Purpose: Renal sympathetic denervation (RDN) is again gaining interest as recent well-designed trials have demonstrated reduced ambulatory blood pressure (BP) after RDN. However, the hemodynamic mechanisms have not been elucidated. We aimed for the first time to investigate the effect of RDN on the "Hallmark of Hypertension" namely increased systemic vascular resistance index (SVRI).
Materials and methods: We investigated SVRI change in patients with true treatment-resistant hypertension randomised to RDN (n = 9) or drug adjusted control (n = 9). Treatment-resistant hypertension was defined as office systolic BP ≥ 140 mmHg despite ≥ 3 antihypertensive drugs including a diuretic. True treatment-resistant hypertension was confirmed prior to inclusion with ambulatory daytime systolic BP ≥ 135 mmHg immediately after witnessed intake of antihypertensive drugs. Hemodynamic variables were recorded with thoracic impedance cardiography at baseline and at three and six months follow-up after RDN. This non-invasive method also guided further tailoring of drug treatment in the control group aiming to normalise hemodynamic variables and BP.
Results: From three to six months follow-up after RDN, SVRI decreased with a median of -611 dyn*s*m2/cm5 [IQR -949 to -267] (p < 0.01), while supine mean BP decreased with a median of -11 mmHg [IQR -21 to -3] (p = 0.02). In the same period, SVRI in the control group was reduced with -674 dyn*s*m2/cm5 [IQR -1,309 to -340] (p < 0.01), while supine mean BP decreased with -15 mmHg [IQR -29 to -6] (p = 0.01). Thus, hemodynamic variables and BP in the two groups normalised in parallel.
Conclusion: Our data suggest that in patients with true treatment-resistant hypertension, renal sympathetic denervation lowers BP by reducing systemic vascular resistance of similar size as in the control group with careful individual selection of antihypertensive drugs and dose titration.
Keywords: Blood pressure; impedance cardiography; renal sympathetic denervation; systemic vascular resistance; treatment-resistant hypertension.