Premature atrial contractions (PACs) are early heartbeats that start in the atria. Occasional PACs are not cause for concern and can even occur in teenagers and children. Usually, they are benign and go away on their own. Doctors typically do not treat PACs unless the person has frequent symptoms that interfere with day-to-day life, or if the doctor considers the PAC harmful and an underlying disease had been identified.
Electrical signals cause the heart to contract and control the rate and rhythm of each heartbeat. These signals start at the top of the heart in the atria and move to the bottom ventricles. Normally, the signal begins in the sinoatrial (SA) node, a group of cells in the right atrium. It moves through the atrioventricular (AV) node, which sits between the atria and ventricles, slowing the signal down slightly so the ventricles can fill with blood. The AV node then sends a signal through the ventricles to stimulate contraction, and the process starts again.
During a premature atrial contraction, the electrical signal does not originate from the SA node.
Premature atrial contractions have many causes, some of the most common being alcohol and tobacco use, fatigue, anxiety, and pregnancy. PACs also occur if there is a structural change in the heart, like heart disease, a malformation, or coronary artery disease. PACs can also result from medications, including beta-blockers, chemotherapy, and certain antidepressants.
Some chronic conditions also cause an increased incidence of PACs, like type 2 diabetes, COPD, and congestive heart failure.
Symptoms of premature atrial contractions are nonspecific, and most people have none. Some report feeling like their heart is skipping a beat or palpatations. Physical exams often lack specific findings since the unpredictable nature of a PAC means they tend not to occur during the exam.
When PACs happen regularly and frequently, the effects are more significant and may resemble symptoms of heart failure, like shortness of breath, fatigue, coughing, wheezing, confusion, or increased heart rate.
Premature atrial contractions are some of the most common forms of arrhythmias, and have many causes. An EKG is useful for determining whether the cause should be further investigated and whether treatment is necessary. Although many cases of PAC are benign, some may change into atrial fibrillation or atrial flutter, which can lead to more serious complications.
For people who have no symptoms and negative EKG findings, no further investigation is necessary. Doctors will perform additional testing if PAC causes palpitations in relation to physical exercise or if they exhibit symptoms of other cardiac conditions. EKG exercise testing evaluates people who have palpitations on exertion. Those who are at high risk for heart disease or other cardiac conditions may need 24-hour cardiac monitoring.
Treatment for premature atrial contractions varies based on the cause and triggers. Only people with symptomatic PACs need treatment. Doctors usually first work to identify and help patients avoid triggers. If this approach is unsuccessful, medication is the next step. Low-dose beta-blockers are the preferred pharmacological treatment.
If symptoms continue or worsen despite pharmacological interventions, additional management is needed. The patient may receive an atrial pacemaker or a catheter ablation.
In an ablation, an electrophysiology study tests and maps the electrical activity in the heart to locate the signal causing the PACs. Once identified, the area is ablated — the tissue is removed — using heat or cold to disrupt the electrical pathway.
Frequent premature atrial contractions are often associated with an increased risk of atrial fibrillation. Atrial fibrillation is a common arrhythmia that causes the upper heart chambers to beat irregularly, which prevents the ventricles from filling with blood. Some studies attribute this to frequent PACs that change the structure of the tissues near the SA node, eventually causing dysfunction.
One study took an in-depth look at premature atrial contractions in the general population. Results show a strong relationship between PACs and a history of cardiovascular disease. Extra heartbeats that originate in the lower chambers of the heart or premature ventricular contractions are also strongly correlated with PACs.
This study also demonstrated that some factors that do not seem to influence PACs, like height and obesity, and that increasing HDL or "good" cholesterol and physical activity can help people better manage the condition.
The prognosis for someone experiencing premature atrial contractions depends on the cause. Many PACs are benign, isolated, and resolve on their own. PACs that persist can be associated with an increased risk of dangerous cardiac issues in the future. Complications also depend on the underlying cause and include ischemic stroke and atrial fibrillation.
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