Do Elevated BNP Levels Predict Hemodynamically Significant PDAs
Condition: Patent Ductus Arteriosus
MeSH terms: Ductus Arteriosus, Patent
Study type: Observational

Summary: 
      The purpose of this study is to determine if B type natriuretic peptide (BNP) levels can be
      used to predict a hemodynamically significant patent ductus arteriosus (PDA). This peptide is
      produced by the ventricles in the heart when they are under stress, such as when a ductus
      remains open. If we can use a simple and inexpensive blood test to determine whether a PDA
      needs to be treated, we can potentially treat infants sooner than if they needed to wait for
      the availability of a cardiologist to perform an echocardiogram. This might decrease some of
      the deleterious effects of PDAs on the preterm infant such as bronchopulmonary dysplasia,
      necrotizing enterocolitis, renal hypoperfusion, and pulmonary hemorrhage. In a situation
      where follow up echocardiogram after a course of medical therapy shows persistent PDA, this
      test may help to decide whether this baby needs further treatment, either medical or
      surgical.
    

Detailed description: 
      B type natriuretic peptide (BNP) is mainly synthesized in the ventricles of the heart and
      released in response to volume and pressure loading and ventricular stress and, therefore,
      plays an important role in regulation of extracellular fluid volume. BNP causes diuresis,
      natriuresis, arterial and venous vasodilation and antagonizes the renin-angiotensin system
      resulting in a reduction in intravascular volume and decreased ventricular preload and
      afterload.

      In adults, BNP levels have been routinely used to diagnose and measure the degree of
      congestive heart failure. In healthy term infants, BNP levels are initially elevated in the
      first few days of life but then decline over the ensuing week after birth to near adult
      levels by 3 months of age. However, in premature newborn infants there are still no normative
      values for BNP and, therefore, no agreed-upon cut off points to diagnose ventricular overload
      without confirmatory echocardiography. Patent ductus arteriosus (PDA) is the most common
      cause of ventricular overload and congestive heart failure in premature neonates and can be a
      cause of significant morbidity. Excessive pulmonary blood flow due to the aortopulmonary
      shunting can result in increased ventilatory dependency and thereby contribute to chronic
      lung disease. Other possible sequelae from a PDA include renal hypoperfusion, necrotizing
      entercolitis, and pulmonary hemorrhage. Early closure of a PDA has been shown to reduce these
      risks.

      Delayed ductal closure is inversely related to GA at birth with the incidence varying from
      20% in babies greater than 32 weeks gestation and up to 60% in babies less than 28 weeks
      gestation. Currently, infants are screened for a PDA by echocardiography. This requires that
      centers have access to cardiologists to perform and analyze these studies. A simple blood
      test that could help diagnose a hemodynamically significant PDA would be extremely helpful in
      low birth weight infants, especially in more remote centers that do not have routine access
      to cardiology services. To date, there is no accepted blood test although numerous studies
      are emerging suggesting that BNP might be such a test. It has been shown that the magnitude
      of shunting through a PDA is a major determinant of BNP level, however, the levels published
      in various studies for what is hemodynamically significant varies greatly. In addition, the
      studies that have been done previously are on small sample sizes (less than 70 patients, with
      one retrospective study that had 88 patients) and on various gestational ages and, therefore,
      it is difficult to extrapolate normative data.

      It is already known that BNP levels are elevated in neonates with a hsPDA, however, there is
      little agreement on how high a BNP level needs to get to imply a hsPDA. We propose a study to
      measure the BNP values in all infants born less than 32 weeks gestation with and without a
      PDA. We will also do serial BNP levels with concurrent echocardiograms in infants with a PDA
      to determine a cutoff value of BNP above which an infant is likely to have a hsPDA. We hope
      that our study, with a larger sample size and on all infants with and without a PDA, will be
      able to not only gather more definitive data on what the cutoff BNP level is, but also gather
      normative BNP data on premature infants without PDAs.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Preterm infants between 24 0/7 weeks gestation and 31 6/7 weeks gestation.
      
Keywords: B type natriuretic peptide; Patent Ductus Arteriosus; Preterm infant