Cardiology clinics
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Cardiac diseases, particularly coronary artery disease and its risk factors, are associated with the majority of perioperative complications in patients undergoing major noncardiac surgery. Risks are remarkably low overall, yet for selected patients undergoing high-risk procedures, the chances of complications remain reasonably high. The literature has focused largely on identifying patients in whom complications are most likely to occur, using clinical assessment, including RFI, specialized cardiac testing, and perioperative monitoring. ⋯ The general application of percutaneous or surgical revascularization as a means of reducing perioperative risk has not been assessed and to date represents an expensive and perhaps risky strategy. In patients who satisfy the usual symptomatic or prognostic criteria for coronary revascularization, its timing should depend on the urgency and risk of the noncardiac procedure. Finally, patients with cardiac devices--pacemakers, prosthetic valves, implantable debrillators, and antitachycardia devices--and survivors of congenital and transplant surgery have specific needs that require careful attention, going beyond the usual vigilance required in the perioperative period.
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Review
Intraoperative assessment of left ventricular function with transesophageal echocardiography.
Qualitative TEE assessment is used to guide administration of fluids and inotropic drugs and to monitor left ventricular function intraoperatively. Left ventricular hypovolemia or depression is easily recognized by directly noting a small end-diastolic area or low ejection fraction. Appropriate therapy can be instituted and continuously monitored. ⋯ The raw information in the returning signal will most likely be further analyzed to allow characterization of ischemic but still viable tissue. Coupled with the ability to assess regional myocardial perfusion by contrast echocardiography, the clinician will be able to institute more timely and appropriate medical and surgical therapy. TEE assessment of mitral valve function has become the standard of care after mitral valve repair, and in a similar fashion, assessment of myocardial perfusion by TEE may become the standard of care during cardiac and major noncardiac surgery.
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The transesophageal approach has improved echocardiographic investigation of cardiac structure and function. As a new window to the heart with markedly improved resolution, TEE gives better insight into cardiac morphology and pathology than does precordial imaging. Specifically, the LA and mitral valve can be better visualized due to the immediate retrocardiac position of the imaging transducer. ⋯ Furthermore, pulmonary venous flow is characteristically altered in patients with severe MR and can be useful in grading its severity. Transesophageal continuous wave Doppler echocardiography may prove useful to estimate systolic pulmonary artery pressure as another clinically useful hemodynamic parameter. Therefore, TEE adds significantly to the noninvasive assessment of cardiac hemodynamics.
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The combination of different ultrasound techniques such as transthoracic, suprasternal, subcostal, and TEE has a high sensitivity and specificity in the diagnosis of aortic dissection. Limitations of this combined ultrasound technique are related to the visualization of the ascending part of the aortic arch, which, because of the interposition of the trachea, cannot be visualized completely. The beginning or end of a dissection in this part of the aorta may be misinterpreted. ⋯ With TEE, entry tears can be detected with a higher sensitivity than with MR tomography. This capability may be important for the patient's prognosis. MR tomography, on the other hand, has a better spatial resolution showing the entire aorta, particularly the ascending aortic arch.
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Two primitive pacemakers were invented between 1925 and 1932, demonstrating that adequate knowledge existed to pace the heart for brief periods. Heart specialists ignored these interesting inventions. In contrast, Zoll's announcement of external pacing in 1952 spurred intense interest and an outpouring of research. The reasons for the different response of heart specialists in the 1950s have to do with improved medical understanding of cardiac arrhythmias, growing confidence that cardiac resuscitation was possible, and the expansion of hospital-based medicine after World War II.