Heart conditions can cause seizures, although the event is often a seizure-like episode known as convulsive syncope. A seizure is a sudden, uncontrolled surge of electrical activity within the brain, leading to temporary changes in movement, behavior, or consciousness. When the heart’s function is severely impaired, the resulting lack of blood flow to the brain can directly trigger this electrical disruption. It is important to distinguish these events from epilepsy, which involves recurrent seizures originating from a chronic brain disorder.
Cerebral Hypoxia and Seizure Activity
The immediate mechanism linking a heart problem to a seizure is a rapid, temporary reduction of blood flow to the brain, called cerebral hypoperfusion. This lack of adequate blood delivery quickly starves the brain tissue of oxygen, leading to cerebral hypoxia. The brain is highly dependent on a constant oxygen supply because it cannot store energy reserves. When oxygen levels drop below a certain threshold, brain cells experience energy failure, causing their electrical membranes to depolarize. This instability can trigger a brief, abnormal firing of neurons, resulting in a convulsive seizure.
A seizure-like event caused by this mechanism is most commonly diagnosed as convulsive syncope, a severe form of fainting. Syncope is a transient loss of consciousness caused by global cerebral hypoperfusion. If the period of low blood flow is prolonged or severe, the loss of consciousness may be accompanied by myoclonic jerks or brief, chaotic movements. These movements are not true epileptic seizures originating from the cortex, but rather a reflex response triggered deep within the brainstem by the lack of oxygen.
Cardiac Conditions That Reduce Blood Flow
Any heart condition that acutely compromises the heart’s ability to pump blood efficiently can lead to cerebral hypoperfusion and a seizure-like event. These conditions fall into two main categories: abnormal heart rhythm (arrhythmias) and structural or mechanical failure.
Arrhythmias
Both abnormally slow heart rates (bradycardia) and dangerously fast heart rates (tachycardia) can dramatically reduce cardiac output. For example, an episode of asystole (where the heart temporarily stops beating) or severe ventricular tachycardia prevents the heart chambers from properly filling, immediately cutting off blood supply to the brain. Conditions like severe sick sinus syndrome or complete heart block are bradyarrhythmias that cause neurological symptoms because the heart rate is too slow to maintain cerebral circulation.
Structural Issues
Structural issues also impede the heart’s pumping action, leading to insufficient blood flow. Severe aortic stenosis, a narrowing of the heart’s main outflow valve, physically obstructs the amount of blood that can leave the heart and reach the brain. Advanced congestive heart failure, particularly with a reduced ejection fraction, means the heart muscle is too weak to generate the necessary pressure to perfuse the brain. Acute conditions, such as a large pulmonary embolism, can also cause sudden right heart failure, leading to a rapid drop in overall cardiac output.
Differentiating Cardiac Seizures from Epilepsy
Accurately distinguishing convulsive syncope from an epileptic seizure is necessary for correct treatment. A key difference lies in the events preceding the episode, known as the prodrome or aura. Cardiac events are often preceded by presyncopal symptoms, such as dizziness, lightheadedness, warmth, or heart palpitations. In contrast, an epileptic seizure may be preceded by a specific aura, which is a focal neurological symptom like a strange smell or visual disturbance.
The duration and nature of the movements also provide important clues. Convulsive syncope is typically very brief, lasting only a few seconds, and movements often consist of just a few myoclonic jerks. Movements in convulsive syncope usually begin after the person has lost consciousness and fallen. Epileptic tonic-clonic seizures involve more sustained body stiffening followed by rhythmic jerking, and the loss of consciousness and movements occur almost simultaneously.
The most telling difference is the post-event state, or postictal phase. Following convulsive syncope, patients typically regain full consciousness and orientation very quickly, often within seconds. After a generalized epileptic seizure, the postictal period is usually prolonged, characterized by significant confusion, drowsiness, or exhaustion that can last for many minutes or hours. Cardiac-related events are also sometimes triggered by external factors like prolonged standing or emotional distress, which are less common triggers for unprovoked epileptic seizures.
Diagnosis and Preventing Future Events
The diagnostic process for a suspected cardiac-related seizure focuses on capturing the heart’s electrical activity during or immediately around the time of the event. The initial evaluation involves an electrocardiogram (ECG) to look for underlying rhythm or conduction abnormalities. If the initial ECG is normal, extended cardiac rhythm monitoring is employed using a Holter monitor or an implantable loop recorder to capture fleeting arrhythmias that may be responsible.
To definitively differentiate between a cardiac and a neurological cause, specialized testing combining both disciplines is often necessary. Video-EEG-ECG telemetry simultaneously records the brain’s electrical activity (EEG) and the heart’s rhythm (ECG), which is the gold standard for correlating the clinical event with its origin. Tilt Table Testing may also be used to provoke episodes of reflex syncope by changing the patient’s body position and observing the resulting drop in blood pressure and heart rate.
The most effective treatment for preventing future episodes of convulsive syncope is addressing the specific underlying heart condition. For patients with symptomatic bradycardia, implantation of a pacemaker can restore a reliable heart rhythm and adequate cardiac output to the brain. Arrhythmias like ventricular tachycardia may require antiarrhythmic medications or an implantable cardioverter-defibrillator (ICD). If a structural issue like severe aortic stenosis is the cause, surgical repair or valve replacement is the necessary intervention to restore proper blood flow.