Congestive Heart Failure (Part 2) – Labs

Category: Uncategorized.

Read part 1 here

Laboratory Findings

  • Blood Count
    • Blood count may show anemia. Poor prognosis.
    • High red cell distribution width (RDW). Poor prognosis.
  • Kidney functions may show reduced renal perfusion.
  • Electrolytes
    • Hypokalemia (risk of arrhythmias)
    • Hyperkalemia (limits the use of ATN inhibitors.) Poor prognosis.
  • Thyroid Function Tests
    • Occult thyrotoxicosis
    • Myxedema
  • Iron Studies
    • Figure out hemochromatosis

Presence of the chronic kidney disease (CKD) limits the treatment options.

Need for Biopsy

In unexplained cases cardiac biopsy can be performed. It can help figure out conditions like amyloidosis. Keep in mind, however, that the biopsy will be more helpful to rule out than to diagnose a cause of the heart failure.

Labs to help differentiate between the dyspnea due to the heart failure vs non-cardiac causes:

Serum BNP is produced in the ventricles. It elevates when the filling pressure in the ventricle is high. It is less specific in women, older patients, and COPD patients.

Acute Setting

In the emergency room triage to diagnose acute decompensated heart failure serum BNP less than 100 ph/mL or NT-proBNP less than 300 pg/mL with normal ECG makes heart failure unlikely.

Chronic Setting

BNP in chronic patients is less sensitive and specific; and hence less useful. One utility in the chronic setting is to assess worsening breathlessness and/or weight gain with increased BNP can help prompt you to increase the dose for diuretics. This is not yet added to the practice guidelines. (2016)

ECG Changes

  • May show arrhythmias secondary to the heart failure
  • MI may be detected with conduction defect changes (if any)

Chest X-Ray

  • Cardiomegaly is an important finding. Poor prognosis.
  • Signs indicating pulmonary venous hypertension may be observed. These include dilation of the upper lobe veins, and hazy vessel outlines due to perivascular edema resulting from the hypertension.
  • Interstitial edema
  • Alveolar fluid


Considering that most patients of heart failure will have abnormalities of the EKG, Chest X-Ray, and serum studies, clinically the pressing need is to figure out the LV failure and the type of the failure (systolic vs diastolic).

Echocardiogram can be the most useful to identify the LV function and state. As you may know, echocardiogram will provide information about the size and function of each cardiac chamber. It will also show pericardia effusion, valvular defects, any intracardiac shunts, and most importantly segmental wall motion abnormality – which in turn helps you identify an old MI.

Is Catheterization Indicated/Useful?

Most of the times the non-invasive studies above should provide you sufficient information to manage the patient. In some cases the state of coronary artery disease (CAD) may be needed. In such cases an LV catheterization maybe done.

Patients not responding to standard therapy may need right heart catheterization to choose and to monitor therapy.


Management will be the next topic.


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