Multiple Sclerosis (MS) is a chronic condition where the immune system attacks the protective myelin sheath covering nerve fibers in the central nervous system. This damage interferes with communication between the brain and the body, causing symptoms like numbness, mobility issues, and fatigue. Although MS is primarily neurological, it can indirectly affect involuntary systems, including heart rhythm regulation, leading to heart palpitations. This occurs because the central nervous system’s regulatory centers are susceptible to the same inflammatory damage that characterizes MS.
Understanding the Autonomic Nervous System and Dysautonomia
The Autonomic Nervous System (ANS) is the body’s involuntary control center, regulating fundamental functions like breathing, digestion, body temperature, and heart rate. The ANS balances the sympathetic system (“fight or flight”) and the parasympathetic system (“rest and digest”). These systems are controlled by pathways running through the brainstem and spinal cord.
In MS, characteristic lesions (areas of demyelination and inflammation) can form in these central nervous system locations. Damage to nerve pathways in the brainstem or spinal cord disrupts the ANS signaling. This disruption leads to dysautonomia, meaning the system is no longer functioning correctly.
The resulting dysfunction causes an imbalance between sympathetic and parasympathetic influences on the heart and blood vessels. Studies suggest that up to two-thirds of people with MS experience some form of cardiac autonomic dysfunction. This damage is often associated with lesions in particular brain regions.
Cardiac Manifestations of MS-Related Dysautonomia
ANS damage manifests in the cardiovascular system as a failure to regulate heart rate and blood pressure, often resulting in palpitations. Palpitations are the conscious awareness of the heartbeat, which may feel like fluttering, pounding, or skipped beats. These sensations frequently result from a rapid heart rate (tachycardia) or an irregular heart rhythm (arrhythmia) caused by impaired nerve signaling.
A specific manifestation of cardiac dysautonomia is Postural Orthostatic Tachycardia Syndrome (POTS). This involves an abnormally large increase in heart rate when moving from lying to standing, as the body attempts to compensate for a sudden drop in blood pressure caused by faulty autonomic regulation. Orthostatic intolerance, including lightheadedness or dizziness upon standing, is reported in a significant number of MS patients and is closely tied to this dysfunction.
While tachycardia and irregular rhythms are more common, autonomic imbalance can also occasionally lead to bradycardia (a significantly slow heart rate). Erratic communication between the brain’s control centers and the heart muscle interferes with the heart’s natural pacemaker, leading to various rhythm disturbances and the sensation of palpitations.
Non-MS Factors Contributing to Palpitations
Heart palpitations are common and are not always directly attributable to MS-related nerve damage. Various coexisting factors frequently found in MS patients can trigger or worsen these sensations. High levels of psychological stress and anxiety, often associated with managing a chronic condition, can independently cause palpitations due to the release of stress hormones like adrenaline.
Certain medications used to manage MS can also have cardiac side effects. For instance, some disease-modifying therapies (DMTs), such as fingolimod, are known to temporarily affect heart rhythm and may cause a reduction in heart rate, requiring careful monitoring. High-dose intravenous corticosteroids, used to treat MS relapses, may also negatively impact cardiovascular autonomic function.
Severe fatigue, a hallmark symptom of MS, can contribute to heart rhythm issues by placing increased strain on the cardiovascular system. Underlying cardiac issues, such as hypertension or other forms of heart disease, may coexist with MS and be responsible for the palpitations. Awareness of these multiple potential causes is important for accurately determining the symptom’s source.
Diagnosis and Management Strategies
If a person with MS experiences new or worsening palpitations, they should seek medical attention, especially if accompanied by chest pain, shortness of breath, or fainting. Diagnosis begins by ruling out serious primary cardiac causes, typically involving an electrocardiogram (ECG or EKG) to record the heart’s electrical activity. Doctors may also use a Holter monitor, a portable device worn for one to two days, to capture the heart rhythm during daily activities.
To investigate dysautonomia, a physician may use specialized autonomic testing. This includes a tilt table test, which monitors heart rate and blood pressure changes as the patient moves from horizontal to vertical. Other tests, like heart rate variability measurements, assess the heart’s response to deep breathing. The Composite Autonomic Symptom Score (COMPASS-31) is a questionnaire used to subjectively assess autonomic symptoms.
Management strategies often focus on non-pharmacological adjustments to stabilize the autonomic system. Increasing fluid and salt intake helps manage symptoms related to blood pressure drops and orthostatic intolerance. Stress reduction and improved sleep hygiene are also beneficial for reducing anxiety-related cardiac symptoms. If medication is implicated, a physician may adjust the dosage of an MS therapy or prescribe medications like beta-blockers to regulate an abnormally fast heart rhythm.