What symptom is commonly associated with the use of Diltiazem in managing cardiomyopathy?

Diltiazem is a calcium channel blocker that is frequently used in the management of various cardiovascular conditions, including cardiomyopathy. One of the known side effects of this medication is bradycardia, which refers to a slower than normal heart rate. This occurrence happens because Diltiazem decreases the rate at which electrical impulses are conducted through the heart, particularly affecting the sinoatrial and atrioventricular nodes.

In the context of managing cardiomyopathy, where heart function can be compromised, Diltiazem's ability to lower heart rate allows for better diastolic filling and can aid in reducing the workload of the heart. While bradycardia can sometimes lead to symptoms such as dizziness or fatigue, it is particularly significant in patients with underlying heart conditions, where maintaining an appropriate heart rate is critical for optimal cardiac output.

The other symptoms listed, such as anxiety, rash, and headache, while they may occur with various medications, are not typically associated with the pharmacological effects of Diltiazem in managing cardiomyopathy. This specificity of bradycardia as a common side effect makes it the most relevant answer in this scenario.