Professor Carlo Di Mario explains how a breakthrough technique - renal denervation - is used to help patients whose hypertension is resistant to drugs.
Hypertension is a silent killer
A sedentary lifestyle, poor diet and obesity, ageing and stress all contribute to the increasing incidence of hypertension, also known as high blood pressure.
In the UK alone, almost 12 million people each year are treated for hypertension. Probably many more are unaware of the presence of this ‘silent killer’.
Although regular blood pressure testing, which takes only a few moments, can help to identify hypertension in its early stages, often patients do not visit their doctor until it is too late. By then, their heart is already thickened or enlarged; their coronary, carotid or peripheral arteries are narrowed; their aorta is dilated; or they have suffered a stroke.
Patients should not be overly concerned if they have a blood pressure higher than the ideal values of 135/85 mmHg, in one test taken by their doctor. It might be what we call ‘white coat hypertension’, where the blood pressure is slightly raised due to fear or nervousness of doctors. One elevated measurement is not enough to start prescribing drugs.
The most reliable method to ensure that the hypertension is real and needs treatment is to perform repeat blood pressure measurements over 24 hours. This is a method now also strongly recommended by the National Institute for Health and Care Excellence (NICE).
Treatment for hypertension
Once it is established that the hypertension is real, NICE recommends starting treatment with drugs called calcium antagonists or ACE-inhibitors. In some cases, depending on the reason for the hypertension, we may start with other drugs called beta-blockers or diuretics.
Often the use of small-to-moderate doses of two or more drugs in combination work better than using a high dose of a single drug alone, which may increase side effects without increasing benefits. Sometimes even a combination of drugs is not sufficient to lower the blood pressure within the desired limits.
Occasionally we have discovered with blood or urine tests and imaging of the patient’s kidneys and surrenal glands that there are relatively rare diseases causing the hypertension. Most often, however, these tests are negative and we are left with a resistant hypertension, uncontrolled or poorly controlled, continuing to damage the heart.
Helping patients with breakthrough renal denervation therapy
For some patients whose hypertension is resistant to drugs, we can now use a breakthrough technique called renal denervation. This technique is based on the observation that in hypertensive patients, the sympathetic nervous system of the kidneys is overactive, causing the blood vessels to narrow, which in turn, increases blood pressure.
The technique is simple and requires few preliminary tests and just a one-day stay in hospital. A catheter is inserted under local anaesthesia into the femoral artery in the groin and pushed inside the two renal arteries supplying the kidneys. Then, the nerves that go to and from the kidneys are given four to six bursts of radiofrequency current, which reduces the nerve activity and consequently reduces blood pressure.
During the two minutes of radiofrequency discharge, there is some pain in the belly, which is managed with strong intravenous sedatives.
Success rates of renal denervation therapy
The method is very safe and works in more than 90 per cent of cases, with an initial reduction of blood pressure that improves progressively in the first six to 12 months after treatment.
Recent data from a well-conducted randomised trial has shown that the improvement is persistent and blood pressure is reduced by more than 10mmHg up to four years after initial treatment.
Eligibility for renal denervation therapy
To plan the denervation procedure, suitable patients undergo a simple non-invasive radiological test called a multislice CT scan to exclude the presence of renal arterial stenoses and establish the anatomy of the renal arteries.
Under Royal Brompton Hospital’s tight regulations, the need for treatment must be confirmed by a group of hypertension and cardiology specialists.
Honorary consultant cardiologist