(RxWiki News) A typical heart attack comes on suddenly and is easily diagnosed. Another type of heart attack that can occur after a heart procedure, however, may need to be better defined.
Doctors can identify a typical heart attack with results from an electrocardiogram — which records the electrical activity in the heart — and by an increase in a heart muscle protein in the blood. When patients have procedures to restore blood flow to clogged arteries, they are often identified as having had a heart attack if they simply have a small rise in this heart muscle protein.
Recently, a panel of heart experts has proposed a new definition for heart attack in these patients. The new criteria are intended to help identify true heart complications and reduce unnecessary procedures and testing.
"Ask a doctor about how to best diagnose heart attack."
Issam Moussa, MD, chair of the Division of Cardiovascular Diseases at Mayo Clinic Florida in Jacksonville, and other members of The Society for Cardiovascular Angiography and Interventions (SCAI) issued a new definition for identifying patients who've had a heart attack after coronary angioplasty or bypass surgery.
Under the current definition, a heart attack is diagnosed by a relatively small rise in the blood level of a protein called cardiac troponin. The increase has to be at least five times the normal level. This measure is used along with confirmation by an electrocardiogram, an imaging test or symptoms.
Under the existing criteria, doctors can detect minimal heart damage from small protein leaks from the heart muscle. This minimal heart damage, however, does not necessarily reflect a patient’s likelihood for survival or having another heart attack.
Based on these miniscule increases in troponin, patients who have undergone heart procedures have been kept in hospitals for longer stretches than may have been necessary. Some have undergone additional screenings and blood tests that may not have been required, according to the authors.
SCAI is now recommending that most of these post-procedure heart attacks be identified by a large increase in the blood of a protein called CK-MB (to at least 10 times the normal level).
If CK-MB is not available, then Dr. Moussa and his colleagues would like to see a troponin level that is 70 times normal — not the current 10 times — to diagnose a heart attack.
If the ECG measures give strong evidence of a heart attack, then the new definition establishes that blood levels of CK-MB and troponin can be five times and 35 times normal, respectively, to diagnose heart attack.
“If you tell a patient, ‘You have had a heart attack,’ it should mean something about clinical outcomes, not microscopic injury to the heart muscle,” Dr. Moussa said in a press release.
The new definition stresses that diagnosis would focus on CK-MB levels, which may provide a better indication of future cardiac events, rather than changes in troponin levels in patients who have had stenting or bypass surgery. Diagnosis would also be more uniform for both bypass surgery and angioplasty.
“This is an important study and is likely to help us better understand what is more likely to represent a meaningful clinical cardiac event after certain types of cardiac procedures and surgeries," said Mohan Sathyamoorthy, MD, Chief of the Cardiovascular Division at Baylor All Saints Medical Center.
"Cardiac procedures such as coronary angioplasty and stenting, or any type of cardiac surgery, are expected to cause a certain amount of elevation in laboratory tests called cardiac biomarkers. Current definitions may term these expected elevations in these cardiac biomarkers a 'heart attack', when in reality, they are not. Furthermore, calling these expected elevations 'heart attacks' may prompt further clinical testing and interventions that fundamentally may not be necessary or helpful," said Dr. Sathyamoorthy, who was not involved in this study.
"The new definitions proposed in this study should lessen the degree of concern related to post-procedural elevations in these laboratory tests called cardiac biomarkers. This may then very well help us utilize resources more effectively in managing patients after these types of cardiac procedures.”
In a statement, Dr. Moussa added, “This definition of heart attack would better identify those patients with true complications after angioplasty or bypass surgery who require urgent action, better reflect the quality of these procedures and inform future research designed to identify the best preventive strategies.”
This position paper was published online and in the October 22 issue of the Journal of the American College of Cardiology.