Why Is My Heart Racing?

That sudden racing heartbeat can be terrifying. Whether it happens when you stand up, during exercise, or seemingly out of nowhere, heart palpitations are a common reason people seek medical care. But not all rapid heartbeats are the same: some reflect normal physiology, some reflect treatable non-cardiac triggers, and some reflect arrhythmias that need closer evaluation.

Understanding the different causes of palpitations is useful because the same sensation can come from very different rhythms. This guide breaks down common possibilities and the clinical features that often determine how they are evaluated.

Understanding Palpitations: More Than Just a Fast Heartbeat

Palpitations are the sensation of your heart beating rapidly, irregularly, or more forcefully than usual. They can feel like:

Racing or pounding
Fluttering or "flip-flopping"
Skipping beats
Irregular rhythm

The key to proper diagnosis lies in understanding the underlying rhythm causing these sensations.

Common Lower-Risk Causes

Sinus Tachycardia: Your Heart's Natural Response

What it is: Your heart beating faster than 100 beats per minute, but maintaining a regular rhythm through the normal electrical pathway.

Common triggers:

Exercise or physical activity
Stress, anxiety, or emotional excitement
Caffeine, alcohol, or certain medications
Fever or illness
Pain or discomfort

How it feels: A steady, rapid heartbeat that gradually increases and decreases with the triggering activity.

Why it is often lower risk: This is the heart's expected response to increased oxygen demand or sympathetic activation. The rhythm is still coming through the usual electrical pathway, just faster.

Orthostatic Changes: The Stand-Up Challenge

What it is: Heart rate changes when moving from lying or sitting to standing, sometimes called orthostatic hypotension or POTS (Postural Orthostatic Tachycardia Syndrome).

What happens:

Blood pools in your legs when you stand
Blood pressure temporarily drops
Heart rate increases to compensate

Symptoms:

Racing heart upon standing
Dizziness or lightheadedness
Temporary weakness

Why context matters: A sustained rise of 30 beats per minute or more in adults, paired with orthostatic symptoms and without a major blood-pressure drop, is part of how POTS is evaluated; brief lightheadedness after standing quickly is a different pattern.

Arrhythmias to Consider

Supraventricular Tachycardia (SVT): The Circuit Problem

What it is: A rapid heart rhythm originating above the ventricles, often due to an extra electrical pathway in the heart.

Characteristics:

Sudden onset and termination
Very regular, rapid rate (usually 150-250 beats per minute)
Episodes last minutes to hours

How it feels:

Heart "switches on" to rapid mode suddenly
May feel like heart is "revving like an engine"
Often accompanied by chest discomfort or shortness of breath

Why it matters: While not always life-threatening, SVT can be uncomfortable and may require treatment, especially if episodes are frequent or prolonged.

Atrial Flutter: The Circular Pattern

What it is: The atria beat in a rapid, regular pattern, but the ventricles beat slower due to the heart's natural electrical system.

How it presents:

Regular rapid heartbeat
Often feels similar to SVT but may be more sustained
May cause fatigue or shortness of breath

The concern: Like AFib, atrial flutter can increase stroke risk and may progress to more serious rhythms.

Higher-Risk Rhythms and Presentations

Atrial Fibrillation with Rapid Ventricular Response (RVR)

What it is: AFib where the ventricles are beating very rapidly (usually over 120 beats per minute), causing inefficient heart pumping.

Symptoms that can occur:

Irregular, rapid heartbeat
Chest pain or pressure
Severe shortness of breath
Dizziness or near-fainting
Weakness or fatigue

Why it matters: Rapid AFib can worsen symptoms and strain the heart, while AFib itself is associated with increased stroke risk. Severity depends on rate, duration, underlying heart function, and other risk factors.

Ventricular Tachycardia (VT)

What it is: Rapid rhythm originating from the ventricles—the heart's main pumping chambers.

Critical characteristics:

Heart rate usually 150-250 beats per minute
May cause hemodynamic instability
Can progress to ventricular fibrillation (cardiac arrest)

Symptoms that raise concern:

Chest pain
Severe shortness of breath
Loss of consciousness or near-fainting
Severe dizziness

High Risk Symptoms

Palpitations accompanied by the following symptoms are higher risk than routine outpatient palpitations:

Chest pain or pressure
Severe shortness of breath
Loss of consciousness or near-fainting
Severe dizziness that doesn't resolve
A sustained, very rapid rhythm with worsening symptoms

The Diagnostic Challenge: Why Rhythm Documentation Matters

The Intermittent Nature Problem

Many palpitations are intermittent, making them difficult to capture during a brief medical visit. A normal EKG does not exclude a rhythm that was absent during the recording; it describes the rhythm present during those seconds.

The Symptom-Rhythm Correlation

Understanding what rhythm is present during symptoms matters because the same sensation — racing, fluttering, pounding — can have very different causes and treatments.

How Extended Monitoring Provides Answers

Capturing the Rhythm During Symptoms

Extended monitoring with devices like the Zio® patch can:

Record every heartbeat for up to 14 days
Capture intermittent episodes that may not appear during a brief visit
Correlate symptoms with actual heart rhythms
Help distinguish normal rhythm, premature beats, and sustained arrhythmias

Sources & Further Reading

This article draws on peer-reviewed clinical literature:

Palpitations: Evaluation in the Primary Care Setting. American Family Physician (2017) — common causes of palpitations and features associated with cardiac etiologies.
Diagnosis and Treatment of Atrial Fibrillation. American Family Physician (2016) — irregular pulse as a clue to AFib and the need for ECG confirmation.
ACC/AHA/HRS Syncope Evaluation and Treatment Guidelines. American Family Physician (2018) — ambulatory monitoring options and matching monitor type to symptom frequency.

The Bottom Line: Match the Symptom to the Rhythm

Palpitations exist on a spectrum from normal physiology to clinically important arrhythmias. The key factors used to sort them include:

Pattern: Regular vs. irregular
Duration: Seconds vs. minutes vs. hours
Associated symptoms: Chest pain, shortness of breath, dizziness
Triggers: Exercise, position changes, stress
Frequency: Rare episodes vs. daily occurrences

When symptoms are intermittent, ambulatory monitoring can connect the sensation to the rhythm present at that moment. That documentation is what turns a broad differential into a specific finding.

This blog post is for educational purposes only and is not a substitute for professional medical advice. If you're experiencing chest pain, severe shortness of breath, or think you're having a heart attack, call 911 immediately.