Calcium as an ion involve in regulation of vascular and cardiac contraction, verapamil which is a Calcium channel blocker (CCB) effect the heart by causing negative ionotropic effect which is dangerous in people with CHF because of the necessity of calcium for proper cardiac functioning. Verapamil effect the blood vessels by causing vasodilation which is the desired effect in controlling high BP.
verapamil calcium channel blockers, should generally be avoided in patients with CHF, as their negative inotropic effects may exacerbate the disease.
That is very true brother
Verapamil as said by Mr.Eloy Mwanjisi is a Calcium Channel Blocker, these drugs tend to have weakening effect on the heart muscles because they block the entry of calcium ions into the muscle cells via calcium channels as their names imply, calcium is important in contractility of heart muscles and a patient with CHF generally have a weak heart, administering drugs like Verapamil may worsen the condition because of reduced contractility. Good contractility is necessary for ensuring perfusion of blood to different parts of the body
Note that the extent of this effect vary from drug to drug of the same class(CCB) for example diltiazem have more of chronotropic and dromotropic effect than inotropic effects.