Today’s post on the Medical Technology Blog come from Medical Industry Week, Espicom’s current business publication on the medical industry, please read on…

Researchers from Loyola University Chicago Stritch School of Medicine have discovered a possible new blood test to help diagnose heart attacks.

Featured within the Journal of Molecular and Cellular Cardiology, the investigators provided details of a large protein known as cardiac myosin binding protein-C (cMyBP-C), which is released to the blood following a heart attack. Senior author, Dr Sakthivel Sadayappan, believes this could potentially become the basis for a new test, used in conjunction with other blood tests, to help diagnose heart attacks, however, additional studies will be necessary to establish cMyBP-C as a true biomarker for heart attacks.

Between 60 and 70 per cent of all patients who complain of chest pain do not have heart attacks. Many of these patients are admitted to the hospital, at considerable time and expense, until a heart attack is definitively ruled out. An electrocardiogram can diagnose major heart attacks, but not minor ones. There are also blood tests for various proteins associated with heart attacks, but most of these proteins are not specific to the heart. Elevated levels could indicate a problem other than a heart attack, such as a muscle injury. Only one protein now used in blood tests, called cardiac troponin-I, is specific to the heart, however, it takes at least four to six hours for this protein to show up in the blood following a heart attack.

 The Loyola study is the first to find that cMyBP-C is associated with heart attacks. The researchers evaluated blood samples from heart attack patients, and also evaluated rats that had experienced heart attacks. They found that in both humans and rats, cMyBP-C was significantly elevated following heart attacks. cMyBP-C is a large assembly protein that stabilises heart muscle structure and regulates cardiac function. During a heart attack, a coronary artery is blocked, and heart muscle cells begin to die due to lack of blood flow and oxygen. As heart cells die, cMyPB-C breaks into fragments and is released into the blood. Future studies would determine the time course of release, peak concentrations and half life in the circulatory system. Sadayappan holds a provisional patent to determine the risk factors associated with cMyBP-C degradation and release into human body fluid.

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This weeks artice on the Medical Technology Blog is taken fromEspicom’s business publication, Cardiovascular Device Business, please read on…

In a paper published in the September issue of the Biophysical Journal, lead author Dr Oscar Abilez, a postdoctoral scholar and PhD candidate in bioengineering, and a multidisciplinary team from Stanford University, describe how they have, for the first time, engineered human heart cells that can be paced with light using a technology called optogenetics. In the near term, the researchers say the advance will provide new insight into heart function. In the long term, however, the development could lead to an era of light-based pacemakers and genetically matched tissue patches that replace muscle damaged by a heart attack.

To create the light-responsive heart cells, the researchers first inserted DNA encoding a light-sensitive protein called channelrhodopsin-2 (ChR2), into human embryonic stem cells. ChR2 controls the flow of electrically charged ions into the cell. For heart cells, the primary ion is sodium, which initiates an electrochemical cascade that causes the cell to contract. They then transformed the optogenetically engineered stem cells into cardiomyocytes those that respond to light.

The key protein for the experiment is ChR2, which is sensitive to a very specific wavelength of blue light and regulates tiny channels in the cell surface. When ChR2 is illuminated by the right wavelength of blue light, the channels open to allow an influx of electrically-charged sodium into the cell, producing a contraction. After creating the cells in a laboratory dish, the researchers tested their new cells in a computer simulation of the human heart, injecting the light-sensitive cells in various locations in the heart and shining a virtual blue light on them to observe how the injections affected contraction as it moved across the heart.

In a real heart, the pacemaking cells are on the top of the heart and the contraction radiates down and around the heart. With these models, the researchers say they can demonstrate not only that pacing cells with light will work, but also where to best inject cells to produce the optimal contraction pattern.

The long-term goal is the development of a new class of pacemakers. At present, surgically-implanted electrical pacemakers and defibrillators are commonplace, regulating the pulses of millions of faulty hearts around the world. However, Abilez adds that neither is without problems – pacemakers fail mechanically and the electrodes can cause tissue damage. Defibrillators, on the other hand, can produce tissue damage due to the large electrical impulses that are sometimes needed to restore the heart’s normal rhythm. In the future, the researchers envision that bioengineers will use induced pluripotent stem cells fashioned from the recipient’s own body, or similar cell types that can give rise to genetically matched replacement heart cells paced with light, circumventing the drawbacks of electrical pacemakers.

Co-author, Dr Christopher Zarins, professor emeritus of surgery and director of the lab, speculates the the work could result in a pacemaker that is not in physical contact with the heart. Instead of surgically implanting a device that has electrodes poking into the heart, engineered light-sensitive cells would be injected into the faulty heart and used to pace the heart remotely with light, possibly even from outside of the heart. The leads for such a light-based pacemaker might be placed outside the heart, but inside the pericardium, the protective sack surrounding the heart. Another concept to be explored is a pacemaker placed inside the heart chambers, as with traditional pacemakers, whose light can travel through the intervening blood to pace light-sensitive heart cells implanted inside. Since the new heart cells are created from the host’s own stem cells, they would be a perfect genetic match.

The authors conclude that optogenetics could also lead to advances beyond the heart. It might lead to new insights for various neuronal, musculoskeletal, pancreatic and cardiac disorders, including depression, schizophrenia, cerebral palsy, paralysis, diabetes, pain syndromes and cardiac arrhythmias.

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Welcome back to The Medical Technology blog. My apologies for the lack of posts last week, but I  was extremely busy updating Espicom’s main website. Please read on….

Interesting news has come this week from a study funded by the FDA’s Agency for Healthcare Research and Quality (AHRQ) which gives qualified backing to the adoption of percutaneous heart valve replacement (PVR) procedures in preference to open heart surgery

The report, produced by the Duke Evidence-based Practice Center for AHRQ and published online in the Annals of Internal Medicine, found that PVR, a minimally-invasive procedure in which a replacement valve is implanted through a catheter rather than by open heart surgery, is a realistic option for some patients with heart valve disease, especially older or sicker patients.

The report concluded that this form of heart valve replacement may be a safe and effective alternative to open heart surgery, especially in the short term, for this patient group. However, the FDA body maintains that information is lacking on the potential long-term benefits and risks of this procedure, particularly compared with open heart valve replacement surgery.

In this study, approximately 92 per cent of patients who received a percutaneous valve survived the procedure, of which 86 per cent survived for at least 30 days. The authors looked at 62 published studies representing a total of 856 patients, as well as additional studies that have not yet been published. However, researchers were unable to make direct comparisons between percutaneous valves and traditional surgical replacement due to differences between patient groups receiving the treatments.

In total, seven percutaneous valves were featured in the study, namely the Sapien transcatheter heart valve (Edwards), CoreValve ReValving system, Melody heart valve (Medtronic), Paniagu heart valve (Endoluminal Technology Research), Lotus valve (Sadra Medical) and Ventor Embracer (Ventor Technologies). This particular study didn’t look at the comparative performance of the devices, leaving that to be revealed through other studies currently in progress in the US. The AHRQ argues that there are plenty of comparative “mine’s better than yours” studies but little in the way of  observational studies and decision modelling that could help inform clinical and health policy in the absence of randomised control trials.

It’s an important question since, as with most of the developed world, the US population  proportion of older adults continues to increase, bring with it higher incidences of degenerative heart valve disease. Calcific aortic stenosis (narrowing) and ischaemic and degenerative mitral regurgitation (leakage) are the most common valvular disorders in adults aged 70 years and older.

Mechanical and, more latterly, bioprosthetic heart valves, have radically transformed the way in which we treat patients with heart disease. The urgent need now is to make sure that includes policymakers, decision makers for third-party payers, clinicians, patients and investigators, get the right form of information.

Thanks for reading, and come back soon, Paul.