Evaluation of total-LDH / heat resistant- LDH ratio in patients with acute myocardial infarction and unstable pectoral angina

Measurement of serum enzymes levels, such as lactate dehydrogenaze (LDH) and its isoenzymes is a routine way for diagnosis of myocardial infarction. One of these isoenzymes is LDH-1 which is raised after myocardial infarction. The purpose of this study was to evaluate total-LDH / heat resistant- LDH ratio in patients with acute myocardial infarction and unstable pectoral angina. In an descriptive analitical study 220 patients with suspected myocardial infarction (MI) or unstable pectoral angina (UA), hospitalized in CCU ward of Ekbatan Hospital in Hamedan city were studied. Using WHOs criteria, 110 were classified as having myocardial infarction and 110 as having unstable pectoral angina. The serum level of total-LDH and heat resistant- LDH was measured by NADH exchange method, 24 to 48 hours after their admission to the hospital. Data were analyzed by student-t test and Mann-Witheny test. Our study showed that total-LDH / heat resistant- LDH ratio in MI patients was 1.27±0.18 and it was 2.51±1.39 in UA patients (P<0.001). In our study, we found that when total LDH/ heat resistant- LDH ratio is decreased the severity of myocardial infarction (number of involved leads) and creatine phosphokinase (CPK) is increased (P<0.01). We did not find any relationship between total LDH/ heat resistant- LDH ratio with sex, age, type of MI (Q-wave & Non Q-wave), block after MI and arrhythmia following MI. Our results revealed that measuring heat resistant- LDH can be used as a method for accurate diagnosis of MI. This simple method can be used in centers where other accurate tests are not available.