From the Guidelines
Atrial Natriuretic Peptide (ANP) testing should be considered primarily in patients with suspected heart failure, volume overload states, or when evaluating for cardiac dysfunction, as indicated by the most recent and highest quality study 1.
Clinical Scenarios for ANP Testing
The test is most useful when clinical assessment of volume status is challenging, such as in patients with:
- Obesity
- Concurrent pulmonary disease
- Diagnostic uncertainty between cardiac and non-cardiac causes of dyspnea Specific clinical scenarios warranting ANP testing include:
- Acute shortness of breath with unclear etiology
- Monitoring of heart failure treatment efficacy
- Risk stratification in patients with established heart failure
- Evaluation of volume status in patients with renal dysfunction
Rationale for ANP Testing
ANP is a hormone released by cardiac atrial cells in response to stretching from increased blood volume, functioning as a natural diuretic that promotes sodium and water excretion while inhibiting the renin-angiotensin-aldosterone system. Elevated ANP levels typically indicate cardiac stress and volume overload. However, B-type Natriuretic Peptide (BNP) or NT-proBNP are more commonly used in clinical practice due to their greater stability and established diagnostic thresholds, making ANP testing relatively less common in routine clinical settings 1.
Diagnostic Accuracy of Natriuretic Peptides
The diagnostic accuracy of natriuretic peptides in heart failure has been evaluated in several studies, including a systematic review and diagnostic meta-analysis in the acute care setting 1. The results show that both B-type natriuretic peptide and N-terminal probrain natriuretic peptide (NTproBNP) have excellent ability to exclude the diagnosis of acute heart failure at their respective lower cut-off thresholds. However, the sensitivity of these peptides for the diagnosis of acute heart failure at thresholds above this lower cut-off is only modest, and specificity is also relatively low, thus confirmatory testing by cardiac imaging is required 1.
From the Research
When to Test for Atrial Natriuretic Peptide (ANP)
- Testing for ANP can be useful in the diagnostic evaluation of heart failure (HF) 2, 3, 4, 5.
- ANP levels can serve as a potential biomarker for the diagnosis of acute stages of heart failure 5.
- The measurement of plasma ANP, specifically its metabolite mid-regional pro-ANP, has similar diagnostic and prognostic value to brain natriuretic peptide (BNP) 4.
- ANP testing may provide incremental diagnostic value when BNP levels fall into "grey zone" levels 4.
- Patients with heart failure with preserved ejection fraction (HFpEF) may have lower ANP levels and a greater diuretic effect of exogenous ANP, making them a promising therapeutic target for modulating circulating ANP 6.
Clinical Conditions Associated with ANP Levels
- Dilated cardiomyopathy: associated with increased ANP levels 5.
- Renal failure: associated with decreased ANP levels 5.
- Aging: associated with decreased ANP levels 5.
- Heart failure with preserved ejection fraction (HFpEF): associated with lower ANP levels 6.
Diagnostic and Therapeutic Implications
- ANP has cardioprotective effects, including diuretic/natriuretic actions, vasodilatory actions, and inhibition of aldosterone secretion 3.
- Exogenous ANP may be a logical treatment for HF patients with ANP deficiency, particularly those with HFpEF 6.
- The efficacy of exogenous ANP (carperitide) has been evaluated in patients with acute HF, showing a greater diuretic effect in patients with HFpEF 6.