WHY HAPPENS A PROGRESSIVE DECREASE OF BLOOD PRESSURE AFTER RENAL DENERVATION

Objective: Long-term follow-up data from the SYMPLICITY 3 trial (Bhatt et al, Lancet, 2022) and the Global Symplicty Register data (Mahfoud et al, JACC, 2020) show a further decrease in BP over time up to 3 years post procedure. Yet these observations lack a mechanistic explanation. A decrease in vascular resistance could possibly explain the observed phenomenon. Scanning Laser Doppler Flowmetry (SLDF) allows the non-invasive assessment of vascular resistance and capillary density by using the retinal vasculature as a mirror of the systemic circulation. Design and method: Retinal parameters were assessed using SLDF together with office and 24-hour ambulatory BP before and 6 as well as 12 months after renal denervation in 63 patients with treatment resistant hypertension (TRH) (NCT01687725). SLDF allows the assessment of retinal capillary flow (RCF), pulsed retinal capillary flow (systolic retinal capillary flow – diastolic retinal capillary flow) (pRCF), retinal vascular resistance, capillary area (CapA) and intercapillary distance (ICD). Results: Mean age of the study cohort was 60±11 years, mean BMI 30.6±4.9 kg/m2. Patients took 5.8 antihypertensive medications on average. There was a significant reduction of systolic and diastolic 24-hour ambulatory as well office BP 6 as well as 12 months after RDN (table 1). There was no significant reduction in the number of antihypertensive medications taken between baseline and 12 months after RDN (5.8vs.5.7 antihypertensive pills, p=0.159). Retinal vascular resistance was reduced 6 months after RDN (table 1), pRCF was reduced 6 as well as 12 months after RDN and capillary density improved 12 months after RDN. Conclusions: In high-risk patients with TRH endovascular RDN improved vascular resistance and reversed capillary rarefaction in the retinal circulation, a prognostic marker of further end-organ damage. The reduction of pRCF indicates a decrease of shear stress on the vascular wall by the pulsed blood flow. Increment of capillary density was observed not already 6 months, but only 12 months after RDN. We conclude that, improvement of capillary rarefaction happens slowly after RDN and requires long-term effective BP control and, that reduction in vascular resistance might explain the prolonged BP reduction after RDN.