Ratio of ST-segment and myoglobin slopes to estimate myocardial salvage during thrombolytic therapy for acute myocardial infarction

A dynamic model forecasting myocardial infarct size before, during, and after reperfusion therapy: an ASSENT-2 ECG/VCG substudy

AIMS

Serial forecasts of final myocardial infarct (MI) size during fibrinolytic treatment (Rx) of ST-elevation MI would allow the identification of high-risk patients with a predicted major loss of viable myocardium, at a point when treatment may still be modified. We investigated a model for such forecasting, using time and the ECG.

METHODS AND RESULTS

We collected 234 patients with ST-elevation MI, without signs of previous MI, bundle branch block, or hypertrophy. MI size was determined by the Selvester score and was "forecasted" at: admission with patients stratified by delay time and an ECG acuteness score into three groups (EARLY, DISCORDANT, and LATE); 90 min after Rx by > or =70% ST-recovery or not and occurrence of "reperfusion peaks"; 4 h after Rx by ST re-elevations. EARLY patients had smaller final infarct sizes than LATE (9.4 vs. 20%, P=0.01). EARLY patients with > or =70% ST-recovery without a reperfusion peak had smaller infarct sizes than those with (3.1 vs. 12.5%, P=0.001). EARLY patients without ST re-elevations had smaller infarct sizes (1.5%) than those with some (9%) or many re-elevations (12%), P<0.001.

CONCLUSION

Final infarct size can be forecasted using delay time and serial ECGs. Serially updated forecasts seem especially important when both clock-time and initial ECG- signs indicate earliness.

“Mirror-lake” serial relationship of electrocardiographic and biochemical indices for the detection of reperfusion and the prediction of salvage in patients with acute myocardial infarction

BACKGROUND

Serial observations of biochemical markers in the blood and bioelectric markers on the electrocardiogram (ECG) have been used to evaluate the effectiveness of reperfusion therapy in acute myocardial infarction (AMI). This study presents a combined method for clinical use, based on the "mirror-lake" tendency of the serial changes in these markers.

METHODS

Consecutive thrombolytic-treated patients with AMI (n = 43) had ST-segment monitoring (Mortara Eli 100) and frequent serum sampling of myoglobin (MG) concentration. Their acutely predicted and finally estimated AMI sizes and myocardial salvage extents were calculated from the 12-lead standard ECG. Patients having 2 positive reperfusion indices (ST resolution at least 50%, and an increase in MG at least 2.4 fold) at 2 hours after initiation of thrombolytic therapy were considered the "complete reperfusion" group, and patients with discordant or 2 negative reperfusion indices after 2 hours of thrombolytic therapy were considered the "limited reperfusion" group.

RESULTS

Patients with complete reperfusion (n = 22) versus patients with limited reperfusion (n = 21) had +12% versus -1% myocardial salvage (P <.0001). The serial changes in the ST segment mirrored the serial changes in the MG concentration, and the rates of increase in MG correlated with the rates of resolution of the ST-segment elevation.

CONCLUSION

Myocardial salvage (measured by ECG indices) is greatest when an early increase in serum MG is "mirrored" by early resolution of ST-segment elevation.

ST segment resolution as a tool for assessing the efficacy of reperfusion therapy

Rapid, simple and inexpensive measures are needed to assess the efficacy of reperfusion therapy both in clinical practice and in clinical trials testing novel reperfusion regimens. In the last decade, several observations have led to a favorable reappraisal of the utility of ST segment monitoring as a simple means of assessing reperfusion in patients receiving fibrinolytic therapy for acute ST elevation myocardial infarction, and ST resolution is being used increasingly in clinical practice and in clinical research. This review focuses on four interrelated roles for ST segment monitoring: the assessment of epicardial reperfusion and the identification of candidates for rescue percutaneous coronary intervention; the evaluation of microvascular and tissue-level reperfusion; the determination of prognosis early after fibrinolytic therapy; and the use of ST segment resolution to compare different reperfusion regimens.

Early noninvasive detection of failed epicardial reperfusion after fibrinolytic therapy

Available noninvasive techniques for identifying patients with failed epicardial reperfusion after fibrinolytic therapy are limited by poor accuracy. It is unknown whether combining multiple noninvasive predictors would improve diagnostic accuracy and facilitate identification of candidates for rescue percutaneous coronary intervention. In the Thrombolysis In Myocardial Infarction (TIMI) 14 trial, we evaluated the ability of ST-segment resolution (n = 606), chest pain resolution (n = 859), and the ratio of 60-minute/baseline serum myoglobin (n = 308) to identify patients with angiographic evidence of failed reperfusion 90 minutes after fibrinolysis. Three criteria were prospectively defined: <50% ST resolution at 90 minutes, presence of chest pain at the time of angiography, and myoglobin ratio <4. Patients who met any individual criterion were more likely to have less than TIMI 3 flow and an occluded infarct-related artery (TIMI 0/1 flow) than those who did not meet the criterion (p <0.005 for each). When the 3 criteria were used together (n = 169), patients who satisfied 0 (n = 29), 1 (n = 68), 2 (n = 51), or 3 (n = 21) of the criteria had a 17%, 24%, 35%, and 76% probability of failing to achieve TIMI 3 flow (p <0.0001 for trend), a 0%, 6%, 18%, and 57% probability of an occluded infarct-related artery (p <0.0001 for trend), and a 0%, 1.5%, 2.0%, and 9.5% rate of 30-day mortality (p = 0.05 for trend), respectively. Use of the criteria in combination increased positive predictive values without decreasing negative predictive values. In conclusion, ST-segment resolution, chest pain resolution, and early washout of serum myoglobin can be used in combination to aid in the early noninvasive identification of candidates for rescue percutaneous coronary intervention.

Use of biochemical markers in acute coronary syndromes. IFCC Scientific Division, Committee on Standardization of Markers of Cardiac Damage. International Federation of Clinical Chemistry

This paper presents evidence and suggestions from the IFCC Committee on "Standardization of Markers of Cardiac Damage" (C-SMCD) on the use of biochemical markers for the triage diagnosis of acute coronary syndromes. There is general agreement that both 'early' and 'definitive' biochemical markers of myocardial damage are necessary and that these assays must be available with a turnaround time of 1 h or less. Currently, myoglobin is the marker that most effectively fits the role as an 'early' marker, whereas 'definitive' markers are cardiac troponins. Since the sensitivity of the initial electrocardiogram is only 50% for detecting myocardial infarction, the use of biochemical markers may significantly contribute to the early diagnosis and become relevant when the electrocardiogram is not diagnostic. In addition, new sensitive biochemical markers, particularly the cardiac troponins, are presently the best to detect the presence of minor myocardial cell damage. With regard to this, two decision limits are probably needed for the optimal use of troponins: a low abnormal value suggesting the presence of myocardial damage and a higher value suggesting the diagnosis of myocardial infarction according to traditionally used criteria. Properly designed studies should be performed to establish limits for each commercially available troponin assay. Finally, it is recognized that there is no need for the use of any biochemical marker when the clinical diagnosis is unequivocal, other than for diagnosing reinfarction, estimating the infarct size, and monitoring thrombolytic therapy.

Preservation of autonomic function following successful reperfusion with streptokinase within 12 hours of the onset of acute myocardial infarction

Successful reperfusion following thrombolysis results in increased heart rate variability in the first 24 hours after administration. Preservation of autonomic function may contribute to improved prognosis when coronary artery patency is restored with intravenous thrombolysis.