Controlled shear filtration: A novel technique for animal cell separation.

A novel rotary microfiltration technique specifically suited for the separation of animal cells has been developed. The concept allows the independent adjustment of wall shear stress, transmembrane pressure, and residence time, allowing straightforward optimization of the microfiltration process. By using a smooth, conically shaped rotor, it is possible to establish a controlled shear field in which animal cells experience a significant hydrodynamic lift away from the membrane surface. It is shown in preliminary experiments that shear-induced cell-rupture speeds up membrane clogging and that cell debris poses the most significant problem in harvesting of BHK cell cultures by dynamic microfiltration. However, a threshold value of shear stability exists which depends on the frequency of passing the shear field, the residence time in the shear field, as well as on cell status. By operating close to this threshold value, cell viability can be maintained while concentration polarization is efficiently minimized. By applying this concept, it is possible to attain flux rates several times higher compared to conventional crossflow filtration. Controlled shear filtration (CSF) can be used for batch harvesting as well as for cell retention in high cell density systems. In batch harvesting of hIL-2 from rBHK cell culture, a constant flux rate of 290 L h-1 m-2 has been adjusted without indication of membrane clogging or fouling.

Changing trends for surgical standby in patients undergoing percutaneous transluminal coronary angioplasty.

In 1988 the American College of Cardiology/American Heart Association (ACC/AHA) task force subcommittee on Guidelines for Percutaneous Transluminal Coronary Angioplasty (PTCA) recommended that an experienced cardiovascular surgical team be available within the institution for emergency surgery for all angioplasty procedures. The subcommittee felt strongly that this requirement allowed for no exception, stating that it could not condone existing arrangements that required the transportation of patients to off-site surgical facilities for emergency cardiac surgery. Such arrangements failed to meet the necessary standards of care exercised by prudent physicians. Interventional cardiologists are recognizing that it may be prudent for the ACC/AHA task force to revise its 1988 guidelines. Improved operator technique and new technologic advances, such as lasers, atherectomy devices, stents, and perfusion pumps and balloons, have helped extend the reach of PTCA to more seriously ill patients. With new technologies for angioplasty and an increased awareness of risk factors, active standby can be markedly reduced, thereby resulting in enormous cost reductions and in more appropriate patient care.

Coronary angioplasty in high-risk patients with left main coronary stenosis: results from the National Registry of Elective Supported Angioplasty.

To assess the outcome of PTCA in circulatory supported patients with left main coronary artery (LMCA) stenosis, the National Registry of Elective Supported Angioplasty data bank was searched. Patients entered in the registry were considered high-risk PTCA and the PTCA was performed using percutaneous cardiopulmonary bypass (PCPB). Criteria for high risk was left ventricular ejection fraction less than or equal to 25% or a target lesion supplying greater than or equal to 50% of functioning myocardium. Of 455 patients entered in the registry, 61 (13.3%) had LMCA stenosis greater than or equal to 60%. There were 42 patients in whom the PTCA target vessel was the LMCA (PTCA-LMCA) and 19 in whom it was vessel(s) other than the LMCA (PTCA-OTHER). The mean age was similar in the 2 groups (65 +/- 10 vs. 68 +/- 9 yrs, p = ns). The left ventricular ejection fraction (LVEF) was higher in PTCA-LMCA than in PTCA-other (38 +/- 16% vs. 27 +/- 16%, p less than 0.05). The number of vessels dilated/patient was higher in PTCA-LMCA than in PTCA-OTHER (2.1 +/- 1.0 vs. 1.1 +/- 0.3, p less than 0.001). There were a total of 10 in-hospital deaths (16%) in patients with LMCA greater than or equal to 60% stenosis. This exceeds the mortality of the patients with less than 60% LMCA stenosis entered in the registry (4.5%, p less than 0.001). There were 6 in-hospital deaths (14%) in PTCA-LMCA and 4 (21%) in PTCA-OTHER (p = ns).(ABSTRACT TRUNCATED AT 250 WORDS)

Management of acute myocardial infarction 1990: a perspective.

Rising costs have reached a point at which physicians must assume a major role in dealing with the cost of medicine. Little information is available regarding actual practice at the community hospital level. In order to develop some insight on this issue, a survey of cardiovascular specialists was conducted regarding management of acute myocardial infarction in 1990. The results indicate a major lack of correlation between efficacy, cost, and practice patterns in terms of current knowledge. Perhaps legal concerns have contributed to these current practice patterns. Clearly, aside from choice of thrombolytic agent and/or PTCA, early treatment of acute myocardial infarction has emerged as a most important factor in reducing mortality.

Percutaneous (nonsurgical) supported angioplasty in unprotected left main disease and severe left ventricular dysfunction.

A 69-year-old patient with the equivalent of severe, unprotected left main coronary artery disease associated with marked left ventricular dysfunction with ventricular aneurysm who had Class IV angina, underwent supported angioplasty utilizing a total percutaneous approach. The patient tolerated occlusion of his main left coronary artery for a total of 7 minutes without difficulty, during dilatation of left anterior descending and two circumflex lesions. He was discharged the following day, symptom free.

Intravenous streptokinase in acute myocardial infarction at the community hospital: a six-year experience.

The efficacy of intravenous streptokinase in the initial management of acute myocardial infarction was evaluated over a 6-year period in 130 patients admitted to 3 community hospitals. Most patients were admitted within 2 hours of onset of symptoms and received 1.5 million units of streptokinase over a 30- to 60-minute period. Clinical observations and serial creatine phosphokinase-MB were indicative of vessel patency in 115 (88%) of the patients after initiation of thrombolysis. Of this group, 105 underwent catheterization, and recanalization was demonstrated in 97 (92%). Fifty percent of the patients who underwent reperfusion were subsequently maintained with medical therapy; 50% underwent either percutaneous transluminal coronary angioplasty or coronary artery bypass surgery. Major morbidity was confined to hematomas; no cerebral bleeding was encountered. There was 1 early death from cerebral thrombosis and 2 late deaths, 1 to cancer and 1 to myocardial infarction. These findings suggest the benefit of intravenous streptokinase thrombolysis in patients with acute myocardial infarction presenting within 3 hours of onset of pain, unless specific potential bleeding problems exist or in the case of certain very elderly persons. In addition, the trial demonstrated the feasibility of triaging patients who have undergone lytic therapy to a central facility for catheterization and management.

Left ventricular pseudoaneurysm secondary to infection after coronary bypass surgery.

We present a case of left ventricular pseudoaneurysm following coronary bypass surgery. The cause was infection, dating from the bypass procedure 1 1/2 years before. Repair of pseudoaneurysm in a patient with a bypass is complicated by the presence of grafts which should be protected from injury. Details of successful management in this case are presented.

Congenital unilateral absence of the left pulmonary artery. Echocardiography in reverse.

This study demonstrates that when the heart is markedly displaced posteriorly to the left, or perhaps to the right, the posterior approach may make echocardiographic evaluation possible. Thus, in a patient with congenital unilateral absence of the left pulmonary artery, with marked displacement of the heart posteriorly, it was possible to obtain a satisfactory echocardiogram "in reverse" from the back, whereas no echoes were obtainable from the standard anterior positions.

Spontaneous closure of residual ventricular septal defect following surgical repair of ventricular septal defect complicating acute myocardial infarction.

Spontaneous closure of ventricular septal defects in patients with congenital heart disease is well documented. Also, successful closure of ventricular septal defects complicating myocardial infarction performed in the acute phase have been reported, although the mortality rate is high. Intra-aortic balloon pumping has been helpful in this regard, as it was in our patient. Our case is of interest in that it demonstrates the possibility of spontaneous closure of a residual ventricular septal defect resulting from rupture of the interventricular septum, secondary to acute myocardial infarction, partially closed at surgery. Clearly, the residual defect was small in that the patient was substantially benefitted by surgery and the postoperative catheterization revealed a small 5% step-up in oxygen saturation at the right ventricular level.