Heart palpitations are a sensation of a fast-beating, fluttering, or pounding heart that becomes uncomfortably noticeable in the chest, throat, or neck. Hypocalcemia is the medical term for an abnormally low level of calcium in the blood, defined as a total serum concentration below the normal range (approximately 8.5 to 10.4 milligrams per deciliter). A definitive link exists between low calcium levels and abnormal heart rhythms, known as arrhythmias, which are the underlying cause of palpitations.
The Essential Role of Calcium in Heart Function
Calcium ions are fundamentally involved in both the electrical signaling and the mechanical pumping action of the heart muscle. The rhythmic beating of the heart is governed by a precise electrical impulse, called the cardiac action potential, which travels through the heart cells. Calcium’s entry into the heart muscle cell (cardiomyocyte) is a key event that occurs during the plateau phase of this action potential.
This influx of calcium triggers a much larger release of stored calcium from the sarcoplasmic reticulum, a process known as calcium-induced calcium release. The released calcium then binds to specialized proteins, initiating the interaction between muscle filaments that causes the heart muscle cell to contract.
For the heart to relax, calcium must be quickly removed from the cell’s interior. Calcium acts as a regulator that couples the electrical signal (excitation) to the mechanical squeeze (contraction), ensuring a synchronized and forceful heartbeat. A stable level of calcium is required for the heart’s strength of contraction and for maintaining the appropriate timing of its electrical cycle.
Hypocalcemia and Resulting Cardiac Symptoms
Insufficient calcium directly destabilizes the electrical signals that coordinate the heart’s rhythm, making the heart muscle prone to abnormal beats. This disruption leads to various types of arrhythmias, which manifest as palpitations, skipped beats, or a racing heart.
A low calcium level significantly prolongs the repolarization phase of the cardiac action potential, the period when heart muscle cells reset for the next beat. This delay is visible on an electrocardiogram (ECG) as a prolonged QT interval. A prolonged QT interval is concerning because it predisposes the heart to develop life-threatening, chaotic rhythms, such as Torsades de Pointes.
These electrical abnormalities can trigger a rapid and irregular heart rhythm, which the patient feels as a noticeable palpitation. While palpitations can be mild, their presence in the setting of hypocalcemia suggests a potential for more serious rhythm disturbances.
Common Underlying Causes of Low Calcium Levels
Hypocalcemia most commonly occurs due to issues with the body’s regulatory system involving parathyroid hormone (PTH) and Vitamin D. A primary cause is hypoparathyroidism, a condition where the parathyroid glands do not produce enough PTH. PTH is the main hormone responsible for controlling blood calcium levels, and its deficiency is a frequent result of damage during thyroid surgery.
Vitamin D deficiency is another significant contributor because Vitamin D is necessary for the intestines to absorb calcium from food. Chronic kidney disease (CKD) is also a frequent cause, as impaired kidney function leads to poor phosphate excretion and reduces the ability to convert Vitamin D into its active form.
Certain medications can induce hypocalcemia by interfering with calcium metabolism, including some bisphosphonates, antiseizure medications, and corticosteroids. Additionally, low magnesium levels (hypomagnesemia) can cause hypocalcemia because magnesium is required for the parathyroid glands to produce and release PTH effectively.
Medical Evaluation and Management
If a person experiences persistent or worsening heart palpitations, especially when accompanied by symptoms like lightheadedness or muscle cramps, seeking prompt medical attention is advisable. Diagnosis for suspected hypocalcemia involves a blood test to measure the total serum calcium level. Doctors may also check for ionized calcium, the unbound, active form that directly affects heart function.
Additional blood tests are necessary to pinpoint the underlying cause, including measurements of parathyroid hormone (PTH), Vitamin D, magnesium, and phosphate levels. An electrocardiogram (ECG) is routinely performed to check for rhythm abnormalities and to look for the prolonged QT interval, a hallmark sign of hypocalcemia.
Management focuses on two main goals: rapidly correcting the low calcium level and treating the root cause. For severe hypocalcemia with cardiac arrhythmias, intravenous (IV) calcium, usually as calcium gluconate, may be administered in a monitored setting. For chronic, milder cases, treatment involves oral calcium supplements and active Vitamin D. Any underlying issue, such as hypoparathyroidism or Vitamin D deficiency, must be addressed under professional supervision to ensure safe and effective correction.