Premature ventricular contractions (PVCs) are a common type of irregular heartbeat that originate in the heart’s lower chambers, the ventricles. Instead of the normal electrical signal starting in the upper chamber’s sinoatrial (SA) node, a PVC is an extra, abnormal beat that occurs too early. This premature signal disrupts the heart’s regular rhythm, which is why many people describe the sensation as a “skipped beat” or a flutter. PVCs are highly prevalent, occurring in people of all ages, with or without pre-existing heart conditions. Many healthy individuals experience them frequently, and they are generally considered harmless when they occur occasionally. Understanding their causes and when they signal a more serious underlying issue is important.
The Electrical Event
The normal heartbeat begins with an electrical impulse generated by the SA node, which acts as the heart’s natural pacemaker. This signal travels through the upper chambers (atria) and then through the atrioventricular (AV) node to the lower chambers (ventricles), ensuring a coordinated contraction. A PVC occurs when an electrical impulse spontaneously fires from an ectopic location within the ventricle before the SA node’s signal arrives. Since this premature signal travels outside the heart’s specialized conduction system, the resulting QRS complex appears wide and abnormal on an electrocardiogram (ECG).
This early ventricular contraction is often less effective at pumping blood. The PVC is typically followed by a “compensatory pause,” a longer-than-normal interval before the next regular beat. This pause occurs because the ventricle is temporarily refractory, meaning it cannot respond to the next scheduled signal from the SA node.
The subsequent normal heart contraction after this pause often feels stronger because the ventricle had more time to fill with blood. This forceful contraction is what patients commonly perceive as a “thump” or a sudden pound in the chest. This complete compensatory pause helps distinguish a PVC from other types of premature beats.
Common Causes and Triggers
The causes of PVCs are varied, often involving a mix of transient lifestyle factors and underlying medical conditions. Transient triggers, common in otherwise healthy individuals, include stimulants like excessive caffeine, tobacco, and alcohol use. These substances can increase adrenaline levels in the body, making the heart muscle cells more electrically irritable.
Increased physical or emotional stress and anxiety are also frequent non-cardiac causes due to the release of stress hormones. Sleep deprivation and the use of certain medications, such as decongestants or antihistamines, can similarly provoke PVCs. Addressing these modifiable lifestyle factors often helps reduce the frequency of the extra beats.
Underlying health issues also play a role in causing or exacerbating PVCs. Electrolyte imbalances, particularly low levels of potassium (hypokalemia) or magnesium (hypomagnesemia), can destabilize the heart’s electrical activity. Other medical conditions that may contribute include hypertension (high blood pressure), hyperthyroidism (an overactive thyroid), and anemia.
Recognizing the Symptoms and Diagnosis
While many people with PVCs remain entirely asymptomatic, the electrical event often manifests as noticeable sensations in the chest. The most frequently reported symptoms are a feeling of the heart “skipping a beat” or a momentary flutter. Patients may also describe a pounding, jumping, or thumping sensation, which corresponds to the stronger beat following the compensatory pause.
Less common symptoms include lightheadedness, dizziness, or a general awareness of the heartbeat. If the PVCs are very frequent, they can sometimes lead to fatigue or shortness of breath. A medical evaluation is necessary to confirm the diagnosis and rule out other causes of palpitations.
The primary diagnostic tool is the 12-lead ECG, which captures the heart’s electrical activity at a single moment. On the ECG, a PVC is characterized by a premature, wide QRS complex that typically lacks a preceding P wave. To assess PVC frequency and correlate them with symptoms, doctors use ambulatory monitoring devices.
A Holter monitor records the heart rhythm continuously, usually over 24 to 48 hours, providing a detailed count of PVCs. For less frequent symptoms, a patient may use an event recorder, which can be worn for several weeks and activated when symptoms occur. An echocardiogram is also routinely performed to check for underlying structural heart disease, which influences the seriousness of the diagnosis.
When PVCs Require Medical Attention
For the majority of people, isolated or infrequent PVCs are benign and require no specific treatment. However, the seriousness of PVCs is determined by their frequency, their complexity, and the presence of underlying heart disease. A high frequency, often referred to as a high “PVC burden,” is a concern.
When PVCs account for a high percentage of all heartbeats (sometimes cited as over 10,000 to 20,000 per day), they can weaken the heart muscle over time. This potentially leads to a reversible condition known as PVC-induced cardiomyopathy. High-risk PVCs also include those that occur in patterns like couplets (two in a row) or triplets, which are short runs of ventricular tachycardia. These complex PVCs increase the risk of more dangerous heart rhythms.
The most concerning scenario is when PVCs occur in individuals who have pre-existing structural heart disease, such as previous myocardial infarction or heart failure. In this group, the PVCs signal an increased risk of severe arrhythmias, including sudden cardiac death. Management for high-risk or highly symptomatic PVCs can range from lifestyle changes and medications like beta-blockers, to a catheter ablation procedure to eliminate the source of the abnormal electrical impulse.