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Biomedical subjects

V Parsonnet

Publications and source records attributed to V Parsonnet.

At least 91 records · Page 5Linked to original sources
PubMed1983

Continued propranolol administration following coronary bypass surgery. Antiarrhythmic effects.

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.

Arrhythmias, Cardiac↗
PubMed1983

Pacemaker inhibition.

Explore the source record for details and available documents.

Cardiac Surgical Procedures↗
PubMed1983

Cardiac pacing in the 1980s: treatment and techniques in transition.

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.

Arrhythmias, Cardiac↗
PubMed1983

Pseudomalfunctions of dual-chamber pacemakers.

The proliferation of dual-chamber pacemakers has created a host of electrocardiographic problems relating to interpretation. The term "pseudomalfunction" identifies an electrocardiographic finding that looks like pacemaker malfunction but is not. Several different models of dual-chamber pacemakers, which are either presently available or in clinical evaluation, produce different types of pseudomalfunctions. These are classified and described. Intimate knowledge of individual pacemaker characteristics is required for proper evaluation of these units.

Action Potentials↗
PubMed1983

Implications of constant-energy pacing.

Some cardiac pacemakers maintain constant energy per stimulus by automatically increasing the stimulus duration as battery depletion causes the stimulus amplitude to decline. This feature does not guarantee an invariant capture safety margin, however, because the stimulus energy at threshold increases for stimulus durations exceeding the geometric mean of the voltage and current chronaxie times. A method is described for identifying the impulse duration at which the initial capture safety margin begins to be lost with constant-energy pacing.

Cardiac Pacing, Artificial↗
PubMed1983

R-wave triggering of external instrumentation during cardiac pacing.

Monitoring and diagnostic instruments often utilize electrocardiographic R-wave detection for measuring heart rate or for timing of measurement processes. During cardiac pacing stimulus artifacts commonly interfere with the operation of such instruments because they are misinterpreted as R-waves. This phenomenon creates problems in assessing the hemodynamics during gated blood-pool scans, coronary care monitoring, and intra-aortic balloon pumping. A straightforward solution is found in the nature of the electrical signals involved in which the stimulus artifacts are detected independently and are removed from the signal fed to the R-wave detector.

Cardiac Pacing, Artificial↗
PubMed1983

Notation system and overlay diagrams for the analysis of paced electrocardiograms.

With the advent of adaptive dual-chamber pacing, the interaction between the pacemaker and the heart is becoming increasingly complex and the interpretation of paced electrocardiograms more difficult. We have developed a set of notation conventions for use in teaching and rhythm-strip analysis. Easily-drawn symbols delineate successful, unsuccessful, and inhibited pacing and sensing events as well as refractory and blanking periods. Another application is to generate movable transparent overlays after programming a pacemaker, to be used in interpreting subsequent rhythm strips.

Cardiac Pacing, Artificial↗
PubMed1983

Coronary artery bypass grafting in patients with ejection fractions below forty percent. Early and late results in 466 patients.

The outcome of patients undergoing coronary artery bypass grafting with preoperative ejection fractions below 40% was evaluated to determine if a specific level of ventricular dysfunction resulted in unacceptably poor short-term or long-term survival rates. Left ventricular ejection fractions were segregated into groups of five percentage points each starting from 35% to 39% and progressing down to 10% to 14%. In evaluating the six ejection fraction groups between 10% and 39%, we found no significant differences among them with regard to previous myocardial infarctions, left ventricular end-diastolic pressure (LVEDP), age, preoperative New York Heart Association (NYHA) class, or number of vessels bypassed. Eighty-four percent were men and 16% women. From 1976 through 1982, 466 patients were distributed among these groups, all having ejection fractions below 40% (mean 30% +/- 3% SEM). There were significant differences (p = 0.001) in both the hospital and long-term survival (36 months) of patients with preoperative ejection fractions from 20% to 39% (425 patients) as compared to those with preoperative ejection fractions from 10% to 19% (41 patients). Hospital survival rate was 89% for patients with ejection fractions from 20% to 39% but only 63% for patients with ejection fractions below 20%. Similarly, at 3 years, patients with ejection fractions of 20% to 39% had an average survival rate of 60% as compared to an average survival rate of 15% for those with ejection fractions below 20%. Neither the preoperative LVEDP nor the intraoperative ischemic arrest time significantly predicted survival. In all survivors, NYHA class decreased from an average of 3.00 to 1.25 in surviving patients following bypass at a mean follow-up of 29 +/- 5 months. It is concluded that ejection fraction is an excellent predictor of short-term and long-term survival following coronary artery bypass grafting. Patients with ejection fractions of 10% to 19% have a significantly reduced short-term and long-term survival rate as compared to patients with ejection fractions of 20% or more.

Angina Pectoris↗
PubMed1983

Optimal resources for implantable cardiac pacemakers. Pacemaker Study Group.

In this document, the 1974 Inter-Society Commission for Heart Disease Resources (ICHD) report, Implantable Cardiac Pacemakers, has been revised and updated to emphasize the increased complexity of present-day pacing, to propose realistic guidelines for various aspects of pacing practivce, and to identify the resources needed for delivery of this important mode of health care. The first section of the report describes the several types of pacemakers currently available, how they function, and how and to what purpose they may be modified through noninvasive programming. Recommendations are given for a modified and updated version of the widely accepted ICHD code for identification of pacing modes. The emphasis of the second section of the report is on physical and personnel resources. Matters considered in some depth include the training and qualification of the various medical, technical, and paramedical specialists involved in an implantation procedure; requirements for, and methods of achieving, short and long-term surveillance of pacemaker patients; and the role of the hospital, the manufacturers, and the FDA in this new era of complex dual-chamber, multiprogrammable pacemakers.

American Heart Association↗
PubMed1983

An argument for increased use of subtotal colectomy in the management of carcinoma of the colon.

Subtotal colectomy (STC) is a safe operation because operative mortality rates are as good as, if not better than, conventional segmental colon resections. It is no more difficult to perform than conventional segmental resections. Suture line complications, such as fecal fistulas and suture line recurrences, are not as common before as they are after colocolic anastomoses. In addition to being used in cases with known synchronous carcinomas, and carcinoma associated with polyps, STC should be considered in selected patients with obstructing or partially obstructing lesions of the sigmoid or left colon when complete evaluation of the proximal colon has not been possible. STC can be combined with a preliminary transverse colostomy for obstructing left colon lesions when appropriate evaluation demonstrates suitable indications for the resection of the colostomy as a one-stage procedure with ileocolic anastomosis. It also should be considered if there is significant distal sigmoidal diverticular disease associated with proximal carcinomas. Statistically, STC does not appear to be indicated as a prophylactic operation to avoid the development of metachronous colon cancer when the entire colon can be surveyed colonoscopically to assure that there is no associated neoplasm.

Adult↗
PubMed1983

Optimal resources for implantable cardiac pacemakers.

In this document, the 1974 Inter-Society Commission for Heart Disease Resources (ICHD) report, Implantable Cardiac Pacemakers, has been revised and updated to emphasize the increased complexity of present-day pacing, to propose realistic guidelines for various aspects of pacing practice, and to identify the resources needed for delivery of this important mode of health care. The first section of the report describes the several types of pacemakers currently available, how they function, and how and to what purpose they may be modified through noninvasive programming. Recommendations are given for a modified and updated version of the widely accepted ICHD code for identification of pacing modes. The emphasis of the second section of the report is on physical and personnel resources. Matters considered in some depth include the training and qualification of the various medical, technical, and paramedical specialists involved in an implantation procedure; requirements for, and methods of achieving, short- and long-term surveillance of pacemaker patients; and the role of the hospital, the manufacturers, and the FDA in this new era of complex dual-chamber, multiprogrammable pacemakers.

Arrhythmias, Cardiac↗