Differential Diagnosis for New Onset of Tachycardia with Shortness of Breath

Single Most Likely Diagnosis

• Anxiety or Panic Attack: This is often the most common cause of new onset tachycardia and shortness of breath, especially in the absence of other symptoms. The body's "fight or flight" response can lead to rapid heart rate and respiratory distress.

Other Likely Diagnoses

• Asthma or Chronic Obstructive Pulmonary Disease (COPD) Exacerbation: Both conditions can cause shortness of breath and may lead to tachycardia due to hypoxia or increased respiratory effort.
• Pneumonia: An infection in the lungs can cause both tachycardia and shortness of breath, especially if the pneumonia is severe or the patient has underlying health conditions.
• Pulmonary Embolism (PE): While not as common as other diagnoses, PE can cause sudden onset of tachycardia and shortness of breath, especially if the clot is large.
• Cardiac Conditions (e.g., Heart Failure, Myocardial Infarction): Various heart conditions can lead to both symptoms, either through direct effects on the heart or through secondary effects like pulmonary edema.

Do Not Miss Diagnoses

• Pulmonary Embolism (PE): Although mentioned earlier, it's crucial to emphasize PE as a "do not miss" diagnosis due to its high mortality rate if untreated.
• Cardiac Tamponade: A life-threatening condition where fluid accumulates in the sac around the heart, impeding its ability to pump blood effectively.
• Tension Pneumothorax: A condition where air enters the space between the lungs and chest wall, leading to a collapse of the lung, which can cause both tachycardia and severe shortness of breath.
• Hypertensive Emergency: Severe high blood pressure can lead to heart failure, stroke, or other emergencies, presenting with tachycardia and shortness of breath among other symptoms.

Rare Diagnoses

• Thyroid Storm: A life-threatening complication of untreated or undertreated hyperthyroidism, which can cause tachycardia, shortness of breath, and other systemic symptoms.
• Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of severe hypertension, tachycardia, and other symptoms due to excessive catecholamine release.
• Neurogenic Pulmonary Edema: A rare condition often associated with severe central nervous system injuries or conditions, leading to pulmonary edema without heart failure, which can present with tachycardia and shortness of breath.