Exclusion Of Myocardial Infarction Research Articles

A rapid protocol to identify and exclude acute myocardial infarction: Continuous 12-lead ECG monitoring with 2-hour delta CK-MB

A prospective observational study was performed in 706 chest pain patients who underwent our chest pain evaluation protocol which consists of continuous 12-lead ST-segment monitoring with automated serial ECG (SECG) and a 2-hour delta (Δ) CK-MB level determination before ED physician making final disposition decision to determine the incremental value of our 2-hour protocol for identifying myocardial infarction (MI) as compared with the initial ECG in combination with a baseline CK-MB. The initial ECG was obtained on presentation and considered positive if it revealed injury or ischemia. SECGs were obtained at least every 10 minutes and considered positive if it revealed new injury or ischemia. The baseline CK-MB value was considered positive if it was ≥12 ng/mL and index ≥4%. ΔCK-MB was defined as a difference between the 2 hour and baseline CK-MB and was considered positive if the value was ≥+1.5 ng/mL. MI was defined as acute myocardial infarction (AMI) or recent AMI (ie, AMI patients presenting on falling curve of CK-MB). The incremental value of the 2 hour protocol (ie, SECG in conjunction with ΔCK-MB) was more sensitive for identification of MI than the baseline protocol (ie, initial ECG in conjunction with the baseline CK-MB) (94.0% versus 55.4%; P < .0001) and reliably both identified (+LR = 14.6) and excluded MI (−LR = 0.06). SECG monitoring in conjunction with the 2 hour ΔCK-MB allows for early identification and exclusion of MI, and can assist the ED physician in making appropriate treatment and disposition decisions. (Am J Emerg Med 2000;18:698-702.

Diagnosis of acute myocardial infarction from sequential enzyme measurements obtained within 12 hours of admission to hospital.

A prospective study was made of sequential changes in serum creatine kinase (CK) and CK-MB isoenzyme activity within the 12 hours following admission to the coronary care unit on 65 patients with recent chest pain. CK determinations were performed in the laboratory or in the coronary care unit using a dry reagent strip analyser. Slope values for log CK/hour and log CK-MB/hour were calculated, used to confirm or exclude the diagnosis of myocardial infarction, and compared with diagnosis by conventional means. Compared with retrospective diagnosis using all available information, the CK slope had a sensitivity of 100% and a specificity of 94%. This compared with a sensitivity of 94% and specificity of 90% for diagnosis using upper reference limits alone. Determination of CK slope permits very rapid and accurate biochemical confirmation or exclusion of myocardial infarction and the possibility of performing the measurements on the coronary care unit. It additionally offers the prospect of major cost savings resulting from early discharge or transfer from the coronary care unit.

Perioperative mortality rate in patients with unstable angina selected by exclusion of myocardial infarction

Coronary bypass surgery may be associated with an increased perioperative mortality rate in patients with unstable compared to stable angina. The mortality rate is excessively high when surgery is performed during evolving myocardial infarction. Elevated plasma MB CPK isoenzyme activity is a remarkably sensitive and specific marker of myocardial damage. Accordingly, we studied 111 patients with unstable angina to determine whether exclusion of patients with initially elevated MB CPK improves the perioperative mortality rate. Plasma MB CPK activity was assayed prior to catheterization and every 2 hours therafter. Of the 111 patients, 16, with initially elevated MB CPK activity, were excluded and managed medically. Catheterization was performed in 59 patients, and severe vessel obstruction was documented in 55. Coronary bypass surgery performed in 47 patients was associated with a mortality rate of 4 per cent. Thus, after exclusion of patients with evolving infarction by MB CPK isoenzyme analysis, catheterization and coronary bypass surgery in patients with unstable angina resulted in a mortality rate comparable to that in patients with stable angina.

QRS-T Patterns in Multiple Precordial Leads that May Be Mistaken for Myocardial Infarction

The electrocardiograms of patients with pathologic evidence of right ventricular hypertrophy and/or dilatation and exclusion of myocardial infarction are presented to bring out certain features likely to be mistaken for myocardial infarction: (1) abnormal qR or QS patterns or cove plane inversion of the T waves in leads from the right precordium; (2) reduction in the amplitude of the initial R wave or replacement by a QS deflection and/or change from an upright to an inverted T wave as the electrode is moved from the V 1 position to the transitional zone; (3) abnormal qrS deflections in leads from the left axilla.