The sudden sensation of a fluttering or “skipped” beat in the chest can be startling, leading many people to search for an explanation for this irregular heart rhythm. These sensations are often caused by premature heartbeats, known medically as ectopic beats, which interrupt the heart’s normal, steady rhythm. The two most frequent types of these early contractions are Premature Atrial Contractions (PACs) and Premature Ventricular Contractions (PVCs). While these terms may provoke anxiety, they are extremely common and are often observed in people with otherwise healthy hearts.
Defining Premature Heartbeats
Premature heartbeats occur when an electrical impulse fires from a location other than the heart’s natural pacemaker, the sinoatrial (SA) node, causing the heart muscle to contract ahead of schedule. The distinction between PACs and PVCs rests entirely on where this misfired electrical signal originates within the heart’s four chambers. Premature Atrial Contractions arise in the atria, the two upper collecting chambers of the heart. The impulse begins in an abnormal spot within the atrial tissue and prematurely activates the heart’s electrical system.
A PVC, conversely, originates in the ventricles, the two muscular lower pumping chambers. This electrical signal starts in an “ectopic focus” within the ventricular wall, causing a chaotic, early contraction. The feeling of a “skipped beat” or a strong “thump” reported by patients is typically the result of a PVC. This sensation is caused by a compensatory pause following the premature beat, which allows the ventricle to fill with extra blood, making the next normal beat notably more forceful.
Common Triggers and Underlying Causes
Although the exact cause of premature heartbeats is often unknown, many episodes are linked to modifiable external and internal factors. Lifestyle triggers include the consumption of stimulants such as caffeine, nicotine, and alcohol. Elevated levels of adrenaline, brought on by stress, anxiety, or lack of sleep, can also increase the electrical excitability of heart muscle cells.
Internal physiological conditions also play a role in provoking these extra beats. Dehydration or an imbalance in electrolytes, specifically low levels of potassium or magnesium, can affect the heart’s electrical stability. Certain cold and allergy medications containing stimulants, such as decongestants, are also known to temporarily increase the frequency of PACs and PVCs.
Assessing Clinical Significance
The primary question for individuals experiencing premature beats is whether they signal a serious underlying health problem. Clinicians determine the clinical significance of PACs and PVCs by assessing the patient’s symptoms and the structural health of the heart. Isolated, infrequent beats in a person with a structurally normal heart are generally considered benign, but symptoms like chest pain, fainting, or severe dizziness warrant immediate medical evaluation.
Diagnostic tools include a 12-lead electrocardiogram (ECG) and a 24- to 48-hour Holter monitor, used to quantify the frequency and pattern of the beats. An echocardiogram (an ultrasound of the heart) is performed to rule out structural heart disease, which is the most important determinant of risk. For example, a PVC “burden” that accounts for more than 10 to 20 percent of all heartbeats can, over time, lead to a weakening of the heart muscle, a condition called cardiomyopathy. Though PACs are generally less worrisome than PVCs, a high burden of PACs is sometimes associated with an increased risk of developing atrial fibrillation later in life.
Approaches to Management
Management of premature heartbeats begins with non-invasive lifestyle changes designed to minimize known triggers. Patients are advised to reduce or eliminate caffeine and alcohol intake, quit tobacco use, and implement stress-reduction techniques like meditation and improved sleep hygiene. Ensuring proper hydration and addressing electrolyte imbalances can also decrease the frequency of both PACs and PVCs.
If premature beats are frequent, cause severe symptoms, or are associated with underlying heart disease, medical intervention may be necessary. Medications such as beta-blockers are commonly prescribed to slow the heart rate and reduce the excitability of the heart muscle. For patients with high-burden, symptomatic, or drug-resistant PVCs, a procedure called catheter ablation may be considered. This minimally invasive treatment uses radiofrequency energy to precisely destroy the small area of heart tissue generating the abnormal electrical signals.