In the setting of conduction delay purchase indapamide 2.5 mg prehypertension fix, the electromechanical coupling of the heart is disrupted discount indapamide 1.5mg otc blood pressure extremely low, leading to dyssynchrony generic 2.5 mg indapamide with amex arrhythmia hypothyroidism. In addition to the three varieties of dyssynchrony already discussed, dyssynchrony can also be broken into “mechanical” and “electrical. Although the two are presumed to be closely linked, current measures of electrical and mechanical dyssynchrony have often shown poor agreement. Currently, the development of new measures of both electrical and mechanical dyssynchrony is an area of intense research. The main difficulty with all measures of mechanical dyssynchrony has been reproducibility across centers. Technical and interpretative variability across centers was thought to be a major reason behind the only modest predictive ability. Furthermore, the secondary end point of all-cause mortality reached statistical significance after 3 years of follow-up, and the survival curves continued to separate. The trial was not powered to compare mortality benefits between the two device groups. The American arm of the study concluded at 12 months, with the European arm proceeding to 24 months. Women have continually derived improved outcomes in multiple studies compared with men. Patients with nonischemic cardiomyopathy appear to be more likely to derive reverse ventricular remodeling than patients with ischemic cardiomyopathy. Initially, this was achieved via a thoracotomy; however, currently up to 98% of Bi-V devices are placed via a transvenous approach. Although now used infrequently, some patients are still referred for a thoracotomy after a failed transvenous approach. The procedure is performed in an electrophysiology laboratory under sterile conditions. All patients receive preprocedural antibiotics at least 30 minutes before the procedure. A subcutaneous pocket is first prepared, making sure that appropriate hemostasis is achieved. If high pacing threshold or diaphragm capture occurs, the lead should be repositioned. Because the pressure in the venous system is low, serious sequelae are unusual and cardiac tamponade rarely results. The time frame for the majority of dislodgements is the first 24 to 48 hours postimplantation, when patients resume activity. For that same reason, patients are encouraged to ambulate while still in-house to prevent any out-of- hospital dislodgement, which may have more serious consequences. Changing configurations for pacing can be very useful in cases of poor thresholds or diaphragmatic stimulation. Patents should have a posteroanterior and lateral chest ray to confirm lead position and to rule out pneumothorax. Despite the myriad of parameters of mechanical dyssynchrony that are available, none has been shown to be a practical and reliable predictor of response. Developing a measure of dyssynchrony that predicts response accurately and can be used across multiple care settings remains a challenge. Although many studies have shown some predictive ability of various imaging modalities, none to date has been shown to be a reliable predictor of response that could be utilized across multiple centers. Cardiac resynchronization therapy in patients with minimal heart failure: a systematic review and meta-analysis. Patient selection and echocardiographic assessment of dyssynchrony in cardiac resynchronization therapy. Developed with the special contribution of the Heart Failure Association and the European Heart Rhythm Association. Cardiac resynchronization therapy for patients with left ventricular systolic dysfunction: a systematic review. Guidelines for cardiac pacing and cardiac resynchronization therapy: the task force for cardiac pacing and cardiac resynchronization therapy of the European Society of Cardiology. The indications and technology of cardiac pacing continue to evolve, leading to a rapid increase in the number of pacemakers implanted. Pacemaker implantation rates increased from 329 implants per million in 1990 to 612 per million in 2002. In 2011, 400,000 cardiac devices were implanted and over 3 million people in the United States had implantable cardiac rhythm management devices. It is imperative that the physician caring for the pacemaker patient understand the basic physiology and technology of cardiac pacing and be able to apply these principles to effectively manage the unique problems with which these patients may present. Lithium batteries deplete over a more predictable time course than other types of compounds, such as zinc mercuric oxide, that were used in prior generations of devices. These circuits control programmable features of the output pulse, including amplitude and pulse width. A bandpass filter allows signals of a certain frequency range to be passed whereas signals of other frequency ranges are blocked or attenuated. Pacemakers use a bandpass filter to distinguish between cardiac depolarization and repolarization signals from extracardiac signals, such as myopotentials from the chest wall musculature. Some appropriate signals that pass through the filter are small in amplitude, and a sense amplifier increases the appropriate signal for the device to process. These circuits allow communication between an external programmer and the pulse generator for pacemaker programming or retrieval of information. Most modern pacemakers have computer chips with read-only memory and random access memory and therefore have enhanced capabilities, such as downloading of new features via telemetry and increased storage of diagnostic data. The conducting wire connects the stimulating and sensing electrodes to the terminal pin. The distal end of the lead that connects via a fixation mechanism to atrial or ventricular myocardium 4. Active fixation leads are secured to the endocardium using a “screw-in” mechanism. Over the past decade, active fixation leads have been implanted much more commonly. These types of leads have a lower rate of early dislodgement and yet higher chronic capture thresholds than passive fixation leads. This refers to the electrode configuration of the pacing lead or the configuration of the pulse generator. Polarity may be unipolar or bipolar; however, some pacemakers can be programmed to pace in one polarity and sense in another (only if a bipolar lead is present). Configuration in which the cathode (negative) is on the lead, usually the lead tip, and the anode (positive) is the pacemaker can. Oversensing of extraneous signals, especially pectoralis muscle activity (myopotentials), and inadvertent skeletal muscle stimulation may occur. Both electrodes are at the end of the lead—the cathode (negative) at the distal tip and the anode (positive) at the proximal ring. Myocardial stimulation occurs as electrons from the cathode travel through the myocardium and back to the anode.
The longer mesial groove extends There are three triangular ridges: one on each of the from a small mesial triangular fossa to the largest cen- two lingual cusps and one on the buccal cusp purchase genuine indapamide line arrhythmia kinds. The distal triangular fossa is so small that it appears to be at the outer edge of the central fossa buy genuine indapamide online blood pressure chart jnc. Marginal Ridge Grooves of Mandibular The three-cusp type of mandibular second premolar Premolars from the Occlusal View is the only premolar to have a lingual groove effective 2.5 mg indapamide hypertension and headaches. This lin- gual groove begins in the central fossa at the junction On both the two-cusp and three-cusp second premolar of the mesial and distal grooves, and extends lingually types, grooves crossing the marginal ridges (that is, mar- between the mesiolingual and distolingual cusps and ginal ridge grooves) are not common. Red lines accentuate differences in groove patterns and lingual taper found on different types of mandibular premo- lars. The mandibular first premolar has a lack of symmetry on the lingual half because the mesiolingual portion is “pushed in” or flattened, and is often crossed by a mesiolingual groove. It often has two separate pits that are not joined by a central groove due to the prominence of the transverse ridge. The three-cusp type mandibular second premolar can be as wide in the lingual half (or even wider) compared to the buccal half since it has two lingual cusps. The groove pattern is Y-shaped with the mesial, distal and lingual grooves intersecting in the central fossa. The two-cusp type mandibular second premolar is the most symmetrical of the three types, and may have a groove pattern that is U- or H-shaped. Suppose a patient just had all of his or her perma- lary premolar, as opposed to only one trait that nent teeth extracted and you were asked to find makes you think it belongs in the maxillary arch. This will permit you (extracted teeth or tooth models), select only to view the tooth as though you were looking the premolars (based on class traits). Name each ridge on the mandibular second premolar, two-cusp type, in Figure 4-28A. Also, name each ridge on the mandibular second premolar, three-cusp type, in Figure 4-28B. Ridges for two-cusp type: 1—mesial cusp ridge of buccal cusp; 2—buccal ridge; 3—distal cusp ridge of buccal cusp; 4—distal marginal ridge; 5—distal cusp ridge of lingual cusp; 6—mesial cusp ridge of lingual cusp; 7—mesial marginal ridge, 8—triangular ridge of buccal cusp; 9—triangular ridge of lingual cusp; 10—transverse ridge. Ridges for three-cusp type: 1—mesial cusp ridge of buccal cusp; 2—buccal ridge; 3—distal cusp ridge of buccal cusp; 4—distal marginal ridge; 5—distal cusp ridge of distolingual cusp; 6—mesial cusp ridge of distolingual cusp; 7—distal cusp ridge of mesiolingual cusp; 8—mesial cusp ridge of mesiolingual cusp; 9—mesial marginal ridge; 10—triangular ridge of buccal cusp; 11—triangular ridge of distolingual cusp; 12—triangular ridge of mesiolingual cusp. In this person, the buccal half of this maxillary second premolar is narrower mesiodistally than the lingual half, but in both types of maxillary premolars, the lingual half should be narrower mesi- odistally (as seen on the adjacent first premolar). During an oral examination, you are charting the teeth that are present in Heather’s mouth. All of her teeth are present, except on her left side; there is only one mandibular premolar, not two as expected. Name as many traits as possible that distinguish a mandibular second premolar (two-cusp type) from a mandibular first premolar in the same quadrant. Two premolars that most frequently have a groove crossing the mesial marginal ridge or one groove just lingual to it. Has a depression in the cervical one third of the mesial side of the crown and root. Based on 458 maxillary premolars, the crowns letters that refer to the data stated here. Buccal longitudinal crown depressions in the lars have three cusps (two lingual cusps). Based on measurements on 1472 teeth, maxillary occurring more frequently distal to the buccal premolar roots average within 1 mm of maxillary ridge. The single root on maxillary second premolars second premolars 55% of the time, and smaller averages 0. On 93 two-rooted maxillary first premolars, the of 209 maxillary second premolars. The crown outline of 234 maxillary premolars mea- between the buccal and lingual cusp tips of firsts sured greater buccolingually than mesiodistally: by is 5. On 641 maxillary second premolars, smooth buccal surface in the occlusal third with- only 37% of mesial marginal ridges and 30% of out depressions, 17% had a deeper depression in distal marginal ridges had a groove. On 234 maxillary first premolars, the cervical line of the buccal ridge, and only 3% had a deeper dis- curvature on the mesial averaged 1. On maxillary 74% had no discernible depressions, 25% had a second premolars, the difference between mesial deeper distal than mesial depression, and only 1% and distal curvature averages 0. On 1348 mandibular first premolars, the buccal (that is continuous with a mesial root depression) cusp is likely to have a notch on the mesial cusp on 100% of 100 teeth, whether single or double ridge 65% of the time, and on the distal cusp ridge rooted. On maxillary second premolars, 78% had a mesial molars, the buccal cusp is likely to have a notch root depression (none extending onto the crown on the distal cusp ridge 66% of the time, and on surface). On 238 mandibular first premolars, the cervical dency for a mesial bend was 23% and 17% on first line curvature on the mesial averaged 0. Roots of mandibular second premolars average lar second premolars, the cervical line curvature 0. On 321 mandibular first premolars, lingual cusps be located as much as 2 mm more occlusal on the averaged 3. On 818 mandibular second premolars, 90% had mesial root depressions and 86% had distal root the mesiolingual cusp larger and longer than the depressions that were deeper than on the mesial distolingual cusp; the two lingual cusps were 69% of the time. On 100 mandibular second equal in size on 3%, and the distolingual cusp was premolars, 81% had no mesial root depression larger on only 7%. On 229 mandibular three-cusp second premolars, a mesiolingual groove; 8% had a similar groove 56% have greater faciolingual bulk in the distal between the distal marginal ridge and the distal half, but 38% have greater bulk in the mesial slope of the lingual cusp. On 200 mandibular three-cusp second premolars, shorter than the buccal cusp, ranging from 0. On 200 mandibular second premolars, 24% had mesial marginal ridge groove, and 4% had a distal mesial marginal ridge grooves, and 11% had distal marginal ridge groove. They are also (c) important in maintain- views, the occlusal surfaces of all molars slope shorter ing continuity within the dental arches, thus keeping toward the cervix from mesial to distal (Appendix other teeth in proper alignment. This, along with the more cervical placement of (d) at least a minor role in esthetics or keeping the the distal marginal ridge, makes more of the occlusal cheeks normally full or supported. You may have seen surface visible from the distal aspect than from the someone who has lost all 12 molars (six upper and six mesial aspect (compare mesial to distal views in lower) and has sunken cheeks. The loss of a first molar is really noticed and missed by most people when it has been extracted. Molars have an occlusal (chewing) surface with three to five cusps, and their occlusal surfaces are larger than D. A The combined mesiodistal Compare extracted maxillary and mandibular molars width of the three mandibular molars in one quadrant and/or tooth models while reading about these dif- makes up over half of the mesiodistal dimension of ferentiating arch traits. From the occlusal view, the crowns of mandibular molars are oblong: they are characteristically much 2. That is, the mesi- view, maxillary molars have a more square or twisted odistal width on the buccal half is wider than on the parallelogram shape. See Table 5-1 for a sum- mary of the number of lobes forming first and second Mandibular molar crowns normally have four or five molars.
Multicrystal cameras oriented in a straight anterior projection are used for detection of count rates buy discount indapamide prehypertension pubmed. For the in vivo method order genuine indapamide online arteriogram complications, the patient is administered intravenous stannous chloride buy indapamide discount blood pressure 40 over 20. Then, a 2- to 3-mL sample of the patient’s blood is retrieved and bounded with technetium 99m pertechnetate. The stannous ions reduce the technetium, so they will not leak out of the tagged cells. The in vitro method binds the patient’s blood with the stannous ion and technetium prior to reinjection into the patient. Because multiple cardiac cycles are averaged to obtain the final images, this technique is not optimal for evaluating regional wall motion. The standard injection of 20 to 30 mCi of technetium 99m allows evaluation of perfusion and function in a single study. For example, if a region has a perceived fixed perfusion defect, yet wall motion is normal in the same region, artifact becomes a more likely consideration as the cause of the filling defect. However, wall motion abnormalities are typically not seen in ischemic segments after exercise nuclear testing because of the delay between peak stress and image acquisition. Comparison of this method with two-dimensional echocardiography in the evaluation of regional wall motion has shown good correlation between the two. Nuclear scintigraphy with 99m technetium pyrophosphate is used in the diagnosis of cardiac amyloidosis. Technetium pyrophosphate is a bone tracer that binds to the calcium in amyloid deposits, particularly in transthyretin amyloidosis; uptake is usually absent in light chain amyloid heart disease. Thus, this test is commonly used to diagnose transthyretin amyloidosis and differentiate it from light chain disease. Uptake is graded based upon visual assessment as well as comparing uptake in the heart versus the contralateral lung on planar images. Radiotracer analogues of sympathetic nervous system factors have been used to assess myocardial innervation and predict risk in certain conditions. The most striking finding was the greater than 99% negative predictive value; patients with normal uptake had very few cardiac events. Positron imaging agents can be divided into blood flow tracers and metabolic radiopharmaceuticals. A number of radiopharmaceuticals exist for the assessment of myocardial blood flow. Rubidium 82, the most readily used blood flow tracer, can be generated on-site without the use of a cyclotron. Much like thallium 201, rubidium 82 is a potassium analogue that is actively transported into myocytes through the Na–K pump. Because of a short half-life (76 seconds), rubidium 82–based imaging protocols can be used to assess myocardial blood flow rapidly (within 1 hour). Other perfusion agents include the cyclotron-produced nitrogen 13 ammonia (half-life 10 minutes) and oxygen 15 water (half-life 123 seconds). Image quality with oxygen 15 water is poor and requires extensive processing to subtract the blood pool, 13 thus is rarely used in current practice. Rb 82 and N-ammonia are the perfusion tracers that are used in clinical practice, with Rb 82 carrying the distinct advantage of requiring only a 13 generator instead of a cyclotron. The image quality of N-ammonia is excellent, although the impracticality of cyclotron production in most facilities is a limiting factor for this agent. There is diminished oxidation of long-chain fatty acids and increased use of glucose as a secondary fuel source during ischemia or hibernation. The release of this product of β-oxidation is reflective of long-chain fatty acid oxidation in myocardium. Measuring the production of [ C]carbon dioxide in this setting correlates with myocardial oxygen consumption. An attenuation scan is performed that allows the density of the surrounding thoracic structures to be subtracted to leave only cardiac count activity. After the attenuation scan, the positron-emitting radiopharmaceutical is injected, and images are obtained 2 to 5 minutes later. As mentioned earlier in the chapter, two photons are created by the annihilation of the emitted positron colliding with the nearest electron it meets in the tissue surrounding it. These two photons travel exactly 180° apart while the patient is lying in the circular scanner. The detector/analyzer merely has to “accept” the signal it receives only if a simultaneous signal strikes the detector directly across from it in the scanner. This dramatically improves the signal-to-noise ratio that can be achieved during imaging. As mentioned before, the ability to quantitate absolute blood flow regionally and globally may help improve the diagnosis of coronary ischemia in the setting of severe multivessel disease and balanced ischemia. The presence of a flow–metabolism mismatch, which indicates underperfusion in the presence of metabolically active myocytes, suggests hibernating myocardium. This utility of nuclear imaging has found increasing application in the selection of patients for revascularization who have ischemic cardiomyopathy and heart failure with low ejection fraction. Under fasting conditions, myocardial cells shift to utilizing predominantly fatty acids. Inflammatory cells in cardiac sarcoidosis utilize glucose because of high metabolic demands, even during fasting. Sarcoidosis nuclear protocols vary among institutions, but attempt to minimize physiologic glucose uptake in normal myocardial tissue. Patients are advised to prepare for the exam with a prolonged fast (12 to 18 hours) and high-protein, low-carbohydrate diet the day before the exam. Skiles, Gregory Bashian, and Santosh Oommen for their contributions to earlier editions of this chapter. Identification and differentiation of resting myocardial blood flow in man with positron emission tomography, 18F-labeled fluorodeoxyglucose and N-13 ammonia. Thallium-201 for myocardial imaging: relation of thallium-201 to regional myocardial perfusion. Technetium-99m hexakis 2-methoxyisobutyl isonitrile: human biodistribution, dosimetry, safety, and preliminary comparison to thallium-201 for myocardial perfusion imaging. Myocardial oxygen demand is determined by contractility (inotropy), heart rate (chronotropy), and wall stress (preload + afterload). Although a number of agents have been evaluated in combination with echocardiography, dobutamine is most widely used. Low-dose dobutamine has positive inotropic effects mediated through cardiac α - and β -receptors. At higher doses, it has positive1 1 chronotropic effects mediated through β -receptors. These agents result in perfusion abnormalities by causing blood to be preferentially shunted away from myocardial segments supplied by stenotic coronary arteries (i. However, because of the shorter duration of action of adenosine, the echocardiographic findings tend to be less pronounced and of shorter duration, resulting in a lower sensitivity. Tachycardia induced by atrial pacing is an alternative to pharmacologic testing in patients that cannot exercise and in whom pharmacologic agents are contraindicated.
By O. Rathgar. Bryn Mawr College.