A 62-year-old male with a history of myocardial infarction presents to your primary care office with complaints of dyspnea on exertion and swollen feet and ankles. On exam, you note an elevated JVP and 2+ pitting edema of bilateral lower extremities. What is the most likely explanation for this patient’s lower extremity edema?
1.Increasing in capillary pressure
2.Decrease in plasma proteins
3.Increase in capillary permeability
4.increase in colloid osmotic pressure
5.increase in interstitial fluid pressure
summary
Given this patient’s history of myocardial infarction and findings on physical exam, his lower extremity edema is likely due to an increase in capillary pressure secondary to congestive heart failure. An increase in capillary pressure occurs in congestive heart failure as a result of increased plasma fluid volume backing up into the pulmonary and systemic circulations.
Starling forces determine fluid movement through capillary membranes. Net filtration pressure is dependent on the balance between the hydrostatic pressure gradient and the oncotic pressure gradient across the capillary. In heart failure, increased plasma fluid volume results in an increase in capillary pressure, thereby pushing fluid out of the capillaries and into the interstitium. There is a compensatory increase in lymphatic drainage in order to prevent the development of interstitial edema; however, as more fluid accumulates, this compensatory mechanism is overcome and overt peripheral edema develops.
King et al. review the diagnostic features and evaluation considerations in patients with heart failure. Patients most commonly present with decreased exercise tolerance with dyspnea, fatigue, generalized weakness, and fluid retention, with peripheral or abdominal swelling and possibly orthopnea. They highlight that the most important consideration when categorizing heart failure is whether left ventricular ejection fraction is preserved or reduced (less than 50 percent).
McMurray provides a review of the guidelines for recommended treatment in ambulatory patients with systolic heart failure. Pharmacologic agents include those that provide relief of symptoms only (i.e. diuretics) and those that also modify the course of the disease (i.e. ACE, ARB, beta-blocker). Furthermore, lifestyle changes, such as restriction of sodium intake are routinely recommended, although this recommendation is based on little evidence.
Illustration A summarizes the four Starling forces that determine fluid movement through capillary membranes.