Is Total Isovolumic Time Useful for Assessing Ventricular Function in the Fontan Patient?

Background: Echocardiographic evaluation of ventricular function is paramount in routine follow up of Fontan patients. Yet function of the single right ventricle (sRV) is mostly assessed semi-quantitively by eyeballing. We therefore evaluated whether total isovolumic time (t-IVT), a sensitive marker of left ventricular systolic-diastolic interaction that is easily computable only from the time intervals of the cardiac cycle from Doppler tracings, qualifies as a marker of sRV function.

Methods: We performed a retrospective analysis of echocardiography and cardiac magnetic resonance (CMR) studies of 47 Fontan patients with a sRV. t-IVT is the time of the cardiac cycle when the ventricle is neither filling nor ejecting. It is expressed in seconds per minute and was calculated as follows: t-IVT = 60 − (t-ET + t-FT), where t-ET and t-FT represent total ejection and filling times, respectively. Median time interval between studies was 8 ± 3 years. tIVT was correlated with contemporary markers of systolic and diastolic ventricular function from echocardiography and CMR.

Results: Only global longitudinal strain (GLS) from echocardiography suggested a decline in sRV function (−18.1 ± 3.8% vs. 16.0 ± 3.9%, p < 0,01) whereas t-IVT, e/E’ and sRV-EF from CMR remained unchanged during follow up (t-IVT: 11.0 ± 2.3 vs. 11.1 ± 2.0 second min, p = 0.7; e/E’: 10.5 ± 4.6 vs. 9.7 ± 4.3, p = 0.6; 56.0 ± 8.4 vs. 50.7 ± 10.0%, p = 0.1). t-IVT correlated closely with sRV-EF (r = −0.723, p < 0.0001) but not with GLS and e/E´.

Conclusion: Its close correlation with sRV-EF suggests that t-IVT is a useful marker to monitor systolic function of the systemic RV during follow up of Fontan patients and can therefore be considered a helpful adjunct to routine echocardiographic assessment. The simplicity of its measurement makes t-IVT especially attractive for clinical use. Global longitudinal strain seems a particularly sensitive parameter to detect changes in sRV function.

Publication History

Article published online:
13 February 2024