Recognizing Symptoms and Emergency Red Flags

Living with Hereditary atrial tachyarrhythmia-infra-Hisian cardiac conduction disease means paying attention to two very different types of symptoms. Because your heart can struggle with being “too fast” and “too slow” at the same time, it is important to know which sensations are part of your baseline and which require immediate action.

The Symptoms of “Too Fast” (Atrial Tachyarrhythmia)

The “fast” part of your diagnosis usually starts in the top chambers of your heart (the atria). When these chambers race or quiver, you may feel:

• Palpitations: A sensation of your heart skipping a beat, thumping, or “flip-flopping” in your chest ^[1].
• Racing or Fluttering: A rapid heartbeat that may come and go suddenly ^[2].
• Exertional Fatigue: Feeling unusually tired or “out of gas” specifically when you try to move or exercise ^[3].

While these symptoms can be unsettling, they are often the more “visible” side of the condition. They occur because the top of the heart is electrically unstable ^[4].

The Symptoms of “Too Slow” (Infra-Hisian Block)

The “slow” part of your diagnosis is often more subtle. It happens when the “wiring” (the infra-Hisian pathways) deep in your heart conducts signals too slowly or fails to carry them to the bottom chambers ^[5]. This can cause:

• Persistent Fatigue: A deep sense of exhaustion that doesn’t go away with rest.
• Dizziness or Lightheadedness: Feeling “woozy” or unsteady, which may happen if your heart rate drops too low ^[6].
• Shortness of Breath: Feeling like you can’t get enough air, even when sitting still or doing light activity ^[7].

The “Silent” Diagnosis

It is important to know that you can have a pathogenic genetic variant without feeling any symptoms at all. In studies of certain high-risk genetic groups (like specific pediatric SCN5A cohorts), many individuals are asymptomatic (have no symptoms) when they are first diagnosed ^[8]. Even if you feel perfectly fine, electrical delays can develop over time ^[9]. This is why regular, individualized check-ups and ECGs are vital even when you feel healthy.

Emergency Red Flags: When to Seek Immediate Care

Some symptoms in this condition are not just “signs”—they are warnings that the heart’s electrical system is failing to maintain blood flow to the brain or body. If you or a loved one experience any of the following, call emergency services (such as 911) immediately.

• Syncope (Fainting) or Near-Fainting: A sudden loss of consciousness (fainting) is a major red flag ^[10]. It can mean your heart has paused due to a complete electrical block, or it could indicate a dangerous rhythm in the bottom chambers ^[11][12]. Presyncope (near-fainting) is also a very serious warning, especially if it happens during exercise or is accompanied by chest pain ^[6].
• Signs of a Stroke: Because atrial fibrillation can cause blood to pool and clot, stroke is a serious risk. Watch for sudden facial drooping, one-sided arm weakness, confusion, or difficulty speaking.
• Signs of Heart Failure: Seek emergency care for sudden, severe shortness of breath, an inability to breathe while lying flat, or rapid swelling in the legs and ankles ^[7][13].
• Signs of Cardiac Arrest: Sudden collapse, loss of pulse, and no breathing require immediate CPR and emergency intervention ^[12].
• Chest Pain or Tightness: Any new or severe chest pain, especially if combined with a racing heart or shortness of breath, requires an immediate evaluation ^[7].

When to Call Your Doctor Instead

If you notice a mild increase in palpitations, a slight change in your energy levels, or infrequent “fluttering” that resolves quickly, you should contact your cardiology team for a non-emergency appointment. They may want to adjust your medications or check your heart monitor data ^[14]. However, if those symptoms are accompanied by dizziness or happen while you are exercising, they move into a higher-risk category and need much faster attention based on your personalized action plan ^[10].