They work by blocking voltage-sensitve calcium channels in the heart and in the blood vessels. This prevents calcium levels from increasing as much in the cells when stimulated, leading to less contraction.
This decreases total peripheral resistance[?] by dilating the blood vessels, and decreases cardiac output by lowering the force of contraction. Because resistance and output drop, so does blood pressure.
With low blood pressure, the heart does not have to work as hard, this can ease problems with cardiac myopathy[?] and coronary disease.
Unlike with beta-blockers, the heart is still responsive to sympathetic nervous system stimulation, so blood pressure can be maintained more effectively.
wikipedia.org dumped 2003-03-17 with terodump