Patterns of exercise response in patients with severe left ventricular dysfunction: radionuclide ejection fraction and hemodynamic cardiac performance evaluations

Is magnetic resonance imaging the 'reference standard' for cardiac functional assessment? Factors influencing measurement of left ventricular mass and volumes

PURPOSE

MRI is considered reference standard for the assessment of left ventricular (LV) volume and mass measurements. There are few accepted guidelines for uniform assessment of cardiac function with MRI. We sought to investigate different confounding factors influencing LV measurement results.

MATERIAL AND METHODS

In 60 diabetic type-II patients (group A) we compared intra-/inter-reader variability of MRI for cardiac function measured twice at a 3 month interval by one MRI trained reader and one untrained. In 20 patients (group B) two different techniques were compared for determining the epicardial and endocardial LV-borders.

RESULTS

Bland Altman analysis showed excellent intra-observer measurement agreement for the trained reader 1 for EDM (mean = -2.3 (-23.6-19)), EDV (2.9(-9.2-15.0)), ESV (3.3(-5.8-12.4)) and EF (1.2(-3.3-5.7)). Untrained reader 2 measurement agreement was considerably less appropriate for EDM (mean = -8.2 (-25.8-9.5)), EDV (7.8(-5.1-20.7)), ESV (5.3(-8.0-18.6)). Only for EF (0.8 (-6.5-8.1)) results were comparable to reader 1. Inter-observer measurement in the beginning was poor for EDM (-13.5(-55.6-28.6)) and EDV (7.3(-61.9-76.6)), whereas agreement for ESV (2.1(-29.9-34.2)) and EF (-0.9(-11.6-9.9)) was good. After 3 months, measurement agreement for EDM (-5.3 (-46.4-35.8)) was considerably improved, for EDV (0.4(-67.0-66.2)) was excellent, whereas agreement for ESV (3.1(-34.4-28.1)) and EF (-1.7(-13.0-9.6)) was similar. Using different techniques for determining the epicardial and endocardial borders, only end-diastolic volume was unchanged whereas all other parameters were significantly different using the two methods (p < or = 0.03).

CONCLUSION

Intra- and inter-reader variability, analyst experience as well as different techniques for determining the boundaries of the left ventricle significantly affect MRI parameters for cardiac function. These results suggest a need for developing commonly accepted standards for cardiac MRI evaluation.

Head-to-head comparison of high-dose dobutamine stress-echocardiography and exercise testing in prognostic stratification of patients with idiopathic dilated cardiomyopathy

INTRODUCTION It is of the utmost importance to make an accurate assessment of prognosis in patients with idiopathic dilated cardiomyopathy. Both high-dose dobutamine stress-echocardiography and exercise testing have been used for prognostic stratification of these patients. OBJECTIVE To make head-to-head comparison of high-dose dobutamine stress-echocardiography and exercise testing in prognostic stratification of patients with idiopathic dilated cardiomyopathy. METHODS A total of 63 consecutive patients (55 men, mean age 50.1 ?9.6 years, mean ejection fraction 19.2?8.4%) with idiopathic dilated cardiomyopathy, left ventricular end-diastolic diameter >60mm, ejection fraction <35%, and adequate echo-cardiographic window have been studied. Dobutamine stress echocardiography was performed using 5, 10, 20, 30 and 40 meg/kg/min infusions, in progressive stages lasting 5 minutes each. Wall motion score index and ejection fraction were considered the indices of the left ventricular contractility. Contractile reserve was defined as the difference between the values of these indices obtained at peak dobutamine dose during the test and the baseline values. Exercise testing was performed as supine bicycle ergometry in progressive stages of 25 W lasting 120 seconds each. Patients were followed one year for combined end-point consisting of cardiac death, partial left ventric-ulectomy and hospitalization for congestive heart failure. RESULTS Out of 61, 19 (31%) patients met combined end-point during follow-up [cardiac death in 6/61 (10%), partial left ventricu-lectomy in 4/61 (7%) and hospitalization for heart failure in 9/61 (15%) patients]. Kaplan-Meier survival analysis demonstrated that dobutamine-induced change of wall motion score index was the best parameter for separation of patients in terms of prognosis during the follow-up (log rank=25.34, p<0.001), followed by change of ejection fraction (log rank=16.83, p<0.001) and duration of exercise testing (log rank 13.85, p=0.002). Cox model identified dobutamine-induced change of wall motion score index as the only independent predictor (p<0.001) of combined end-point during one-year follow-up. DISCUSSION There is a number of studies dealing with the left ventricular contractile indices. These studies are different with respect to studied population, method used to elicit the left ventricular contractile response and the indices of contractile reserve. A number of studies has suggested that the amount of pharmacologically or physically induced change of wall motion score index and ejection fraction can identify patients with dismal prognosis. Peak oxygen consumption is traditionally considered the most accurate prognostic index, but its usefulness has been recently questioned. Our data suggest that high-dose dobutamine stress-echocardiography may be superior to exercise testing for prognostic stratification of patients with idiopathic dilated cardiomyopathy. The reasons for such observation are not clear, but it can be hypothesized that this may be due to multifactorial nature of the exercise tolerance. The most serious potential drawback of methodology is that, because of technical limitations, we did not test peak oxygen consumption in our patients, but since it has been shown that oxygen consumption correlates well with the duration of exercise, we believe that our methodology is valid. CONCLUSION Both high-dose dobutamine stress-echocardiography and exercise testing can identify patients with dismal prognosis during one-year follow-up, but it appears that dobutamine stress-echocardiography may yield better prognostic significance.

Comparison of left ventricular responses to the six-minute walk test, stair climbing, and maximal upright bicycle exercise in patients with congestive heart failure due to idiopathic dilated cardiomyopathy

Submaximal exercise tests have been advocated to assess exercise capacity in chronic heart failure, but hemodynamic responses have not been characterized. To determine left ventricular (LV) responses during submaximal exercise, the LV ejection fraction (EF) and volumes were evaluated by using an ambulatory radionuclide detector in 13 patients with idiopathic dilated cardiomyopathy during upright maximal graded bicycle exercise, stair climbing and a 6-minute walk test. The 3 tests elicited different responses in volumes and, to a lesser degree, in LVEF. The maximal bicycle exercise led to a decrease in LVEF from 22 +/- 9% to 17 +/- 8% (p <0.05), with marked increases in both end-diastolic volume (EDV) (+15 +/- 10%, p <0.001) and end-systolic volume (ESV) (+23 +/- 18%, p <0.001). Stair climbing tended to reduce LVEF (from 24 +/- 11% to 21 +/- 10%, p = 0.05), with a lesser increase in volumes, which was more marked for ESV (+8 +/- 9%, p <0.01) than for EDV (+4 +/- 4%, p <0.01). The 6-minute walk test did not significantly change LVEF (23 +/- 10% vs 22 +/- 10%), but increased both EDV (+10 +/- 6%, p <0.001) and ESV (+8 +/- 8%, p <0.01) moderately and proportionally. Exercise capacity indexes (peak oxygen consumption, maximal bicycle work rate, stair climbing time, and the distance covered during the 6-minute walk test) correlated significantly with one another. There was no correlation between submaximal exercise tolerance indexes and resting or exercise LVEF. This study shows that (1) LVEF changes are inadequate to report on LV volume changes during exercise; (2) the 3 tests induce different LV volume changes; (3) the 6-minute walk test induces significant changes in LV volumes but no change in LVEF.

Nuclear cardiology, current applications in clinical practice

The clinical applications of nuclear cardiology have rapidly expanded since the introduction of suitable imaging cameras and readily applicable isotopes. The currently available methods can provide useful data on estimates of ventricular function and detection of myocardial ischemia for adequate patient management. Two standard procedures are routinely used: (1) myocardial perfusion scintigraphy, eg, with thallium 201; and (2) radionuclide angiocardiography by using technetium 99m-labeled red blood cells. Myocardial perfusion scintigraphy provides information on regional viability and estimates regional myocardial perfusion by measuring regional tracer activity. Thallium 201 is the agent used for noninvasive assessment of myocardial perfusion and for improving the results of exercise electrocardiography. Alternative tests, such as pharmacologic stress testing with dipyridamole, have been proposed as a reliable substitute for exercise testing. Additional quantitative analysis and computed tomography have increased the sensitivity and specificity of thallium scintigraphy. Radionuclide angiography techniques are used for the noninvasive evaluation of cardiac function, right and left ventricular function, and wall motion abnormalities. As in perfusion scintigraphy, radionuclide angiography has proven its value for the detection of coronary artery disease (CAD). Abnormal regional wall motion abnormalities are specific for CAD.

Abnormal left ventricular ejection fraction response to mental stress and exercise in cardiomyopathy

BACKGROUND

A decline in left ventricular (LV) ejection fraction in response to mental stress and exercise is regarded as an indicator of myocardial ischemia. In patients with LV dysfunction, the ejection fraction is sensitive to afterload, which increases during stress. Thus, the effects of mental stress and exercise on LV systolic function in patients with cardiomyopathy were examined.

METHODS

The ambulatory nuclear VEST (Capintec, Inc., Ramsey, N.J.) was used to monitor LV ejection fraction in patients with cardiomyopathy (10 idiopathic and 9 ischemic). Patients underwent a series of mental stress tests (serial 7s, Stroop color, and Paced auditory addition) and treadmill exercise. Heart rate, systolic blood pressure, and LV ejection fraction were measured.

RESULTS

Mental stress and exercise increased heart rate and systolic blood pressure. For idiopathic cardiomyopathy, LV ejection fraction decreased during serial 7s, Stroop color, Paced auditory addition and exercise by -8% +/- 6%, -7% +/- 5%, -7% +/- 3%, -9% +/- 10%, respectively. For ischemic cardiomyopathy, LV ejection fraction declined by -4% +/- 3%, -7% +/- 5%, -6% +/- 3%, -2% +/- 6% during the same stress tests. There was no difference between the idiopathic and ischemic groups. Each patient showed a 5% or greater decline in LV ejection fraction during one mental stress test. There was an inverse relation between changes in LV ejection fraction and systolic blood pressure during all mental stress tests and exercise (r = -0.47, p < 0.0001).

CONCLUSIONS

In patients with depressed baseline systolic function, the decline in systolic function during mental stress and exercise could be related in part to increases in LV afterload.

Left ventricular volumes during exercise in normal subjects and patients with dilated cardiomyopathy assessed by first-pass radionuclide angiography

During isotonic exercise, left ventricular (LV) suction and the Frank-Starling law of the heart may have important roles in the enhancement of early LV diastolic filling and in the increase of myocardial contractility, respectively. It remains controversial whether these mechanisms operate in normal subjects or patients with dilated cardiomyopathy. Ten healthy subjects and 10 patients with idiopathic dilated cardiomyopathy who underwent maximal upright bicycle exercise testing were studied. First-pass radionuclide angiography was performed at both rest and peak exercise using a multicrystal gamma camera. In normal subjects, LV end-systolic volume at peak exercise was smaller than during baseline (17 +/- 7 vs 30 +/- 15 ml/m2; p < 0.05), whereas rapid filling volume was greater (52 +/- 16 vs 38 +/- 8 ml/m2; p < 0.01). In patients with dilated cardiomyopathy, both end-systolic (108 +/- 34 to 123 +/- 53 ml/m2; p = NS) and rapid filling (24 +/- 6 to 28 +/- 9 ml/m2; p = NS) volumes did not change from rest to peak exercise. A significant correlation was found between the changes in end-systolic volume at peak exercise and in peak rapid filling rate in normal subjects (r = 0.6; p < 0.05), but not in patients with dilated cardiomyopathy (r = 0.3; p = NS). In normal subjects, end-diastolic volume at peak exercise was similar to that during baseline (78 +/- 14 and 85 +/- 15 ml/m2, respectively; p = NS), whereas in patients with dilated cardiomyopathy, it was greater (164 +/- 50 vs 146 +/- 33 ml/m2; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between left ventricular function at rest and with exercise and silent myocardial ischemia

The prognostic value of radionuclide measures of left ventricular function at rest and exercise is well established. Some studies have suggested that the frequency and duration of silent ischemia during ambulatory monitoring provide similar prognostic information; however, studies comparing these two techniques have not been performed. This study examines the relation between left ventricular function at rest and exercise-induced ischemia assessed by radionuclide ventriculography with myocardial ischemia during ambulatory electrocardiographic (ECG) monitoring. Of the 155 patients with coronary artery disease studied, 88% had left ventricular dysfunction with exercise, defined as failure of the ejection fraction to increase by greater than 4% with exercise, and 33% of patients had left ventricular dysfunction at rest (ejection fraction less than 45%); 52% had transient episodes of ST segment depression during 48-h ambulatory ECG monitoring. Exercise-induced left ventricular dysfunction during radionuclide ventriculography was extremely sensitive (94%) in detecting patients with ischemic episodes during ambulatory ECG monitoring; however, only 55% of patients with exercise-induced left ventricular dysfunction had ST segment depression during ambulatory monitoring. Moreover, patients with left ventricular dysfunction at rest had a lower prevalence of transient episodes of ST segment depression (31%) than did patients with normal left ventricular function at rest (62%) (p = 0.008). The relation between prognostically important variables during exercise radionuclide ventriculography and the number and duration of transient episodes of ST depression was examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Incremental prognostic value of exercise hemodynamic variables in chronic congestive heart failure secondary to coronary artery disease or to dilated cardiomyopathy

To determine the prognostic value of hemodynamic variables at rest and during exercise, 49 patients with chronic congestive heart failure undergoing hemodynamic evaluation at rest and during symptom-limited exercise were followed for 1 year. One-year mortality rate was 33%. On univariate analysis, nonsurvivors differed significantly from survivors in pulmonary arterial wedge pressure at rest (22 +/- 10 vs 15 +/- 10 mm Hg; p = 0.01) and during exercise (32 +/- 9 vs 24 +/- 9 mm Hg; p = 0.003), stroke work index at rest (19 +/- 6 vs 25 +/- 9 g-m/m2; p = 0.03) and during exercise (20 +/- 7 vs 32 +/- 14 g-m/m2; p = 0.001) and exercise-induced increment in stroke work index (0.5 +/- 0.4 vs 7 +/- 8 g-m/m2; p = 0.004), but not with respect to left ventricular ejection fraction, exercise duration, peak oxygen consumption or peak left ventricular hydraulic power. Patients with a peak exercise stroke work index less than 20 g-m/m2 had a 66% mortality rate compared with a mortality rate of 13% in patients with a peak exercise stroke work index greater than 20 g-m/m2 (p = 0.0001). Multiple logistic regression analysis identified pulmonary arterial wedge pressure at rest and peak exercise stroke work index as the only independent predictors of mortality. A receiver-operating characteristic curve analysis revealed that peak exercise stroke work index provided significant incremental prognostic information over the resting hemodynamic variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of radionuclide ventriculography in evaluating cardiac function

The role of nuclear cardiology techniques for evaluating cardiac function has become increasingly important among other diagnostic techniques. The current status of radionuclide imaging of left and right ventricular function allows accurate diagnosis of cardiac patients with both coronary and noncoronary disease. The combination of gated first-pass and equilibrium radionuclide ventriculography makes it possible to assess more completely cardiac function than by either technique alone. Of particular interest to most imaging physicians is the current position of exercise ventriculography in the diagnostic setting, especially since this test has undergone new scrutiny in its application to broader patient segments. This technique and issues related to its place in the diagnostic environment are discussed in this review article, with emphasis on relevance to the clinical laboratory.

Cardiovascular reserve in idiopathic dilated cardiomyopathy as determined by exercise response during cardiac catheterization

Simultaneous right- and left-sided cardiac high-fidelity hemodynamic measurements were obtained at rest and supine exercise during cardiac catheterization in 27 patients (mean age 32 +/- 10 years) with idiopathic dilated cardiomyopathy to investigate the hemodynamic exercise response and possible mechanisms for the wide variation in exercise tolerance observed clinically. There were no significant differences in other rest hemodynamic variables between group 1, patients with a normal exercise factor (more than 600, n = 10), and group 2, patients with an abnormal exercise factor (less than 600, n = 17). A greater increase in stoke volume index (12 +/- 6 vs 2 +/- 8 ml/beats/m2, mean +/- standard deviation) and a greater decrease in systemic vascular resistance with exercise occurred in group 1 than in group 2 (-614 +/- 304 vs -406 +/- 291 dynes cm-5). Elevation of right ventricular end-diastolic pressure with exercise was significantly greater in group 2 than in group 1 (7 +/- 5 vs 1 +/- 4 mm Hg, respectively, p less than 0.05). A maintained cardiac reserve in patients with idiopathic dilated cardiomyopathy appears to be largely dependent on 2 primary factors: preservation of normal right ventricular function during exercise; and preservation of systemic vasodilator capability sufficient to produce a significant degree of afterload reduction during exercise.

Cardiocirculatory adjustments to exercise following myocardial infarction in rats

The sequential changes of the cardiocirculatory response to exercise over time in rats with myocardial infarction and failure were studied. Hemodynamics and regional blood flow (RBF, radioactive microspheres) were determined at rest and during exercise either at 1, 10 or 42 days after infarction (MI, infarct size 41.4 +/- 2.6% of LV) or sham procedures (SH). Whereas the response to exercise was attenuated one day after surgery in MI and SH, cardiocirculatory recovery was present in SH at 10 days and LV systolic and end-diastolic pressures separated SH and MI groups. Renal vasoconstriction during exercise occurred 10 days after MI and BF to working muscle during exercise was significantly lower in MI as compared to SH. At 42 days after MI manifest heart failure was present and despite significant blood flow redistribution (p less than 0.05 MI vs SH in renal and cutaneous beds) impaired skeletal muscle flow was observed along with increased vascular resistance in working muscle during exercise. We conclude that the cardiocirculatory response to exercise following large MI follows a distinctive time-dependent pattern, which differs from that observed at rest. Besides exaggerated sympathetically mediated vasoconstriction during exercise, impaired vasodilatation in skeletal muscle at exercise emerged.

Left ventricular volume and ejection fraction response to exercise in chronic congestive heart failure: difference between dilated cardiomyopathy and previous myocardial infarction

To determine if cause influences the left ventricular (LV) volume and ejection fraction (EF) response to exercise, 24 patients with chronic congestive heart failure (CHF) (13 dilated cardiomyopathy [DC], CHF-DC group; 11 previous myocardial infarction [MI], CHF-MI group) and 6 age-matched control subjects underwent simultaneous hemodynamic monitoring and radionuclide ventriculography during semiupright bicycle exercise. Both CHF groups had similar hemodynamic values, LV volumes and EF at rest. Exercise hemodynamics were also similar, but LV volume and EF responses to exercise were different. In the CHF-DC group LV end-diastolic volume increased by 15% during exercise, significantly less (p less than 0.01) than the 44% increase in CHF-MI group. During exercise, EF increased in CHF-DC group, but did not change in CHF-MI group because of a larger increase in end-systolic volume. The slope of mean pulmonary wedge pressure-LV end-diastolic volume relation was steeper in CHF-DC group than in CHF-MI group (p less than 0.01). The study suggests that LV volume and EF response to exercise in patients with CHF depends on the origin of the CHF.