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Assessment of Infarct Size 99m 21 Contemporary studies have used Tc-sestamibi to provide an assessment of infarct size buy cleocin gel 20 gm acne popping. Because clearance from the myocardium after initial uptake of this tracer is minimal buy discount cleocin gel 20gm on line skin care shiseido, images acquired even hours after initial injection represent a “snapshot” of blood flow conditions and tracer uptake at the time of injection cleocin gel 20gm amex skin care laser clinic birmingham. Infarct size as assessed by quantitative analysis of rest sestamibi uptake has been validated against 21 many other measures of infarct size 20 gm cleocin gel acne 7 day detox. The change in defect size between the initial image acquired in the acute stage and the later image represents the magnitude of salvaged myocardium from reperfusion. Assessment of Myocardial Perfusion During Stress Coronary blood flow must respond rapidly to changing metabolic conditions and oxygen demand to meet the nutrient needs of myocytes being called on to contract more frequently and with more force. Oxygen extraction by the myocardium is nearly maximum at rest; thus any increase in oxygen demand can be met only through increasing coronary blood flow to deliver more oxygen per unit time (see Chapter 57). The major determinants of coronary blood flow include the perfusion pressure at the head of the system (principally aortic diastolic pressure) and the downstream resistance, residing predominantly in the coronary arteriolar bed. Because aortic diastolic pressure during exercise varies little from the value at rest, the major mechanism responsible for increasing coronary blood flow during stress involves a reduction in coronary vascular resistance. During exercise stress, coronary blood flow can increase approximately two to three times above levels at rest. During pharmacologic stress to minimize coronary arteriolar resistance, using intravenous coronary arteriolar vasodilator agents such as dipyridamole, adenosine, or regadenoson (discussed later), coronary blood flow can increase up to four to five times above rest levels. The magnitude of blood flow increase secondary to any stress relative to flow values at 22 rest is termed the coronary blood flow reserve. It should be extracted rapidly (from the blood into the myocyte), because the hemodynamic conditions during peak stress are not maintained for long periods. The ideal tracer also should be extracted as completely as possible out of the bloodstream, and it should be retained in myocardium for a sufficient period to be imaged. Moreover, perturbations in metabolic conditions, such as ischemia or common cardioactive drugs, should neither influence nor interfere with 4 uptake so that the resulting regional tracer concentrations primarily reflect myocardial perfusion. The ideal perfusion tracer would track myocardial blood flow across the entire range of physiologically relevant flows (red line). The different tracers reach a plateau at different levels of myocardial blood flow, as demonstrated in this schematic example based on multiple studies in animal models. The 140-keV energy spectrum of Tc perfusion tracers results in less scatter and soft tissue attenuation, with improved spatial resolution compared with 4 thallium. However, the first-pass myocardial extraction of both sestamibi and tetrofosmin is only in the 60% range with nonlinear extraction at high flows. Nonetheless, regional differences in myocardial tracer uptake during exercise or pharmacologic stress have provided important 6 diagnostic as well as prognostic information. In animal models in which discrete coronary stenoses of varying degrees are induced, coronary blood flow at rest is maintained by autoregulatory dilation of the downstream arteriolar resistance vessels until a stenosis between 80% and 90% of vessel diameter is reached (Fig. As stenosis severity increases further, the arteriolar vasodilatory capacity to maintain flow at rest is exhausted, at which point coronary blood flow at rest diminishes (see Chapter 57). A, At rest, flow is driven by the pressure head (P) at the proximal end of the system. R2 represents the coronary arteriolar resistance, which predominantly regulates coronary blood flow. At rest in the normal vessel (left vessel on the drawing), some vasoconstrictor resistance is present. In the setting of an epicardial coronary stenosis (right vessel), blood flow at rest can be maintained, but at the expense of lowering of coronary resistance downstream (R2 decreased) by autoregulatory dilation of the arterioles. Thus, with lower resistance, flow at rest may be maintained despite the lower pressure head at the distal end of the stenosis. B, With demand stress or with administration of a coronary arteriolar vasodilator such as dipyridamole or adenosine, perfusion increases substantially in the area supplied by the normal epicardial artery (left vessel on the drawing) as resistance (R2) becomes minimal. However, blunted flow reserve is seen in the area supplied by the stenosis (right vessel), because most of the vasodilator reserve at the R2 level has been used to maintain flow at rest. Thus, heterogeneity of flow is established (based on presence of upstream stenosis) and can be imaged with a perfusion tracer as a defect in the territory supplied by the stenotic vessel. By contrast, maximum coronary blood flow reserve begins to decrease when the upstream coronary stenosis reaches 50% diameter. Three levels of resistance influence coronary blood flow: that provided by the large-conductance epicardial vessels, designated R1; the coronary arteriolar resistance, R2; and the resistance in the subendocardium by wall tension from the ventricular chamber, R3 (Fig. Under normal conditions, most of the resistance at rest is provided by R2, and most of the increase in coronary flow during heightened demand occurs through reduction of resistance at this level, potentially increasing flow as much as four times as demand increases. Normal epicardial vessels dilate slightly (R1 decreases slightly) in response to increased coronary flow as a consequence of normal endothelial cell function. Depending on the type of exercise performed, the R3 component may remain unchanged or may increase, with an increase in chamber radius and wall tension. Achieving maximal flow is predominantly 22 dependent on the vasodilatory capacity of the downstream resistance vessels. With a coronary stenosis, in which some vasodilatory reserve has been used to maintain flow at rest, less vasodilatory reserve is available to minimize resistance during stress. Thus, in a vessel with a moderate stenosis, coronary blood flow reserve is blunted and detectable by a perfusion tracer (Fig. Stenoses may not be discrete, the length and complexity of the stenosis may affect the coronary reserve, and impaired endothelial function plays a role (see Classic References, Gould). In patients with preserved endothelial function, the increased coronary flow during stress leads to coronary arterial and arteriolar vasodilation, contributing to maximal coronary flow reserve. Endothelial function often is abnormal, with early atherosclerosis or risk factors for atherosclerosis contributing to the blunting of coronary flow reserve. The development of collaterals to the distal perfusion bed of a myocardial territory with a severe 22 upstream coronary stenosis also influences blood flow at rest and during stress. Left, Myocardial blood flow profiles at rest and stress of two myocardial regions, with region S (septum) supplied by a normal epicardial artery and region L (lateral wall) by an artery with significant epicardial coronary stenosis. Right, Perfusion tracer uptake profile is demonstrated with myocardial blood flow on the y axis. In the resulting perfusion images, a relative “defect” of tracer uptake is seen in the lateral wall compared with the septum, whereas both regions demonstrate similar tracer uptake at rest. The lateral wall thus demonstrates a reversible perfusion defect, reflecting the blunted coronary blood flow reserve and indirectly reflecting the presence of the coronary stenosis. Detection of Stress-Induced Ischemia Versus Infarction In standard practice, stress and rest myocardial perfusion images are compared to determine the presence, extent, and severity of stress-induced perfusion defects and to determine whether such defects reflect 2,5 regional myocardial ischemia or infarction. Stress-induced perfusion abnormalities in regions that exhibit normal perfusion at rest are termed reversible perfusion defects, and such regions represent viable tissue with blunted coronary blood flow reserve (Fig. Perfusion abnormalities at stress that are irreversible, or fixed, as seen on rest images (unchanged from stress to rest), most often represent infarction, particularly if the defect is severe (Fig. When both viable myocardium and scarred myocardium are present, 99m thallium redistribution or Tc tracer reversibility is incomplete, giving the appearance of partial 99m reversibility on the delayed thallium or rest Tc images.

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While deaths due to ruptured berry aneu- rysms or intracerebral hemorrhage are generally considered natural discount 20gm cleocin gel amex skin care used by celebrities, in cer- tain circumstances generic 20gm cleocin gel visa skin care lotion, they might be classified as homicide cleocin gel 20 gm low cost acne zapper. Thus buy cheap cleocin gel 20gm line skin care oils, if an individual ruptures an aneurysm during a fight in which physical violence is involved, the case should be classified as homicidal in manner. But, whether there are any criminal actions involved is something for the courts to decide, not the medical examiner. Primary Brain Tumors Sudden, unexpected death may, on rare occasion, be due to an undiagnosed primary brain tumor. In a study of l0,995 consecutive medicolegal autopsies in Dallas, Texas, DiMaio et al. Six deaths occurred following abrupt loss of consciousness or the individuals were found dead. Thirteen individuals had symptoms of increased intracranial pressure, epilepsy, and psychiatric manifestations. The symptoms also tended to be nonlocalizing and there was a lack of progression or change of symptoms in those patients in whom epilepsy was a primary manifestation of their underlying disease. There was also a lower incidence of focal neurological deficits as presenting symptoms. Mass inoculation of children with Hemophilus vaccine has resulted in the virtual disappearance of such cases. It is seen in association with infections of the ears and sinuses; alcoholism; splenec- tomy, pneumonia, and septicemia. The most common organisms now encoun- tered are Streptococcus pneumoniae (40–60%); Neisseria meningitis (15–25%); Listeria monocytogene (10–15%) and Haemophilus influenzae (5–10%). Hemophilus, pneumococcal, and meningococcal meningitis all may develop by direct extension from middle ear infections. The meninges appear cloudy on the ventral surface of the brain and, to a lesser degree, laterally due to purulent exudate (Figure 3. The exudate may be so slight as not to be seen grossly, or severe with copious quantities. In all cases of meningitis, the middle ears should be opened and examined to make sure that this is not the source of the meningitis. Men- ingococcal is now second only to pneumococcus in causing meningitis and is more common than Hemophilus influenza in both children and adults. Infection may present as a pure purulent meningitis, meningococcemia (septicemia), or as both. Meningococcemia may present as a mild febrile illness, a fulminant disease (Waterhouse-Friderichsen Syndrome) or a chronic illness. The patient may have chills, high fever, dizziness, nausea, headaches, or weakness. In 10% of the cases, there is a rapidly progressive course with toxemia, shock, and collapse. The individual may die less than 10 h after Deaths Due to Natural Disease 71 onset of symptoms. Occasionally, a person who is walking around will suddenly collapse, die, and, at autopsy, be found to have meningococcemia. In such a case, one can only speculate that the symptoms were not severe enough to inconvenience the person. At autopsy, there will be cyanosis; a blotchy erythematous rash, petechiae and purpura of the skin, and conjunctivae and acute bilateral hemorrhagic adrenal necrosis, but no meningitis (Figure 3. Cultures of the blood and spinal fluid for meningococcus are generally negative after refrigeration of the body due to the fragile nature of the organisms and/or antemortem administration of antibiotics. In such cases, diagnosis can be made from blood by detection of specific meningococcal capsular polysaccharides using immunoelectrophoresis, latex agglutination or polymerase chain reac- tion. The same clinical and autopsy presentation that occurs in meningococ- cemia may occur from pneumococcal septicemia. The latter condition is commonly associated with absence of the spleen, either through surgery or congenital aberration. The pneumococcus organisms can usually be cultured from the blood even after refrigeration of the body. Viral encephalitis is rarely seen in the medical examiner’s office due to its protracted course, which leads to a clinical diagnosis. The brain will show severe edema with perivascular cellular infiltrates and infiltration of the meninges. Reyes Syndrome Reyes syndrome is an entity of unknown etiology affecting children, in which an upper respiratory tract infection, chicken pox, and, rarely, gastroenteritis are followed by vomiting, convulsion, coma, hypoglycemia, elevated blood ammonia, and abnormal serum transaminase values. Individuals dying of the entity show fatty metamorphosis of the liver, with multiple small fatty cyto- plasmic vesicles in the hepatocytes, myocardial fibers, and tubular cells of the kidneys. These are extremely fine vesicles compared with the coarse deposit seen in alcoholic fatty metamorphosis of the liver. Reyes syndrome can be confused with inborn errors of metabolism with which it may share many of the same clinical characteristics. The only way to be absolutely sure of the diagnosis is to demonstrate specific mitochondrial changes in liver tissue. An increased incidence of this syndrome was noted in children who had taken aspirin for flu-like illnesses or chicken pox. Because of this, the use of aspirin in the treatment of children was discontinued in the 1980s. Thus, from 1980 to 1997, 1207 cases of Reyes Syndrome were reported with a peak incidence of 555 cases in 1980. Hydrocephalus Sudden and unexpected death is also seen in association with hydroceph- alus. Here, the patient will usually have a long history of hydrocephalus, often with a shunt procedure performed in the past. Such deaths are appar- ently a manifestation of the “final straw that broke the camel’s back. Psychiatric Patients Sudden death is occasionally seen in psychiatric patients, usually chronic schizophrenics on phenothiazine, in whom there are therapeutic or high, but not lethal, levels of this drug. Such deaths are believed to be due to one or more of the following: cardiac arrhythmias induced by this drug, which does have a recognized potential to produce arrhythmias; hyperthermia; hypoten- sion with development of tachycardia and cardiovascular collapse; respiratory dyskinesias; laryngeal-pharyngeal dystonias; neuroleptic malignant syn- drome; and seizures. This is to prevent deaths from other causes being incorrectly attributed to phenothiazines. Another subpopulation of schizophrenics whose deaths are not related to phenothiazine medication even though many have been prescribed this drug in the past, die suddenly and unexpectedly. A complete toxicological analysis using the most refined techniques will reveal no drugs in toxic levels and, in most cases, absence of any drugs at all. In some cases, histories have shown that the individuals have been off their medications for several months prior to death. Also included in this category were deaths allegedly due to inhalation of vomitus. It is now realized that vomitus in the tracheobronchial tree is almost invari- ably an agonal event. Epiglottitis While conditions like luetic or diphtheric laryngitis are no longer seen, occa- sional cases of acute epiglottitis will be seen in the medical examiner’s office.

Access is obtained at the umbilicus generic 20gm cleocin gel with visa acne questionnaire, either through a closed (Veress needle ) technique or open (Hasson trocar) technique cleocin gel 20gm for sale skin care for acne. The table will then be rotated to the left side discount cleocin gel 20gm fast delivery skin care pakistan, and the surgeon may ask for it to be placed in Trendelenburg or reverse Trendelenburg position generic cleocin gel 20gm mastercard skin care lines, depending on the location of the cecum. The appendix generally is placed in a bag prior to delivering it, or it may be brought directly through the 10/12-mm trocar. When unexpected pathology is identified, it can be dealt with by laparoscopy or by laparotomy, with incision placement dependent on findings. Bennett J, Boddy A, Rhode M: Choice of approach for appendicectomy: a meta- analysis of open versus laparoscopic appendicectomy. In patients with first-time unilateral hernias, there are no clear advantages in terms of operative time, postop pain, time to discharge, or time to return to normal activities, compared with tension-free open repair (see p. Two additional ports are placed in the midline—one suprapubic and one halfway between the umbilicus and the suprapubic port. Further dissection is required to identify the hernia defects, which are then reduced. A peritoneal flap over the hernia defect is created, and the preperitoneal space is entered. Laparoscopic repair of inguinal hernia is usually associated with less pain and earlier return to preop function when compared to the open procedure. Patients with strangulated or incarcerated hernias usually require emergent open procedures. Neumayer L, Giobbie-Hurder A, Jonasson O, et al: Open mesh versus laparoscopic mesh repair of inguinal hernia. According to the United States Centers for Disease Control and Prevention, 35% of American adults are obese. Surgical treatmentresults in weight loss of approximately 2/3–3/4 of excess body weight, usually with consequent correction ofcomorbidities. Operations for morbid obesity are classified as restrictive, such as the adjustable gastric banding and vertical banded gastroplasty; malabsorptive, such as a jejunoileal bypass; or a combination, such as the Roux-en-Y gastric bypass. In general, this operation is approached laparoscopically in most patients because of the decreased pain, earlier ambulation, earlier discharge from the hospital, quicker return to regular activity, and decreased wound complication rates,whencompared with an open approach. Open approaches, though very rare, are undertaken in patientswith previous upper abdominal surgery; patients who may not tolerate an increased intraabdominal pressure (e. Some surgeons prefer a split-leg table, with the surgeon standing between the legs. During this time, the patient is placed in a reverse Trendelenburg position to drop the small intestines into the pelvis. The omentum is placed in the upper abdomen, and the ligament of Treitz is identified. Some surgeons prefer aretrocolic approach, wherein a passage is made through the transverse mesocolon. Other surgeons prefer an antecolic approach, in which the omentum is divided to allow for a place where the Roux limb can pass without tension. Often a calibrating tube is placed after the first two staple firings to help maintain the size of the pouch and the anastomosis. Some surgeons hand sew the gastrojejunostomy, and some staple it with a linear stapler. Some surgeons staple the anastomosis and place the anvil of the end-to-end anastomotic stapler through the mouth (rarely done). Other surgeons place the anvil through a separate gastrotomy prior to complete division of the pouch. Usual preop diagnosis: Morbid obesity generally in combination with a medical condition(s) felt to be worsened by the obesity (e. Obesity and length of exposure to obesity, increase the risk of hospital admission and lengthen hospital stay. Evaluate any patient who has had previous bariatric surgery for metabolic changes that can include protein, vitamin, iron, and calcium deficiencies. Review a list of all current medications the patient is taking, including nonprescription appetite suppressors and diet drugs. For example, the combination of phentermine and fenfluramine (“phen-fen”), which is no longer prescribed in the United States, is associated with persistent, serious, heart and lung problems. Another weight loss medication, sibutramine, works in the brain by inhibiting the reuptake of norepinephrine, serotonin, and dopamine, producing a feeling of “anorexia,” which limits food intake. Orlistat blocks digestion and absorption of dietary fat by binding lipases in the gastrointestinal tract and can cause deficiencies in fat-soluble vitamins (A, D, E, K). A reduction in vitamin K levels can increase the anticoagulation effects of warfarin. The increase in adipose tissue seen in obese subjects increases volume of distribution of lipophilic anesthetic agents. However, drug distribution is dependent on cardiac output, which is strongly related to lean body mass. Tracheal intubation is necessary for controlled ventilation and airway protection. High Mallampati score and large neck circumference are the most reliable predictors of potential intubation difficulties. If a problem is anticipated preop, an “awake intubation” with a fiberoptic bronchoscope is recommended. Appropriate nerve blocks and topical anesthesia to the airway are applied, and sedative drugs are kept to a minimum. It is important that the patient breathes supplemental O2 during the intubation procedure. The patient must be placed with the head, upper body and shoulders significantly elevated (“stacked” or “ramped”) so that the ear is level with the sternum (head elevated laryngoscopy position, H. When a morbidly obese patient is in this position, the endoscopist’s view during direct laryngoscopy is significantly improved. Frappier J, Guenoun T, Journois D, et al: Airway management using the intubating laryngeal mask airway for the morbidly obese patient. Huerta S, DeShields S, Shpiner R, et al: Safety and efficacy of postoperative continuous positive airway pressure to prevent pulmonary complications after Roux-en-Y gastric bypass. Juvin P, Vadam C, Malek L, et al: Postoperative recovery after desflurane, propofol, or isoflurane anesthesia among morbidly obese patients: a prospective, randomized study. Perilli V, Sollazzi L, Bozza P, et al: The effects of the reverse Trendelenburg position on respiratory mechanics and blood gases in morbidly obese patients during bariatric surgery. Warn patients about possible fetal loss (3–12% in 1st trimester) and premature labor (5–8% in 2nd and 25–40% in 3rd trimesters). Anesthesia and surgery are associated with increased spontaneous abortion, growth retardation, and perinatal mortality; however, no increase in congenital abnormalities has been found. Rates of fetal loss, premature labor, and maternal mortality are higher among sicker patients. It is unclear whether adverse outcomes after surgery relate to the disease process itself, disturbances in nutrition, the surgical procedure, exposure to radiation, or drugs. No correlation has been found between outcome and any specific anesthetic technique or agent (including N2O).

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Implant-related complications are similar to those seen with standard pacemakers and defibrillators buy cleocin gel 20gm low cost acne medication accutane, with the additional risk of dissection or perforation of the coronary sinus cleocin gel 20gm free shipping acne studios. Sudden Cardiac Death in Heart Failure Patients with heart failure and left ventricular systolic dysfunction are at increased risk for sudden cardiac 25-27 death (see also Chapter 42) safe cleocin gel 20gm acne 415 blue light therapy 38 led bulb. Importantly order cleocin gel 20gm line acne pictures, this trial included no arrhythmic markers, such as nonsustained or inducible ventricular tachycardia, for inclusion. This observation may be important when considering the timing of device placement in eligible patients. Also, clouding the picture were older observations suggesting that the prophylactic administration of an antiarrhythmic agent, amiodarone, might prolong survival in nonischemic cardiomyopathy patients. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. Kaplan-Meier estimates for A, all-cause mortality; B, cardiovascular mortality; and C, sudden cardiac death. The activity level may serve as a useful teaching and reinforcement tool for both patient and family about the importance and level of activity. Implantable devices can monitor fluid status by assessing changes in intrathoracic impedance. These devices allow continuous or intermittent assessment of hemodynamics, generally focused on the assessment of intracardiac or pulmonary artery pressures. The majority of pressure-based medication changes (≈75%) involved, as expected, diuretics and long-acting nitrates. Wireless pulmonary artery haemodynamic monitoring in chronic heart failure: a randomised controlled trial. Conclusion Cardiac resynchronization therapy offers a therapeutic approach for treating patients with ventricular dyssynchrony and heart failure. Guidelines Cardiac Resynchronization and Implantable Cardioverter-Defibrillators in Heart Failure with a Reduced Ejection Fraction William T. Patients who have had sustained ventricular tachycardia, ventricular fibrillation, unexplained syncope, or cardiac arrest are at highest risk for recurrence. Developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. Cardiac resynchronization therapy is important for all patients with congestive heart failure and ventricular dysynchrony. Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay. Comparative effects of permanent biventricular and right- univentricular pacing in heart failure patients with chronic atrial fibrillation. Double-blind, randomized controlled trial of cardiac resynchronization in chronic heart failure. Safety and efficacy of combined cardiac resynchronization therapy and implantable cardioversion defibrillation in patients with advanced chronic heart failure. Cardiac resynchronization therapy for the treatment of heart failure in patients with intraventricular conduction delay and malignant ventricular tachyarrhythmias. The effect of cardiac resynchronization on morbidity and mortality in heart failure. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure. Effects of cardiac resynchronization on disease progression in patients with left ventricular systolic dysfunction, an indication for an implantable cardioverter defibrillator, and mildly symptomatic chronic heart failure. Randomized trial of cardiac resynchronization in mildly symptomatic heart failure patients and in asymptomatic patients with left ventricular dysfunction and previous heart failure symptoms. Risk stratification of ventricular arrhythmias in patients with systolic heart failure. Left ventricular ejection fraction for the risk stratification of sudden cardiac death: friend or foe? Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. Prophylactic defibrillator implantation in patients with nonischemic dilated cardiomyopathy. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. Implantable cardioverter-defibrillator for non ischemic cardiomyopathy: an updated meta-analysis. Intrathoracic impedance monitoring in patients with heart failure: correlation with fluid status and feasibility of early warning preceding hospitalization. Intrathoracic impedance monitoring, audible patient alerts, and outcome in patients with heart failure. Continuous ambulatory right heart pressure measurements with an implantable hemodynamic monitor: a multicenter 12-month follow-up study of patients with chronic heart failure. Ongoing right ventricular hemodynamics in heart failure: clinical value of measurements derived from an implantable monitoring system. Physician-directed patient self-management of left atrial pressure in advanced chronic heart failure. Wireless pulmonary artery haemodynamic monitoring in chronic heart failure: a randomised controlled trial. Wireless pulmonary artery pressure monitoring guides management to reduce decompensation in heart failure with preserved ejection fraction. Indeed, despite the variety of available medical therapies and electrophysiologic interventions, such as placement of biventricular pacemakers and implantable cardioverter-defibrillators (see Chapter 27), many patients who have been so treated are still left with a reduced quality of life and a poor prognosis. The medical management of patients with a reduced ejection fraction is discussed in Chapter 25 and the role of circulatory assist devices in Chapter 29. The term ischemic cardiomyopathy is used to describe the myocardial dysfunction that arises secondary to occlusive or obstructive coronary artery disease (see Chapter 61). Ischemic cardiomyopathy is composed of three interrelated pathophysiologic processes that may overlap: myocardial hibernation, defined as persistent contractile dysfunction at rest, caused by reduced coronary blood flow that can be partially or completely restored to normal by myocardial revascularization; myocardial stunning, wherein the viable myocardium may demonstrate prolonged but reversible postischemic contractile dysfunction caused by the generation of oxygen-derived free radicals on reperfusion and by a loss of sensitivity of contractile filaments to calcium; and irreversible myocyte cell death, leading to ventricular remodeling and contractile dysfunction. Other major technical issues to be considered are the adequacy of target vessels for revascularization and an adequate conduit strategy. The most important determinant remains the extent of jeopardized but still- viable myocardium (see Chapters 14, 16, and 17). The impact of viability on decision making for revascularization is discussed separately in Chapter 16. Studies show that for patients with clinical heart failure, perioperative mortality rates range from approximately 2. A mismatch of more than 18% was associated with a sensitivity of 76% and a specificity of 78% for predicting a change in functional status after revascularization. A substantial objective improvement in physical activity was noted in patients with presurgical mismatches that occupied at least 20% of the ventricular myocardium. Thus, patients with large perfusion-metabolism mismatch exhibited the greatest clinical benefit after revascularization. Viability studies may be appropriate for patients with severe disease and adequate surgical targets. However, patients who have valvular dysfunction secondary to, or in association with, a primary cardiomyopathy pose a much more difficult management problem.

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