Stress echocardiography in contemporary clinical cardiology: practical considerations and accreditation

Stress echocardiography is a widely utilised test in patients with known or suspected coronary artery disease (CAD), valvular heart disease and cardiomyopathies. Its advantages include the ubiquitous availability of echocardiography, lack of ionising radiation, choice of physiological or pharmacological stressors, good diagnostic accuracy and robust supporting evidence base. SE has evolved significantly as a technique over the past three decades and has benefitted considerably from improvements in overall image quality (superior resolution), machine technology (e.g. digital cine-loop acquisition and side-by-side image display) and development of second-generation ultrasound contrast agents that have improved reader confidence and diagnostic accuracy. The purpose of this article is to review the breadth of SE in contemporary clinical cardiology and discuss the recently launched British Society of Echocardiography (BSE) Stress Echocardiography accreditation scheme.

Diagnostic Concordance and Clinical Outcomes in Patients Undergoing Fractional Flow Reserve and Stress Echocardiography for the Assessment of Coronary Stenosis of Intermediate Severity

BACKGROUND

The ischemic consequences of coronary artery stenosis can be assessed by invasive fractional flow reserve (FFR) or by noninvasive imaging. We sought to determine (1) the concordance between wall thickening assessment during clinically indicated stress echocardiography (SE) and FFR measurements and (2) the factors associated with hard events in these patients.

METHODS

Two hundred twenty-three consecutive patients who underwent SE and invasive FFR measurements in close succession were analyzed retrospectively for diagnostic concordance and clinical outcomes.

RESULTS

At the vessel level, the sensitivity, specificity, positive predictive value, and negative predictive value of SE for identifying significant disease as assessed by FFR was 68%, 75%, 43%, and 89%, respectively. The greatest discordance was seen in patients with wall thickening abnormalities (WTAs) and negative FFR. During a follow-up of 3.6 ± 2.2 years, there were 23 cardiovascular (CV) events (death and nonfatal myocardial infarction). The number of wall segments with inducible WTAs emerged as the strongest factor associated with CV events (hazard ratio, 1.18 [1.05-1.34]; P = .008). FFR was not associated with outcome. There was a significant increase in event rate in patients with WTA/negative FFR versus no WTA/negative FFR (P = .01), but no significant difference versus WTA/positive FFR (P = .85).

CONCLUSIONS

In a patient population with significant CV risk factors, a normal SE had a high negative predictive value for excluding abnormal FFR. WTAs were associated with outcomes regardless of FFR value, suggesting that this is a superior marker of ischemia to FFR.

Stress Echocardiography in Stable Coronary Artery Disease

PURPOSE OF REVIEW

Stress echocardiography (SE) is a well-established technique for the diagnosis and risk stratification of patients with known or suspected coronary artery disease (CAD). This review article summarizes the status of SE in CAD, including testing protocols, clinical efficacy and current use of newer technologies: myocardial perfusion, strain imaging, three-dimensional echocardiography and adjunctive carotid ultrasonography.

RECENT FINDINGS

Recent major findings in SE include the clinical value of myocardial perfusion imaging in multicentre studies, as well as when added to left ventricular (LV) wall motion assessment in clinical service. Additionally, SE has been shown to be more cost-effective than exercise ECG in patients with low-intermediate pre-test probability of CAD. Adjunctive atherosclerosis imaging by carotid ultrasonography (CU) to ischaemia testing by SE provides synergistic prognostic value, equivalent to hybrid imaging by PET-CT. Despite the development of newer and more expensive imaging modalities, SE remains the cornerstone for the assessment of CAD and has excellent clinical efficacy, is safe and is cost-effective.

Reproducible Computer-Assisted Quantification of Myocardial Perfusion with Contrast-Enhanced Ultrasound

Myocardial perfusion can be quantified by myocardial contrast echocardiography (MCE) and is used for the diagnosis of coronary artery disease (CAD). However, existing MCE quantification software is highly operator dependent and has poor reproducibility and ease of usage. The aim of this study was to develop robust and easy-to-use software that can perform MCE quantification accurately, reproducibly and rapidly. The developed software has the following features: (i) semi-automatic segmentation of the myocardium; (ii) automatic rejection of MCE data with poor image quality; (iii) automatic computation of perfusion parameters such as myocardial blood flow (MBF). MCE sequences of 18 individuals (9 normal, 9 with CAD) undergoing vasodilator stress with dipyridamole were analysed quantitatively using the software. When evaluated against coronary angiography, the software achieved a sensitivity of 71% and a specificity of 91% for hyperemic MBF. With the automatic rejection algorithm, the sensitivity and specificity further improved to 77% and 94%, respectively. For MBF reproducibility, the percentage agreement is 85% (κ = 0.65) for inter-observer variability and 88% (κ = 0.72) for intra-observer variability. The intra-class correlation coefficients are 0.94 (inter-observer) and 0.96 (intra-observer). The time taken to analyse one MCE sequence using the software is about 3 min on a PC. The software has exhibited good diagnostic performance and reproducibility for CAD detection and is rapid and user-friendly.

Incidental finding of a double orifice mitral valve in an elderly patient: value of 3D imaging

A rare isolated double orifice mitral valve (DOMV) was diagnosed in a 77-year-old male patient, being assessed for surgical repair of the ascending aorta. This is a rare congenital abnormality, usually discovered as an incidental finding during investigation of other congenital heart defects. This case shows that a detailed assessment of all cardiac structures is necessary, not only in young patients, but also in the elderly population, to minimise the under-diagnosis of such rare anomalies. The use of 3D transthoracic echocardiography (TTE) has an increasingly significant role in establishing the diagnosis and extending the morphological and functional understanding of the anomaly.