High blood pressure is a common condition which affects 1 in 5 Australians during their lifetime and if left untreated increases the risk of serious health problems including stroke, heart failure and kidney failure. Hypertension during pregnancy (‘pre-eclampsia’) can affect both mother and baby.
When the heart beats, it develops a very high pressure over a short period of time which ejects the blood out of the left ventricle of the heart into the large arteries connected to it – the aorta and its major branches. When the left ventricle relaxes, the back pressure closes the aortic valve trapping blood in these large arteries and allowing the blood to continue flowing even though the heart is relaxing between beats. The highest blood pressure is called the systolic and the lowest, the diastolic blood pressure.
Hypertension occurs when the pressure in arteries is higher than normally needed to get blood to flow through the tissues of the body. Systolic and diastolic blood pressure levels are both important risk factors; of the two, systolic carries a greater risk than diastolic hypertension.
Generally hypertension is silent but some patients are aware of feeling generally unwell and headaches can occur which may be migrainous but are often not. If your BP is not checked regularly the condition will be missed in most patients until complications like stroke or heart attack occur.
Genetic and lifestyle factors are important in causing or worsening hypertension. Lifestyle factors contributing to hypertension include a high (sodium) salt or alcohol intake, obesity and being sedentary. Sleep apnoea is increasingly recognised as a contributing factor. High blood pressure is caused by many different mechanisms with persistently high blood pressure the end result. As with many other health problems, prevention is the key.
In general we separate patients into those with clearly normal BP (<120/80 mmHg), borderline or pre-hypertensive’ (<140/90 mmHg) and hypertension (over 140/ 90) taken as the average of 3 readings at rest.
The situation is complicated by white coat hypertension when BP is high when taken by a doctor or nurse and normal measured by a BP device in the home. This is a situation in which patients tend to experience more side-effects than benefits of treatment. Nowadays we consider white coat hypertension can lead to genuine hypertension in some patients so if it is not treated it needs to be checked regularly.
Ambulatory BP recordings are valuable for diagnosis of hypertension and monitoring the effects of lifestyle changes and drug treatment. Increasingly we look to home BP measurements as one way of monitoring BP over time. Home BP
Lifestyle changes are a cornerstone of treatment but are difficult to maintain over the long term in order to be of benefit. Bariatric surgery (lap band/gastric sleeve procedures) can lower blood pressure substantially in very overweight or obese patients.
Drug treatments have been shown to improve outcome in many clinical trials. In order to bring BP back into normal range many patients need multiple drugs – newer combination tablets with several medications have been a major advance. Reducing tablet numbers is known to be useful for compliance. The more tablets people have to take, the less likely they are to take them.
The main barrier to successful treatment of hypertension is long term compliance with treatment.
Obstructive sleep apnoea (OSA) is linked with the development of high blood pressure and untreated sleep apnoea can make hypertension resistant to treatment. Treatment of OSA using CPAP has been shown to lower blood pressure.
New procedures such as renal artery denervation are being introduced for those with drug resistant hypertension (despite 3 or more drugs).
Renal Artery Denervation to Treat High Blood Pressure
High blood pressure (BP) is the end result of many factors and results among other things in stroke, heart failure and kidney failure when untreated or inadequately treated. The kidney is also closely involved in the control of BP and there are nerves which go both to and from the kidneys to the brain which are part of the body’s system regulating BP.
Renal artery denervation is a novel blood pressure lowering treatment, specifically in those patients with difficult to control high blood pressure, despite multiple medications. It is based on the principle that nerves that cause high blood pressure lie in the kidney artery wall, and thus interruption of these nerves might dramatically reduce blood pressure. The procedure involves passing a fine tube or catheter into the femoral artery in the groin and via X ray guidance, threading a specially designed catheter into the kidney arteries. A low energy current is then administered at several points along the artery, leading to inactivation of the nerves that play a key critical role in causing high blood pressure. A significant reduction in blood pressure (20mmHg) is seen within a few weeks of the treatment.
The level at which lowering BP is beneficial depends on factors which include diabetes and pregnancy (when recommended BP levels are lower). Evidence of effects of hypertension on the heart (left ventricular hypertrophy, heart failure) or kidney function lead to more aggressive treatment approaches and lower targets. Treating blood pressure in pregnancy is limited by the number of drugs which are safe in pregnancy.