Ventriculo‐arterial coupling in children with Still's murmur

Still's murmur is the most common innocent heart murmur in children and considered flow related; however, so far the cause of the murmur has not yet been fully explained. Assessment of the hemodynamic ventriculo-arterial interaction and the proportional anatomical dimensions of the left ventricle and the aortic root were the objective for this study. This case-control study was conducted at the Division of Pediatric Cardiology, Vienna Medical University, including healthy children with and without Still's murmur. To assess ventriculo-arterial interaction, the model of ventriculo-arterial coupling (VAC) was applied. The model describes the interaction between the left ventricle (left ventricular contractility, ELV) and the arterial system (effective arterial elastance, EA) by the VAC ratio EA/ELV. The parameters EA and ELV can be derived from M-mode echocardiography thereby allowing a noninvasive pressure-volume analysis. Outcomes comprised VAC ratio and diameters of both the aortic root (AOD) and the left ventricle in end diastole (LVED) and end systole (LVES) as well as their relative proportions, ejection fraction (EF), stroke volume (SV), blood pressure (BP), and heart rate (HR). Forty-three healthy children with Still's murmur (mean age 5.2 years) and 42 healthy children without murmur (mean age 5.8 years) participated in this study. Children with Still's murmur had a significantly lower VAC ratio EA/ELV (0.5 ± 0.13 vs. 0.59 ± 0.15; P < 0.005), a significantly higher EF% (67.1 ± 5.8 vs. 63.3 ± 5.6; P < 0.005, P < 0.01), and a larger SV per kg bodyweight (1.84 ± 0.33 vs. 1.68 ± 0.38; P < 0.05) than controls. BP, HR, and diameters of AOD, LVED, and LVES as well as their relative anatomic proportions did not differ between children with Still's murmur and controls. Still's murmur seems to be generated by a subtle alteration in ventriculo-arterial coupling in healthy children. This result can be translated to parents, as they may be informed that their child's innocent murmur is caused by a more "lively interplay between the heart and the aorta."