Medicines and Cardiovascular Disease Treatments

Treating a cause or relieving symptoms

Medicines can help in different ways. Some control or eliminate the cause of a disease; others reduce the severity or duration of its symptoms. Relieving symptoms can make someone more comfortable without curing the underlying disease.

Antibiotics kill bacteria or prevent their growth. For example, penicillin interferes with processes in bacterial cells. An effective antibiotic can therefore treat the cause of a bacterial infection. Different bacteria respond to different antibiotics, so choosing an appropriate antibiotic matters.

Antibiotics do not work against viruses. Viruses reproduce inside the body’s cells, and the bacterial processes targeted by antibiotics are not present in viruses. Developing medicines against viruses is difficult because a treatment must interfere with the virus without damaging the patient’s cells.

Painkillers reduce pain but do not kill pathogens. Someone with an infection might therefore receive a painkiller to relieve symptoms as well as a medicine that treats the infection. Unnecessary antibiotic use should be avoided because it encourages the spread of antibiotic-resistant bacteria, making infections harder to treat.

Comparing antibiotics using clear zones

Bacteria can grow on nutrient agar jelly in a Petri dish. When an antibiotic disc is placed on the agar, the antibiotic spreads into it. If the bacteria are susceptible, their growth is prevented around the disc, leaving a clear inhibition zone.

Measuring this zone gives a numerical way to compare treatments rather than judging their effects by eye. Under comparable conditions, a larger clear zone indicates that bacterial growth has been prevented over a larger area. This is evidence of effectiveness against the bacteria tested, not proof that the antibiotic will be best for every infection. A fair comparison uses the same bacteria and comparable antibiotic quantities and growth conditions.

When measuring a school culture, keep the dish closed and measure through it. Do not open an incubated culture to obtain a clearer view.

Turning a diameter into an area

The cross-sectional area of a circular bacterial culture, or the area enclosed by a circular clear zone, is calculated using:

$$A = \pi r^2$$

Here, $A$ is area and $r$ is radius: the distance from the centre to the edge. The diameter passes through the centre from one edge to the opposite edge, so the radius is half the diameter. If the radius is measured in millimetres, the area is in square millimetres, $\text{mm}^2$.

Suppose a circular bacterial culture has a diameter of 10 mm. Its radius is $10 \div 2 = 5\text{ mm}$, so its cross-sectional area is $\pi \times 5^2 \approx 78.5\text{ mm}^2$. This measures the area occupied by the culture, not the number of bacterial cells.

A clear zone may not be perfectly circular. Measure its full diameter in at least two different directions and calculate the mean. For example, suppose perpendicular diameters are 12 mm and 16 mm. The mean diameter is $(12 + 16) \div 2 = 14\text{ mm}$, giving a radius of 7 mm. The estimated area is therefore $\pi \times 7^2 \approx 153.9\text{ mm}^2$. Using a mean diameter treats the zone as approximately circular, so the result is an estimate.

Why cardiovascular disease needs prevention and treatment

Cardiovascular disease affects the heart or blood vessels. One important example is coronary heart disease. The heart muscle needs its own blood supply, delivered by the coronary arteries, to obtain oxygen and glucose for respiration.

Fatty deposits called plaques can narrow these arteries. Restricted blood flow may cause chest pain called angina. If blood flow becomes completely blocked, heart muscle cells can die, causing a heart attack.

Strategies can act at different stages: lifestyle changes reduce the chance of disease developing, medicines can reduce particular risks, and procedures can restore blood flow when an artery is already narrowed or blocked.

Lowering risk through lifestyle changes

Stopping smoking reduces exposure to chemicals that damage arteries. A balanced diet with less saturated fat and more fruit and vegetables can help reduce blood cholesterol and support a healthy body mass. Regular exercise can help control body mass, lower blood pressure and improve cardiovascular health. Avoiding excessive alcohol consumption also reduces a cardiovascular risk factor.

These changes have advantages over waiting until disease develops. They can reduce several risks together, benefit other aspects of health and avoid the risks of surgery. However, maintaining changes can be difficult, and the benefits develop over time. Lifestyle changes also cannot reliably restore blood flow through a severely blocked artery.

Prevention is therefore valuable, but it is not a substitute for necessary treatment. Someone with established disease may need lifestyle changes alongside medicines or a procedure.

Medicines and procedures for coronary heart disease

Medicines: a doctor may prescribe aspirin to reduce the risk of blood clots forming in arteries. This can lower the chance of a clot blocking blood flow. Taking a medicine avoids an operation, but it may need to be taken regularly, can have side effects and does not physically remove an existing plaque. Treatment should be medically supervised.

Angioplasty and stents: a small balloon is guided into a narrowed artery and inflated to press the plaque against the artery wall. A mesh tube called a stent can then hold the artery open, improving blood flow to the heart muscle. Some stents release a medicine to help prevent further narrowing. This directly treats the narrowing, but it is still a procedure with risks and does not remove the underlying risk factors.

Coronary bypass surgery: a blood vessel taken from elsewhere in the patient’s body is used to create a new route around a blocked section of coronary artery. This allows blood to reach the heart muscle without passing through the blockage. It can help when an alternative route is needed, but it involves an operation and recovery, with risks including bleeding, infection and complications from anaesthesia.

Heart transplantation: in severe cases, a diseased heart may be replaced with a donor heart. Suitable donors are scarce, and the recipient’s immune system may reject the organ. Long-term medicines that suppress the immune system may be needed, increasing susceptibility to infection. Transplantation also carries the risks of major surgery.

Reaching a justified treatment decision

There is no single strategy that is best for everyone. A useful evaluation weighs the likely improvement against side effects, procedural risks, the severity of disease and the patient’s ability to sustain treatment.

For someone without established disease, reducing risk through lifestyle changes has clear advantages over waiting for a blockage and then operating. For someone whose heart muscle already receives too little blood, lifestyle changes alone may be insufficient: a stent or bypass may provide a more immediate improvement. The strongest conclusion is often a combination of approaches—treat the existing problem while continuing to reduce the risk of further disease.

Medicines

• Antibiotics: kill bacteria or inhibit their growth; ineffective against viruses.
• Painkillers: relieve symptoms without killing pathogens.
• Choose an antibiotic effective against the bacteria involved; avoid unnecessary use.

Areas of cultures and clear zones

$$A = \pi r^2 \qquad r = \frac{d}{2}$$