Which diagnostic test best evaluates fluid volume overload in a patient with heart failure?

Fluid volume overload in heart failure results from impaired cardiac pumping ability, leading to increased venous pressures, pulmonary congestion, interstitial edema, and reduced gas exchange due to fluid accumulation in the alveolar and interstitial spaces. Rationale: A. An echocardiogram evaluates cardiac structure and function, including ejection fraction and valvular abnormalities. While essential in diagnosing heart failure, it does not directly assess pulmonary fluid overload or congestion severity. B. A CBC panel evaluates hemoglobin, hematocrit, and infection markers but does not directly measure fluid overload. Hemodilution may suggest fluid excess but is not specific or diagnostic for volume status. C. A chest X-ray is the best diagnostic tool for identifying fluid volume overload because it shows pulmonary vascular congestion, interstitial edema, and pleural effusions. These findings directly reflect excess intravascular and extravascular fluid in heart failure. D. An electrocardiogram assesses cardiac rhythm and electrical activity but does not evaluate fluid status or congestion. It is useful for identifying ischemia or arrhythmias but not volume overload.