A 57-year-old man is admitted to the hospital because of acute shortness of breath shortly after a 12-hour automobile ride. Findings on physical examination are normal except for tachypnea and tachycardia. He does not have edema or popliteal tenderness. An electrocardiogram reveals sinus tachycardia but is otherwise normal. Which of the following statements is correct?
The clinical situation strongly suggests pulmonary embolism. In greater than 80% of cases, pulmonary emboli arise from thrombosis in the deep venous circulation (DVT) of the lower extremities, but a normal lower extremity Doppler does not exclude the diagnosis. DVTs often begin in the calf, where they rarely if ever cause clinically significant pulmonary embolic disease. However, thromboses that begin below the knee frequently “grow,” or propagate, above the knee; clots that dislodge from above the knee cause clinically significant pulmonary emboli. Untreated pulmonary embolism is associated with a 30% mortality rate. Interestingly, only about 50% of patients with DVT of the lower extremities have clinical findings of swelling, warmth, erythema, pain, or palpable “cord.” When a clot does dislodge from the deep venous system and travels into the pulmonary vasculature, the most common clinical findings are tachypnea and tachycardia; chest pain is less likely and usually indicates pulmonary infarction. The ABG is usually abnormal, and a high percentage of patients exhibit low P CO2 with respiratory alkalosis, and a widening of the alveolar-arterial oxygen gradient. The ECG usually shows sinus tachycardia, but atrial fibrillation, pseudoinfarction in the inferior leads, and acute right heart strain are also seen. Initial treatment for suspected pulmonary embolic disease includes prompt hospitalization and institution of intravenous heparin or therapeutic dose subcutaneous lowmolecular-weight heparin. It is particularly important to make an early diagnosis of pulmonary embolus, as intervention can decrease the mortality rate from 30% down to 5%. A normal D-dimer level helps exclude pulmonary embolus in the low-risk setting. This patient, however, has a high pretest probability of PE; further testing (CT pulmonary angiogram, V/Q lung scan) must be done to exclude this important diagnosis.
A 40-year-old woman has had increasing fatigue and shortness of breath for 6 months. Physical examination reveals normal vital signs and a resting O 2 saturation of 97%. Her lungs are clear without rales or wheezing. Cardiac examination shows a prominent pulmonary component of the second heart sound (P2 ) and a soft systolic murmur at the left sternal border that varies with respiration. Her neck veins show a prominent v wave. Chest x-ray shows right ventricular hypertrophy and enlargement of the central pulmonary arteries. What is the best next step in establishing a diagnosis in this patient?
This patient likely has primary pulmonary hypertension. Echocardiogram is a reliable noninvasive test to confirm the clinical suspicion. Once pulmonary hypertension is confirmed, secondary causes (pulmonary or congenital heart disease) should be ruled out. These are unlikely in this patient without clinical or radiographic evidence of chronic pulmonary disease. Once pulmonary hypertension is confirmed by echocardiography and secondary causes ruled out, patients often undergo right heart catheterization with measurement of pulmonary vascular resistance in response to various pulmonary vasodilators. Treatment choices have expanded in recent years; bosentan, sildenafil, and in severe cases, infused prostacyclin are effective treatments. In refractory cases, heart-lung transplantation (with its considerable risks) may be necessary. Spirometry is useful in defining obstructive or restrictive lung disease. Spirometry will be normal in pulmonary hypertension. Exercise stress testing in this patient will show a nonspecific decline in exercise tolerance; it is diagnostically useful when ischemic heart disease is a consideration. Measurement of alpha-1 antitrypsin would be indicated if this young woman had obstructive lung disease, but none of her clinical features point in this direction. If COPD were causing her symptoms, O2 desaturation or radiographic evidence of hyperexpansion would be expected.
A 65-year-old man with mild congestive heart failure is scheduled to receive total hip replacement. He has no other underlying diseases and no history of hypertension, recent surgery, or bleeding disorder. Which of the following is the best approach to prevention of pulmonary embolus in this patient?
Effective prophylaxis against DVT in the high-risk setting (eg, after major orthopedic surgery of the hip or knee) requires pharmacologic treatment with unfractionated heparin, low-molecular-weight heparin, fondaparinux, or therapeutic doses of warfarin. These treatments, when given at approved dosages and time intervals, decrease the risk of radiographic DVT by over 50%; dosage guidelines should be carefully followed. Aspirin alone is not effective in prevention of pulmonary embolus. Early ambulation, sequential compression devices, and elastic stockings provide some additional benefit, but are not adequate in themselves in this high-risk situation.
An obese 50-year-old woman complains of insomnia, daytime sleepiness, and fatigue. During a sleep study she is found to have recurrent episodes of arterial desaturation —about 30 events per hour—with evidence of obstructive apnea. Which of the following is the treatment of choice for this patient?
This patient with multiple episodes of desaturation has obstructive sleep apnea (OSA). In OSA, upper airway muscle tone decreases as the patient achieves deep stages (stages 3 and 4) of sleep; the soft palate falls against the base of the tongue, leading to obstruction of air flow and snoring. Microawakening occurs, leading to improvement in muscle tone but at the cost of shallow unrefreshing sleep. This leads to daytime somnolence (due to sleep deprivation), hypertension (due to hyperadrenergic state), and even cor pulmonale and chronic hypercarbia (due to hypoxia). At present fewer than five apneic episodes per hour are considered normal. The severity of sleep apnea is graded using the apnea/hypopnea index. Mild sleep apnea is 5 to 15 events per hour; moderate sleep apnea is 16 to 30; severe apnea is greater than 30 events per hour Continuous positive airway pressure is the recommended therapy. Weight loss is often helpful and should be recommended as well. However, weight loss alone will take significant time and may not be sufficient. Uvulopalatopharyngoplasty, when applied to unselected patients, is effective in less than 50%. A trial of CPAP is indicated before surgical therapy. Tracheostomy is a treatment of last resort in severe and refractory sleep apnea; it does provide immediate relief of the upper airway obstruction. Oxygen alone is less effective than CPAP.
A 30-year-old athlete presents to your office complaining of intermittent wheezing. This wheezing begins shortly after running. The patient admits to smoking 1 to 2 packs of cigarettes per day for 5 years. What finding would be consistent with asthma?
Asthma is an inflammatory process with reversible air-flow obstruction. This patient’s presentation suggests exercise-induced asthma. Asthma is an incompletely understood disease that involves the lower airways and results in bronchoconstriction and excess production of mucus. This, in turn, leads to increased airway resistance and occasionally respiratory failure and death. In any obstructive lung disease such as chronic obstructive pulmonary disease, hyperinflation may be present on chest x-ray and FEV1 may be decreased. Only in asthma is the airway obstruction fully reversible. Hypoxia would be unusual in exercise-induced asthma and would suggest an alternative diagnosis. Reduced forced vital capacity (FVC) characterizes restrictive lung disease, not obstructive (airways) disease. Dyspnea on assuming a supine position would suggest congestive heart failure.
Click to expand