New body surface isopotential map evaluation method to detect minor potential losses in non-Q-wave myocardial infarction.

BACKGROUND: Potential losses caused by stable non-Q-wave myocardial infarction (MI) are too small to diagnose with the use of standard ECG. The aim of the present study was to obtain accurate diagnostic criteria for this prognostically important disease with the help of body surface mapping. METHODS AND RESULTS: Body surface potentials were recorded with the use of 63 unipolar leads in 45 patients with a non-Q-wave MI (41 to 75 years old); 24 healthy adults, 42 patients with unstable angina, and 70 patients with Q-wave MI served as reference groups. Qualitative pathological features of the isopotential maps, such as onset time and site and magnitude of the first right-anterior/anterior minimum, as well as pathological negativities at that time, were defined in non-Q-wave MI cases. These features, which account for the activation sequence and the body surface projections of specific cardiac regions (Selvester classification), showed a 91% sensitivity and an 88% specificity for the detection of non-Q-wave MI. In comparison, the different departure maps (first third QRS, QRS, and QRST isoarea) resulted in less favorable specificities (50% to 58%). Concordance between the isopotential maps and the acute-phase ECG (90%), hypokinesis (64%), fixed perfusion defects (59%), and significant stenosis of the infarct-related coronary artery (87%) supported the concept that these isopotential map changes correspond to the supposed sites of MI. There were pathological features in 69% of patients with unstable angina, with similar concordances as in non-Q-wave MI. CONCLUSIONS: Isopotential maps revealed characteristic features that were suitable for the detection and localization of non-Q-wave MI in the clinical setting of unstable coronary artery disease.

Continuous ST-segment monitoring during coronary angioplasty using orthogonal ECG leads.

In order to characterize ST-segment shifts during transient coronary artery occlusion, 24 patients with single-vessel disease were continuously monitored during percutaneous transluminal coronary angioplasty by use of a computerized orthogonal lead system. Changes of ST-segment (J + 60 ms) in leads X, Y, and Z and of the ST vector magnitude were analyzed by using 20 microV as a threshold for significant ST-segment shift. The sensitivity and magnitude of this shift were compared among the left anterior descending, right coronary, and circumflex artery groups (11, 8, and 5 patients, respectively) during balloon inflation. Significant ST-segment shifts were seen in 22 patients (92%) in ST-VM, Y, and Z leads and all patients in lead X (100%). There was no significant difference in sensitivity of either the ST vector magnitude or the most sensitive lead for occlusion detection among the three groups. There was a significantly greater magnitude of ST shift during left anterior descending artery occlusion than during right coronary artery and circumflex artery occlusions in ST-VM. Analysis of the direction of ST shifts in the X, Y, and Z leads showed a characteristic pattern, which could distinguish among the three coronary groups in 21 patients (88%). The presence of collaterals was significantly associated with ST-segment depression in leads oriented toward ischemia (3 of 6 patients) as compared with ST-segment elevation in the absence of collaterals (all of 15 patients), P > .01. It is concluded that ST-segment shift in the orthogonal leads is a reliable marker for myocardial ischemia. It is equally sensitive to occlusion of each of the three major coronary arteries and can thus identify the occluded coronary. An ST-segment depression instead of an elevation was related to the presence of collaterals, which may reflect a lesser degree of ischemia.

Influence of race, sex, and age on management of unstable angina and non-Q-wave myocardial infarction: The TIMI III registry.

OBJECTIVE: To investigate the natural history and response to treatment of patients with unstable angina or non-Q-wave myocardial infarction (MI). DESIGN: Inception cohort. SETTING: Patients in general community, primary care, or referral hospitals. PATIENTS: All patients with an episode of unstable exertional chest pain or chest pain at rest presumed to be ischemic in origin lasting 5 minutes or more but without persisting ST-segment elevation greater than 30 minutes or the development of Q-waves were identified and enumerated in 18 participating hospitals. A subset of enumerated patients was selected to be followed prospectively using specific sampling strategies that would provide adequate numbers of black, women, and elderly (aged > or = 75 years) patients for comparison with their respective counterparts. MAIN OUTCOME MEASURES: The primary analysis compared the incidence of death or MI at 42 days after entry into the prospective study according to race, sex, and age. Other outcomes considered were recurrent ischemia and the combined outcomes of death, MI, or recurrent ischemia by 42 days after entry. RESULTS: A total of 8676 admissions with unstable angina or non-Q-wave MI were enumerated and, of these, 3318 patients were selected for the prospective study. The direct adjusted mean age of 3318 patients was 63.8 years. There were 943 blacks and 2375 nonblacks. Compared with nonblacks, blacks were less likely to be treated with intensive anti-ischemic therapy for their qualifying anginal episode and less likely to undergo invasive procedures (risk ratio [RR], 0.65%; 95% confidence interval [CI], 0.58 to 0.72; P<.001). However, of those who underwent angiography (45% of blacks and 61% of nonblacks), blacks had less extensive and severe coronary stenoses than nonblacks. The incidence of death and MI was similar for blacks and nonblacks, but blacks had a lower incidence of recurrent ischemia. There were 1678 men and 1640 women. Women were less likely than men to receive intensive anti-ischemic therapy and less likely to undergo coronary angiography (RR, 0.71; 95% CI, 0.65 to 0.78; P<.001). Women had less severe and extensive coronary disease and were less likely to undergo revascularization, yet had a similar risk of experiencing an adverse cardiac event by 6 weeks. There were 2490 patients aged 75 years or less and 828 patients aged more than 75 years. Elderly patients received less aggressive anti-ischemic therapy and were less likely to undergo coronary angiography than their younger counterparts. Elderly patients had more severe and extensive coronary disease but fewer revascularization procedures than younger patients and experienced a much higher incidence of adverse cardiac events both in hospital and by 6 weeks. CONCLUSIONS: Among patients presenting with acute ischemic chest pain without persistent ST-segment elevation, blacks appeared to have less severe coronary disease, received revascularization less frequently, and had less recurrent ischemia compared with nonblacks. Women were also found to have less severe coronary disease and were treated less intensely than men, but experienced similar outcomes. Elderly patients had more severe coronary disease than younger patients on coronary angiography, but were more likely to be treated medically, and they experienced far more adverse outcomes. These data suggest that more aggressive strategies should be directed to those patients with the greatest likelihood of adverse outcomes.

Continuous ST segment recording during thrombolysis in acute myocardial infarction: a report on orthogonal ECG monitoring.

BACKGROUND: A noninvasive, real time method is needed to identify failures of thrombolysis and evaluate new treatments in acute myocardial infarction (MI). OBJECTIVE: To study XYZ monitored ST segment evolution during thrombolysis in acute MI and to examine the correlation of ST parameters to outcome. DESIGN: Thirty-five patients receiving tissue plasminogen activator (tPA) (n = 18) or streptokinase (SK) (n = 17) for acute MI were monitored by vector-cardiography during the first 12 h of thrombolytic therapy. Computer constructed ST vector magnitude (ST-VM) trends were analyzed for 0.5 or greater decline from the initial ST amplitude (IA) lasting for 10 mins or longer (ST response) and for ST re-elevation 0.75 IA or more following ST decline. The degree of ST response, time from treatment onset and ST-VM re-elevation were correlated to peak creatine phosphokinase (CPK), left ventricular ejection fraction (EF) and final ST-VM. RESULTS: The presence of an ST response correlated with a lower peak CPK (2691 +/- 1625 versus 4057 +/- 1622 U/L, P = 0.043) and tended to higher EF (0.48 +/- 0.11 versus 0.36 +/- 0.09, P = 0.057). The ST responder group had fewer patients with ST re-elevation than the group of nonresponders (13 of 30 versus five of five patients, P = 0.041). Moreover, ST response before 120 mins was associated with lower peak CPK (2089 +/- 1299 versus 3367 +/- 177 U/L, P = 0.02) and better EF (0.54 +/- 0.06 versus 0.41 +/- 0.12, P = 0.02) compared with later or no ST response. The degree of ST response correlated significantly with a lower ST-VM during the last hour (r = -0.744, P = 0.001). ST trends showed no significant differences between treatment groups (tPA versus SK). The tPA group, however, tended to an overall earlier ST response (117 +/- 75 versus 163 +/- 64 mins, P = 0.13). CONCLUSIONS: Early ST-VM trends are closely associated with electrocardiographic and clinical outcome and may provide a basis for clinical management, therapeutic comparisons and better insight into thrombolysis in MI.

Predictors of non-Q-wave acute myocardial infarction in patients with acute ischemic syndromes: an analysis from the Thrombolysis in Myocardial Ischemia (TIMI) III trials.

Among patients with acute ischemic syndromes, patients with non-Q-wave acute myocardial infarction (AMI) are known to be at higher risk for death, reinfarction, and other morbidity than those with unstable angina. The aim of this study was to develop a clinically useful prediction rule to assist in distinguishing, at the time of presentation, patients with non-Q-wave AMI from those with unstable angina. The TIMI IIIB trial enrolled 1,473 patients presenting with ischemic pain at rest within 24 hours who had either electrocardiographic changes or documented coronary artery disease. Non-Q-wave AMI on presentation was documented by elevation of creatine kinase-MB in 33% of patients. Fifty clinical and electrocardiographic variables were compared between the patients with non-Q-wave AMI and unstable angina. After performing logistic regression, 4 baseline characteristics independently predicted non-Q-wave myocardial AMI: the absence of prior coronary angioplasty (odds ratio [OR] = 3.3, p < 0.001), duration of pain > or = 60 minutes (OR = 2.9, p < 0.001), ST-segment deviation on the qualifying electrocardiogram (OR = 2.0, p < 0.001), and recent-onset angina (OR = 1.7, p = 0.002). Using these 4 characteristics, a prediction rule for non-Q-wave AMI was developed. For the entire cohort of patients in TIMI III, the percentages of patients with non-Q-wave AMI when 0, 1, 2, 3, and 4 risk factors were present were 7.0%, 19.6%, 24.4%, 49.9%, and 70.6%, respectively (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)