What is the primary action of Diltiazem on heart muscle cells?

Diltiazem primarily acts by inhibiting calcium ion influx into heart muscle cells. It is a calcium channel blocker that targets L-type calcium channels primarily found in cardiac and smooth muscle tissues. By blocking these channels, Diltiazem reduces the entry of calcium ions into the cells during depolarization. This decrease in calcium availability leads to reduced contractility and heart rate, which can help manage conditions such as hypertension and certain types of angina.

Calcium ions play a crucial role in the excitation-contraction coupling of cardiac muscle, as they are necessary for the contraction of muscle fibers. By inhibiting calcium influx, Diltiazem decreases the strength of heart muscle contractions and slows down the conduction through the heart, especially at the AV node. This mechanism is beneficial in reducing the workload on the heart and controlling heart rhythms, making Diltiazem effective in treating various cardiovascular conditions.