Methodological Analysis of Diagnostic Dobutamine Stress Echocardiography Studies

Use of Computed Tomography Coronary Calcium Score for Coronary Artery Disease Risk Stratification During Liver Transplant Evaluation

Background

End-stage liver disease (ESLD) is not considered a risk factor for atherosclerotic cardiovascular disease (ASCVD). However, lifestyle characteristics commonly associated with increased ASCVD risk are highly prevalent in ESLD. Emerging literature shows a high burden of asymptomatic coronary artery disease (CAD) in patients with ESLD and a high ASCVD risk in liver transplantation (LT) recipients. Coronary artery calcium score (CAC) is a noninvasive test providing reliable CAD risk stratification. We implemented an LT evaluation protocol with CAC playing a central role in triaging and determining the need for further CAD assessment. Here, we inform our results from this early experience.

Methods

Patients with ESLD referred for LT evaluation were prospectively studied. We compared accuracy of CAC against that of CAD risk factors/scores, troponin I, dobutamine stress echocardiogram (DSE), and single-photon emission computed tomography (SPECT) to detect coronary stenosis ≥70 (CAD ≥ 70) per left heart catheterization (LHC). Thirty-day post-LT cardiac outcomes were also analyzed.

Results

One hundred twenty-four of 148 (84%) patients underwent CAC, 106 (72%) DSE/SPECT, and 50 (34%) LHC. CAC ≥ 400 was found in 35 (28%), 100 to 399 in 17 (14%), and <100 in 72 (58%). LHC identified CAD ≥ 70% in 8 of 29 (28%), 2 of 9 (22%), and 0 of 4, respectively. Two acute coronary syndromes occurred after LT in a patient with CAC 811 (CAD < 70%), and one with CAC 347 (CAD ≥ 70%). No patients with CAC < 100 presented with acute coronary syndrome after LT. When using CAD ≥ 70% as primary endpoint of LT evaluation, CAC ≥ 346 was the only test showing predictive usefulness (negative predictive value 100%).

Conclusions

CAC is a promising tool to guide CAD risk stratification and need for LHC during LT evaluation. Patients with a CAC < 100 can safely undergo LT without the need for LHC or cardiac stress testing, whereas a CAC < 346 accurately rules out significant CAD stenosis (≥70%) on LHC, outperforming other CAD risk-stratification strategies.

Chronotropic incompetence on dobutamine stress echocardiography in candidates for a liver transplant

OBJECTIVES

We evaluated dobutamine stress echocardiography as an initial screening test for a cardiac evaluation before a liver transplant.

MATERIALS AND METHODS

We retrospectively examined 111 liver transplant candidates who had undergone previous cardiac evaluation; 30 of whom had undergone a liver transplant.

RESULTS

Eighty patients (72.1%) completed a dobutamine stress echocardiography (41 chronotropically competent, 39 incompetent), while 31 patients (27.9%) required us to terminate early. Overall, 68 patients (61%) were on β-blockers (21 required early dobutamine stress echocardiography termination, 30 chronotropically incompetent, and 17 competent). Patient results were normal. Thirty patients underwent a liver transplant. Among candidates requiring termination of early dobutamine stress echocardiography, posttransplant cardiac events included 1 fatal acute myocardial infarction, 1 nonfatal acute myocardial infarction, and 1 idiopathic cardiomyopathy. Among chronotropically incompetent patients, 2 patients had transient bradycardia, and among those who were chronotropically competent, 1 had refractory atrial fibrillation, and 1 had transient bradycardia.

CONCLUSIONS

Nearly 50% of patients with end-stage liver disease may not reach the target heart rate. Early termination of dobutamine stress echocardiography because of cardiac symptoms or significant echocardiographic changes have more effect in predicting postoperative cardiac events, but further evaluation is required even if their target heart rate is close to that desired. Lower target heart rate may be acceptable in chronotropically incompetent individuals provided they are asymptomatic, have no echocardiographic changes, or cardiovascular risk factors, especially if they are on β-blockers.

Assessment of myocardial ischemia with cardiovascular magnetic resonance

Assessment of myocardial ischemia in symptomatic patients remains a common and challenging clinical situation faced by physicians. Risk stratification by presence of ischemia provides important utility for both prognostic assessment and management. Unfortunately, current noninvasive modalities possess numerous limitations and have limited prognostic capacity. More recently, ischemia assessment by cardiovascular magnetic resonance (CMR) has been shown to be a safe, available, and potentially cost-effective alternative with both high diagnostic and prognostic accuracy. Cardiovascular magnetic resonance has numerous advantages over other noninvasive methods, including high temporal and spatial resolution, relatively few contraindications, and absence of ionizing radiation. Furthermore, studies assessing the clinical utility and cost effectiveness of CMR in the short-term setting for patients without evidence of an acute myocardial infarction have also demonstrated favorable results. This review will cover techniques of ischemia assessment with CMR by both stress-induced wall motion abnormalities as well as myocardial perfusion imaging. The diagnostic and prognostic performance studies will also be reviewed, and the use of CMR for ischemia assessment will be compared with other commonly used noninvasive modalities.

Factors affecting sensitivity and specificity of diagnostic testing: dobutamine stress echocardiography

BACKGROUND

Clinical characteristics of patients, angiographic referral bias, and several technical factors may all affect the reported diagnostic accuracy of tests. The aim of this study was to assess their influence on the diagnostic accuracy of dobutamine stress echocardiography (DSE).

METHODS

The medical literature from 1991 to 2006 was searched for diagnostic studies using DSE and meta-analysis was applied to the 62 studies thus retrieved, including 6881 patients. These studies were analyzed for patient characteristics, angiographic referral bias, and several technical factors.

RESULTS

The sensitivity of DSE was significantly related to the inclusion of patients with prior myocardial infarctions (0.834 vs 0.740, P < .01) and defining the results of DSE as already positive in case of resting wall motion abnormalities rather than obligatory myocardial ischemia (0.786 vs 0.864, P < .01). Specificity tended to be lower when patients with resting wall motion abnormalities were included in a study (0.812 vs 0.877, P < .10). The presence of referral bias adversely affected the specificity of DSE (0.771 vs 0.842, P < .01).

CONCLUSION

This analysis suggests that the reported sensitivity of DSE is likely higher and the specificity lower than expected in routine clinical practice because of the inappropriate inclusion of patients with prior myocardial infarctions, the definition of positive results on DSE, and the negative influence of referral bias. However, in the patient subset that will be sent to coronary angiography, the opposite results can be expected.

Predictive value of dobutamine stress echocardiography for coronary artery disease detection in liver transplant candidates

Patients with obstructive coronary artery disease (CAD) undergoing orthotopic liver transplantation (OLT) are at increased risk of poor outcomes. The accuracy of dobutamine stress echocardiography (DSE) to detect obstructive CAD is not well established in this population. We retrospectively identified patients with end-stage liver disease who underwent both DSE and coronary angiography as part of risk stratification prior to OLT. One hundred and five patients had both DSE and angiography, of whom 14 had known CAD and 27 failed to reach target heart rate during DSE. Among the remaining 64 patients (45 men; average age 61 +/- 8 years) DSE had a low sensitivity (13%), high specificity (85%), low positive predictive value (PPV) (22%) and intermediate negative predictive value (NPV) (75%) for obstructive CAD. DSE as a screening test for obstructive CAD in OLT candidates has a poor sensitivity. The frequent chronotropic incompetence and low sensitivity in patients who achieve target heart rate, even in those with multiple cardiovascular disease risk factors, suggest that alternative or additional methods of risk stratification are necessary.

Automated Analysis of Myocardial Deformation at Dobutamine Stress Echocardiography

OBJECTIVES

We investigated the accuracy of automated analysis of myocardial deformation during dobutamine stress echocardiography (DSE).

BACKGROUND

The time required for segmental measurement of strain rate imaging (SRI) limits its feasibility for quantification of DSE.

METHODS

Myocardial deformation was assessed at DSE in 197 patients, 76 with and 61 without coronary artery disease (CAD) at angiography, and 60 at low risk of CAD. Automated deformation analysis was based on velocity gradient and segment length methods of measuring longitudinal motion within a region of interest tracked through the cardiac cycle. Results were compared with independent wall motion scoring (WMS). Patients were randomly divided; group A (n = 69) established optimal cutoffs for the parameters and group B (n = 68) tested their accuracy.

RESULTS

The feasibility of WMS exceeded that of both SRI methods at rest and at peak stress. In group A, the area under the receiver-operating characteristics curve of the peak systolic strain rate was 0.90 by both methods, and the optimal cutoffs for detection of CAD were -1.3 (velocity gradient) and -1.2 s(-1) (segment length). The areas under the receiver-operating characteristics curves for end-systolic strain were less (0.87) by both methods, with respective cutoffs of 9% and 8%. In group B, the velocity and segment length methods had respective sensitivities of 87% and 84% for SR, and 87% and 88% for end-systolic strain. Both significantly exceeded that of WMS in the same group (75%).

CONCLUSIONS

Automated analysis of myocardial deformation at DSE is feasible and accurate, and may increase the sensitivity of expert conventional reading.

Dobutamine cardiovascular magnetic resonance: A review

Dobutamine cardiovascular magnetic resonance (DCMR) is useful for identifying myocardial ischemia and viability in patients with known or suspected coronary artery disease (CAD). This article reviews the performance and utility of DCMR, its association with dobutamine stress echocardiography (DSE), and areas of active investigative research.

Dobutamine stress echocardiography in healthy adult male rats

BACKGROUND

Dobutamine stress echocardiography is used to investigate a wide variety of heart diseases in humans. Dobutamine stress echocardiography has also been used in animal models of heart disease despite the facts that the normal response of healthy rat hearts to this type of pharmacological stress testing is unknown. This study was performed to assess this normal response.

METHODS

15 normal adult male Wistar rats were evaluated. Increasing doses of dobutamine were infused intravenously under continuous imaging of the heart by a 12 MHz ultrasound probe.

RESULTS

Dobutamine stress echocardiography reduced gradually LV diastolic and systolic dimensions. Ejection fraction increased by a mean of +24% vs. baseline. Heart rate increased progressively without reaching a plateau. Changes in LV dimensions and ejection fraction reached a plateau after a mean of 4 minutes at a constant infusion rate.

CONCLUSION

DSE can be easily performed in rats. The normal response is an increase in heart rate and ejection fraction and a decrease in LV dimensions. A plateau in echocardiographic measurements is obtained after 4 minutes of a constant infusion rate in most animals.