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Catheter-based Renal Artery Denervation for Resistant Hypertension

On 14th September 2011, Institut Jantung Negara became the first centre in Asia to perform a new technique of treating patients with Resistant Hypertension. The procedure is bilateral renal artery denervation using the Symplicity® Catheter system (Ardian).

Hypertension is defined as Blood Pressure of more than 140/90. The prevalence of hypertension increases with age and currently some 30-40% of the world’s adult population are hypertensive. Persistently elevated blood pressure is a major risk factor for stroke, heart disease and kidney failure. As such, the control and treatment is important, with current treatment options of lifestyle modification and pharmacotherapy, essentially lifelong.

However in some instances, Blood Pressure remains above target goals despite intensive therapy. While these patients are considered as uncontrolled hypertension due to various reasons like non-compliance to medications, White-coat hypertension or pseudohypertension, there are those that are truly resistant to treatment.

Resistant Hypertension is defined as Blood Pressure that remains above target goals despite taking 3 or more anti-hypertensive medications. They remain at risk of stroke and heart failure.
While the exact prevalence of Resistant Hypertension is unknown, a few large trials have indicated that it can be relatively common, accounting for 16-27% of study population.

The pathophysiology of hypertension is complex and not fully understood. But what we do know is that blood pressure control is achieved by the coordination of various systems in the body and the kidneys play a central role. The efferent and afferent sympathetic nerves to the kidneys lie along the inside wall of the renal arteries. The efferent sympathetic nerves terminates at the blood vessels, tubules and juxtaglomerular cells. Stimulation of these nerves will increase renin release, increase sodium reabsorption and decrease renal blood flow, all of which affects the Blood Pressure. The sensory afferent nerves provide communication from kidneys to the central nervous system. Its activity directly influences sympathetic outflow to the kidneys, heart and peripheral blood vessels.

The stimulation and hyperactivity of the renal sympathetic system is thought to be responsible for a major part of hypertension. It has been shown that denervation of the nerves surgically can prevent or reverse hypertension.

A device-based, percutaneous approach of selectively denervating the renal sympathetic nerves using Radiofrequency Ablation, the Symplicity® Catheter system was developed by Ardian for this very reason (Picture 1, courtesy of Ardian Medtronic).

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As there is no immediate change in blood pressure post procedure, our current endpoint is achieving 4-6 “good” ablations in each artery. It is a relatively simple procedure. The total procedure time is usually less than 1 hour. As it can be painful and uncomfortable for the patient during the ablation, we routinely administer sedation

Presently, the data on safety and efficacy comes from published studies and reports.

In the Symplicity HTN-2 study, 106 patients with Resistant Hypertension, from 24 centres in Australia, Europe and New Zealand, were randomized to either medical therapy or RDN. At 6 months follow up, the mean blood pressure reduced by 32/12mmHg in patients who underwent RDN. No serious procedural complications occurred and renal function remained the same at follow up.

In IJN, we started a Resistant Hypertension clinic together with Professor Abdul Rashid from Cyberjaya University of Medical Sciences (CUCMS), to screen and review all patients with uncontrolled hypertension. Those with true Resistant Hypertension, meeting a set of criteria will be offered RDN. The IJN foundation has graciously donated 30 sets of Symplicity catheters for us to start off the procedure and we are offering these free of charge for Malaysian patients meeting the criteria.

Currently, RDN is offered only to patients with Resistant Hypertension. The data so far have been very promising, with good safety and efficacy. With larger trials, we will be able to assess if this procedure is also suitable for a larger population of Hypertensive patients.

Other than in hypertensive states, renal sympathetic hyperactivity has also been noted in heart failure, chronic renal disease, insulin resistance, and obstructive sleep apnea and hepatorenal syndromes. RDN may also be of some application to these. Studies looking at effectiveness of RDN in these conditions is currently ongoing.

Are there any potential downsides? Yes, both in safety and efficacy. We do not have data much longer than 2 years. Also, the possibility of nerve regeneration, especially efferent nerves is a possibility that have been demonstrated in renal and heart transplant models, raising the question of how long the blood pressure benefits will last. Current data from pilot studies up to 24 months suggest that the blood pressure reduction remains, but longer term follow up will tell us more. Cost is also a big consideration.

IJN BREAK THROUGH

Catheter based selective renal artery denervation is a new therapy that is being offered in IJN for patients with Resistant Hypertension. It is a simple and safe procedure. The current data is very promising. There are also potentials for larger applications. In the meantime, bigger studies and longer follow up are being planned and anticipated.

IJN EXPERIENCE AND TRACK RECORD

Up to December 2013, we have performed 29 Renal Denervation procedures. There were no complications. In the clinical studies, the benefits were only seen some 6 months after the procedure.

THE DOCTORS WHO PERFORMED THE PROCEDURE

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