Abstract
Post-natal maturation of the myocardium starts shortly after birth and could affect how clinicians should provide hemodynamic support during this transition. Our aim was to assess the impact of post-natal maturation on tolerance to tachycardia with altered loading condition in a piglet model.Methods: We report three series of experimentations. Six groups of landrace cross neonatal piglets (NP) (1–3 days) and young piglets (YP) (14–17 days) were assigned to tachycardia (NP, YP), tachycardia and hypervolemia (NPV, YPV) or tachycardia and increased afterload (NPA, YPA) groups (n = 7/group). Under anesthesia, a pressure catheter was placed in the left ventricle and pacing wire in the right atrium. NPV and YPV groups had 60 ml/kg of normal saline infused over 20 min. NPA and YPA had balloon sub-occlusion of the descending aorta. Heart rate was increased by 10 bpm increments to 300 bpm. Left ventricular output was measured by echocardiography.Results: NP maintained left ventricular output throughout the pacing protocol but it decreased in the YP (p < 0.001). With volume loading both NPV and YPV maintained their output with tachycardia. Although increased afterload resulted in reduced output during tachycardia in NPA (p = 0.005), there was no added impact on output in YPA. Interestingly, 4 of 7 NPV had significant desaturation at 300 bpm (baseline 99.7% vs. 300 bpm 87.9%, p = 0.04), associated with a right to left shunt through the patent foramen ovale which resolved immediately on cessation of pacing.Conclusions: Early post-natal maturation is associated with improved myocardial tolerance to increased afterload and poor tolerance of tachycardia, the latter of which may be alleviated by increasing intravascular volume. These data could translate into the development of better strategies to optimize cardiac output at these early development ages.
Highlights
MATERIALS AND METHODSStrategies for managing neonatal shock remain controversial and the impact of rapid early post-natal development underexplored
Using a piglet model of rapid atrial pacing, we previously demonstrated that tolerance to tachycardia decreases in the first few weeks [6], a finding associated with differences in the twist pattern of the left ventricle (LV)
Our finding of increased left ventricular output (LVO) with low grade tachycardia in the NP group is in accordance with early fetal studies [16] but is in contrast to a single neonatal study that employed a lamb model [17], using ventricular instead of atrial pacing
Summary
MATERIALS AND METHODSStrategies for managing neonatal shock remain controversial and the impact of rapid early post-natal development underexplored. What is currently understood of the developmental changes in myocardial function from birth has largely been influenced by observations from echocardiography [1]. These studies have suggested the neonatal heart has less robust diastolic function as some of the features of ventricular inflow and annular motion are similar to findings in adults with diastolic dysfunction [2]. Over the first few months of life, these features evolve in a way that suggests rapid improvement in diastolic function. Such studies have all been performed at rest. The effect of maturational changes on tolerance to combined hemodynamic stressors, a common occurrence in neonatal and pediatric intensive care, has not been sufficiently explored
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