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Biomedical subjects

V Parsonnet

Publications and source records attributed to V Parsonnet.

At least 19 recordsLinked to original sources
PubMed1992

Survey of cardiac pacing in the United States in 1989.

A survey of physicians who implant permanent cardiac pacemakers was conducted to identify practice patterns related to pacemaker-implantation frequency, hospital and implantation-facility characteristics, indications for pacing and pulse-generator replacement, preferences regarding device types, pacing modes, follow-up methods and frequency, and type and frequency of pacing-related complications. Questionnaires were sent to 11,414 potential physician respondents and 6 pacemaker manufacturers. Implanters' opinions were solicited regarding such issues as the importance of various device features and capabilities, the appropriateness of practice guidelines, and the efficacy of quality-assurance measures. In 1989, 89,445 primary pacemaker implantations and 21,055 pulse-generator replacements were performed by approximately 7,919 physicians at about 3,400 U.S. centers. Typically, a pacemaker manufacturer's sales representative played an active role in 80% of cases. Since the last survey, which examined pacing practices in 1985, primary implantations of dual-chamber pacemakers increased from 22 to 32%, and the proportion of adaptive-rate pacemakers increased from 1 to 40% of primary implants. The "typical" implanter used bipolar electrode systems in 90% of cases, single-chamber pacemakers in 70%, and the introducer method in 95% of lead placements. Significant differences in practice patterns were found among subsets of the survey respondents. Surgeons tended to work alone, use simpler, single-chamber pacemakers, and leave follow-up to others. Electrode stability tended to be better among implanters in nonacademic environments. The quadrennial survey continues to provide useful information on an easily identifiable and traceable patient population, but the process would be greatly simplified by the adoption of a "universal" reporting system such as that used in Europe.

Adult↗
PubMed1992

Deleterious effects of long-term single-chamber ventricular pacing in patients with sick sinus syndrome: the hidden benefits of dual-chamber pacing.

Nine hundred fifty patients who received three modes of primary pacemaker systems (581 dual-chamber universal [DDD], 84 atrioventricular-sequential ventricular-inhibited [DVI] and 285 ventricular-inhibited [VVI]) over 12 years were studied retrospectively to determine the effect of pacing mode on patient longevity and the subsequent development of chronic atrial fibrillation or flutter. All patients were followed up continuously for 7 to 8 years. Patients were classified according to indication for permanent pacing (sick sinus syndrome or other indication), age at pacemaker implantation (less than or equal to 70 or greater than 70 years) and history of atrial tachyarrhythmia. Fourteen percent of patients developed atrial fibrillation at some time during the study period. Of those, 4% had a DDD pacemaker, 8% had a DVI pacemaker and 19% had a VVI pacemaker. At 7 years, atrial fibrillation was significantly more frequent in the VVI group than in the DDD and DVI groups. In patients with sick sinus syndrome, the incidence rate was even higher in the VVI group but approximately the same in the DDD and DVI groups. Patients in the VVI and DVI groups who had had previous atrial tachyarrhythmia had a significantly higher incidence of atrial fibrillation at 7 years than did those in the DDD group. During the entire period there were 130 deaths in the study group, including 22% of patients with a DDD pacemaker, 38% of those with a DVI pacemaker and 50% of those with a VVI pacemaker. Patient survival at 7 years was lower in the VVI group than in the DDD or DVI groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Strategies for mode selection in antibradyarrhythmia pacing.

A systematic technique is described for selecting an appropriate mode of antibradycardia pacing on the basis of 10 clinical criteria. A computer model of the selection process was developed with input from more than 41 implanting physicians, and implemented together with a database management system for keeping track of mode selections and identifying cases in which the modes selected by the implanters differed from those recommended by the model. The selection technique, which can be used without a computer, is presented in detail with a decision-tree representation of the model and an explanation of the rationale behind each of its 39 possible recommendations.

Algorithms↗
PubMed1991

Extraction of implanted transvenous pacing leads: a review of a persistent clinical problem.

Within a few months of implantation, permanent pacemaker leads become ensheathed in fibrocollagenous tissue. This tissue may anchor the lead so that it is difficult, dangerous, or impossible to remove it. Leads with bulbous or finned tips are particularly resistant to extraction. The risks of applying traction to an entrapped lead include induction of bradycardia or ventricular tachycardia and fibrillation, invagination of the right ventricle, avulsion of the right ventricular myocardium or tricuspid valve, hemopericardium, and cardiac tamponade. Forceful traction may result in uncoiling of the conductor, disruption of the insulation, or complete fracture, leaving an intravascular remnant that may embolize or be a source for thrombosis. Although fixation and abandonment of an inactive chronically implanted lead is frequently appropriate and is known to pose little long-term risk, the retained inactive lead may interact adversely with a new active lead and then increase the risk of venous thrombosis, serve as a potential nidus for infection, or produce spurious electrical sensing signals that may be sensed by the pulse generator. Absolute indications for lead removal are those in which there would be a life-threatening situation if the lead were to remain in situ. In the absence of an absolute indication, the decision to proceed with extraction must be made by weighing the potential for serious morbidity or mortality against risks of the extraction technique. Techniques for lead removal include traction and open cardiotomy operations. When a portion of the lead is intravascular, forceps, snares, baskets, countertraction, or lead-transection devices may be used to retrieve the fragment.

Electrodes, Implanted↗
PubMed1991

Ultrasound-guided balloon angioplasty is a new technique for vascular surgeons.

A new catheter has been developed that can be accurately and precisely positioned using duplex ultrasonography alone. A piezoelectric transducer that functions as a passive, omnidirectional receiver is attached to the mid-balloon region of an angioplasty catheter. Integration to a standard duplex imaging system allows visualization of this receiver in all planes, with the location of the receiver represented by a flashing bright arrow superimposed on the ultrasound B-mode image. This catheter was tested successfully in 10 dogs with bilateral femoral arteriovenous fistulas. With the use of duplex guidance, eight arterial and three venous stenoses were dilated and two stents were placed. Catheter placements and therapeutic outcomes predicted by ultrasound correlated with arteriographic findings. Ultrasound guidance has several advantages. It eliminates the risks associated with radiographic imaging. It also reduces patient costs and discomfort. Furthermore, procedures can be monitored continuously in real time with the collection of anatomic and physiologic data.

Angiography↗
PubMed1991

Defining the role of subtotal colectomy in the treatment of carcinoma of the colon.

Seventy-two patients with colon cancer were treated by primary subtotal colectomy, including 23 patients with acute and subacute left colon obstruction. There were two operative deaths and no cases of disabling diarrhea. One death occurred in the group with colon obstruction. Other indications for subtotal colectomy included multiple polyps associated with the primary tumor (32), synchronous carcinomas (15), a previous transverse colostomy for obstruction (8), associated severe sigmoid diverticular disease (2), age less than 50 years with a positive family history (3), adherence of the sigmoid loop to a cecal tumor (2), and metachronous carcinoma (2). There were multiple indications in several patients. Subtotal colectomy has a defined role in a wide variety of clinical settings associated with colon cancer, including management of obstruction of the left and sigmoid colon, particularly if the proximal colon cannot be evaluated before operation by colonoscopy or barium enema. Segmental or regional colonic resections are appropriate if the entire colon can be evaluated before operation and no associated neoplasms are revealed.

Adult↗
PubMed1991

Comparison of titanium-mesh and porous disc electrodes for epicardial defibrillation.

The object of this study was to compare the effectiveness of chronically implanted porous electrodes with that of smooth mesh titanium electrodes of the same diameter but smaller effective surface area. The criteria used in evaluating the electrodes were (1) acute, subacute, and chronic resistance and (2) acute, subacute, and chronic defibrillation thresholds. Electrode pairs 2.5 cm in diameter were implanted in each of 17 dogs (ten mesh and seven porous). One electrode of each pair was sutured to the right ventricle and one to the left ventricle near the cardiac apex. Defibrillation threshold energy and total resistance were measured at the time of implantation and again 6 and 12 weeks after implantation. The mean initial resistance of the titanium electrodes was 131.7 omega; the mean defibrillation values for the porous electrode implant were 96.9 omega and 7.5 joules, respectively. Three to 6 weeks after implantation, the values for the titanium mesh electrode were 88.9 omega and 12.0 joules, while those for the porous electrode were 59.9 omega and 8.0 joules. In the chronic state, the figures for the titanium mesh electrode were 78.1 omega and 13.0 joules, while those for the porous electrode were 64.3 omega and 8.3 joules. We conclude that defibrillation can be achieved successfully with small epicardial electrodes. The findings suggest that a porous electrode, with its larger effective surface area, has lower electrode/tissue interface resistance in the acute and chronic phases, and, therefore, provides lower defibrillation threshold energy.

Animals↗
PubMed1991

Long-term functional integrity of atrial leads.

The effectiveness and reliability of atrial leads has been questioned. We studied retrospectively, all atrial leads implanted at our center (n = 494; 438 Medtronic Model 6957J, 56 Medtronic Model 4512) over a 5-year period ending December 31, 1987, to determine the frequency of atrial lead failure (pacing, sensing, or both) and the median duration of proper pacing and sensing function for each lead model studied. Eighty-eight percent of the polyurethane atrial leads continued to function satisfactorily at 5 years, results somewhat better than those reported heretofore in the literature, as well as our own past results with a variety of different lead types. There were 29 failures of pacing, sensing, or both (6% of implants). The cumulative survival of the atrial leads at 5 years was 88%. Pacing and sensing survival were 91% +/- 2.4% and 88% +/- 2.9%, respectively. We conclude that the choice of pacing mode for a new pacemaker should be based solely on the clinical indication and not on the concern that atrial pacing and sensing will be unreliable.

Electrodes, Implanted↗
PubMed1991

Transvenous placement of a pacemaker lead through an introducer despite long-standing subclavian-vein occlusion.

Under ordinary circumstances complete chronic subclavian vein occlusion precludes using that vein for the pacemaker lead. There are circumstances, however, in which a patent vein beyond the obstruction can be reached with an introducer needle, thus permitting transvenous access similar to any other introducer-assisted implantation. A case exemplifying this point is described. Patency of the right subclavian vein beyond an occlusion was demonstrated by angiography, and a new dual-chamber pacemaker lead was inserted through that site by use of the introducer method.

Catheterization, Central Venous↗
PubMed1991

Meralgia paresthetica after coronary bypass surgery.

Meralgia paresthetica is a neurologic disorder characterized by localized paresthesia and numbness on the anterolateral aspect of the thigh and involving the lateral femoral cutaneous nerve. It involves no motor deficits. Meralgia paresthetica, which may result from a variety of causes, has been observed as a rare complication in heart operations. Its cause when associated with such operations is uncertain but may be prolonged relaxed positioning on the operating table and recovery room stretcher. Another possible cause of meralgia paresthetica after heart operations is the "frog-leg" position of the legs during vein harvesting. Patients with this condition should be advised of its untreatable, but benign and self-limiting, nature.

Aged↗
PubMed1990

The nuclear pacemaker: is renewed interest warranted?

From 1973 through 1987, 155 radioisotope-powered "nuclear" pacemakers were implanted in 132 patients at the Newark Beth Israel Medical Center. The longevity of the first 15 devices, all of which were fixed-rate (VOO) pacemakers, was significantly better than that of 15 lithium-chemistry demand (VVI) pacemakers used as control devices (p = 0.0002). Of the entire cohort of 155 nuclear pacemakers, 136 were VVI devices and 19 were VOO units. The patients with VOO pacemakers needed reoperations more often than did those with VVI pacemakers, chiefly for mode change (p less than 0.001). Power-source failure was observed in only 1 case, but 47 nuclear pacemakers were removed for other reasons, including component malfunction (15 units), mode change (12 units), high pacing thresholds (8 units) and lead or connector problems (5 units). The actuarial survival at 15 years was 99% for power sources and 82% for the entire pacing systems (pulse generators plus leads). The frequency of malignancy was similar to that of the population at large and primary tumor sites were randomly distributed. Deaths most commonly were due to cardiac causes (68%). Thus, nuclear pacemakers are safe and reliable and their greater initial cost appears to be offset by their longevity and the resulting decrease in the frequency of reoperations. It is reasonable to suggest that further use be made of long-lasting nuclear power sources for modern pacemakers and other implantable rhythm-management devices.

Adolescent↗