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Selective heart rate inhibition improves single-ventricular stroke volume and efficiency in Fontan patients during exercise.

Research output: Contribution to journalArticle

Original languageEnglish
JournalJACC Cardiovascular Imaging
Accepted/In press17 Sep 2020

King's Authors

Abstract

Background: In patients with Fontan circulation stroke volume (SV) falls during exercise. We investigated if modifying the heart rate (HR) response using selective heart rate inhibition (sHRi) improves SV and cardiac function during exercise in these patients. Methods: 12 Fontan patients and 12 healthy controls underwent cardiac magnetic resonance imaging (CMR) during exercise to measure ventricular volumes, ventriculo-arterial (VA) coupling, ventricular mechanical and energetic efficiency (Meff and Eeff) and myocardial oxygen consumption per generated Liter cardiac output (MvO2CO). Fontan patients underwent a second exercise CMR during sHRi using ivabradine. Results: During exercise, mean ventricular filling rate was lower in Fontan patients compared to healthy volunteers (interaction p=0.01), resulting in a drop in end-diastolic volume (EDV), SV and a blunted increase in CO (all interaction p<0.01). VA-coupling, Meff and Eeff were lower in patients compared to volunteers, while MvO2CO was higher (all p≤0.01). sHRi in the Fontan patients increased diastolic time (p<.01), resulting in improved ventricular filling (mean EDV increase +5±1%, p<0.01–interaction p<0.01), SV (mean effect +10±2%, p<0.01–interaction p<0.01) and CO (mean effect +4±3%, p<0.04–interaction p=0.44) during exercise. sHRi also improved VA-coupling, Meff, Eeff and MvO2CO (all p≤0.01). Conclusion: In Fontan patients, ventricular filling is not sufficiently augmented to adapt to the increase in HR during exercise. sHRi increases diastolic time, hereby improving ventricular filling, SV, ventricular efficiency and CO. sHRi might be a potential new target for optimising cardiac function in these patients.

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