The Fontan Dapagliflozin Pilot Study

Background:

The Fontan palliation is subject to progressive physiologic deterioration over time due to chronic elevation in central venous pressures (CVP), compromised cardiac output, and chronic lymphatic congestion and dysfunction. As a result, in adulthood Fontan patients have high rates of hospitalization of \~30% per year and nearly universally succumb to heart failure in the patients' 40s without heart transplant. Currently, there are no medical therapies of proven benefit in prolonging the lifespan of the Fontan palliation or in improving outcomes in Fontan patients.

Rationale:

Given the unusual physiologic stress established by the Fontan palliation, there is reason to believe that sodium-glucose cotransporter-2 (SGLT2) inhibitors might be uniquely beneficial in this small but growing patient population with an orphan disease process. SGLT2 inhibitors may be beneficial for the following reasons. a) Fontan patients are set up for cardiorenal syndrome. The severe end-organ congestion and increased total body water which characterizes Fontan failure are due to compromised cardiac output and chronically and uniquely elevated CVP. SGLT2 inhibitors appear to be uniquely beneficial in this setting based on findings from Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure (DAPA) trial, CANagliflozin cardioVascular Assessment Study (CANVAS) and Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients. Moreover, Griffin and Rao et al recently demonstrated the benefits of empagliflozin on renal sodium handling resulting in decreases in both plasma volume (which would be anticipated to decrease CVP) and total body water (which would be expected to decrease end-organ parenchymal edema and dysfunction). Based on similar mechanisms of action and similarly beneficial effects of dapagliflozin, the investigators anticipate that benefits will be b) Fontan patients who are overweight have a worse prognosis and SGLT2 inhibitors may facilitate modest weight loss. c) Activation of the Renin-Angiotensin-Aldosterone System (RAAS) has been implicated in the progression of Fontan circulatory deterioration, although clinical trials to investigate this hypothesis have not yielded positive results. In case the RAAS hypothesis is true, SGLT2 inhibitors should decrease renin tone by increasing sodium delivery to the macula densa. d) Fontan physiology frequently deteriorates as a result of progressively worsening ventricular systolic and diastolic function. Activation of inflammatory pathways and cardiac myocyte calcium overload have been implicated in this process in non-Fontan related heart failure, and likely play a role as well in Fontan-related heart failure. Putative anti-inflammatory effects and inhibition of the sodium/hydrogen transporter mediated by SGLT2 inhibition may therefore be of benefit in preventing progressive heart failure in Fontan palliated patients.