These two cell types differ not only in their function, but also in their appearance. The pacemakers are somewhat larger than their colleagues, and have a ‘pale and interesting’ look about them. With impressive regularity, they make sure the heart beats at a constant rate — between 60 and 80 times a minute at rest. Provided, that is, that they are healthy and functioning as they should.

      Unlike some of the other organs of our bodies, the heart has very limited regenerative capabilities. Compared to the liver, which can renew its cells exceptionally quickly, and even the lungs, which manage the same trick but at a much more leisurely pace, the heart is at the bottom of the regeneration league. Fewer than half the heart’s cells are replaced over the course of an entire human life.

      Despite this, the heart has all the cardiomyocytes it needs. The left ventricle alone is made up of an estimated six billion cells. If you were to look at each one of these cells through a microscope for half a second, you would have to spend almost 200 years at the eyepiece. That’s without counting breaks for sleeping, eating, or satisfying other natural needs. Wow! That’s a lot of cells! This naturally raises the question of where the heart gets all the energy it needs to pump some five to six litres (1–1.5 gallons) of blood per minute, even when the body is at rest. The answer is simple: the heart is a believer in self-sufficiency.

      Soon after the blood has exited the left ventricle to enter the body’s circulatory system, it can take one of three possible routes. Most of it flows through the aorta towards our internal organs, arms, and legs. If it does so, it bypasses two exits just beyond the aortic valve, which lead to the right and left coronary arteries. Those vessels spread out into many smaller branches and supply the tissues of the heart with the nutrients they need.

      At first glance, the pattern of those branches appears to be very similar from person to person, but a closer examination reveals that the details vary widely. Just like actual trees: a trunk in the middle, some branches, and a lot of leaves. It’s not until you look more closely that you see each tree’s particular characteristics, such as, for example, the pattern of the branches, the shape of the leaves, and the colour of the blossom.

      In a left-dominant heart, the left coronary artery also supplies the posterior wall of the heart with oxygen and nutrients; in a right-dominant heart, this task is done by the right coronary artery. The most common type is the one in which both coronary arteries provide that supply in equal measure. This type is described by cardiologists as co-dominant.

      Apart from forming branches, the coronary arteries can also form anastomoses. These are new connections created between blood vessels to make sure that effectively all the muscle tissue of the heart is constantly provided with the best possible supply of blood. Unfortunately, when one of the larger blood vessels becomes blocked in a heart attack, these anastomoses are almost never able to create a circulatory bypass as an alternative route to guarantee the continued supply of oxygen to the heart muscles.

      When a heart attack occurs, the undersupplied tissues of the heart begin to die. This can have varying consequences, depending on the location and size of the area supplied by the blocked artery. In the worst case, the heart simply stops beating immediately. If some of the rowers stop rowing, the boat may either start to spin round in circles or come to a complete halt. If the pacemaker stops beating its drum to dictate the rhythm, all the rowers will begin rowing for all they are worth, but out of synch with each other, so the boat still fails to move an inch. Sometimes, however, the reduced blood supply causes only slight irregularities in the rhythm of the heartbeat, and such very minor heart attacks often go unnoticed.

      An arterial blockage — doctors call it an occlusion — leading to a reduced blood supply to the right side of the heart often causes the jugular veins of the neck to become engorged, since the blood flowing through those veins back to the heart can no longer be pumped into the pulmonary circulation system quickly enough by the right side of the heart. This leads to a traffic jam in the jugular. And no one likes a traffic jam.

      An insufficient blood supply to the muscles of the left side of the heart, on the other hand, often leads to an accumulation of fluid in the lungs, known to doctors as pulmonary oedema. This is also caused by a traffic jam, but this time the blocked blood backs up in the pulmonary vein all the way to the tissue of the lungs. This builds up the pressure, causing fluid from the capillaries of the alveoli — the little air sacs in the lungs — to be pressed into the cavities that are normally filled with air, flooding them. This can be so conspicuous that a bubbling in the chest may be heard even without the aid of a stethoscope. In especially serious cases, the lungs can become so full of foam that the patient has to cough terribly hard to get rid of it. This can be a rather disgusting process, not only for the person concerned, but also for the emergency medical team treating the patient.

      If no emergency doctor is on the scene at this point, the hands of a paramedic are basically tied. She can do little more than a trained first-aider. Of course, a paramedic can administer oxygen, but a first-aider can also simply open the window to help the patient breathe more easily. If the symptoms of such cardiac congestion become so serious that the patient’s heart stops beating, anyone (not just a qualified medic) who discovers the unfortunate person should immediately begin resuscitation procedures. It would be good to have your last first-aid course fresh in your mind, but even less-than-correct resuscitation attempts are better than none at all.^*

      In addition to this, one thing is particularly important that has nothing to do with medical knowledge, machines, or electric shocks. It is providing for the patient’s general comfort. This is so important because patients who are suffering a heart attack are often extremely frightened. The more anxious a person is, however, the more stressed he will be, and the faster his already-weakened heart will beat as a result. And that could be the final nail in his coffin, so to speak. For this reason, it is crucial to create as pleasant an atmosphere as possible during the time until professional help arrives,