Are electrocardiographic Q-wave criteria reliable for diagnosis of perioperative myocardial infarction after coronary surgery?
OBJECTIVE
A major assumption in cardiovascular medicine is that Q-waves on the electrocardiogram indicate major myocardial tissue damage. The appearance of a new Q-wave has therefore been considered the most reliable criterion for diagnosis of perioperative myocardial infarction (PMI) in cardiac surgery. In a study, originally intended to evaluate troponin-T as a marker of PMI, analysis of our data aroused the need to address the reliability of Q-wave criteria for diagnosis of PMI.


METHODS
In 302 consecutive patients undergoing coronary surgery, Q-wave and other electrocardiogram (ECG) criteria were compared with biochemical markers of myocardial injury and the postoperative course. All ECGs were analysed by a cardiologist blinded to the biochemical analyses and the clinical course.


RESULTS
The incidence of positive Q-wave criteria was 8.1%. Combined biochemical (CK-MB > or = 70 microg/l) and Q-wave criteria were found in 1.0%. Patients with new Q-waves did not have CK-MB or troponin-T levels significantly different from those without Q-waves. More than 25% of the Q-waves were associated with plasma troponin-T below the reference level (< 0.2 microg/l) on the fourth postoperative day. Q-wave criteria alone did not influence the postoperative course. In contrast, biochemical markers correlated with clinical outcome.


CONCLUSIONS
The majority of Q-waves appearing after coronary surgery were not associated with major myocardial tissue damage, and according to troponin-T one-fourth of the Q-waves were not associated with myocardial necrosis. Furthermore, the appearance of Q-waves had little influence on short term clinical outcome. Therefore, the use of Q-wave criteria as the gold standard for diagnosis of PMI may have to be questioned.
Svedjeholm
R
R
Department of Cardiothoracic Surgery, Linköping Heart Center, University Hospital, Sweden. rolf.svedjeholm@thx.us.lio.se
Dahlin
L G
LG
Lundberg
C
C
Szabo
Z
Z
Kågedal
B
B
Nylander
E
E
Olin
C
C
Rutberg
H
H
D000368:Aged; D006348:Cardiac Surgical Procedures; D003402:Creatine Kinase / Q000097:blood; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007431:Intraoperative Complications; D007527:Isoenzymes; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000175:diagnosis*; D011183:Postoperative Complications / Q000175:diagnosis*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D014336:Troponin / Q000097:blood; D020107:Troponin T
D007527:Isoenzymes; D014336:Troponin; D020107:Troponin T; D003402:Creatine Kinase