Sick sinus syndrome is a syndrome that describes a group of arythmia characterized by a failure of the sinus node, the part of the heart that sets the steady pace described as sinus rhythm. It's underlying causes are unknown, but it tends to occur in the elderly. It can also appear in persons who have had heart surgery, and often appears together with other issues of the heart, such as coronary artery disease, high blood pressure, and heart valve disorders. It can also appear in any patient who is suffering from another disease that affects the structure of the heart, such as sarcoidosis and amyloidosis

The syndrome is difficult to diagnose as they changes in heart rhythm often do not appear in a patient at rest, and patients are generally not well enough to undergo a cardiac stress test. It generally has to be diagnosed by monitoring the patient's EKG while they go about normal activities such as walking. The syndrome can cause both bradycardia and tachycardia.

Several drugs are known to make the syndrome worse, such as digitalis, calcium channel blockers, beta blockers and even drugs that are commonly used to treat arythmia.

Treatment generally starts with a pacemaker, followed by drugs that treat the specific type of arythmia. Treatment with drugs alone is contra-indicated as drug therapy alone can result in the exact opposite disorder - for example anti-bradycardia drugs can result in tachycardia in an SSS patient, and vice versa.

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