What Causes Tachycardia?

Patient Presentation
A 25-day-old male came to clinic because he seemed to be eating differently for the past 24 hours. His mother described it as less interested, but he still would breastfeed for 20-30 minutes every 2.5-3 hours, but seemed overall more tired. He had a good suck, didn’t turn blue or sweat during feedings, and maybe was slightly more tired in general. His crying was normal as were his urination and stooling. The mother didn’t think he was having pain, rhinorrhea, cough, or a rash.

The past medical history showed a healthy male born at 40 1/7 weeks gestation without problems. His neonatal screening and critical congenital heart disease tests were negative. He had regained his birth weight by 11 days of age. The family history was negative for any congenital heart disease or arrhythmias. He had a maternal aunt who had an early pregnancy spontaneous abortion. There were no abnormal deaths in the families. The review of systems was otherwise negative.

The pertinent physical exam showed a heart rate of 180-190 beats/minutes, respiratory rate of 36, temperature of 98.9°F, and eventually four-point blood pressures that were normal. His weight was 4.23 kg (50%) and length of 54 cm (50%). HEENT showed a normal fontanele and wet mucous membranes. His heart examination had a III/VI systolic murmur best at the mid-to-lower sternal border that could be heard on the back and axilla but it was difficult to discern because of the sustained tachycardia. Neck and head examinations for murmur radiation couldn’t be appropriately evaluated. Pulses in the upper extremities and lower extremities were normal. His capillary refill was brisk without obvious color changes. His lungs and abdomen were normal. There were no obvious congenital abnormalities on the rest of his examination.

The diagnosis of sustained tachycardia in the setting of a new heart murmur was made. The tachycardia varied between 170-190 beats/minute but mainly stayed in the 180’s range. It did vary with movement or crying of the neonate. The clinic evaluation included an electrocardiogram which showed sinus tachycardia and a chest radiograph which showed a normal heart size.

The patient’s clinical course revealed the patient was transferred to the emergency department for further evaluation where laboratory testing was negative, and the patient’s heart rate had decreased to the 150’s range. Pediatric cardiology was consulted and felt the patient could safely be seen the following day, where an echocardiogram showed a small muscular ventricular septal defect. A Holter monitor was placed with followup planned in 3 days.

Tachycardia is a rapid heart rate that is above normal for age and level of exertion. Tachycardia is common, particularly sinus tachycardia due to normally encountered circumstances such as pain, fever or exercise. It is usually a normal physiologic process but sustained tachycardia often indicates a potentially abnormal underlying cause.

Sinus tachycardia has a rapid heart rate with normal P waves and P-R intervals and variations from moment to moment and respiration. Generally it is not over 200 beats/minute. Vagal stimulation can slow the heart rate; this is a gradual slowing, not an abrupt slowing seen in supraventricular tachycardia.

A supraventricular tachycardia has rapid fixed rates, and normal QRS complexes with no discernable P waves or P waves on top of T waves. Vagal stimulation causes no change or an abrupt change to sinus rhythm. Rates are usually 180-300 beats/minute.

Wide QRS complexes with usually a fixed rapid rate is a ventricular tachycardia but can also be a supraventricular tachycardia with ventricular aberration.

History always provides the primary context for evaluating tachycardia including recent illness, feeding problems, exercise or syncope, emotional state and especially medication use.

Physical examination should include evaluation of all vital signs with comparison to normal for age. Fever is commonly noted as can be dehydration when compared to previous weights. Four point blood pressures should be done if possible (congenital heart disease). Cardiac evaluation looking for distant heart sounds and/or pulseus paradoxus (pericardial effusion), S3 or S4 (cardiac dysfunction), and murmur (may be normal for state or are indicate underlying heart disease) can be helpful. Other physical examination findings may be helpful such as dry mucous membranes or prolonged capillary refill (dehydration), tachypnea and hepatomegaly (cardiac failure), poor perfusion (shock), pallor (anemia) and thyromegaly (hyperthyroidism).

Evaluation depends on history and physical examination but especially if a cardiac cause is suspected an electrocardiogram, chest radiograph and general laboratory testing (complete blood count, electrolytes, glucose, and calcium) usually are included in the initial testing. More extensive testing may be needed including echocardiogram, Holter monitoring, etc.

Treatment also depends on the underlying cause. It maybe as simple as calming an agitated patient, or treating a fever. But it can also be much more complicated with necessary specialty care, particularly cardiology.

Learning Point
The differential diagnosis of tachycardia includes:

  • Commonly encountered conditions
    • Anxiety
    • Crying
    • Dehydration
    • Exercise/exertion
    • Fever and/or infection
    • Medications – cough and cold medications, caffeine, legal or illegal drugs
    • Pain
  • Cardiac problems
    • Arrhythmias
      • Supraventricular tachycardia
      • Paroxysmal atrial tachycardia
      • Wolff-Parkinson White syndrome
      • Atrial fibrillation
      • Atrial flutter
      • Junctional tachycardia
      • Ventricular tachycardia
      • Ventricular fibrillation
    • Cardiac state, low or high output
      • Cardiac failure
      • Cardiomyopathy
      • Myocarditis
      • Hypertrophic cardiomyopathy
    • Pleural effusion
  • Other causes
    • Anaphylaxis
    • Anemia, acute or chronic
    • Acute rheumatic fever
    • Cancer
      • Cardiac tumors
      • Catecholine producing tumors
    • Drugs or toxins
      • Alpha-adrenergic agonists
      • Antiarrhythmics
      • Anticholinergics
      • Antidepressants
      • Antihistamines
      • Antimicrobials
      • Antipsychotics
      • Beta-blockers
      • Calcium channel blockers
      • Cardiac glycosides
      • Cholinergics
      • Opioids
      • Organophosphates
      • Sedative-hypnotics
      • Sympathomimetics
      • Arsenic
      • Citrate
      • Fluoride
      • Magnesium
      • Potassium
      • Thallium
      • Thyroid hormone
      • Carbon monoxide
      • Drug withdrawal
      • Caffeine
      • Tobacco
      • Herbals
    • Electrolyte disturbances
      • Hypoglycemia
      • Hypokalemia
      • Hypocalcemia
      • Hypomagnesemia
    • Hypoxemia
    • Hyperthyroidism
    • Kawasaki disease
    • Psychogenic, anxiety or other mental illness

Questions for Further Discussion
1. What are indications for an echocardiogram or Holter monitor?
2. What are indications for invasive treatment such as radioablation for an arrhythmia?
3. How is supraventricular tachycardia treated?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Arrhythmias and Congenital Heart Defects

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Crosson JE, Callans DJ, Bradley DJ, et.al. PACES/HRS expert consensus statement on the evaluation and management of ventricular arrhythmias in the child with a structurally normal heart. Heart Rhythm. 2014 Sep;11(9):e55-78. doi: 10.1016/j.hrthm.2014.05.010.

Srinivasan C. Diagnosis and Acute Management of Tachyarrhythmias in Children. Indian J Pediatr. 2015;82(12):1157-1163. doi:10.1007/s12098-015-1881-5

Corwin DJ, Scarfone RJ. Supraventricular Tachycardia Associated With Severe Anemia: Pediatr Emerg Care. 2018;34(4):e75-e78. doi:10.1097/PEC.0000000000001134

Mazor S, Mazor R. Approach to the Child with Tachycardia. UpToDate. (rev. 3/2/2019, accessed 12/17/19).

Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa