Lifting the veil on how we see the heart and how it affects our health

THERE is something reassuring in the simple act of checking a patient’s pulse. It’s a bit like a hand on the shoulder.

In people’s minds it represents a physician’s connection and affinity to the body and its internal workings, bringing about a confidence and trust that might otherwise take much longer to build.

And a doctor can tell a lot from it. From its rhythm, frequency, quality and volume, one can tell whether someone’s heart is healthy or otherwise.

These steady perpetual beats, felt all over the body but most commonly monitored at the wrist, have been the only window into the workings of the heart that physicians have had for millennia.

Throughout history, the pulse has been a symbol of life and of vitality and the heart itself has become synonymous with our essence or soul; the centre of our being.

It’s little wonder considering that if the heart stops, we do too.

For a long time, we have had only the ability to hear it and feel it as it beats away.

Only recently have we been able to delve into the intricacies of each beat and, from a medical point of view, this has been used to our advantage in treating all manner of arrhythmias and heart conditions.

The invention of the stethoscope enabled a big advance in our understanding, combined with increased anatomical knowledge of the chambers and valves of the heart.

The classic “lub dub” of the heart heard when listening over the chest represents one set of valves opening and then closing as the second set take their turn.

The first electrocardiogram (ECG) was conceived and built in 1895 by a Dutch physician called Willem Einthoven.

This harnessed the electrical current produced by a small circle of cells in the heart from which each impulse originates.

This grouping of cells is called the sinoatrial node and every heart beat starts there. This node is our natural pacemaker and the current produced then travels downwards through fibres running through the centre of the heart before spreading back up on to the walls.

In doing so, the muscle contracts as the current passes through and this is what drives the pumping action that pushes blood out of the heart through the valves and into the arteries.

The commonly held belief is that the heart is on the left side of the chest. In reality, it is more central than many people realise. However, we feel it more on the left as it is angled to the left.

The ventricles, the two large pumping chambers, sit at the bottom of the heart.

The current runs roughly diagonally from right to left. In inventing the ECG to measure this current, Einthoven invented a way for us to see each beat of the heart.

Electrodes were placed on the right and left shoulders and on the left leg (at the time the electrodes were buckets of water into which patients had to dip their hands and feet) and the signals were converted on to paper, giving us the familiar pattern we see in the top diagram.

Each bump and wave represents a different phase of the heart beat as the current runs down, outwards and upwards and then repolarises again.

The heart beats about 100,000 times a day, 35 million times a year and, over an average lifespan, around 2.5 billion times.

Each beat is a contraction with a force similar to that needed to squeeze a tennis ball.

The heart muscles work twice as hard as the leg muscles of someone sprinting. Thankfully, for the most part, the beats are all regular and reliable.

But, occasionally, they can become more irregular and this is where potentially an arrhythmia develops. There are many types but one of the most common is called atrial fibrillation.

You will see in the middle diagram that the gaps between successive waves (the tallest wave is known as the R-wave and is a good landmark for each beat) vary in a random fashion.

An ECG can pick this up and confirm it in a way that is more difficult when just feeling the pulse.

Often people will not be aware they even have this particular arrhythmia but sometimes it causes a racing, fluttering feeling or manifests itself through a sensation of palpitations and it can give rise to quite unpleasant symptoms of weakness, faintness or dizziness.

Diagnosis and treatment are important because atrial fibrillation is associated with a significantly increased risk of stroke. Initially, the ECG was used to pick up arrhythmias but as the 20th century progressed, it became a tool used in the diagnosis of heart attacks.

The classic appearance on an ECG in someone with central chest pain is shown in the third diagram. This is known as “tombstoning” and is not a good sign.

A heart attack is the loss of blood supply to part of the heart muscle due to blockage of a coronary artery.

A heart attack (myocardial infarction) that causes this tombstoning involves the section between the S and T waves rising — something we call it ST elevation (or STEMI in medical jargon).

If the blockage is in one of the arteries round the side or back of the heart, it might not give this appearance (making it an NSTEMI) but, either way, the ability to confirm what is going on with this relatively simple test is extremely important. Having an ECG really is simple. It doesn’t hurt and it can be done in a few minutes. You no longer have to dip your hands and feet in buckets of saline.

Having one involves having some stickers applied to your arms and legs and then some on your chest as well.

A lead is connected to each sticker and the reading is taken while you lie still.

The extra leads on the chest are a newer feature developed over the last century and givimg rise to something known as a “12-lead” ECG. This means that, rather than just the one angle, 12 different angles of current can be analysed.

These produce lines of ECG that look quite different from each other but they give much more of a cross-sectional element to the analysis of the heart.

An experienced cardiologist can look at a 12-lead ECG and glean all sorts of information — whether parts of the heart are abnormally large, whether there are abnormal pathways the current is diverting down, whether the heart is angled differently from normal… the list goes on.

The 12-lead ECG is the most commonly used test for the heart with more than 300 million performed globally each year.

Because sometimes arrhythmias are not always present but come and go randomly, a portable ECG was invented in the Sixties that one wears over 24 hours while carrying it around in order to catch them when they occur.

The first one weighed around 80kg which, I suspect, was enough to give someone palpitations on its own.

Thankfully, these Holter monitors (named after their inventor), are much more practical now.

Cardiologists also have the option of putting someone on a treadmill and monitoring their heart via an ECG to see how they respond to stress — this is known as an exercise ECG, or stress test. Very useful.

Such is the endless drive of technology, even our watches can provide us with a rudimentary ECG these days.

While these watches can only give us the equivalent of one lead, they can still be useful in measuring the regularity of a pulse so something like AF can be picked up.

There are also various small devices that can be linked to mobile phones to give a quick ECG in order to capture what’s going on when a particular symptom occurs.

ECGs then are a vital part of our diagnostic arsenal.

Simple, harmless and packed with information, the ECG lifts the veil on how we see the heart and how it affects our health.