Premature atrial contraction (PAC), also known as atrial premature complexes (APC) or atrial premature beats (APB), are a common
cardiac dysrhythmia characterized by premature heartbeats originating in the
atria. While the
sinoatrial node typically regulates the heartbeat during
normal sinus rhythm
A sinus rhythm is any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sinus node. It is characterised by the presence of correctly oriented P waves on the electrocardiogram (ECG). Sinus rhythm is necessary, but not s ...
, PACs occur when
another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat, in contrast to escape beats, in which the normal
sinoatrial node fails, leaving a non-nodal pacemaker to initiate a late beat.
The exact cause of PACs is unclear; while several predisposing conditions exist, single isolated PACs commonly occur in healthy young and elderly people. Elderly people that get PACs usually don't need any further attention besides follow ups due to unclear evidence.
PACs are often completely
asymptomatic and may be noted only with
Holter monitoring, but occasionally they can be perceived as a skipped beat or a jolt in the chest. In most cases, no treatment other than reassurance is needed for PACs, although medications such as
beta blockers can reduce the frequency of symptomatic PACs.
Risk factors
Hypertension
Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...
, or abnormally high blood pressure, often signifies an elevated level of both
psychological
Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries bet ...
and
physiological stress. Often, hypertension goes hand in hand with various
atrial fibrillations including premature atrial contractions (PACs). Additional factors that may contribute to spontaneous premature atrial contractions could be:
* Increased age
* Abnormal body height
* Family history of heart disease
* History of cardiovascular disease (CV)
* Abnormal
atrial natriuretic peptide (ANP) levels
* Elevated cholesterol
Diagnosis
Premature atrial contractions are typically diagnosed with an
electrocardiogram,
Holter monitor,
cardiac event monitor, or with a
smartwatch
A smartwatch is a wearable computer in the form of a watch; modern smartwatches provide a local touchscreen interface for daily use, while an associated smartphone app provides management and telemetry, such as long-term biomonitoring. Whil ...
with an ECG functionality.
Electrocardiogram
On an electrocardiogram (ECG), PACs are characterized by an abnormally shaped
P wave in different ECG leads. Since the premature beat initiates outside the
sinoatrial node, the associated P wave appears different from those seen in
normal sinus rhythm
A sinus rhythm is any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sinus node. It is characterised by the presence of correctly oriented P waves on the electrocardiogram (ECG). Sinus rhythm is necessary, but not s ...
. Typically, the atrial impulse propagates normally through the
atrioventricular node and into the
cardiac ventricles, resulting in a normal, narrow
QRS complex. However, if the atrial beat is premature enough, it may reach the atrioventricular node during its refractory period, in which case it will not be conducted to the ventricle and there will be no QRS complex following the P wave.
In some people, PACs occur in a predictable pattern. Two PACs in a row are called doublets and three PACs in a row are triplets. Depending whether there are one, two, or three normal (sinus) beats between each PACs, the rhythm is called atrial bigeminy, trigeminy, or quadrigeminy. If 3 or more consecutive PACs occur in a row and at a frequency of 100 or more beats per minute, it may be called
atrial tachycardia
Atrial tachycardia is a type of heart rhythm problem in which the heart's electrical impulse comes from an ectopic pacemaker (that is, an abnormally located cardiac pacemaker) in the upper chambers ( atria) of the heart, rather than from the sin ...
.
Treatment
Premature atrial contractions are often benign, requiring no treatment. Occasionally, the patient having the PAC will find these symptoms bothersome, in which case the doctor may treat the PACs. Sometimes the PACs can indicate
heart disease or an increased risk for other
cardiac arrhythmias. In this case, the underlying cause is treated. Often a
beta blocker will be prescribed for symptomatic PACs.
Prognosis
In otherwise healthy patients, occasional single premature atrial contractions are a common finding and most of times do not indicate any particular health risk. Rarely, in patients with other underlying structural heart problems, PACs can trigger a more serious arrhythmia such as
atrial flutter or
atrial fibrillation. In otherwise healthy people, PACs usually disappear with adolescence.
Supraventricular extrasystole
A supraventricular extrasystole (SVES) is an
extrasystole
A premature heart beat or extrasystole is a heart rhythm disorder corresponding to a premature contraction of one of the chambers of the heart. Premature heart beats come in two different types: premature atrial contractions and premature ventr ...
or premature electrical impulse in the
heart
The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
, generated above the level of the
ventricle. This can be either a premature atrial contraction or a premature impulse from the
atrioventricular node. SVES should be viewed in contrast to a
premature ventricular contraction that has a ventricular origin and the associated QRS change. Instead of the electrical impulse beginning in the sinoatrial (SA) node and propagating to the atrioventricular (AV) node, the signal is conducted both to the ventricle and back to the SA node where the signal began.
See also
*
Premature junctional contraction Premature junctional contractions (PJCs), also called atrioventricular junctional premature complexes or junctional extrasystole, are premature cardiac electrical impulses originating from the atrioventricular node of the heart or "junction". This a ...
*
Premature ventricular contraction
References
External links
{{Circulatory system pathology
Cardiac arrhythmia
de:Supraventrikuläre Extrasystole