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S J Schwartz

Publications and source records attributed to S J Schwartz.

12 recordsLinked to original sources
PubMed1992

Chromatographic analysis of cis/trans carotenoid isomers.

Cis/trans configurations of carotenoids are known to effect the biochemistry of carotenoids in certain situations. Methodology for separating carotenoid cis/trans isomers is of importance to nutritionists and food scientists because cis isomers of provitamin A carotenoids have lower provitamin A activities than the all-trans form. Traditional food processing and preservation methods, especially thermal treatments, induce the formation of cis isomeric forms. However, many challenges, are apparent for identifying and analyzing cis/trans isomers present in foods and other biological tissues. The development of current chromatographic methods for the separation of carotenoid cis/trans isomers is reviewed. For the separation of beta-carotene isomers, most procedures employ either Ca(OH)2 or Vydac C18 columns. In general, polymeric C18 columns allow for the detection of cis carotenes, while monomeric C18 columns provide for some separation of certain xanthophylls. The main cis isomers detected in foods are the 13-cis and 9-cis forms, although other forms have also been found (mainly 15-cis and various di-cis isomers). More studies involving the metabolism and physiological consequences of cis/trans isomers in the diet are needed. However, due to limitations in current techniques, further method development in the area of separation, detection and quantitation of cis/trans carotenoid isomers will be required.

Carotenoids↗
PubMed1992

Lead extraction. Indications and techniques.

Each of the extraction techniques and their ancillary tools was reported as used successfully; however, until now, no technique has been successful when used in more than a few isolated instances. The technique for intravascular countertraction and the associated tools described in this paper were devised and selected in an attempt to develop one technique to be used on all patients, with all types of leads, and with a very low complication rate. Its versatility permitted single or multiple lead extractions combined with the precision of selecting and extracting a specific lead. In our experience, as well as the experience of others, the techniques described in this paper have proved to be superior by minimizing the inherent risk and morbidity, allowing us to expand the indications for lead removal beyond septicemia and free-floating leads, to include infection, abandonment of pockets, and replacement of malfunctioning or fractured leads. Intravascular countertraction was a consistently safe and efficacious method of removing transvenous pacemaker leads regardless of the duration of the implant, thus permitting extractions in patients not considered candidates for a more extensive surgical procedure. Intravascular countertraction encompasses surgical and fluoroscopic techniques possessed by most physicians experienced in pacemaker and automatic implantable cardioverter defibrillator implants. However, there is a learning curve, predicating caution for the inexperienced physician. In addition, advanced surgical skills may be needed in handling associated conditions such as debridement and primary closure of chronically inflamed tissues, especially in submuscular pockets and sinus tracts in the neck. Although the potential for a cardiovascular complication is small, it does exist, and cardiovascular surgical backup is a recommended precaution.

Cardiopulmonary Bypass↗
PubMed1991

Intravascular techniques for extraction of permanent pacemaker leads.

Intravascular techniques were used to extract 226 leads from 124 patients. Indications for lead extraction were life-threatening septicemia (30%), complications of free-floating leads (2%), abandonment of pockets (40%), and replacement of malfunctioning leads (28%). Extraction tools included flexible, telescoping sheaths advanced over the lead to dilate scar tissue and apply countertraction, deflection catheters, and wire basket snares. Countertraction is defined as the direct force of traction on the lead countered by the circumference of an extraction sheath. One hundred sixty-four leads were extracted through the superior vena cava by advancing the sheaths over the lead to the myocardial wall. Most of these leads passed through the subclavian vein. An approach through the inferior vena cava was used for the remaining 62 leads. The countertraction sheaths were passed from the femoral vein into the right atrium. A maneuvering catheter and an extracting snare were placed inside the sheaths. The lead was positioned by the maneuvering catheter, entangled in the extracting snare, and the sheaths advanced over the snare and lead to the myocardium. An atriotomy by means of a limited surgical approach was required to free one lead. One infected lead broke 5 cm from the electrode and was removed through a median sternotomy, ventriculotomy, and retrograde extraction. All patients had unremarkable recoveries. Intravascular countertraction techniques proved to be a viable alternative, minimizing the risks and morbidity of lead removal.

Adolescent↗
PubMed1990

Transatrial implantation of transvenous pacing leads as an alternative to implantation of epicardial leads.

State-of-the-art pacing modalities are not readily utilized with conventional epicardial pacing lead implantation techniques. A transatrial implantation technique was developed combining a limited surgical approach with transvenous leads. Six patients who were poor candidates for transvenous implants have received DDD or DDDR pacemakers by this approach. The limited surgical approach includes resection of the third or fourth costal cartilage through a small skin incision, reflection of the pleura, and opening of the pericardium. The introducer and transvenous leads are inserted through a right atrial pursestring suture. The leads are positioned in the right ventricle and right atrium using standard fluoroscopic techniques. Through the incision, the subcutaneous tissue pocket is constructed on the right anterior chest wall. The leads are connected to the pacemaker without the need for adaptors or tunneling. There were no procedure-related complications. The magnitude of the surgery and postoperative morbidity are significantly less than for a standard thoracotomy, median sternotomy, and transdiaphragmatic epigastric or subcostal approach. The utility of the transatrial implantation technique is that it allows the use of state-of-the- art bipolar dual chamber pacemakers restoring access to all pacing modalities for those patients not candidates for transvenous implantation.

Adult↗
PubMed1990

Intravascular lead extraction using locking stylets and sheaths.

Chronic lead extraction using intravascular countertraction techniques was studied in patients with over 65 different lead models including passive and active fixation devices. Indications for removal of 115 leads implanted 5 days to 264 months (mean 58 months) in 62 patients (mean 65 years) included septicemia, subcutaneous tissue infection, preerosion, free-floating lead, lead trapped in valve, too many leads, pain, and vein thrombosis. The superior vena cava (SVC) approach was attempted in 101 leads and was successful in 82 attempts (71% of total leads). The inferior vena cava (IVC) approach via the femoral vein was required to extract 14 (12%) leads inaccessible to the SVC approach and the 19 leads that failed the SVC approach (29% of total leads). The SVC procedure includes a sized stylet locked at the tip and telescoping sheaths advanced over the lead to the heart. An IVC procedure includes placement of a 16 F sheath workstation via a femoral vein into the right atrium. A deflection catheter and Dotter snare in an 11 F sheath were advanced through the workstation into the right atrium. The lead was maneuvered into position, snared, and pulled into the workstation. For both the SVC and IVC approaches, the leads were removed by applying traction on the lead and countertraction with the sheaths. In experienced hands, these techniques have proven safe and effective for removing chronic transvenous leads.

Adult↗
PubMed1990

Determination of beta-carotene and its cis isomers in serum.

All-trans-beta-carotene was resolved from its cis isomers in human serum by reversed-phase "high-performance" liquid chromatography. Absorption spectra of the cis peak suggested that 13-cis-beta-carotene was the predominant cis isomer. Analyses and recovery studies of fresh and stored sera eliminated the possibility that isomerization had occurred in samples during handling or storage. The average analytical recovery was 101.9% for standards of the all-trans-, 9-cis-, and 13-cis-beta-carotene compounds in pooled serum samples. We also demonstrated that cis isomers had not formed after the blood was drawn and that cis isomers of beta-carotene are present at significant concentrations in the human circulation.

Carotenoids↗
PubMed1988

DDD pacemakers maximize hemodynamic benefits and minimize complications for most patients.

A 44-month retrospective analysis was performed on 666 pacemakers implanted at Mt. Sinai Medical Center. Mapping techniques and endocardial waveform analyses were used during lead positioning to ensure the best electrical environment. The optimal pacing lead type was selected based on the clinical situation. Follow-up evaluations were rigorous. Patient population ranged in age from 28 to 103 with a mean of 78 years at time of implant. Seventy percent of the patients received DDD pacemakers with an 81% survival incidence at 44 months. Of the VVI population (30% of the implants), there was a 62% survival incidence. Most problems associated with the pacing systems were related to the atrial channel. Loss of atrial sensing occurred in 7.5% of the population and was corrected noninvasively in 5.8%. Due to chronic loss of atrial sensing, 1.7% of the population remained programmed to DVI/VVI. A total of 7.7% were chronically reprogrammed from DDD to VVI, 5.6% secondary to atrial fibrillation. Reoperations were necessary in 1.2% of the malfunctioning systems that could not be corrected by reprogramming. The following conclusions were reached: (1) maximizing hemodynamic benefits and minimizing pacemaker complications permitted a survival rate equal to or better than that of the general population, and (2) chronic problems related to the atrial lead and malfunctions of the pacing system were minimized by careful patient selection, appropriate pacemaker and lead selection, endocardial waveform analysis, and thorough follow-up.

Adult↗
PubMed1986

Pacemaker clinic evaluations: key to early identification of surgical problems.

The pacemaker center evaluation was responsible for the timely reoperation of 341 pacemaker patients over the last three years. The most common indication for reoperation was battery end-of-service (46.3%). Battery testing and maintenance of accurate records for trend analysis ensures prompt generator replacement. Atrial and/or ventricular lead malfunction was the second largest indication (26.3%). Lead malfunction detected by bracketing capture and sensing thresholds included: dislodgement, penetration, exit block, fracture, insulation failure, and abnormal sensing. The third largest indication for reoperation was pacemaker pocket erosion and/or infection (15.5%). Examination of the pacemaker pocket site is an integral part of an evaluation. In conclusion, the three largest indications for reoperations can be best demonstrated in a pacemaker center where evaluations are personal and thorough, and accurate record keeping is maintained.

Adult↗
PubMed1985

Rapid analysis of starch, amylose and amylopectin by high-performance size-exclusion chromatography.

Starch components, amylose and amylopectin, were analyzed by high-performance size-exclusion chromatography. These two-components were separated using a two-column system (E-Linear and E-1000) and dimethyl sulphoxide as the mobile phase. The void volume (V0 = 2.22 ml) was measured using tobacco mosaic virus. Column calibration was accomplished with dextrans of known average molecular weight (Mw range = 10,100-2,000,000). The elution volume of amylopectin (Ve = 2.5 ml) indicated that this starch component was fractionated on the column system despite its very large molecular size. Standard curves were prepared from various mixtures of purified corn and wheat amylose and amylopectin. From the linear relationships obtained, the percentages of both components in corn and wheat starches were determined. The method developed proved useful to monitor the purity of amylose and amylopectin preparations, and to estimate rapidly the amylose:amylopectin ratio of starch samples.

Amylopectin↗