Asthma is a chronic inflammatory disorder affecting the airways, causing them to narrow, swell, and produce extra mucus. This results in episodes of wheezing, coughing, chest tightness, and shortness of breath. The physiological stress of an asthma episode and the medications used to treat it create a link between asthma control and heart rate. Changes in heart rate, most commonly an increase, are frequently observed during acute exacerbations and as a side effect of treatment.
The Body’s Acute Response to Airway Constriction
When the airways constrict during an asthma episode, the body’s natural defense mechanisms are immediately activated. This acute response is governed by the sympathetic nervous system, often called the “fight-or-flight” system. Struggling to breathe triggers the release of hormones, such as adrenaline and noradrenaline, which prepare the body for an emergency.
This surge of hormones directly stimulates the heart, causing the heart rate to increase, a condition known as tachycardia. Additionally, airway narrowing impairs gas exchange, often leading to a drop in blood oxygen levels, or hypoxia. The heart speeds up in a compensatory mechanism to pump available oxygen more rapidly to the body’s tissues.
The increased work of breathing and the anxiety associated with the feeling of suffocation further contribute to this cardiac acceleration. A severe asthma attack is characterized by a pulse rate that may be 100 beats per minute or more, reflecting the body’s struggle for oxygen.
How Asthma Medications Influence Heart Rhythm
Asthma relief medications often directly affect heart rhythm due to their pharmacological structure. Short-acting beta-agonists (SABAs), such as albuterol, and long-acting beta-agonists (LABAs) stimulate Beta-2 adrenergic receptors in the smooth muscle of the airways, leading to bronchodilation. These receptors are not exclusive to the lungs.
The heart contains Beta-1 and, to a lesser extent, Beta-2 adrenergic receptors. When beta-agonist medications are inhaled, a portion of the drug is absorbed systemically and activates these cardiac receptors. This direct stimulation results in an increased heart rate and force of contraction, often causing palpitations or temporary sinus tachycardia.
This effect is generally more pronounced and acute with SABAs, which are used for rescue, than with maintenance LABAs. A single dose of a beta-2 agonist can increase the heart rate by about nine beats per minute compared to a placebo.
The immediate effect of any beta-agonist is dose-dependent. Overuse of a rescue inhaler during a severe attack significantly increases the systemic dose and, consequently, the risk of more pronounced cardiac side effects, including irregular heart rhythms.
Long-Term Cardiovascular Effects of Uncontrolled Asthma
Beyond acute heart rate spikes caused by attacks and medications, chronic, poorly controlled asthma poses systemic risks to cardiovascular health over time. Asthma is characterized by persistent airway inflammation that is not confined to the lungs. This chronic inflammation can lead to systemic effects that strain the heart and blood vessels.
This inflammatory state has been linked to the development of atherosclerosis, which involves plaque buildup in the arteries. Individuals with persistent or uncontrolled asthma have shown higher levels of inflammatory biomarkers, suggesting a higher cardiovascular risk profile.
The long-term strain on the lungs and heart can also promote endothelial dysfunction and lead to conditions like pulmonary hypertension, where blood pressure in the arteries of the lungs becomes elevated.
Patients with asthma, particularly those with severe disease, face an increased risk for various cardiovascular events, including heart failure and atrial fibrillation. Furthermore, frequent use of oral corticosteroids (OCS) to manage severe exacerbations introduces additional cardiovascular risks. OCS use may lead to metabolic changes, such as dyslipidemia and diabetes, which contribute to vascular stiffness and hypertension.
Monitoring Heart Rate and When to Consult a Doctor
Monitoring heart rate is a practical way for individuals with asthma to assess the severity of an attack and their response to treatment. Heart rate can be checked manually or with devices such as pulse oximeters or smartwatches. A heart rate consistently above 110 beats per minute during an acute episode is classified as a sign of a severe asthma attack.
It is important to seek immediate medical attention if the heart rate remains persistently high, or if the heart rate does not slow down after using a rescue inhaler and breathing improves. A slow heart rate, or bradycardia, during a severe attack can be a late sign indicating respiratory failure and requiring emergency care.
You should prompt an emergency call if you experience:
- Severe palpitations or chest pain.
- Any irregular heart rhythm.
- Confusion.
- Severe sweating.
- A feeling of faintness.