What is renal denervation therapy?
Renal denervation is a minimally invasive, one-time procedure to disrupt the renal nerves. It does not involve a permanent implant and does not involve the risks of invasive surgery.
The first of its kind, the Medtronic Symplicity® renal denervation system consists of a flexible catheter and proprietary generator. In a procedure, similar to an angioplasty, the physician inserts the small, flexible Symplicity® catheter into the femoral artery in the upper thigh and threads it into the renal artery.
Once in place within the renal artery, the generator delivers a controlled, low-power radio-frequency (RF) energy to deactivate the surrounding renal nerves. This, in turn, reduces hyperactivation of the sympathetic nervous system, which is an established contributor to chronic hypertension (high blood pressure).
Recent studies have shown promising reductions in blood pressure amongst patients with treatment-resistant hypertension using renal denervation. This treatment may dramatically lower a patient’s cardiovascular risk, and may lead to some reductions in the need for anti-hypertensive medications.
How does it work?
The small, flexible Medtronic Symplicity™ catheter is inserted into the femoral artery in the upper thigh and threaded into the renal artery.
Once in place within the renal artery, the generator delivers a controlled, low-power radio-frequency (RF) energy to deactivate the surrounding renal nerves.
The step is performed four times to block the renal nerves.
RDN therapy reduces hyperactivation of the sympathetic nervous system, which is an established contributor to chronic hypertension.
The Medtronic system has been successfully used since 2007 to treat more than 5,000 patients with treatment-resistant hypertension worldwide. The procedure generally takes around 40-60 minutes. Most patients are discharged the same day.
What health condition does it treat?
Hypertension (high blood pressure) is the number one risk factor for premature death worldwide, accounting for more than half of all cardiovascular problems managed in primary care.
It is a common disorder where blood pressure remains abnormally elevated for a sustained period of time. Although there are often no symptoms, it is the number one risk factor for premature death worldwide. Approximately one-quarter of men and women attending general practice and over 40 per cent of those receiving treatment for hypertension, have blood pressure above recommended levels.
According to the Heart Foundation, there is a continuous relationship between blood pressure levels and the risk of cardiovascular disease (CVD), stroke, heart failure, pulmonary vein disease and kidney failure. Research shows incremental increases in blood pressure above normal levels are associated with a doubling of cardiovascular mortality over a 10 year period and that reducing systolic blood pressure by as little as 5 mmHg can reduce the risk of stroke by almost 30 per cent.
How many Australians are affected?
More than 6 million Australians have hypertension – a figure expected to grow to 6.4 million by 2051.
It is estimated that approximately 20 to 30 per cent of hypertensive patients meet criteria for treatment-resistance, meaning that despite treatment with three or more anti-hypertensive medications, their condition is uncontrolled.
Approximately 620,000 Australians have treatment-resistant hypertension. An ageing population coupled with increasing trends in obesity, sleep apnoea, and chronic kidney disease, mean the prevalence of treatment-resistant hypertension is anticipated to increase.
What is the consequence of not providing this therapy?
There have not been significant gains in the community control of hypertension since 2005.
Although pharmaceutical therapy plays a primary role in hypertension management, drugs alone are sometimes ineffective and approximately 50 per cent of treated patients have blood pressure that is uncontrolled. Further, approximately 50-75 per cent of patients with hypertension will not reach their blood pressure targets with a single drug, in which case combination therapy is advised.
Based on a study by Nelson et al, it is estimated 1,223,000 Australians received an average of 1.6 antihypertensive medications each under the PBS in 1998, costing the government $365.3m per year and consumers a further $110.9m through co-payments.
Approximately 62 per cent of cerebrovascular and 49 per cent of ischemic heart disease cases are attributed to poor blood pressure control. The annual global healthcare expenditure directly attributable to hypertension is estimated at $500 billion.
A patient's perspective
The first patient in the world to receive the therapy, Gael Lander from Victoria, was treated by Professor Rob Whitbourn at St Vincent’s Hospital, Melbourne in 2007.
For more than 30 years, 68 year-old Gael Lander struggled with high blood pressure that did not respond to the medications usually prescribed. Despite following all the rules – regular exercise, eating a low sodium diet, and taking anti-hypertensive medications – her systolic blood pressure was often in the 200mm/Hg range, double that of a person with a normal heart beat.
Gael describes her uncontrolled hypertension as if “someone had pushed the fast-forward button,” noting that ‘everything raced’, including her heart. Her blood pressure was always on her mind causing frequent anxiety. The increased cardiovascular risk associated with her hypertension was also a concern, as both her parents suffered from hypertension and had died of cardiovascular events.
Following lengthy discussions with Prof Murray Esler, her cardiologist at Baker IDI Heart and Diabetes Institute in Melbourne, Gael underwent renal denervation with the Symplicity® system. The procedure lasted less than one hour. Shortly following the procedure Gael saw an immediate reduction in her blood pressure. Her systolic blood pressure is currently 140 mm/Hg and her medications have been reduced.