PubMed Health⌕ Search

Biomedical subjects

E M Dwyer

Publications and source records attributed to E M Dwyer.

At least 19 recordsLinked to original sources
PubMed2003

Immediate exercise hyperemia in humans is contraction intensity dependent: evidence for rapid vasodilation.

We tested the hypothesis that rapid vasodilation proportional to contraction intensity contributes to the immediate (first cardiac cycle after initial contraction) exercise hyperemia. Ten healthy subjects performed single 1-s isometric forearm contractions at 5, 10, 15, 20, 30, 50, and 70% maximal voluntary contraction intensity (MVC) in arm above heart (AH) and below heart (BH) positions. Forearm blood flow (FBF; brachial artery mean blood velocity, Doppler ultrasound), mean arterial pressure (arterial tonometry), and heart rate (electrocardiogram) were measured beat by beat. Venous emptying (measured with a forearm strain gauge) was already maximized at 5% MVC, indicating that increases in contraction intensity did not further empty the forearm veins. Immediate increases in FBF were linearly proportional to contraction intensity from 5 to 70% MVC in AH (slope = 4.4 +/- 0.5%DeltaFBF/%MVC). In BH, the immediate increase in FBF demonstrated a curvilinear relationship with increasing contraction intensity and was greater than AH at 15, 20, 30, and 50% MVC (P < 0.05). Peak changes in FBF were greater in BH vs. AH from 10 to 50% MVC, even when venous refilling was complete (P < 0.05). These data support the existence of a rapid-acting vasodilatory mechanism(s) at the onset of human forearm exercise.

Adult↗
PubMed2000

Role of hypertension, diabetes, obesity, and race in the development of symptomatic myocardial dysfunction in a predominantly minority population with normal coronary arteries.

BACKGROUND: Hypertension, diabetes, and obesity have been reported as risk factors for both vascular and myocardial disease. Myocardial disease may be manifest as systolic or diastolic dysfunction. The development of coronary artery disease frequently obscures or confounds the myocardial disease. Our purpose was to study the effect of these risk factors and race on the frequency and severity of myocardial disease in the absence of coronary artery disease. METHODS AND RESULTS: We studied patients referred to the cardiac catheterization laboratory. We selected 233 patients with normal coronary arteries and excluded patients with other structural cardiac disorders and other causes of myocardial disease. Systolic function and diastolic function were determined. We gathered demographic, risk factor, clinical, and hemodynamic data on each patient. A multivariate analysis was performed to determine factors important to the development of myocardial disease in the absence of coronary artery disease. Diastolic dysfunction (44%) and systolic dysfunction (25%) were common findings. The 3 risk factors were found most often in black and Hispanic patients, but hypertension and obesity were most severe (P <.001) in black patients. Multivariate analysis indicated that a prior diagnosis of hypertension, level of systolic blood pressure, and severe obesity were the 3 factors independently associated with myocardial disease. CONCLUSIONS: Systolic dysfunction and diastolic dysfunction are common in patients with normal coronary arteries who have hypertension, diabetes, and/or obesity. Because these risk factors are so frequent and severe in the black population, myocardial disease is significantly more common in this segment of the population.

Black or African American↗
PubMed1999

Thrombogenic factors and recurrent coronary events.

BACKGROUND: Thrombosis is a pivotal event in the pathogenesis of coronary disease. We hypothesized that the presence of blood factors that reflect enhanced thrombogenic activity would be associated with an increased risk of recurrent coronary events during long-term follow-up of patients who have recovered from myocardial infarction. METHODS AND RESULTS: We prospectively enrolled 1045 patients 2 months after an index myocardial infarction. Baseline thrombogenic blood tests included 6 hemostatic variables (D-dimer, fibrinogen, factor VII, factor VIIa, von Willebrand factor, and plasminogen activator inhibitor-1), 7 lipid factors [cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, lipoprotein(a), apolipoprotein (apo)A-I, and apoB], and insulin. Patients were followed up for an average of 26 months, with the primary end point being coronary death or nonfatal myocardial infarction, whichever occurred first. The hemostatic, lipid, and insulin parameters were dichotomized into their top and the lower 3 risk quartiles and evaluated for entry into a Cox survivorship model. High levels of D-dimer (hazard ratio, 2.43; 95% CI, 1.49, 3.97) and apoB (hazard ratio, 1.82; 95% CI, 1.10, 3.00) and low levels of apoA-I (hazard ratio, 1.84; 95% CI, 1.10, 3.08) were independently associated with recurrent coronary events in the Cox model after adjustment for 6 relevant clinical covariates. CONCLUSIONS: Our findings indicate that a procoagulant state, as reflected in elevated levels of D-dimer, and disordered lipid transport, as indicated by low apoA-1 and high apoB levels, contribute independently to recurrent coronary events in postinfarction patients.

Adult↗
PubMed1998

Ability of the exercise electrocardiogram test to detect ischemia in stable coronary artery disease patients with ST-segment depression on the resting electrocardiogram.

BACKGROUND: The appearance of ST-segment depression on the exercise electrocardiogram (ETT) generally indicates myocardial ischemia. Disorders that produce ST-segment depression on the resting electrocardiogram can confound the results of the ETT. The purpose of this study was to assess the reliability of exercise ST-segment depression as an indicator of ischemia in patients with a resting electrocardiographic ST depression, presumably caused by coronary disease. METHODS: We studied 882 patients 1 to 6 months after a hospitalization for myocardial infarction or unstable angina as part of the Multicenter Study of Myocardial Ischemia. An ETT and thallium-201 perfusion scan were performed in all patients. For the purpose of this study, the perfusion scan was considered the "gold standard" for ischemia. We correlated the ETT ST-segment responses with the perfusion scan in a group with a normal electrocardiogram baseline ST segment (NO ST DEP group) and in a group with resting electrocardiographic ST depression > or =0.5 mm (ST DEP group). RESULTS: Although the frequency of ischemia by perfusion scan was similar in the ST DEP group (48%) to that in the NO ST DEP group (40%), the ST DEP group had a significantly higher (p = 0.03) sensitivity (54%) in detecting ischemia than the NO ST DEP group (35%). The ST DEP group, however, had a lower (58% vs 74%) specificity than the NO ST DEP group (p = 0.056). Baseline characteristics of the two groups probably account for these differences. The overall diagnostic accuracy is similar (58% vs 56%) in the two groups. CONCLUSION: We conclude that in a stable population with known coronary disease, the presence of ST depression on the resting electrocardiogram does not impair the detection of ischemia by the ETT, but may be associated with a higher false-positive rate.

Adult↗
PubMed1995

Interaction of ischaemia and encainide/flecainide treatment: a proposed mechanism for the increased mortality in CAST I.

OBJECTIVE: To determine whether an interaction between encainide or flecainide and intercurrent ischaemia could account for the observed increase in cardiac and sudden deaths in the study group in the Cardiac Arrhythmia Suppression Trial (CAST) I. DESIGN: CAST I was a randomised, double blind, placebo controlled study in which patients received the drug which suppressed at least 6 premature ventricular contractions per minute by 80% or episodes of non-sustained ventricular tachycardia by 90%. Arrhythmic sudden death or aborted sudden death were the study end points. Measured secondary end points included recurrent myocardial infarction, new or increasing angina pectoris, congestive heart failure, and syncope. The CAST I database was analysed to determine which of three end points occurred first--cardiac death or cardiac arrest, angina pectoris, or non-fatal recurrent infarction. They were regarded as mutually exclusive end points. The triad of cardiac or sudden arrhythmic death plus congestive heart failure and syncope was similarly analysed. RESULTS: It was assumed that recurrent non-fatal infarction and new or increasing angina pectoris were ischaemic in origin. The sum of these non-fatal ischaemic end points and sudden death were nearly identical in the placebo group (N = 129) and the treatment group (N = 131). The one year event rate in each group was 21%. However, the treatment group had a much greater fatality rate (55 v 17; P < 0.0001) than the placebo group. The same relation was found when the data were examined on the basis of drug exposure rather than intention to treat. The temporal and circadian events were similar in each group and were consistent with an ischaemic pattern. No such patterns emerged from analysis of the presumed non-ischaemic end points of congestive heart failure and syncope. CONCLUSIONS: These data suggest that the interaction between active ischaemia and treatment with encainide or flecainide may have been responsible for the increased mortality seen in the treatment group in CAST I. This conversion of a non-fatal to a fatal event emphasises the need for future antiarrhythmic drugs to be screened in ischaemic models.

Angina Pectoris↗
PubMed1993

Long-term prognostic significance of ST segment depression during acute myocardial infarction. The Multicenter Diltiazem Postinfarction Trial Research Group.

OBJECTIVES: The purpose of this study was to evaluate the long-term prognostic value of ST segment depression on the electrocardiogram (ECG) in patients with acute myocardial infarction. BACKGROUND: The prognostic importance of ST segment depression on the ECG has been studied in small groups of patients with infarction, but larger numbers are needed. METHODS: Coronary care unit ECGs of 1,234 patients who survived the coronary care unit with acute Q wave (n = 896) or non-Q wave (n = 338) myocardial infarction were analyzed for the presence of ST segment depression. Patients were followed up for up to 4 years. RESULTS: ST segment depression was present in 607 patients. Those with ST segment depression had a 1-year mortality rate of 10.3% compared with a rate of 5.6% for those without ST segment depression (p = 0.002). This effect was seen in both the Q wave and non-Q wave subgroups. Of the 437 patients with anterior ST segment elevation, those with ST segment depression in other regions had a 13.6% 1-year mortality rate compared with a rate of 6.9% for those with no ST segment depression (p = 0.0005). Of the 514 patients with inferior ST segment elevation, those with ST segment depression in other leads had an 11.0% 1-year mortality rate compared with a 1.8% rate for those with no ST segment depression (p = 0.0001). The Cox proportional hazards model showed that ST segment depression was an independent predictor of mortality over the follow-up period. CONCLUSIONS: ST segment depression on the admitting ECG in patients with acute myocardial infarction is a predictor of increased mortality in the year after infarction.

Adult↗
PubMed1993

An echocardiographic study of the fluid mechanics of obstruction in hypertrophic cardiomyopathy.

OBJECTIVES: The goal of this study was to investigate the hydrodynamic cause of mitral-septal contact and obstruction in patients with hypertrophic cardiomyopathy. BACKGROUND: Mitral-septal apposition has been shown to be the cause of obstruction in patients with hypertrophic cardiomyopathy. With obstruction, characteristic continuous wave Doppler tracings show an increasing acceleration of flow. (Tracing is concave to the left.) METHODS: We studied 24 consecutive patients who had a Doppler echocardiographic pressure gradient > or = 36 mm Hg. We pursued two lines of inquiry. 1) Before the onset of obstruction, we systematically measured the angle between the direction of left ventricular Doppler color flow and the protruding mitral leaflet in early systole. 2) After the onset of obstruction, we qualitatively analyzed the concave contour of the continuous wave Doppler tracings in our patients and developed a hydrodynamic theory of the obstruction phase to explain the characteristic tracings. We present a mathematic model to support this concept. RESULTS: We measured 129 angles. Just before mitral-septal contact, the protruding mitral leaflet projects at a mean 40 degrees and 45 degrees relative to flow in the apical long-axis and apical five-chamber views, respectively. At mitral-septal contact, the obstructing leaflet projects at a mean 52 degrees and 58 degrees relative to flow in the same respective views. Even very early in systole, at leaflet coaptation, 11 of 23 patients had angles > 15 degrees relative to flow. After mitral-septal apposition, obstruction across a cowl-shaped orifice begins. During this stage, the obstructing leaflet projects at a mean 55 degrees and 63 degrees relative to flow. In 22 patients, the continuous wave Doppler tracing of the left ventricular outflow jet showed an increasing acceleration of flow. CONCLUSIONS: Just before mitral-septal contact, the protruding leaflets project at high angles relative to flow. At these high angles, flow drag, the pushing force of flow, is the dominant hydrodynamic force on the protruding leaflet and appears to be the immediate cause of obstruction. The high angle between flow direction and the protruding leaflet precludes significant Venturi effects. Even earlier in systole, at leaflet coaptation, flow drag is dominant in half of the patients, with angles relative to flow > 15 degrees. After obstruction is triggered, it appears from our data and model that the leaflet is forced against the septum by the pressure difference across the orifice. The increasing acceleration of Doppler flow is explained by a time-dependent amplifying feedback loop in which the rising pressure difference across the orifice leads to a smaller orifice and a higher pressure difference.

Adult↗
PubMed1992

Effects of diltiazem on recurrent myocardial infarction in patients with non-Q wave myocardial infarction.

Diltiazem has been reported to reduce the short-term in-hospital reinfarction rate in patients with a non-Q wave myocardial infarction. In the long-term Multicenter Diltiazem Postinfarction Trial, there were 514 patients with non-Q wave myocardial infarction; 279 patients were randomized to the placebo group and 235 to the treatment group. The average follow-up period was 25 months. There was no difference in baseline clinical characteristics between the two groups. Early reinfarction (less than or equal to 6 months) occurred in 17 patients in the placebo group and in 2 patients in the diltiazem group (p less than 0.001). Late reinfarction (greater than 6 months) occurred in 13 patients in the placebo group and in 14 patients in the diltiazem group (p = NS). Initial and reinfarction electrocardiograms (ECGs) were analyzed by using a coding system that permitted identification of standard anatomic areas involved in the infarction process. Thirty-one of the 46 patients had a localized infarction on index and reinfarction ECGs. In the early reinfarction group, 10 (77%) of 13 infarctions occurred in the same ECG region in which the initial infarction had occurred; all 10 were in patients in the placebo group. Among the 18 patients with late reinfarction, the site of the second infarction was the same as that of the first in 9 patients and differed in 9. There was no difference between the placebo and diltiazem groups with respect to location of the infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Cohort Studies↗
PubMed1991

Unsuspected mitral stenosis.

PURPOSE AND PATIENTS AND METHODS: We observed a series of patients in whom the diagnosis of mitral stenosis was first discovered in the echocardiography laboratory. Because of this experience, we examined the records of 152 patients with echocardiographic evidence of rheumatic mitral stenosis to determine the clinical characteristics and course of patients with unsuspected mitral stenosis as well as those factors that may have obscured the diagnosis. RESULTS: Of these 152 patients, 18 had mitral stenosis that was unsuspected clinically until the echocardiogram. These patients were elderly, with a median age of 72 years. They were all referred for echocardiography because of cardiac symptoms. Eight patients were referred for evaluation of congestive heart failure. Five patients were referred for evaluation of aortic valve disease. Three patients were referred because of cerebrovascular accidents and atrial fibrillation. The Doppler-determined mean diastolic mitral gradient ranged from 4 to 15 mm Hg (mean: 7 mm Hg). Mitral stenosis ranged in severity from trivial to very severe. Eight patients had moderate to severe mitral stenosis with estimated mitral valve areas less than or equal to 1.5 cm2. Seven had mild or trivial mitral stenosis with estimated mitral valve areas greater than 1.5 cm2. After further evaluation, two patients underwent mitral valve surgery with improvement of congestive failure. In three patients, warfarin therapy was begun to prevent emboli. Thus, five of 18 patients had a significant immediate change in therapy because of the discovery of mitral stenosis. CONCLUSION: The diagnosis of mitral stenosis may not be suspected in the presence of advanced age, other serious cardiac and medical conditions, or mechanical factors that complicate the physical examination. In these patients, mitral stenosis may be hemodynamically significant and may cause significant symptoms.

Adult↗
PubMed1990

The prognostic significance of first myocardial infarction type (Q wave versus non-Q wave) and Q wave location. The Multicenter Diltiazem Post-Infarction Research Group.

The prognostic significance of the type of first acute myocardial infarction (Q wave versus non-Q wave) and Q wave location (anterior versus inferoposterior) was determined from a multicenter data base involving 777 placebo-treated patients who were participants in the Multicenter Diltiazem Post-Infarction Trial. There were 224 patients (29%) with a non-Q wave infarction, 326 (42%) with an inferoposterior Q wave infarction and 227 (29%) with an anterior Q wave infarction. Mean left ventricular ejection fraction was significantly (p less than 0.001) lower in patients with an anterior Q wave infarction than in the other two groups (anterior Q wave 0.39; inferior Q wave 0.52; non-Q wave 0.53). Nevertheless, the total cardiac mortality rate during the follow-up period (average 25 months per patient) was only marginally higher (p = 0.42) in the anterior Q wave group (8.4%) than in the other two groups (inferoposterior Q wave 7.1%; non-Q wave 6.3%). The total first recurrent cardiac event was somewhat higher (p = 0.08) in the anterior Q wave group (18.1%) than in the other two groups (inferoposterior Q wave 11.7%; non-Q wave 15.6%). Survivorship analyses extending over 3 years revealed that electrocardiographic classification of the type of first infarction and Q wave location did not make significant independent contributions to the risk of postinfarction cardiac death or first recurrent cardiac event, either before or after adjustment for baseline clinical variables.

Adult↗
PubMed1990

The predictive accuracy of the electrocardiogram in identifying the presence and location of myocardial infarction and coronary artery disease.

In summary, the electrocardiogram is limited in its ability to detect a myocardial infarction. Its sensitivity is compromised seriously by a substantial number of patients (table; see text) with non-Q wave infarction or regression of Q waves. Once a Q wave occurs, the predictive accuracy of those changes, in delineating the location of the infarction, is quite high. The ability of Q waves or ST segment elevation to predict or identify the "culprit artery" is less strong, primarily due to the variation in coronary anatomy commonly found. The relationship between anterior or inferior lead changes and anterior or inferior myocardial damage is close. However, lateral lead changes may more accurately represent anterolateral (I, AVL) or apical (V5-V6) infarction. Tall R waves in anterior precordial leads is most often associated with posterolateral infarction.

Coronary Vessels↗
PubMed1989

Clinical characteristics and natural history of survivors of pulmonary congestion during acute myocardial infarction. The Multicenter Postinfarction Research Group.

Although pulmonary congestion during acute myocardial infarction (AMI) is recognized as an important adverse event, the detailed clinical features, natural history and predictive value of standard diagnostic tests in such patients have not been well characterized. As part of a multicenter prospective postinfarction trial, 123 patients with pulmonary congestion during AMI, who survived and were discharged from the coronary care unit, were studied. These patients were compared with similar patients who did not develop pulmonary congestion. Patients with pulmonary congestion had a significantly higher 1-year mortality rate compared with 744 patients without pulmonary congestion during AMI (28 vs 5.5%). Patients with pulmonary congestion were characterized by a lower ejection fraction, more frequent anterior infarction, diminished ability to perform exercise testing and higher incidence of subsequent cardiac events. Even without these variables, pulmonary congestion was associated with increased mortality. In patients with pulmonary congestion, ejection fraction (dichotomized at 30%) and exercise testing were the most discriminating tests in risk stratification. An ejection fraction greater than 30% and completion of the exercise test was associated with a 7% mortality while an ejection fraction less than 30% and inability to take or complete the exercise test was associated with a 44% 1-year mortality. A greater incidence of reinfarction, ischemia during exercise and ischemic events at the time of death in the pulmonary congestion group suggests that ischemia may be an important factor in this high risk category.

Aged↗
PubMed1989

Risk stratification in patients with first non-Q wave infarction: limited value of the early low level exercise test after uncomplicated infarcts. The Multicenter Post-Infarction Research Group.

Risk stratification using clinical and historical variables plus early low level exercise testing was performed in 141 patients with a first non-Q wave myocardial infarction. The 111 patients who performed the exercise test had a 3.6% cardiac mortality rate in the first year compared with 13.3% in the 30 patients who could not exercise (p = 0.063), and a 1 year incidence rate of recurrent cardiac events (cardiac death or recurrent nonfatal myocardial infarction) of 10.8% compared with 23.3% (p = 0.127). Patients who developed ischemia (ST depression or angina) during the test had an increased incidence of cardiac events in the year after the infarction (odds ratio greater than 3, p less than 0.05). When patients were subgrouped by the presence or absence of pulmonary congestion, the discriminatory value of the exercise test was seen to reside primarily in the cohort with pulmonary congestion. For example, ST depression during exercise in this group identified patients with a 71% incidence of cardiac events in the year after the infarction compared with 5.3% for those without ST depression (odds ratio 45, p = 0.002). In the patients without pulmonary congestion, the exercise test had no discriminatory value. It is concluded that early low level exercise testing has a limited role after an uncomplicated non-Q wave infarction, but is useful in patients with clinical markers of higher risk.

Electrocardiography↗
PubMed1988

After the myocardial infarction: a review and approach to risk stratification.

Each patient who is stricken with a myocardial infarction should be evaluated with respect to future risk. Risk stratification should be carried out early after the acute infarction since the majority of excess deaths occur early after discharge. Clinical observations and several properly selected noninvasive procedures will classify most patients into high or low risk.

Cardiac Complexes, Premature↗
PubMed1987

A new electrocardiographic classification for post-myocardial infarction clinical trials.

A new electrocardiographic code was developed for clinical trials involving patients with acute myocardial infarction (AMI). In the Multicenter Post-Infarction Program (MPIP), the electrocardiogram, classified by the Minnesota code, was not useful as a clinical predictor and played almost no role in subsequent analysis. To test its value the new code was applied to the electrocardiograms of 653 of the 866 patients in the MPIP data base who had sustained a first AMI. The MPIP code identifies AMI by region and severity. The 4 regions are anterior, lateral, inferior and posterior, defined by traditional criteria. Severity codes include Q-wave and non-Q-wave AMI, ST depression and no ischemic changes. The interpretation for each of 4 regions results in a 4-digit location severity code that is amenable to sorting and analysis. Fourteen separate and mutually exclusive groups were identified. Mortality gradients were found within the inferior AMI groups, but not within the anterior AMI groups. Mean ejection fraction was 50% for patients with isolated anterior infarction and decreased progressively (p less than 0.0003) as the extent of lateral wall involvement increased. For isolated inferior AMI, mean ejection fraction was 53%; lateral or posterior involvement did not significantly change this. The MPIP code is easy to apply, correlates acceptably well with clinically relevant variables of left ventricular function and permits the electrocardiogram to be used as a clinical predictor in large clinical trials.

Clinical Trials as Topic↗
PubMed1986

Association between transient pulmonary congestion during acute myocardial infarction and high incidence of death in six months.

In a prospective multicenter study of 866 patients after acute myocardial infarction (AMI), an increased or excessive mortality rate (13%) was confined to the first 6 months after AMI. In the subsequent 18 months of follow-up, the mortality rate (4%) was similar to that in coronary patients in chronic stable condition. Analysis of patients who died in the first 6 months revealed that 55% had had pulmonary congestion at the time of the index AMI. Neither these patients nor the others who died in the early period were found to have more severe ventricular dysfunction, more malignant arrhythmias or more severe ischemia than patients who died after 6 months. The reason for the high and early mortality in patients with pulmonary congestion is not clear, particularly because 30% had reasonable ventricular function, with an ejection fraction of more than 40%. However, given the poor prognosis of these patients, early and aggressive diagnostic efforts should be undertaken to exclude jeopardized regions remote from the initial AMI.

Arrhythmias, Cardiac↗