Hypertension is a blood pressure measuring 140/90 mmHg or greater most of the time. Blood pressure fluctuates throughout the day but normally does exceed levels above 130/80 mmHg except in acute stress or shock. A normal blood pressure may even drop as low as 100/60 mmHg during relaxed periods and sleep. With hypertension the persistently high blood pressure has a host of effects on the body. In the short term this is not often life threatening particularly if it is a moderate elevation. However, if chronic hypertension is left untreated, it can be detrimental to many organs and systems in the body. Irrespective of the cause, the heart is also affected by hypertension and may undergo various changes that can impair its functioning.
What is hypertensive heart disease?
Hypertensive heart disease (HHD) is the structural and functional changes of the heart associated with hypertension (high blood pressure). These changes are primarily seen in the heart wall but may also affect the heart valves, blood supply to the heart and conduction system that regulates the electrical activity of the heart. It may also arise secondary to abnormalities of other organs and systems as a result of hypertension. These changes are mainly seen with prolonged uncontrolled hypertension.
The heart is a muscular organ that is constantly receiving and pumping blood. The right side of the heart receives oxygen-deficient (deoxygenated) blood from the body (right atrium) and then pumps it out to the lungs for oxygenation (right ventricle). Once oxygenated, the blood returns to the heart (left atrium) and is then pushed out to the rest of the body (left ventricle). Therefore the right side of the heart deals with pulmonary circulation (lung) and the left side of the heart handles systemic circulation. Systemic hypertension affects the left side of the heart and therefore HHD is more accurately referred to as left-sided hypertensive heart disease or systemic hypertensive heart disease
The right side of the heart may undergo changes as a result of pulmonary hypertension. This arises with lung disease, any obstruction or constriction of the pulmonary blood vessels and disorders restricting chest movement. In these instances, the changes to the heart are known as right-sided hypertensive heart disease, pulmonary hypertensive heart disease or cor pulmonale. This type of hypertensive heart disease is not discussed in this article.
Left-Sided Hypertensive Heart Disease
As explained above, the rise in blood pressure (hypertension) causes changes on the left side of the heart. These changes include hypertrophy (enlargement) of the left ventricle and eventually atrium as well as changes in the aorta and heart valves.
The heart has thick muscular walls and the large to medium sized arteries have thick elastic walls. This allows these structures to cope with the high pressures. Since the left side of the heart deals with higher pressures than the right, it has naturally thicker walls. However, with hypertension, the left side and particularly the left ventricle undergoes hypertrophy (enlargement). Initially the ventricle does not not enlarge although the wall thickens. The thickening of the left ventricle alone can almost double the weight of the heart.
The aorta carries blood from the left ventricle and distributes it throughout the body. In hypertension, the root of the aorta which is in contact with the left ventricle dilates. This widening affects the aortic valve from functioning. Normally the valve will prevent blood in the aorta from flowing backwards (regurgitation) into the left ventricle. However, when it is not functioning properly (aortic insufficiency), it cannot prevent this backward flow of blood.
Over time, the thicker ventricle wall becomes stiff and does not fill with blood as easily when the heart relaxes. This decreased compliance increases the pressure within the left atrium. Therefore the left atrium enlarges and its wall thickens. Along with this thickening, the electrical activity within the atrium is disrupted causing it to beat fast and quiver (atrial fibrillation – a type of arrhythmia). At the same time, the mitral valve between the left atrium and ventricle may not function properly (mitral regurgitation).
Effects of High Blood Pressure on the Heart
The changes associated with hypertension may lead to a host of pathology that can be severe and debilitating or even cause death. The long term effect on the heart due to uncontrolled hypertension includes :
- Congestive heart failure (CHF) discussed under heart failure.
- Ischemic heart diseasediscussed under coronary heart disease.
- Arrhythmia – irregular heart beat.
- Cardiomyopathy – abnormally enlarged heart muscle.
- Heart valve disease – dysfunctional heart valves.
Signs and Symptoms
With the changes in the heart structure that occurs with hypertension, the heart becomes less capable of pumping out blood. Therefore the body’s tissues are starved of oxygen. The heart muscle that is now thicker is also deprived of oxygen which causes injury to parts of it. Apart from the effects of high blood pressure, hypertensive heart disease also impacts other parts of the body. This further exacerbates the effects of hypertensive heart disease and thereby contributes to the clinical presentation.
The clinical features associated with hypertensive heart disease may vary depending on the type of heart disease that arises. Some of these signs and symptoms include :
- Fatigue and weakness
- Dyspnea – shortness of breath.
- Angina – chest pain associated with heart muscle injury.
- Dizziness and lightheadedness
- Fainting spells
- Cyanosis – bluish discoloration of the skin.
- Edema – swelling of the legs, arms and other parts of the body.
- Murmurs – abnormal and extra heart sounds.
- Arrhythmia – irregular heart beat.