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Mr. C is a 64-year-old man who comes to see you complaining of shortness of breath.

What is the differential diagnosis of dyspnea? How would you frame the differential?

Heart disease, lung disease, and anemia are the most common causes of dyspnea. The simplest approach to the differential diagnosis is to consider the anatomical components of each of these systems. This in turn allows us to deduce a fairly comprehensive differential diagnosis of dyspnea. (Occasionally, neuromuscular disease and anxiety also cause dyspnea.)

Differential Diagnosis of Dyspnea

  1. Heart

    1. Endocardium: Valvular heart disease (ie, aortic stenosis [AS], aortic regurgitation [AR], mitral regurgitation [MR], and mitral stenosis)

    1. Conduction system

      1. Bradycardia (sick sinus syndrome, atrioventricular block)

      1. Tachycardia

        1. Atrial fibrillation and other supraventricular tachycardias (SVTs)

        1. Ventricular tachycardia

    1. Myocardium: Heart failure (HF)

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

      1. Diastolic failure (hypertension, AS, hypertrophic cardiomyopathy)

    1. Coronary arteries (ischemia)

    1. Pericardium (tamponade, constrictive pericarditis)

  2. Lung

    1. Alveoli

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

      1. Pneumonia

    1. Airways

      1. Suprathoracic airways (ie, laryngeal edema)

      1. Intrathoracic airways

        1. Asthma

        1. Chronic obstructive pulmonary disease (COPD) (see Chapter 28, Wheezing and Stridor)

    1. Blood vessels

      1. Pulmonary emboli

      1. Primary pulmonary hypertension

    1. Pleural

      1. Pneumothorax

      1. Pleural effusions

        1. Transudative

          1. HF

          1. Cirrhosis

          1. Nephrotic syndrome

          1. Pulmonary embolism (PE)

        1. Exudative

          1. Tuberculosis

          1. Cancer

          1. Parapneumonic effusions

          1. Connective tissue diseases

          1. PE

    1. Interstitium

      1. Edema

      1. Inflammatory

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

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

        1. Idiopathic diseases (eg, sarcoidosis, scleroderma, systemic lupus erythematosus, Wegener granulomatosis)

      1. Infectious

  3. Anemia

Despite this long list, certain symptoms, signs, and historical features can give pivotal clues to the diagnosis. Features that suggest HF include a history of myocardial infarction, CAD risk factors, long—standing hypertension, or alcohol abuse. Further, an S3 gallop or jugular venous distention (JVD) are fingerprints for HF. Pulmonary embolism can be obvious or subtle and should be considered in patients taking exogenous estrogen and those with a history of cancer, recent immobilization, surgery, or leg swelling. A significant smoking history (≥ 20 pack years) raises the possibility of COPD. Wheezing—defined as a high-pitched sound on exhalation—suggests COPD or asthma, whereas stridor—defined as a high-pitched sound on inspiration—suggests upper airway obstruction. Menorrhagia or melena suggests anemia for which pale conjunctiva is virtually diagnostic. Fever and cough raise the possibility of pneumonia.

Certain tests are key in the evaluation of the patients with dyspnea. A chest radiograph, ECG and Hct are mandatory in the initial evaluation. In addition, echocardiography can reveal unsuspected HF or valvular heart disease. Pulmonary function tests can help determine whether the patient has obstructive, restrictive, or vascular lung disease (Table 14–1). Obstructive lung disease is characterized by decreased flows (forced expiratory volume in 1 second (FEV1) and the fraction of expired air in the first second (FEV1/FVC or [FEV1%]), restriction by decrease volumes (total lung capacity [TLC]) and pulmonary vascular disease by ...

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