Evaluation of a QRS scoring system for estimating myocardial infarct size. VIII. Specificity in a control group with left ventricular hypertrophy and proposal of a new scoring system for use with this confounding factor.

Electrocardiographic differentiation between left ventricular hypertrophy (LVH) and myocardial infarction (MI) is often difficult because both diagnoses are based primarily on QRS changes on the electrocardiogram (ECG). The specific goal of this study was the development of ECG criteria that could be used with the complete Selvester QRS scoring system for MI size in patients with LVH. A study population of 127 patients had significant aortic valve disease verified by cardiac catheterization. Inclusion in the study required no significant coronary artery disease, no focal contraction abnormality on the left ventriculogram, and no documented MI. Quantitative criteria for LVH developed by Bonner (IBM) and also those developed by the Cornell group were used to determine the ECG evidence for LVH in each patient. One or both sets of criteria were met in 110 (87%) of the 127 patients. This group was compared to a previously evaluated control population of 500 normal subjects. The complete 54-criteria, 32-point QRS MI size scoring system was applied to the 12-lead ECG of both groups. The score was 98% specific in the normal controls and 73% specific in the LVH group using a score of greater than 3 points as diagnostic for MI. Of the 54 individual QRS criteria, 16 failed to achieve 95% specificity in the LVH population: 13 were for anterior (and apical), 2 for inferior, and 1 for posterior locations. Of these 16, minor modifications to 11 were sufficient to achieve the 95% specificity standard.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of serial QRS changes during acute inferior myocardial infarction using a QRS scoring system.

The evolution of changes in the QRS complex during the initial 3 days after the onset of an initial inferior myocardial infarction (MI) was studied in 82 consecutive patients. Each patient's standard 12-lead electrocardiogram was assigned points (a QRS score) according to the absolute duration of the Q and R waves and the amplitude ratios of R-to-Q and R-to-S waves. This QRS score has been demonstrated to correlate (r = 0.74) with the anatomic extent of single inferior MI. By this system, 43 patients (53% of the study group) had an initial electrocardiogram that registered a score of 0 and developed QRS points only after admission. The QRS scores of 18 additional patients (22% of the study group) changed after admission. Forty-nine score changes were noted on Day 2 and 18 on Day 3. All of these changes resulted in an increased QRS score. Alteration of the QRS complex during initial inferior MI evolves over 2 to 3 days in many patients. There is a distinct pattern to this evolution, which results in sequential increases in a QRS score based upon electrocardiographic indicators of the extent of myocardial necrosis. This QRS scoring system might be applied to evaluate clinically interventions aimed at limiting the extent of necrosis in patients with initial acute inferior MI.

Evaluation of a QRS scoring system for estimating myocardial infarct size. I. Specificity and observer agreement.

We evaluated a simplified version of a previously developed QRS scoring system for estimating infarct size using observations of Q- and R-wave durations and R/Q and R/S amplitude ratios in the standard 12-lead ECG. Groups of subjects with a minimal likelihood of having myocardial infarcts and minimal likelihood of having common noninfarction sources of QRS modification were studied to establish the specificity of each of the 37 criteria. Only two criteria required modification to achieve 95% specificity. These 37 criteria form the basis of a 29-point QRS scoring system. A 98% specificity was achieved when a score of more than 2 points was required to identify a myocardial infarct. Fifty patients were studied to determine the intra- and interobserver agreement with this scoring system. Each criterion achieved at least 91% intra- and interobserver agreement. These impressive levels of specificity and observer agreement must be matched by high sensitivity of the scoring system and a good correlation between the point score and infarct size in patients with proven infarcts if the point score is to be useful for detecting and sizing infarcts. Sensitivity and correlation between point score and infarct size are evaluated in later studies in this series. The standard ECG is inexpensive and can be obtained repetitively and noninvasively; its QRS complex may be an important means of estimating the size, presence and location of myocardial infarcts.