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Effects of Early Myocardial Postnatal Maturation on Tolerance to Atrial Tachycardia With Altered Loading Conditions:
Etienne Fortin-Pellerin1, Nee S Khoo2,3, James Y Coe3
1Division of Neonatology, Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, QC, Canada.
Insights
Neonatal piglets tolerate rapid heart rates better than young piglets, especially with increased fluid volume. Post-natal maturation improves afterload tolerance but worsens tachycardia tolerance in piglets.
Area of Science:
- Cardiovascular Physiology
- Neonatal Physiology
- Pediatric Cardiology
Background:
- Post-natal myocardial maturation influences hemodynamic support needs.
- Understanding this transition is crucial for clinical management of neonates.
Purpose of the Study:
- To evaluate the impact of post-natal maturation on hemodynamic tolerance to tachycardia under altered loading conditions.
- To investigate the effects of hypervolemia and increased afterload on cardiac output in piglets of different ages.
Main Methods:
- Six groups of neonatal and young piglets underwent pacing to increase heart rate.
- Groups were subjected to tachycardia alone, tachycardia with hypervolemia, or tachycardia with increased afterload.
- Left ventricular output was measured using echocardiography.
Main Results:
- Neonatal piglets maintained cardiac output during tachycardia, unlike young piglets.
- Volume loading preserved cardiac output in both age groups during tachycardia.
- Increased afterload reduced cardiac output in neonatal piglets but not young piglets.
- A subset of neonatal piglets experienced desaturation due to right-to-left shunting at high heart rates.
Conclusions:
- Early post-natal maturation improves tolerance to increased afterload but reduces tolerance to tachycardia.
- Increasing intravascular volume can alleviate tachycardia's negative impact on cardiac output.
- Findings may inform strategies for optimizing cardiac output in early developmental stages.
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.
