Sudden Heart Rate Increases: Causes and Risks

Sudden increase in heart rate?

Hello Doctor, in August this year, I woke up feeling chest tightness.
On my way to work, my heart suddenly raced to about 150 beats per minute, accompanied by dizziness and difficulty breathing, lasting for about an hour.
I went to the hospital where an electrocardiogram (ECG), exercise stress test, and echocardiogram were all normal.
The results of the 24-hour Holter monitor are as follows: 1.
Basic rhythm: Sinus rhythm; Max/min/mean HR 150/44/76 BPM; Total 105,743 beats.
2.
Atrial ectopy: Total 17 isolated atrial premature contractions (APCs).
3.
Ventricular ectopy: None.
4.
Short-run of tachyarrhythmia except atrial fibrillation: None.
5.
High-grade atrioventricular block: None.
6.
Sinus pause: No pause longer than 2.0 seconds.
7.
Paroxysmal atrial flutter/fibrillation: None.

Since all results were normal and there have been no further episodes, the doctor advised me to continue monitoring and to return to the hospital if I feel unwell.
They prescribed antiarrhythmic medication to take as needed.
However, in December, I experienced another episode where my heart rate suddenly increased to 160 beats per minute without any physical activity, accompanied by dizziness.
After taking the medication and resting, my heart rate returned to about 90 beats per minute in approximately 10 minutes.

I would like to ask what possible causes there could be for these symptoms? Is there an immediate risk to my life? Would you recommend any additional tests? Thank you!

ALLEN, 30~39 year old female. Ask Date: 2023/12/11

Dr. Wu Xueming reply Cardiology

The 24-hour electrocardiogram did not show any dangerous arrhythmias, so there is no need to worry.

Reply Date: 2023/12/11

More Info

Sudden increases in heart rate, known as tachycardia, can be alarming and may occur due to various reasons. In your case, the episodes of rapid heart rate (up to 160 beats per minute) accompanied by symptoms such as dizziness and shortness of breath warrant careful consideration. While your previous tests, including ECG, echocardiogram, and 24-hour Holter monitoring, returned normal results, it is essential to understand the potential causes and risks associated with these symptoms.

Possible Causes of Sudden Heart Rate Increases
1. Autonomic Nervous System Imbalance: The autonomic nervous system regulates heart rate and can be influenced by stress, anxiety, or fatigue. Given your mention of anxiety and autonomic dysfunction, it is possible that these factors contribute to your episodes of tachycardia.

2. Physical Activity and Fatigue: Engaging in prolonged physical activity can lead to temporary increases in heart rate. If you have been more active than usual or are experiencing fatigue, your heart may respond by increasing its rate to meet the body's demands for oxygen.

3. Caffeine and Stimulants: Consumption of caffeine or other stimulants can lead to increased heart rate. If you have recently consumed caffeinated beverages or medications that stimulate the heart, this could be a contributing factor.

4. Hormonal Changes: Hormonal fluctuations, such as those related to stress or thyroid function, can also affect heart rate. Conditions like hyperthyroidism can lead to persistent tachycardia.

5. Underlying Heart Conditions: Although your tests have shown no significant abnormalities, conditions such as mitral valve prolapse or other structural heart issues can sometimes lead to episodes of tachycardia. It is essential to monitor any changes in your symptoms.

Risks Associated with Tachycardia
While occasional episodes of tachycardia may not pose an immediate threat, persistent or severe tachycardia can lead to complications, including:
- Heart Failure: Prolonged periods of rapid heart rate can weaken the heart muscle over time, leading to heart failure.

- Stroke: Certain types of tachycardia, particularly atrial fibrillation, can increase the risk of blood clots forming in the heart, which can lead to a stroke.

- Cardiac Arrest: In rare cases, extremely high heart rates can lead to life-threatening arrhythmias.

Recommendations for Further Evaluation
Given your symptoms and the recurrence of tachycardia, it may be prudent to consider additional evaluations:
1. Repeat Holter Monitoring: A longer duration of monitoring may capture more episodes of tachycardia and provide insight into their frequency and triggers.

2. Electrophysiological Study: If episodes continue, an electrophysiological study may help identify any underlying arrhythmias that were not detected in previous tests.

3. Stress Test: A supervised exercise stress test can help determine how your heart responds to physical exertion and may reveal any exercise-induced arrhythmias.

4. Consultation with a Cardiologist: If you have not already done so, a referral to a cardiologist specializing in arrhythmias may provide further insights and management options.

Conclusion
While your initial tests have shown no significant abnormalities, the recurrence of tachycardia and associated symptoms should not be ignored. It is essential to maintain open communication with your healthcare provider and report any new or worsening symptoms. Lifestyle modifications, such as managing stress, avoiding stimulants, and ensuring adequate rest, can also play a crucial role in managing your heart health. If your symptoms persist or worsen, seeking immediate medical attention is advisable to rule out any serious underlying conditions.

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