Effect of oral propranolol on rest, exercise and postexercise left ventricular performance in normal subjects and patients with coronary artery disease

Resting β-Adrenergic Blockade Does Not Alter Exercise Thermoregulation in Children With Burn Injury: A Randomized Control Trial

The objective of this study was to test the hypothesis that propranolol, a commonly prescribed β-blocker to burned children, in combination with exercise-heat stress, increases the risk of heat illness and exercise intolerance. In a randomized double-blind study, propranolol was given to 10 burned children, and placebo was given to 10 additional burned children (matched for TBSA burned; mean ± SD, 62 ± 13%), while nonburned children served as healthy controls. All groups were matched for age and body morphology (11.2 ± 3.0 years; 146 ± 19 cm; 45 ± 18 kg; 1.3 ± 0.4 m2). All children exercised in hot conditions (34.3 ± 1.0°C; 26 ± 2% relative humidity) at 75% of their peak aerobic capacity. At the end of exercise, none of the groups differed for final or change from baseline intestinal temperature (38.0 ± 0.5°C; 0.02 ± 0.01Δ°C·min-1), unburned (37.0 ± 0.6°C) and burned skin temperatures (36.9 ± 0.7°C; nonburn group excluded), heat loss (21 ± 18 W m-2), whole-body thermal conductance (118 ± 113 W m-2), or physiological strain index (5.6 ± 1). However, burn children exercised less than nonburn group (21.2 ± 8.6 vs 30 ± 0.0 min; P < .001) and had a lower calculated exercise tolerance index (1.0 ± 0.0 vs 6.7 ± 4.3; P < .01). Burned children had lower peak heart rates than nonburned children (173 ± 13 vs 189 ± 7 bpm; P < .01), with greater relative cardiac work rates at the end of exercise (97 ± 10 vs 85 ± 11% peak heart rate; P < .01). Resting β-adrenergic blockade does not affect internal body temperature of burned children exercising at similar relative intensities as nonburn children in the heat. Independent of propranolol, a suppressed cardiac function may be associated to exercise intolerance in children with severe burn injury.

Testing the Translational Power of the Zebrafish: An Interspecies Analysis of Responses to Cardiovascular Drugs

The zebrafish is rapidly emerging as a promising alternative in vivo model for the detection of drug-induced cardiovascular effects. Despite its increasing popularity, the ability of this model to inform the drug development process is often limited by the uncertainties around the quantitative relevance of zebrafish responses compared with nonclinical mammalian species and ultimately humans. In this test of concept study, we provide a comparative quantitative analysis of the in vivo cardiovascular responses of zebrafish, rat, dog, and human to three model compounds (propranolol, losartan, and captopril), which act as modulators of two key systems (beta-adrenergic and renin–angiotensin systems) involved in the regulation of cardiovascular functions. We used in vivo imaging techniques to generate novel experimental data of drug-mediated cardiovascular effects in zebrafish larvae. These data were combined with a database of interspecies mammalian responses (i.e., heart rate, blood flow, vessel diameter, and stroke volume) extracted from the literature to perform a meta-analysis of effect size and direction across multiple species. In spite of the high heterogeneity of study design parameters, our analysis highlighted that zebrafish and human responses were largely comparable in >80% of drug/endpoint combinations. However, it also revealed a high intraspecies variability, which, in some cases, prevented a conclusive interpretation of the drug-induced effect. Despite the shortcomings of our study, the meta-analysis approach, combined with a suitable data visualization strategy, enabled us to observe patterns of response that would likely remain undetected with more traditional methods of qualitative comparative analysis. We propose that expanding this approach to larger datasets encompassing multiple drugs and modes of action would enable a rigorous and systematic assessment of the applicability domain of the zebrafish from both a mechanistic and phenotypic standpoint. This will increase the confidence in its application for the early detection of adverse drug reactions in any major organ system.

The effect of atenolol on the left ventricular performance in patients with angina pectoris measured with isotope technique

Working capacity, left ventricular ejection fraction (EF), stroke volume and the phase of the left ventricular contraction were tested before and after 3 weeks of atenolol treatment in 14 patients with angina pectoris and coronary insufficiency diagnosed by thallium tomography. Eight patients (group A) increased their EF during exercise and six patients (group B) showed a decrease in EF when tested with placebo. When treated with atenolol the changes in EF during exercise were reversed in the two groups. Group B increased and group A decreased their EF. Atenolol caused an increase in working capacity in group B, but not in group A. In both groups atenolol caused an increased stroke volume and a decreased phase deviation at rest, while no significant volume changes or phase changes occurred during exercise. These results indicate that atenolol treatment had the most marked effect in patients with the most pronounced disease.

The sensitivity of the symptom angina pectoris as a marker of transient myocardial ischaemia in chronic stable angina pectoris

Therapeutic decisions in patients with angina pectoris are traditionally based on the history reported by the patient, since objective evidence of myocardial ischaemia during daily life is often not available. In this study, ambulatory ST segment monitoring was performed in 60 patients with a history of chronic stable angina pectoris, positive exercise test and/or positive coronary angiography, and a correlation was made between the episodes of chest pain and ST segment change. The patients were grouped according to the results of exercise testing and coronary arteriography, and one group was studied with and without antianginal medication. Overall, 195 episodes of angina were noted, only 94 of which (48%) were accompanied by ST segment depression. Pain and ST segment changes were best correlated in patients with a positive exercise test, positive angiography and who were not receiving antianginal medication. In 101 episodes of chest pain, ST segment change could not be identified; in 18 (18%) there was sinus tachycardia, in 12 (12%) ventricular premature beats, and in 71 (70%) sinus rhythm solely. Thus, anginal pain appears not to be the reliable indicator of transient myocardial ischaemia as was previously thought, a finding which supports the use of objective methods in identifying episodes of transient myocardial ischaemia in daily life.

Peri-operative beta-blockade and haemodynamic optimisation in patients with coronary artery disease and decreasing exercise capacity presenting for major noncardiac surgery

Patients with coronary artery disease presenting for major noncardiac surgery may have indications for both peri-operative beta-blockade and haemodynamic optimisation. The combination of peri-operative cardiorespiratory failure and myocardial ischaemia has a grave prognosis. Recent investigations have shown that in patients with coronary artery disease, beta-blockade does not depress cardiac output as much as originally thought. There may, therefore, be a place for both peri-operative beta-blockade and haemodynamic optimisation. The indications for peri-operative beta-blockade and haemodynamic optimisation, the effect of acute beta-blockade on cardiac output in patients with coronary artery disease, and the interaction of peri-operative beta-blockade and haemodynamic optimisation are discussed.

Amlodipine reduces myocardial ischaemia during exercise without compromising left ventricular function in patients with silent ischaemia: a randomised, double-blind, placebo-controlled study

BACKGROUND

Left ventricular systolic function is reduced during episodes of silent ischaemia in patients with coronary artery disease (CAD). In most normal subjects left ventricular ejection fraction (LVEF) increases at least 5% during exercise whereas LVEF often remains unchanged or decreases in patients with CAD. The anti-ischaemic effect of calcium antagonists is well documented including a capability to reduce exercise-induced electrocardiographic ST-depressions, whereas the effect of these drugs on LV volume changes during exercise in patients with silent ischaemia is unknown.

AIM

The aim of this study was to evaluate the effect of amlodipine on rest and exercise LVEF in patients with silent ischaemia.

METHODS

Twenty-one patients completed a double-blind placebo-controlled cross-over study. Conventional exercise test and radionuclide cardiographies during exercise were used for determining haemodynamic parameters.

RESULTS

Exercise-induced electrocardiographic ST-depressions were reduced in 83% of the patients having ST-deviations during placebo even though 10 patients were already treated with a beta-blocker. Amlodipine did not affect left ventricular systolic function compared to placebo, neither at rest nor during exercise.

CONCLUSION

The results indicated that amlodipine is a safe anti-ischaemic drug in patients with silent ischaemia concerning cardiac function.

Metoprolol abolishes exercise-induced left ventricular dysfunction in patients with silent ischemia

Left ventricular systolic function is reduced during episodes of silent ischemia in patients with coronary artery disease (CAD). Left ventricular ejection fraction (LVEF) is increased at least 5 absolute percent during exercise in most normal subjects; however, in patients with CAD, LVEF often remains unchanged or decreases. The anti-ischemic effect of beta-adrenergic receptor blockade is well documented, including a reduction of exercise-induced electrocardiographic ST depressions; however, the effect of these drugs on left ventricular volume changes during exercise in patients with silent ischemia is unknown. The aim of this study was to evaluate the effect of a cardio-selective beta-blocking agent, metoprolol, on rest and exercise LVEF in patients with silent ischemia, using radionuclide cardiography. Fifteen patients with silent ischemia completed a double-blind, placebo-controlled crossover study at rest and during submaximal exercise. LVEF remained unchanged during exercise in the placebo phase (56% to 58%; p = NS), but even though LVEF tended to decrease 56% during rest after metoprolol versus 52% after placebo (p = NS), the LVEF increase from rest to exercise resembled a normal LVEF response, 52% to 58% (p = 0.005). Exercise-induced electrocardiographic ST depressions were also reduced during metoprolol treatment. In patients with silent ischemia, the exercise-induced change in LVEF rises significantly during metoprolol treatment. The mechanism may be a reduction in myocardial ischemia as indicated by a reduction in ischemic electrocardiographic findings.

Objective assessment of "cardioprotective" efficacy as a prognostic guide to management of mildly symptomatic revascularizable coronary artery disease

OBJECTIVES

The concept of "cardioprotection" based on ejection fraction was tested to see whether patients with coronary artery disease in whom medical treatment fails to be cardioprotective can be distinguished from those in whom it is safe to continue such treatment.

BACKGROUND

Ejection fraction is of fundamental prognostic importance. Its modification by anti-ischemic medication may allow assessment of cardioprotection from adverse outcome.

METHODS

Exercise ejection fraction and the change in ejection fraction from rest to exercise were measured by radionuclide ventriculography with and without background medication in 102 mildly symptomatic patients with coronary artery disease suitable for revascularization but initially treated medically.

RESULTS

Over 20 months, 23 patients experienced an adverse event. With medication, exercise ejection fraction increased in patients with and without events. By contrast, the ejection fraction response to exercise improved significantly in the event-free group only; the group with events had a persistent decrease in ejection fraction. By Cox analysis, the ejection fraction response to exercise performed with medication made the most significant independent contribution to event-free survival. Comparison of areas under receiver operating characteristic curves suggested that this index is the most useful clinical measure of cardioprotection.

CONCLUSIONS

An exercise-induced decrease in ejection fraction despite anti-ischemic medication implies failure of cardioprotection and a greater short-term risk of adverse outcome and crossover to revascularization in patients initially treated medically. Conversely, a preserved left ventricular performance confers a satisfactory prognosis while continuing with that treatment. Thus, the effect of medication on the ejection fraction response to exercise--a reasonable estimate of its cardioprotective efficacy--may influence the choice of continuing with such treatment or performing early revascularization.

Beta receptor antagonists in the treatment of heart failure

The use of beta-receptor antagonists in the treatment of heart failure is controversial. Available data do not allow general recommendations regarding their use. In dilated cardiomyopathy, several studies suggest that long-term treatment in individual patients reduces symptoms and increases exercise capacity. Short-term treatment is usually not beneficial, except in patients with ischemically induced left ventricular dysfunction. In heart failure, post myocardial infarction and in chronic ischemic heart disease, no proper long-term study has been performed to evaluate its effects. However, patients with acute myocardial infarction tolerate beta blockers, despite the presence of left ventricular dysfunction and long-term prognosis is improved. Newer agents, some with ancillary properties, such as intrinsic activity and vasodilatation, may have advantages. In the future we need a better description of the cardiac status in our patients in order to be able to select those that will respond favorably to beta-receptor antagonists. The mechanisms by which some patients improve are still obscure. Protection against receptor downregulation, restoration of receptor density, protection against cardiotoxicity of catecholamines, and improvement in ischemic systolic and diastolic left ventricular function are all possible. The fear that beta-receptor antagonists are dangerous in heart failure is in most instances not warranted, but an initial deterioration may have to be accepted in order to gain long-term beneficial effects. Ongoing studies in both idiopathic cardiomyopathy and in postinfarction failure will hopefully help us to define the use of beta-adrenoceptor antagonists in the future.

Multicenter evaluation of the hemodynamic effects of bisoprolol in patients with mild to moderate hypertension

Twenty-six patients with mild-to-moderate essential hypertension participated in a 6-week outpatient, multicenter, randomized, double-blind, placebo-controlled two-way crossover study to assess the hemodynamic effects of bisoprolol (20 mg QD) at steady state. Hemodynamic assessments included sitting blood pressure, heart rate, and left-ventricular ejection fraction by radionuclide ventriculography after 7 days of bisoprolol or placebo at trough (24 h post-dose) and peak (3 h post-dose) values. The group adjusted mean ejection fraction was not significantly different in patients receiving bisoprolol compared with the placebo group at either peak or trough measurements; in fact, means in patients taking bisoprolol were slightly higher than in the placebo group. No symptomatic hypotension was documented. Blood pressure, measured 24 hours after dosing, was significantly lower in those receiving bisoprolol when compared with the placebo group, by 7.7 mm Hg and 9 mm Hg for diastolic and systolic blood pressure, respectively. Similarly, mean values of heart rate were 10 beats/min lower in the bisoprolol patients than in the placebo group. Only headache and insomnia occurred as adverse events. Bisoprolol (20 mg QD) effectively lowered blood pressure over a 24-hour period without significantly reducing ejection fraction or causing adverse clinical or biochemical events.

Effects of exercise on blood flow to canine articular tissues

We measured articular blood flow by standard microsphere techniques in normal adult dogs at rest and during treadmill exercise. All animals but one underwent beta-adrenergic blockade as part of another experimental protocol. Expressed in microliter/min/g +/- SEM, baseline flow values to articular tissues were: knee synovium 26 +/- 4, femoral condyle 130 +/- 21, tibial plateau 182 +/- 29, articular fat pad 9 +/- 2, knee ligaments 17 +/- 3, menisci 34 +/- 6, wrist synovium 19 +/- 4, distal radius 65 +/- 13, and lunate bone 59 +/- 13. Blood flow increased with exercise in all soft tissues of both the knee (stifle joint) and the wrist (radiocarpal joint). Geometric mean exercise/rest flow ratios ranged from a low of 1.44 (p less than 0.05) in the menisci of the knee to a high of 7.25 (p less than 0.001) in the synovium of the wrist. In contrast, blood flow did not rise in juxtaarticular bones and fell significantly in femoral condyles (mean flow ration 0.71, p less than 0.005). These findings indicate that articular soft tissues derive increased perfusion from the redistribution of blood flow that accompanies short-term exercise. In contrast, flow to juxtaarticular bone does not increase under these conditions.

Hemodynamic effects of intravenous and oral sotalol

Beta-adrenergic blocking agents may have negative inotropic effects that are particularly worrisome in patients with depressed cardiac function. Their membrane-stabilizing properties may be a contributing factor. Sotalol is currently thought not to cause significant myocardial depression. Intravenous sotalol administration has minimal effects on resting stroke volume, although heart rate and consequently cardiac output are significantly decreased. Systolic blood pressure decreases, with a minimal change in diastolic or mean pressure. Hemodynamic effects are usually seen within 15 to 20 minutes of administration. Hemodynamic indexes are maintained even in patients with mildly depressed ejection fractions (mean ejection fraction of 43 +/- 15%) after oral sotalol administration. Although heart rate decreases, cardiac index is unchanged because of a significant increase in stroke volume index. The latter results from an increase in preload (secondary to bradycardia) and a decrease in afterload. Sotalol is well tolerated, although occasionally it may cause worsening heart failure. This is seen in patients with markedly depressed left ventricular function and inadequate cardiac reserve characterized by an inability to increase stroke volume and cardiac output with exercise. Long-term (1-year) patient follow-up reveals no significant hemodynamic deterioration from initial values obtained after oral administration.

The application of radionuclide ventriculography to cardiac screening

Screening asymptomatic individuals for latent coronary disease often requires sequential testing because exercise electrocardiography typically produces more false positive than true positive results in a population with a low prevalence of coronary disease. Cardiac scintigraphy is a technique that may be employed as a confirmatory test in lieu of coronary arteriography to further evaluate the significance of a positive exercise electrocardiogram. Radionuclide ventriculography was employed in 98 asymptomatic individuals who were considered to be at moderate risk of heart disease after risk factor analysis and exercise electrocardiography. Seventeen (17%) patients had an abnormal study and underwent cardiac catheterization. Seven had coronary artery disease, two had cardiomyopathy, and eight were normal. Eighty-one (83%) patients had a normal study. Because the sensitivity of radionuclide ventriculography is 63-80%, it was postulated that 2 to 5 individuals with disease were missed. Thus, from a population with an 11-14% prevalence of disease, two subsets were identified. A large subset in which a prevalence of 2-6% could be estimated was separated from a much smaller one in which a prevalence of approximately 50% was demonstrated.

Doxorubicin cardiotoxicity: response of left ventricular ejection fraction to exercise and incidence of regional wall motion abnormalities

Gated radionuclide ventriculograms were performed to evaluate cardiac function in 53 patients who received doxorubicin treatment for various malignancies (mean dose: 449 +/- 128 mg/m2 BSA). In fourteen patients (Group I) function was evaluated before and after treatment; there was a significant decrease of resting left ventricular ejection fraction after therapy (p less than 0.001). Twenty-two patients (Group II) had serial studies during treatment which also showed a significant fall of resting left ventricular ejection fraction (p less than 0.001). Eighteen patients in Groups I and II had supine exercise studies. A normal exercise response was maintained in the majority of patients. Exercise testing added little to the diagnostic performance when compared to serial resting studies. We found regional wall motion abnormalities (mild apical hypokinesis) at rest by visual inspection in 33 of 36 Group I and Group II patients who had received doxorubicin. In the baseline or initial study, only 4 of these patients demonstrated WMA. In 18 Group I and II patients who were exercised, 3 had wall motion abnormalities during the initial study. All of these patients demonstrated wall motion abnormalities at rest after the second study, however only 7 of 18 demonstrated abnormalities during the exercise study. The results indicate that resting left ventricular ejection fraction declines after doxorubicin treatment. Exercise radionuclide angiography may not increase diagnostic accuracy for the detection of doxorubicin related cardiotoxicity. Regional wall motion abnormalities occur with a relatively high incidence following doxorubicin therapy, more readily detectable at rest. However, the exercise study can distinguish doxorubicin related wall motion abnormalities from those due to coronary artery disease.

Prognosis in patients with an abnormal exercise radionuclide angiogram in the absence of significant coronary artery disease

To investigate the prognostic importance of abnormal exercise left ventricular function on radionuclide angiography in the absence of significant angiographic coronary artery disease, 79 consecutive patients with these findings were followed up for a mean of 25 months (range 12 to 55). All patients had 1) an ejection fraction at rest greater than or equal to 0.40, 2) an ejection fraction that decreased with exercise or peak exercise ejection fraction less than 0.60, and 3) no significant coronary artery disease. The mean change in ejection fraction was a decrease of 0.07. In 63 patients (80%), the ejection fraction decreased during exercise; in 45 patients, it decreased by greater than or equal to 0.05. Twenty patients (25%) had a peak exercise ejection fraction less than 0.50. All patients were alive at follow-up study. One patient had a nonfatal myocardial infarction, and three patients were hospitalized for recurrent chest pain. No patient underwent coronary angioplasty or bypass surgery. The calculated infarction-free survival rate at 4 years by life table analysis was 97%. Patients with an abnormal exercise radionuclide angiogram in the absence of significant angiographic coronary artery disease have an excellent short-term prognosis.

The relationship between left ventricular systolic function and congestive heart failure diagnosed by clinical criteria

There is no uniformly accepted clinical definition for congestive heart failure (CHF), although criteria have been published by various groups. There is also no reference standard for CHF, although left ventricular ejection fraction (LVEF) gives a quantitative assessment of systolic function and is useful in predicting prognosis. To determine the relationship between LVEF and clinically diagnosed CHF, we compared resting LVEF determined by radionuclide ventriculography with diagnosis of CHF by clinical criteria in 407 patients, based on clinical data collected by a cardiology fellow. Of 153 patients with a low LVEF (less than or equal to 0.40), 30 (20%) met none of the criteria for CHF. Conversely, of 204 patients with normal LVEF (greater than or equal to 0.50), 105 (51%) met at least one of the criteria. We conclude that different criteria for CHF will have varying utility depending on the population being examined, and that a combination of clinical features and an objective measure of cardiac performance is needed to diagnose CHF.

Long term inotropic effects of flecainide and propafenone

This study was undertaken to evaluate the effect of flecainie (Fle) and propafenone (Pro) on rest and exercise myocardial contractility after prolonged oral administration. Standardized, fully automated, gated radionuclide angiograms at rest and during maximum exercise were performed single blinded and prospectively in 19 patients before and after oral treatment with either 150 mg b.i.d. of Fle or 150 mg t.i.d. of Pro. The left ventricular ejection fraction (EF%) as a hemodynamic indicator presented as follows: (Table: see text) In general, there was no significant effect of either drug on resting ventricular function. In only one patient of the Fle group with decreased baseline function did the left ventricular EF fall from 40% to 29%. During exercise, ventricular performance showed deterioration in the Pro group, but, interestingly, improvement in the Fle group. As a result of these opposite changes, the effect of the two drugs on the exercise response of ventricular function was significantly different (P less than 0.05). This study thus gives first evidence that no significant cardiodepressive effects are to be expected after prolonged application of Fle or Pro in normal hearts. There might even be a mild beneficial effect on exercise performance after Fle.

Quantitative radionuclide angiocardiography

Quantitation of cardiac pump function using radionuclide angiocardiography provides objective information for the management of patients with heart disease. Left and right ventricular ejection fraction, stroke volume ratio, ejection rate, diastolic function, ventricular volume, parametric imaging, amplitude and phase analysis, and shunt quantification can be measured from the radionuclide angiocardiogram at rest, during exercise, and during pharmacologic interventions. This review describes these methods and discusses their reliability and their role in the clinical assessment of patients with cardiac disease.

Effects of exercise tolerance, age, and gender on the specificity of radionuclide angiography: sequential ejection fraction analysis during multistage exercise

We investigated the factors that determine the left ventricular ejection fraction response to exercise in 57 middle-aged, untrained patients with angiographically normal coronary arteries. The ejection fraction was measured by blood pool radionuclide angiography during each stage of exercise. Stepwise regression analysis was applied to 39 variables, and the resulting significant variables were then included in a logistic regression model to determine which of them would predict a normal ejection fraction response. By stepwise regression analysis, the best model (F = 5.6, p = 0.0004) was obtained by combining four variables: achieving 85% of maximal predicted heart rate, peak heart rate, number of exercise stages performed, and resting pulse pressure. Only the latter two variables were significant by logistic regression analysis. The specificity of greater than or equal to 5 ejection fraction unit increase at peak exercise was 42%, 75%, and 100% in patients who exercised one, two, or three stages, respectively. Furthermore, the increase in ejection fraction during each exercise stage was independent of age or gender. Thus the standard criteria of normality during exercise radionuclide angiography have high specificity only when applied to patients with good exercise performance, regardless of age or gender.

The detection of coronary artery disease: a comparison of exercise thallium imaging and exercise equilibrium radionuclide ventriculography

This study compared the accuracy of rest and exercise gated equilibrium technetium ventriculography with exercise thallium imaging in 50 consecutive male patients undergoing routine coronary angiography for the evaluation of chest pain. No patients were excluded on the basis of prior myocardial infarction, nature of angiographically defined coronary disease or symptoms. Antianginal therapy was continued in all patients. Eight patients had normal coronary arteries, 9 had single vessel, disease, 20 had double vessel disease and 13 had triple vessel disease. Sixteen patients had previously documented myocardial infarction. Using exercise radionuclide ventriculography, 34 patients with coronary disease were detected resulting in a sensitivity of 81%; 6 patients with normal coronary arteries had normal scans, a specificity of 75%, with a predictive accuracy of 80%. In comparison, thallium imaging detected 42 patients with coronary disease resulting in a sensitivity of 100%. Six patients with normal coronary arteries had normal thallium images resulting in a specificity of 75% and a predictive accuracy of 96%. These results suggest that exercise thallium imaging is a more accurate investigation than exercise equilibrium radio-nuclide ventriculography and is the investigation of choice in the noninvasive detection of coronary artery disease.

Lack of effect of low levels of carboxyhemoglobin on cardiovascular function in patients with ischemic heart disease

We studied 30 patients 38-75 yr of age who had ischemic heart disease to assess the effect of acute elevation of carboxyhemoglobin (COHb) concentration. Patients were nonsmokers with ischemia defined by exercise-induced ST depression (ST decreases)--25/30, angina--23/30, or abnormal ejection fraction (EF) response--18/30. After an initial familiarization and exercise session patients were exposed to air (carboxyhemoglobin [COHb] = 1.5 +/- 0.05%) and to carbon monoxide (CO) (100 ppm-COHb-average = 3.8 +/- 0.1%) on successive days in a double blind, randomized fashion. There was no significant difference in time to onset of angina (air = 312 sec, CO = 306 sec), maximal exercise time (air = 711 sec, CO = 702 sec), maximal ST decreases (1.5 mm for both), or time to significant ST decreases (air = 474 sec, CO = 475 sec). Double product at ST decreases and maximal double products were similar for both conditions. Resting ejection fraction was slightly but nonsignificantly higher after CO exposure (air = 53.9%, CO = 55.2%). Maximal ejection fraction was similar for both conditions (air = 57.4%, CO = 57.1%). Change in ejection fraction was slightly lower for CO exposure (air = 3.5%, CO = 2%), p = .049. In conclusion, there is no clinically significant effect of 3.8% COHb (representing a 2.2% increase from resting values) on the cardiovascular system in this study.

Effects of beta blockade on systolic and diastolic left ventricular function at rest and during exercise in patients with chronic stable angina pectoris

This study examined the effects of beta blockade with betaxolol, a cardioselective, lipid-soluble, beta-adrenergic-blocking agent, on rest and exercise systolic and diastolic left ventricular function in 15 patients, aged 40 to 70 years (mean = 52), with chronic stable angina pectoris. Each patient underwent three upright exercise studies at identical workloads; the first was a baseline study, the second was done 3 hours after a single oral dose, and the third was obtained after chronic therapy for 2 weeks. Beta blockade was evident by significant decreases in heart rate, systolic blood pressure, and diastolic blood pressure at rest and during exercise (p less than 0.04). Although there were no significant changes (at rest or during exercise) in mean left ventricular ejection fraction and peak filling rate, individual variations were seen after 3 hours and 2 weeks of therapy. During chronic therapy, the peak filling rate increased in three patients, decreased in five, and remained unchanged in seven. Also, discordant changes in systolic and diastolic functions were seen at rest and during exercise during both acute and chronic therapy. Thus, although acute and chronic beta blockade produces no significant changes in mean measurements of diastolic and systolic left ventricular performance, individual variations and discordant results are seen in many patients. The acute effects are generally consistent with the chronic effects, but exceptions are present.

Left ventricular geometry and function in adults with Ebstein's anomaly of the tricuspid valve

We postulated that the abnormal shape, size, and function of the right heart and adjoining ventricular septum in adults with Ebstein's anomaly of the tricuspid valve might in turn alter the shape and function of the left ventricle. Seven adult patients with uncomplicated Ebstein's anomaly were studied. Left ventricular geometry was determined by two-dimensional echocardiography. Left ventricular function was assessed by treadmill exercise and radionuclide angiography at rest and with exercise. Paradoxic ventricular septal motion was consistently present. Left ventricular eccentricity (ratio of two minor axes in the short-axis view) was uniformly abnormal, averaging 1.35 +/- 0.23 (normal = 1.02 +/- 0.05). The ratio of right to left ventricular cavity size averaged 1.70 +/- 0.44 (normal 0.65 +/- 0.30), and tricuspid valve displacement into the right ventricular cavity averaged 52% (normal 8%). Functional right atrial size averaged 27.6 +/- 5.2 cm2 (normal right atrial area = 13.1 +/- 2.2 cm2). Resting left ventricular ejection fractions were below 50% in all but two patients. In response to Bruce protocol exercise stress, there were consistently appropriate increments in heart rate, blood pressure, and peak double product and, with one exception, radionuclide left ventricular ejection fraction. There were significant correlations between tricuspid valve displacement and functional right atrial size versus resting left ventricular ejection fraction and left ventricular eccentricity. These data support the hypothesis that derangements in right heart morphology and function in Ebstein's anomaly contribute to significant alterations in left ventricular geometry, but the geometric alterations are associated with tangible but less significant changes in left ventricular systolic function.

Comparison of nifedipine alone with propranolol alone for stable angina pectoris including hemodynamics at rest and during exercise

The effects of nifedipine (60 to 90 mg/day) and propranolol (240 mg/day) on symptoms, angina threshold and cardiac function were compared in a placebo-controlled, double-blind, crossover study. Five-week treatment periods with nifedipine and propranolol were compared with 2 weeks of placebo treatment in 21 men with chronic stable angina pectoris, 13 of whom had symptoms both at rest and on exertion. Compared with placebo, New York Heart Association functional class improved in patients equally with nifedipine (p = 0.001) and propranolol (p = 0.006). Frequency of chest pain decreased with nifedipine (p = 0.001) and propranolol (p = 0.01), and nitroglycerin consumption similarly decreased with both treatments. Nifedipine significantly delayed the onset of chest pain (p = 0.01) and 1 mm of ST-segment depression (p = 0.002) during bicycle exercise; smaller increases with propranolol were not statistically significant. A preferential clinical response to nifedipine (9 patients) or propranolol (6 patients) was unrelated to the presence or absence of pain at rest or to any baseline hemodynamic finding. Nifedipine and propranolol were equally effective in relieving exertional ischemia as shown by improvements in ejection fraction at identical workloads, from 0.48 +/- 0.11 to 0.58 +/- 0.12 (p less than 0.001) and 0.56 +/- 0.14 (p less than 0.001), respectively. Exercise wall motion, assessed by a semiquantitative wall motion score, also improved with both drugs. Propranolol treatment decreased exercise cardiac output by 14% (p = 0.01) through its effect on heart rate. In contrast, nifedipine treatment had no effect on cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversibility of cardiac wall-motion abnormalities predicted by positron tomography

Positron emission tomography (PET) can be used with nitrogen-13-ammonia (13NH3) to estimate regional myocardial blood flow, and with fluorine-18-deoxyglucose (18FDG) to measure exogenous glucose uptake by the myocardium. We used PET to predict whether preoperative abnormalities in left ventricular wall motion in 17 patients who underwent coronary-artery bypass surgery were reversible. The abnormalities were quantified by radionuclide or contrast angiography or both, before and after grafting. PET images were obtained preoperatively. Abnormal wall motion in regions in which PET images showed preserved glucose uptake was predicted to be reversible, whereas abnormal motion in regions with depressed glucose uptake was predicted to be irreversible. According to these criteria, abnormal contraction in 35 of 41 segments was correctly predicted to be reversible (85 percent predictive accuracy), and abnormal contraction in 4 of 26 regions was correctly predicted to be irreversible (92 percent predictive accuracy). In contrast, electrocardiograms showing pathological Q waves in the region of asynergy predicted irreversibility in only 43 percent of regions. We conclude that PET imaging with 13NH3 to assess blood flow and 18FDG to assess the metabolic viability of the myocardium is an accurate method of predicting potential reversibility of wall-motion abnormalities after surgical revascularization.

Effect of beta blockade with betaxolol on left ventricular systolic function in chronic stable angina pectoris and left ventricular dysfunction

To assess the effect of beta blockade on left ventricular (LV) performance in patients with LV dysfunction and stable angina pectoris, 18 subjects taking a placebo followed by incremental doses of the cardioselective beta-adrenergic blocking agent betaxolol (5, 10, 20, 40 and 80 mg/day) were studied. The study ended with the achievement of optimal clinical beta blockade (heart rate at rest 50 to 60 beats/min, a 20% or smaller increase in heart rate during stage 1 of symptom-limited treadmill exercise using the modified Bruce protocol). Optimal clinical beta blockade produced a decrease in mean frequency of angina, from 6.8 +/- 1.7 to 0.7 +/- 0.8 episodes per week (p less than 0.0005) and an increase in mean treadmill exercise capacity, from 3.1 +/- 1.7 to 7.7 +/- 2.8 minutes (p less than 0.0005). LV systolic function was assessed at rest and during symptom-limited exercise with radionuclide left ventriculography. Mean LV ejection fraction (EF) during therapy with placebo was 39 +/- 7% at rest and 40 +/- 8% at peak exercise. Mean LVEF during optimal clinical beta blockade was 43 +/- 11% at rest and 45 +/- 10% at peak exercise. Neither of these changes was statistically significant. No patient had clinical or radiographic signs of LV failure. The results suggest that optimal clinical beta blockade with betaxolol, in doses sufficient to significantly reduce the frequency of angina and improve exercise capacity in patients with stable angina pectoris and mild to moderate LV systolic dysfunction, does not cause significant deterioration of LV systolic function or produce LV failure.

Prospective, randomised, double-blind study of radionuclide determination of left-ventricular ejection fraction in acute myocardial infarction

In a controlled, randomised, double-blind study to see whether knowledge of left-ventricular ejection fraction (LVEF) could reduce the frequency of left-sided heart failure after acute myocardial infarction, LVEF was determined a few days before hospital discharge in a consecutive series of 60 patients. Subsequently, the patients were randomly assigned to two groups. The cardiologist responsible for their treatment was aware of the LVEF result in group I but not in group II. A month after hospital discharge there was no significant difference in the LVEF between the groups. 2 months after discharge there were no significant differences between the groups in clinical and radiological signs of left-ventricular heart failure or the use of drugs. The cardiologist's clinical estimate of the LVEF and the result of the radionuclide determination were significantly correlated. Thus, the use of LVEF did not change the clinical outcome. The need for randomised controlled studies in the evaluation of diagnostic methods is emphasised.

Treatment of angina pectoris with nifedipine and atenolol: efficacy and effect on cardiac function

The antianginal effects of nifedipine 20 mg three times a day and atenolol 100 mg once a day singly and in combination were investigated in 16 patients with angina pectoris. The amount of work that could be done before angina and ST depression appeared was significantly increased by atenolol and the combination but not by nifedipine. At peak exercise the number of leads on a 16 point precordial electrocardiogram map that demonstrated greater than or equal to 1 mm ST segment depression was significantly reduced from a mean (SD) of 5.0 (0.4) on placebo to 3.7 (0.6), 2.8 (0.4), and 2.3 (0.7) on nifedipine, atenolol, and the combination respectively. Mean resting left ventricular ejection fraction, assessed by gated radionuclide ventriculography, did not change during any active treatment phase but increased significantly during exercise only on nifedipine and the combination. The nifedipine/atenolol combination was the most effective treatment, and the data suggest that nifedipine may be used to best advantage in combination with a beta blocker.

Effect of beta blockade on silent regional left ventricular wall motion abnormalities

The effect of beta-adrenergic blockade on regional left ventricular wall motion abnormalities was studied in 11 patients with coronary artery disease and silent myocardial ischemia during exercise testing. Four patients were asymptomatic; 7 were asymptomatic after a myocardial infarction. Left ventricular wall motion abnormalities were characterized by reduced regional ejection fraction (EF) during exercise determined by gated left anterior oblique images of the cardiac blood pool. In the 11 patients, 10 anteroseptal and 8 inferoposterior regions were subserved by stenotic coronary arteries. Before beta blockade, regional EF decreased in 15 of 18 regions. After beta blockade, this occurred in only 6 of 18 regions (p less than 0.05); the other 12 regions showed no change or an actual increase in regional EF. Thus, beta-adrenergic blockade effectively improved the reduction in exercise regional EF usually seen in patients with coronary artery disease with silent myocardial ischemia. One probable mechanism of action is a reduction in myocardial oxygen requirement at peak exercise.

Calcium antagonists and beta blockers in the control of mild to moderate systemic hypertension, with particular reference to verapamil and propranolol

The antianginal and antiarrhythmic role of calcium antagonists is well established. Recent preliminary studies have indicated that, like beta blockers, calcium antagonists may produce short- and long-term hypotensive effects in patients with mild to moderate essential hypertension. The pharmacologic properties of calcium antagonists provide a clear rationale for their use in the control of essential hypertension. The comparative hypotensive effects of verapamil (80 to 160 mg 3 times a day) and propranolol (40 to 120 mg 3 times a day) were evaluated over 4 weeks, preceded by a 4-week placebo phase, in a double-blind protocol in 17 patients with mild to moderate hypertension. Verapamil (n = 10) reduced the mean sitting systolic blood pressure by 10.7% (p less than 0.01) and standing by 7.6% (p less than 0.04). The corresponding data for propranolol (n = 7) were 4.8% (not significant) and 5% (p = 0.04). Verapamil reduced the sitting diastolic blood pressure by 10.8% (p less than 0.01), propranolol by 7.5% (p = 0.01); the standing diastolic blood pressure was reduced by 10.7% with verapamil (p less than 0.01) and by 8.6% (p = 0.01) with propranolol. With verapamil the mean heart rate fell from 77.60 +/- 8.42 to 70.20 +/- 4.85 beats/min (p = 0.03); with propranolol it fell from 76.85 +/- 6.91 to 66.29 +/- 4.54 beats/min (p less than 0.01). Although a trend towards a slightly greater hypotensive effect was apparent with verapamil compared with propranolol, the difference was not statistically significant. It is concluded that verapamil and propranolol exert comparable hypotensive potency in patients with mild to moderate hypertension.

Effects of esmolol on cardiac function: evaluation by noninvasive techniques

In a double-blind, randomized, crossover study, the effects of esmolol and propranolol were examined at rest and during peak upright exercise in 15 patients. At rest, both esmolol and propranolol significantly decreased heart rate, systolic blood pressure, rate-pressure product, left ventricular ejection fraction, cardiac index and right ventricular ejection fraction. During exercise, significant decreases were also found in heart rate, systolic blood pressure and cardiac index in both treatment groups. No significant differences were found between mean esmolol and mean propranolol measurements at rest and during exercise, except for the exercise systolic blood pressure, which was lower during esmolol infusion. Blood levels of esmolol decreased markedly by 30 minutes postinfusion, as did its beta-blocking action. Esmolol was well tolerated with no important local, systemic or laboratory abnormalities. Thus, the effects of esmolol on cardiovascular performance at rest and during exercise are similar to those of propranolol.

Beta-adrenoceptor blockade and intrinsic sympathomimetic activity--relevance in the treatment of ischaemic heart disease

Beta adrenoceptor blockade has become one of the major therapeutic interventions in the medical management of ischaemic heart disease over the last 15 years. A number of beta adrenoceptor blockers have been developed with differing pharmacological properties including cardioselectivity and intrinsic sympathomimetic activity (ISA). The relevance of this latter property has been in some doubt. A number of reports suggest that ISA confers haemodynamic benefits although there does not appear to be any clear therapeutic advantage. In addition it would appear that patients with severe or rest angina might benefit more from a pure beta antagonist rather than one with ISA when the beta blocker is used as monotherapy, but this situation rarely arises. This paper reviews and assesses the value of treatment of ischaemic heart disease with beta blockers possessing intrinsic sympathomimetic activity.

Does left ventricular aneurysmectomy improve ventricular function in patients undergoing coronary bypass surgery?

Fourteen consecutive patients undergoing left ventricular aneurysmectomy and coronary artery bypass grafting were studied by multiple gated ventricular scintigraphy at rest and during exercise before and at six weeks and six months after surgery. All had congestive heart failure and 12 angina pectoris. Before operation left ventricular ejection fraction fell significantly with exercise, as did the regional wall motion score. Six weeks after surgery all surviving patients were free of angina, with an improvement in functional class; the total exercise workload improved significantly, but resting left ventricular ejection fraction was unchanged; the regional wall motion score improved in both the anterior and left anterior oblique projections, although extensive areas of abnormal contraction persisted. Exercise left ventricular ejection fraction improved significantly after operation at six weeks, and previous exercise induced abnormalities of regional contraction were abolished. Six months after operation angina pectoris had recurred in one patient, but there was no further change in ventricular function in the remainder. Although resting ejection fraction is not improved, symptoms, exercise workload, and exercise ventricular function can be improved by aneurysmectomy and coronary artery bypass grafting, but the respective contribution of these two procedures remains uncertain.

Limitations of radionuclide ventriculography in the non-invasive diagnosis of coronary artery disease. A correlation with right heart haemodynamic values during exercise

A consecutive series of 56 patients with chest pain but no evidence of previous myocardial infarction was prospectively studied by radionuclide ventriculography to determine the value of global and regional radionuclide indices in detecting coronary artery disease. The results were correlated with the clinical judgment of chest pain, the results of the exercise electrocardiogram, and the right heart haemodynamic measurements during exercise. As a result of the criteria for entry, the study group was representative of the population seen in such a clinical setting. Only 25% of patients had coronary artery disease. The predictive power of radionuclide ventriculography was limited. The conventionally used criterion that normal subjects have an increase in left ventricular ejection fraction of at least 5% with exercise provided only 78% sensitivity and 57% specificity. Fourier analysis and visual interpretation of radionuclide studies wrongly diagnosed three out of 10 patients with extensive disease requiring surgery. These results suggest that radionuclide ventriculography is of limited value in the non-invasive diagnosis of coronary artery disease.

The role of beta blockade, with and without intrinsic sympathomimetic activity, in preserving compromised left ventricular function in patients with ischemic heart disease

To determine if intrinsic sympathomimetic activity (ISA) is associated with a hemodynamic advantage over non-ISA beta blockade, 17 patients with ischemic heart disease underwent resting echocardiography and symptom-limited stress radionuclide angiography on three occasions: control, pindolol (with ISA), 10 mg twice a day, and propranolol, 40 mg four times a day, in a nonrandomized design. In six patients with normal resting ejection fraction (EF) (mean = 57 +/- 4%), neither drug was associated with a significant hemodynamic improvement over control. In 11 patients with reduced resting EF (mean = 37 +/- 9%), pindolol was associated with a higher EF and peak velocity of circumferential fiber shortening at rest compared with propranolol but not control. On maximal exertion, pindolol was associated with a higher EF than that during control but was similar to propranolol. These observed beneficial effects on pindolol appear primarily to be related to the partial beta agonist activity which this agent possesses.

Effects of intravenous infusion of esmolol and propranolol on biventricular performance at rest and during exercise as assessed by quantitative radionuclide angiography

This double-blind, randomized, crossover study examined the effects of intravenous infusion of esmolol (a new ultra-short-acting beta-receptor blocking agent) and propranolol on cardiovascular performance at rest and during peak upright exercise in 15 patients. Biventricular function was assessed by means of first-pass radionuclide ventriculography with a computerized multicrystal camera. At rest, significant treatment differences between esmolol and propranolol vs baseline were found for the heart rate, systolic blood pressure, double product, left ventricular ejection fraction (EF), systolic blood pressure to end-systolic volume ratio, cardiac index and right ventricular EF. During exercise, significant treatment differences were also found for the heart rate, systolic blood pressure, double product, right ventricular EF and cardiac index. The mean baseline measurements were higher than the mean treatment measurements, but no significant differences were found between mean esmolol and mean propranolol measurements at rest and during exercise except for the exercise systolic blood pressure, which was lower during esmolol infusion. The magnitude of drug effect was greater at the time of exercise than at rest. The blood level of esmolol decreased markedly by 30 minutes after infusion. Esmolol was well tolerated, with no important local, systemic or laboratory abnormalities. Thus, the effects of esmolol on cardiovascular performance at rest and exercise are similar to those of propranolol.

Exercise training during chronic beta blockade in cardiovascular disease

To determine whether cardioselective and nonselective beta-blocking agents impair exercise training effects in patients with cardiovascular disease, 50 subjects were evaluated. All were in a 3-times-weekly medically supervised outpatient exercise program for 3 months or longer. Treadmill exercise tests were done initially and at 3-month intervals. Eight patients were receiving atenolol, 23 propranolol, 3 timolol, 6 metoprolol, and 8 nadolol and 1 patient receiving timolol changed to atenolol and 1 receiving nadolol changed to propranolol. Treadmill test duration increased significantly (p less than 0.05), from 7.5 +/- 2.5 to 9.9 +/- 2.3 minutes, with exercise training. In 35 of the 50 subjects heart rate at rest decreased significantly (p less than 0.05) from 67.5 +/- 11.7 to 60.4 +/- 10.5 beats/min. The other 15 subjects were excluded from heart rate analysis because beta blockade was begun 1 to 2 weeks after the initial exercise test. It is concluded that exercise training effects (increase in exercise test duration and decrease in resting heart rate) can be achieved in patients with cardiovascular disease in the presence of both cardioselective and nonselective beta-blocking agents.

Beta blockade in the compensation for bed-rest cardiovascular deconditioning: physiologic and pharmacologic observations

Beta-adrenergic blockade using intravenous propranolol was evaluated as a countermeasure for bedrest-induced cardiovascular deconditioning. After propranolol administration, tolerance to a maximal lower body negative pressure (LBNP) test after bed rest improved to at least the -70 mm Hg level; following this, there was a sharp decrease in tolerance time. Propranolol decreased mean tolerance time by 36% (17.7 +/- 2.4 to 11.5 +/- 2.3 minutes) before bed rest, and by only half as much (16.6%) after bed rest (14.4 +/- 2.2 to 12.0 +/- 2.3 minutes). Systemic vascular resistance was maintained and even slightly increased after propranolol despite a decrease in cardiac output, indicating beta 2-adrenergic blockade. Heart rates at all levels of LBNP were lower during beta blockade, yet increases occurred with successive LBNP steps, both before and after bed rest, indicating withdrawal of parasympathetic nervous system influences. Results support the use of propranolol in small dosages as a countermeasure after bed rest, and the findings may also be extrapolated to space-flight deconditioning.

Improvement in resting ventricular performance following coronary bypass surgery

To assess the changes in resting left ventricular (LV) function following coronary bypass surgery, technetium 99m-labeled multiple equilibrated blood pool gated scans were performed in 53 consecutive patients at rest, before operation, and at 24 hours and 1 week after operation. Left ventricular ejection fraction (LVEF) and end-diastolic volume (EDV) were measured. The LVEF increased significantly from a preoperative value of 49 +/- 2% to 56 +/- 2% at 24 hours after operation (p less than 0.05) and 56 +/- 2% at 1 week following operation (p less than 0.05 compared with the preoperative value). The EDV also exhibited significant changes, decreasing from a preoperative value of 148 +/- 8 ml to 91 +/- 11 ml at 24 hours (p less than 0.001) and 114 +/- 9 ml at 1 week (p less than 0.01 compared with the preoperative value). When the patients were divided into two groups according to the preoperative LVEF (Group 1, LVEF of greater than or equal to 50%; Group 2, LVEF of less than 50%), the observed changes were similar. This study demonstrates significant improvement in resting LV function 24 hours following coronary bypass surgery. This improvement persists at 1 week and is not related to the degree of preoperative impairment. We conclude that the combination of successful revascularization and optimal myocardial protection can result in significant improvement of LV function at rest.

Exercise and beta-blocking agents

Beta-adrenoceptor-blocking agents produce noticeable effects on exercise performance. In patients with coronary heart disease, exercise capacity may in some cases increase during beta-blockade. Training effects (increased functional capacity, increased maximal oxygen uptake) may be somewhat attenuated in relatively healthy individuals taking beta-blockers, although with vigorous exercise programs, physiologic adaptations to exercise probably do occur.

Evaluation of bepridil for the treatment of angina pectoris: evidence for preservation of left ventricular function

The efficacy of bepridil (400 mg once a day) was assessed in 15 patients with exertional angina pectoris. All 15 patients reported substantial clinical improvement during bepridil treatment compared with placebo treatment. Episodes of angina were 11.8 +/- 4.1 (mean +/- standard error of the mean)/week with placebo and 3.8 +/- 1.6 with bepridil (p less than 0.05); nitroglycerin use was 9.1 +/- 3.3 tablets/week with placebo and 3.5 +/- 1.7 with bepridil (p less than 0.05). Five of 15 patients receiving bepridil did not experience angina during treadmill exercise; in the remaining 10 patients, time to onset of angina during exercise was 5.7 +/- 0.9 minutes with bepridil as opposed to 4.5 +/- 0.8 minutes with placebo (p less than 0.05). Left ventricular (LV) performance at peak exercise as measured by first-pass radionuclide angiography revealed the ejection fraction to be 38 +/- 3% during placebo therapy and 47 +/- 4% during bepridil therapy (p less than 0.0025). End-diastolic LV volume was unchanged, but end-systolic volume was 136 +/- 11 and 117 +/- 13 ml (p less than 0.05) and stroke volume was 82 +/- 6 and 97 +/- 9 ml (p less than 0.05) during placebo and bepridil therapy, respectively. Heart rate at peak exercise was 136 +/- 3 beats/min with placebo and 128 +/- 3 beats/min with bepridil; however, blood pressure was unchanged. These studies demonstrate that bepridil results in significant clinical improvement and enhanced LV performance in patients with angina pectoris.

The effect of left ventricular systolic function on maximal aerobic exercise capacity in asymptomatic patients with coronary artery disease

The purpose of this study was to examine the relationship between maximal O2 uptake (VO2max) and left ventricular systolic function in patients with coronary artery disease. We studied 27 patients, age 50 +/- 10 years (mean +/- SD), who were asymptomatic and able to attain true VO2max. VO2max was defined by the leveling-off criterion and/or a respiratory exchange ratio of 1.15 or greater. Left ventricular ejection fraction was determined by gated cardiac blood pool imaging. In patients whose ejection fraction decreased with exercise, VO2max was 21 +/- 4 vs 27 +/- 4 ml/kg/min in those whose ejection fraction increased (p less than .001). Systolic blood pressure/end-systolic volume relation was shifted upward and to the right in the former group in response to peak exercise. In contrast, the pressure-volume relation was shifted upward and to the left in patients whose ejection fraction increased with exercise. Ejection fraction at rest did not correlate with VO2max. There was a significant but weak correlation between peak exercise ejection fraction and VO2max (r = .43, p less than .025). Left ventricular exercise reserve, i.e., the change in ejection fraction from rest to exercise, correlated with VO2max (r = .77, p less than .0002), maximal O2 pulse (r = .50, p less than .005), and maximal heart rate during treadmill exercise (r = .61, p less than .001). Maximal heart rate during treadmill exercise correlated with VO2max (r = .70, p less than .0002).(ABSTRACT TRUNCATED AT 250 WORDS)

Limitations of quantitative phase analysis of radionuclide angiograms for detecting coronary artery disease in patients with impaired left ventricular function

Phase analysis of radionuclide ventriculograms is used for identifying ischemic wall motion abnormalities. Myocardial segments with an abnormal phase, that is, delayed onset of wall motion, can be localized on a phase distribution image, and the synchronicity of left ventricular (LV) wall motion can be assessed from a histogram of LV phase distribution. The standard deviation of the LV peak on this histogram (SDP-LV) describes the width of the peak and is used as an index of the synchronicity of wall motion. We examined in this study the sensitivity of SDP-LV for identifying coronary artery disease (CAD) and its specificity in patients with normal and various degrees of LV impairment. A total of 84 patients were studied. Forty-five patients had CAD and 39 had congestive cardiomyopathy or valvular heart disease. Patients were grouped according to their LV ejection fraction (EF). In group I (37 patients) resting LVEF was equal to or greater than 50%, in group II (24 patients) it ranged from 35% to 50%, and in group III (23 patients) it was less than 25%. SDP-LV was highly specific in groups I and II for CAD with sensitivities of 48% and 89% at rest that increased with exercise to 88% and 100%. In group III patients, SDP-LV remained highly sensitive but was no longer specific for CAD. Therefore, in severe LV impairment, phase analysis does not aid in distinguishing CAD from other causes of ventricular dysfunction. By contrast, phase analysis is highly sensitive and specific for CAD in patients with normal or moderately depressed LV function.

Comparative effects of oral acebutolol and propranolol at rest and during exercise in ischemic heart disease: double-blind placebo crossover study utilizing radionuclide ventriculography

Acebutolol is a new investigational beta-antagonist which has intrinsic sympathomimetic and cardioselective properties. In this study its effects on the ischemic consequences following supine bicycle exercise were compared to those of propranolol in 16 patients with chronic stable coronary artery disease (CAD) using a double-blind placebo crossover protocol and equilibrium radionuclide ventriculography. In eight patients (group I), the left ventricular ejection fraction (LVEF) at peak exercise fell under control conditions. During chronic acebutolol therapy (400 mg thrice daily), the exercise-induced LVEF (means +/- 1 SD) was significantly higher (37.1 +/- 15.5% versus 42.2 +/- 14.3%; p less than 0.05). The corresponding values during placebo and during propranolol (80 mg thrice daily) were 39.2 +/- 12.3% versus 43.4 +/- 14.8% (p = 0.07). In eight patients (group II) in whom supine bicycle exercise produced increases in LVEF, both acebutolol (58.8 +/- 5.4% versus 53.8 +/- 4.4%) and propranolol (57.8 +/- 5.7% versus 54.1 +/- 4.9%) attenuated the increases. In neither group was the resting LVEF reduced by acebutolol or propranolol. The data show that acebutolol and propranolol are approximately equipotent in minimizing the radionuclide left ventriculographic manifestations of myocardial ischemia induced by supine bicycle exercise.