If you are healthy, diet as well as the calcium in your bones keep your supply of blood calcium pretty constant. However, certain physiological conditions can alter the amount of calcium in your blood, causing hypercalcemia, too much calcium, or hypocalcemia, too little calcium. Either condition is stressful to your heart, causing arrhythmias that may cause detrimental harm.
Heart Beat
Your heart rate and electrical conductivity can be monitored by an electrocardiogram, or EKG. This gives you a picture of how each of your heart's chambers is contracting and relaxing. This picture looks like a series of waves, dips and spikes. The first wave is the P wave, which indicates the contraction of the atria. This is followed by a downward spike, then an upward spike, and another downward spike, which is the QRS interval. This indicates the contraction of the ventricles. The last wave is the T wave, which marks the repolarization of the ventricles. The QT interval is the length of time between a contraction and the repolarization or relaxation of the ventricle cardiac cells.
Mechanism
A study published in the journal "Nature" in January 2002 explains the mechanism of the action between calcium and your cardiac cells. Inside your cardiac cells are calmodulin and calcium. Calmodulin senses the amount of calcium in your cells. Then, by binding with a sodium channel protein inside your cells, it influences the heart rate and rhythm based on how much calcium your cells hold.
Hypercalcemia
On an EKG, hypercalcemia may manifest itself with a short QT interval. Atrial or ventricular fibrillation are the two arrhythmias associated with a short QT interval. Atrial fibrillation is characterized by fast and irregular beats that originate in the atrium. Symptoms can include dizziness, chest pain, fatigue and anxiety. This condition is not generally fatal. Ventricular fibrillation is life-threatening. It is an abnormal rhythm marked by the irregular and uncontrolled twinges from the cardiac cells of the ventricles. This prohibits blood from leaving the heart, so a run of ventricular fibrillation often results in sudden death.
Hypocalcemia
Hypocalcemia can cause a long QT interval, which may lead to two arrhythmias: torsades de pointes -- twist of the points -- or ventricular fibrillation. Torsades de pointes occurs when your ventricles beat irregularly fast. This makes it hard for blood to leave the heart. This condition is marked by a sudden onset of dizziness and fainting. If torsades de pointes corrects itself quickly, you can recover. However, it can lead to ventricular fibrillation, which is life-threatening.
References
- MayoClinic.com; Hypercalcemia; May 2011
- Cleveland Clinic; Hypocalcemia; Mario Skugor
- "Reporter: Vanderbilt University Medical Center's Weekly Newspaper"; Arrhythmias Linked to Calcium Levels -- Nature Study Directed by VUMC Anesthesiology Chair Balser; Mary Beth Gardiner; January 2002
- Cleveland Clinic; Hypercalcemia; Mario Skugor and Mira Milas
- Short QT Syndrome: Arrhythmias
- PubMed Health: Ventricular Fibrillation
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