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How do I determine the cause?

Constructing and Ranking a DDx


Figure 15-1.

A diagnostic approach to dyspnea.

The differential diagnosis of dyspnea is extraordinarily broad but following a structured and sequential approach to the patient with dyspnea can allow for the rapid identification of common and serious disorders while also ensuring that other causes are not missed. Heart disease and lung disease constitute the most common serious causes of dyspnea, specifically heart failure (HF), pneumonia, obstructive lung disease (chronic obstructive pulmonary disease [COPD] and asthma), and pulmonary embolism (PE). These four conditions should always be on the differential diagnosis for dyspnea and at the forefront of the clinician’s mind in evaluating the dyspneic patient. A series of other less common disorders represent an immediate risk to life and must also be considered in the very early stages of investigation, as urgent treatment may be necessary. These diagnoses can be remembered using the ACT ASAP mnemonic (Table 15-1).

Table 15-1.Common serious and life-threatening causes of dyspnea.

Once these common and life-threatening disorders have been considered, a more systematic approach to the many other causes of dyspnea can proceed. The simplest approach to constructing the broad differential diagnosis is to consider the anatomic components of each of these systems, specifically the route of inspired air and oxygen through the cardiopulmonary system and the rest of the body. This allows us to develop a fairly comprehensive differential diagnosis of dyspnea.

Differential Diagnosis of Dyspnea

  1. Lung

    1. Airways

      1. Suprathoracic airways (ie, laryngeal edema)

      2. Intrathoracic airways

        1. Asthma

        2. COPD (see Chapter 33, Wheezing and Stridor)

    2. Alveoli (can fill with water, pus, or blood)

      1. Pulmonary edema

        1. HF

        2. Acute respiratory distress syndrome

      2. Pneumonia

      3. Pulmonary hemorrhage

    3. Interstitium

      1. Edema

      2. Inflammatory

        1. Organic exposures (eg, hay, cotton, grain)

        2. Mineral exposures (eg, asbestos, silicon, coal)

        3. Idiopathic diseases (eg, sarcoidosis, scleroderma, systemic lupus erythematosus, granulomatosis with polyangiitis)

      3. Infectious (Pneumocystis)

      4. Malignancy (may occur in all areas on lung)

    4. Pleural

      1. Pneumothorax

      2. Pleural effusions

        1. Transudative

          1. HF

          2. Cirrhosis

          3. Nephrotic syndrome

        2. Exudative

          1. Tuberculosis

          2. Cancer

          3. Parapneumonic effusions

          4. Connective tissue diseases

          5. Hemothorax

    5. Blood vessels

      1. PE

      2. Primary pulmonary hypertension

  2. Heart

    1. Endocardium: Valvular heart disease (ie, aortic stenosis, aortic regurgitation, mitral regurgitation, and mitral stenosis)

    2. Conduction system

      1. Bradycardia (sick sinus syndrome, atrioventricular block)

      2. Tachycardia

        1. Atrial fibrillation and other supraventricular tachycardias

        2. Ventricular tachycardia

    3. Myocardium: HF

      1. Heart failure with reduced ejection fraction (HFrEF) (Secondary to coronary artery disease [CAD], hypertension, alcohol ...

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