Stands for transmyocardial laser revascularization, a procedure by which a physician uses a laser to make holes in the heart to relieve the pain of severe angina.
TMR has been done from both the outside and inside of the heart. When done from the outside, a laser (carbon dioxide or holmium laser) is placed in proximity to the left ventricle of the heart and sufficient energy is applied to create small channels from the outside (epicardial) surface to the inside (endocardial) surface of the heart. Thus, a number (10-50) of tiny holes are created right through the heart muscle (the myocardium). More recently, this procedure has moved into the cardiac catheterization lab and the laser works from the inside outward.
Angina is due to oxygen deprivation of the heart muscle. The channels made by the laser are intended to improve the perfusion of the oxygen-deprived heart muscle by giving it direct access to the oxygen-rich blood from the left ventricle. This does not happen for long, because the channels quickly fill with blood clot. Further, the procedure does not noticeably improve the function of the heart. Nonetheless, TMR appears to lessen or abolish the pain in patients with severe angina, at least for a while.
This procedure was originally done by heart surgery and carried an overall mortality rate of about 5 percent. The major hazards are arrhythmias (abnormal hear rhythms) and tamponade due to complete penetration of the heart. Tamponade is a life-threatening situation in which there is such a large amount of blood inside the pericardial sac around the heart that it interferes with the performance of the heart.
One-year data from three major randomized trials reported late in 1999 showed that transmyocardial revascularization (TMR), either by the open chest method or percutaneously, was superior in terms of angina relief and improvement in exercise tolerance to maximal medical therapy.
Transcranial magnetic stimulation.
- Toasted skin syndrome
McGraw-Hill Professional, 2008.
A South American herb (Nicotiana tabacum) whose leaves contain 2 to 8 percent nicotine and serve as the source of both smoking and smokeless tobacco and the basis of great health hazards.
- Tobacco smoking
The direct inhalation of tobacco smoke, the basis of major health hazards. Long known to cause cancer in humans, tobacco smoking is generally held to be the leading preventable cause of cancer in developed countries. Tobacco smoking was formally classified as a “known human carcinogen” by the US government in 2000.
- Toc- (prefix)
Stemming from the Greek word “tokos” meaning childbirth, we have toc-, toco-, tok-, and toko- as combining forms, all referring to labor or childbirth.