Sensitivity For Diagnosis Of Acute Myocardial Infarction Research Articles

IMPROVING THE DIAGNOSIS OF ACUTE MYOCARDIAL INFARCTION BY DERIVING EPICARDIAL POTENTIALS FROM THE BODY SURFACE POTENTIAL MAP USING INVERSE ELECTROCARDIOGRAPHY AND AN INDIVIDUALIZED TORSO MODEL

Epicardial potentials (EP) derived from the body surface potential map (BSPM) improve acute myocardial infarction (AMI) diagnosis. In this study, we compared EP derived from the 80-lead BSPM using a standard thoracic volume conductor model (TVCM) with those derived using a patient-specific torso model (PSTM) based on body mass index (BMI). Patients presenting to ED between August 2009 and August 2011 with acute ischaemic-type chest pain at rest were enrolled. At first medical contact, 12-lead ECG and BSPM were recorded. BMI for each patient was calculated. Cardiac troponin-T (cTnT) was sampled 12h after symptom onset. Patients were excluded from analysis if they had any electrocardiographic confounders to interpretation of the ST-segment. A cardiologist assessed the 12-lead ECG for STEMI by Minnesota criteria and BSPM. BSPM ST-elevation (STE) was ≥0.2mV in anterior, ≥0.1mV in lateral, inferior, RV or high right anterior and ≥0.05mV in posterior territories. To derive EP, the BSPM data were interpolated to yield values at 352-nodes of a Dalhousie torso. Using an inverse solution based on the boundary element method, EP at 98 cardiac nodes positioned within a standard TVCM were derived. The TVCM was then scaled to produce a PSTM, using a model developed from CT in 48 patients of varying BMI, and EP re-calculated. EP ≥0.3mV defined STE. A cardiologist blinded to both the 12-lead ECG and BSPM interpreted the EP map. AMI was defined as cTnT ≥0.1µg/L. Enrolled were 400 patients (age 62 ± 13 yrs; 57% male): 80 patients had exclusion criteria. Of the remaining 320 patients, BMI was 27.8 ± 5.6kg m-2. Of these, 180 (56%) had AMI. Overall, 132 had Minnesota STEMI on ECG (sensitivity 65%, sensitivity 89%) and 160 had BSPM STE (sensitivity 81%, specificity 90%). EP STE occurred in 165 patients using TVCM (sensitivity 88%, specificity 95%, p<0.001) and in 206 patients using PSTM (sensitivity 98%, specificity 79%, p<0.001). Of those with EP <0.3mV using TVCM and AMI (n=22), all had EP ≥0.3mV when an individualised PSTM was used. Among patients presenting with ischaemic-type chest pain at rest, EP derived from BSPM using a novel PSTM significantly improves sensitivity for AMI diagnosis.

Role of cardiac troponin in the diagnosis of acute myocardial infarction in comatose patients resuscitated from out-of-hospital cardiac arrest

Troponin is a major diagnostic criterion of acute myocardial infarction (AMI) but in out-of-hospital cardiac arrest (OHCA) patients, its diagnostic value may be altered by cardiopulmonary resuscitation. Single-centre study assessing the diagnostic characteristics of troponin for AMI diagnosis in consecutive patients resuscitated from OHCA between 2002 and 2008 with coronary angiogram (CA) performed on admission. Patients with obvious non-cardiac cause of OHCA, unsustained or absent return of spontaneous circulation were excluded. AMI was defined on CA by the presence of acute occlusion or critical stenosis with intracoronary fresh thrombus easily crossed by an angioplasty wire. Troponin concentration was recorded once on admission and once 6-12h after the OHCA. A total of 163 patients aged 56 (median) years (interquartile range (IQR) 48-65) was included, all comatose. Most prevalent initial OHCA rhythms were ventricular fibrillation (49%) and asystole (41%). AMI was diagnosed on coronary angiogram in 37% of the patients. Median troponin concentration on admission was 1.7 (0.3-10)ngml(-1) and sensitivity for AMI diagnosis was 72% and specificity 75% for a 2.5ngml(-1) cut-off. A combined criterion comprising ST elevation and troponin >2.5ngml(-1) had a sensitivity of 93% and specificity of 64%. Six to twelve hours after the OHCA, median troponin concentration was 7.6ngml(-1) (1.4-47.5), sensitivity was 84% and specificity 84% for a 14.5ngml(-1) cut-off. Troponin I has a good diagnostic value for AMI diagnosis in OHCA patients. In combination with ST elevation, troponin I on admission achieves a very high sensitivity.

Body Surface Mapping

Recent advances in biomarkers have improved the evaluation of patients with acute chest pain, but current critical care pathways may still lead to important delays in early diagnosis and, hence, treatment of acute myocardial infarction (AMI). Electrocardiographic changes may occur within seconds of an ischemic insult, but the conventional 12-lead electrocardiogram (ECG) typically has only 50% to 60% sensitivity for diagnosis of AMI. Recording of multiple ECGs over a larger thoracic surface area, including the right ventricular, high left lateral, and posterior regions, by body surface mapping (BSM) has been made feasible in the setting of acute coronary syndromes by novel developments in electrode technology and simultaneous multichannel ECG data acquisition. Clinical studies of an Food and Drug Adminstration-approved BSM system (PRIME-ECG) have demonstrated improved early diagnosis of AMI in patients without 12-lead ST elevation and improved detection of right ventricular or posterior involvement in ST elevation MI. The improved diagnostic sensitivity compared with the conventional 12-lead ECG coupled with the potential reduction of delay to diagnosis compared with biomarkers suggest that BSM may have an important role as part of a chest pain critical care pathway for evaluation of patients with ischemic type chest pain.

Accuracy of 22-lead ECG analysis for diagnosis of acute myocardial infarction and coronary artery disease in the emergency department: A comparison with 12-lead ECG

To compare a new 22-lead ECG with the 12-lead ECG for diagnosis of acute myocardial infarction (AMI). Prospective study of all consenting patients presenting to the emergency department with chest pain. Urban hospital ED. 163 patients admitted with a cardiac-related diagnosis and complete data sets of 22- and 12-lead ECG results and creatine kinase-MB analysis. Patient care and existing protocols were unaltered, with the exception of including the new 22-lead ECG. Forty-one of 163 patients had an AMI as defined by creatine kinase-MB analysis. The 22-lead ECG provided a statistically significant improvement in sensitivity (83%) for AMI diagnosis over the 12-lead ECG (51%) with specificities of 76% and 99%, respectively. When combined with clinical judgment, the 22-lead ECG could provide a 97.6% sensitivity for AMI diagnosis while reducing unnecessary admissions for "rule-out MI" by 69%.