Admission prediction of expected final myocardial infarct size using weighted ST-segment, Q wave, and T wave measurements

Validation of contemporary electrocardiographic indices of area at risk and infarct size in acute ST elevation myocardial infarction (STEMI)

BACKGROUND

Electrocardiographic (ECG) methods to assess area at risk (AAR) and infarct size (IS) in patients with ST-elevation myocardial infarction (STEMI) have been previously established but not validated against contemporary benchmark Cardiac Magnetic Resonance (CMR) measures. We compared ECG-determined and CMR-determined measures for (a) AAR, (b) IS, and (c) myocardial salvage.

METHODS

Sixty patients with ECG evidence of STEMI and CMR imaging performed within 13 days were included. The ECG-determined (a) AAR scores (Aldrich and Wilkins), (b) IS (Selvester score), and (c) myocardial salvage (i.e. [AAR-IS] / AAR × 100%), were compared with CMR-determined measures.

RESULTS

Compared with CMR-determined AAR, both the Wilkins & Aldrich scores underestimated AAR, although the Wilkins (r = 0.72, p < 0.001) showed a better correlation than the Aldrich (r = 0.54, p < 0.001). Bland-Altman analysis revealed a bias of 2.6% (95% limits of agreement: 18.5%, -13.3%) for the Wilkins and 5.9% (95% limits of agreement: 25.6%, -13.8%) for the Aldrich. Estimation of IS was similar between the Selvester score and CMR, with good correlation (r = 0.77, p < 0.001) and agreement (fixed bias 0.4%, 95% limits of agreement 20.8%, -15.5%). However, ECG-determined myocardial salvage significantly underestimated CMR-determined myocardial salvage, with an inverse correlation (r = -0.33, p = 0.01).

CONCLUSIONS

The Wilkins score is superior to Aldrich score as an ECG-AAR index, Selvester score is a reasonable ECG estimate of infarct size, though ECG derived myocardial salvage does not have enough accuracy to be used in the clinical setting; it may be an inexpensive surrogate for myocardial salvage in large research studies. Further validation and prognostic studies are required.

Early Use of N-acetylcysteine With Nitrate Therapy in Patients Undergoing Primary Percutaneous Coronary Intervention for ST-Segment-Elevation Myocardial Infarction Reduces Myocardial Infarct Size (the NACIAM Trial [N-acetylcysteine in Acute Myocardial Infarction])

BACKGROUND

Contemporary ST-segment-elevation myocardial infarction management involves primary percutaneous coronary intervention, with ongoing studies focusing on infarct size reduction using ancillary therapies. N-acetylcysteine (NAC) is an antioxidant with reactive oxygen species scavenging properties that also potentiates the effects of nitroglycerin and thus represents a potentially beneficial ancillary therapy in primary percutaneous coronary intervention. The NACIAM trial (N-acetylcysteine in Acute Myocardial Infarction) examined the effects of NAC on infarct size in patients with ST-segment-elevation myocardial infarction undergoing percutaneous coronary intervention.

METHODS

This randomized, double-blind, placebo-controlled, multicenter study evaluated the effects of intravenous high-dose NAC (29 g over 2 days) with background low-dose nitroglycerin (7.2 mg over 2 days) on early cardiac magnetic resonance imaging-assessed infarct size. Secondary end points included cardiac magnetic resonance-determined myocardial salvage and creatine kinase kinetics.

RESULTS

Of 112 randomized patients with ST-segment-elevation myocardial infarction, 75 (37 in NAC group, 38 in placebo group) underwent early cardiac magnetic resonance imaging. Median duration of ischemia pretreatment was 2.4 hours. With background nitroglycerin infusion administered to all patients, those randomized to NAC exhibited an absolute 5.5% reduction in cardiac magnetic resonance-assessed infarct size relative to placebo (median, 11.0%; [interquartile range 4.1, 16.3] versus 16.5%; [interquartile range 10.7, 24.2]; P=0.02). Myocardial salvage was approximately doubled in the NAC group (60%; interquartile range, 37-79) compared with placebo (27%; interquartile range, 14-42; P<0.01) and median creatine kinase areas under the curve were 22 000 and 38 000 IU·h in the NAC and placebo groups, respectively (P=0.08).

CONCLUSIONS

High-dose intravenous NAC administered with low-dose intravenous nitroglycerin is associated with reduced infarct size in patients with ST-segment-elevation myocardial infarction undergoing percutaneous coronary intervention. A larger study is required to assess the impact of this therapy on clinical cardiac outcomes.

CLINICAL TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry. URL: http://www.anzctr.org.au/. Unique identifier: 12610000280000.

Usefulness of quantitative baseline ST-segment elevation for predicting outcomes after primary coronary angioplasty or fibrinolysis (results from the DANAMI-2 trial)

The DANAMI-2 trial showed a 40% decrease in the composite end point with primary coronary angioplasty versus fibrinolysis. This result was primarily driven by a decrease in reinfarction, with no significant difference in mortality or stroke rates. The objective of this study was to determine the prognostic value of the sum ST-segment elevation (SigmaST) on baseline electrocardiography in patients who were randomized to receive primary coronary angioplasty versus fibrinolysis. In the DANAMI-2, 1,450 patients had baseline ST-segment deviation measurements and were assigned to quartiles according to SigmaST: 0 to 6.5, 7.0 to 9.5, 10.0 to 14.5, and 15.0 to 70.5 mm. The composite and component end-point rates at 30 days were determined for each quartile and chi-square for trend statistic was used to compare end-point rates across quartiles of SigmaST. The composite end point occurred more often with increasing SigmaST (p = 0.05). With regard to component end points, only mortality increased significantly with SigmaST (p = 0.03), whereas reinfarction and stroke rates did not. By multivariate analysis, only SigmaST and age were independent predictors of mortality. The relative benefit of primary coronary angioplasty was similar for all SigmaST quartiles. In conclusion, the magnitude of SigmaST correlates with increased mortality at 30 days, thus driving the composite end point rate. Regardless of SigmaST, patients had a lower composite end-point rate with primary coronary angioplasty than with fibrinolysis.

“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.

Clinical and angiographic characteristics of patients with combined anterior and inferior ST-segment elevation on the initial electrocardiogram during acute myocardial infarction

OBJECTIVE

We evaluated the significance of combined anterior and inferior ST-segment elevation on the initial electrocardiogram (EKG) in patients with acute myocardial infarction (AMI) and correlated it with AMI size and left ventricular (LV) function.

METHODS

We analyzed admission EKGs of 2996 patients with AMI from the GUSTO-I angiographic substudy and the GUSTO-IIb angioplasty substudy who underwent immediate angiography. In all, we identified 1046 patients with anterior ST elevation (ST-segment elevation in > or =2 of leads V1-V4) and divided them into 3 groups: Group 1, anterior + inferior ST elevation (ST elevation in > or =2 of leads II, III, aVF, n =179); Group 2, anterior ST elevation only (<2 of leads II, III, aVF with ST elevation or depression, n = 447); Group 3, anterior ST elevation + superior ST elevation (ST depression in > or =2 of leads II, III, aVF, n = 420).

RESULTS

Cardiac risk factors, prior AMI, prior percutaneous transluminal coronary angioplasty or coronary artery bypass graft, Killip class, and thrombolytic therapy assignment did not differ among the 3 groups. Group 1 patients had greater number of leads with ST elevation compared to Groups 2 and 3 (ST elevation in > or =6 leads 83% vs 22% vs 49%, P =.001). Despite greater ST-segment elevation, Group 1 patients had a lower peak CK level (median baseline peak CK 1370 vs 1670 vs 2381 IU, P =.0001) and less LV dysfunction (median ejection fraction 0.53 vs 0.49 vs 0.45, P =.0001; median number of abnormal chords 21 vs 32 vs 40, P =.0001). Angiographically, Group 1 had 2 distinct subsets of patients with either right coronary artery (RCA) (59%) or left anterior descending coronary artery (LAD) (36%) occlusion. In contrast, the infarct-related artery (IRA) was almost entirely the LAD in Groups 2 and 3 (97%). Further, the site of IRA occlusion in Group 1 was mostly proximal RCA (67%) in the RCA subgroup and mid or distal LAD (70%) in the LAD subgroup. ST-segment elevation in lead V1 > or = V3 and absence of progression of ST elevation from lead V1 to V3 on the EKG differentiated IRA-RCA from IRA-LAD in patients with combined anterior and inferior ST elevation.

CONCLUSIONS

The AMI size and LV dysfunction in patients with anterior ST elevation is directly related to the direction of ST segment deviation in the leads II, III, aVF; least with inferior ST elevation, intermediate with no ST deviation, and maximal with superior ST elevation (inferior ST depression). Despite greater ST-segment elevation, patients with combined anterior and inferior ST elevation have limited AMI size and preserved LV function. Angiographically, they comprise 2 distinct subsets with either proximal RCA or mid to distal LAD occlusion. A predominant right ventricular and limited inferior LV AMI from a proximal RCA occlusion, or a smaller anterior AMI from a more distal occlusion of LAD may explain their limited AMI size despite greater ST elevation.