Atrial Rhythms Explained

• Atrial rhythms start in one or more irritable locations in the atria.
• These rhythms are also called ectopic rhythms.

Conduction of Atrial Rhythms

• A single atrial impulse depolarizes the atria, writing a P wave on the EKG, then heads down the pathway normally, and a QRS is written
• Multiple atrial impulses write a P wave (or alternate atrial wave) then head down the pathway normally and write a QRS
• The atrium is another pacemaker of the heart and produces rhythms with rapid heart rates, causing patients to be symptomatic.
• Treatment is aimed at converting the rhythm back to sinus rhythm, or if that is not possible, returning the heart rate to more normal levels.

Atrial Rhythm Criteria

• Matching upright Ps, atrial rate > 160 at rest, or absence of Ps with a wavy or sawtooth baseline, or P waves of ≥ 3 different shapes.
• Also premature abnormal P wave interrupting another rhythm, or heart rate ≥ 130, rhythm regular, P waves not discernible
• Atrial rhythms can have a positive or negative QRS depending on the lead being monitored

Wandering Atrial Pacemaker (WAP) & Multifocal Atrial Tachycardia (MAT)

• Rhythms occur when pacemaking impulses originate from at least 3 foci in the atria, each producing a unique P wave.
• WAP is a slow atrial arrhythmia while MAT is rapid; they are the same rhythm with different heart rates.

Rate

• WAP has a mean rate of <100, usually in the 50s to 60s while MAT rate is >100.
• Both rhythms have irregular regularity and P waves with at least 3 different shapes.

Intervals

• WAP and MAT have varying PR intervals and QRS of <0.12 seconds.

Causes

• WAP is caused by medication side effects, hypoxia, or vagal stimulation, or MI.
• MAT is caused by COPD or heart disease.

Adverse Effects

• WAP usually has no ill effects.

Treatment

• MAT can cause decreased cardiac output if heart rate is too fast.
• WAP requires no treatment.
• MAT is treated with beta blockers or calcium channel blockers if decreased cardiac output exists.

Premature Atrial Complexes (PACs)

• PACs are premature beats fired out by irritable atrial tissue.
• The premature P wave may or may not be followed by a QRS, depending on how premature the PAC is.
• If very premature, it won't be conducted to the ventricle because it will arrive during the ventricle's refractory period.
• PACs can occur at any rate, with regular regularity interrupted by PACs.

P Wave Characteristics

• P waves are shaped differently from sinus P waves and may be hidden in the T wave of the preceding beat.
• If the PAC's P wave is inverted, the PR interval should be normal (0.12 to 0.20 seconds).

Intervals of PACs

• PR interval is 0.12 to 0.20 seconds, QRS is <0.12 seconds.
• QRS will be absent after a nonconducted PAC.
• The most common cause of an unexplained pause is a nonconducted PAC.

Causes

• Atria fire early, caused by medications (stimulants, caffeine), tobacco, hypoxia, or heart disease; occasional PACs are normal.

Adverse Effects

• Frequent PACs can indicate impending heart failure or atrial tachycardia.
• Patients have no ill effects from occasional PACs.

Treatment

• Omit caffeine, tobacco, and stimulants, using digitalis, calcium channel blockers, or beta blockers if needed; treat heart failure if present.

Paroxysmal Atrial Tachycardia (PAT)

• PAT is A sudden burst of 3+ PAC's which usurps the existing rhythm, can resemble sinus tach, diagnosis is dependent on seeing the PAC that intitiates it.

Rate and Regularity

• PAT has rate of 160-250 within the atrial tachycardia itself, but is interrupted by a different rate.

P Waves and Intervals

• PAT has similar shaped atrial tachycardia Ps, but different to sinus P waves
• Interval has a PR of 0.12-0.20, constant, with QRS being <0.12

Cause and Treatment

• PAT causes can be the same as PAC, with prolonged runs causing a decrease in cardiac output
• Healthy people can tolerate it without symptoms, but those with heart issues may develop symptoms rapidly.
• Treat PAT with digitalis, calcium channel blockers, beta-blockers, adenosine, and oxygen. Electrolyte cardioversion can be considered if unstable

Atrial Flutter Definition

• An irritable atrial focus fires out impulses rapidly creating a flutter pattern instead of P waves.

The AV node

• The Atria fires impulses so fast that the AV node blocks some, acting as the protector of ventricles.

Atrial Flutter Key Facts

• Atrial rate: 250 to 350, ventricular rate depends on the conduction ratio
• Regularity: Regular if the conduction ration is constant.
• P Wave: None, instead flutter waves are present
• Intervals: No PR since there are no real P waves with a QRS <0.12secs

Additional Facts

• Atrial flutter can indicate heart disease and the impulses are rapid, so the AV node selectively blocks out some impulses.
• At normal rates Atrial Flutter is Can be well tolerated, but signs of decreased cardiac output can occur if not.
• Treatment includes; digitalis, calcium channel blockers, beta-blockers, adenosine, carotid sinus massage (to stimulate vagus nerve).

Atrial Fibrillation Definition

• Hundreds of atrial impulses from different locations all fire at the same time- The atria depolarize not as a unit but rather in small sections, the atria wiggle instead of contract.

Additional Facts

• Rate is 350 to 700, ventricular rate caries
• Irregular in regularity and completely unpredictable
• No P waves and instead and fibrillatory waves are present
• Intervals, cause and adverse effects are cause by lung diseas, and or MI
• If fibrillation is less than 48 hours the goal is to convert the rhythm back to sinus

Supraventricular Tachycardia (SVT)

• SVT is a catchall term when the exact origin cannot be identified because P waves are not discernible

Additional Facts About SVT

• Rate of 130 or higher, with regular regularity
• P Waves wont be discernible and cause be the same as PATs
• Adverse effects cause a decreased cardiac output with treatment including, Adenosine, digitalis, ibutilide, (medication to control A-fibs)

Atrial rhythms, also known as ectopic rhythms, originate from irritable locations in the atria. Single or multiple atrial impulses depolarize the atria, creating P waves on the EKG, before proceeding down the normal pathway to produce a QRS complex. Treatment focuses on restoring sinus rhythm or normalizing heart rate.