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

Contrast echocardiography: a practical guideline from the British Society of Echocardiography

Ultrasound contrast agents (UCAs) have a well-established role in clinical cardiology. Contrast echocardiography has evolved into a routine technique through the establishment of contrast protocols, an excellent safety profile, and clinical guidelines which highlight the incremental prognostic utility of contrast enhanced echocardiography. This document aims to provide practical guidance on the safe and effective use of contrast; reviews the role of individual staff groups; and training requirements to facilitate its routine use in the echocardiography laboratory.

The Role and Advantages of Cardiac Magnetic Resonance in the Diagnosis of Myocardial Ischemia

Ischemic heart disease continues to be the leading cause of death and disability worldwide. For the diagnosis of ischemic heart disease, some form of cardiac stress test involving exercise or pharmacological stimulation continues to play an important role, despite advances within modalities like computer tomography for the noninvasive detection and characterization of epicardial coronary lesions. Among noninvasive stress imaging tests, cardiac magnetic resonance (CMR) combines several capabilities that are highly relevant for the diagnosis of ischemic heart disease: assessment of wall motion abnormalities, myocardial perfusion imaging, and depiction of replacement and interstitial fibrosis markers by late gadolinium enhancement techniques and T1 mapping. On top of these qualities, CMR is also well tolerated and safe in most clinical scenarios, including in the presence of cardiovascular implantable devices, while in the presence of renal disease, gadolinium-based contrast should only be used according to guidelines. CMR also offers outstanding viability assessment and prognostication of cardiovascular events. The last 2019 European Society of Cardiology guidelines for chronic coronary syndromes has positioned stress CMR as a class I noninvasive imaging technique for the diagnosis of coronary artery disease in symptomatic patients. In the present review, we present the current state-of-the-art assessment of myocardial ischemia by stress perfusion CMR, highlighting its advantages and current shortcomings. We discuss the safety, clinical, and cost-effectiveness aspects of gadolinium-based CMR-perfusion imaging for ischemic heart disease assessment.

Cardiovascular positron emission tomography: established and emerging role in cardiovascular diseases

Cardiac positron emission tomography (PET) imaging has established themselves firmly as excellent and reliable functional imaging modalities in assessment of the spectrum of coronary artery disease. With the explosion of technology advances and the dream of flow quantification now a reality, the value of PET is now well realized. Cardiac PET has proved itself as precise imaging modality that provides functional imaging of the heart in addition to anatomical imaging. It has established itself as one of the best available techniques for evaluation of myocardial viability. Hybrid PET/computed tomography provides simultaneous integration of coronary anatomy and function with myocardial perfusion and metabolism, thereby improving characterization of the dysfunctional area and chronic coronary artery disease. The availability of quantitative myocardial blood flow evaluation with PET provides additional prognostic information and increases diagnostic accuracy in the management of patients with coronary artery disease. Hybrid imaging seems to hold immense potential in optimizing management of cardiovascular diseases and furthering clinical research.

Clustering of patients with inconclusive non-invasive stress testing referred for vasodilator stress cardiovascular magnetic resonance

BACKGROUND

Inconclusive non-invasive stress testing is associated with impaired outcome. This population is very heterogeneous, and its characteristics are not well depicted by conventional methods.

AIMS

To identify patient subgroups by phenotypic unsupervised clustering, integrating clinical and cardiovascular magnetic resonance data to unveil pathophysiological differences between subgroups of patients with inconclusive stress tests.

METHODS

Between 2008 and 2020, consecutive patients with a first inconclusive non-invasive stress test referred for stress cardiovascular magnetic resonance were followed for the occurrence of major adverse cardiovascular events (defined as cardiovascular death or myocardial infarction). A cluster analysis was performed on clinical and cardiovascular magnetic resonance variables.

RESULTS

Of 1402 patients (67% male; mean age 70±11years) who completed the follow-up (median 6.5years, interquartile range 5.6-7.5years), 197 experienced major adverse cardiovascular events (14.1%). Three distinct phenogroups were identified based upon unsupervised hierarchical clustering of principal components: phenogroup 1=history of percutaneous coronary intervention with viable myocardial infarction and preserved left ventricular ejection fraction; phenogroup 2=atrial fibrillation with preserved left ventricular ejection fraction; and phenogroup 3=coronary artery bypass graft with non-viable myocardial scar and reduced left ventricular ejection fraction. Using survival analysis, the occurrence of major adverse cardiovascular events (P=0.007), cardiovascular mortality (P=0.002) and all-cause mortality (P<0.001) differed among the three phenogroups. Phenogroup 3 presented the worse prognosis. In each phenogroup, ischaemia was associated with major adverse cardiovascular events (phenogroup 1: hazard ratio 2.79, 95% confidence interval 1.61-4.84; phenogroup 2: hazard ratio 2.59, 95% confidence interval 1.69-3.97; phenogroup 3: hazard ratio 3.16, 95% confidence interval 1.82-5.49; all P<0.001).

CONCLUSIONS

Cluster analysis of clinical and cardiovascular magnetic resonance variables identified three phenogroups of patients with inconclusive stress testing, with distinct prognostic profiles.

Impact of ultrasound enhancing agents on clinical management

PURPOSE OF REVIEW

Ultrasound enhancing agents (UEAs), microbubbles which are composed of lipid or albumin shells containing high molecular weight gases with nonlinear acoustic properties in the ultrasound field, are important components of the diagnostic armamentarium in echocardiography. This review highlights the substantial value of UEAs in delineating endocardial border definition and influencing downstream decision-making in cardiovascular ultrasound.

RECENT FINDINGS

In this article, we review recent updates to the clinical applications of UEAs, special circumstances regarding use, the impact of use on downstream testing and cost-effectiveness, and recommended approaches for optimizing workflow in the echocardiography laboratory with UEAs.

SUMMARY

In multiple studies, UEAs have been identified as a useful tool in echocardiography, improving study accuracy and reader confidence, while reducing downstream testing and procedures and resulting in significant changes in clinical management. Despite their proven efficacy and cost-effectiveness, recent studies have suggested utilization remains low, in part due to perceived concerns and workflow issues that impair uptake. With an increasingly broader list of indications for echocardiography, UEAs will continue to play an important role in the diagnosis and management of patients with cardiovascular and noncardiovascular diseases.

To what extent are perfusion defects seen by myocardial perfusion SPECT in patients with left bundle branch block related to myocardial infarction, ECG characteristics, and myocardial wall motion?

INTRODUCTION

We investigated if uptake pattern on myocardial perfusion SPECT (MPS) in patients with left bundle branch block (LBBB) is related to myocardial fibrosis, myocardial wall motion, and electrocardiography (ECG) characteristics.

METHODS

Twenty-three patients (9 women) with LBBB, examined with MPS and cardiac magnetic resonance (CMR), were included. Tracer uptake on MPS was classified by visual interpretation as typical LBBB pattern (Defect+, n = 13) or not (Defect-, n = 10) and quantitatively. CMR images were evaluated for wall thickness and for myocardial wall motion both by visual assessment and by regional myocardial radial strain from feature tracking, and for presence and location of myocardial fibrosis. ECGs were analyzed regarding QRS duration and the presence of strict criteria for LBBB.

RESULTS

Wall thickness was slightly lower in the septum compared to the lateral wall in Defect+ patients (5.6 ± 1.1 vs 6.0 ± 1.3 mm, P = 0.03) but not in Defect- patients (5.6 ± 1.0 vs 5.6 ± 0.9 mm, P = 0.84). Defect+ patients showed a larger proportion of dyskinetic segments in the septum and hyperkinetic segments in the lateral wall compared to Defect- patients (P = 0.006 and P = 0.004, respectively). Decreased myocardial radial strain was associated with decreased tracer uptake by MPS (R = 0.37, P < 0.001). Areas of fibrosis did not match areas with uptake defect on MPS. No differences in ECG variables were seen.

CONCLUSION

The heterogeneous regional tracer uptake in some patients with LBBB is related to underlying regional myocardial dyskinesia, wall thickening, and wall thickness rather than stress-induced ischemia, myocardial fibrosis, or specific ECG characteristics.

Prognostic value of dipyridamole stress perfusion cardiovascular magnetic resonance in elderly patients >75 years with suspected coronary artery disease

AIMS

There are only very few data on the prognostic value of stress cardiovascular magnetic resonance (CMR) in elderly people, while life expectancy of the general population is steadily increasing. Therefore, this study aims to assess the prognostic value of vasodilator stress perfusion CMR in elderly >75 years.

METHODS AND RESULTS

Between 2008 and 2017, we included consecutive elderly >75 years without known coronary artery disease (CAD) referred for dipyridamole stress CMR. They were followed for the occurrence of major adverse cardiovascular events (MACE) including cardiac death or non-fatal myocardial infarction. Univariate and multivariate analyses were performed to determine the prognostic value of ischaemia or late gadolinium enhancement. Of 754 elderly individuals (82.0 ± 3.9 years, 48.4% men), 659 (87.4%) completed the follow-up with median follow-up of 4.7 years. Using Kaplan-Meier analysis, the presence of myocardial ischaemia was associated with the occurrence of MACE [hazard ratio (HR) 5.38, 95% confidence interval (CI): 3.56-9.56; P < 0.001]. In a multivariable Cox regression including clinical characteristics and CMR indexes, inducible ischaemia was an independent predictor of a higher incidence of MACE (HR 4.44, 95% CI: 2.51-7.86; P < 0.001). In patients without ischaemia, the occurrence of MACE was lower in women when compared with men (P < 0.01).

CONCLUSION

Stress CMR is safe and has discriminative prognostic value in elderly, with a significantly lower event rate of future cardiovascular event or death in subjects without ischaemia or infarction.

Updated knowledge and practical implementations of stress echocardiography in ischemic and non-ischemic cardiac diseases: an expert consensus of the Working Group of Echocardiography of the Hellenic Society of Cardiology

Stress echocardiography (SE) is a well-established and valid technique, widely-used for the diagnostic evaluation of patients with ischemic and non-ischemic cardiac diseases. This statement of the Echocardiography Working Group of the Hellenic Society of Cardiology summarizes the consensus of the writing group regarding the applications of SE, based on the expertise of their members and on a critical review of current medical literature. The main objectives of the consensus document include a comprehensive review of SE methodology and training, focusing on the preparation, the protocols used and the analysis of the SE images and an updated, evidence-based knowledge about SE applications on ischemic and non-ischemic heart diseases, such as in cardiomyopathies, heart failure and valvular heart disease.

Prognostic Value of Vasodilator Stress Perfusion Cardiovascular Magnetic Resonance in Patients With Prior Myocardial Infarction

OBJECTIVES

This study sought to assess the incremental prognostic value of vasodilator stress cardiovascular magnetic resonance (CMR) in patients with prior myocardial infarction (MI).

BACKGROUND

Recurrent MI is a major cause of mortality and morbidity among MI survivors.

METHODS

Between 2008 and 2019, consecutive patients with prior MI referred for stress CMR were followed up for the occurrence of major adverse cardiovascular events (MACE), defined by cardiovascular mortality or recurrent nonfatal MI. Uni- and multivariable Cox regressions were performed to determine the prognostic value of inducible ischemia and the extent of myocardial scar.

RESULTS

Among 1,594 patients with prior MI and myocardial scar on CMR, 1,401 (92%) (68.2 ± 11.0 years; 61.4% men) completed the follow-up (median: 6.2 years), and 205 had MACE (14.6%). Patients without inducible ischemia experienced a lower annual rate of MACE (3.1%) than those with 1-2 (4.9%), 3-5 (21.5%), or ≥6 segments of ischemia (45.7%) (all p < 0.01). Using Kaplan-Meier analysis, the presence of inducible ischemia and the extent of scar were associated with MACE (hazard ratio [HR]:3.52; 95% confidence interval [CI]: 2.67 to 4.65 and HR: 1.66; 95% CI: 1.53 to 2.18, respectively; both p < 0.001). In multivariable stepwise Cox regression, the presence of ischemia and the extent of scar were independent predictors of MACE (HR: 2.84; 95% CI: 2.14 to 3.78 and HR: 1.57; 95% CI: 1.44 to 1.72, respectively; both p < 0.001). These findings were significant in both symptomatic and asymptomatic patients. The addition of CMR parameters to the model including traditional risk factors resulted in a better discrimination for MACE (C-statistic: 0.76 vs. 0.62).

CONCLUSIONS

In patients with prior MI, vasodilator stress CMR has independent and incremental prognostic value over traditional risk factors.

Diagnostic accuracy of SPECT and PET myocardial perfusion imaging in patients with left bundle branch block or ventricular-paced rhythm

BACKGROUND

The difference in diagnostic accuracy of coronary artery disease (CAD) between vasodilator SPECT and PET myocardial perfusion imaging (MPI) in patients with left bundle branch block (LBBB) or ventricular-paced rhythm (VPR) is unknown.

METHODS

We identified patients with LBBB or VPR who underwent either vasodilator SPECT or PET MPI and subsequent coronary angiography. LBBB/VPR-related septal and anteroseptal defects were defined as perfusion defects involving those regions in the absence of obstructive CAD in the left anterior descending artery or left main coronary artery.

RESULTS

Of the 55 patients who underwent coronary angiography, 38 (69%) underwent SPECT and 17 patients (31%) underwent PET. PET compared to SPECT demonstrated higher sensitivity (88% vs 60%), specificity (56% vs 14%), positive predictive value (64% vs 20%), negative predictive value (83% vs 50%), and overall superior diagnostic accuracy (AUC .72 (95% CI .50-.93) vs .37 (95% CI .20-.54), P = .01) to detect obstructive CAD. LBBB/VPR-related septal and anteroseptal defects were more common with SPECT compared to PET (septal: 72% vs 17%, P = .001; anteroseptal: 47% vs 8%, P = .02).

CONCLUSIONS

PET has higher diagnostic accuracy when compared to SPECT for the detection of obstructive CAD in patients with LBBB or VPR.

Initial experience with regadenoson stress positron emission tomography in patients with left bundle branch block: Low prevalence of septal defects and high accuracy for obstructive coronary artery disease

BACKGROUND

Assessing for coronary artery disease (CAD) in patients with left bundle branch block (LBBB) is difficult with noninvasive cardiac imaging. Few studies report the prevalence of LBBB associated septal-apical perfusion defects using regadenoson stress on Positron Electron Tomography (PET) imaging.

METHODS AND RESULTS

We identified 101 consecutive patients with baseline LBBB, and without known CAD, who underwent rest-stress regadenoson PET. Investigators have the ability to prospectively identify studies, whose quality is limited by LBBB artifact. With the infusion of regadenoson, resting to peak stress heart rate rose from a median of 78 to 93 BPM. Despite this, LBBB perfusion artifacts were not identified in any studies. 10 individuals had both regadenoson SPECT and PET within 1 year. 3 of the 10 SPECT studies had LBBB artifacts, all of which were not seen on subsequent PET. 21 patients with PET had subsequent coronary angiography. Of these, 9 PETs were without significant inducible ischemia, and angiogram was without flow-limiting disease. 3 PETs identified inducible ischemia, but did not have flow-limiting disease on angiogram. 9 PETs identified inducible ischemia and had flow-limiting disease on angiogram.

CONCLUSIONS

In patients with LBBB undergoing regadenoson PET stress imaging, artifactual septal perfusion defects are rare.

Feasibility and Prognostic Value of Vasodilator Stress Perfusion CMR in Patients With Atrial Fibrillation

OBJECTIVES

The aim of this study was to assess the feasibility and prognostic value of vasodilator stress perfusion cardiovascular magnetic resonance (CMR) in patients with atrial fibrillation (AF).

BACKGROUND

Because most studies have excluded arrhythmic patients, the prognostic value of stress perfusion CMR in patients with AF is unknown.

METHODS

Between 2008 and 2018, consecutive patients with suspected or stable chronic coronary artery disease and AF referred for vasodilator stress perfusion CMR were included and followed for the occurrence of major adverse cardiovascular event(s) (MACE), defined as cardiovascular death or nonfatal myocardial infarction. The diagnosis of AF was defined by 12-lead electrocardiography before and after CMR. Univariate and multivariate Cox regressions were performed to determine the prognostic value of inducible ischemia or late gadolinium enhancement (LGE) by CMR.

RESULTS

Of 639 patients (mean age 72 ± 9 years, 77% men), 602 (94%) completed the CMR protocol, and 538 (89%) completed follow-up (median 5.1 years); 80 had MACE. Using Kaplan-Meier analysis, the presence of ischemia (hazard ratio [HR]: 7.56; 95% confidence interval [CI]: 4.86 to 11.80) or LGE (HR: 2.41; 95% CI: 1.55 to 3.74) was associated with the occurrence of MACE (p < 0.001 for both). In a multivariate Cox regression including clinical and CMR indexes, the presence of ischemia (HR: 5.98; 95% CI: 3.68 to 9.73) or LGE (HR: 2.61; 95% CI: 1.89 to 3.60) was an independent predictor of MACE (p < 0.001 for both).

CONCLUSIONS

In patients with AF, stress perfusion CMR is feasible and has good discriminative prognostic value to predict the occurrence of MACE.

Safety and Prognostic Value of Vasodilator Stress Cardiovascular Magnetic Resonance in Patients With Heart Failure and Reduced Ejection Fraction

Background:

Patients with heart failure with reduced ejection fraction (HFrEF; heart failure with reduced left ventricular ejection fraction <40%) referred for stress cardiovascular magnetic resonance (CMR) may have a less optimal hemodynamic response to intravenous vasodilator. The aim was to assess the prognostic value of vasodilator stress perfusion CMR in patients with HFrEF.

Methods:

Between 2008 and 2018, consecutive patients with HFrEF defined by left ventricular ejection fraction <40% prospectively referred for vasodilator stress perfusion CMR were followed for the occurrence of major adverse cardiovascular events (MACE), defined by cardiovascular death or nonfatal myocardial infarction. Univariable and multivariable Cox regressions were performed to determine the prognostic value of inducible ischemia or late gadolinium enhancement by CMR.

Results:

Of 1053 patients with HFrEF (65±11 years, median [interquartile range] left ventricular ejection fraction 38.7% [37.2–39.0]), 1018 (97%) completed the CMR protocol and 950 (93%) completed the follow-up (median [interquartile range], 5.6 [3.6–7.3] years); 117 experienced a MACE (12.3%). Stress CMR was well tolerated without any adverse events. Patients without ischemia or late gadolinium enhancement experienced a lower annual event rate of MACE (1.8%) than those with both ischemia and late gadolinium enhancement (12.0%; P <0.001). Using Kaplan-Meier analysis, inducible ischemia and late gadolinium enhancement were significantly associated with the occurrence of MACE (hazard ratio, 2.46 [95% CI, 1.69–3.60]; and hazard ratio, 2.92 [95% CI, 1.77–4.83], respectively, both P <0.001). In multivariable Cox regression, inducible ischemia was an independent predictor of a higher incidence of MACE (hazard ratio, 2.26 [95% CI, 1.52–3.35]; P <0.001).

Conclusions:

Stress CMR is safe and has a good discriminative prognostic value to predict the occurrence of MACE in patients with HFrEF.

New Applications in Echocardiography for Ultrasound Contrast Agents in the 21st Century

Contrast echocardiography microbubbles are ultrasound-enhancing agents that were originally designed to help improve endocardial border definition, known as left ventricle opacification, and to enhance Doppler signals. Over time, contrast microbubbles are used to assess myocardial perfusion because they travel through the capillaries of the cardiac circulation. Current research provides good evidence that myocardial perfusion echocardiography improves comprehensive echocardiographic evaluations of ischemic heart disease. The approval of regulatory authorities and the availability of quantitative operator-independent analysis software will hopefully prompt physicians and sonographers to implement myocardial perfusion echocardiography into the daily workflow of echo laboratories. New diagnostic and therapeutic applications will result in improved patient care, especially in the area of sonothrombolysis, where preliminary data have already shown utilization in ST elevation myocardial infarction, improving left ventricular systolic function and reducing the need for implantable defibrillators at 6-mo follow-up. This review gives an overview of the applications of myocardial perfusion imaging with ultrasound. Each cited study had institutional review board/institutional animal care and use approval.

Left Bundle Branch Block: Current and Future Perspectives

Left bundle branch block may be due to conduction system degeneration or a reflection of myocardial pathology. Left bundle branch block may also develop following aortic valve disease or cardiac procedures. Patients with heart failure with reduced ejection fraction and left bundle branch block may respond positively to cardiac resynchronization therapy. Lead placement via the coronary sinus is the mainstay approach of cardiac resynchronization therapy. However, other options, including physiological pacing, are being explored. In this review, we summarize the salient pathophysiologic and clinical aspects of left bundle branch block, as well as current and future strategies for management.

Stress echocardiography in coronary artery disease: a practical guideline from the British Society of Echocardiography

Stress echocardiography is an established technique for assessing coronary artery disease. It has primarily been used for the diagnosis and assessment of patients presenting with chest pain in whom there is an intermediate probability of coronary artery disease. In addition, it is used for risk stratification and to guide revascularisation in patients with known ischaemic heart disease. Although cardiac computed tomography has recently been recommended in the United Kingdom as the first-line investigation in patients presenting for the first time with atypical or typical angina, stress echocardiography continues to have an important role in the assessment of patients with lesions of uncertain functional significance and patients with known ischaemic heart disease who represent with chest pain. In this guideline from the British Society of Echocardiography, the indications and recommended protocols are outlined for the assessment of ischaemic heart disease by stress echocardiography.

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.

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.

Prognostic usefulness of contemporary stress echocardiography in patients with left bundle branch block and impact of contrast use in improving prediction of outcome

Aims

Patients with symptomatic left bundle branch block (LBBB) may have myocardial ischaemia due to both coronary artery disease and/or cardiomyopathy (microcirculatory abnormalities) and may have concomitant left ventricular (LV) dysfunction. We aimed to assess the feasibility and prognostic value of contemporary stress echocardiography (SE), which can uncover both pathophysiologies in LBBB patients in routine clinical practice, and also aimed to assess the additive value of contrast SE.

Methods and results

Accordingly, 190 consecutive patients (age 70.5 ± 11.3 years, LV ejection fraction = 50.1 ± 10%) with symptomatic LBBB who underwent SE over 6 years were assessed, of which 142 (75%) underwent contrast SE and 176 (92.6%) had diagnostic SE. Inducible ischaemia was present in 25 (14.2%) patients. During follow-up (35.4 ± 20.2 months) there were 32 deaths (18%) and 18 (10.2%) first cardiovascular (CV) events (acute myocardial infarction/mortality) in the 176 patients with diagnostic studies. Wall thickening score index at peak stress (WTSIpeak), which measures combined LV function and inducible ischaemia, was an independent predictor of mortality (HR = 3.78, 95% CI = 1.39-10.31, P = 0.01) and CV events (HR = 3.96, 95% CI = 1.1-14.3, P = 0.036). An abnormal SE (myocardial ischaemia and/or abnormal LV function) predicted an almost three-fold increase in all-cause mortality and CV events compared with normal SE. Amongst the confounders affecting assessment of wall thickening in LBBB and conventional prognostic variables, use of contrast was an independent predictor (P = 0.034) of WTSI1.16 (optimal predictor of mortality/CV outcome).

Conclusion

SE in patients with LBBB demonstrated high feasibility and the combination of LV systolic function and myocardial ischaemia provided important prognostic information. Contrast-enhanced SE improved the prediction of outcome.

Sequential SPECT/CT imaging for detection of coronary artery disease in a large cohort: evaluation of the need for additional imaging and radiation exposure

BACKGROUND

Performing both single photon emission computerized tomography (SPECT) and coronary computed tomography angiography (CCTA) in patients suspected for coronary artery disease (CAD) leads to increased radiation exposure. We evaluated the need for additional imaging and following implications for radiation exposure of a sequential SPECT/computed tomography (CT) algorithm.

METHODS AND RESULTS

5018 consecutive patients without history of CAD were referred for stress-first SPECT and coronary artery calcium (CAC) scoring. If stress SPECT was abnormal, additional rest SPECT and, if feasible, CCTA were acquired. Stress SPECT was normal in 2617 patients (52%). CCTA was not performed in 1289 of the 2401 patients referred for additional imaging (54%), mainly because of severe CAC (47%) or fast/irregular heart rate (22%). 642 patients with abnormal SPECT underwent CCTA, which excluded significant CAD in 378 patients (59%). Mean radiation dose was 4.5 ± 0.3 mSv for stress-only imaging and 13.2 ± 3.3 mSv for additional imaging (P < 0.001).

CONCLUSIONS

Half of the patients do not require additional imaging in our sequential SPECT/CT algorithm, which is accompanied with low radiation exposure. CCTA cannot be performed in half of the patients who undergo additional imaging because of (relative) contra-indications. CCTA is able to correct for false-positive SPECT findings in our algorithm.

Resting Myocardial Contrast Echocardiography for the Evaluation of Coronary Microcirculation Dysfunction in Patients With Early Coronary Artery Disease

BACKGROUND

Coronary microcirculation dysfunction can occur in patients with chest pain suggestive of coronary artery disease (CAD). The present study aimed to determine the diagnostic value of resting myocardial contrast echocardiography (MCE) for early CAD with myocardial microcirculation dysfunction by evaluating the continuous imaging time, peak time, and peak intensity.

HYPOTHESIS

Resting MCE is an effective and noninvasive method for evaluation of coronary microcirculation dysfunction in patients with early coronary artery disease.

METHODS

The present study included 20 consecutive patients without obvious clinical evidence of early CAD and 20 healthy volunteers. Resting MCE was performed to evaluate the myocardial microcirculation perfusion, and the follow-up evaluation of myocardial microcirculation perfusion was performed with technetium 99 m 2-methoxy-isobutyl-isonitrile ((99m) Tc-MIBI) single-photon emission computed tomography (SPECT).

RESULTS

Peak intensity was significantly lower in patients with high risk of CAD than in controls (P < 0.0001). The peak time and continuous imaging time were significantly higher in patients with high risk of CAD than in controls (P < 0.0001). None of the 40 subjects experienced discomfort, such as cough and chest tightness, during the resting MCE procedure, and the heart rate and blood pressure showed no abnormalities during the entire procedure. SPECT imaging showed reversible myocardial perfusion reduction in 80% (16/20) of the patients with high risk of CAD. Abnormalities of heart rate and blood pressure and adverse reactions were noted during the process of SPECT examination.

CONCLUSIONS

Resting MCE is an effective and noninvasive method for detecting abnormalities of coronary microcirculation and can help in the clinical analysis, risk assessment, and treatment of early occult CAD.

Regadenoson stress for myocardial perfusion imaging

Noninvasive functional imaging plays a major role in the diagnosis of hemodynamically significant coronary artery disease (CAD) by means of the detection of abnormal myocardial perfusion. For this, cardiac stressors are essential as they induce hypoperfusion in the presence of flow-limiting coronary stenosis. Several pharmacological stressors are currently available and it is important that clinicians who are involved in the care and management of patients with CAD become familiar with their indications, contraindications and protocols. Among the primary coronary vasodilator agents, regadenoson is increasingly used as the default stressor or as an alternative to other modalities of stress. This article provides an updated review of regadenoson stress for the assessment of patients with suspected or known CAD and describes its pharmacological properties, stress protocol, efficacy and safety profile.

Dipyridamole stress myocardial perfusion by computed tomography in patients with left bundle branch block

Background

Functional tests have limited accuracy for identifying myocardial ischemia in patients with left bundle branch block (LBBB).

Objective

To assess the diagnostic accuracy of dipyridamole-stress myocardial computed tomography perfusion (CTP) by 320-detector CT in patients with LBBB using invasive quantitative coronary angiography (QCA) (stenosis ≥ 70%) as reference; to investigate the advantage of adding CTP to coronary computed tomography angiography (CTA) and compare the results with those of single photon emission computed tomography (SPECT) myocardial perfusion scintigraphy.

Methods

Thirty patients with LBBB who had undergone SPECT for the investigation of coronary artery disease were referred for stress tomography. Independent examiners performed per-patient and per-coronary territory assessments. All patients gave written informed consent to participate in the study that was approved by the institution’s ethics committee.

Results

The patients’ mean age was 62 ± 10 years. The mean dose of radiation for the tomography protocol was 9.3 ± 4.6 mSv. With regard to CTP, the per-patient values for sensitivity, specificity, positive and negative predictive values, and accuracy were 86%, 81%, 80%, 87%, and 83%, respectively (p = 0.001). The per-territory values were 63%, 86%, 65%, 84%, and 79%, respectively (p < 0.001). In both analyses, the addition of CTP to CTA achieved higher diagnostic accuracy for detecting myocardial ischemia than SPECT (p < 0.001).

Conclusion

The use of the stress tomography protocol is feasible and has good diagnostic accuracy for assessing myocardial ischemia in patients with LBBB.

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.

Comprehensive dobutamine stress CMR versus echocardiography in LBBB and suspected coronary artery disease

OBJECTIVES

This study aimed to compare dobutamine stress cardiac magnetic resonance (DSCMR) with dobutamine stress echocardiography (DSE) in patients with left bundle branch block (LBBB) and suspected coronary artery disease (CAD).

BACKGROUND

Noninvasive diagnosis of CAD in patients with pre-existent LBBB is difficult because single-photon emission computed tomography and stress echocardiography both have limitations. We hypothesized that a comprehensive DSCMR examination including cine, perfusion, and late gadolinium enhancement imaging would be more accurate than DSE, thus potentially reducing the number of unnecessary invasive coronary angiograms.

METHODS

We prospectively evaluated 82 consecutive patients with LBBB referred to our cardiology clinic for investigation of suspected CAD. All 82 patients underwent DSE, DSCMR, and invasive quantitative coronary angiography within 14 days. We compared the diagnostic accuracy of DSE, CMR cine imaging, the additive value of first-pass perfusion, and late gadolinium enhancement. In the comprehensive examination, a positive result was adjudged as the presence of either subendocardial or transmural late gadolinium enhancement with or without inducible peri-infarct ischemia or an inducible perfusion defect corresponding to an inducible regional wall motion abnormality.

RESULTS

CMR cine imaging (regional wall motion abnormalities) had higher specificity, negative predictive value, and overall diagnostic accuracy than did DSE (87.5% vs. 72.9%; 80.8% vs. 67.3%; and 80.4% vs. 72.0%, respectively), although sensitivity was the same (72.0%). The addition of first-pass stress perfusion and late gadolinium enhancement (scar) further improved diagnostic confidence (sensitivity 82.4%, specificity 95.8%, positive predictive value 93.3%, negative predictive value 88.5%, and diagnostic accuracy 90.2%).

CONCLUSIONS

DSCMR is a safe procedure and has greater diagnostic accuracy than does DSE in assessing patients with suspected CAD and LBBB. A comprehensive examination with the addition of perfusion and late gadolinium enhancement to CMR cine imaging significantly boosted specificity and sensitivity, making DSCMR a reliable alternative to invasive quantitative coronary angiography in this group of patients.

Implications of left bundle branch block in patient treatment

Left bundle branch block (LBBB) causes an abnormal pattern of cardiac activation and affects regional myocardial function. Although recognition of LBBB on the surface electrocardiogram is straightforward, dissecting its effect on patient treatment and outcome can be more challenging. The altered pattern of cardiac activation in LBBB causes electrical and mechanical ventricular dyssynchrony, influences ischemia detection on the surface electrocardiogram, and affects stress testing and imaging modalities dependent on wall motion and thickening. Restoration of synchrony by biventricular pacing can improve symptoms and longevity in carefully selected patients. The diagnostic, prognostic, and therapeutic implications of LBBB across this spectrum are discussed in this review.

Assessing coronary artery disease in patients with anginal chest pain and left bundle branch block: an emerging role for a new parameter of cardiopulmonary exercise testing

Cardiopulmonary exercise testing (CPET) is used in cardiology to grade the severity of heart failure and to assess its prognosis. However, it is unknown whether CPET may be a useful technique to rule out coronary artery disease (CAD) in patients with anginal chest pain and left bundle branch block (LBBB). The aim of this investigation was to evaluate the diagnostic accuracy of CPET to identify CAD in these patients. A cohort of 90 patients with anginal chest pain, 45 with LBBB (group A) and 45 non-LBBB (group B), were studied with CPET and a single-photon emission computed tomographic myocardial perfusion study during the same period. The following variables of CPET were analyzed: peak oxygen uptake (VO2), VO2 at anaerobic threshold, and time to reach the anaerobic threshold (TAT). Group A values were lower compared with group B in peak VO2 (23 ± 6.2 vs. 28 ± 7.6 mLO2 · kg · min; P = 0.002), VO2 at anaerobic threshold (16.1 ± 3.6 vs. 18.9 ± 4.1 mLO2 · kg · min; P =0.001), and TAT (2.7 ± 0.96 vs. 4.4 ± 2.1 min; P < 0.001). Group A showed higher perfusion abnormalities in myocardial perfusion study than group B [27 (60%) vs. 12 (26.7%); P = 0.003]. Multivariate analysis showed that TAT (odds ratio = 1.59; 95% confidence interval, 1.06-2.39; P = 0.02) was the only independent predictor of CAD, after controlling for other factors. Receiver operator characteristic analysis showed an area under the curve of 0.78 for TAT (95% confidence interval, 0.68-0.86; P < 0.0001). In conclusion, our findings suggest that a new functional parameter such as TAT significantly predicts CAD in patients with anginal chest pain and LBBB.

Animal models of dyssynchrony

Cardiac resynchronization therapy (CRT) is an important therapy for patients with heart failure and conduction pathology, but the benefits are heterogeneous between patients and approximately a third of patients do not show signs of clinical or echocardiographic response. This calls for a better understanding of the underlying conduction disease and resynchronization. In this review, we discuss to what extent established and novel animal models can help to better understand the pathophysiology of dyssynchrony and the benefits of CRT.

Myocardial Structural, Perfusion, and Metabolic Correlates of Left Bundle Branch Block Mechanical Derangement in Patients With Dilated Cardiomyopathy

Background—

Left bundle branch block (LBBB) influences on regional left ventricular (LV) structure, perfusion, and metabolism have not yet been thoroughly investigated in dilated cardiomyopathy patients.

Methods and Results—

Eleven dilated cardiomyopathy patients with LBBB (mean±SD age, 62±11 years; LV ejection fraction, 35±8%) and 7 dilated cardiomyopathy patients without LBBB (mean±SD age, 58±9 years; LV ejection fraction, 37±10%) were studied by cardiac magnetic resonance and positron emission tomography. The left ventricle was divided in 3 regions: septum, adjacent (anterior-inferior walls), and lateral. Regional midwall circumferential strain, maximum shortening, and strain rate were obtained from tagged cardiac magnetic resonance. The systolic stretch index was calculated as positive strain rate (stretching) divided by total strain rate. Myocardial metabolic rate of glucose and resting and hyperemic myocardial blood flow were quantified by 2-[ 18 F]fluoro-2-deoxyglucose and [ 13 N]ammonia positron emission tomography, respectively. Compared with non-LBBB patients, LBBB patients showed a highly inhomogeneous systolic deformation pattern that changed gradually, moving from a discoordinate [(systolic stretch index, 0.485 (0.284)] and poorly contracting (maximum shortening, −1.14±0.96%) septum to a coordinate [systolic stretch index, 0.002 (0.168)] and strongly contracting (maximum shortening, −13.63±2.58%) lateral region (both P <0.0001). This pattern was closely matched to the myocardial metabolic rate of glucose, disclosing lowest, intermediate, and highest values in the septum, adjacent, and lateral regions, respectively ( P <0.0001). Septal-to-lateral thickness ratio was lower in LBBB than in non-LBBB patients ( P =0.03). In both groups, the LV distribution of resting and hyperemic myocardial blood flow and myocardial blood flow reserve did not differ significantly.

Conclusions—

In dilated cardiomyopathy patients, the extensive LV contraction abnormalities induced by LBBB cause regional myocardial metabolic and structural remodeling, without consistent changes in blood flow.

Myocardial perfusion imaging with contrast ultrasound

This report reviews the development and clinical application of myocardial perfusion imaging with myocardial contrast echocardiography (MCE). This includes the development of microbubble formulations that permit the detection of left ventricular contrast from venous injection and the imaging techniques that have been invented to detect the transit of these microbubbles through the microcirculation. The methods used to quantify myocardial perfusion during a continuous infusion of microbubbles are described. A review of the clinical studies that have examined the clinical utility of myocardial perfusion imaging with MCE during rest and stress echocardiography is then presented. The limitations of MCE are also discussed.

Myocardial perfusion SPECT identifies patients with left bundle branch block patterns at high risk for future coronary events

BACKGROUND

The value of myocardial perfusion SPECT (MPS) for patients with left bundle branch block (LBBB) or right ventricular apical (RVA) pacing seems reduced. The prognosis of patients with only abnormal activation related perfusion defects (AARD) due to LBBB or RVA-pacing is similar to those with a normal MPS. We assessed the prognostic value of MPS in patients with LBBB or RVA pacing.

METHODS

Patients with LBBB or RVA pacing referred for vasodilator stress MPS between April 2002 and January 2006 were analyzed. Group 1 are patients with normal MPS and MPS with AARD. Group 2 are patients with an MPS with a perfusion defect extending outside the AARD area. Events were cardiac death, acute myocardial infarction and coronary revascularization.

RESULTS

In Group 1 (101 patients) 12 events and in Group 2 (96 patients) 45 events occurred during a mean follow-up of 2.6 +/- 1.5 years. The prognosis of Group 2 was significantly worse (49%) compared with Group 1 (91%). The annual cardiac death rate was 0.7%/year in Group 1 and 6.4%/year in Group 2 (P < .001). The prognosis of patients with LBBB was not different from those with RVA pacing.

CONCLUSION

Group 2 had a significantly worse cardiac prognosis compared to Group 1. The annual cardiac death rate of <1% in Group 1 warrants a watchful waiting strategy, whereas the cardiac death rate in Group 2 warrants aggressive invasive coronary strategies.

Comparison between myocardial contrast echocardiography and (99m)technetium sestamibi single photon emission computed tomography determined myocardial viability in predicting hard cardiac events following acute myocardial infarction

The extent of residual myocardial viability (MV) after acute myocardial infarction (AMI) is an important determinant of the outcome. Single photon emission computed tomography (SPECT) is widely used to assess MV after an AMI. However, myocardial contrast echocardiography (MCE), a relatively new technique for the assessment of MV, has better spatial and temporal resolution than SPECT. The present study evaluated whether MV determined by MCE is comparable to that determined using SPECT for the prediction of hard cardiac events after an AMI. Accordingly, 99 patients who had undergone simultaneous rest low-power MCE and nitrate-enhanced SPECT 7 days after an AMI were followed up for cardiac death and AMIs. Both MCE perfusion (1 = normal; 2 = reduced; and 3 = absent) and SPECT tracer uptake (0 = normal; 1 = mildly reduced; 2 = moderately reduced; 3 = severely reduced; and 4 = absent) were scored on a 16-segment left ventricular model. The contrast perfusion index and SPECT perfusion index were calculated by adding the respective scores in the 16 segments and dividing by 16. The contrast perfusion index and SPECT perfusion index were used as a measure of the residual MV on MCE and SPECT, respectively. Of the 99 patients recruited, 95 were available for the follow-up examination (follow-up 46 +/- 16 months). A total of 15 events (16%) occurred (8 cardiac deaths and 7 AMIs). Of the clinical, biochemical, echocardiographic, and SPECT markers of prognosis, the only independent predictors of cardiac death and cardiac death or AMI were age and MV as determined by MCE (p = 0.01 and p = 0.002, respectively). In conclusion, MV determined by MCE at rest was superior to nitrate-enhanced SPECT for the prediction of hard cardiac events after AMI.

Myocardial perfusion defects in right ventricular apical pacing are caused by partial volume effects because of wall motion abnormalities: a new model to study gated myocardial SPECT with the pacemaker on and off

BACKGROUND

Myocardial perfusion defects have been shown in patients with abnormal intraventricular conduction. These defects have been ascribed to regional differences in myocardial blood flow caused by the abnormal activation. This proof of the concept study assesses the effects of abnormal electrical activation and subsequent wall motion abnormalities of the left ventricle on myocardial perfusion in a pacing model.

METHODS

Fourteen patients with normal atrio-ventricular (AV) and intraventricular conduction with a right ventricular apical (RVA) pacemaker for brady-tachycardia syndrome were studied to allow for intrapatient comparison. Tc-sestamibi was injected in atrial inhibited (AAI) pacing mode allowing uptake during normal intraventricular conduction. Imaging was performed with AAI pacing and the second image was acquired directly after the first scan with AV pacing with a short AV-interval ensuring complete AV pacing with abnormal ventricular activation patterns (RVA pacing). Left ventricular ejection fraction (LVEF), wall motion score and myocardial perfusion score (SSS) were assessed with gated single photon emission computed tomography (SPECT) during normal conduction (AAI) and with RVA pacing.

RESULTS

Left ventricular ejection fraction was normal in all patients. During AAI, three of 14 patients showed wall motion abnormalities, mean wall motion score 0.9+/-1.8 with a mean SSS 0.6+/-1.5 increasing to 4+/-6.2 and 3.6+/-5.8 (P<0.01), respectively during RVA pacing. Wall motion abnormalities were found in the apex, inferior, inferoseptal and septal walls.

CONCLUSION

Despite a fixed amount of tracer activity in the myocardium, larger and more perfusion defects were visible during RVA pacing compared with normal conduction. The site and severity of the perfusion defects correlates with abnormal wall motion because of this pacing mode. This implies that abnormal wall motion is at least partly responsible for the apparent myocardial perfusion defects.

[Cardiac memory of the ECG following ventricular pacing]

During abnormal pacemaker depolarization, abnormal repolarization occurs and persists in normal QRS beats often seen in alternation with paced beats. The T-wave direction of normal beats is typically similar to the direction of the QRS complex during pacing, hence the term cardiac memory. The normal nonpaced beats have shown a sensitivity of 92% and a specificity of 100% for cardiac memory in the presence of T-wave inversions (TWI) in the precordial and inferior (II, III and aVF) leads with a positive T wave in aVL, a positive or isoelectric T wave in lead I, and the maximal precordial TWI being greater than the TWI of lead III, discriminating it from ischemic precordial TWI. In the latter, TWI are also seen in leads aVL and I.