title: Postnatal neonatal myocardial adaptation is associated with loss of tolerance to tachycardia: a simultaneous invasive and noninvasive assessment.
abstract: Doppler studies at rest suggest left ventricular (LV) diastolic function rapidly improves from the neonate to infant. Whether this translates to its response to hemodynamic challenges is uncertain. We sought to explore the impact of early LV maturation on its ability to tolerate atrial tachycardia. As tachycardia reduces filling time, we hypothesized that the neonatal LV would be less tolerant of atrial tachycardia. Landrace cross piglets of two age groups (1-3 days; NPs; 14-17 days, YPs; n = 7/group) were instrumented for an atrial pacing protocol (from 200 to 300 beats/min) and assessed by invasive monitoring and echocardiography. NPs maintained their LV output and blood pressure, whereas YPs did not. Although negative dP/dt in NPs at baseline was lower than that of YPs (-1,599 ± 83 vs. -2,470 ± 226 mmHg/s, respectively, P = 0.007), with increasing tachycardia negative dP/dt converged between groups and was not different. Both groups had similar preload reduction during tachycardia; however, NPs maintained shortening fraction while YPs decreased (NPs: 35.4 ± 1.4 vs. 31.8 ± 2.2%, P = 0.35; YPs: 31.4 ± 0.8 vs. 22.9 ± 0.8%, P < 0.001). Contractility measures did not differ between groups. Peak LV twist and untwisting rate also did not differ; however, NPs tended to augment LV twist through increased apical rotation and YPs through increasing basal rotation (P = 0.009). The NPs appear more tolerant of atrial tachycardia than the YPs. They have at least similar diastolic performance, enhanced systolic performance, and different LV twist mechanics, which may contribute to improved tachycardia tolerance of NPs.
authors.affiliation: Fetal and Neonatal Cardiology Program, Division of Cardiology, Women's and Children's Health Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada;
authors.forename: Etienne
authors.initials: E
authors.lastname: Fortin-Pellerin
authors.affiliation: Fetal and Neonatal Cardiology Program, Division of Cardiology, Women's and Children's Health Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada;
authors.forename: Nee S
authors.initials: NS
authors.lastname: Khoo
authors.affiliation: Fetal and Neonatal Cardiology Program, Division of Cardiology, Women's and Children's Health Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada;
authors.forename: Lindsay
authors.initials: L
authors.lastname: Mills
authors.affiliation: Fetal and Neonatal Cardiology Program, Division of Cardiology, Women's and Children's Health Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada;
authors.forename: James Y
authors.initials: JY
authors.lastname: Coe
authors.affiliation: School of Public Health, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Jesus
authors.initials: J
authors.lastname: Serrano-Lomelin
authors.affiliation: Division of Neonatology, Women's and Children's Health Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and.
authors.forename: Po-Yin
authors.initials: PY
authors.lastname: Cheung
authors.affiliation: Fetal and Neonatal Cardiology Program, Division of Cardiology, Women's and Children's Health Research Institute, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; lisa.hornberger@albertahealthservices.ca.
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Hornberger
mesh_terms: D000222:Adaptation, Physiological; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001696:Biomechanical Phenomena; D001794:Blood Pressure; D006328:Cardiac Catheterization; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D018619:Echocardiography, Doppler, Pulsed; D006339:Heart Rate; D009200:Myocardial Contraction; D013314:Stress, Mechanical; D013552:Swine; D013617:Tachycardia, Supraventricular / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control*; D013997:Time Factors; D016277:Ventricular Function, Left
keywords: diastole; echocardiography; neonatology; tachycardia; torsion