Science & Tech: Heart disease

Heart disease is the single biggest killer of women in New Zealand. Photo / AP

Heart disease kills more than 6000 Kiwis a year with genes, unhealthy eating, lack of exercise, diabetes, high blood pressure and smoking are all deemed risk factors.

Heart disease kills more people in New Zealand than in most other OECD countries, according to a recent international OECD health report. Figures show that heart disease here is responsible for around 30 per cent of all deaths, scoring us 18 per cent higher than the OECD average and resulting in over 6000 Kiwi deaths every year, the equivalent of one every 90 minutes.

Also known as cardiovascular disease, heart disease encompasses a range of conditions, including coronary artery disease, arrhythmias (problems with heart rhythm) and congenital heart defects.

Your heart is a muscular pump the size of a fist that sends oxygen-rich blood around your body. The blood travels through blood vessels called arteries to the organs of your body and comes back to the heart through your veins.

Heart disease occurs when the coronary arteries which carry the blood feeding the heart itself become blocked by a build-up of fatty deposits. This clogging process called atherosclerosis deposits plaques formed from cholesterol, fatty substances, cellular waste products, calcium and the clotting material fibrin in the blood. The plaques narrow the arteries, reducing the space that the blood can flow in and blocking nutrient delivery to the artery wall.

Because of the narrowing, blood has to be pumped harder to flow through, resulting in high blood pressure and putting further strain on the heart.

If your arteries are only partially blocked you might experience severe chest pains or angina spreading across your upper body as your heart struggles to keep beating with a restricted oxygen supply.

Sometimes the plaque cracks open, triggering a blood clot to form around the crack which can completely block the artery, causing a heart attack. Without oxygen, the heart muscle starts to die. Survival is determined by the amount of muscle that dies before medical intervention.

Using drugs to dissolve the clot or surgery to open up the blocked artery, the aim is to get oxygen back into the heart muscle. The smaller the area damaged, the greater the chance of recovery.

Genetics may deal you a poor hand. Other factors include an unhealthy diet, lack of exercise, diabetes, high blood pressure and smoking.

Heart disease is often seen as only affecting males, and the mortality rate for Maori is more than twice as high as that among non-Maori, but what isn't commonly known is that women are four times more likely to die of heart disease than from breast cancer. The most common heart attack symptom is an uncomfortable pressure, squeezing, fullness or pain in the centre of your chest. Other symptoms include pain in one or both arms, shortness of breath, light-headedness and breaking out in a cold sweat. Women are more likely to experience different symptoms including shortness of breath, nausea or vomiting and back or jaw pain that are easily dismissed as just feeling under the weather, which may explain why heart disease is the single biggest killer of women in New Zealand.

The good news is that the OECD report shows New Zealand's heart disease mortality rate has dropped by 53 per cent over the past 23 years thanks to better medications for blood pressure and less exposure to risk factors such as passive smoking.

During the Heart Foundation's annual appeal launch, it's probably a good time to think about your risk factors and take stock of your own heart health.

• Dr Michelle Dickinson, also known as Nanogirl, is an Auckland University nanotechnologist who is passionate about getting Kiwis hooked on science. Tweet her your science questions @medickinson