Multicenter Evaluation of Fixed-Wire PTCA Catheters with Modified Distal Tips: Initial and 2-Month Follow-Up Results

Lesions in the distal portion of coronary arteries are technological challenges with currently available percutaneous transluminal coronary angioplasty (PTCA) equipment. A study was performed at multiple centers to determine if new "fixed-wire" devices with a modified distal tip (a 2-cm flexible tip and 1-cm standard tip) would be useful in these situations. Three hundred twenty-three patients were included in the study, 75% male, mean age 63 ± 11 years. Four hundred ninety-three lesions were attempted; the overall success rate was 85%. Forty-six (14.2%) clinical complications occurred including: 5 deaths (1.1%); 2 nonfatal myocardial infarctions (0.6%); and 6 emergency coronary artery bypass grafting procedures (2.6%). A device malfunction was noted in 32 patients (9.9%), and included: 8 balloon ruptures or perforations (2.0%); 6 bent or damaged tips (1.9%); and 4 shaft/manifold leaks (1.2%). Two-month follow-up assessment for restenosis was done in 352 of 371 (95%) patients and at that time 89% were asymptomatic, had a negative functional test, or patent PTCA site by angiography. The new fixed-wire PTCA catheters with 1- and 2-cm flexible tips hold promise for dilating lesions in distal locations with an acceptable rate of complications. Additional investigation is needed to determine their role in the treatment of coronary artery disease with PTCA.     

Health education and primary health care in Costa Rica: the role of the health assistant

Health status indicators for the population of Costa Rica comparedfavorably in the 1980s to those of more developed nations. Morbidityand mortality had been lowered, and health status differentialsbetween population subgroups had been narrowed. By 1984, mostof the objectives set by the World Health Organization had beenexceeded. These outcomes have been attributed to the successof a national primary health care program and to the role ofthe health assistant/asistente de salud in the operation ofthis program. This article examines the approach taken in achieving theseoutcomes. Of particular interest is the role of the health assistantas health educator in attaining the health promotion and diseaseprevention goals of the primary care program. Contemporary challenges which may diminish the role of the healthassistant and the possible consequences of this for public healthare considered, as is a recent government experiment which affordsa potential response to these issues. The latter, a new modelfor the organization and delivery of health services, featuresa partnership between government and a private sector providergroup. This arrangement retains the traditional role of thehealth assistant in primary care and enhances the health educationfunction of the health assistant. Under pressure and in transition, the health sector in CostaRica is striving to safeguard the admirable achievements ithas attained and to plan for further advances. It is clear thatunder present circumstances difficult choices must be made.One hopes that in the trade-offs made, those elements of theprimary health care program which have been essential to thisnation's success are not assigned a lower priority.     

Age-Dependent Prevalence of Cardioembolic Sources Detected by TEE: Diagnostic and Therapeutic Implications

To define the prevalence of cardioembolic sources found by transesophageal echocardiography (TEE) in different age groups of patients with and without cryptogenic systemic embolism, TEE risk factors for cardiogenic embolism were identified from 341 consecutive patients referred for TEE. One hundred and thirty-five had cryptogenic cerebral or systemic peripheral embolic events (CEE) and 206 other indications for TEE (CTR). Cardioembolic sources were found in 40% of CEE and in 29% of CTR (P < 0.02). Specifically, left atrial (LA) thrombi (P < 0.0001), atrial septal aneurysm with right-to-left shunt (P < 0.002), and atherosclerotic aortic plaques (P < 0.02) were more frequent. The prevalence of potential cardioembolic sources was significantly higher in patients ≥ 70-years old than in younger patients (P < 0.03), specifically LA thrombi (P < 0.004) and atherosclerotic aortic plaques (P < 0.0001). In patients ≥ 70-years old, potential cardioembolic sources were found in 63% and in 40% in CEE and CTR (P = 0.073), respectively. However, LA thrombi were more frequent in CEE (P < 0.003). Thus, potential cardioembolic sources observed by TEE are found more frequently in patients ≥ 70-years old than in younger patients. LA thrombi were more frequent in CEE than in CTR patients ≥ 70-years old. In patients ≥ 70-years old with CEE who are eligible for an anticoagulant regimen, a search for potential cardioembolic sources by TEE should be considered.     

The Inhalation Toxicology, Genetic Toxicology, and Metabolism of Difluoromethane in the Rat

Difluoromethane (HFC32) is under development as a replacementfor chlorofluorocarbons (CFCs) in some refrigeration applications.It has been evaluated by standard studies of toxicity, developmentaltoxicity, and genotoxicity. In addition, the metabolism anddisposition of HFC32 was investigated and a physiologicallybased pharmacokinetic (PB-PK) model constructed. Inhalationof HFC32 (up to 50,000 ppm) caused no organ-specific effects,but resulted in slight maternal toxicity to the pregnant ratand rabbit and some fetotoxicity to the rat. HFC32 did not sensitizethe heart to adrenaline. The pharmacokinetics of [¹⁴C]difluoromethane(10,000 to 50,000 ppm/6 hr) revealed that about 2.1% of theinhaled HFC32 was absorbed and that steady state blood levelswere achieved within 2 hr and were proportional to dose. Carbondioxide was the major metabolite of HFC32 at all exposure levels.Carbon monoxide was not detected. The in vivo data were usedto validate a PB-PK model to describe the uptake and metabolismof HFC32. Absorption and distribution are adequately describedusing rat blood:air and tissue:air partition coefficients. Metabolism,which was linear across the dose range, was described by a firstorder rate constant (K_f=8.98 hr^–1). Of the absorbed HFC32,about 63% was metabolized at all doses; however, when metabolismwas expressed as a percentage of the inhaled dose it was muchlower, being about 1.4% of the HFC32 entering the airways. Overall,the results indicate that HFC32 is of very low toxicity andshould be an acceptable alternative to CFCs.     

Alveolar Retention and Clearance of Insoluble Particles in Rats Simulated by a New Physiology-Oriented Compartmental Kinetics Model

Alveolar Retention and Clearance of Insoluble Particles in RatsSimulated by a New Physiology-Oriented Compartmental KineticsModel. STOBER, W., MORROW, P. E., AND MORAWIETZ, G. (1990).Fundam Appl. Toxtcol. 15,329–349. A physiology-orientedcompartmental kinetics model of alveolar retention of inhaledinsoluble paniculate matter in rat lungs was proposed in a recentpaper, (W. Stober, P. E. Morrow, and M. D. Hoover, 1989, Fundam.Appl. Toxicol. 13, 823–843), and the retention patternsobtained with the model for a hypothetical set of input dataappeared to simulate phenomena which were observed in inhalationstudies with Fischer 344 rats. The present paper representsthe results of applying the new model for simulations of theactual experimental retention data of five different inhalationstudies with Fischer 344 rats exposed to three different materials.The experimental data showed that model adjustments had to bemade in order to account for clearance effects that appearedto be influenced by the age of the animals. After these adjustmentswere made and an appropriate set of values for the model parametersdescribing the respective exposure conditions was used, themodel was constrained to represent the empirical data of allof the studies by one unique set of parameter values. Changesin particular values of this set were considered to be acceptableonly if they reflected changes of relevant properties of theinhaled paniculate matter. The final simulations did not completelycomply with this self-imposed criterion. However, the degreeof compliance and the simulation quality achieved with a minimumof parameter variations seem to be unprecedented in retentionmodeling. The results of the study encourage attempts for furtherrefining the present model