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At low doses, nitroglycerin dilates veins more than arteries, thereby reducing preload (volume of blood in the heart after filling); this is thought to be its primary mechanism of action. By decreasing preload, the heart has less blood to pump, which decreases oxygen requirement since the heart does not have to work as hard.
Lower preload and afterload result in the heart needing less energy and thus less oxygen. Besides, NO donated by nitrovasodilators can reduce coronary spasms, increasing the heart's oxygen supply. [2] PDE5 inhibitors block deactivation of cGMP by the enzyme phosphodiesterase-5. In combination with the increased cGMP production caused by ...
Sodium nitroprusside (SNP), sold under the brand name Nitropress among others, is a medication used to lower blood pressure. [3] This may be done if the blood pressure is very high and resulting in symptoms, in certain types of heart failure, and during surgery to decrease bleeding. [3]
This vasodilation does not decrease the volume of blood the heart pumps, but rather it decreases the force the heart muscle must exert to pump the same volume of blood. Nitroglycerin pills, taken sublingually (under the tongue), are used to prevent or treat acute chest pain.
Preload is related to the ventricular end-diastolic volume; a higher end-diastolic volume implies a higher preload. However, the relationship is not simple because of the restriction of the term preload to single myocytes. Preload can still be approximated by the inexpensive echocardiographic measurement end-diastolic volume or EDV.
Initial lengths larger or smaller than this optimal value will decrease the force the muscle can achieve. For longer sarcomere lengths, this is the result of there being less overlap of the thin and thick filaments; [ 8 ] [ 9 ] [ 10 ] for shorter sarcomere lengths, the cause is the decreased sensitivity for calcium by the myofilaments .
The U.S. Department of Transportation said the Federal Highway Administration has "terminated approval" of New York City's congestion pricing plan, the first of its kind in the nation, which went ...
The term "amyl nitrite" encompasses several isomers.In older literature, the common non-systematic name amyl was often used for the pentyl group, where the amyl group is a linear or normal (n) alkyl group, and the resulting amyl nitrite would have the structural formula CH 3 (CH 2) 3 CH 2 ONO, also referred to as n-amyl nitrite.