Renal sympathetic denervation (RDN) was considered an effective alternative for patients whose blood pressure (BP) is not optimally controlled. The RDN works mainly by selectively disabling the nerves around the renal arteries and reducing blood pressure increase. However, despite the early success showed in the SYMPLICITY HTN-2 trial, the SYMPLICITY HTN-3 trial failed to demonstrate a significant BP reduction when compared to sham-control. incomplete disabling might result in inadequate denervation and were cited as some of the contributors to the nil result in the SYMPLICITY HTN-3 . The new generation of the Symplicity Spyral catheter aims to address some of these issues by altering the configuration of the catheter to allow better apposition to the renal arterial wall and increasing the numbers of electrodes to faciiitate more thorough ablations. However, the adequacy of sympathetic denervation with this new catheter can not be easily assessed at the time of the procedure as there is no simple physiological or biochemical feedbacks that can be monitored during the procedure. Blood pressure response by renal nerve simulation (RNS) during RDN procedure using the previous generation of the Symplicity Flex catheter have been reported to be potential parameter to assess the efficacy during the procedure and predict the BP response 6 months after RDN. The feasibility of RNS guided RDN procedure using the new generation of Symplicity Spyral catheter has not been reported. We therefore aim to explore the feasibility of RNS guided RDN with Symplicity Spyral Radiofrequency Catheter in patient with resistant hypertension.

Renal sympathetic denervation (RDN) was considered an effective alternative for patients whose blood pressure (BP) is not optimally controlled. The RDN works mainly by selectively disabling the nerves around the renal arteries and reducing blood pressure increase. However, despite the early success showed in the SYMPLICITY HTN-2 trial, the SYMPLICITY HTN-3 trial failed to demonstrate a significant BP reduction when compared to sham-control. incomplete disabling might result in inadequate denervation and were cited as some of the contributors to the nil result in the SYMPLICITY HTN-3 . The new generation of the Symplicity Spyral catheter aims to address some of these issues by altering the configuration of the catheter to allow better apposition to the renal arterial wall and increasing the numbers of electrodes to faciiitate more thorough ablations. However, the adequacy of sympathetic denervation with this new catheter can not be easily assessed at the time of the procedure as there is no simple physiological or biochemical feedbacks that can be monitored during the procedure. Blood pressure response by renal nerve simulation (RNS) during RDN procedure using the previous generation of the Symplicity Flex catheter have been reported to be potential parameter to assess the efficacy during the procedure and predict the BP response 6 months after RDN. The feasibility of RNS guided RDN procedure using the new generation of Symplicity Spyral catheter has not been reported. We therefore aim to explore the feasibility of RNS guided RDN with Symplicity Spyral Radiofrequency Catheter in patient with resistant hypertension.

Inclusion Criteria:

1. Age > 18 years
2. With resistant hypertension as defined by systolic BP over 140 mmHg on 24 hours ambulatory blood pressure measurement (ABPM)
3. Already on a stable dose of at least 3 anti-hypertensive drugs of different classes for 3 months.
4. subject is recruited for Transcatheter Renal Denervation

Exclusion Criteria:

1. Individual has undergone prior renal denervation.
2. Presence of renal artery stenosis >50%.
3. Main renal artery diameter <3mm and larger than 8mm by visual assessment on angiography.
4. Previous renal stenting.
5. Subject with Estimated GFR <30ml/min/1.73m2 as calculated using the MDRD formula.
6. Subject with renal transplant, single kidney, active nephritis or polycystic kidney disease.
7. Subject with known pheochromocytoma, Cushing's Syndrome (hypercortisolism), primary hyperaldosteronism, coarctation of the aorta, untreated hyperthyroidism, untreated hypothyroidism, or primary hyperparathyroidism.
8. Subject with unstable cardiac conditions such as myocardial infarction, unstable angina, malignant arrythmia, pulmonary embolism, significant valvular condition awaiting surgery or recent cerebrovascular accident within 3 months of recruitment.
9. Subject who is pregnant or planning for pregnancy during the study duration.
10. Subject who is enrolled in another device study for renal sympathetic denervation.

This is a feasibility study, small sample size serves as a proof of concept