Right and left ventricular mass development in early infancy: Correlation of electrocardiographic changes with echocardiographic measurements.

Right ventricular mass indexed to body surface area (RVMI) decreases and left ventricular mass index (LVMI) increases rapidly and substantially during early infancy. The relationship between these sizeable mass transformations and simultaneous electrocardiographic changes have not been previously delineated. Normal term infants (#45 initially enrolled) were prospectively evaluated at 2 days and at 2-week, 2-month, and 4-month clinic visits. Ventricular masses were estimated with 2D echocardiographic methods. QRS voltages were measured in leads V 1 , V 6 , I and aVF. Mean QRS axis shifted from 135 (95%CI 124, 146) to 65 degrees (95%CI 49, 81) and correlated with both RVMI decrease and LVMI increase (R = 0.46^⁎ vs. 0.25^†, respectively. * p < 0.01, ^† p < 0.05). As RVMI decreased from mean 28.1 (95%CI 27.1, 29.1) to 23.3 g/m2 (95%CI 21.4, 25.2) so did V 1 R and V 6 S voltages. RVMI changes correlated with V 1 R, V 6 S, and V 1 R + V 6 S voltages (R = 0.29*, 0.23† and 0.35*, respectively. * p < 0.01, †p < 0.05) but not with V 1 R/S ratio. As LVMI increased from 44.6 (95%CI 42.9, 46.3) to 55.4 g/m2 (95%CI 52.3, 58.5) V 6 R and V 6 Q increased but V 1 S voltage did not. LVMI changes correlated with V 6 R, V 6 R-S, and V 6 (Q + R)-S voltages (R = 0.31*, 0.34*, and 0.38* respectively. *p < 0.01) but not with V 1 S or V 6 R/S (R = 0.01 and 0.18 respectively, p = NS). Conclusions: During early infancy the RVMI decrease correlates best with the QRS axis shift and V 1 R + V 6 S voltage, and the LVMI increase correlates best with V 6 R-S and V 6 (Q + R)-S voltages • In early infancy indexed right ventricular mass decreases while the left increases. • Right ventricular mass index changes correlate best with the QRS axis shift. • Left ventricular mass index changes correlate best with V 6 (Q + R)-S voltage. • V 1 R/S voltage ratio does not correlate with right ventricular mass index. • V 1 S voltage and V 6 R/S voltage ratio do not correlate with left ventricular mass index. [ABSTRACT FROM AUTHOR]