Afterload

As afterload (English afterload ) are those forces referred to counteract the contraction of the muscles of the ventricles and thus limit the ejection of blood from the ventricles into the blood vessel system. It reaches its maximum shortly after the opening of the aortic valve. The afterload is mainly determined by two factors: the arterial blood pressure and the stiffness (compliance) of the arteries.

The wall tension of the heart chambers and thus the afterload is not directly measurable. Reliability can be derived ( in the aorta pressure, divided by the flow of blood at a given time ) from the impedance of the aorta. The impedance can, however, only invasively measured approximately by the transesophageal echocardiography. Clinically, the afterload can also estimate the arterial blood pressure, aortic stenosis, or as long as no significant change in arterial stiffness is present.

The afterload is pharmacologically influenced and can be lowered, for example, through the use of arterial vasodilators ( e.g., calcium antagonist of the dihydropyridine type ) or by beta-blockers. ACE inhibitors, diuretics, and nitroglycerin reduce the preload and the afterload.