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Biomedical subjects

J E Madias

Publications and source records attributed to J E Madias.

At least 19 recordsLinked to original sources
PubMed1997

The role of "ischemic ST-segment counterpoise" in rendering the response of exercise electrocardiogram falsely negative.

Exercise electrocardiogram (ECG) has a high rate of false negative results in comparison with simultaneously performed thallium-201 perfusion scintigraphy, particularly in patients with single-vessel coronary artery disease, low exercise workload, inadequate heart rate rise, and resting ECG abnormalities. We present the case of a patient in whom thallium-201 SPECT scintigram revealed equally extensive and severe myocardial ischemia in two myocardial planes opposite each other. The accompanying exercise ECG did not disclose ischemic changes despite the adequacy of heart rate rise in this patient with severe right and left anterior descending coronary artery disease. We propose, as an explanation for this phenomenon, that in this patient the ischemic ST-segment vectors of equal magnitude and direction but of opposite sense, generated during stress, cancelled each other ("ischemic ST-segment counterpoise"), thus rendering the exercise ECG normal.

Coronary Disease↗
PubMed1997

Transient disappearance of Q waves of previous myocardial infarction due to exercise-induced ischemia of the contralateral noninfarcted myocardium.

The electrocardiogram (ECG) of a 40-year-old woman with an old inferolateral myocardial infarction revealed, in the course of an exercise treadmill/thallium test, gradual disappearance of infarctional Q waves, which reappeared gradually during recovery from exercise. The patient had evidence of exercise-induced myocardial ischemia both by the ECG and by thallium-201 perfusion scintigraphy involving several myocardial regions. The temporal association of transient disappearance of Q waves with the occurrence of reversible ischemia suggested that the latter was instrumental in producing this phenomenon, through a transient failure of the ischemic anterior wall to shift the initial depolarization forces away from the infarcted inferolateral territory. Further evidence for this concept was provided by the case of another patient, a 49-year-old man who also had an old inferolateral myocardial infarction and whose ECG in the course of an exercise treadmill/thallium test did not reveal any changes in the infarctional Q waves. In this patient, thallium images showed mild, reversible inferolateral myocardial ischemia but a well perfused anterior wall, which provided for early depolarization forces (thus Q waves) directed opposite to the region of infarcted myocardium.

Adult↗
PubMed1997

Standard 12-lead ECG versus special chest leads in the diagnosis of right ventricular myocardial infarction.

The case of a 60-year-old woman with an acute inferior transmural myocardial infarction associated with a right ventricular myocardial infarction provided an opportunity to compare the performance of the 12-lead electrocardiogram (ECG) and the right chest leads in the diagnosis of infarction of the right ventricle. While the right chest leads revealed unequivocal evidence of ischemic injury emanating from the right ventricle, the standard leads II and III showed changes compatible with inferior myocardial infarction; familiarity with vectorial interpretive concepts of ST segment deviations could provide a hint of an associated right ventricular involvement. This report is presented at a time of renewed controversy regarding the necessity of special ECG leads in the diagnosis of acute right ventricular infarction in the routine emergency department environment.

Electrocardiography↗
PubMed1996

Atrial fibrillation in acute myocardial infarction: a prospective study based on data from a consecutive series of patients admitted to the coronary care unit.

Atrial fibrillation (AF) is a common and much-studied arrhythmia in patients with acute myocardial infarction (MI). However, documentation of its occurrence in temporal association with MI has been often neglected in the literature; also, its frequent occurrence with mere advanced age, or in the setting of various cardiac conditions or complications, has prevented the definition of an exact role for AF as a marker or determinant of outcome in patients with MI. The purpose of this study was to evaluate prospectively the frequency of AF (present or occurring subsequently) in a consecutive series of patients with MI admitted to the Coronary Care Unit, and to explore for variables associated with this arrhythmia; the role of AF in determining major clinical outcomes of the patients was also examined. A large data base of baseline, clinical, laboratory, and patient outcome variables was generated and continuously updated to examine correlates of AF and its possible role in determining prognosis. AF was found in 72 of 517 patients, of whom 58 experienced this arrhythmia anew. Univariate analyses detected a positive association of AF with age, pulmonary congestion, left ventricular hypertrophy, high admission Killip class, and a large array of complications including in-hospital mortality. Multivariate analyses showed, however, that AF correlated weakly with age and strongly with left ventricular hypertrophy and occurrence of ventricular tachycardia, but that it was not a determinant of ventricular fibrillation or in-hospital mortality.

Age Factors↗
PubMed1996

Correlative studies of heart rate and heart rate variability indices from five consecutive ambulatory electrocardiogram recordings in patients with coronary artery disease.

BACKGROUND: Reproducibility of heart rate (HR) and heart rate variability (HRV) indices from ambulatory electrocardiograms (AECGs) is a prerequisite for their use as predictors or monitors of disease progression, or response to therapeutic interventions. HYPOTHESIS: This study sought to determine the stability over time of HR and HRV indices in patients with coronary artery disease. METHODS: Five AECGs, recorded at 1-week intervals in 21 clinically stable patients, were used to calculate minimum, average, and maximum HR, and three commonly used HRV indices in data samples of 15, 30, 60, 120, daytime and nighttime intervals (complete data were available on 17 patients). RESULTS: All parameters studied were stable over time (p = NS). Diurnal variation was found only for the average and maximum HR, with values being higher for daytime than for nighttime. Intercorrelations of the HR and HRV indices were poor and varied among the five AECGs, suggesting that these parameters reflect different aspects of HRV. The HR and HRV variables calculated from short-time intervals correlated poorly with the corresponding information from 24-h recordings, and such relationships varied among the five AECGs. CONCLUSIONS: Thus, HR and HRV indices from five consecutive AECGs recorded at 1-week intervals are reproducible. The poor intercorrelations between pairs of the studied indices suggest that none of these parameters can be used as surrogate of the others. Finally, the poor performance of HR and HRV indices, deriving from short-time intervals, indicate that they cannot be employed in lieu of parameters calculated from 24-h AECGs.

Aged↗
PubMed1996

The paradox of negative exercise stress ECG/positive thallium scintigram. Ischemic ST-segment counterpoise as the underlying mechanism.

A 62-year-old woman with exertional angina underwent an exercise thallium-201 stress test. She exercised for 4 minutes on the treadmill using a modified Bruce protocol, reaching 94% of her predicted maximal heart rate, and stopped because of chest pain and fatigue. No ST-segment depression was detected at peak exercise or in the recovery period. In contrast, the thallium-201 myocardial single-photon emission computed tomography images in the short-axis, vertical long-axis, and horizontal long-axis views revealed severe myocardial ischemia involving the anterior, septal, posteroinferior, and posterolateral planes of the heart. Coronary arteriography showed severe stenosis of the left anterior descending and right coronary arteries. The information from the exercise electrocardiogram (ECG), thallium-201 myocardial scintigraphy, and a coronary angiogram suggested that the false negative ECG response was due to ischemic ST-segment counterpoise (i.e., cancellation of ischemic ST-segment vectors, generated by equally extensive and severe ischemia involving myocardial planes opposite each other.

Electrocardiography↗
PubMed1995

Correlates and in-hospital outcome of painless presentation of acute myocardial infarction: a prospective study of a consecutive series of patients admitted to the coronary care unit.

BACKGROUND: The past literature has long ago identified painless myocardial infarction as a clinical entity; however, the term has been applied, often loosely, to denote diagnosis of infarction made at autopsy, or during routine electrocardiography, or at presentation with atypical symptoms. Many of the old studies were retrospective or included patients who could not contribute a reliable history. METHODS: Systematic interviews of 517 consecutive patients with an acute myocardial infarction admitted to the Coronary Care Unit were carried out; a large array of data was collected prospectively while the patients were taken care of in the hospital. RESULTS: A reliable history of symptoms at the inception of the clinical episode could be provided by 501 patients; 40 patients (8.0%) presented with painless (not silent) infarction, while the remaining 461 had pain. Multivariate analysis revealed that painless presentation of myocardial infarction correlated positively with age (OR 1.05, CI 1.02-1.08) and admission Killip class (OR 2.58, CI 2.16-2.97), and negatively with history of prior angina (OR 0.16, CI 0.15-064); also it was not a predictor of increased rate of mortality or life-threatening arrhythmias. CONCLUSIONS: Presentation with painless myocardial infarction occurs in older patients with increased degrees of pulmonary congestion on admission, and less frequent rate of prior angina than the ones encountered in patients with pain; however such presentation is not an independent predictor of worse than expected in-hospital outcome.

Aged↗
PubMed1993

The "giant R waves" ECG pattern of hyperacute phase of myocardial infarction. A case report.

The author describes a rarely appreciated electrocardiographic (ECG) pattern of the hyperacute phase of myocardial infarction, characterized by the transient development of very tall R waves merging with maximally elevated ST-segments, and the reduction of the depth, or complete disappearance of S waves. Similar ECG findings are frequently recorded in epicardial and precordial tracings in the animal laboratory, immediately following experimental occlusion of a coronary artery. In patients with acute myocardial infarction, the "giant R waves" ECG pattern is seen very early in the clinical course. Often the ECG appearances described above are missed either because patients suffering a myocardial infarction do not present to the hospital shortly after the inception of symptoms, or are attributed to conduction abnormalities of the classic variety or to ventricular tachycardia. The incidence of the giant R waves ECG pattern in the setting of clinical acute myocardial infarction is not known. Also its pathophysiologic, clinical, and prognostic correlates remain to be defined by appropriately designed research protocols.

Aged↗
PubMed1991

The S wave in acute anterior Q-wave myocardial infarction: a study with serial multilead precordial maps and standard ECGs.

To investigate the relationship of S waves with R waves and/or Q waves in the ECGs of patients with acute myocardial infarction, 20 patients with anterior Q-wave infarcts had serial 49-lead precordial maps and simultaneously recorded standard ECGs on admission and at 13 predetermined time intervals, extending to their discharge from the hospital. The sums of S waves (sigma S) from ECG leads of both precordial maps and standard ECGs showing ST-segment elevation on admission were correlated with the corresponding sums of R waves (sigma R) and/or Q waves (sigma Q). Correlation of sigma S by the precordial maps and the sigma S by the standard ECG was good (r = 0.88). However, correlation of sigma S with sigma R and sigma Q by both the precordial maps and standard ECG were poor (r values ranged between -0.02 and -0.32). Fair correlations were found between sigma S + sigma Q and the corresponding sigma R by both ECG systems (r = 0.36, precordial map and r = 0.40, standard ECG). The present study demonstrates (1) that precordial (consequently partial) ECG mapping systems have no advantage over standard precordial ECG, and (2) that quantitative data from S waves correlate weakly with similar information from corresponding R waves or Q waves, but fairly with the latter two combined, as recorded by the two ECG systems employed.

Data Collection↗