Left Ventricular Contractility in Extremely Premature Infants in the First Day and Response to Inotropes

Abstract

ABSTRACT:The aim was to assess myocardial contractility in infants born Ͻ30 wk gestation developing low systemic blood flow (SBF) in the first day, and the effect of dobutamine versus dopamine. Superior vena cava (SVC) flow was used as a measure of SBF at 3, 10, and 24 h (n ϭ 106). Infants with low SVC flow randomized to dopamine or dobutamine. Myocardial contractility was determined by the relationship between left ventricular (LV) mean velocity of circumferential fiber shortening (mVcfs) and wall stress. Infants who developed low SVC flow had significantly worse myocardial contractility at 3 h, but not 10 h. At 24 h, low-flow infants had lower than expected mVcfs for any given LV stress. In 37 infants randomized to inotrope, there was no significant difference in contractility at 10 g/kg/min. At 20 g/kg/min (n ϭ 21), dopamine increased whereas dobutamine decreased LV stress. Infants on dobutamine had significantly lower than expected mVcfs for any given LV stress compared with infants on dopamine. Contractility was not improved by either inotrope at either dose. In conclusion, infants developing low SVC flow in the first day have worse myocardial contractility at 3 h. Neither inotrope increased contractility, but dopamine increased LV stress at 20 g/kg/min. E xtremely preterm infants with low brain and upper body blood flow, as measured by SVC flow, in the first day are at increased risk of late peri/intraventricular hemorrhage (1,2), mortality, and subsequent neurodevelopmental impairment (3). Low SVC flow was associated with infants born at lower gestation, with a higher MAP in the first 12 h and a larger diameter DA at 5 h of age (1). Although infants with low SVC flow frequently had normal BP, they had significantly higher calculated UBVR compared with infants with normal flows. However, calculated vascular resistance is not a direct measure of LV afterload. LV stress is affected by LV dimensions, which are affected by preload, and LV wall thickness (4,5).Although LV shortening fraction has been reported to be reduced in shocked and acidotic preterm infants (6), this measure of LV performance does not take preload or afterload conditions into account and has been reported to be unreliable in preterm infants (7). In contrast, the relationship between LV mVcfs and LV wall stress (LV stress) has been used as a preload independent measure of LV contractility that takes into account afterload conditions. Myocardial contraction velocity will fall as afterload increases. A steeper negative slope of the regression line of the relationship indicates a more rapidly reducing mVcfs in response to increasing LV stress, or reduced myocardial contractility (4,8). Preterm infants have been documented to have reduced LV contractility in the first days after birth compared with term infants (9), although the relationship to low blood flow states has not been reported. In addition, the effects on myocardial contractility of commonly used inotropes in preterm infants have not been measured in infants with low flow in the firs...

Sex-Specific Differences in Peripheral Microvascular Blood Flow in Preterm Infants

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Acute hemodynamic effects of caffeine administration in premature infants

“…Previous studies describing the pharmacological effects of dopamine, dobutamine, milrinone, epinephrine or hydrocortisone have not shown consistent changes in the LVCO and SV. [9][10][11][12][13][14][15][16] Hydrocortisone, 9 commonly used to increase BP in infants unresponsive to dopamine, failed to increase LVCO significantly in a study of 15 hypotensive infants. The hemodynamic effect of dopamine has been examined in several studies: A trend of increasing RVCO, did not reach statistical significance, with significant increase of the shortening fraction in 8 hypotensive premature infants; 10 in 50 hypotensive patients treated with dopamine, LVCO dropped in 40, compared to 10 others in whom LVCO increased 11: BP did increase in the low LVCO group, with concomitant increase in the SVR.…”

Cardiac troponin T and N-terminal-pro-B type natriuretic peptide reflect myocardial function in preterm infants

“…It is determined by the following method: 13 mVcfs ¼ ðLVEDC À LVESCÞ Ä ðLVEDCÂEtcÞ where LVEDC ¼ LV end-diastolic circumference; LVESC ¼ LV endsystolic circumference and ETc ¼ LV ejection time corrected for heart rate (ET/ORR interval).…”