The patient is experiencing Prinzmetal angina, also referred to as vasospastic angina or variant angina. It is mainly caused by coronary arterial spasms. This type of angina is not directly associated with cardiac workload or physical stress. Unstable angina is a severe type of angina that occurs at rest and lasts for increasing periods of time, while stable angina is a predictable type of angina that primarily occurs during stressful periods and is relieved with relaxation and rest. There is no such thing as silent angina.