Stress echocardiography for the assessment of myocardial ischemia and viability

Exercise echocardiography in rheumatoid arthritis: a case-control study

BACKGROUND

Rheumatoid arthritis (RA) is associated with increased cardiovascular risk.

METHODS

To assess the role of exercise echocardiography (EE) in the evaluation of patients with RA, follow-up (mean, 6.7+/-3.7 years) was retrospectively obtained in 159 patients with RA who underwent EE. Patients were matched for age, gender, and cardiovascular risk factors with 454 controls who underwent EE.

RESULTS

Patients with RA were more likely to have positive results for ischemia on EE (odds ratio, 2.32; 95% confidence interval, 1.48-3.64; P=.0003). Rest and exercise wall motion score indexes were higher in the RA group (1.14+/-0.33 and 1.22+/-0.39, respectively, vs 1.06+/-0.18 and 1.10+/-0.24 in controls; P < .005 for each). Logistic regression adjusted for age revealed an increased odds ratio for myocardial ischemia of 1.06 (95% confidence interval, 1.02-1.11; P=.005) per year of RA. Five-year all-cause mortality in subjects with RA with myocardial ischemia on EE was 14.9%, compared with 4.3% in RA subjects without ischemia (P=.028).

CONCLUSION

RA was associated with a 2-fold increased risk for myocardial ischemia on EE; risk increased with the duration of RA. Mortality was increased in patients with RA with ischemia on EE.

Evaluation of myocardial viability with contrast echocardiography

Identification of viable myocardium after acute myocardial infarction (MI) or in the setting of severe chronic ischemic heart disease has important clinical implications. Myocardial contrast echocardiography (MCE) has been used for the evaluation of myocardial viability by assessing myocardial perfusion and microvascular integrity. In acute MI, MCE can identify the no-reflow phenomenon after revascularization, which has significant implications regarding recovery of function and clinical outcomes. Serial changes in myocardial perfusion can also be evaluated for the prediction of ultimate recovery of function. In the setting of chronic ischemic left ventricular dysfunction, early studies have shown that MCE is helpful in the identification of myocardial hibernation and in the prediction of recovery of function after revascularization, with accuracy similar to radionuclide techniques. Preliminary studies using the new quantitative MCE parameters of myocardial blood flow and velocity derived from intravenous contrast administration appear to enhance the diagnostic accuracy of MCE in the evaluation of myocardial viability.

Myocardial hibernation in coronary artery disease

Coronary artery disease (CAD) is very prevalent in Western societies and is a leading cause of mortality and morbidity. Despite decreases in mortality rates from CAD over the past 30 years, ischemic heart failure remains an important problem because people with CAD are now living longer. Hibernating myocardium may be defined as reversible left ventricular dysfunction due to chronic CAD that shows improvement in function after revascularization. Many patients with ischemic cardiomyopathy have areas of hibernating myocardium, and thus can potentially show improvement in left ventricular regional and global function if they are revascularized. Whether hibernating myocardium represents an adaptive response to hypoperfusion in the face of chronic ischemia or whether it is a degenerative process is not entirely clear. Clearly, ultrastructural changes of de-differentiation are seen, and include loss of sarcomeres and the appearance of small mitochondria and glycogen accumulation. Although the mechanisms underlying the changes in morphology and depressed contractility, and the factors governing recovery of function are not clear, changes in adrenergic receptor density, cytokine upregulation, and the degree of fibrosis may all play a role. Identification of viability is commonly performed with dobutamine echocardiography or nuclear imaging. Because patients with extensive CAD and poor left ventricular systolic function are high-risk candidates for coronary bypass surgery, the preoperative identification of viability provides important prognostic information. Patients with viable myocardium who are treated with revascularization rather than medical therapy have better outcomes in terms of survival, left ventricular function, symptoms, and exercise capacity.

Use of atropine to maintain higher heart rate after exercise during treadmill stress echocardiography

The sensitivity of treadmill stress echocardiography (SE), which is extensively used as a noninvasive test to detect myocardial ischemia, is contingent on the rapid acquisition of 2-dimensional echocardiographic (2D) images immediately after exercise, before a substantial decrease in heart rate (HR). This test is technically challenging and needs proficient sonographers to obtain the images rapidly. This study was designed to determine whether administration of atropine at peak exercise would maintain a higher HR longer after exercise, thereby facilitating acquisition of images. Two comparable groups of patients were randomized to receive either 0.5 mg atropine intravenously (i.v.) (n = 20), or no medication (n = 19) at peak exercise. HR was significantly higher in the atropine group compared with the control group (P <.05) at 60, 90, and 120 seconds after exercise. There were no serious complications in either group. Atropine can be safely used to maintain a higher HR after exercise during SE, thus reducing the technical challenge of obtaining postexercise 2D images while HR remains elevated.

Assessment of myocardial viability with stress echocardiography

Over the past two decades, there has been an increased realization that systolic myocardial dysfunction, outside of the setting of acute ischemia, does not necessarily imply irreversible myocardial injury. Echocardiographic techniques, particularly dobutamine stress echocardiography, have emerged as important diagnostic modalities that can identify residual viable myocardium in patients following acute myocardial infarction and in those with suspected myocardial hibernation. Dobutamine echocardiography can also help risk stratify patients with coronary artery disease and depressed ventricular function and identify patients who would benefit best from revascularization procedures.

Long-term prognostic value of exercise echocardiography compared with exercise 201Tl, ECG, and clinical variables in patients evaluated for coronary artery disease

BACKGROUND

The accuracy of exercise echocardiography and 201Tl single photon emission computed tomography (SPECT) is similar in the diagnosis of coronary artery disease (CAD). However, comparative data on long-term prognosis are lacking.

METHODS AND RESULTS

Clinical variables and exercise, echocardiographic, and 201Tl tomographic parameters were studied in 248 patients (age, 56+/-12 years [mean+/-SD]; 189 men) who underwent simultaneous treadmill exercise 201Tl SPECT and echocardiography. Follow-up was obtained in 225 patients (91%) at a mean of 3.7+/-2.0 years. A total of 64 cardiac events occurred. With the use of stepwise logistic regression, 4 models simulating clinical stress testing scenarios were evaluated in the prediction of all cardiac events, ischemic events, and/or cardiac death. The best clinical models were exercise echocardiography with exercise ECG and exercise 201Tl SPECT with exercise ECG. Both models were comparable in the prediction of cardiac events. For the exercise echocardiography model, exercise wall motion score index and induction of ischemia were the strongest predictors of events with ORs of 2.63 per unit increment (95% CI, 1. 34 to 5.17; P=0.005) and 4.1 (95% CI, 1.32 to 12.79; P=0.015), respectively. For the model with exercise 201Tl SPECT, the strongest predictor was ischemic perfusion defect (OR, 4.93; 95% CI, 1.72 to 14.08; P=0.003). The absence of ST changes during exercise decreased the risk of events. For the prediction of ischemic events and/or cardiac death, echocardiographic and 201Tl parameters were the only predictive variables.

CONCLUSIONS

In patients evaluated for CAD, exercise echocardiography and 201Tl combined with ECG variables provide comparable prognostic information and can be used interchangeably for risk stratification.

Native tissue harmonic imaging improves endocardial border definition and visualization of cardiac structures

BACKGROUND

The purpose of this study was to examine the impact of native tissue harmonic imaging on endocardial border definition, wall motion scoring, and visualization of intracardiac structures.

METHODS AND RESULTS

For wall motion analysis, 60 consecutive patients underwent standard transthoracic echocardiograms in both harmonic and fundamental modes. Three experienced echocardiographers reviewed each echocardiogram. Endocardial border definition for each wall segment was graded from 1 to 4 (1 = excellent endocardial definition). Wall motion was scored by using a standard 16-segment model and 1 to 5 scale. For visualization of cardiac structures, 50 consecutive patients were studied. Two experienced interpreters reviewed each echocardiogram for both normal and abnormal structures by using the following scoring scale: (1) harmonic is much better than fundamental, (2) harmonic is slightly better than fundamental, (3) harmonic and fundamental are equivalent, (4) fundamental is slightly better than harmonic, and (5) fundamental is much better than harmonic. Visualization of 64% (95% confidence interval [CI] 0.61 to 0.66) of all segments improved in harmonic mode, with 26% (95% CI 0.24 to 0.29) improving from poor/not seen to good/excellent. Of 444 segments deemed poor/not seen, visualization of 312 (70%) (95% CI 0.66 to 0.75) improved to good/excellent with harmonic mode. Of these 312 segments, 55% comprised the lateral and anterior walls on apical views. Interobserver agreement on endocardial border definition was 82% to 86%. Scoring of wall motion was altered in 171 of 1075 (16%) of segments by harmonic mode. This was significantly greater than the interobserver disagreement, which was only 10% (p<0.002). Mitral valve chordae and papillary muscles were visualized slightly/much better with harmonic mode in 40 of 50 echocardiograms. Left atrial boundaries were seen slightly/much better in harmonic mode in 29 of 50 studies. Abnormal structures were seen slightly/much better in harmonic mode in 12 of 14 cases.

CONCLUSIONS

Native tissue harmonic imaging has significant impact on endocardial border definition and wall motion scoring and improves the visualization of both normal and abnormal cardiac structures.

Hibernating myocardium has reduced blood flow at rest that increases with low-dose dobutamine

The study of Sun and coworkers is important because (1) it provides additional data that HM has an inotropic and an attenuated coronary vasodilator reserve. They also provided data that support the conclusion that with dobutamine, the improvement of abnormal LV wall motion is real in many patients. (2) It emphasizes the possibility of a deleterious effect (infarction) of dobutamine in HM and thus the need for appropriate caution during its use. (3) It provides additional data that confirm that areas of perfusion-metabolism mismatch on PET imaging (HM) are associated with a reduced MBF at rest. However, their conclusions about areas of LV dysfunction with "normal" MBF in coronary artery disease are problematic; therefore, one must be extremely cautious about these conclusions on the basis of the data that are presented.