Biomedical subjects
Publications and source records attributed to V Parsonnet.
A case of Greenfield filter migration to the left pulmonary artery is presented and the pertinent literature reviewed. Technical points are made regarding the prevention and the management of proximal filter migration.
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A survey of physicians implanting pacemakers was conducted to obtain a profile of permanent cardiac pacing practices in the United States during 1981. Questionnaires were mailed to 5,832 implanters with 765 responses (13%) received and 680 analyzed. It was estimated that there were approximately 5,600 physicians, 66% surgeons and 34% nonsurgeons, implanting pacemakers at 3,670 centers. About 118,000 new primary implants were performed, or 518 per million population. Only 17% of implantation procedures in 1981 were replacements compared with 31% in 1978. Roughly half the respondents worked in teams, most implanting from 46 to 55 pacemakers annually. The chief indications for permanent pacing were sick sinus syndrome (48%) and impairment of conduction in the atrioventricular node and His-Purkinje system (42%). Ninety-five percent of pacing leads were implanted transvenously. Seventy percent of the respondents had had experience with atrial and dual-chamber pacemakers, used largely to increase cardiac output. The use of ventricular demand (VVI) pacing decreased accordingly from 91% in 1975 to 84% in 1981. Although approximately 90% of primary pacemakers were programmable to some degree, almost half were not reprogrammed within the first 3 months after implantation and 30% were never reprogrammed. Most patients (85%) were followed up by transtelephonic electrocardiographic monitoring, 68% in conjunction with private office visits. The respondents estimated that dual-chamber pacing, accounting for 10% of implants in 1981, would increase to 37% by 1985. Early electrode malfunctions were less frequent when implantation was performed by high volume and solo implanters, and in public and community hospitals. It is concluded that periodic surveys of this type disclose important trends in the practice of cardiac pacing.
In April, 1973, a decade-long study was begun on nuclear-powered pacemakers. The first 15 of these were designed by the Numec Corporation under a contract from the United States Atomic Energy Commission. Altogether 151 units powered by the isotope plutonium 238 were implanted in 131 patients; the pacemakers of 4 different manufacturers were used. The last nuclear pacemaker was implanted in January, 1983. The actuarial survival at 10 years was 92%, meeting the original performance goal of the Commission of 90%. Ninety pulse generators are still in service today; 25 patients have died and 36 pulse generators have been replaced with non-nuclear units. The most common indication for replacement was an inappropriate pacing mode. This high reliability and superior performance suggest that continued use of a radioisotopic power source is justified, particularly if combined with the electronic circuits of today's dual-chambered, multiprogrammable, and multifunctional pacemakers.
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From January 1979 through December 1982, 2026 patients scheduled to undergo open heart surgery were evaluated by a preoperative battery of noninvasive carotid tests including phonoangiography, oculopneumoplethysmography, pulse-timing oculoplethysmography, periorbital Doppler examination, and during the last 12 months, continuous-wave Doppler ultrasonography with spectral analysis. The incidence of hemispheric neurologic deficit following cardiac surgery in the 47 patients with carotid disease was 14.9%; the incidence in patients with no carotid disease was 1.9% (p less than 0.001). Fourteen of the 47 patients were not candidates for carotid surgery because of unilateral occlusion in 13 and bilateral occlusion in one. Three of the 14 (21.4%) had intraoperative strokes on the appropriate side. Thirty-three of the 47 had operable carotid disease. Four with unilateral stenosis had no carotid surgery; one had a postoperative deficit on the side referable to the nonstenotic artery. Eighteen with unilateral stenosis underwent simultaneous cardiac and carotid surgery; one (5.6%) had a transient deficit. Seven patients with bilateral stenosis underwent cardiac and unilateral carotid surgery; no deficits occurred. Four patients with unilateral stenosis and contralateral occlusion underwent combined surgery; one had a transient ischemic attack and one a fatal stroke, both referable to the hemisphere ipsilateral to the occlusion. It appears that the presence of carotid disease increased the risk of stroke during heart surgery. Proof that carotid endarterectomy lowers this risk awaits a prospective randomized trial.
Evidence of ischemia after acute myocardial infarction is a serious complication. If angiography reveals significant coronary artery disease, the precise timing of myocardial revascularization may be of critical importance. From 1978 through 1982, 174 patients underwent myocardial revascularization within 7 weeks of a documented myocardial infarction. The male:female ratio was 138:36, the average age was 58 +/- 1 (SEM) years; and the ejection fractions averaged 41% +/- 1%. Forty-four (25%) patients required preoperative intra-aortic balloon pump support, and an additional 18 (10%) required intra-aortic balloon pumping to be separated from cardiopulmonary bypass. An average of 2.9 +/- 0.1 vessels per patient were bypassed. The hospital mortality for these 174 patients was 16%. When mortalities were categorized according to the postinfarction week in which operation was performed, hospital mortality fell from 46% for those patients operated upon within 1 week of infarction to 6% for those patients operated upon 7 weeks after infarction. Of those patients operated upon within the first week after infarction, 23% were in cardiogenic shock and 62% required preoperative balloon pumping. Clearly the most critically ill patients were operated upon during the early postinfarction period. However, there was a marked difference in survival when patients in each of the seven weekly groups were classified according to ejection fraction. All patients with an ejection fraction greater than or equal to 50% (50 patients) operated upon at any time after infarction survived their hospital course, with only one late death. Conversely, among the 124 patients with an ejection fraction less than 50% operated upon during this 7 week interval, there were 27 (22%) hospital deaths. In this latter group, survival rates steadily improved if revascularization was performed at a time more remote from the infarction. The difference in early and late survival rates of patients operated upon with an ejection fraction greater than or equal to 50% compared to patients with an ejection fraction less than 50% is highly significant (p less than 0.001). We conclude that myocardial revascularization is safe at any time after myocardial infarction for those individuals with an ejection fraction greater than or equal to 50%. However, if the ejection fraction is less than 50%, then operation after myocardial infarction should be delayed at least 4 weeks.
Intraoperative angiography in carotid extracranial surgery demonstrates technical defects in 5% to 8% of patients. A simple and safe method of completion contact angiography (CCA) has been perfected by adapting dental x-ray equipment, small dental film cassettes, and a "shoe box" type of developing unit. The method is not technician dependent, requires only 5 ml of contrast medium, has a completion time of less than 5 minutes, and produces no measurable radiation to the operating team. CCA was performed with no complications in 40 patients undergoing carotid endarterectomy. Two unsuspected internal carotid artery defects (5%) were discovered: in one a stenosis was immediately repaired, and in the other small thrombi that were seen but not removed were probably the cause of a postoperative transient ischemic attack. Two complete occlusions and one prominent intimal flap in the external carotid artery were also identified. We believe that CCA after carotid surgery should be used routinely because it is safe and simple and reveals unsuspected operative defects that can be corrected immediately.
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One hundred consecutive patients requiring propranolol hydrochloride before undergoing isolated aortocoronary bypass procedures were examined. In half the patients, propranolol therapy was discontinued, whereas the other half continued to receive intraoperative and postoperative propranolol regardless of clinical events. Although there were no preoperative differences in the apparent degree of coronary arterial disease or left ventricular function in the two groups, postoperative supraventricular arrhythmias were less frequent in the propranolol-treated group, most noticeably in those receiving less than 320 mg preoperatively. In patients who had received large preoperative doses (greater than or equal to 320 mg/day), there were no significant differences in postoperative supraventricular tachycardias. Continued propranolol therapy following isolated coronary bypass surgery appears to be a safe and efficacious method of decreasing the incidence of postoperative supraventricular tachycardias.
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The pacemaker of the 1980s is designed to maintain atrioventricular synchrony through dual-chamber pacing. This pacemaker is multiprogrammable and capable of telemetric transmission of biologic, electronic and electrophysiologic data. Several developments have made this therapeutic modality possible: 1) the cumulative survival rate of many lithium-battery pacemakers exceeds 95% at 5 years; 2) lead and connector problems are rare; 3) atrial and ventricular electrode malfunctions occur in less than 2% of implants; and 4) new introducer techniques have simplified implantation (mortality and major morbidity rates are 0.5 and 0.4%, respectively). With multiprogrammability, pacemaker function can be optimized for the patient's needs, and about 20% of reoperations can be avoided. Ninety-six dual-chamber (DDD) pacemakers, 55 of which have been followed up for more than 3 months, have provided trouble-free performance and have yielded salutary clinical results, particularly when implanted to replace previous ventricular inhibited units. Problems with these pacemakers have included unusual pacing electrocardiograms, pacemaker eccentricities, programmer maintenance, pacing and follow-up complexities and costs. In the 1980s, effort will be required to find a balance between rapidly evolving technology and the clinical need for complex pacing systems. From 1978 to 1981, the rate of pacemaker implantation grew from 309 to 513 implants per million population per year, and there are now approximately 500,000 patients with implanted pacemakers living in the United States. Indications for pacing are ill-defined, because in many cases the assessment of clinical response to pacing is largely subjective, lacking satisfactory quantitative indexes. This decade will be a time of reappraisal of the extent of clinical applicability of new techniques, particularly the multiprogrammable dual-chamber system which, after 3 years of clinical trial, shows promise of being the predominant pacemaker of the immediate future.