ECG and Stress Tests: What You Need to Know About Heart Diagnostic Tests

When your doctor suspects something’s off with your heart, two tests come up again and again: the ECG and the stress test. They’re not scary, they’re not surgery, and they don’t require needles or incisions. But they can reveal hidden problems your resting heart won’t show. If you’ve been told you need one-or both-here’s what actually happens, why it matters, and what the results mean.

What an ECG Really Shows

An ECG, or electrocardiogram, is a snapshot of your heart’s electrical activity. It’s quick, painless, and done in just a few minutes. Electrodes stick to your chest, arms, and legs, picking up tiny electrical signals as your heart beats. These signals create a graph on a screen or paper-a series of waves and spikes that tell a story.

That story includes your heart rate (is it too fast, too slow?), rhythm (is it irregular?), and whether any part of your heart is struggling to get blood or has been damaged. A past heart attack leaves a signature on the ECG. So does an enlarged heart, or an abnormal electrical pathway. It’s not perfect-it won’t catch every problem-but it’s the first line of defense.

Doctors use it for routine checkups, after chest pain, or when you feel dizzy or short of breath. In the UK, nearly 8 million ECGs are done every year. Most of them come back normal. But when they don’t, they point you toward the next step: a stress test.

Why You Might Need a Stress Test

Your heart works fine when you’re sitting still. But what happens when you climb stairs? When you’re running late? When your heart has to pump harder? That’s where the stress test comes in.

It’s designed to make your heart work harder-either by having you walk on a treadmill, or by using medicine to mimic exercise if you can’t move well. While you’re under stress, your heart’s electrical activity is monitored through an ECG, and your blood pressure is checked every few minutes.

The goal? To see if your heart gets enough blood when it’s under pressure. If part of your heart muscle isn’t getting enough oxygen during exercise, it can cause changes in the ECG pattern. That’s often a sign of narrowed arteries-coronary artery disease, or CAD. This is the most common cause of heart attacks.

Stress tests aren’t for everyone. They’re most useful for people with moderate risk-someone with chest discomfort, high blood pressure, or a family history of heart disease, but no clear signs of a heart attack. If you’re at low risk, an ECG alone might be enough. If you’re at high risk, you might skip straight to a scan.

Exercise vs. Chemical Stress Tests

There are two main types of stress tests. One makes you move. The other makes medicine do the work.

The exercise stress test is the classic version. You walk on a treadmill, starting slow and getting harder every three minutes. The goal is to reach 85% of your maximum heart rate-roughly 220 minus your age. So if you’re 55, you’re aiming for about 142 beats per minute. Most people last 8 to 12 minutes. If you get too tired, dizzy, or have chest pain, you stop.

The chemical stress test is for people who can’t walk due to arthritis, lung disease, or other mobility issues. You get medicine through an IV-drugs like adenosine or dobutamine-that make your heart beat faster and harder, just like exercise. You might feel flushed, short of breath, or have a strange sensation in your chest. It’s not pleasant, but it’s brief-usually under 10 minutes. The side effects fade fast.

Neither test is better than the other. It’s about what your body can handle. Your doctor picks based on your health, age, and symptoms.

What the Numbers Mean

Stress test results aren’t just ‘normal’ or ‘abnormal.’ They’re graded.

One key number is how long you lasted on the treadmill. Each extra minute you walk reduces your risk of a future heart event by about 12%. If you make it past 10 minutes, your prognosis is generally good.

Another is the ECG pattern. If the ST segment dips during exercise, that’s a classic red flag for reduced blood flow. But it’s not foolproof. In women, especially younger women, this sign can be misleading. Their heart disease often affects smaller vessels, not the big arteries-and that doesn’t always show up on a standard ECG stress test.

That’s why many doctors now prefer stress echocardiography. It’s the same treadmill test, but with an ultrasound machine taking pictures of your heart before and after exercise. If a part of the heart wall stops moving properly under stress, it’s a strong sign of blocked arteries. This test is more accurate than ECG alone-especially for women-and doesn’t use radiation.

Nuclear stress tests, which use a small amount of radioactive dye, are even more sensitive. They can show exactly which areas of the heart aren’t getting enough blood. But they involve radiation-about the same as 3-4 years of natural background exposure. So they’re saved for cases where the diagnosis is still unclear.

What to Expect Before and After

Preparing is simple. No caffeine for 24 hours before the test. That includes coffee, tea, chocolate, and some painkillers. Wear comfortable clothes and walking shoes. Don’t eat a heavy meal right before.

Afterward, you can usually go right back to your day. No recovery time. No restrictions. If you had a chemical stress test, you might feel a little off for a few minutes-but the staff will monitor you until you’re back to normal.

Results often come within hours. Many clinics give you a quick summary before you leave. A full report from your cardiologist follows within a few days. If something’s wrong, they’ll explain what it means and what comes next-maybe more tests, medication, or lifestyle changes.

What Stress Tests Can’t Do

They’re not magic. A normal stress test doesn’t mean your heart is completely healthy. It doesn’t catch early artery buildup before it causes symptoms. It won’t detect microvascular disease-the kind that affects tiny blood vessels in the heart, common in women and people with diabetes.

And false negatives happen. About 1 in 3 women with heart disease get a normal result on a standard ECG stress test. That’s why experts now recommend stress echocardiography for women with symptoms and intermediate risk. It’s more sensitive, safer, and just as accessible.

Also, stress tests aren’t for everyone. If you’ve had a heart attack in the last two days, or have unstable heart rhythms or severe heart failure, you won’t be tested. The risk outweighs the benefit.

The Future of Heart Testing

Technology is making these tests smarter. New AI tools can analyze ECG patterns during stress tests with 20% more accuracy than human readers. Portable devices are now approved for use in clinics, pharmacies, even GP offices-making testing more accessible.

At the same time, CT scans of the heart’s arteries are becoming cheaper and faster. Some doctors are starting to use them first for low-risk patients, skipping stress tests entirely. But for now, stress testing remains the go-to functional test for most people with chest pain or unexplained symptoms.

And while the cost of nuclear stress tests can hit £700 or more, stress echocardiography is often £100-£200 cheaper and just as effective for many cases. Insurance usually covers them if your doctor says they’re medically necessary.

Real Stories, Real Results

One patient in Leeds, 58, had mild chest tightness after walking uphill. Her resting ECG was normal. Her stress test showed clear signs of reduced blood flow. She went on to have a coronary angiogram, found a 70% blockage, and got a stent. She’s back hiking now.

Another, a 47-year-old woman with fatigue and dizziness, had a normal exercise ECG. Her doctor ordered a stress echo. It showed subtle wall motion changes-evidence of microvascular disease. She started on medication and lifestyle changes. Her symptoms improved within weeks.

Not everyone needs a stress test. But if you’ve been told you might benefit from one, don’t delay. It’s not about fear. It’s about knowing. And knowing gives you power-to change, to treat, to live better.