A: At a paced cycle length of 600 msec cheap sildigra 100 mg overnight delivery, the A-H is 95 msec and the H-V is 50 msec order sildigra with american express. Shortening the cycle length to 350 msec (B) results in A-V nodal Wenckebach block; that is purchase sildigra with a mastercard, progressive A-H prolongation (140, 200, 225 msec) terminating in block of the P wave in the A-V node (no His bundle deflection after the fourth paced beat). The stimulus is delivered, which fails to capture the atrium, which has been previously depolarized by an atrial echo (Ae, arrow) that is due to A-V nodal reentry. The exact proportion of patients demonstrating V-A conduction varies from 40% to 90% and depends on the patient population studied. The incidence of V-A conduction is higher in patients with normal antegrade conduction, although it is well documented that V-A conduction can occur in the presence of complete A-V block if block is localized to the His–Purkinje system. This divergence from the rest of the literature obviously reflected a selected patient population. In 1981, Akhtar74 reviewed his data, which revealed that if retrograde conduction is present, it will be better than antegrade conduction in only one-third of instances. Most of such instances involve patients with either bypass tracts or dual A-V nodal pathways (see Chapters 8 and 10). Our own data have revealed that in 750 patients with intact A-V conduction, antegrade conduction was better (i. These data, which exclude patients with bypass tracts, are comparable to those of Akhtar who only considered patients with intact retrograde conduction. The ability to conduct retrogradely during ventricular pacing is directly related to the presence and speed of antegrade conduction. Patients with prolonged P-R intervals are much less likely to demonstrate retrograde conduction. Thus, A-V nodal conduction appears to be the major determinant of retrograde conduction during ventricular pacing. As with atrial pacing, ventricular pacing is begun at a cycle length just below the sinus cycle length. The paced cycle length is gradually reduced until a cycle length of 300 msec is reached. Further shortening of the ventricular-paced cycle length may also be used, particularly in studies assessing rapid retrograde conduction in patients with supraventricular arrhythmias (see Chapter 8) or during stimulation studies to initiate ventricular arrhythmias (see Chapter 11). During ventricular pacing, a retrograde His deflection can be seen in the His bundle electrogram in the majority of cases. We have used the Bard Electrophysiology Josephson quadripolar catheter for obtaining distal and proximal His deflections (Chapter 1). Using this catheter, we observed a retrograde His potential in 86 of 100 consecutive patients in whom we attempted to record it. Ventricular pacing at the base of the heart opposite the A-V junction (Para-Hisian pacing) facilitates recording a retrograde His deflection, particularly when the His bundle recording is made with a narrow bipolar signal (i. Retrograde His deflections are much less often seen in the presence of ipsilateral bundle branch block. In all instances, V-H (or stimulus-H) interval exceeds the anterograde H-V by the time it takes for the stimulated impulse to reach the ipsilateral bundle branch. This response occurred because the effective refractory period of the His–Purkinje system was 350 msec, which is longer than the paced cycle length. The normal response to ventricular pacing is a gradual prolongation of V-A conduction as the ventricular-paced cycle length is decreased. Retrograde (V-A) Wenckebach-type block and higher degrees of V-A block appear at shorter cycle lengths (Fig. Although Wenckebach-type block usually signifies retrograde delay in the A-V node, it is only when a retrograde His deflection is present that retrograde V-A Wenckebach and higher degrees of block can be documented to be localized to the A-V node (Fig. This extra beat is termed a ventricular echo and is not infrequent during retrograde Wenckebach cycles. Ventricular echoes of this type are due to reentry secondary to a longitudinally dissociated A-V node and require a critical degree of V-A conduction delay for their appearance. Patients with a dual A-V nodal pathway manifesting this type of retrograde Wenckebach and reentry are generally not prone to develop clinical supraventricular tachycardia that is due to A-V nodal reentry (see Chapter 8). Because a retrograde His bundle deflection may not always be observed in patients during ventricular pacing, in the presence of V-A block, localization of the site of block in such patients must be inferred from the effects of the ventricular-paced beat on conduction of spontaneous or P. Thus, one localizes the site of delay by analyzing the level of concealed retrograde conduction. If the A-H interval of the spontaneous or induced atrial depolarization is independent of the time relationship of ventricular-paced beats, then by inference, the site of retrograde block is infranodal in the His–Purkinje system. On the other hand, variations in the A-H intervals that depend on the coupling interval of the atrial complex to the ventricular-paced beat, or failure of the atrial impulse to depolarize the His bundle, suggest retrograde penetration and block within the A-V node (Fig. Another method of evaluating the site of retrograde block in the absence of a recorded retrograde His potential is to note the effects of drugs, such as atropine or isoproterenol, which affect only A-V nodal conduction, on V-A conduction. Improvement of conduction following administration of these drugs suggests that the site of block is in the A-V node. On the bottom, ventricular pacing at the same cycle length is associated with the V-H interval of 70 msec. B: During sinus rhythm at a cycle length of 550 msec, the right bundle branch block is present with an H-V interval of 80 msec. The presence of a retrograde His deflection allowed the site of block to be localized to the A-V node. After the third paced ventricular complex, pacing is terminated (open arrow) and a return beat appears that has the same configuration as the subsequent sinus beat. In contrast to the development of the V-A Wenckebach, if one can record a retrograde His deflection, it is possible to demonstrate that V-H conduction remains relatively intact at rapid rates despite the development of retrograde block within the A-V node (Fig. Refractory Periods The refractoriness of a cardiac tissue can be defined by the response of that tissue to the introduction of premature stimuli. In clinical electrophysiology, refractoriness is generally expressed in terms of three measurements: relative, effective, and functional. The definitions differ slightly from comparable terms used in cellular electrophysiology. Despite the presence of a visible retrograde His deflection the site of block is shown to be the A-V node because antegrade A-V nodal conduction (A-H) depends on the relationship of the sinus beats A to the ventricular complexes. In humans, refractory periods are analyzed by the extrastimulus technique, whereby a single atrial or ventricular extrastimulus is introduced at progressively shorter coupling intervals until a response is no longer elicited. Determining refractoriness at shorter cycle lengths may be useful to assess refractoriness in the heart at rates comparable to those during spontaneous tachycardias. The extrastimulus is delivered after a train of 8 to 10 paced complexes to allow time for reasonable (≥95%) stabilization of refractoriness, which is usually accomplished after the first three or four paced beats. The specific effects of preceding cycle lengths on refractoriness will be discussed later. In most electrophysiologic laboratories, stimulus strength has been arbitrarily standardized as being delivered at twice-diastolic threshold. Some standardization of stimulus strength is necessary if one wishes to compare atrial and/or ventricular refractoriness before and after an intervention. Although use of current at twice-diastolic threshold gives reproducible and clinically relevant information, and has a low incidence of nonclinical arrhythmia induction, the use of higher currents has been suggested. An example of a strength–interval curve to determine ventricular refractoriness is shown in Figure 2-29.
Only the difference in antegrade conduction over either the fast- or slow-conducting A-V nodal dual pathways alters the tachycardia cycle length and the R-P/P-R ratio sildigra 100mg overnight delivery. In the right-hand panel order sildigra on line amex, the second tachycardia with a cycle length of 400 msec is present with an identical retrograde activation sequence and identical R-P intervals generic sildigra 50 mg mastercard. The tachycardia is slower because antegrade conduction proceeds over the slow A-V nodal pathway. First, at short coupling intervals or paced cycle lengths, intramyocardial conduction delay can occur, producing a prolonged V-A interval. Second, short cycle lengths or coupling intervals may encroach on the refractoriness of the bypass tract, causing some decremental conduction. Third, rarely, one can observe longitudinal dissociation in the bypass tract such that it can exhibit a short and long conduction time. Finally, an increased V-A interval is the rule when one stimulates from the chamber contralateral to a free-wall bypass tract (e. This phenomenon is identical to the spontaneous effect of bundle branch block ipsilateral to the bypass tract (see following). An increase in the V-A conduction time in response to ventricular pacing has been used as a diagnostic criterion for a free-wall bypass tract in the ventricle contralateral to the site of stimulation. Paradoxically shorter V-A intervals may be observed during right ventricular stimulation in the presence of right free-wall bypass tracts. To distinguish intramyocardial delay from delay in the bypass tract, one must analyze the atrial and ventricular electrograms at the bypass tract site (e. In this latter instance, the change is related to a different activation wavefront approaching the ventricular insertion of the bypass tract. Once engaged from a different direction, there will be a change in local V-A interval, which thereafter remains fixed regardless of the paced rate. This suggests that in those instances in which a V-A delay occurs in response to ventricular stimulation, the delay results from a change in intramyocardial activation. Thus, this finding alone should not be considered diagnostic of a bypass tract, as some investigators have suggested. The retrograde atrial activation sequence will be eccentric if the bypass tract is located on the free wall of atria, that is, if it is nonseptal. The investigator, however, should be aware that during ventricular pacing activation to the atria may proceed over both the normal atrioventricular conduction system and the bypass tract, leading to a fusion of atrial activation. If retrograde A-V nodal conduction is very rapid, stimulation in the contralateral ventricle (e. The investigator can pace at shorter cycle lengths in order to produce A-V nodal conduction delay or block in order to promote conduction over the bypass tract (Fig. Therefore, when using the atrial activation sequence during ventricular pacing to localize the bypass tract, it is necessary to demonstrate that retrograde conduction proceeds solely over the bypass tract during ventricular pacing. When the paced cycle length is reduced to 500 msec (right panel) A-V nodal block is produced allowing manifest retrograde conduction over a left lateral bypass tract. Changes in atrial activation, either spontaneously or in response to ventricular stimulation, can demonstrate the presence of multiple bypass tracts (Fig. If the bypass tract is opposite the site of ventricular stimulation, the V-A interval prolongs during pacing. This can be readily accomplished by observing the response to ventricular pacing during the tachycardia. One must be careful to exclude a “pseudo–V-A-A-V response” produced by a very long V-A, which exceeds the paced cycle P. This can be recognized because the first “A” of the “pseudo”–V- A-A-V response occurs at the paced cycle length. Another reason for a pseudo–V-A-A-V response is A-V nodal tachycardia with a long H-V such that the A occurs before the V (Fig. These responses require intact V-A conduction which is present in perhaps 80% of patients in the absence of bypass tracts. The only difference is the lengthening of V-A intervals, which is characteristic of left-sided bypass tracts during right ventricular pacing. In each panel ventricular overdrive pacing demonstrating retrograde conduction is shown in blue. Recordings should be made using a multipolar catheter and, if possible, one should try to bracket the earliest; that is, demonstrate later activation on either side of the earliest site. In such cases more distal left atrial sites must be mapped through a patent foramen ovale or via a transseptal approach (Fig. Thus, careful mapping of multiple sites around the tricuspid and mitral valves is required for proper diagnosis. This may require a superior vena cava approach and/or the use of catheters with deflectable tips. Specially designed multipolar catheters that can record around the tricuspid ring can be especially useful. This could be a specially designed “halo” catheter or a deflectable 10–20-pole catheter which can be positioned around the tricuspid annulus. While some investigators have employed a fine catheter in the right coronary artery, the potential for endocardial damage and subsequent long-term development of coronary atherosclerosis exists; therefore, I believe this technique should be avoided. As expected, the V-A intervals measured from intracardiac electrograms are more accurate than R-P intervals. The shortest V-A interval we have observed in a septal bypass tract in an adult patient is 70 msec. This is nearly identical to the data of Ross and Uther,124 who found that a V-A interval of 60 msec was the best value to discriminate between the two. Upon cessation of pacing there is a V-A-A- V response prior to resumption of the tachycardia. B: Ventricular pacing is associated with retrograde conduction, but upon cessation of pacing the tachycardia resumes following a V-A-V response. The former response is diagnostic of atrial tachycardia, and the latter excludes it. An easy way to do this is to note the response to ventricular stimulation during the tachycardia. An exception to this can occur if there are dual A-V nodal pathways and ventricular pacing shifts antegrade conduction to the slow pathway, yielding a long postpacing cycle. This can be sorted out by comparing the V-A interval during pacing to that during the tachycardia. Finally, para-Hisian pacing can be used to document the presence of an accessory pathway; when a septal pathway is present the St-A will be the same with His capture and pure ventricular capture; while if an accessory pathway is absent, a marked difference between stimulus to A when His capture is lost and pure ventricular pacing ensues. All of the maneuvers discussed above are not useful in the presence of very decremental pathways or left free-wall pathways. In the presence of a septal accessory pathway the difference always is more positive than 30 msec. A limitation of this method is that the H-A interval cannot be measured during ventricular pacing in approximately 15% of cases.
The request for a preflight screening may be triggered because a pas- senger makes a statement regarding a medical condition or may appear obvi- ously ill or in distress proven sildigra 25 mg. This consultation aims to ensure reso- lution of the prior medical emergency and determine the passenger’s current fitness for air travel discount sildigra express. For patients identifed as having a potentially communicable disease buy discount sildigra 50 mg online, there may be questions regarding the risk of exposure of other passengers and any precautions that may be necessary. Other providers that may perform a ftness-to-fy evaluation include the passen- ger’s own physician, or a physician at a clinic or hospital where the passenger has been evaluated for a medical event. Recommendations must avoid any discrimination against passengers and ensure the right to free movement . Guidelines for prefight screenings have been published by the International Air Transport Association , and specifc recommendations regarding prefight medical therapies are provided in Chapter 14 of this book. Individual airlines may also have their own medical guidelines for passenger ftness to fy. Other occu- pational health questions are typically addressed by the medical department of the airline. When a potential medical emergency involves a member of the fight crew, recommendations should always be discussed with the pilot in command to obtain consensus on the best course of action. In some cases, a pilot may be the patient and diversion may be advisable even in circumstances where continuation to des- tination would be appropriate for a passenger (e. In most cases, the recommendation will be for fight crew members with an ongoing medical concern to be removed from onboard duties, as appropriate considering the type of medical concern, available staff, and needs for safe operation of the aircraft. Upon completion of the fight, airline poli- cies should address the mechanism for a fight crew member to be cleared to return to fight duties. Additional recommendations to cabin crew may be provided to protect against disease transmission, such as use of face masks, gloves, and strict hand hygiene. In some cases, passengers may be moved away from other passengers if space allows. The Public Health Agency of Canada has similar regional Quarantine Stations to which their respective reports should be made. Following notifcation, the public health entity has the authority to quarantine passengers, though this is exceedingly rare. In most cases, information is obtained from the airline, the passenger may be interviewed or evaluated at the airport, and follow-up may be performed as determined by the public health entity. Once communications are established, the con- sultation may be led onboard by the pilot in command, copilot, or other fight crew 156 C. Radio communications are typically established through regional communica- tions centers. A consideration in using radio communications is that different fre- quency bands are utilized for different parts of the United States and Canada, as they are across the world. As the fight moves away from one radio tower, the signal may fade and the aircraft may need to switch frequency. Usually it is the most effcient means of communication, yet satellite positioning may limit the ability to communicate and lead to dropped calls. It is not normally used over continental North America, where the radio network is easily accessed by aircraft; instead, it is used more commonly for transoceanic fights. Internet communication systems are increasingly becoming available on com- mercial airlines. The nature of the event and airline policies also infuence whether the fight attendant asks for an onboard medi- cal volunteer to assess the passenger and assist in the management of the medical emergency. This information may be provided from the pilot, from the fight attendant, or directly from a medical volunteer. Additional recommendations may include whether to divert the aircraft or continue to the intended destination. The fnal recom- mendation may be to divert to the closest airport, divert to a more appropriate desti- nation based on the patient’s condition, or continue to the intended destination if time to the intended destination is not determined to be medically signifcant for the patient’s condition. This recommendation may be infuenced by the immediate need for additional medical interventions, a determination that the patient will need to be transported to the hospital, or the need to medically screen the passenger prior to making a connection following an onboard medical emergency. For example, the decision to divert an aircraft due to a medical emergency lies solely with the onboard pilot in command and the airline’s dispatch center. The pilot in command also makes the fnal determination of whether a pas- senger can board an aircraft, in consideration of the safety of that passenger and everyone else on board. In the United States, no legal requirement exists requiring interven- tion by onboard medical volunteer providers. First, the type of provider who is accepted by the airline may vary from airline to air- line; some airlines may require proof of licensure prior to rendering assistance. The medical volunteer should be sober and able to provide a business card or other identifcation to the fight attendant. The pilot in command is the primary incident commander and utilizes the information avail- able from all sources when making critical decisions. This may include input on use or future replenishment of the onboard medical kit, coordination of ongoing medical care upon arrival, and ensuring appropriateness of any major decisions such as aircraft diversion. All medical providers involved in an in-fight event offer advice to these primary decision makers. For example, the average aircraft takes 20–30 min to descend and land from cruising altitude. A fight with 30 min or less remaining will not save any time by diverting to an alternate airport. Additionally, different airports will have different nearby medical facilities and the closest airport may not be located near facilities that would best serve the patient. Additional operational considerations include whether specifc airports can handle the type of aircraft involved, as well as weather and/or operational considerations. Thus, dispatch must be involved in assessing and making deci- sions regarding any potential diversion. This may include fights over the oceans or poles, fights over countries where political or other considerations preclude landing, or situations where it is unsafe to immediately land as is the case with overweight aircraft soon after takeoff. If no further care is likely to result in return of circulation, it may be medically appropriate to cease resuscitation efforts. This process should be undertaken by the appropriate emergency medical service where the fight lands by following local procedures. If resuscitation efforts have ceased and there are no signs of life, there is no longer a medical reason to divert the aircraft. An automatic diversion may create additional prob- lems, particularly regarding disposition of human remains across national borders. However, there may be other company reasons to divert, including crew exhaustion, bio- logical contamination, or other operational concerns.
Association between implementation of a medical team training program and surgical morbidity 120 mg sildigra fast delivery. Development and validation of assessment measures for a newly developed physical examination simulator order generic sildigra line. A comprehensive anesthesia simulation environment: Recreating the operating room for research and training best sildigra 100 mg. To the point: Reviews in medical education online computer assisted instruction materials. The current status of robotic pelvic surgery: Results of a multinational interdisciplinary consensus conference. Simulation-based assessment and retraining for the anesthesiologist seeking reentry to clinical practice: A case series. Laparoscopic training on bench models: Better and more cost effective than operating room experience? Physical reality simulation for training laparoscopists in the 21st century: A multispecialty, multi-institutional study. Virtual reality training improves operating room performance: Results of a randomized, double-blinded study. Learning curves and the impact of previous operative experience on performance on a virtual reality simulator to test laparoscopic surgical skills. Randomized clinical trial of virtual reality simulation for laparoscopic skills training. Virtual reality and computer-enhanced training devices equally improve laparoscopic surgical skill in novices. Virtual reality simulation training can improve technical skills during laparoscopic salpingectomy for ectopic pregnancy. Standing on the shoulders of giants: Contemplating a national curriculum for surgical training in gynaecology. Effect of short term pretrial practice on surgical proficiency in simulated environments: A randomized trial of the “preoperative warm-up” effect. Virtual reality robotic surgery warm-up improves task performance in a dry laboratory environment: A prospective randomized controlled study. High fidelity simulation-based team training in urology: A preliminary interdisciplinary study of technical and non-technical skills in laparoscopic complications management. Use of high fidelity operating room simulation to assess and teach communication, teamwork and laparoscopic skills: Initial experience. Evaluation of a preoperative checklist and team briefing among surgeons, nurses, and anesthesiologists to reduce failures in communication. A systematic review of the effectiveness, compliance, and critical factors for implementation of safety checklists in surgery. The science of medical decision making: Neurosurgery, errors, and personal cognitive strategies for improving quality of care. Disclosing medical errors to patients: Attitudes and practices of physicians and trainees. The emotional impact of medical errors on practicing physicians in the United States and Canada. Disclosure of adverse events and errors in surgical care: Challenges and strategies for improvement. Disclosure and apology: Patient-centered approaches to the public health problem of medical error. Nurturing a culture of patient safety and achieving lower malpractice risk through disclosure: Lessons learned and future directions. Malpractice reform: Opportunities for leadership by health care institutions and liability insurers. Kelleher Understanding the patient perspective of any medical condition allows us to treat our patients more effectively, compassionately, and completely. Lower urinary tract dysfunction and genital prolapse can be described by objective investigations and clinical examination. Ignoring the patient perspective can, however, lead to inappropriate conclusions regarding treatment desire, appropriate treatments to select, and treatment efficacy. How conditions affect patients’ lives and how they hope to benefit from interaction with the medical world can only be answered by the patients themselves. In Chapter 12, Coyne and Sexton introduce the concept of patient-reported outcomes, from their development through their selection and usage for clinical trials and clinical practice. Increasingly, the patient perspective of treatment success is recognized as the most important goal of medical interventions. Whether the patient is satisfied with their treatment, whether it improves their symptoms sufficiently, and whether they wish to persist with treatments outside the context of clinical trials are all hallmarks of a successful intervention. The authors describe how the bother caused by a problem can be addressed and measured in a reproducible way and how to select the best tools to use in various different settings. In Chapter 13, the individual questions used to measure the quality-of-life outcomes of patients with lower urinary tract dysfunction are described in greater detail. Understanding as much as possible about the content of the questionnaire, its previous usage, size, etc. Kopp and Evans focus on patient satisfaction, expectations, and goal achievement in Chapter 14, a new edition to this volume of the textbook. It is now increasingly recognized that setting realistic patient goals and expectations for treatment are of paramount importance to satisfactory treatment outcome. Addressing patient goals before an intervention supports dialogue with a patient and ensures that they understand what a treatment is likely to achieve and helps the clinician understand what a patient would like the treatment to do. This is a very important chapter and highlights the fact that clinicians and patients are not always on the same wavelength regarding the expectation of an intervention and what signifies treatment success. How to measure goals and patient satisfaction has evolved considerably, and while we all undoubtedly address various aspects of this in our clinical practice, how best to do it and what instruments are available to do it properly may not be so clear. In Chapter 15, Domoney and Symonds have updated their chapter from the previous edition of this textbook to include new questionnaires to assess sexual function. The assessment of sexual function in a standardized fashion is crucial to understand the problems that patients are experiencing, and whether treatments impact positively or indeed negatively on this important aspect of their lives. So many of the problems affecting the lower genital and urinary tracts impact on sexual function, and so often it is assumed that treatments improve it. Without being able to measure it in a reproducible and meaningful way, we are unable to draw these conclusions. In Chapter 16, Mohamed, Chatoor, and Williams describe questionnaires used to assess bowel function. Many patients with lower urinary tract dysfunction and genital prolapse have associated bowel symptoms. Increasingly, we are working as part of a multidisciplinary team to assess and treat all aspects of a patient’s concerns from the outset. The inclusion of clinicians trained in the clinical assessment and treatment of lower bowel dysfunction is recognized as well as the use of questionnaires to identify bowel problems as part of the initial patient evaluation.
By Z. Malir. University of Minnesota-Duluth.