Histologic analysis of tissue response to bucrylate-pantopaque mixture

A toxicologic-pathologic study of isobutyl-2-cyanoacrylate (Bucrylate) was carried out first in dogs and then in humans whose arteriovenous malformations were infused with this embolic agent. The canine specimens obtained at 7, 18, 28, and 147 days after embolization showed the development of a mild histiocytic giant cell reaction, which evolved to end-state sclerotic arteritis. The response was confined to the vessels and did not involve contiguous parenchymal tissues. Ten human specimens, obtained from 1 hr to 7 years after treatment, showed a similar bland reaction with no evidence of suppuration or premalignant changes.     

Flow dynamics for radiologists. II. Practical considerations in the live human.

Although the rules about flows seem complex and even at times suggest chaos, some general principles can be extracted and used by the radiologist. Normal arteries damp disturbances, tolerate our catheters well, and generally cause the blood''s slipstreams to swirl. It seems that the swirls and the energy that accompanies the passage of those swirls are prime determiners of the development of degenerative changes, most importantly of atherosclerosis and berry aneurysms. Knowing this, we now must direct our research to look beyond today''s practical applications and this simplistic summary. Radiologists who trained during the angiography era are often incredulous when they see the richness of information found in physiologic flow models. For years, contrast agents have hidden the elegant complexity of blood flow. Now, however, we have two new powerful machines: the Doppler gray-scale ultrasound and the MR scanner. These machines routinely demonstrate flow data that we do not as yet use. As angiographers we have a natural and unconscious bias to make images produced by our new machines look like the classic angiogram. It is a powerful and pervasive bias. We still call angiography our "gold standard." We must overcome that bias. As valuable as angiography has been to radiology, it may no longer be our benchmark. A new standard is ready to be developed. The MR scanner even now not only allows calculation of global flow in vessels but also analyzes individual slipstreams. The images shown here are only the beginning. Keep our old mindset, and the limits and utility of the MR scanner will not be explored by radiologists. However, if we physicians, especially radiologists, reenter the field of fluid dynamics, all of science and our patients will benefit. We have broad shoulders to stand on and see into the future. Harvey, Hales, Galen, and Poiseuille: all were physicians; they added immeasurably to the foundations of rheology and our understanding of flowing blood. We must be willing to do likewise.     

In vitro analysis of boundary identification techniques used in quantification of two-dimensional echocardiograms

Echocardiographic cross-sectional areas of 10 formalin-fixed animal left ventricles were determined by 5 independent observers using black-white (B-W) and mid-spot (M-S) endocardial boundary identification techniques. The echocardiographic cross-sectional areas were compared with the true anatomic cross-sectional areas of the same 10 hearts to determine the accuracy, variability and reliability of each technique. The results of these comparisons revealed that the M-S technique was more accurate than the B-W technique (3.3 +/- 7.2 vs 34.9 +/- 8.6% error). However, the B-W technique was more reliable in that it had a smaller interobserver and estimated intraobserver variability. The M-S technique had a 6% greater intraobserver variability.     

Comparative effects of catecholamines in cardiac tamponade: Experimental and clinical studies

In experimental cardiac tamponade, catecholamines improve hemodynamic variables. To determine whether hemodynamic changes result in increased blood flow to critical organs, tamponade was produced in nine spontaneously breathing, anesthetized dogs. Infusion of dopamine, isoproterenol or norepinephrine doubled cardiac output, but only norepinephrine increased mean arterial pressure. All catecholamines increased blood flow to the myocardium, but not to the brain or kidney. Isoproterenol caused a significant decrease in the endocardial/epicardial blood flow ratio, which was shown to be due to tachycardia.To determine whether catecholamines increase cardiac output and mean arterial pressure in patients with tamponade, eight patients with tamponade due to neoplasms were studied before therapeutic pericardiocentesis. Cardiac output increased only 50 percent with dopamine and isoproterenol and not at all with norepinephrine. Cardiac filling pressure did not decrease with isoproterenol or dopamine, as in experimental tamponade. Only norepinephrine increased mean arterial pressure.Thus, although catecholamines improve hemodynamics in experimental tamponade, the heart is the only critical organ to which blood flow is improved. The hemodynamic benefits of catecholamine administration to patients may be more limited than previous experimental studies have suggested.     

Characterization of acute experimental left ventricular thrombi with quantitative backscatter imaging

Two-dimensional echocardiography is an excellent technique for detecting left ventricular thrombi, however, acute clot is sometimes difficult to differentiate from adjacent myocardium and intracavitary signals. We hypothesized that quantitative assessment of the acoustic properties of acute left ventricular thrombi using a quantitative backscatter imaging system would permit the differentiation of thrombus from adjacent myocardium and intracavitary echoes. Acute, experimental left ventricular thrombi in seven dogs were evaluated with a quantitative backscatter imaging system that allowed the measurement of relative integrated backscatter and cyclic (i.e., diastolic minus systolic) variation in integrated backscatter. Coronary ligation abolished the cyclic variation in relative backscatter that occurred in normal myocardium. The end-diastolic relative backscatter in the thrombus (16.9 +/- 1.3 dB) was significantly higher than in apical myocardium (13.2 +/- 0.6 dB, p less than 0.05). There was no significant difference in the cyclic variation in relative backscatter among thrombus, ischemic myocardium, or intracavitary blood. Thus, the quantitative assessment of the acoustic properties of left ventricular thrombi can be useful in their detection and in the differentiation from myocardium and intracavitary signals.