From the Guidelines
Laboratory tests for determining the cause of sinus tachycardia should include a complete blood count (CBC), comprehensive metabolic panel, thyroid function tests, cardiac biomarkers, and toxicology screening, as these tests can help identify underlying conditions such as anemia, infection, hyperthyroidism, heart failure, and substance use. When evaluating a patient with sinus tachycardia, it is essential to consider the potential underlying causes, which can include physiological and pathological conditions, as outlined in the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1. Some key tests to consider include:
- Complete blood count (CBC) to check for anemia or infection
- Comprehensive metabolic panel to assess electrolyte imbalances, particularly potassium, magnesium, and calcium
- Thyroid function tests to rule out hyperthyroidism
- Cardiac biomarkers like troponin to check for myocardial injury and B-type natriuretic peptide (BNP) to evaluate for heart failure
- Toxicology screening if substance use is suspected
- Cortisol level to assess for adrenal disorders
- Arterial blood gases to identify hypoxemia or acidosis These tests are crucial because sinus tachycardia is often secondary to underlying conditions rather than a primary disorder, and identifying the underlying cause is vital for appropriate management of the tachycardia, as emphasized in the guidelines 1.
From the Research
Sinus Tachycardia Causes
- Sinus tachycardia (ST) can be caused by various medical conditions, including pulmonary embolism, anemia, infection, or hyperthyroidism 2
- It can also be related to incompletely defined conditions such as inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome 2
- Hyperthyroidism is a known cause of sinus tachycardia, with studies showing that tachycardia is present in 28.2% of patients with hyperthyroidism 3
- However, another study found that sinus tachycardia was observed in 60.19% of patients with primary hyperthyroidism, highlighting the importance of thyrotoxicosis as a cause of cardiac morbidity and mortality 4
- Laboratory tests, such as thyroid-stimulating hormone (TSH) and free thyroid hormone tests, are essential in diagnosing and managing thyroid disorders, including hyperthyroidism 5
Laboratory Tests for Sinus Tachycardia
- Electrocardiogram (ECG) is a crucial test in diagnosing sinus tachycardia, with studies showing that ECG changes are common in patients with primary hyperthyroidism 4
- Blood tests, such as TSH, free thyroxine, and free triiodothyronine, are used to assess the functional status of the thyroid and diagnose hyperthyroidism 5
- Thyroid peroxidase antibodies (TPO-Ab) and TSH receptor antibodies (TRAb) tests are used to diagnose Hashimoto's thyroiditis and Graves' disease, respectively 5