Criteria For Inferior Myocardial Infarction Research Articles

A New Method of Interpreting the Electrocardiogram

The electrocardiogram (EKG) is one of the most widely used diagnostic tests in clinical medicine and is generally considered to be an excellent means of detecting many important cardiac abnormalities. However, when the EKG is interpreted in the traditional manner, its diagnostic performance is not as good as clinicians might wish. For example, a recent study showed that three sets of commonly used traditional EKG criteria for inferior myocardial infarction (MI) had such low sensitivities that they missed between 66% and 96% of the MIs that they were supposed to detect. 1 In contrast, three different sets of vectorcardiographic (VCG) criteria for inferior MI exhibited much better diagnostic performances. The investigators found that the superior performance of the VCG was due to its ability to display information about the contour of the pathway followed by the electrical forces of ventricular depolarization. Despite the reported advantages of the VCG, it is

Importance of the distance and velocity of electrical forces in the diagnosis of inferior wall healed myocardial infarction: A vectorcardiographic study

The vectorcardiograms of 41 patients with angiographically proved inferior myocardial infarction (MI) and 51 normal subjects were analyzed to determine whether it is the time (in milliseconds) or the distance (in millivolts) of the initial superiorly directed forces of ventricular depolarization that is increased more by inferior MI, and whether parameters derived from both the initial superior time and distance can be used to detect inferior MI. The 10 best individual and the 10 best paired criteria for inferior MI involve superior distance, either alone or used in the calculation of average velocity (in volts per second), and the product of initial superior time and distance (in millivolts per second). The 2 best individual criteria for inferior MI are: inferior velocity more than 0.0065 V/s (sensitivity 71%, specificity 100%) and superior distance more than 0.39 mV (sensitivity 68%, specificity 100%). These diagnostic performances are superior to those of the best criterion that involves only the duration of the initial superior forces, i.e., initial superior time longer than 28 ms (sensitivity 49%, specificity 98%) ( ξ 2 = 8.42, p < 0.005 and ξ 2 = 6.31, p < 0.025, respectively). Initial superior distance and parameters calculated from both initial superior distance and time are better vectorcardiographic criteria for inferior MI than are criteria that involve only initial superior time.

Importance of the terminal portion of the QRS in the electrocardiographic diagnosis of inferior myocardial infarction

The scalar electrocardiograms of 64 patients with inferior wall myocardial infarction (MI) and 87 normal subjects were quantitatively analyzed to determine the respective contributions of the initial and terminal portions of the QRS to the diagnosis of inferior Ml. Of the 10 best individual electrocardiographic criteria for inferior MI, 7 were Q-wave criteria and 3 were criteria that consisted of delayed termination of the QRS in leads II or III. Combining the best terminal QRS criterion (the QRS in lead III ending at least 20 ms later than the QRS in lead I) with the 7 best Q-wave criteria and the best Q-wave criterion (Q wave 40 ms or longer in lead aVF) with the 3 best terminal QRS criteria, resulted in criteria with better sensitivities and overall diagnostic performances than those of the individual criteria. Analyzing the vectorcardiograms that were also available in 26 of the patients with inferior MI and 34 of the normal subjects showed that the delayed inscription of the end of the QRS in leads II and III in patients with inferior MI is due to redirection of the terminal forces of ventricular depolarization. The terminal portions of the QRS complexes in the limb leads, considered both alone and in conjunction with traditional measurements of Q waves, contain information that is useful for diagnosing inferior MI.

Electrocardiographic criteria for the diagnosis of combined inferior myocardial infarction and left anterior hemiblock

New electrocardiographic (ECG) criteria for diagnosing the combination of inferior myocardial infarction and left anterior hemiblock are proposed. The proposed criteria are based upon the relations between portions of the vectorcardiographic QRS loop in the frontal plane and the corresponding portions of the QRS complexes recorded by the limb leads. The application of the proposed criteria requires that the tracings be obtained with 3-channel ECG machines. The proposed criteria for the diagnosis of inferior myocardial infarction and left anterior hemiblock are as follows: (1) leads aVR and aVL both end in R waves, with the peak of the terminal R wave in lead aVR occurring later than the peak of the terminal R wave in lead aVL, and (2) a Q wave of any magnitude is present in lead II. The performance of the proposed criteria was superior to that of 10 combinations of traditional ECG criteria for inferior myocardial infarction and left anterior hemiblock.

Polarcardiographic study of inferior myocardial infarction: Global projection of heart vector

The sensitivity of electrocardiographic, vectorcardiographic and polarcardiographic criteria for inferior myocardial infarction was studied. ECG and Frank system VCG were recorded in 50 normal cases and 40 cases of inferior myocardial infarction, whose acute phase was documented by typical electrocardiographic and serum enzymatic changes. The records were made from one month to 16 years after acute attacks. Polarcardiograms were obtained by a specially-designed analogue computer from X, Y and Z signals of the VCG, and recorded at a paper speed of 1000 mm/sec by Mingograph. The polarcardiographic tracings were measured at every 5 msec after onset of the QRS wave, and plotted on the Aitoff's equal-area projection. In normal cases, the QRS vectors plotted on Aitoff's projection passed through the narrow area between 15 to 35 msec after the QRS onset. Electrocardioraphic diagnosis of myocardial infarction was correctly made in 22 cases (55%), and by VCG the sensitivity was improved to 32 cases (80%). Polarcardiographic diagnosis was made in 33 cases (82.5%). Global plots of heart vector on Aitoff's projection were a useful display to visualize the sequential changes of heart vector. In inferior myocardial infarction, the QRS vector passed through the more superior portion to normal, and the diagnosis was accurately made in 33 cases (82.5%).

Re-evaluation of the vectorcardiographic criteria for inferior myocardial infarction. Correlation between vectorcardiograms and left ventriculograms.

In 72 patients satisfying the vectorcardiographic criteria described by Young et al, vectorcardiographic findings were compared between a group of patients with an inferior myocardial infarction and a false positive group to increase the specificity of the vectorcardiographic diagnosis of inferior myocardial infarction. The first group was composed of 18 cases, with angiographic findings of inferior myocardial infarction and the false positive group was composed of 54 cases which had no significant narrowing of coronary arteries. Vectorcardiographic parameters such as the angle between the X axis and maximal QRS vector, the duration of initial superior force, the maximal superior deviation (QY) and the maximal inferior deviation (RY) were analyzed and only QY and QY/RY showed statistically significant differences between the 2 groups. Of these two parameters, QY/RY indicated a more definite difference. In addition, the rate of false positive cases was reduced prominently if the criterion of QY/RY above or equal to 0.2 was added to the criteria of Young et al. The direction of the maximal T vector was downward in 2 cases (11%) in the inferior myocardial infarction group, but downward in 44 cases (81%) in the false positive group.