Patients experiencing angina when doing certain physical activities can often prevent symptoms by taking nitroglycerin 5 to 10 minutes before the activity. Overdoses may generate methemoglobinemia.Nitroglycerin is available in tablets, ointment, solution for intravenous use, transdermal patches, or sprays administered sublingually. Some forms of nitroglycerin last much longer in the body than others. Nitroglycerin as well as the onset and duration of action of each form is different. The sublingual or tablet spray of nitroglycerin has a two minute onset and twenty five minute duration of action. The oral formulation of nitroglycerin has a thirty five minute onset and a duration of action of 4-8 hours. The transdermal patch has an onset of thirty minutes and a duration of action of ten to twelve hours. Continuous exposure to nitrates has been shown to cause the body to stop responding normally to this medicine. Experts recommend that the patches be removed at night, allowing the body a few hours to restore its responsiveness to nitrates. Shorter-acting preparations of nitroglycerin can be used several times a day with less risk of developing tolerance. Nitroglycerin was first used by William Murrell to treat angina attacks in 1878, with the discovery published that same year. Industrial exposure
Infrequent exposure to high doses of nitroglycerin can cause severe headaches known as "NG head" or "bang head". These headaches can be severe enough to incapacitate some people; however, humans develop a tolerance to and dependence on nitroglycerin after long-term exposure. Although rare, withdrawal can be fatal.
LHC can be synonymous with coronary angiography.technique is also used to assess the amount of occlusion (or blockage) in a coronary artery, often described as a percentage of occlusion. A thin, flexible wire is inserted into either the femoral artery or the radial artery and threaded toward the heart until it is in the ascending aorta. Radial access is not associated with an increased risk of stroke over femoral access. At this point, a catheter is guided over the wire into the ascending aorta, where it can be maneuvered into the coronary arteries through the coronary ostia. In this position, the interventional cardiologist can inject contrast and visualize the flow through the vessel. If necessary, the physician can utilize percutaneous coronary intervention techniques, including the use of a stent (either bare-metal or drug-eluting) to open the blocked vessel and restore appropriate blood flow. In general, occlusions greater than 70% of the width of the vessel lumen are thought to require intervention. However, in cases where multiple vessels are blocked (so-called "three-vessel disease"), the interventional cardiologist may opt instead to refer the patient to a cardiothoracic surgeon for coronary artery bypass graft (CABG; see Coronary artery bypass surgery) surgery. Right heart catheterization
Right heart catheterization (RHC) allows the physician to determine the pressures within the heart (intracardiac pressures). The heart is most often accessed via the internal jugular or femoral vein; arteries are not used. Values are commonly obtained for the right atrium, right ventricle, pulmonary artery, and pulmonary capillary "wedge" pressures.