Anxiety or Stress: Heart palpitations are a common symptom of anxiety and stress, which can cause an increase in heart rate and forceful heartbeats, leading to a sensation of palpitations.

Atrial Fibrillation: A type of irregular heartbeat that can cause palpitations, shortness of breath, and fatigue.
Mitral Valve Prolapse: A condition where the mitral valve does not close properly, leading to palpitations, chest pain, and shortness of breath.
Hyperthyroidism: An overactive thyroid gland can cause an increase in heart rate, leading to palpitations, weight loss, and heat intolerance.
Dehydration or Electrolyte Imbalance: Dehydration or an imbalance of essential electrolytes such as potassium, sodium, or magnesium can cause palpitations, fatigue, and muscle weakness.

Myocardial Infarction (Heart Attack): Although less common, a heart attack can cause palpitations, chest pain, and shortness of breath, and is a medical emergency.
Cardiac Tamponade: A condition where fluid accumulates in the sac surrounding the heart, leading to palpitations, chest pain, and shortness of breath, which can be life-threatening if not treated promptly.
Pulmonary Embolism: A blood clot in the lungs can cause palpitations, chest pain, and shortness of breath, and is a medical emergency.
Hypertrophic Cardiomyopathy: A condition where the heart muscle becomes thickened, leading to palpitations, chest pain, and shortness of breath, which can increase the risk of sudden cardiac death.

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): A rare condition where the heart muscle becomes replaced by fatty tissue, leading to palpitations, chest pain, and shortness of breath.
Long QT Syndrome: A rare genetic disorder that can cause palpitations, fainting, and sudden cardiac death.
Brugada Syndrome: A rare genetic disorder that can cause palpitations, fainting, and sudden cardiac death.
Pheochromocytoma: A rare tumor of the adrenal gland that can cause palpitations, high blood pressure, and sweating.