A significant reduction in coronary flow reserve is present when the ratio of flow at rest to flow after vasodilation is less than 2 : 1. Measurement of the pressure gradient across a stenosis using a small wire transducer also can assess functional severity. Fractional flow reserve is the ratio of the distal pressure to proximal pressure after maximum vasodilation. A fractional flow reserve of less than 0.75 indicates a significant stenosis.
[...] Right-Sided Heart Catheterization The most commonly used catheter is a balloon flotation catheter that is introduced into the femoral, brachial, subclavian, or internal jugular vein, then passed with or without fluoroscopic guidance into the right atrium, right ventricle, and pulmonary artery. If necessary, hemodynamic measurement of oxygen saturations can be obtained as the catheter is passed into the pulmonary artery. When in the pulmonary artery, inflation of the balloon at the tip of the catheter occludes the smaller pulmonary arteries and allows for measurement of the pulmonary capillary wedge pressure, which is nearly always an accurate reflection of left atrial pressure. [...]
[...] Capsulas CATHETERIZATION AND ANGIOGRAPHY Cardiac catheterization and angiography provide the detailed assessment of anatomy and physiology of the heart and vasculature and are the gold standard for assessment of cardiac disease. The technique first was applied to humans by Forssmann in 1929, but it was expanded into a diagnostic tool by Cournard and Richards; in 1956, all three physicians shared the Nobel Prize for their discovery. Selective coronary angiography was introduced by Sones in 1963 and modified further by Judkins. [...]
[...] Contraindications and Risks The risks of cardiac catheterization and coronary angiography are low, with a risk of myocardial infarction risk of stroke, and a reported mortality of These risks are increased substantially, however, in certain subsets of patients, such as patients undergoing an emergency procedure, patients having an acute myocardial infarction, and patients who are hemodynamically unstable. In patients who require catheterization as a prelude to a potentially life-saving intervention, there are no absolute contraindications, but relative contraindications include acute renal failure, pulmonary edema, bacteremia, acute stroke, active gastrointestinal bleeding, and documented anaphylactic reaction to contrast dye. [...]
[...] Occasionally, left-sided heart catheterization can be accomplished by a needle-tipped catheter that punctures the atrial septum from the right atrial side to enter the left atrium; the needle is withdrawn, and the catheter is advanced to the left ventricle. This technique is reserved for situations in which the left ventricle cannot be accessed by the retrograde approach, such as in patients who have aortic valve prostheses, or when mitral valvuloplasty or invasive electrophysiology studies are being done. Hemodynamic Assessment PRESSURE MEASUREMENTS The measurement of intracardiac pressure is an essential component of cardiac catheterization and is performed through fluid-filled catheters that are attached to an external pressure transducer. [...]
[...] The shunt ratio (pulmonary blood flow-to-systemic blood flow) measures the severity of a shunt; for an atrial or ventricular septal defect, a shunt ratio of greater than 1.5 : 1 is considered significant. Cardiac Angiography Angiography almost always is performed during cardiac catheterization by injecting an iodine-containing radiopaque contrast agent. These agents are highly viscous and can cause cardiac arrhythmias and adverse hemodynamic changes secondary to ionic changes, volume expansion, and negative inotropic effects. Use of more expensive, low osmolar, nonionic agents reduces these adverse effects. [...]
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