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J Thorac Cardiovasc Surg 2006;131:625-631
© 2006 The American Association for Thoracic Surgery

Surgery for Congenital Heart Disease

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

^a Division of Cardiology, Hospital for Sick Children, Toronto, Ontario, Canada
^b Kinderherz-Praxis, Munich, Germany

Received for publication July 4, 2005; revisions received September 8, 2005; accepted for publication September 15, 2005.

^_* Address for reprints: Andrew Redington, MD, FRCP, Head, Division of Cardiology, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario M5G 1X8, Canada. (Email: andrew.redington{at}sickkids.ca).

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.

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