Heart attack - On the horizon

New and improved techniques for the assessment and treatment of heart attacks are continually being explored. For example, newer imaging methods may allow better evaluation of heart muscleTissue made up of cells that can contract to bring about movement. damage, and researchers are always looking for fresh ways to limit the extent of this damage.

The following pages will discuss these techniques:

MRI to assess the extent of heart muscle damage

What is it?

Magnetic resonance imaging (MRIAn abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field.) is an imaging test that uses a powerful magnetic field; the benefit is it does not expose people to any radiation. It is not a new technology, but is not yet used routinely in those who have had a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction..

How does it work?

MRIAn abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field. is an imaging investigation that can assess how much heart muscleTissue made up of cells that can contract to bring about movement. tissue is living - viableCapable of survival.. This can be done in a number of ways, for example, by assessing the function of the heart and its physical structure. Determining the thickness of the heart wall also helps, as a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. may be associated with thinning of the heart wall.[1]

The procedure of assessing viability by MRIAn abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field. scanning involves the person having a small tube inserted into a vein A blood vessel that carries blood towards the heart. - this is called an intravenous line - before entering a scanner and having various images taken. Next, a small amount of substance called a contrast agentA substance taken (either by mouth or into a vein) by a person who is about to undergo an imaging investigation, to improve the visibility of the structures being imaged. Also known as contrast medium. is given via the intravenous line. After 10 minutes, additional images are taken. Changes in the heart muscleTissue made up of cells that can contract to bring about movement. after a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. mean that the contrast agentA substance taken (either by mouth or into a vein) by a person who is about to undergo an imaging investigation, to improve the visibility of the structures being imaged. Also known as contrast medium. becomes concentrated within the area of dead muscleTissue made up of cells that can contract to bring about movement. (infarcted tissue) that remains following the heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction..[1]
This technique can be used to highlight damaged areas that cannot be detected by other imaging techniques such as echocardiographyThe use of ultrasound to examine the heart as it is pumping. .[1]

Who is it for?

Being able to tell the difference between heart muscleTissue made up of cells that can contract to bring about movement. that is viableCapable of survival. and non-viableCapable of survival. is potentially very valuable for anyone who has had a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction.. If the damage to the heart muscleTissue made up of cells that can contract to bring about movement. after a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. is limited, then any heart failureFailure of the heart to pump adequately. should improve following the restoration of bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow through the coronaryRelating to the arteries supplying the heart itself. arteries. This will give the person a better chance of survival. On the other hand, if there is extensive damage to the heart muscleTissue made up of cells that can contract to bring about movement., abnormal heart rhythms are more likely.[1]

What stage of development has been reached?

While MRIAn abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field. is regularly used for the imaging of various other conditions, it is not routinely used after a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction..

Molecular imaging of heart attacks

What is it?

Molecular imaging is a newer group of imaging techniques that give information about the actual function of cells and tissues, rather than just their structure. Again, while molecular imaging is an accepted technology within modern medicine, its use in people who have had heart attacks is relatively new.

How does it work?

In molecular imaging, substances called biomarkersA substance that can be measured to help healthcare professionals to assess normal processes, disease processes or a person's response to treatment. are administered directly into the veins before a series of images are taken with any of a number of techniques, including MRIAn abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field., ultrasound and positron emission tomography (PET). These biomarkersA substance that can be measured to help healthcare professionals to assess normal processes, disease processes or a person's response to treatment. are taken up by specific tissues, and the pattern of this uptake can give information about the function of these tissues.[2]

Who is it for?

After a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction., the heart undergoes a complex process of repair, and what is known as remodellingRestructuring.. During this process, specific biochemical and structural changes take place. If healing is impaired, this may lead to thinning or rupture of the heart wall, abnormal dilation of the heart wall (aneurysmAn abnormal swelling in the wall of an artery.) or heart failureFailure of the heart to pump adequately..[2]

Although this remodellingRestructuring. process is extremely important, as yet there are limited methods of imaging and assessing it. Molecular imaging may provide a way of doing so.[2]

What stage of development has been reached?

While still in its early stages, molecular imaging can already be used to assess key processes in the remodellingRestructuring. of heart muscleTissue made up of cells that can contract to bring about movement. tissue after a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction.. These processes include the formation of new bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. vessels and 'cellThe basic unit of all living organisms. suicide' - known as apoptosisA natural process of programmed cell death, for example, when cells are old or damaged.. The discovery of new biomarkersA substance that can be measured to help healthcare professionals to assess normal processes, disease processes or a person's response to treatment. will allow for further advances in the imaging of healing in the damaged area of heart muscleTissue made up of cells that can contract to bring about movement. tissue, and much progress is expected by 2015.[2]

Stem cell therapy

What is it?

Stem cells are cells that have the ability to develop into any type of specialised cellThe basic unit of all living organisms. in the body. They can renew themselves as needed to help to replace lost cells. As such, they are vital in repairing damaged tissues.

Stem cellThe basic unit of all living organisms. therapy involves the transplantation of stem cells, usually from the bone marrowTissue within the bones where blood cells are formed., to the heart muscleTissue made up of cells that can contract to bring about movement.. The most direct way to deliver stem cells to the heart muscleTissue made up of cells that can contract to bring about movement. is by injecting them into the muscleTissue made up of cells that can contract to bring about movement., usually during coronaryRelating to the arteries supplying the heart itself. arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. bypass surgery that is frequently performed after a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction.. Other methods include administration during angioplastyThe mechanical widening or clearing of a narrowed or obstructed blood vessel, performed during angiography, which is used to help with visibility., or even by intravenous injection.[3,4]

A heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. results in the death of part of the heart muscleTissue made up of cells that can contract to bring about movement.. Unlike many other parts of the body, however, the heart cannot easily repair itself after injury. The rationale behind stem cellThe basic unit of all living organisms. therapy is that the implanted cells may be able to replace or help to repair any damaged heart muscleTissue made up of cells that can contract to bring about movement..[3] It is thought that delivering these stem cells to the heart can help to improve the formation of bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. vessels and perhaps even generate new heart muscleTissue made up of cells that can contract to bring about movement. tissue, improving the outcome for people with coronaryRelating to the arteries supplying the heart itself. arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. disease.[4]

How does it work?

The basis of using stem cells in heart disease is their potential to transform themselves into other cellThe basic unit of all living organisms. types, in this case, heart muscleTissue made up of cells that can contract to bring about movement. cells, a process known as differentiationThe process by which cells or tissues become specialised for a specific function.. These specialised cells then help to repair damaged heart muscleTissue made up of cells that can contract to bring about movement. tissue.[4]

It is still not entirely understand exactly how stem cellThe basic unit of all living organisms. therapy works, although much research has been done in the area. It is thought that the stem cells may change the levels of hormones within the tissues they are transplanted into. Alternatively, they may act as a 'reservoir' of new cells, which can form new bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. vessels and heart muscleTissue made up of cells that can contract to bring about movement., or in some way support existing heart muscleTissue made up of cells that can contract to bring about movement. cells.[3]

Who is it for?

A person who has had a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. may safely be given their own bone marrowTissue within the bones where blood cells are formed. stem cells, according to current evidence. Furthermore, the benefits seem to be significant.[3]

What stage of development has been reached?

The first Phase I clinical trials using bone marrowTissue within the bones where blood cells are formed. stem cells for heart attacks were carried out at the start of the 21st century.[3] Since then, several different centres around the world have started investigating the benefits of stem cells derived from bone marrowTissue within the bones where blood cells are formed. in heart attacks.[4] Although randomised controlled trialsStudies comparing the outcomes between one or more different treatments for a disease (or in some instances, preventive measures against that disease) and no active treatment at all (the placebo group). Study participants are allocated to the various groups on a random basis. May be abbreviated to RCT. are still needed, stem cellThe basic unit of all living organisms. therapy appears promising in this area.[3]

Newer anticoagulants

What are they?

Anticoagulants are medicines that help to prevent the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. from clotting. Usually, unfractionatedNot fractionated; that is, not divided up into separate parts. heparinA substance produced by the body, or given as medication, that reduces the likelihood of the blood to clot, coagulate. - that is, heparinA substance produced by the body, or given as medication, that reduces the likelihood of the blood to clot, coagulate. of varying molecular weight - is given alongside clot-busting drugs (this is called fibrinolyticA susbstance that can break down fibrin, the major component of blood clots. therapy) in the treatment of heart attacks. However, there is now a wealth of data surrounding the use of newer anticoagulantA medication that prevens blood from clotting, or which reduces the likelihood of the blood to clot. drugs in this area, including low molecular weight heparinA substance produced by the body, or given as medication, that reduces the likelihood of the blood to clot, coagulate., factor XaA coagulation factor, one of a group of proteins in the blood that help the blood to clot. inhibitors and direct thrombinAn enzyme that converts fibrinogen to fibrin during blood coagulation. inhibitors.[5]

The main role of anticoagulantA medication that prevens blood from clotting, or which reduces the likelihood of the blood to clot. therapy after a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. is not in restoring bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow through the coronaryRelating to the arteries supplying the heart itself. arteries, but in keeping them open after the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow has been restored. Additional benefits from these drugs include preventing the formation of bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. clots in the veins (deep vein thrombosisObstruction of one of the deep veins, often in the calf, by a blood clot. Often abbreviated to DVT., DVTDeep vein thrombosis: the obstruction of one of the deep veins, often in the calf, by a blood clot. ), the lungs (pulmonary embolismObstruction of blood flow by an embolus, a clot (or other material, for example, fat or air) that has become dislodged from elsewhere in the blood system.) and the wall of the heart (left ventricular thrombusA blood clot formed within the left lower chamber of the heart.).[5]

How do they work?

Low molecular weight heparinA substance produced by the body, or given as medication, that reduces the likelihood of the blood to clot, coagulate. is around one third of the molecular weight of unfractionatedNot fractionated; that is, not divided up into separate parts. heparinA substance produced by the body, or given as medication, that reduces the likelihood of the blood to clot, coagulate.. This means that it is more readily taken up by the body after injection. Unlike unfractionatedNot fractionated; that is, not divided up into separate parts. heparinA substance produced by the body, or given as medication, that reduces the likelihood of the blood to clot, coagulate., it does not require continual monitoring.[5]

Another newer class of anticoagulants is a group of drugs called pentasaccharides. These selectively inhibit one of the proteins (coagulation factorsA group of substances that can undergo a cascade of reactions in certain conditions, leading to the coagulation of blood. Also known as clotting factors.) that help the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. to clot.  Thrombin is a substance in the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. that usually causes platelets to cluster together (aggregate), helping to form a bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. clot. Taking these medicines reduces the formation of thrombinAn enzyme that converts fibrinogen to fibrin during blood coagulation. and thus reduces bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. clotting.

Finally, direct thrombinAn enzyme that converts fibrinogen to fibrin during blood coagulation. inhibitors inactivate thrombinAn enzyme that converts fibrinogen to fibrin during blood coagulation. and also directly prevent plateletStructure in the blood that helps the blood to clot. aggregation.[5]

Who are they for?

As noted above, anticoagulants are given alongside clot-busting drugs in the treatment of heart attacks, to help maintain bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow through the coronaryRelating to the arteries supplying the heart itself. arteries.

What stage of development has been reached?

Low molecular weight heparinA substance produced by the body, or given as medication, that reduces the likelihood of the blood to clot, coagulate. has the best evidence to support its use. It is thought that direct thrombinAn enzyme that converts fibrinogen to fibrin during blood coagulation. inhibitors may have benefits in those who have angioplastyThe mechanical widening or clearing of a narrowed or obstructed blood vessel, performed during angiography, which is used to help with visibility. (the mechanical widening or clearing of a blocked arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. of the heart). However, further trials are needed.[5]

Ischaemic postconditioning

What is it?

Ischaemic postconditioning is a therapy that aims to limit the extent of damage to the heart muscleTissue made up of cells that can contract to bring about movement. following a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction.. This therapy is given after the onset of a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction., or during the process of restoring bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow through the coronaryRelating to the arteries supplying the heart itself. arteries. Usually, ischaemic postconditioningA therapy that aims to limit the extent of damage to the heart following a heart attack. The restoration of blood flow through the affected artery is briefly interrupted several times during angioplasty. is done when someone is undergoing angioplastyThe mechanical widening or clearing of a narrowed or obstructed blood vessel, performed during angiography, which is used to help with visibility. as the first treatment for their heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. (this is known as primary angioplastyThe mechanical widening or clearing of a narrowed or obstructed blood vessel, performed during angiography, which is used to help with visibility.).[6] One way to do this is by inflating and deflating an angioplastyThe mechanical widening or clearing of a narrowed or obstructed blood vessel, performed during angiography, which is used to help with visibility. balloon within the arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood., so that an artificial blockage within the arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. is effectively alternated with free bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow.[7]How does it work?
Sometimes, sudden restoration of bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow can itself cause injury to the heart, leading to inflammationThe body’s response to injury. and dysfunction of the heart muscleTissue made up of cells that can contract to bring about movement.. This is known as reperfusionRestoration of blood flow through a previously blocked vessel. injury and is difficult to treat because its underlying causes are multiple and complex.[7,8]

In early clinical studies, it was reported that after placing a stentA tube placed inside a tubular structure in the body, to keep it patent, that is, open. in the affected coronaryRelating to the arteries supplying the heart itself. arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood., an improvement in the overall restoration of bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow could be achieved by actually interrupting bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow, very briefly, several times. This seemed to reduce the size of damaged heart muscleTissue made up of cells that can contract to bring about movement. tissue, and an improvement was seen in the heart pump function after one year.

It seems that ischaemic postconditioningA therapy that aims to limit the extent of damage to the heart following a heart attack. The restoration of blood flow through the affected artery is briefly interrupted several times during angioplasty. helps to protect against reperfusionRestoration of blood flow through a previously blocked vessel. injury to the heart caused by the restoration of bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow [6]. It is thought that it does so by improving the function of the inner lining of the arteries (the endothelium), preventing the overload of calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions. within the cells and lessening inflammationThe body’s response to injury..[8]

Who is it for?

At the moment, this type of therapy is limited to people who have undergone a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. that is then treated with primary angioplastyThe mechanical widening or clearing of a narrowed or obstructed blood vessel, performed during angiography, which is used to help with visibility., rather than clot-busting (fibrinolyticA susbstance that can break down fibrin, the major component of blood clots.) therapy.[6]

What stage of development has been reached?

Additional studies are needed to determine whether ischaemic postconditioningA therapy that aims to limit the extent of damage to the heart following a heart attack. The restoration of blood flow through the affected artery is briefly interrupted several times during angioplasty. can be of value in the 'real world' rather than just in an experimental setting. Further research is being done into finding a way to apply ischaemic postconditioningA therapy that aims to limit the extent of damage to the heart following a heart attack. The restoration of blood flow through the affected artery is briefly interrupted several times during angioplasty. to people who do not undergo angioplastyThe mechanical widening or clearing of a narrowed or obstructed blood vessel, performed during angiography, which is used to help with visibility., so that those who have clot-busting drugs as a primary treatment after heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. may also enjoy the benefits of this therapy.[6]

References: 
  1. Weinsaft JW, Klem I and Judd RM. MRIAn abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field. for the assessment of myocardial viability. Cardiol Clin. 2007;25:35-56.
  2. Jaffer FA, Sosnovik DE, Nahrendorf M et al. Molecular imaging of myocardial infarctionDeath of an area of heart muscle due to poor blood supply.. Journal of Molecular and Cellular Cardiology. 2006;41:921-33.
  3. Martin-Rendon E, Brunskill SJ, Hyde CJ et al. Autologous bone marrowTissue within the bones where blood cells are formed. stem cells to treat acuteHas a sudden onset. myocardial infarctionDeath of an area of heart muscle due to poor blood supply.: a systematic review. European Heart Journal. 2008;29:1807-18.
  4. Lasala GP and Minguell JJ. Bone marrow-derived stem/progenitor cells: their use in clinical studies for the treatment of myocardial infarctionDeath of an area of heart muscle due to poor blood supply.. Heart, Lung and Circulation 2009;18:171-180.
  5. McCann CJ and Menown IBA. New anticoagulantA medication that prevens blood from clotting, or which reduces the likelihood of the blood to clot. strategies in ST elevation myocardial infarctionDeath of an area of heart muscle due to poor blood supply.: trials and clinical implications. Vascular Health and Risk Management. 2008;4:305-13.
  6. Hausenloy DJ and Yellon DM. Preconditioning and postconditioning: underlying mechanisms and clinical application. Atherosclerosis. 2009;204:334-41.
  7. Mockford KA, Girn HRS and Homer-Vanniasinkam S. Postconditioning: Current controversies and clinical implications. Eur J Vasc Endovasc Surg. 2009;37:437-42.
  8. Balakumar P, Rohilla A and Singh M. Pre-conditioning and postconditioning to limit ischemia-reperfusionRestoration of blood flow through a previously blocked vessel.-induced myocardial injury. What could be the next footstep? Pharmacological Research. 2008; 57:403-12.