Sudden Heart Racing During Exercise: Doctors Explain SVT and Warning Signs

Your heart suddenly starts pounding during a workout. The rhythm feels erratic and frightening. Many people dismiss these episodes as anxiety or dehydration. Doctors now warn these sudden spikes could indicate a serious condition.

Understanding Supraventricular Tachycardia

Dr Kunal Sood, a Maryland-based physician specializing in Anesthesiology and Interventional Pain Medicine, recently explained this phenomenon. He says sudden heart racing episodes often result from supraventricular tachycardia or SVT.

"If you've ever felt your heart suddenly take off mid-workout, this is likely what's happening," Dr Sood states. "What you're seeing here is an episode of supraventricular tachycardia."

How SVT Differs from Normal Heart Rate Increase

Dr Sood clarifies the distinction between SVT and typical exercise-induced heart rate elevation. "It's the rhythm where the heart suddenly starts beating very fast, often 170 beats per minute or higher, without gradually speeding up," he explains.

The underlying mechanism involves an electrical short circuit in the heart's upper chambers. Normal signal flow gets disrupted. Electrical impulses loop rapidly instead. This forces the heart to beat much faster than appropriate for the activity level.

Common Triggers and Unexpected Onset

Several factors can trigger SVT episodes according to medical experts:

Exercise or physical exertion
Emotional stress and anxiety
Dehydration and electrolyte imbalance
Lack of sleep or chronic sleep deprivation
Stimulants like caffeine from coffee, energy drinks, or pre-workout supplements

"That's why it can show up unexpectedly during a run or a workout," Dr Sood notes. The condition doesn't always follow predictable patterns.

Recognizing SVT Versus Normal Fast Heart Rate

Dr CM Nagesh, honorary secretary of the Indian College of Cardiology and Founder of Cardea Super Speciality Hospital, explains the key differences. A normal fast heart rate usually builds up gradually during exercise or stress. It settles down naturally once the trigger passes.

In contrast, SVT often starts and stops suddenly without warning. "People describe it as a switch being flipped," Dr Nagesh says. "The heart suddenly races very fast, often above 150 beats per minute, even while resting."

Associated Symptoms

SVT episodes frequently accompany additional symptoms that distinguish them from normal physiological responses:

Dizziness or lightheadedness
Chest discomfort or pain
Shortness of breath
A fluttering sensation in the chest
Sometimes near-fainting or actual fainting

These symptoms rarely occur with typical exercise-induced heart rate increases.

Immediate Steps During an Episode

Dr Sood outlines practical actions to take when experiencing sudden heart racing:

First, stop your activity immediately. Rest and stay calm. Anxiety can worsen the episode.

Try vagal manoeuvres. These techniques stimulate the vagus nerve which helps regulate heart rhythm:

Bear down as if having a bowel movement
Practice slow, deep breathing
Gently splash cold water on your face
Try coughing forcefully

These methods sometimes help reset the heart's electrical rhythm naturally.

Lifestyle Factors Increasing SVT Risk

Dr Nagesh identifies several lifestyle elements that can trigger SVT in otherwise healthy adults:

Excessive caffeine intake from multiple sources overstimulates the heart's electrical system. Energy drinks and pre-workout supplements pose particular risks.

Poor sleep patterns and chronic sleep deprivation increase stress hormones. This makes abnormal heart rhythms more likely to occur.

Dehydration and electrolyte imbalance especially involving low potassium or magnesium levels can provoke SVT episodes.

Additional factors include alcohol consumption, smoking, and high emotional stress. These can increase susceptibility even without underlying heart disease.