Atrial Fibrillation: Understanding the Difference Between Heart Rate and Pulse

One of the key characteristics of atrial fibrillation (AFib) is the discrepancy between heart rate and pulse. This occurs because not every rapid and irregular heartbeat during AFib is strong enough to generate a detectable pulse. This mismatch leads to what is known as "pulse deficit," where the pulse rate is lower than the actual heart rate.

What Causes the Pulse Deficit in Atrial Fibrillation?

AFib is a type of arrhythmia where the heart's electrical signals become chaotic, particularly in the atria. This often results from structural changes in the atria, which can be caused by various heart conditions. In many cases, patients with enlarged atria are more prone to AFib. Interestingly, AFib itself can further contribute to atrial enlargement, creating a harmful cycle that worsens the condition over time.

Why Does the Heart Rate Spike During Atrial Fibrillation?

During normal heart function, the sinoatrial (SA) node controls the heartbeat at a rate of 60 to 100 beats per minute. However, in AFib, the atria can beat at an extremely high rate—ranging from 300 to 600 beats per minute. Due to this rapid firing, not every electrical impulse successfully travels through the atrioventricular (AV) node to the ventricles.

How Does This Affect the Peripheral Pulse?

Even when some of these impulses do reach the ventricles, the resulting heartbeats may be too weak to produce a noticeable pulse in the peripheral arteries, such as the radial artery in the wrist. As a result, when a healthcare provider checks the pulse at the wrist, they may detect fewer beats than the actual heart rate measured by an electrocardiogram (ECG). This phenomenon is known as pulse deficit and is a hallmark of uncontrolled AFib.

Implications for Diagnosis and Management

Recognizing the difference between heart rate and pulse in AFib is crucial for accurate diagnosis and effective treatment. Clinicians often rely on both pulse palpation and ECG monitoring to identify pulse deficits and assess the severity of the arrhythmia. Managing AFib typically involves rate or rhythm control strategies, along with anticoagulation therapy to reduce stroke risk.