15 Microfon study – differences in the microcirculation in fontan adults compared to healthy controls; - preliminary results

Background and Aim Fontan palliation for functionally univentricular CHD carries long-term multiple organ sequelae and uncertain longevity in adulthood. The mechanisms behind these complications are incompletely understood but may not solely relate to systemic venous hypertension. We hypothesized that differences in the capillary microcirculation may play a role. Method We have so far evaluated the microcirculation in 10 adults (≥16 years) who underwent early childhood Fontan palliation and compared them with 11 healthy controls (≥16 years). Handheld Capillary Microscopy (HVCS, Exeter, UK) was used to assess the microcirculation in the hands, feet, nailfolds, and oral cavity. Basal and Maximal Capillary Density (BCD & MCD) were recorded & measured on the dorsum of the hand and feet after venous congestion according to a well-established protocol. Sitting and standing blood pressures were recorded as per British Hypertension Society guidelines. Central blood pressure, augmentation index, and pulse wave velocity were measured using Mobil-O-Graph® device (Stolberg, Germany). The independent 't' test was used for comparison of means among the groups using IBM-SPSS v26. Results The Fontan adults had statistically significantly lower basal (BCD-mean difference -18 capillaries/field, p = 0.001) and maximal capillary density (MCD-mean difference -23 capillaries/field, p = 0.001) on dorsum of the finger and of the feet (BCD - mean difference - 6 capillaries/field, p = 0.087; MCD-mean difference -12 capillaries/field, p = 0.012). Other findings include thickening of the capillaries, increased looping, distortion, and widening of venous limb of the capillary loop in the upper and lower extremities and buccal mucosa. Our Fontan patients also had significantly lower systolic BP (mean difference -12 mm Hg, p < 0.011), diastolic BP (mean difference -8 mm Hg, p < 0.001), and pulse wave velocity (mean difference -.73 milliseconds, p <0.016) compared to the healthy controls. There was no statistically significant difference in central blood pressure between both groups. Conclusions Our Fontan adults have significant structural capillary rarefaction and likely adverse remodeling of the microcirculation in their extremities compared to the healthy controls. Studies to examine this in other repaired CHD phenotypes are ongoing, Keywords Fontan Procedure, Microcirculation, Capillary Rarefaction, Central Blood Pressure Conflict of Interest None