N-terminal proatrial natriuretic factor. An independent predictor of long-term prognosis after myocardial infarction

Neurohumoral measurements as indicators of long-term prognosis after acute myocardial infarction

The objective of this study was to evaluate the prognostic accuracy and usefulness of neurohumoral determination as a risk stratification tool after acute myocardial infarction (AMI) by comparing the long-term prognostic value of subacute neurohumoral measurements with other established indicators of adverse outcome. The study included 145 patients with documented AMI. During a median follow-up of 3.7 years, 30 cardiovascular and 6 noncardiovascular deaths occurred. By univariate analysis, plasma atrial natriuretic factor (ANF) and endothelin levels were strongly related to long-term cardiovascular mortality. In multivariate models, both peptides added prognostic information to that obtained from clinical evaluation, but not to that obtained from left ventricular ejection fraction (LVEF). Estimation of the area under the receiver-operating characteristic curve showed comparable prognostic accuracy for LVEF (0.7788), plasma ANF (0.7795), plasma endothelin (0.7493), and Killip classification (0.8203), meaning that for all these prognostic indicators, a randomly selected patient from the group of patients dying will have a test value larger than that of a randomly selected patient from the group of surviving patients 75% to 82% of the time. The clinical usefulness of neurohumoral determination in routine risk stratification after AMI appears to be limited since no additional prognostic information to that provided by objective evaluation of LV systolic function is obtained. However, in patients for whom objective assessment of LV performance is not readily available, measurement of plasma ANF and endothelin may be helpful in identifying asymptomatic patients at risk for cardiac death.

Plasma proatrial natriuretic factor (1-98) concentration after myocardial infarction: relation to indices of cardiac and renal function

OBJECTIVES

(a) To assess the relation between plasma concentrations of proatrial natriuretic factor (1-98) and non-invasively derived indices of left ventricular systolic and diastolic performance and (b) to assess the potential confounding effect of renal function and age on this relation in patients with acute myocardial infarction.

DESIGN

Cross sectional comparison of biochemical and echocardiographic indices of cardiac function.

SETTING

Norwegian central hospital.

PATIENTS

Sixty four patients with acute myocardial infarction.

MAIN OUTCOME MEASURES

Relation between plasma proatrial natriuretic factor (1-98) concentrations and echocardiographic indices of left ventricular systolic function as assessed by univariate and multivariate linear regression analysis. Sensitivity and specificity of plasma proatrial natriuretic factor (1-98) concentration as a measure of left ventricular systolic and diastolic dysfunction.

RESULTS

Plasma proatrial natriuretic factor (1-98) concentrations were significantly related to left ventricular ejection fraction (r = -0.33; P = 0.008), age (r = 0.43; P < 0.001), and creatinine clearance (r = - 0.53; P < 0.001). In a multivariate model left ventricular ejection fraction and creatinine clearance were both independently related to plasma values. The mean concentration of proatrial natriuretic factor (1-98) was significantly higher in patients with an ejection fraction of < 40% than in those with an ejection fraction of > or = 40% (1876 (1151) v 1174 (530) pmol/l; P = 0.03) and in patients with an abnormal transmitral E/A ratio ( < 0.65 or > 1.65, where E/A is ratio of peak early filling velocity to peak atrial component) compared with those with a normal ratio (1572 (895) v 1137 (523) pmol/l, respectively; P = 0.02). When patients were subdivided according to the median concentration of proatrial natriuretic factor (1192 pmol/l) the sensitivity and specificity were 89% and 56% respectively for detecting a left ventricular ejection fraction of < 40% and 75% and 61% respectively for detecting an abnormal E/A ratio. Concentrations below the median had a negative predictive value of 97% in excluding an ejection fraction of < 40% and of 84% in excluding an abnormal E/A ratio.

CONCLUSION

These results suggest that soon after myocardial infarction left ventricular ejection fraction and indices of renal function are independently related to plasma concentrations of proatrial natriuretic factor (1-98). Plasma concentrations of proatrial natriuretic factor (1-98) seem to reflect renal and cardiac performance rather than specific haemodynamic variables assessed by noninvasive methods. Plasma proatrial natriuretic factor (1-98) measurements may be a useful screening tool to identify patients with normal cardiac function soon after myocardial infarction.

Atrial natriuretic peptide and its potential role in pharmacotherapy

Atrial natriuretic peptide (ANP) is a 28 amino-acid polypeptide secreted into the blood by atrial myocytes after atrial pressure and distension. Although its role in humans is not clear, it can produce a variety of physiologic effects including vasodilatation, natriuresis, and suppression of the renin-angiotensin-aldosterone axis. These actions are potentially useful in a variety of pathologic states such as hypertension and congestive heart failure, and diverse methods to augment the effects of ANP in these states have been devised. The results are exciting and, despite some problems, may lead to the pharmacologic use of enhancement of ANP actions in several clinical disorders.