best method available for measuring flow in unopened vessels, is limited to mean flow measurements. In this laboratory a new method was developed which can follow ra...

An Electromagnetic Flowmeter. Principle of the Method and its Application to Bloodflow Measurements

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An Electromagnetic Flowmeter. Principle of the Method and its Application to Bloodflow Measurements