Asphyxia causes ultrasonographic D‐shaping of the left ventricle – an experimental porcine study

Abstract

The early and transient acute dilatation of the RV, coinciding with D-shaping of the LV and decrease in LV end-diastolic area seen in our study represent a combination of ultrasonographic characteristics normally attributed to pulmonary embolism. Early changes in ventricular chamber sizes and shape with septal flattening related to asphyxia can occur, but appear to be transient and disappear as circulatory collapse progresses, in an animal model. Despite this, asphyxia may represent a cause of ultrasonographic misinterpretation.

Effects of Progressive Hypoventilation on Left Ventricular Appearance: An Alternative Etiology of Acute Sonographic Short-Axis D-Shaping

“…We predefined an increase in the LV end‐diastolic eccentricity index (primary end point) from 1.0 to 1.3 to be the minimal increase of clinical relevance. Given this effect and standard deviations extracted from previously published data of 0.2 and 0.3, respectively, a nonparametric power analysis based on a before‐after situation showed a need for 9 piglets (α = .05; power = 0.8). To compensate for unforeseen sources of variation, we decided to include 10 piglets in the intervention group.…”

“…The LV area change was calculated as (LV end‐diastolic area – LV end‐systolic area)/LV end‐diastolic area and expressed as a percentage. Two inner diameters of the LV, perpendicular and parallel to the interventricular septum, were calipered at end diastole for derivation of the LV eccentricity index at both end diastole and end systole as previously explained in detail . All sonographic analyses were performed by a single observer and repeated by a second observer for calculation of interobserver variation.…”

“…13 The specificity of acute LV D-shaping has recently been challenged, showing that the LV eccentricity index, a sonographic index of D-shaping, 14 has an abrupt but transient increase with acute asphyxia. 15 However, acute asphyxia is rare in clinical practice, and decompensation of respiratory distress most often manifests itself as progressive hypoventilation. Progressive hypoventilation allows for circulatory compensatory mechanisms, which may influence LV filling and yield a different sonographic appearance.…”

When appearances deceive: Echocardiographic changes due to common chest pathology

“…In clinical settings, D‐shaping of the LV is often attributed to pulmonary embolism, as explained previously. However, Netzer's study and several porcine studies have shown that septal D‐shaping (Figure ) may occur as a response to hypoxic pulmonary vasoconstriction, with or without hypercapnia, as well. In these studies, RV dimensions normalized within minutes after re‐oxygenation.…”

“…Parasternal short‐axis views of an anesthetized, porcine heart at baseline (A) and after 90 s of asphyxia induced by ventilator respiratory hold (B). Flattening of the interventricular septum indicates an acute pressure increase in the right‐sided circulation LV = left ventricle; RV = right ventricle…”