15: Dyspnea

CHIEF COMPLAINT

CONSTRUCTING A DIFFERENTIAL DIAGNOSIS

Heart disease, lung disease, and anemia are the most common causes of dyspnea. Neuromuscular disease and anxiety are less common causes. The simplest approach to the differential diagnosis is to consider the anatomical components of each of these systems. This allows us to develop a fairly comprehensive differential diagnosis of dyspnea.

Differential Diagnosis of Dyspnea

1. 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: Heart failure (HF)

      1. Systolic failure (coronary artery disease [CAD], hypertension, alcohol abuse)

      2. Diastolic failure (hypertension, aortic stenosis, hypertrophic cardiomyopathy)

   4. Coronary arteries (ischemia)

   5. Pericardium (tamponade, constrictive pericarditis)

2. Lung

   1. Alveoli

      1. Pulmonary edema (HF or acute respiratory distress syndrome)

      2. Pneumonia

   2. Airways

      1. Suprathoracic airways (ie, laryngeal edema)

      2. Intrathoracic airways

         • (1) Asthma

         • (2) Chronic obstructive pulmonary disease (COPD) (see Chapter 33, Wheezing & Stridor)

   3. Blood vessels

      1. Pulmonary emboli

      2. Primary pulmonary hypertension

   4. Pleural

      1. Pneumothorax

      2. Pleural effusions

         • (1) Transudative

           • (a) HF

           • (b) Cirrhosis

           • (c) Nephrotic syndrome

           • (d) Pulmonary embolism (PE)

         • (2) Exudative

           • (a) Tuberculosis

           • (b) Cancer

           • (c) Parapneumonic effusions

           • (d) Connective tissue diseases

           • (e) PE

   5. 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 [formerly Wegener granulomatosis])

      3. Infectious

3. Anemia

The extensive differential diagnosis for dyspnea necessitates a careful and detailed history, physical exam and review of basic laboratory examinations including chest film, ECG, and hematocrit. The history should detail the time course of the complaint, its severity, associated symptoms, and the patient’s past medical history. The physical exam should include vital signs, a detailed cardiac and pulmonary exam, and a search for signs suggestive of anemia (conjunctival pallor or palmar crease pallor). This process often suggests the diagnosis. However, when the diagnosis is not straightforward, certain pivotal findings can narrow the differential diagnosis and focus the diagnostic search (Figure 15-1). One such pivotal clue is fever. Fever is typically seen in pneumonia but could also be seen in asthma or COPD with concomitant infection. Less common causes of fever and dyspnea include valvular heart disease due to endocarditis, pulmonary emboli, acute respiratory distress syndrome, or interstitial lung disease. Chest pain (covered extensively in Chapter 9) is another pivotal clue in patients with dyspnea. Chest pain may be pleuritic or nonpleuritic and acute or chronic/recurrent. Each of these features can help focus the differential diagnosis (see Figure 15-1, Table 15-1). In brief, common causes of dyspnea and pleuritic chest pain are pneumonia, PE, pneumothorax, asthma, and COPD. On the other hand, many ...