Metronomic consistency. Brute force. Vital organ. Three phrases that describe one of the most essential organs in our body – the heart. While the electrical conduction systems within the heart are subject to the chemical complexity that underlies all of biochemistry, the function of the heart within our body remains relatively simple. It is a pump, which delivers vital nutrients and oxygen to body cells, so that life can continue. This crucial role of the heart is emphasised within clinical medicine also – the code for cardiac arrest is present in every hospital and takes priority over all other emergency procedures. One can also take a look at cardiac arrest survival rates to see how integral to life the heart is. Without emergency intervention, when the heart stops, survival rates stand at around a meagre 12%. Yet, it would be wrong to suggest that medicine has made anything but enormous leaps when it comes to the management of cardiac conditions over the last 2 centuries and this article takes a look at the technology that has made it possible.
The first piece of technology is synonymous with the medical profession in general and it’s a treasure that all doctors carry – their stethoscope. While it is among the most basic technology present in medicine (indeed its first form by Rene Laennec consisted of a rolled tube of paper to amplify the heart sounds), it can give doctors a huge insight into the workings of the body without immediately undergoing any time-consuming, invasive and potentially unnecessary tests. Its key components are the diaphragm (to identify high frequency sounds) and the bell ( to identify low frequency sounds). In the study of cardiology specifically, the stethoscope can be used to make rapid diagnoses – from the irregularity of atrial fibrillation to the turbulence that accompanies mitral regurgitation. Its simplicity and portable nature along with the range of relatively accurate diagnoses that can be made are certainly remarkable. However, this simplicity means that there is an inherent limit to what it can achieve – so more ‘fancy tech’ is needed.
The next stage of our journey takes us to the electrocardiogram (ECG), which remains today the standard for measuring the electrical efficacy of the heart. What is produced is a graph of voltage against time – this is done as metal electrodes are placed on the skin and these map the small changes in electrical activity in the skin. Like the stethoscope, this is a relatively simple and quick test to carry out and is not invasive. There are so many irregularities that can be spotted by an ECG so it would be a futile attempt to list them all and, as a true diagnostic tool should, influences the treatment given. For example, if there’s evidence of atrial fibrillation, the patient may be subject to a radiofrequency ablation (essentially ‘burning’ the regions of faulty conduction in the heart’) or perhaps antiplatelet medications to reduce the risk of stroke. Again, like the stethoscope, the ECG has quite a clear limitation – if there is nothing wrong with the electrical conduction systems but instead it is a problem of the vessels, the ECG will be normal and not show anything.
It’s all very well using diagnostics to identify the key problems but it is the procedural and surgical aspects that allow conditions to be directly treated . If the heart is to be operated on, its function in delivering oxygen to key tissues has to be replicated. The heart is in every way a vital organ and operating on the heart is a risky business. Indeed, the birth of open heart surgery became possible due to the invention of the heart-lung machine (also known as cardiopulmonary bypass) and its supplementary necessities. The 2 key parts of the machine are the ‘heart’ (the pump) and the lungs (the oxygenator) – the pump is most often centrifugal as this provides less hassle with blood flow while the oxygenator removes carbon dioxide and replenishes oxygen. Along with this, a fluid is used to stop the heart known as cardioplegia – these prevent the generation of action potentials in the heart through inhibiting sodium currents.
An aspect that is as crucial in ‘helping the heart’ as the surgical and is the pharmacological aspect and just as the heart is crucial in helping the body stay fit for function, when it is failing, many parts of the body may also fail. One of the most popular families of medications are the anticoagulants/antiplatelets. As suggested in the name, these drugs act against the work of platelets to prevent clotting as if this occurs, the patients in question may have a dangerous internal clot (such as a stroke) – the most common first line agents can be identified through their suffix ‘rin’, such as warfarin and heparin. These are not without risk however, as inhibiting the work of platelets may increase the risk of major bleeding events – for this reason, second line drugs are present and have been trialled, such as apixaban, which does not directly interfere with platelets, but instead with the clotting factors.
It is a testament to how heralded the heart is that cardiology and cardiac surgery still remain among the most awe-inspiring medical specialities. The massive advances that have been made mean that clinical care in cardiology units is multi-dimensional and that surgery has evolved so much that for one defect, there may be multiple operations available. There, as ever, remains work to be done but history has favoured us kindly when helping the heart.
- Medicine, Institute of (2015-06-30). Strategies to Improve Cardiac Arrest Survival: A Time to Act
- University of Washington Department of Medicine ‘Technique: Heart Sounds & Murmurs’ – https://depts.washington.edu/physdx/heart/tech.html
- Lich, Bryan (2004). Manual of Clinical Pefusion (2nd ed.). Fort Myers, Florida: perfusion.com. p. 141.
- Kiser, Kathryn (2017). Oral Anticoagulation Therapy: Cases and Clinical Correlation. Springer. p. 11. ISBN9783319546438.