Comparison of myocardial contrast echocardiography with SPECT in the evaluation of coronary artery disease in asymptomatic patients with LBBB

Usefulness of dynamic perfusion SPECT with quantitative assessment of myocardial perfusion reserve for the detection of myocardial ischaemia in patients with presumed new left bundle branch block

Aims

The aim of this retrospective study was to evaluate the ability of dynamic SPECT with quantitative analysis of myocardial blood flow (MBF) and myocardial flow reserve (MFR) for the detection of coronary artery disease (CAD) in patients with presumed new left bundle branch block (LBBB).

Methods and results

We evaluated the dynamic SPECT results from 174 consecutive patients with LBBB without a history of CAD from a single center. MBF was assessed at rest and during regadenoson (400 μg). Normal MFR was defined as ≥ 2.1. Left ventricular function and segmental perfusion were assessed from conventional gated SPECT. SPECT abnormalities were found in 17/174 (10%) patients including a reversible SPECT defect in 4 patients (2.3%), a fixed defect in 12 patients (7%), and both in 1 patient. Global left ventricular function was normal despite a significant impairment of septal wall motion. Stress and rest MBF was decreased in the septum and the inferior wall compared with other walls (P < 0.0001), resulting in similar MFR. A reduced MFR was associated with a fixed defect (P = 0.04). Only 18 patients (10%) presented with a decreased MFR. They were more often referred to subsequent coronary angiography (8/18, 44%) compared with patients with a normal MFR (9/156, 6%, χ2 = 27.382, P < 0.0001). However, significant coronary lesions were finally found in only 4/174 patients (2%).

Conclusion

Although a decreased MFR was associated with a fixed defect on conventional perfusion imaging, the low rate of CAD finally demonstrated in this study questions the relevance of routine screening for CAD in patients with presumed new LBBB.

Clinical practice of contrast echocardiography: recommendation by the European Association of Cardiovascular Imaging (EACVI) 2017

Contrast echocardiography is widely used in cardiology. It is applied to improve image quality, reader confidence and reproducibility both for assessing left ventricular (LV) structure and function at rest and for assessing global and regional function in stress echocardiography. The use of contrast in echocardiography has now extended beyond cardiac structure and function assessment to evaluation of perfusion both of the myocardium and of the intracardiac structures. Safety of contrast agents have now been addressed in large patient population and these studies clearly established its excellent safety profile. This document, based on clinical trials, randomized and multicentre studies and published clinical experience, has established clear recommendations for the use of contrast in various clinical conditions with evidence-based protocols.

Non-invasive assessment of coronary artery disease in patients with left bundle branch block

There is a high prevalence of coronary artery disease (CAD) in patients with left bundle branch block (LBBB); however there are many other causes for this electrocardiographic abnormality. Non-invasive assessment of these patients remains difficult, and all commonly used modalities exhibit several drawbacks. This often leads to these patients undergoing invasive coronary angiography which may not have been necessary. In this review, we examine the uses and limitations of commonly performed non-invasive tests for diagnosis of CAD in patients with LBBB.

Magnetic resonance imaging of abnormal ventricular septal motion in heart diseases: a pictorial review

The purpose of this article is to illustrate the usefulness of MR imaging in the clinical evaluation of congenital and acquired cardiac diseases characterised by ventricular septal wall motion abnormality. Recognition of the features of abnormal ventricular septal motion in MR images is important to evaluate the haemodynamic status in patients with congenital and acquired heart diseases in routine clinical practice.

Suitable solutions for reconstituting the ultrasound contrast agent "Levovist" used in contrast echocardiogram: in vitro and in vivo evaluation of the influence of osmotic pressure

PURPOSE

To evaluate the influence of the osmotic pressure of solutions used for reconstituting the ultrasound contrast agent "Levovist" on the degree of video intensity of the enhancement and video intensity decay in contrast echocardiogram, we used 6 solutions with different osmotic pressures in both vitro and in vivo experiments.

MATERIALS AND METHODS

In the in vitro experiments, Levovist was reconstituted with 6 kinds of solutions with different osmotic pressures (Lactate Ringer's solution, 2.5%, 5%, 7.5%, and 20% glucose and distilled water) and peak video intensities and video intensity decay were measured. In the in vivo experiments, contrast echocardiography was performed in 7 adult volunteers, following the intravenous injections of Levovist, previously reconstituted with one of 2 solutions (5% glucose or distilled water).

RESULTS

In vitro, at peak time, Levovist reconstituted with either Lactate Ringer's solution, 2.5% glucose, 5% glucose, or distilled water had good peak video intensities. At 30 s after peak time, Levovist reconstituted with Lactate Ringer's solution had greater enhancement and less decay than the other 5 solutions (P<0.001). In vivo, at 180 heart beats after peak time, the video intensity decay with 5% glucose was greater than that with distilled water (150+/-13 dB, 123+/-25 dB, respectively, P<0.05).

CONCLUSION

In this study, among various (2.5-20%) glucose solutions, the stability of the microbubbles differed, depending on the degree of osmotic pressure of the respective solutions; 5% glucose was the best. However, overall, the most suitable solution for reconstituting Levovist, was Lactate Ringer's solution. These findings could lead to effective strategies for better contrast echocardiography using Levovist by changing the current solution of choice to Lactate Ringer's solution or 5% glucose.

Effects of Left Bundle-Branch Block on Cardiac Structure, Function, Perfusion, and Perfusion Reserve

Background— We aimed to investigate the cardiac effects of left bundle-branch block (LBBB) using myocardial contrast echocardiography (MCE) to ascertain the value of MCE for detecting coronary artery disease (CAD) and to uncover the mechanism that affects the accuracy of single-photon emission computed tomography (SPECT) in these patients.

Methods and Results— Sixty-three symptomatic LBBB patients (group A), 10 left ventricular ejection fraction–matched control subjects without LBBB and no CAD (group B), and 10 normal control subjects (group C) underwent resting echocardiography. Rest and vasodilator MCE and SPECT were undertaken in LBBB patients. Septal (SW) and posterior wall (PW) thickness, thickening, quantitative myocardial blood flow (MBF), and MBF reserve were measured. SW/PW thickness and percentage thickening ratios were lower ( P <0.01 and P <0.05, respectively) in group A compared with both groups B and C, but resting SW/PW MBF and MBF reserve ratios were similar in all 3 groups. MBF reserve but not MBF was reduced in groups A and B (2.2±0.7 versus 2.2±0.2; P =0.98) compared with group C (3.1±0.5; P <0.01). SW thickness was an independent predictor ( P =0.006) of SPECT perfusion defects in LBBB patients without CAD. MCE (92%) had a sensitivity similar to SPECT (92%); however, the specificity of MCE (95%) was superior ( P <0.0001) to SPECT (47%) for the detection of CAD.

Conclusions— Despite asymmetrical reduction in SW thickness and function, MBF is preserved and MBF reserve is homogeneously reduced in LBBB patients with left ventricular systolic dysfunction. Because of partial volume effects, the accuracy of SPECT for detecting CAD was significantly compromised compared with MCE in this patient cohort.

Contrast echocardiography: evidence for clinical use

The failure of echocardiography to give diagnostically useful information in a significant proportion of patients has led to the development of specific contrast agents to enhance imaging. Suitable contrast media must have the ability to modify ultrasound characteristics, be capable of crossing the pulmonary capillary bed, show stability over the duration of a procedure, offer low blood solubility with low toxicity and be rapidly eliminated. The current generation of ultrasound contrast agents comprises microbubbles of a high molecular-weight gas encapsulated in a shell of phospholipid or protein. A review of the clinical evidence shows that these agents are clinically effective in enhancing echocardiographic imaging. They enable the rescue of failed procedures, often sparing patients from invasive tests, but appear not to add to the burden of side effects. Indeed, the benefits of using contrast agents in stress echocardiography have been recommended in recently published American Society of Echocardiography guidelines. Myocardial contrast echocardiography has now developed to the stage where assessment of myocardial perfusion for the detection of coronary artery disease is possible with the same diagnostic accuracy as radionuclide imaging. However, in comparison with the latter technique, it is less expensive, is more portable, and avoids the use of ionizing radiation. It is precisely the ability of myocardial contrast echocardiography to simultaneously assess function and perfusion at the bedside that has given it a unique role in clinical practice. This review provides an overview of the clinical evidence supporting the efficacy of contrast echocardiography in the assessment of myocardial structure, function, and perfusion.

Non-Invasive Detection of Coronary Artery Disease in Patients With Left Bundle Branch Block Using 64-Slice Computed Tomography

OBJECTIVES

The goal of this study was to evaluate the diagnostic accuracy of 64-slice computed tomography (CT) to identify coronary artery disease (CAD) in patients with complete left bundle branch block (LBBB).

BACKGROUND

Left bundle branch block increases risk of cardiac mortality, and prognosis is primarily determined by the underlying coronary disease. Non-invasive stress tests have limited performance, and conventional coronary angiography (CCA) is usually required.

METHODS

Sixty-six consecutive patients with complete LBBB and sinus rhythm admitted for CCA were enrolled. Computed tomography was performed 3 +/- 3.9 days before CCA. The accuracy of 64-slice CT to detect significant stenosis (>50% lumen narrowing) was compared with quantitative coronary angiography. All segments were analyzed regardless of image quality from coronary calcification or motion artifacts. Results were analyzed by patient and by coronary segment (990) using the American Heart Association 15-segment model.

RESULTS

Lower heart rates were associated with improved image quality. Computed tomography correctly identified 35 of 37 (95%) patients without significant stenosis and 28 of 29 (97%) patients with significant stenosis on CCA. Computed tomography correctly assessed 68 of 94 (72%) significant stenosis. Overall, accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 64-slice CT for identifying CAD by patient was 95%, 97%, 95%, 93%, and 97%, respectively, and by segment was 97%, 72%, 99%, 91%, and 97%, respectively.

CONCLUSIONS

In a routine clinical practice, 64-slice CT detects with excellent accuracy a significant CAD in patients with complete LBBB. A normal CT in this clinical setting is a robust tool to act as a filter and avoid invasive diagnostic procedures.