Disruption of the ventricular myocardial force-frequency relationship after cardiac surgery in children: noninvasive assessment by means of tissue Doppler imaging.

OBJECTIVE

Impaired ventricular function after cardiopulmonary bypass and surgical repair remains a commonly encountered clinical problem. We hypothesized that the well-described impairment of calcium cycling after cardiac surgery would significantly affect the ventricular myocardial force-frequency relationship, which can be measured noninvasively by using the tissue Doppler echocardiography-derived index of contractility isovolumic acceleration.

METHODS

Children undergoing repair of congenital heart defects were studied. Rate-related changes in contractility were measured by means of simultaneous atrial pacing and tissue Doppler echocardiography preoperatively and postoperatively.

RESULTS

Although closure of atrial septal defect did not affect ventricular myocardial systolic performance, closure of ventricular septal defect lead to a marked postoperative decrease of basal contractile force (2.0 +/- 0.7 m/s2 preoperatively vs 1.0 +/- 0.7 m/s2 postoperatively, P < .02). Furthermore, the force-frequency relationship curves were significantly different (P < .001), with a reduced force-rate trajectory, and also peak force was attained. Neonates undergoing the arterial switch procedure showed the most marked postoperative decrease of isovolumic acceleration at basal heart rates and force-frequency relationship with reduced trajectory and peak force development (P < .0001).

CONCLUSIONS

This is the first clinical study describing the noninvasive acquisition of ventricular force-frequency relationships in children undergoing operations for congenital heart disease. There is a marked variability in response, ranging from no effect in patients undergoing atrial septal defect closure to a profound reduction in myocardial contractile responses after neonatal arterial switch. This simple noninvasive method allows measurement of a hitherto rarely examined property of the myocardium, an understanding of which might allow refinement of myocardial protection and postoperative myocardial support.