Anxiety or Panic Attack: This condition is characterized by an intense fear or discomfort that reaches a peak within minutes and includes symptoms such as palpitations, sweating, trembling, shortness of breath, feeling of choking, and chest discomfort or tightness. The symptoms presented closely align with those of a panic attack, making it a highly plausible diagnosis.

Hyperventilation Syndrome: Often associated with anxiety, this condition involves rapid and deep breathing, leading to symptoms like lightheadedness, palpitations, and chest tightness due to the reduction of carbon dioxide in the blood.
Dehydration or Electrolyte Imbalance: Dehydration and electrolyte imbalances, particularly potassium and magnesium deficiencies, can lead to palpitations, lightheadedness, and chest discomfort.
Mitral Valve Prolapse: A condition where the two valve flaps of the mitral valve do not close smoothly or evenly but instead bulge (prolapse) upward into the left atrium when the heart contracts. It can cause palpitations, chest discomfort, and lightheadedness.

Myocardial Infarction (Heart Attack): Although less likely in younger individuals without risk factors, a heart attack can present with chest tightness, palpitations, and lightheadedness. Missing this diagnosis can be fatal.
Pulmonary Embolism: A blockage of an artery in the lungs that can cause sudden and severe health problems, including chest pain, palpitations, and lightheadedness. It requires immediate medical attention.
Cardiac Arrhythmias (e.g., Atrial Fibrillation, Supraventricular Tachycardia): Abnormal heart rhythms that can lead to palpitations, lightheadedness, and chest discomfort. Some arrhythmias can be life-threatening if not treated promptly.
Hypertrophic Cardiomyopathy: A condition where the heart muscle becomes thickened, which can lead to obstructed blood flow and increase the risk of sudden cardiac death. Symptoms can include chest pain, palpitations, and lightheadedness.

Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of palpitations, sweating, headache, and chest pain due to the excessive release of adrenaline.
Hyperthyroidism: An overactive thyroid gland can lead to increased heart rate, palpitations, chest pain, and lightheadedness due to the excessive metabolic rate.
Cardiac Sarcoidosis: A condition where granulomas form in the heart, potentially disrupting its function and leading to arrhythmias, heart failure, and sudden death. It can present with nonspecific symptoms including palpitations and chest discomfort.