A heart that feels like it is “racing” or beating too quickly, known medically as tachycardia, can be alarming when coupled with a common cold. This rapid heart rate is a recognized physiological response, and it is not just an imagined symptom during illness. An infection places a greater workload on the cardiovascular system. This phenomenon results either from the body’s natural immune response or as a direct side effect of cold medications. Understanding these causes helps determine when an elevated heart rate is an expected reaction and when it signals a need for medical evaluation.
How Infection Increases Cardiac Demand
The body’s response to a viral infection, such as a cold, naturally increases the heart’s workload. The immune system requires more energy and oxygen to fight the invading virus. This means the heart must pump blood faster to meet the heightened metabolic demand throughout the body, delivering immune cells and necessary nutrients more efficiently.
A primary cause of heart rate elevation during a cold is fever. For every one-degree Celsius rise in body temperature (or about 1.8 degrees Fahrenheit), the heart rate increases by approximately 7 to 10 beats per minute. This relationship is a compensatory mechanism that helps dissipate heat while simultaneously boosting circulation. The heart rate remains high even during periods of rest or sleep when the body is febrile.
Dehydration is another significant factor contributing to a faster heart rate during illness. Colds often lead to reduced fluid intake, combined with increased fluid loss from fever, sweating, or vomiting. When the body’s fluid volume decreases, blood volume also drops. This forces the heart to work harder and faster to maintain adequate blood pressure and circulate the remaining blood effectively.
Medication-Induced Tachycardia
Many over-the-counter cold and flu preparations contain ingredients that directly stimulate the cardiovascular system, independent of the infection. Decongestants are a common culprit for causing an elevated heart rate. These medications, which often contain pseudoephedrine or phenylephrine, are classified as sympathomimetic amines.
These substances mimic the effects of the body’s natural stress hormones, such as norepinephrine and epinephrine, activating adrenergic receptors. By stimulating alpha-adrenergic receptors, decongestants cause vasoconstriction, or the narrowing of blood vessels. This reduces swelling in the nasal passages to relieve congestion, but this widespread vasoconstriction can also lead to increased blood pressure.
The stimulation of these receptors also has a positive chronotropic effect, directly increasing the heart rate. Pseudoephedrine is known to cause an increase in heart rate and is classified as a positive chronotrope. People with pre-existing conditions like hypertension or underlying heart rhythm issues may be sensitive to these effects. Common stimulants like caffeine, often consumed when fatigued by a cold, can compound this effect and further drive up the heart rate.
When to Seek Medical Attention
While an elevated heart rate is often a normal part of the body’s defense, certain symptoms or sustained measurements should prompt a medical consultation. If your resting heart rate remains persistently above 100 beats per minute, contact a healthcare provider for an evaluation. An elevated heart rate that continues for an extended period after the fever has broken or the cold has begun to resolve also warrants professional advice.
Immediate medical attention is necessary if a rapid heart rate is accompanied by severe symptoms. These signs include:
- Chest pain or discomfort.
- Significant shortness of breath or difficulty breathing disproportionate to the illness.
- Episodes of lightheadedness or dizziness.
- Fainting, which may suggest the heart is not pumping blood effectively.
Individuals who have a history of heart disease, such as atrial fibrillation or heart failure, must be vigilant. They should consult their cardiologist upon noticing any significant or prolonged change in their heart rhythm.