Prognostic implications of a normal dobutamine-atropine stress echocardiogram in patients with chest pain

A clinical and echocardiographic score for assigning risk of major events after dobutamine echocardiograms

OBJECTIVES

We sought to develop and validate a risk score combining both clinical and dobutamine echocardiographic (DbE) features in 4890 patients who underwent DbE at three expert laboratories and were followed for death or myocardial infarction for up to five years.

BACKGROUND

In contrast to exercise scores, no score exists to combine clinical, stress, and echocardiographic findings with DbE.

METHODS

Dobutamine echocardiography was performed for evaluation of known or suspected coronary artery disease in 3156 patients at two sites in the U.S. After exclusion of patients with incomplete follow-up, 1456 DbEs were randomly selected to develop a multivariate model for prediction of events. After simplification of each model for clinical use, the models were internally validated in the remaining DbE patients in the same series and externally validated in 1733 patients in an independent series.

RESULTS

The following score was derived from regression models in the modeling group (160 events): DbE risk = (age.0.02) + (heart failure + rate-pressure product <15000).0.4 + (ischemia + scar).0.6. The presence of each variable was scored as 1 and its absence scored as 0, except for age (continuous variable). Using cutoff values of 1.2 and 2.6, patients were classified into groups with five-year event-free survivals >95%, 75% to 95%, and <75%. Application of the score in the internal validation group (265 events) gave equivalent results, as did its application in the external validation group (494 events, C index = 0.72).

CONCLUSIONS

A risk score based on clinical and echocardiographic data may be used to quantify the risk of events in patients undergoing DbE.

Correlates of subclinical left ventricular dysfunction in ESRD

BACKGROUND

Abnormalities of the left ventricle are common in patients with end-stage renal disease (ESRD) both before and after the start of renal replacement therapy. The purpose of this study is to identify possible causes of subclinical left ventricular (LV) dysfunction in patients with ESRD. In particular, we sought to determine whether the presence of ESRD was itself associated with dysfunction independent of LV hypertrophy and coronary artery disease.

METHODS

Assessment of cardiovascular risk factors and dialysis adequacy was completed in 145 unselected patients with ESRD who were recruited from the renal dialysis unit and compared with age- and sex-matched controls. Among the 68 patients with ESRD who had undergone a dobutamine stress echocardiogram with normal findings, regional cardiac function was quantified by myocardial Doppler velocity, LV volumes and mass were measured using three-dimensional echocardiography, and vascular function was assessed using brachial artery reactivity (BAR).

RESULTS

LV diastolic velocity was impaired in patients with ESRD, but there was no significant difference in systolic velocity compared with control patients of similar age. Age, diabetes mellitus, hypertension, and LV mass were independent predictors of diastolic velocity (model R2 = 0.45; P < 0.001), whereas age and risk factor number were predictors of systolic velocity (model R2 = 0.19; P = 0.002). Increasing risk factor number had no significant relationship with LV mass or volume. There was no detected association between BAR and incremental risk factors (P = 0.51).

CONCLUSION

Subclinical LV dysfunction occurs in patients with ESRD, but is evidenced as abnormal myocardial diastolic, rather than systolic, function. Correlates of abnormal function are age, diabetes mellitus, hypertension, and LV mass, rather than ESRD alone, dialysis adequacy, or abnormal endothelial function.

Effect of tissue Doppler on the accuracy of novice and expert interpreters of dobutamine echocardiography

The subjective interpretation of dobutamine echocardiography (DBE) makes the accuracy of this technique dependent on the experience of the observer, and also poses problems of concordance between observers. Myocardial tissue Doppler velocity (MDV) may offer a quantitative technique for identification of coronary artery disease, but it is unclear whether this parameter could improve the results of less expert readers and in segments with low interobserver concordance. The aim of this study was to find whether MDV improved the accuracy of wall motion scoring in novice readers, experienced echocardiographers, and experts in stress echocardiography, and to identify the optimal means of integrating these tissue Doppler data in 77 patients who underwent DBE and angiography. New or worsening abnormalities were identified as ischemia and abnormalities seen at rest as scarring. Segmental MDV was measured independently and previously derived cutoffs were applied to categorize segments as normal or abnormal. Five strategies were used to combine MDV and wall motion score, and the results of each reader using each strategy were compared with quantitative coronary angiography. The accuracy of wall motion scoring by novice (68 +/- 3%) and experienced echocardiographers (71 +/- 3%) was less than experts in stress echocardiography (88 +/- 3%, p <0.001). Various strategies for integration with MDV significantly improved the accuracy of wall motion scoring by novices from 75 +/- 2% to 77 +/- 5% (p <0.01). Among the experienced group, accuracy improved from 74 +/- 2% to 77 +/- 5% (p <0.05), but in the experts, no improvement was seen from their baseline accuracy. Integration with MDV also improved discordance related to the basal segments. Thus, use of MDV in all segments or MDV in all segments with wall motion scoring in the apex offers an improvement in sensitivity and accuracy with minimal compromise in specificity.

Echocardiography, nuclear scintigraphy, and stress testing in the emergency department evaluation of acute coronary syndrome

There are between 3 and 5 million visits to EDs each year for complaints of chest pain. Of these, about one half of the patients have a noncardiac cause for their chest pain. Of the remainder, about 30% to 50% have significant coronary disease. It is quite clear that patients who are at high risk for a coronary event should be admitted to the hospital. For the low-to-moderate risk patients, the decision to admit or discharge the patient from the ED is not quite so easy. The emergency physician has to decide which tests can be helpful in the decision-making process, this can be undertaken in conjunction with a consultative cardiologist. It can be argued that if a patient does not have a normal test result whichever that evaluatory test is), then the patient should be admitted for further work-up and evaluation. The easiest test to perform in the ED setting is an echocardiogram. The images can be sent by telecommunication to a qualified echocardiogram reader for interpretation. This also has a reasonable NPV, although not necessarily as good as some of the other modalities available, unless interpreted in light of cardiac enzyme test results. If the index of suspicion is still high, then a stress echocardiogram can be considered. This has an excellent NPV and can be easily performed in [table: see text] most patients. This should not be undertaken in the face of an evolving MI, and patients should be observed for at least 8 hours after their initial presentation to the ED prior to undergoing a provocative test. Nuclear scintigraphy, another modality available for cardiac risk stratification, can be a logistical nightmare. The nuclear isotopes are strictly regulated by the Nuclear Regulatory Commission. The emergency physician may inject the isotopes, provided that he or she has undergone the necessary radiation training. Also, the patient must be removed from the ED to a radioisotope-approved area for the duration of the scan. One of the most difficult questions left open after review of all these analytical modalities is the duration of time these test results remain valid; when does an individual patient need to be reevaluated as to their specific pretest probability? The answer to this question lies in the presenting clinical scenario. If the patient presents with a similar inciting trigger for his or her symptoms, and the cardiac risk profile has not changed appreciably, then the previous study (whether a provocative stress test or even a cardiac catheterization) probably can be reliably counted. If the patient's risk profile has changed or the symptoms are new or more intense, the physician is compelled to pursue this encounter as a new, acute event. This can be true even in the setting of a previous cardiac catheterization that showed nonobstructive coronary disease, because plaque rupture can be acute and unpredictable. Ultimately, optimal care calls for each institution to develop a specific approach, in conjunction with their consultative cardiologist or critical care specialist, to enhance patient care, safety, and diagnostic outcome, while maintaining cost efficiency.

Pharmacologic stress echocardiography. Dobutamine and arbutamine stress testing

Pharmacologic stress testing is an important noninvasive method for evaluating patients with known or suspected coronary artery disease who are unable to adequately exercise. Pharmacologic stress echocardiography using dobutamine has been developed over the last 10 to 15 years as an alternative to vasodilator stress testing using nuclear perfusion imaging. As experience has grown, digital subtraction echocardiogram has been shown to be a safe, convenient, and reliable method for stress testing in a variety of patient populations. Digital subtraction echocardiogram has comparable sensitivity, specificity, and accuracy when compared to other stress testing methods which employ cardiac imaging and is superior to the exercise echocardiogram. It has certain advantages over nuclear perfusion imaging in terms of cost and convenience. The recent addition of arbutamine echocardiography (which has been shown to be comparable to digital subtraction echocardiogram) provides another alternative method for pharmacologic stress testing. Continued improvement in echocardiographic image quality and the development of new technologies such as tissue harmonic imaging and contrast echocardiography will hopefully improve the echocardiographic evaluation of wall motion therefore increasing the diagnostic accuracy of echocardiographic stress testing.