Biomedical subjects
Publications and source records attributed to R Forman.
The rate migration of an implanted cardiac pacemaker from the subrectus area anterior to the peritoneum to the pelvis following a motor vehicle accident is reported. Discovery of dislodgement was made by observing a marked increase of pacemaker impulse amplitude in the three standard limb leads as measured on an oscilloscope.
The actuarial survival and thromboembolic rates for the three types of cloth-covered Starr-Edwards mitral prostheses, models 6300, 6310/6320, and 6400 followed 6, 5, and 2 years, respectively, were not significantly different throughout the years they were followed. The combined cumulative survival and thromboembolic proportion at 5 years for these prostheses were 71 and 66 per cent, respectively. The thromboembolic rates were not different in the following two groups: (a) 238 patients receiving anticoagulants, and (b) 52 patients who had discontinued or who were not receiving anticoagulants. Four patients thrombosed their mitral prostheses. Another 8 per cent had class 3 symptoms after operation, which were attributed to myopathic or restrictive left ventricular dysfunction or other valvular disease.
The clinical and light and electron microscopic findings are reported in a 14-year-old patient who died 12 months after mitral valve replacement with a Hancock prosthesis. Severe cusp calcification had led to immobilisation of the valve and stenosis. Calcification involved the substance of the valve cusps. The cause of the calcification in this patient is unknown.
Twenty-six patients with Lillehei-Kaster prosthetic heart valves, 15 with aortic and 11 with mitral valves, were catheterized to assess their hemodynamic performance. The calculated effective orifice areas were linearly related to but always less than their actual orifice areas. There was no significant difference in the effective orifice area of the mitral or aortic prostheses of similar size. The aortic prosthesis with an annulus diameter of 21 mm. was found to have a mean effective orifice area of 0.77 sq. cm. Our catheter studies have demonstrated no hemodynamic advantages of the Lillehei-Kaster aortic and mitral prosthetic valves over prosthetic valves.
The results of valve replacement in 150 patients with Lillehei-Kaster aortic and mitral prostheses followed for 20 to 40 months are reviewed. Actuarial analysis showed 78 per cent cummulative thromboembolic-free rate three years following mitral valve replacement and 89 per cent following aortic valve replacement. Five patients had a total of six episodes of mitral valve thrombosis despite anticoagulant therapy. Early detection of mitral valve obstruction was difficult because a mid-diastolic murmur and absence of an opening sound was frequently encountered in normally functioning prostheses. Hemodynamic results assessed clinically in patients with nonthrombosed prostheses were satisfactory.
A young woman with unexplained radiographic calcification of the ascending aorta was found at necropsy to have healed idiopathic aorititis. Calcification also involved the aortic valve which was stenosed and the mitral valve. Death was the result of infective endocarditis of these valves with aortic ring abscess, rupture of aortic root, and cardiac tamponade.
Explore the source record for details and available documents.
The effects of both intracoronary and intravenous administration of nitroglycerin on transmural distribution of blood flow in the left ventricle after partial coronary artery occlusion was investigated using two independent methods. In 16 open chest, anesthetized dogs, tubing supplying the cannulated left coronary artery was partially occluded. Strain gauges sutured paralled to superficial and deep fibers of the myocardium separately recorded the contractile force of each layer. With occlusion set so that depression of the deep contractile force was imminent. 12 mug intracoronary nitroglycerin in seven dogs depressed only the deep contractile force without changing systemic hemodynamics. Intravenous administration of 180 mug nitroglycerin in nine dogs resulted in a decrease of deep contractile force and aortic pressure often associated with an increase in superficial contractile force. Distribution of myocardial blood flow during peak coronary flow after intracoronary administration of nitroglycerin or during a decrease in aortic pressure after intravenous nitroglycerin administration was determined by the tissue uptake of an intracoronary bolus of rubidium-(80). This was compared with the uptake of potassium-(42) injected before nitroglycerin. Intravenous or intracoronary administration of nitroglycerin caused a significant reduction in subendocardial blood flow with a decrease in the subendocardial/subepicardial ratio of isotope. These experiments suggest that under conditions of acute partial coronary occlusion, the autoregulatory response results in more fully dilated subendocardial vessels causing them to be less responsive to nitroglycerin. Nitroglycerin may then reduce the vascular resistance in the subepicardial more than the subendocardial vessels, resulting in a "steal" of blood flow from deep to superficial myocardium.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
We prospectively ascertained gestational cocaine use by neonatal urine and hair tests in 600 mother infant pairs in 3 nurseries in Toronto. The 37 (6.25%) babies who tested positive for cocaine and their mothers were compared to the 563 nonexposed with regard to pregnancy outcome and neonatal complications. Mothers using cocaine were not different in their ages, racial distribution, and obstetric history from those nonexposed. Cocaine-using women had significantly higher risk for vaginal bleeding (16% vs 6%, P < 0.05), hepatitis B carrier state (8% vs 0.8%, P < 0.005), and perhaps more urinary tract infections (8% vs 2.5%, P = 0.08). Cocaine-using mothers were significantly more likely to smoke cigarettes (29% vs 10%, P < 0.001). Infants exposed to cocaine in utero were of lower birth weight (3162 +/- 645 [SD] g vs 3391 +/- 573, P < 0.05) and birth length (49.9 +/- 2.9 cm vs 51.1 +/- 3.1 cm, P < 0.05). Further stratification of babies exposed to cocaine by maternal cigarette smoking suggests that cigarette smoking accounted for most of this variability [birth weight of babies exposed to cocaine and cigarettes 2899 +/- 7.50 g (and 50% of them weighed less than 2500 g), vs 3423 +/- 612 (and only 8% less than 2500 g) in those exposed to cocaine only (P < 0.05)]. Babies exposed to cocaine in utero were significantly more likely to need initial medical support or resuscitation (52% vs 30%, P < 0.05). We conclude that gestational exposure to cocaine, ascertained by a sensitive biologic marker, is associated with substantial perinatal risks.(ABSTRACT TRUNCATED AT 250 WORDS)
A series of electron microscopic immunocytochemical studies was performed to analyze subcellular sites for noradrenergic modulation in monkey prefrontal cortex. One out of 12 noradrenergic varicosities, identified by dopamine beta-hydroxylase immunocytochemistry within single ultrathin sections, forms morphologically identifiable junctions with small dendrites and spines. Accordingly, alpha2-adrenergic receptors, almost all of which are of the A-subtype, that occur in spines are localized discretely over postsynaptic membranes. alpha2-Adrenergic receptors are also found at sites along axons, dendritic shafts and astrocytic processes lacking morphologically identifiable synaptic junctions, suggesting that these receptors are activated by volume transmission. In particular, axonal alpha2-adrenergic receptors occur mostly at pre-terminal regions, suggesting that axo-axonic interactions may mediate reduction of neurotransmitter release at sites other than axo-spinous junctions by closing voltage-dependent calcium channels. These results indicate that noradrenergic modulation of prefrontal cortex involves synaptic interactions at spines of pyramidal neurons and nonsynaptic volume transmission to glia, dendritic shafts and axons.
Transcatheter bilateral uterine artery embolization is a relatively new, but fast increasing modality being offered as an alternative to surgery for the treatment of symptomatic uterine fibroids (myomata). Since its introduction in 1995, it is estimated that over 5000 procedures have been performed, despite little objective evidence of its efficacy in comparison with more traditional surgical procedures, e.g. hysterectomy, abdominal or laparoscopic myomectomy or hysteroscopic procedures. The enthusiastic uptake of uterine artery embolization is partly due to the fact that it can be performed as a day case, and is a means of avoiding surgery especially hysterectomy. However, the procedure is not without significant risks, and these are becoming clearer as more procedures are being reported. This review examines the procedure, its use and purported efficacy and discusses its complications and potential hazards.
Coronary flow reserve (CFR) provides essential information about the coronary microvascular bed in the absence of narrowing of epicardial coronary arteries. Experimental and human data suggest chronic heart failure is associated with a reduction of CFR in the absence of coronary artery disease. Dipyridamole, papaverine, or adenosine administration intravenously or intracoronary achieve maximal vasodilation of coronary arteries in human studies, however, systemic administration of vasodilator (dipyridamole) resulted in conflicting effects on systemic blood pressure. Various mechanisms including the nitric oxide pathway, neurohumoral alterations, and microvascular spasm among others, may contribute to the decrease in CFR in nonischemic heart failure. Notably, there is no study which describes the correlation between subjective symptoms of heart failure and the severity of the decrease in CFR. Further investigation of this area may be beneficial in determining the appropriate level of exercise training for heart failure patients and understanding mechanisms of the progression of heart failure. (c)1999 by CHF, Inc.