Other biodegradable synthetic polymers discount furosemide 40mg otc arteria tapada sintomas, including poly(anhydrides) and poly(ortho esters) discount furosemide amex hypertension workup, can also be used to fabricate scaffolds for tissue engineering with controlled properties  order 40mg furosemide with visa hypertension goals jnc 8. These cells are isolated by aspirating the inner cell mass from the embryo during the blastocyst stage (5 days after fertilization). Skin and neurons have been demonstrated, indicating ectodermal differentiation [10–13]. Blood, cardiac cells, cartilage, endothelial cells, and muscle have also been shown, indicating mesodermal differentiation [14–16]. These autologous stem cells have the potential to become almost any type of cell in the adult body and thus would be useful in tissue and organ replacement applications . There are, however, a number of limitations that require further study before this technique can be applied widely in tissue or organ replacement therapy. First, the efficiency of the cloning process is very low as evidenced by the fact that the majority of embryos derived from the cloning process do not survive [19–21]. In addition, cell cycle synchronization between donor cells and recipient oocytes must be accomplished . Transformation of adult cells into pluripotent stem cells through a type of genetic “reprogramming” has also been described. Reprogramming is a technique that involves dedifferentiation of adult somatic cells to produce patient-specific pluripotent stem cells, without the use of embryos. Cells generated by reprogramming would be genetically identical to the somatic cells (and thus the patient who donated these cells) and would not be rejected. They observed that the number of reprogrammed colonies increased when drug selection was initiated later (day 20 rather than day 3 posttransduction). This suggests that reprogramming is a slow and gradual process and may explain 396 why previous attempts resulted in incomplete reprogramming. An alternative approach would be to use a transient expression method, such as adenovirus-mediated system, since both Okita et al. This indicates that these viral genes are only required for the induction, not the maintenance, of pluripotency. Amniotic Fluid Stem Cells An alternate source of stem cells is from amniotic fluid. Amniotic fluid is known to contain multiple partially differentiated cell types derived from the developing fetus. The undifferentiated stem cells expand extensively without a feeder layer, and the population doubles every 36 hours. Lines were maintained for over 250 population doublings retaining long telomeres and a normal karyotype. Clonal human lines verified by retroviral marking can be induced to differentiate into cell types representing each embryonic germ layer, including cells of adipogenic, osteogenic, myogenic, endothelial, neuronal, and hepatic lineages. In this respect, they meet a commonly accepted criterion for pluripotent stem cells, without implying that they can generate every adult tissue. The cells could be obtained either from amniocentesis or chorionic villous sampling in the developing fetus or from the placenta at the time of birth. The cells could be preserved for self-use, could be used without rejection, or could be banked. Adult Stem Cells and Native Progenitor Cells One of the limitations of applying cell-based regenerative medicine techniques to organ replacement has been the inherent difficulty of growing specific cell types in large quantities. Even when some organs such as the liver have a high regenerative capacity in vivo, cell growth and expansion in vitro may be difficult. By studying the privileged sites for committed precursor cells in specific organs as well as exploring the conditions that promote differentiation, one may be able to overcome the factors that limit cell expansion in vitro. For example, though urothelial cells could be grown in the laboratory setting, these types of cultures had only limited expansion capability. Several protocols have been developed over the past two decades that have overcome this difficulty. Studies have identified the undifferentiated cells in a urothelial culture, and culture techniques to keep them undifferentiated during their growth phase have been developed [30–32]. Using these cell culture methods, it is now possible to expand a 2 urothelial strain from a single specimen that initially covers a surface area of 1 cm to one covering a 2 surface area of 3202 m (the equivalent of one football field) within 8 weeks . These studies have indicated that it should be possible to collect autologous bladder cells from human patients, expand them in culture, and return them to the donor in sufficient quantities for reconstructive purposes. In fact, expanded urothelial cells have been used in several clinical studies, including an important study that showed that a tissue-engineered bladder could be implanted into select patients . Major advances have been achieved within the past decade on the possible expansion of a variety of primary human cells, with specific techniques that make the use of autologous cells possible for clinical application. The success of cell transplantation strategies for bladder reconstruction depends on the ability to use donor tissue efficiently and to provide the right conditions for long-term survival, differentiation, and growth. Native cells are currently preferable due to their autologous source, wherein they can be used without rejection . It has been shown experimentally that the bladder neck and trigone area has a higher propensity of urothelial progenitor cells , and these cells are localized in the basal region . Amniotic fluid– and bone marrow–derived stem cells can also be used in an autologous manner and have the potential to differentiate into bladder muscle  and urothelium . Human urothelial and muscle cells can be expanded in vitro, seeded onto polymer scaffolds, and allowed to attach and form sheets of cells. Histological analysis indicated that viable cells were able to self-assemble back into their respective tissue types and would retain their native phenotype . It has been well established for decades that portions of the bladder are able to regenerate generously over free grafts, most likely because the urothelium is associated with a high reparative capacity . Both urothelial and muscle ingrowth are believed to be initiated at the edges of the injury, from the normal bladder tissue in toward the region of the free graft. Inflammation in response to the matrix may contribute to the resorption of the free graft (Figures 27. As a result of this discovery, it was hypothesized that building the 3D bladder constructs in vitro, before implantation, would facilitate the eventual terminal differentiation of the cells after in vivo implantation. Further, this could minimize the inflammatory response, thus avoiding graft contracture and shrinkage. In a dog model , matrices that were seeded with cells and then used for bladder augmentation retained most of their preimplantation diameter, as opposed to matrices implanted without cells, in which significant graft contraction and shrinkage occurred. In addition, histological analysis demonstrated a marked paucity of muscle cells and a more aggressive inflammatory reaction in the matrices implanted without cells. The results of these initial studies showed that the creation of artificial bladders may be achieved in vivo; however, it could not be determined whether the functional parameters noted were created by the augmented segment or by the remaining native bladder tissue. This confirms that the type of scaffold used in the construction of tissue-engineered bladders is critical for the success of these technologies. The use of bioreactors, which provide mechanical stimulation for the growing organ in vitro, has also been proposed as an important parameter for success .
In such a situation best buy for furosemide arteria tibialis posterior, it is advisable to consider use of a E-lactamase inhibitor along with aE-lactam purchase cheap furosemide online arrhythmia medication, say amoxicillin- clavulanate (co-amoxiclav) or ampicillin-sulbactam for a gratifying outcome generic furosemide 40 mg on-line blood pressure medication in liquid form. Saphylococcal Pneumonia A penicillinase-resistant penicillin (cloxacillin) plus ampi- cillin is the best choice. A specifc antibiotic agent is dictated by the anticipated Aspiration pneumonia: Use of prophylactic antibiotics causative agent rather than the anatomic type of pneumonia. Needless to say, these recom- Pneumococcal Pneumonia mendations are subject to changes which may be war- Penicillin is the drug of choice for pneumococcal ranted following receipt of culture and sensitivity report. In uncomplicated cases, it leads to dramatic Gram-negative bacilli: Generally, aminoglycosides response, causing complete resolution in 7–14 days. Staphylococcus aureus: Vancomycin or cloxacillin; Obstruction due to collection of thick mucus as in quinolones and cefazolin are good alternatives. Te so-called Bed rest Kartagener syndrome is characterized by dextrocardia Suction to remove secretions from tracheobronchial (usually with situs inversus), chronic bronchitis with tree bronchiectasis at a later stage and sinusitis. Chronic bronchitis Symptomatic treatment for cough, restlessness, fever is what is usually encountered in childhood. Te origin of the syndrome is Physiotherapy—breathing exercises during recovery ascribed to generalized defect of ciliary motility right from are of value. Te most common organism found in the sputum of children with Treatment of congestive cardiac failure, if present. Te onset is usually insidious with persistent or recurrent Finally, a word of caution. Such an administration may prove Some fever and recurrent attacks of respiratory infections counterproductive by causing respiratory alkalosis. Prognosis is generally good following appropriate and in Te characteristic auscultatory fnding is the localized time treatment. Consequent to this, there is cavitation of the Radiology—X-ray chest shows increased bronchovas- bronchial wall and tissue destruction. Bronchography (it should be preceded by bronchos- Etiopathogenesis copy) is essential to localize and establish the extent of As already mentioned, bronchial occlusion and infam- bronchiectasis. If the occlusion is Treatment signifcant, there results collapse distal to and dilation proximal to the site of obstruction. Partial obstruction frst Appropriate antibiotic cover: Systemic antibiotics causes emphysema in the distal part. Surgical intervention to remove the afected lobe(s), In a large majority of the children, it is unilateral, generally provided that medical treatment, given over a 12-months involving the posterior basal segment of the left lower lobe. Clinical Features Physical examination shows some dullness on percus- sion and diminution of breath sounds in case of thickened Onset is usually subacute with manifestations, such pleura or a thick layer of exudates. A rough to and fro fric- as high fever, cough, chest pain on afected side (that tion sound, pleural rub may be heard early in the disease. Breathlessness may occur depending on rapidity of Diagnosis accumulation and magnitude of efusion. Chest X-ray shows a difuse haziness at the pleural surface Physical examination reveals decreased chest move- or a dense well-defned shadow. Diferential diagnosis ments on afected side, mediastinal shift to the oppo- includes pleurodynia, rib fracture, herpes zoster, etc. Percussion note in axilla may be at a It is the collection of serous fuid (in empyema, it is the higher level. Pleural efusion is relatively less frequent in children; X-ray chest shows a uniform opacity with a curved fuid almost all cases are seen beyond 5 years of age. Pleural line which may become horizontal when air is also fuid may be transudate (clear with protein <3 g% and no coexisting (Fig. Tere is a defnite mediastinal shift cells) or exudate (straw-colored with protein >3 g% and to the opposite side. Pleural tap See Chapter 49 (Pediatric Practical Etiology Procedures) and examination of the fuid confrms the Tuberculosis is responsible for majority of the cases fol- diagnosis. In a small Treatment proportion, thoracic lymphoreticular malignancy may be the cause. Specifc chemotherapy depends on the etiology of pleural Pleural efusion results from discharge of the case- efusion, most cases needing antituberculous therapy. Hematogenous, or local is indicated in case of large pleural efusion causing spread as also allergic reaction to tuberculous proteins too respiratory distress. It is worth remembering that empyema must be ruled out in any infant with localized dullness of the percussion note. Complications Bronchopleural fstulas Pyopneumothorax Purulent pericarditis Pulmonary abscesses Fig. X-ray chest: In addition to the mediastinal shift to the Etiology opposite side, it shows a difuse density suggestive of pleural fuid. In most of the cases, the opacities are basal Te most common organism responsible for empyema is and costophrenic angle is obliterated. Infrequently, Streptococcus pneumoniae, ema may, however, occur in the fssures or at the apex. Hemophilus infuenzae, and even Mycoplasma pneumonia Diagnostic pleural tap: Te fuid is purulent (turbid) account for a small proportion of the cases. Usually it is the outcome of a complication of: and should be examined biochemically (for high Pneumonia (usually staphylococcal) protein and low sugar) as also bacteriologically (for Lung abscess causative pathogens). Bronchiectasis Treatment Subdiaphragmatic abscess/liver abscess (rupture) Septicemia Antibiotics should be started as soon as the diagnosis Metastatic spread of suppurative foci from distant lesions is arrived at. Clinical Features Pneumococcal empyema shows a gratifying response Clinical manifestations, if present, are those of to penicillin G. Antibiotic therapy should, therefore, be continued for 3–4 In case of marked respiratory distress, the child is weeks. It needs to be controlled by underwater Long-standing cases develop clubbing, anemia and seal or continuous suction. Tey Surgical drainage after rib resection (thoracotomy may, however, sufer from growth failure and vague or thoracotomy) may be resorted to in case of severe symptoms. Empyema in such cases is usually detected respiratory difculty, when improvement fails to occur when the child is subjected to a detailed clinical check- after 3 weeks, in loculated pus, or in the presence of up. Before antibiotic era, the Te peak incidence is, however, seen in 5–10 years of age prognosis used to be very bad. Allergy to certain foreign substances: z Inhalants like pollen, smoke, dust* and powder; Etiology z Foods like egg, meat, wheat and chocolate; Single abscess:Usually due to pneumonia, tuberculosis z Food additives; or foreign body and, occasionally, following rupture of z Drugs like aspirin and morphine. In majority of amebic liver abscess into lung or superadded infection the asthmatics, it is, however, difficult to find the of hydatid cyst. Multiple abscesses: Usually due to pneumonia, Respiratory infection: Usually a viral infection causes tuberculosis, cystic fbrosis, fungal infection, leukemias, mucosal edema and mucous secretion that result in agammaglobulinemia, etc. If an abscess fails to resolve, it may cause pleurisy, Emotional disturbances: A row with the siblings pleural efusion or empyema.
The features of each module are summarized in the following texts to inform decisions regarding questionnaire selection generic 40 mg furosemide hypertension kidney group 08755. This can be a more sensitive indicator of treatment outcome than frequency of symptoms alone (Figure 17 buy furosemide 100mg without prescription hypertension images. The bladder diary provides the first validated diary for the collection of bladder-related events buy furosemide with mastercard blood pressure z score. Qualitative studies were conducted to derive the parameters for inclusion followed by quantitative studies to evaluate the robustness of the tool. These instruments contain only question items associated with the symptom complex or have been developed specifically for use in a specific group. Recommended Add-On Modules Core Modules This group of questionnaires incorporates quality of life and sexual matters modules. They are recommended to be completed as stand-alone questionnaires or alongside core or specific symptom evaluations. The core symptom modules described earlier contain bother items indicating impact on quality of life directly related to symptoms. Quality of life questionnaires cover more specific issues that are a consequence of symptoms (e. The combination of symptom assessment with associated bother and a quality of life assessment provides a more complete evaluation of the patient’s experience [15,22]. Specific Patient Groups In the same manner as the symptom modules, quality of life modules are available for specific symptom complexes. Requires evaluation of sensitivity to change Domains/items Catheter function and concern Lifestyle impact Number of items 17 Available Nil translations Scoring system 0–42 catheter function and concern subscale 3–15 lifestyle impact subscale Derived from Newly developed module (submitted for publication) Table 17. Posttreatment Module The issue of posttreatment satisfaction evaluation is being explored from various perspectives. To date, a fully validated questionnaire for generic use among individuals undergoing varied treatments for all lower pelvic dysfunction has not been fully validated. An alternative suggestion is that satisfaction may be simply assumed by alleviation of symptoms or improvement in quality of life. Ongoing studies will provide further evidence on which to make suggestions regarding posttreatment evaluation. Domains/items Life restrictions Emotional aspects Preventive measures Number of items 22 Available 45 translations Scoring system 0–76 total score of all items 0–10 overall impact on everyday life subscale Bother scales are not incorporated in the overall score but indicate impact of individual quality of life aspects for the patient Derived from King’s Health Questionnaire  2. Quantitative studies were also undertaken to evaluate the comparability of findings between the different formats to ensure at least equivalence of the measurement properties, which is considered standard methodology for the conversion of paper questionnaires for electronic completion . More than 1200 requests for use of the various modules have been recorded and over 200 related publications have been identified. This is particularly important in clinical practice and research where treatment decisions or trial outcomes increasingly rely on this source of evidence. Health Measurement Scales: A Practical Guide to Their Development and Use, 3rd ed. A patient centered approach to developing a comprehensive symptom and quality of life assessment of anal incontinence. Guidance for industry: Patient-reported outcome measures: Use in medical product development to support labeling claims. The standardization of terminology for researchers in female pelvic floor disorders. A scored form of the Bristol female lower urinary tract 244 symptoms questionnaire: Data from a randomized controlled trial of surgery for women with stress incontinence. Developing and validating the International Consultation on Incontinence Questionnaire bladder diary. Assessment of treatment outcomes in patients with overactive bladder: Importance of objective and subjective measures. The Bristol female lower urinary tract symptoms questionnaire: Development and psychometric testing. Coons S, Gwaltney C, Hays R, Lundy J, Sloan J, Revicki D, Lenderking W, Cella D, Basch E. More recently, however, their use has now become a desirable, if not essential element in routine clinical practice . This chapter explores the concept, development, and introduction of electronic assessment in urogynecology, aiming to bridge the divide between research use and day-to-day patient care. Whereas electronic systems now provide integral elements in industries such as retail, finance, travel and communication; healthcare generally lags behind. Paper-based recording systems are however increasingly recognized as being outdated, and change in this sector is gathering pace. Electronic data collection compares favorably with paper-based systems in terms of reliability and validity, with lower levels of missing data. Patients have found them relatively easy and even enjoyable to complete, offering efficiency advantages for large surveys [3,4]. When collecting sensitive data, computer-assisted interviewing results in greater openness and disclosure than paper-based questionnaires or face-to-face interviews [5–7]. These findings have implications for questionnaire use in urogynecology, both in research and clinical practice. The sample sizes in these studies were relatively small (n = 52), and although correlations were strong, differences were observed between different formats and not all patients were willing or able to use the electronic questionnaire. In the select sample of those who did use both formats, the majority expressed a preference for web-based completion. Using questionnaires in direct clinical care presents substantially different challenges . In order for a questionnaire to be clinically useful, it must be accessible, meaningful, and easy-to-use (both for patients and clinicians) as well as possessing demonstrable reliability, validity, and responsiveness. In order to inform clinical assessment, a questionnaire should ideally be completed prior to clinical consultation, although most condition-specific questionnaires are too narrow in their scope to be used in this way. Women with pelvic floor disorders commonly have interrelated problems, for example, bowel and urinary incontinence, incontinence prolapse, and prolapse and sexual dysfunction. This has driven the development of more generic urogynecology/pelvic floor questionnaires, covering a range of disorders. For these broader instruments, there is then a tension between the burden of providing sufficient detail and the lack of depth afforded by brevity. The aim was to utilize computer technology to provide an efficient, interactive, single instrument, addressing issues of feasibility faced with the use of paper questionnaires such as compliance, burden, and cost associated with entering, processing, and storing large volumes of clinical data (Figure 18. The purpose-built Microsoft Access “Q-Builder” software incorporated all the technical elements: physical layout and display (e. The system is forward-compatible with electronic data management software systems, allowing integration with other modalities such as new electronic results reporting and electronic patient records. Consultation with specialists in urology, gynecology, colorectal surgery, and sexual medicine identified additional items, whose format was unified to achieve consistency throughout. Paper and electronic versions were reviewed by the local maternity user group who provided critical structured feedback. Psychometric testing was carried out in 432 patients in primary and secondary care .
Of note order generic furosemide online blood pressure normal reading, negative P waves in lead 1 are never seen in left or right pulmonary vein foci discount furosemide line blood pressure stages, since the pulmonary veins are posterior in the chest order 40mg furosemide arteria carotis interna. A negative P wave in lead 1 suggests a left atrial appendage or lateral mitral annulus origin. As such, I recommend that no sedative be given when one is attempting to demonstrate spontaneous atrial impulse formation. Moreover, it is most commonly necessary to add pharmacologic agents to facilitate impulse formation. Because of the unreliability of seeing all potential sources of pulmonary vein foci, we do not rely on them for ablation of atrial fibrillation. An ectopic atrial arrhythmia was initiated from that ablation/mapping catheter as demonstrated by earliest activation from the distal tip of the ablation catheter with subsequent activation to the proximal portion of the pulmonary vein associated with a layer left atrial component. Thus, initiation of atrial tachyarrhythmias from the pulmonary veins by mechanical induction of catheter introduction itself can produce misleading rhythms that should not be targeted for ablation. Once the appearance of pulmonary vein foci has been suggested, transseptal catheterization should be performed. Although some investigators use a single transseptal puncture followed by introduction of two guidewires and then reintroduction of two sheaths, I prefer two (or occasionally three) separate transseptal procedures. I believe the latter approach is associated with less femoral vein bleeding and local complications as well as a lower incidence of persistent atrial septal defect following a procedure. Intracardiac ultrasound or transesophageal echocardiography may also be employed to facilitate catheter positioning. Once the left atrium is entered the goals for the procedure are to identify vein and/or branch of the vein from which the impulse arises and localize either the earliest site of activation within that vein or branch, or the segment from which the earliest activation is recorded. The initial method used was point-by-point activation mapping in the pulmonary veins. This method is still useful, particularly using electroanatomic mapping, which allows one to tag the anatomic location of individual potentials. The initiation of atrial ectopic impulse formation in the pulmonary veins only after a catheter has been introduced into the pulmonary veins does not signify that the source of atrial fibrillation has been identified. The catheter should be withdrawn to assess whether or not this impulse formation exists spontaneously. This is in contrast to an ongoing atrial tachyarrhythmia in which a pulmonary vein is explored and early activation found (Fig. One of the other clues that this rhythm was not flutter is simultaneous activation from high to low on the lateral right atrial free wall and on the septum. Ablation of the focal tachycardia, which was initially performed in the pulmonary vein, is now done by targeting the exit site from the vein at the ostial cuff, or more commonly, by isolating the entire vein. The halo catheter distally records the lateral isthmus and proximally the superior septum. The isthmus catheter is adjacent to the halo catheter distal, which was at the site of a prior ablation for proven isthmus-dependent flutter. The split electrograms are at the site of block produced by the prior linear lesion. The activation in the left superior pulmonary vein records a pulmonary vein potential of 130 msec prior to the P wave with a later left atrial potential (A*). Subsequent ablation of the pulmonary vein focus eliminated the need for antiarrhythmic therapy and the patient has been free of arrhythmia since. Occasionally, far field potentials can be recorded within pulmonary veins that confuse the issue. Because of this, some investigators suggest placing multipolar catheters in each pulmonary vein (primarily the superior pulmonary veins initially) to see the sequence of activation of impulse formation. An example of an atrial premature complex, mapped to the pulmonary vein, initiating atrial fibrillation, and successful ablation of that site is shown in Figure 13-89. In panel A of this figure, a premature atrial complex is seen in the middle of the tracing, which is associated with early activation in the pulmonary vein associated with a local left atrial electrogram, suggesting the recording site is at the ostial cuff. Following the next sinus beat another atrial premature beat from this site initiates atrial fibrillation. Another example of an atrial tachyarrhythmia that was demonstrated to initiate atrial fibrillation at other times is shown in Figure 13-90. Intracardiac recordings guided by the Carto mapping system showed this earliest activity arose from the left superior pulmonary vein. The local electrogram in sinus rhythm at this site showed a complex electrogram with left atrial activity followed by a sharp spike representing activity from the pulmonary vein. Atrial tachyarrhythmia begins on the subsequent beats, which is associated with early activity first in the pulmonary vein potential with subsequent left atrial activity. The Carto system was extremely useful in localizing the earliest site of activation P. Although most ectopic impulse formations initiating atrial fibrillation appear to arise from the pulmonary veins, other sites may also be responsible as mentioned above. Panel B: (bottom) Radiofrequency application at this site in sinus rhythm produces an accelerated rhythm from the pulmonary vein followed by sinus rhythm. Mapping and ablation of pulmonary vein foci is different from mapping atrial tachyarrhythmias, however. Mapping of pulmonary vein foci is limited by (a) ablation at sites that appear early but that are proximal to a more distal branching earlier site resulting in failure; (b) multiple foci are common (recurrences due to atrial ectopic formation in other pulmonary veins, antral sites proximal to the ablation, or at nonpulmonary vein related sites—perhaps only 65% arise in the pulmonary veins, 85% if antrum is included); (c) spontaneous or pharmacologically induced pulmonary vein foci are unreliable; (d) presence of atrial fibrillation prohibits identification of initiating foci; a high failure rate with most patients requiring 3 or 4 sessions; and (e) a high incidence of pulmonary vein stenosis. The latter complication is most frequently associated with the delivery of multiple lesions deep within the pulmonary veins at sites that are smaller than the ostial cuff. Pulmonary hypertension, pulmonary hemorrhage, hemoptysis, phrenic nerve paralysis, and strokes have all been reported. In none of the nonmap-guided approaches is pulmonary vein isolation attempted, and as such there is no real electrophysiologic endpoint. One cannot use termination of atrial fibrillation alone as and end point since it may occur spontaneously or additional mechanisms of initiation may still be present. Analog records of sinus rhythm and the onset of atrial tachycardia are shown in panel C. Atrial tachycardia then begins with reversal of the electrical signals in the left superior pulmonary vein with subsequent activation of the left atrium. This pulmonary vein focus was confirmed by electroanatomical mapping (panel B) to be just inside the left superior pulmonary vein. Ablation at this site immediately terminated the tachycardia and the patient has remained in sinus rhythm off of antiarrhythmic agents for 2 years. The technique of pulmonary vein isolation was developed by the group at Bordeaux214 and further popularized by Chen and his colleagues from Taiwan. This technique employs the use of a mapping catheter that has a spiral curved tip on which 10 to 20 electrodes are placed. The catheter is positioned at the ostium or just inside the ostium of the pulmonary vein and analysis of segmental activation is recorded. It is important to make sure one records activity from the ostial cuff and to stay out of the tubular portion of the vein (Fig. Some investigators have suggested the use unipolar recordings, but we have not found them of incremental value.