A 69-year-old man presents to the emergency department with shortness of breath. The patient has presented 3 times this month with similar complaints. He states his shortness of breath started when he was walking from his car to a local restaurant. He does not see a primary care physician and is not currently taking any medications. He drinks alcohol socially and does not smoke. His temperature is 99.5°F (37.5°C), pulse is 100/min, blood pressure is 130/90 mmHg, respirations are 18/min, and oxygen saturation is 96% on room air. On physical exam, he appears fatigued and the cardiovascular exam reveals an additional heart sound after S2. A pulmonary exam is notable for bilateral crackles and an abdominal exam reveals an obese abdomen without pain in any of the quadrants. Lower extremity pitting edema is noted bilaterally. Which of the sets of lab values shown in Figure A would most likely be seen in this patient?
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A
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C
This patient is presenting with symptoms of heart failure (CHF). The most likely laboratory abnormalities are elevated brain natriuretic peptide (BNP), high anti-diuretic hormone (ADH), low sodium, and low potassium.

Heart failure is characterized by the decreased performance of the cardiac ventricles resulting in ventricular dilation. As the ventricles dilate, they release BNP as a marker of stretching of myocardial tissue. BNP levels can therefore serve as a marker of CHF. The kidneys will also have decreased perfusion levels in this disease leading to several key physiologic changes. First, is the activation of the renin-angiotensin-aldosterone system, which serves to increase perfusion to the kidneys by increasing blood pressure. This system achieves increased blood pressure by maintaining sodium and fluid retention at the expense of decreased potassium (hypokalemia) and decreased hydronium ions (metabolic alkalosis). In addition, ADH is also increased to further increase perfusion, resulting in water retention, hemodilution, and hyponatremia.

Ma et al. studied the correlation between BNP levels and cardiovascular outcomes. They found that patients with CHF and high levels of BNP had increased rates of cardiovascular complications. They recommend assessing BNP levels in patients who are suspected of having CHF.

Figure A is a chart with changes in brain natriuretic peptide, anti-diuretic hormone, sodium, and potassium that would be seen in various diseases.

Incorrect Answers:
Answer A: High BNP, high ADH, high sodium, and high potassium does not reflect the changes that would be seen in CHF. Though aldosterone serves to retain sodium, it also absorbs water. Thus, hypernatremia would not be seen. This pattern could be seen in patients with heart failure who have high free water losses such as after a burn or in desert environments.

Answer B: High BNP, low ADH, normal sodium, and low potassium does not reflect the appropriate increase in ADH and subsequent decrease in sodium that would be seen in CHF. Patients who have diabetes insipidus can have low ADH in this setting resulting in loss of free water.

Answer D: Low BNP, high ADH, low sodium, and low potassium does not reflect the finding of elevated BNP that is classically found in the dilated ventricles of CHF. This pattern would be seen in patients with the syndrome of inappropriate ADH where excessive resorption of free water results in hemodilution.

Answer E: Low BNP, low ADH, normal sodium, and normal potassium reflect the findings in a healthy patient. This patient most likely has CHF, which would result in increased aldosterone and ADH function.

Bullet Summary:
Common lab findings in heart failure include elevated BNP, elevated ADH, low sodium, and low potassium.