Final answer:
Calcium channel blockers help relieve angina pain by relaxing peripheral arterioles to reduce afterload, thus decreasing the heart's workload and the myocardial oxygen demand. Therefore, the correct option is A.
Step-by-step explanation:
A patient is taking a calcium channel blocker (CCB) for stable angina. The correct answer to the question of how calcium channel blockers relieve pain is option (a) help relax peripheral arterioles to reduce afterload. This action decreases the resistance the heart has to work against to eject blood during systole, thereby reducing the myocardial oxygen demand. Unlike option (c), calcium channel blockers do not increase heart rate to improve myocardial contractility; in fact, some CCBs can have a negative effect on the heart rate. Option (d) is also incorrect as calcium channel blockers do not specifically aim to increase the QT interval, which pertains more to the electrical conduction and repolarization of the heart rather than anginal pain relief.