Differential Diagnosis for Variable Heart Rate
The patient's heart rate has fluctuated significantly, ranging from tachycardia (100-115 bpm) to bradycardia (67 bpm) and then back to a more normal range (80's to 90's bpm). This variability, combined with the question of a potential viral infection, suggests several possible diagnoses.
Single Most Likely Diagnosis
- Viral Myocarditis: This condition, where the heart muscle becomes inflamed due to a viral infection, can lead to variable heart rates, including both tachycardia and bradycardia, as the heart's electrical conduction system is affected. The presence of a viral infection could support this diagnosis.
Other Likely Diagnoses
- Dehydration or Electrolyte Imbalance: These conditions can cause fluctuations in heart rate, especially if the patient is experiencing significant fluid loss or has an imbalance in essential electrolytes like potassium or sodium.
- Anxiety or Stress: Both can lead to tachycardia, and in some cases, the body's response to prolonged stress might result in bradycardia as a rebound effect.
- Medication Side Effects: Certain medications can cause heart rate variability as a side effect, especially those that affect the autonomic nervous system or have direct effects on the heart.
Do Not Miss Diagnoses
- Cardiac Arrhythmias (e.g., Atrial Fibrillation, Supraventricular Tachycardia): These conditions can cause significant variability in heart rate and may be triggered by a viral infection or other stressors on the heart.
- Myocardial Infarction (Heart Attack): Although less common in younger individuals, a heart attack can cause variable heart rates among other symptoms and is crucial not to miss.
- Sepsis: In the context of a viral infection leading to bacterial superinfection, sepsis can cause significant heart rate variability due to the body's systemic response to infection.
Rare Diagnoses
- Postural Orthostatic Tachycardia Syndrome (POTS): A condition characterized by a rapid increase in heart rate upon standing, which could contribute to the observed variability.
- Neurocardiogenic Syncope: This condition involves a reflex of the involuntary nervous system that can cause a sudden drop in heart rate and blood pressure, leading to fainting spells.
- Thyroid Storm: A life-threatening complication of untreated or undertreated hyperthyroidism, which can cause significant tachycardia among other symptoms.
Each of these diagnoses should be considered in the context of the patient's overall clinical presentation, medical history, and the results of diagnostic tests such as ECG, blood work, and potentially imaging studies.