Justifying echocardiography: the role of outcomes research in evaluating a diagnostic test

Effect of performing preoperative echocardiography in patients with cardiovascular risk on intraoperative anesthetic management and postoperative outcomes: A retrospective study

Although echocardiography is widely used for preoperative cardiac risk evaluation, few studies have analyzed the effect of performing preoperative echocardiography on intraoperative anesthetic management and postoperative outcomes. We investigated the effect of performing echocardiography on intraoperative anesthetic management and postoperative outcomes in patients with cardiovascular risk. We retrospectively evaluated patients who had undergone major abdominal surgery and satisfied 2 or more of the following criteria: hypertension, diabetes mellitus, age ≥70 years, and previous cardiac disease. Patients were categorized into a group in which preoperative echocardiography was performed (echo) and a group in which it was not (non-echo). The primary outcomes were postoperative 30-day mortality and incidence of cardiovascular complications. Secondary outcomes were length of hospital stay, intraoperative incidence of hypotension, use of vasopressors, and findings on intraoperative invasive hemodynamic monitoring. There were no differences in 30-day mortality, incidence of postoperative cardiovascular complications, length of hospital stay, and intraoperative events between the groups. Only the incidence of cardiac output monitoring was lower in the echo group than in the non-echo group (59.6% vs 73.9%). Preoperative echocardiography does not affect postoperative outcomes, but it has the potential to affect intraoperative anesthetic management such as invasive hemodynamic monitoring during surgery.

Echocardiographic predictors of morbidity and mortality in patients with advanced heart failure: the Beta-blocker Evaluation of Survival Trial (BEST)

OBJECTIVES

The aim of this study was to determine echocardiographic predictors of outcome in patients with advanced heart failure (HF) due to severe left ventricular (LV) systolic dysfunction in the Beta-blocker Evaluation of Survival Trial (BEST).

BACKGROUND

Previous studies indicate that echocardiographic measurements of LV size and function, mitral deceleration time, and mitral regurgitation (MR) predict adverse outcomes in HF. However, complete quantitative echocardiograms evaluating all of these parameters have not been reported in a prospective randomized clinical trial in the era of modern HF therapy.

METHODS

Complete echocardiograms were performed in 336 patients at 26 sites and analyzed by a core laboratory. A Cox proportional-hazards regression model was used to determine which echocardiographic variables predicted the primary end point of death or the secondary end point of death, HF hospitalization, or transplant. Significant variables were then entered into a multivariable model adjusted for clinical and demographic covariates.

RESULTS

On multivariable analysis adjusted for clinical covariates, only LV end-diastolic volume index predicted death (events = 75), with a cut point of 120 ml/m(2). Three echocardiographic variables predicted the combined end point of death (events = 75), HF hospitalization (events = 97), and transplant (events = 9): LV end-diastolic volume index, mitral deceleration time, and the vena contracta width of MR. Optimal cut points for these variables were 120 ml/m(2), 150 ms, and 0.4 cm, respectively.

CONCLUSIONS

Echocardiographic predictors of outcome in advanced HF include LV end-diastolic volume index, mitral deceleration time, and vena contracta width. These variables indicate that LV remodeling, increased LV stiffness, and MR are independent predictors of outcome in patients with advanced HF.

Time requirements of the standard echocardiogram: implications regarding limited studies

BACKGROUND

Although no formal detailed definitions exist, a standard echocardiogram should easily be differentiated from a limited examination by its comprehensive nature and time requirement.

OBJECTIVE

We evaluated the time required to perform each specific component of a comprehensive echocardiography examination and applied these data to compare the time required to complete 3 limited imaging protocols.

METHODS

In all, 7 experienced sonographers were timed in their performance of a comprehensive echocardiographic examination on a healthy patient. A total of 3 limited imaging protocols were then constructed to evaluate for pericardial effusion, wall motion, and left ventricle size. The time necessary to complete each protocol was calculated by adding the average time required to perform all of its components and was compared with the comprehensive examination.

RESULTS

The imaging time required to complete a standard study was 26 +/- 5.4 minutes (range: 20-32). The percentage of total study time spent on 2-dimensional imaging, M-mode, color Doppler, and spectral components was 31 +/- 2.9%, 11 +/- 3.6%, 17 +/- 2.9%, and 39 +/- 5.0%, respectively. The calculated time needed to perform a limited protocol was less than 5 minutes, resulting in a greater than 80% reduction in time compared with the standard examination.

CONCLUSION

Time analysis of components of the standard echocardiography examination can be used to construct appropriate, time-efficient, limited, cardiac ultrasound imaging examinations and differentiate limited from comprehensive studies.

What is the real clinical utility of echocardiography? A prospective observational study

This was a prospective, structured interview to evaluate physician expectations of echocardiography and the subsequent impact on patient care. The setting involved requests for echocardiograms in patients admitted to a tertiary care teaching hospital. Measurements included assessment of the diagnostic and therapeutic implications of echocardiography perceived by the physicians and subsequently reported and confirmed by blinded chart review. From January to May 1997, 542 echocardiograms were performed on 500 inpatients (age 62 +/- 17 years; 56% men). Referring physicians were mainly house staff (83%) and from medical services. The main indications were evaluation of left ventricular function (54%) or valve function (16%). At the time of the request, 89% of physicians believed that echocardiography was needed to guide future investigations or treatment, although in 24% of cases, physicians could not provide details of such. A reported change in treatment occurred in 57% and was validated by chart review in 38%. Changes occurred more frequently in patients in the intensive care unit versus those not in the intensive care unit (54% vs 37%, P =.02) but were similar between attending physicians and house staff (frequency of change 41% vs 39%, P = not significant) and between those with and those without previous echocardiograms (38% vs 39%, P = not significant). The utility of the echocardiogram to influence treatment decisions in hospitalized patients is high, especially in critically ill patients. However, this impact is less than is anticipated at the time of the initial request. Further studies involving more select populations of patients are required.

Changing Patterns of Transesophageal Echocardiography Use in the Intensive Care Unit

Since its advent, the use of transesophageal echocardiography (TEE) has grown rapidly. In patients undergoing TEE in the intensive care unit over two time periods (4 years apart), we evaluated whether TEE led to new/unsuspected findings or changes in patient management. Results showed that the indications for which patients underwent TEE changed considerably between the two time periods. Hemodynamic instability was an indication for TEE in 41% of the patients in the first interval and 56% of the patients in the second interval. TEE frequently established a new diagnosis (41%) and led to significant management changes (28%) in both time periods. These changes occurred despite the use of a pulmonary artery catheter in nearly 2/3 of the patients studied. Therefore, despite increasing and changing use, TEE frequently establishes unsuspected diagnosis and directly influences patient management when used in intensive care patients.

Use of echocardiography in the management of congestive heart failure in the community

OBJECTIVES

We evaluated the use and the impact of echocardiography in patients receiving an initial diagnosis of congestive heart failure in Olmsted County, Minnesota, in 1991.

BACKGROUND

The American College of Cardiology/American Heart Association clinical practice guidelines recommend echocardiography in all patients with suspected congestive heart failure. No data are available on use and impact of echocardiography in management of congestive heart failure in a community.

METHODS

The medical records linkage system of the Rochester Epidemiology Project was used to identify all 216 patients who satisfied the Framingham criteria for congestive heart failure. Of these, 137 (63%) underwent echocardiography within 3 weeks before or after the episode of congestive heart failure (Echo group), and the other 79 patients constitute the No-Echo group.

RESULTS

The No-Echo group patients were older (p=0.022), were more likely to be female (p=0.072), had milder symptoms (p=0.001) and were less often hospitalized at diagnosis (p=0.001). Fewer patients in the No-Echo group were treated with angiotensin-converting enzyme inhibitors (p=0.001). Advanced age (> or = 80 years), lower New York Heart Association functional class, absence of a fourth heart sound on examination, absence of cardiomegaly or signs of congestive heart failure on chest radiography and absence of known valve disease were independently related to the decision not to obtain an echocardiogram. Survival after adjustment for age, functional class and gender was lower in the No-Echo group than the Echo group (risk ratio=0.607, p=0.017).

CONCLUSIONS

The underuse of echocardiography appears to be associated with poorer survival and underuse of angiotensin-converting enzyme inhibitor therapy.

Feasibility of "limited" echo imaging: characterization of incidental findings

To evaluate the feasibility of limiting the extent of the echocardiographic examination without omitting significant incidental findings, we reviewed consecutive reports from full echo studies performed in a tertiary medical center with the following referral questions: "rule-out pericardial effusion" (n = 40) and "rule-out source of embolus" (n = 132). Specific limited echo imaging protocols were formulated without unnecessary imaging (that is, unrelated to the diagnostic question) or use of Doppler. The percentage of full echo studies with significant incidental findings was determined, categorized by patient age, and then recalculated by whether the specific limited imaging protocol could potentially detect any or all of the incidental findings. The percentage of cases with significant incidental findings was 45% and 36% in the "rule-out" pericardial effusion and source of embolus groups, respectively. This percentage was dependent on age <65 years versus > or =65 years (22% vs 42%, p < 0.005). Limited imaging protocols could identify > or =85% of cases with significant incidental findings. These data suggest that limited echo imaging may be feasible in certain patient groups and referral diagnoses.

Applying principles of pharmacoeconomic evaluation to perflenapent emulsion, a new echocardiographic contrast agent for use in cardiac function testing

A pharmacoeconomic evaluation was performed to determine the cost-effectiveness of perflenapent emulsion, a new contrast agent for use in echocardiography. A decision tree analysis was performed on data from the charts of 108 patients who had undergone stress echocardiography without contrast enhancement as part of a cardiac function or wall-motion study. An analysis of a theoretical cohort of patients was conducted to determine shifts in cost associated with enhancement of stress echocardiography with perflenapent emulsion. Outcome was determined by the point at which the clinician was able to determine a treatment course for the patient based on the diagnostic information given. Stress echocardiography without contrast was identified as the most cost-effective path in terms of a conclusive test. Perflenapent emulsion shows a positive cost impact in patients who have had an inconclusive stress echocardiogram without the use of a contrast agent. These results are supported by a sensitivity analysis across a wide range of pricing for perflenapent emulsion, a wide range of cost for a stress echocardiogram, and up to 99% efficacy of contrast-enhanced stress echocardiography.