In some patients with heart disease, the contraction becomes what is known as ‘dyssynchronous’. This means that different parts of the heart move at different times, which impairs the efficiency of the heart, and can worsen symptoms of heart failure. There are many causes. This problem can be easily diagnosed using an ECG.
CRT refers to a type of pacemaker, which may or may not be combined with an ICD depending on the circumstances. Studies have demonstrated that in these cases, CRT improves symptoms and prolongs life expectancy in the majority of patients. The procedure itself is similar to that described in the pacemaker section, although an additional third lead is used.