Sinus Arrhythmia

One of the most common arrhythmias is a sinus arrhythmia. It involves cyclic changes in the heart rate during breathing. It is very common in children and often found in young adults. Patients with sinus arrhythmia do not experience any cardiovascular symptoms.

The sinus node rate can change with inspiration/expiration, especially in younger people. The heart rate speeds up with inspiration (since it inhibits your vagal nerve) and decreases with expiration (stimulates your vagal nerve).

Calculate your heart rate when your rhythm is regular:

  • There are 300 large squares per minute
  • If your rhythm is regular, count the number of large squares between two QRS complexes and divide it into 300:

Heart Rate

Sinus Arrhythmia

Sinus arrhythmia, if not in a young person and not occurring with repsiration, may be a sign of sick sinus syndrome (SSS). Sick sinus syndrome occurs when over time the sinus node scars and becomes replaced with fibrous tissues. SSS contains a spectrum of arrhythmias including severe sinus bradycardia, tachycardic-bradycardic syndrome (tachy-brady syndrome), or sinus exit block/sinus pauses.

Also known as “tachy-brady syndrome,” sick sinus syndrome is a common condition that affects the elderly, accounting for the majority of patients undergoing pacemaker implantation in the U.S.  It is frequently associated with atrial fibrillation or atrial flutter.

In brief, it is due to the inability of the heart to maintain and regulate a steady and normal heartbeat. It either goes too fast (during atrial fibrillation or flutter) or too slow (after conversion to normal rhythm), and rarely just right.  The heart can sudden stop for up to 6 seconds, as in the case below:

SSS

What are symptoms of sick sinus syndrome?

Symptoms of SSS are caused by the frequent alternation of rapid and slow heart beat, resulting in palpitation (pounding heart beat), fainting, fatigue, and shortness of breath.

What causes sick sinus syndrome?

Everything that causes atrial fibrillation and atrial flutter can cause sick sinus syndrome. Age is the number one risk factor for developing SSS. It is frequently exacerbated by the use of medications (i.e., digoxin, beta blocker, calcium channel blocker).  The main purpose of these medications is slow down the fast heartbeat in this syndrome, but the often inevitable trade-off is excessive slowing of the heart rate to the point of needing pacemaker.

Consequences of sick sinus syndrome.

The main feature of this syndrome is inability to maintain normal stable heart rate. The resultant symptoms can include palpitation, shortness of breath, easy fatigue, and fainting spells.

Treatment options.

In patients with predominantly a slow heart rate problem, pacemaker is the treatment option of choice.  There are no reasonable medical alternatives as no medications can speed up the heartbeat effectively and safely on a long term basis.  For those with both fast and slow heart rate problem, medications used to control the rapid heartbeat in this syndrome often slow the heart rate to the point  of requiring a pacemaker.  This is the classic “rock and hard place” scenario where if left untreated, the rapid heart rate can potentially lead to other serious consequences.  Very frequently, patients end up with a combination of medications plus pacemaker.

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