Sick Sinus Syndrome

The following signs and symptoms are seen in sick sinus syndrome:

• General appearance: Patients will often times appear fatigued due to brain and muscle hypoperfusion.
• Chest and heart: Chest pain may be occasionally felt due to cardiac hypoperfusion. Difficulty in breathing may be due to generalized hypoxemia.
• Abdomen: Distention due to ascites in congestive heart failure complications.
• Extremities: Slower peripheral pulses with bradycardia.
• Neurologic: Patients will complain of dizziness, confusion and near syncope due to hypotension.

Patients may be initially examined physically when they present in the emergency room, they would most likely reveal irregular pulse rate and low blood pressure. Auscultation findings of slow rhythm and skip beats may be suggestive of a dysfunctional node. The succeeding tests for diagnosis may be implored in patients with high suspicion of sick sinus syndrome:

• Electrocardiogram (ECG): Sick sinus syndrome may convey a characteristic pattern on ECG. Findings of bradyarrhythmias with heart rates less than 46-51 beats per minute may suggestive of a nodal pathology [8]. 
• Holter monitor: This is a portable device that monitors the heart rhythm in a 24-48 hours period. It allows the cardiologist to detect heart rhythm abnormalities in an extended period of time. Sinus pauses of more than 3 seconds except in rare conditions like seizure disorders and sleep apnea syndrome is suggestive of a nodal pause or arrest [9].
• Event recorder: This is also a portable device that may monitor the heart’s electrical activity at the time of an event with just a push of a button.
• Implantable loop recorder: This small implantable device may is placed under the skin of the chest to monitor cardiac electrical activities from months to years. Rhythms may be recorded automatically when an event occurs or with a press of a button every time the patients feel some discomforts. 

The main goal in the treatment of sick sinus syndrome focuses on the control of the patient’s discomfort. Nodal dysfunction may present mildly or asymptomatic, and may no longer require treatment. Patients on current hypertensive medications like beta-blockers and calcium channel blockers may need some revisions to control the symptoms.

Some patients with sick sinus syndrome may require a permanent pacing device called pacemakers which are implanted beneath the chest wall skin. Anti-arrhythmics may be given to patients with pacemaker whom rhythm remain abnormal. The regular intake of warfarin in face of arrhythmia in nodal dysfunction can prevent strokes in the future.

AV node ablation using radiofrequency probes to control irregularly fast rhythms can subdue tachyarrhythmia in sick sinus syndrome. However, nodal ablation may have a recurrence of abnormal pacing and may revert to atrial fibrillation as long term complication in a number of cases [10].

Sick sinus syndrome may rarely lead to sudden cardiac death [4]. Patients usually succumbs with their underlying cardiac disease rather than with the nodal dysfunction. The use of a cardiac pacemaker is primarily to alleviate symptoms and does not affect the overall mortality rating of the cardiac patients [5]. Patient with nodal dysfunction but with normal systemic ventricular function carry a very good prognosis. Among the sick sinus syndrome subtypes, the bradycardia-tachycardia syndrome has a guarded prognosis compared to the others.

Complications

The following sick sinus syndrome complications can lead to significant morbidity and mortality among cardiac patients:

• Near syncope or syncope
• Falls
• Sudden cardiac death
• Cerebrovascular disease (stroke)
• Congestive heart hailure [6]
• Intolerance to slight exercises
• Cardiac dysrhythmias
• Atrial flutter and fibrillation [7]

The sinus node is the natural pacemaker of the heart that produces the electric impulses that initiates each heartbeat. These impulses traverse from the atria to the ventricles and contract the cardiac muscles to force out the blood. A sick sinus may insinuate a slow rhythm (bradycardia) or a very fast rhythm (tachycardia) that causes characteristic symptoms of the disease.

The following are the different types of sick sinus syndrome and their probable causes:

• Sinus arrest: This is due to the halting of the sinus activity.
• Sinoatrial block: Electrical impulses are described to move slowly through the sinus node causing a slow heart rate.
• Bradycardia-Tachycardia syndrome: There is an alternate fast and slow pace rhythms with a long pause between heartbeats.

There are no available data on the exact incidence of sick sinus syndrome worldwide. The incidence of sick sinus syndrome is 1 out of 600 cardiac patients beyond 65 years of age [2]. Because sick sinus syndrome correlates well with old age, this syndrome is more prevalent in countries with high life expectancy. The age related occurrence of sick sinus syndrome has an average of 68 years old although it may occur in all ages [3]. The prevalence of sick sinus syndrome among the younger age group is usually associated with an underlying heart condition.

The basic pathophysiology of sick sinus syndrome falls on the propagation of electrical impulses. Sometimes, the conduction path at the atrium is obscured by injury causing a delay in the conduction to the heart muscles. The ventricular contraction rate is consequently slowed down and may present with long pauses in between impulses, rest or stressful activities. Mild cases of sick sinus syndrome may be asymptomatic. Presentation of signs and symptoms occurs with concomitant organ hypoperfusion or irregular pulses.

By keeping one’s heart healthy by eating a balanced diet and by doing regular exercises, one may prevent the occurrence of sick sinus syndrome and other heart diseases. One must avoid taking unprescribed medications to avoid any adverse reactions that can cause arrhythmias in the future. These are good advices but majority of sick sinus cases are not preventable.

Sick sinus syndrome is a clinical disease characterized by the persistent dysfunction of the sinus node in the heart. Sick sinus syndrome is sometimes referred to as sinus node disease or sinus node dysfunction in medical literatures. The sinus node is defined as the specialized group of cells located in the right upper chamber of the cardiac musculature.

This node generates electrical impulses throughout the heart in a steady pace of regular electrical discharges. In sick sinus syndrome, these electrical impulses are abnormally paced whether too fast or too slow. Sick sinus syndrome is a relatively rare disease that occurs more often in older people that may eventually require a pacemaker to restore the heart’s normal rhythm [1].

Definition

Sick sinus syndrome refers to the persistent dysfunction of AV node in the heart causing abnormal heart rhythms.

Cause

Sinus arrest, Sino-atrial block and tachy-brady arrhythmias are possible causes of the condition.

Symptoms

Chest pain, confusion, fatigue, dypnea and abnormal pulses may occur.

Diagnosis

Clinical examination, electrocardiogram (ECG) and Holter monitor may be needed to diagnose sick sinus syndrome.

Treatment and follow-up

Anti-arrhythmic drugs, anticoagulants, pacemaker insertion and AV node ablation using radio frequency are treatment options.

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