THE AMBASSADORS
Health Supplement
THE AMBASSADORS
Health
Supplement
BOOK REVIEW
Volume 1,
Issues 3
November 1998
Myocardial
Damage:
Early detection by novel
biochemical markers.
Ed. Juan Carlos Kaski and David W. Holt
Kluwer Academic Publishers Dordrecht, Boston, London (1998)
This 214-page illustrated book is highly commended as a well-designed vade mecum for those in the challenging fields of cardiology and the ancillary laboratory services.
When faced with a patient complaining of acute
chest pain, even today's internists and cardiologists at times
find it difficult to decide
whether it might be due to an acute myocardial
infarction [AMI], angina or simply non-cardiac pain. This problem
becomes even more relevant in the hectic atmosphere of a busy
district general hospital with a bed shortage. Always foremost in
the mind of the hard-pressed treating physician is the
possibility of missing a diagnosis. For fear of this, one tends
to err on the side of caution, and this must lead to the
unnecessary admission of patients who do not have AMI.
This is the easy way of solving the problem, but the drawback is that it also causes adverse effects with respect to the social, economic and psychological aspects of such a situation. In addition to a clear history, a twelve-lead resting electrocardiogram [ECG] does indeed aid in the diagnosis of AMI in about 55% - 75% of such cases [reaching 80% when serial ECG's are recorded]. The biochemical tests such as CK, CK-MB, AST and LDH are time-consuming and at times unhelpful. Does biochemistry have something somewhat more substantial to offer? There are indeed some novel Biochemical Markers, which offer advantages of substance.
This brings us to Juan Kaski and David Holt of
St. George's Hospital Medical School, London, UK, the editors of
'Myocardial Damage'. Their book addresses this issue with 17
essays on the subject all written by internationally known
experts in the field. They have all written readable, concise,
comprehensive and informative chapters on various aspects of the
subject of the myocardial infarction, related conditions and
their diagnosis. Each chapter is followed by adequate and timely
references.
Not only have they described clearly the benefits of the estimation of CK, CKMB, myoglobin [admittedly not a novel marker], troponin T, troponin I, glycogen phosphorylase isoenzyme BB and fatty acid binding proteins in the diagnosis of AMI and angina, they have also outlined their prognostic values in ischaemic heart disease. In addition, the method of assessing infarct size is described. How they aid in determining the success or otherwise of post thrombolytic therapy is covered as is their usefulness in monitoring the post-cardiac transplant situation.
In their evaluation of the role of Troponins T and I in coronary artery disease Frey, Muller-Bardorff and Katus [chapter 3] suggest that these have "become the markers of choice in patients with suspected acute coronary syndromes". In cases where there are definite cardiac enzyme or ECG findings sufficient for the diagnosis of AMI they are not required. Moreover, the troponins can also be used to rule out acute myocardial infarction in patients with chest pain.
The drawback with the troponins and other such markers is that they rarely enter the blood in significant levels until 3 or 4 hours post-infarction. Johannes Mair's chapter [5] on myoglobin, [17.6 kD], which can enter the blood within the first two hours or so, notes that this non-specific marker of coronary artery disease crises is very useful both to rule out AMI, and, in many cases also to rule it in.
In the discussion by Mair, Puschendorf and Krause of the glycogen phosphorylase isoenzyme BB, an isoenzyme found predominantly in brain and heart, but not in significant levels in skeletal muscle, they note that ischaemia triggers this substance to alter from being part of a large insoluble complex to become a soluble entity present in the cytosol. The monomer is 94 Kd in size. Changes in plasma membrane permeability, which occur during ischaemia, allow its early [within 2 to 3 hours] escape into the interstitial fluid and the vascular compartment.
Even smaller than myoglobin at 14-15 kD, fatty acid binding proteins [FABPs] are discussed by Jan Glatz in chapter 7. Their main function is the binding of long chain fatty acids which would otherwise be found free in the cytosol or bound, perhaps detrimentally, to other proteins and the like. These ubiquitous specialized binding proteins are labeled according to the tissue in which they we first discovered, but they are by no means restricted to that location [H-FABP from the heart is also found in skeletal muscle, smooth muscle, parts of the brain, kidney, stomach, lung, etc.] After muscle injury the release of FABPs is similar to that of myoglobin. Although FABPs released after cardiac cell injury are not cardiospecific, H-FABP is found in skeletal muscle in relatively small amounts. This and the fact that plasma reference intervals for FABP are quite low may give it an advantage over myoglobin as a marker protein for AMI and related conditions.
The economic advantages and limitations of these and other markers are discussed. Their use in clinical research and clinical trials is described, with helpful figures and running charts. It is too early to say just how practical these tests may be for a general hospital or clinical laboratory or how adaptable they may be to the day-to-day running of a Casualty or Cardiac Care Unit, and their economic implications require further study. However, this book is nonetheless a valuable source of information to those internists, cardiologists and biochemists who deal with coronary artery disease.
It is also a helpful guide for those in the field of research and those conducting clinical trials in coronary artery disease. Residents and postgraduates will garner a good deal of recently acquired knowledge on current advances in the use of novel markers in coronary artery disease.
Reviewed by M. S.
Basharatullah, MD, FACP, FRCP (I), FRCP (Glasgow),
Consultant Cardiologist and Head of Al-Adan
Hospital Coronary Care Unit,
and David L Wright. Ph.D., FCACB, Senior
Consultant Biochemist, Al-Adan
Laboratories, Kuwait.
