Nancy B. Wagner

Use of initial ST-segment deviation for prediction of final electrocardiographic size of acute myocardial infarcts

The decision to administer thrombolytic therapy for limitation of acute myocardial infarction (AMI) size must occur when only the history, physical examination and 12-lead electrocardiogram of a patient are available. A method that could quickly assess the amount of jeopardized myocardium would greatly aid the physician. This study developed formulas from 68 anterior and 80 inferior AMI patients using the extent of initial ST-segment deviation (ST delta) to predict the final AMI size estimated by the Selvester QRS score in a population not receiving reperfusion therapy. Inclusion required: initial anterior or inferior AMI; admission electrocardiogram less than or equal to 8 hours after the onset of symptoms with evidence of epicardial injury; elevated creatine kinase-MB; a predischarge electrocardiogram taken greater than or equal to 72 hours after admission; and no AMI extension before the predischarge electrocardiogram. The extent of epicardial injury was quantified by counting the number of leads with greater than or equal to 0.1 mm ST delta, by the sum (sigma) of ST delta in all leads and by the sigma ST delta in the lead groups associated with each AMI location. These results were compared to the AMI size estimated from the predischarge electrocardiogram. Univariable and multivariable analyses generated these formulas for AMI size: anterior = 3[1.5 (number leads ST increases) - 0.4]; inferior = 3[0.6 (sigma ST increases II, III, aVF) + 2.0]. Thus, formulas based on quantitative measurements of ST delta on the admission electrocardiogram are predictive of final QRS-estimated AMI size, and may be useful in determining the efficacy of acute reperfusion therapy.

The portable programmable microprocessor-driven real-time 12-lead electrocardiographic monitor: A preliminary report of a new device for the noninvasive detection of successful reperfusion or silent coronary reocclusion

Successful intravenous thrombolytic therapy early in myocardial infraction has the potential to reduce patient mortality without the additional risk and cost of aggressive invasive therapy. Noninvasive detection of successful reperfusion using resolution of chest pain, ST-segment changes assessed on static electrocardiograms, arrhythmia evolution, early isoenzyme peaking or changes in ventricular perfusion or function has been hampered by poor sensitivity or specificity, or inability to provide timely information. A newly available portable programmable microprocessor-driven real-time 12-lead electrocardiographic monitor has been introduced that may address these limitations. A continuously updated precise digital record of ST-segment activity at the bedside provides valuable information both in monitoring patients during reperfusion therapy to determine the efficacy of such treatment and in the subsequent hours to signal threatened reocclusion. This report describes the salient features of the monitor and presents 4 distinct situations in which the monitor detected timely information regarding coronary patency after reperfusion.

Evaluation of a QRS scoring system for estimating myocardial infarct size. VI: Identification of screening criteria for non-acute myocardial infarcts

Each of the 54 criteria in the Selvester 32-point QRS scoring system for estimation of myocardial infarct (MI) size has attained greater than or equal to 95% specificity in normal subjects. This study was performed to identify a subset of those criteria with cumulative specificity greater than or equal to 95% and maximal sensitivity for use in screening for the presence of non-acute MI. Coronary angiography and left ventriculography were used to identify 500 normal subjects, 60 patients with isolated anterior MI and 62 patients with isolated inferior MI. Patients with the QRS confounding factors of ventricular hypertrophy, fascicular block or bundle branch block on their electrocardiogram were not included. Using stepwise logistic regression analysis, the screening criteria identified were: (1) Q greater than or equal to 30 ms in aVF, (2) R less than or equal to 10 ms and less than or equal to 0.1 mV in V2 and (3) R greater than or equal to 40 ms in V1. Cumulatively, these 3 screening criteria achieved 84% and 77% sensitivities for inferior and anterior MI groups, respectively. Thus, a set of 3 criteria from the Selvester QRS scoring system is capable of identifying single non-acute anterior or inferior MI in 80% of patients, and falsely indicating presence of MI in only 5% of normal subjects.

Evaluation of changes in standard electrocardiographic QRS waveforms recorded from activity-compatible proximal limb lead positions

Proximal limb lead positions are currently used for activity-compatible electrocardiographic monitoring of myocardial ischemia. Two previously described systems for alternate limb lead placement were studied in patients with and without QRS evidence of healed anterior or inferior myocardial infarction. An innovative method was used to simultaneously record 6 standard and 6 modified limb leads, and 3 standard and 3 modified precordial leads on a standard digital electrocardiograph. Both alternate lead placement systems showed rightward frontal plane axis shift and diminished Q-wave durations in lead aVF compared with those of their simultaneous standard controls. Furthermore, potential differences between the standard distal limb lead sites and 5 more proximal sites were explored along each limb. Differences along the left arm were accentuated relative to those along the right arm owing to differences in proximity of the arms to the myocardium. Along the lower limb, and anterior site showed less deviation from standard than did a more lateral site. It is imperative that recordings from alternate sites be labeled accordingly so that their output cannot be confused with that obtained from standard sites.

An electrocardiographic acuteness score for quantifying the timing of a myocardial infarction to guide decisions regarding reperfusion therapy.

Abstract The method of determining the acuteness score presented in the present study is suggested for use in automated electrocardiographic analysis systems. A potential use of the acuteness score is in combination with historical timing as a guideline for decisions regarding thrombolytic therapy. Patients with an acuteness score above a certain threshold and a brief time from symptom onset may benefit most from thrombolytic therapy. The relation between the levels of acuteness score and the quantity of myocardium salvaged was not determined in the present study because no measure of salvage was available in this population. A future study is suggested in which this relation is determined. An additional use of the acuteness score may be to assess myocardial reperfusion and salvage by examining the time course of progression in score between the ECGs before and sequentially after administration of thrombolytic therapy.

Anatomic validation of electrocardiographic estimation of the size of acute or healed myocardial infarcts.

Seventeen new criteria added to the simplified version of the Selvester QRS scoring system to comprise the complete version were evaluated to determine their value in estimating the size of single infarcts. These non-Q-wave criteria might be particularly useful regarding posterolateral infarcts in the distribution of the left circumflex artery. The study population was made up of 21 anterior, 30 inferior and 20 posterolateral single myocardial infarction (MI) patients with no evidences of bundle branch or fascicular blocks, ventricular hypertrophy or previous MI on their final stable electrocardiogram. The complete systems maximum 32 points is capable of indicating MI in 96% of the left ventricle and it estimated a mean electrocardiographic MI size that better approximated the anatomic size compared with the simplified version in all MI locations. The correlation between anatomic and electrocardiographic MI size using the complete system was better and statistically significant for the posterolateral MI group (simplified r = 0.55, p less than 0.01 vs complete r = 0.70, p less than 0.0006). Criteria such as Q and S amplitude less than or equal to 0.3 mV in V1 and less than or equal to 0.4 mV in V2 were particularly helpful. This study documents the improved ability provided by the 17 additional non-Q-wave criteria which have been added in the complete version of this scoring system regarding the sizing of infarcts in the region of the left ventricle supplied by the left circumflex artery.

T wave amplitudes in normal populations: Variation with ECG lead, sex, and age

Consideration of increased T wave amplitude (tall T waves), either alone or in association with other electrocardiographic (ECG) parameters, may be beneficial for the early detection of acute transmural ischemia, and quantification of the increase might be used in quantifying the ischemic area. The primary purpose of this study was to quantify normal T wave amplitude limits according to ECG lead, sex, and age. One thousand nine hundred thirty-five subjects in two normal populations were analyzed, and the 98th percentile of the positive T wave amplitude for each ECG lead (including -aVR) was considered the upper limit of normal. Normal T wave amplitude was two times greater in the precordial than in the limb leads, and it was approximately 25% greater in men than in women in all leads. There was approximately a 10% decrease in normal T wave amplitude between 18-39- and 40-59-year-old patients and a 15% decrease between 40-59- and 60-79-year-old patients. The upper limit of normal T wave amplitudes identified in this study confirm those developed by Lepeschkin for use as means for each lead when age and sex are not considered. These limits might be incorporated into both normograms and automated ECG analysis systems to determine the presence or absence of tall T waves in patients presenting with symptoms of acute transmural ischemia.

Importance of early and complete reperfusion to achieve myocardial salvage after thrombolysis in acute myocardial infarction

The importance of the timing and completeness of coronary artery reperfusion for limitation of acute myocardial infarction (AMI) size after intravenous thrombolytic therapy was studied in 39 patients. All had electrocardiographic epicardial injury and acute coronary angiography performed < 8 hours after symptom onset. Acutely jeopardized myocardium was estimated at baseline, and before and after angiography by quantitative ST-segment analysis. The AMI size was estimated on the final electrocardiogram by the Selvester QRS score. Left ventricular ejection fraction was measured at the time of acute angiography and before discharge in 31 of these patients. In the 21 patients with normal flow (Thrombolysis in Myocardial Infarction [TIMI] trial grade 3) in the infarct-related artery, the amount of jeopardized myocardium decreased from baseline to that before and after angiography (17 to 11 and 11%, respectively; p < 0.00005), and the median final AMI size was reduced (17 to 9%; p = 0.0004). In 6 patients with suboptimal flow (TIMI grade 2), the median amount of jeopardized myocardium decreased slightly from baseline to that before to after angiography (15 to 12%); however, the median final AMI size was not reduced (17%). In 12 patients with no reperfusion (TIMI 0 to 1) flow, the median amount of jeopardized myocardium remained unchanged from baseline to that before angiography (21%), and the final AMI size was not significantly reduced. There was a significant inverse correlation between the change in global left ventricular function and the difference between electrocardiographic estimated jeopardized and final AMI size (rs = -0.53; p = 0.008).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of intravenous streptokinase on the relation between initial ST-predicted size and final QRS-estimated size of acute myocardial infarcts

Thrombolytic therapy has been documented to reduce acute myocardial infarct size. The previously established relation between initial ST segment elevation and final electrocardiographic (ECG) myocardial infarct size in patients without coronary reperfusion might therefore be altered by thrombolytic therapy. The effect of intravenous streptokinase on this relation was therefore studied in 73 patients with initial acute myocardial infarction who had participated in the Second International Study of Infarct Survival (ISIS-2). Patients who received streptokinase were considered as one group and patients who did not receive streptokinase as a control group. Final myocardial infarct size, which was estimated from the QRS score, was predicted from the admission standard ECG by previously developed formulas based on ST segment elevation. In the 40 control patients there was no change from ST-predicted to final QRS-estimated infarct size (median 17.7% versus 18.3%; p = NS). In the 33 patients in the streptokinase group, there was a highly significant decrease from predicted to final myocardial infarct size (median 21.9% versus 16.2%; p less than 0.0002). This decrease was found for both anterior (median 23.7% versus 19.5%; p less than 0.03) and inferior (median 21.9% versus 12.0%; p = 0.001) infarct locations. Multiple regression analysis adjusting for differences in predicted infarct size confirmed the significance of streptokinase on the difference in infarct size (p = 0.006). Based on the variability of the percent change from predicted to final infarct size in the control group, a threshold decrease greater than or equal to 20% is required for identification of salvage.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic use of a qrs scoring system after hospital discharge for initial acute myocardial infarction in the framingham cohort

Myocardial infarct size is an important risk factor for survival after acute myocardial infarction (AMI). The purpose of this study was to determine the prognostic value of myocardial infarct size, as estimated by the Selvester 54-criteria/32-point QRS scoring system, in the Framingham cohort. During the first 30 years of the Framingham Heart Study, a total of 384 participants developed an AMI requiring hospitalization; from this group, 243 patients met the following inclusion criteria: (1) no electrocardiographic changes due to a previous infarction, (2) survival greater than 3 days after discharge from the AMI hospitalization and (3) no electrocardiographic evidence of conduction disturbances or ventricular hypertrophy at the time of their final in-hospital electrocardiogram. Univariate and multivariate analyses were performed to test the association of the QRS score, and other associated risk factors, with time until coronary heart disease-related death. QRS score was found to be significantly associated with outcome (p = 0.03), as was the systolic blood pressure before infarction (p greater than 0.001). Both univariate and multivariate analysis showed that a history of systolic hypertension was the variable most strongly associated with coronary heart disease-related death. Thus, identification of AMI survivors at high risk for subsequent mortality can be improved by routine blood pressure measurement before AMI, and QRS scoring of the electrocardiogram taken at hospital discharge.