Usefulness and limitations of dobutamine-atropine stress echocardiography for the diagnosis of coronary artery disease in patients with left bundle branch block. A multicentre study

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.

Recent advances in the synthesis of (99mTechnetium) based radio-pharmaceuticals

Technetium radionuclide (99mTc) has excellent extent of disintegration properties and occupies a special place in the field of nuclear medicinal chemistry and other health disciplines. Current review describes recent approaches of synthesis in detailed ways for radio-pharmaceuticals of technetium which have been developed to treat and diagnose the biotic disorders. These technetium labeled radio-pharmaceuticals have been established to apply in the field of diagnostic nuclear medicine especially for imaging of different body parts such as brain, heart, kidney, bones and so on, through single photon emission computed tomography (SPECT) that is thought to be difficult to image such organs by using common X-ray and MRI (Magnetic Resonance Imaging) techniques. This review highlights and accounts an inclusive study on the various synthetic routes of technetium labeled radio-pharmaceuticals using ligands with various donor atoms such as carbon, nitrogen, sulphur, phosphorus etc. These compounds can be utilized as next generation radio-pharmaceuticals.

[The Clinical use of Stress Echocardiography in Ischemic Heart Disease Cardiovascular Ultrasound (2017)15:7. Translation authors: Arystan A.Zh., Fettser D.V.]

Stress echocardiography is an established technique for the assessment of extent and severity of coronary artery disease. The combination of echocardiography with a physical, pharmacological or electrical stress allows detecting myocardial ischemia with an excellent accuracy. A transient worsening of regional function during stress is the hallmark of inducible ischemia. Stress echocardiography provides similar diagnostic and prognostic accuracy as radionuclide stress perfusion imaging or magnetic resonance, but at a substantially lower cost, without environmental impact, and with no biohazards for the patient and the physician. The evidence on its clinical impact has been collected over 35 years, based on solid experimental, pathophysiological, technological and clinical foundations. There is the need to implement the combination of wall motion and coronary flow reserve, assessed in the left anterior descending artery, into a single test. The improvement of technology and in imaging quality will make this approach more and more feasible. The future issues in stress echo will be the possibility of obtaining quantitative information translating the current qualitative assessment of regional wall motion into a number. The next challenge for stress echocardiography is to overcome its main weaknesses: dependence on operator expertise, the lack of outcome data (a widespread problem in clinical imaging) to document the improvement of patient outcomes. This paper summarizes the main indications for the clinical applications of stress echocardiography to ischemic heart disease.

Postsystolic index for distinguishing coronary artery disease in left bundle branch block

BACKGROUND

Left bundle branch block (LBBB) is associated with a high risk of death, particularly from ventricular tachyarrhythmia and myocardial infarction. It is difficult to clinically differentiate between ischemic and nonischemic LBBB. In this study, we investigated whether advanced echocardiographic variables, such as strain delay index (SDI) and postsystolic index (PSI), can be used to distinguish coronary artery disease (CAD) in patients with LBBB.

METHODS

Our study included 102 patients with LBBB. All patients underwent echocardiography. The left ventricular ejection fraction (LVEF), left ventricular mass, PSI, SDI, global longitudinal strain (GLS), and time-to-peak longitudinal strain were then calculated. Coronary angiography was performed, and the patients were divided into groups with significant CAD and without significant CAD.

RESULTS

Patients in the group with significant CAD were older than the patients in the group without significant CAD. The group had a higher prevalence of diabetes mellitus, hypertension, hyperlipidemia, and family history of CAD than the group without significant CAD. The group with significant CAD also had lower LVEF and GLS than the group without significant CAD. The group without significant CAD showed a direct correlation between LVEF and SDI and an inverse correlation between LVEF and PSI: P value = 0.040 and r = 0.255, and P value = 0.001 and r = -0.427, respectively. However, the group with significant CAD did not show any significant correlation between LVEF and SDI or PSI.

CONCLUSION

Strain delay index and PSI may be useful markers in distinguishing CAD in patients with LBBB and preserved LVEF.

Is exercise stress echocardiography useful in patients with suspected obstructive coronary artery disease who have resting left bundle branch block?

BACKGROUND

Current guidelines support exercise stress echocardiography (ESE) for evaluation of suspected obstructive coronary artery disease (OCAD) in ambulant patients with left bundle branch block (LBBB). Data regarding the diagnostic utility of ESE in patients with LBBB are limited.

HYPOTHESIS

We hypothesized that the diagnostic performance of ESE for the assessment of suspected OCAD is reduced in the context of LBBB.

METHODS

We studied 191 consecutive patients with resting LBBB undergoing ESE for the investigation of suspected OCAD between 2008 and 2015 at our center. The studies were categorized as inconclusive, normal, or abnormal. Patients with an abnormal response were subcategorized as regional ischemic response or globally abnormal.

RESULTS

Eighty-two patients (43%) demonstrated a normal left ventricular contractile response (LVCR) to exercise; 92 (48%) developed an abnormal LVCR to exercise, including 70 patients with globally abnormal and 22 patients with regional ischemic responses. Of the patients with abnormal responses, 62 patients had anatomic imaging, only 29 of whom had significant OCAD, conferring an overall specificity of ESE for significant OCAD of 21% and accuracy of 52%. Of patients who developed a regionally abnormal response, 89% had significant OCAD.

CONCLUSIONS

For patients with LBBB who develop a globally abnormal LVCR during ESE, the specificity of ESE for reliably excluding significant OCAD is significantly reduced. ESE appears to be a suboptimal test for the evaluation of OCAD in patients with resting LBBB, as about 50% of patients will have an abnormal response, the majority due to globally abnormal contraction where OCAD cannot be reliably diagnosed. Alternative testing should be considered for the investigation of suspected OCAD in patients with resting LBBB.

The clinical use of stress echocardiography in ischemic heart disease

Stress echocardiography is an established technique for the assessment of extent and severity of coronary artery disease. The combination of echocardiography with a physical, pharmacological or electrical stress allows to detect myocardial ischemia with an excellent accuracy. A transient worsening of regional function during stress is the hallmark of inducible ischemia. Stress echocardiography provides similar diagnostic and prognostic accuracy as radionuclide stress perfusion imaging or magnetic resonance, but at a substantially lower cost, without environmental impact, and with no biohazards for the patient and the physician.

The evidence on its clinical impact has been collected over 35 years, based on solid experimental, pathophysiological, technological and clinical foundations. There is the need to implement the combination of wall motion and coronary flow reserve, assessed in the left anterior descending artery, into a single test. The improvement of technology and in imaging quality will make this approach more and more feasible. The future issues in stress echo will be the possibility of obtaining quantitative information translating the current qualitative assessment of regional wall motion into a number. The next challenge for stress echocardiography is to overcome its main weaknesses: dependance on operator expertise, the lack of outcome data (a widesperad problem in clinical imaging) to document the improvement of patient outcomes. This paper summarizes the main indications for the clinical applications of stress echocardiography to ischemic heart disease.

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.

Patients with left bundle branch block pattern and high cardiac risk myocardial SPECT: does the current management suffice?

INTRODUCTION

Myocardial perfusion SPECT (MPS) is frequently used for cardiovascular risk stratification. The significance of MPS in patients with abnormal electrical ventricular activation is often questionable. This review assesses the value of MPS for risk stratification of patients with intrinsic left bundle branch block or that due to right ventricular apical pacing.

METHODS

We reviewed the literature by a search of the MEDLINE database (January 1980 to September 2010). The terms prognosis or prognostic value were combined with SPECT and LBBB or pacing or pacemakers. MPS was categorised as low and high risk according to the original definitions.

RESULTS

We identified 11 studies suitable for review. A low-risk MPS is associated with a low risk of cardiac events whereas high-risk MPS carries a 4.8-fold increased risk, 95% CI [3.2 - 7.2] (p < 0.0001). Despite secondary prevention and an improved medical and interventional care, these figures have hardly changed over time.

CONCLUSION AND CLINICAL IMPLICATIONS

A low-risk MPS permits a policy of watchful waiting whereas a high-risk MPS requires further analysis and treatment. The persistent high cardiac death and acute myocardial infarction rate after a high-risk MPS suggest that the current management of these patients does not suffice and needs reconsideration.

Exercise echocardiography

Exercise echocardiography has been used for 30 years. It is now considered a consolidated technique for the diagnosis and risk stratification of patients with known or suspected coronary artery disease (CAD). Of the stress echocardiography techniques, it represents the first choice for patients who are able to exercise. Given that the cost-effectiveness and safety of stress echocardiography are higher than those of other imaging techniques, its use is likely to be expanded further. Recent research has also proposed this technique for the evaluation of cardiac pathology beyond CAD. Although the role of new technology is promising, the assessment of cardiac function relies on good quality black and white harmonic images.

Right ventricular pressure dynamics and stress echocardiography in pharmacological and exercise stress testing

REASONS FOR PERFORMING STUDY

There is interest in using pharmacological stress testing (PST) as a substitute for exercise stress testing (EST) to evaluate cardiac function in horses.

OBJECTIVES

To compare the effect of PST and EST on right ventricular pressure dynamics and stress echocardiography.

METHODS

Five horses completed a PST and EST in a randomised crossover design. High fidelity pressure transducers were placed in the right ventricle. Continuous pressure signals were digitally collected and stored, and dP/dtmax, dP/dtmin and tau calculated from these measurements. ECGs were recorded continuously for 20 h. Echocardiography was performed prior to EST and PST, during and after PST, and immediately post EST. Plasma cardiac troponin I concentrations were measured pre- and 3-4 h post stress testing. For PST, 5 microg/kg bwt glycopyrrolate i.v. followed after 10 min by 5 microg/kg bwt/min dobutamine infusion over 10 min was given. EST consisted of a 2 min gallop at 110% speed required to elicit VO2max.

RESULTS

Both EST and PST resulted in a significant increase in right-ventricular dP/dtmax and dP/dtmin over baseline (P<0.05) and a significant decrease in tau compared with baseline (P<0.05). EST dP/dtmax and dP/dtmin were significantly greater than PST dP/dtmax and dP/dtmin (P<0.05) and EST tau was significantly less than PST tau (P<0.05). Two minutes post EST and 5 min post PST dP/dtmax were not significantly different, but were significantly less than end-EST and during PST. Tau was also not significantly different between post EST and post PST, but was significantly decreased end-EST compared with during PST. FS were not significantly different between PST and post EST, but during PST and post EST all FS were significantly higher than baseline. Cardiac troponin I concentrations were significantly elevated post PST and were greater than post EST. The clinical relevance of this is unknown.

CONCLUSIONS

PST had a similar, although less marked effect on the cardiac parameters related to right-ventricular pressure dynamics and a similar effect on echocardiography as exercise stress testing.

POTENTIAL RELEVANCE

PST deserves further evaluation in normal horses and those with cardiac disease, and may be complementary to EST to better identify exercise-induced cardiac dysfunction.

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.

Assessing ischemic heart disease in patients with left bundle branch block--an emerging role for multislice computed tomography

Diagnosis of left bundle branch block (LBBB) with concomitant coronary artery disease (CAD) alters the prognosis and the therapeutic management. All common non-invasive stress tests have a limited performance to identify CAD in patients with LBBB. Thus invasive coronary angiography is often needed to confirm or defer obstructive CAD. We propose a new diagnostic algorithm in evaluation of symptomatic and asymptomatic patients with LBBB.

Stress-induced QTc-interval shortening as an ancillary marker of ischemia in patients with complete left bundle branch block

BACKGROUND

In patients with left bundle branch block (LBBB), ischemia-induced repolarization changes associated with QTc-interval shortening may be recorded during coronary angioplasty. We aimed to assess whether these repolarization changes may be predictive of severe coronary artery disease in patients with LBBB.

METHODS

Fifty noninfarcted LBBB patients underwent dipyridamole stress test and coronary angiography for chest pain. To localize the site of ischemia, we considered four groups of conventional ECG leads (V1-V2-V3; V4-V5-V6; aVL-I; III-aVF-II), exploring the anteroseptal, lateral, high-lateral, and inferior left ventricular walls. ST-T changes and QTc intervals were estimated at rest and peak stress, lead by lead, in each group of leads and the fractional percentage difference between rest-stress QTc intervals ([DELTA]QTc) was calculated. A [DELTA]QTc greater than -10% was used to define significant QTc-interval shortening. Coronary stenosis of more than 70% and more than 90% were considered 'significant' and 'severe'.

RESULTS

According to dipyridamole stress test response, two groups were identified: group I (35 patients) with dipyridamole-induced ischemia and group II (15 patients) without dipyridamole-induced ischemia. The wall motion score index at peak stress (compared with resting wall motion score index) was significantly higher in group I (1.98 +/- 0.13 vs. 1.28 +/- 0.08, P < 0.0001) than in group II (1.36 +/- 0.18 vs. 1.25 +/- 0.08, P = 0.296). The patients of group I showed a significant QTc-interval shortening ([DELTA]QTc = -16.9 +/- 3.9%), whereas this did not happen in patients of group II ([DELTA]QTc = +8.8 +/- 2.4%, P < 0.0001). The patients of group I also had a more severe stenosis in the vessel related to the stress-induced dyssynergic area (I = 90.5 +/- 9.5 vs. II = 34.3 +/- 31.1%; P < 0.0001).

CONCLUSION

In patients with LBBB, stress-induced pseudonormalization pattern, associated with QTc-interval shortening, allows the identification of cardiac areas supplied by severely stenosed coronary arteries.

Multislice Computed Tomography Coronary Angiography: Risk Stratification of Patients in the Perioperative Period

Multislice computed tomography coronary angiography is emerging as a reliable noninvasive method for the assessmentofcoronaryarterydisease, coronaryanatomyand cardiac function. Improvements in computed tomography technology hold the promise of replacing the standard invasive procedure of conventional coronary angiography in selected patient groups. The ability of a six-second scan to identify flow-limiting coronary artery stenoses as well as characterising coronary atheromatous plaque components provides valuable information that can assist in refining perioperative cardiovascular risk. Multislice computed tomography's high negative predictive value and high specificity for stenoses allows it to effectively rule out coronary artery disease in patients with cardiac risk factors who have non-diagnostic or equivocal noninvasive cardiac stress tests. Other uses include evaluating patients who are symptomatic following percutaneous coronary intervention, evaluating coronary artery bypass grafts and coronary stent patency, detecting coronary stenosis prior to valve surgery and assessing coronary anatomy in patients with technically difficult arterial access. Avoiding the small but definite risks of conventional coronary angiography makes cardiac computed tomography an appealing alternative. An overview of multislice computed tomography is presented with particular attention placed on its role in the risk stratification of selected patients in the perioperative period. A risk stratification algorithm is suggested.

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.

Utility of stress echocardiography in identifying significant coronary artery disease in patients with left bundle-branch block

HYPOTHESIS

The aim of the study was to determine the utility of stress echocardiography for identification of significant coronary artery disease (CAD) in higher-risk patients with an underlying left bundle-branch block (LBBB).

METHODS

Patients with LBBB undergoing stress echocardiography were divided into 2 groups: group 1 (no history MI), group 2 (history MI). Positive stress echocardiograms were compared with the presence of >50% luminal-diameter stenosis during coronary angiography. During the follow-up (FU) period, cardiac events were determined for hard and soft endpoints.

RESULTS

Sixty consecutive patients with LBBB underwent stress echocardiography. Twenty-eight patients had a positive stress echocardiogram (20 group 1; 8 group 2). Nineteen of these patients underwent coronary angiography (14 group 1; 5 group 2). In group 1, regional wall motion abnormality (RWMA) correlated with coronary anatomy in only 5 patients, while in group 2, RWMA correlated with coronary anatomy in only 2 patients. There were 12 false positives, with echocardiographic abnormalities identified. The positive predictive values in groups 1 and 2 were 35.7% and 40%, respectively. During the FU period, there was 1 mortality, 2 MI, 2 coronary revascularizations, and 6 hospitalizations (2 chest pain, 1 CHF, 3 coronary angiography). The negative predictive value for hard endpoints was 83%.

CONCLUSION

Stress echocardiography has a poor positive predictive value to identify significant angiographic CAD in higher-risk patients with LBBB; however, the negative predictive value for hard ischemic events is similar to patients without LBBB.

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.

Left bundle-branch block artifact on single photon emission computed tomography with technetium Tc 99m (Tc-99m) agents: mechanisms and a method to decrease false-positive interpretations

Myocardial perfusion scintigraphy is a well validated noninvasive method of evaluating for significant coronary artery disease, especially in cases where electrocardiographic changes are nondiagnostic, including left bundle-branch block. However, such testing with a technetium Tc 99m agent is often confounded by left ventricular septal-based false-positive perfusion defects. These defects can be either reversible or irreversible in the septal or anteroseptal wall, problematically then, in the territory supplied by the left anterior descending coronary artery. Mechanisms explaining false-positive defects include decreased perfusion via impaired microvessel flow and normal perfusion with apparent decrease in counts in a relatively thin septum (partial-volume effect). Key findings in myocardial perfusion images in the presence of left bundle-branch block that define true positives (ischemia) are reversible perfusion defects (especially at end diastole), a concomitant apical defect, and systolic dysfunction matching the perfusion defect.

Nuclear Cardiology: Present and Future

Nuclear cardiology has made significant advances since the first reports of planar scintigraphy for the evaluation of left ventricular perfusion and function. While the current "state of the art" of gated myocardial perfusion single-photon emission computed tomographic (SPECT) imaging offers invaluable diagnostic and prognostic information for the evaluation of patients with suspected or known coronary artery disease (CAD), advances in the cellular and molecular biology of the cardiovascular system have helped to usher in a new modality in nuclear cardiology, namely, molecular imaging. In this review, we will discuss the current state of the art in nuclear cardiology, which includes SPECT and positron emission tomographic evaluation of myocardial perfusion, evaluation of left ventricular function by gated myocardial perfusion SPECT and gated blood pool SPECT, and the evaluation of myocardial viability with PET and SPECT methods. In addition, we will discuss the future of nuclear cardiology and the role that molecular imaging will play in the early detection of CAD at the level of the vulnerable plaque, the evaluation of cardiac remodeling, and monitoring of important new therapies including gene therapy and stem cell therapy.

Accuracy of non-invasive techniques for diagnosis of coronary artery disease and prediction of cardiac events in patients with left bundle branch block: a meta-analysis

PURPOSE

Non-invasive evaluation of coronary artery disease (CAD) in patients with left bundle branch block (LBBB) has limitations inherent to different tests, and the relative merits of these tests are unclear. This meta-analysis assessed the accuracy of the frequently used non-invasive techniques, including exercise electrocardiography (ECG), myocardial perfusion imaging (MPI) and stress echocardiography (SE), for detection of CAD and prediction of cardiac events in patients with LBBB.

METHODS

A review was conducted of all reports on detection of CAD and prediction of cardiac events in patients with LBBB (published between January 1970 and December 2004), and revealed 55 diagnostic and nine prognostic reports with sufficient details to calculate test accuracy. Weighted (by sample size) sensitivity and specificity were calculated. Summary relative risk ratios (95% confidence intervals) were calculated.

RESULTS

Overall sensitivity was higher for exercise ECG and (quantitatively analysed) MPI than for SE (83.4% and 88.5% versus 74.6% respectively, p<0.0001). SE had a higher specificity (88.7%) than MPI (41.2%) and exercise ECG (60.1%) (p<0.0001). Based on analysis of eight reports, the relative risk of cardiac death or myocardial infarction in patients with an abnormal SE and MPI was elevated more than sevenfold, but it did not differ by imaging modality (p=0.9).

CONCLUSION

Meta-analysis of non-invasive CAD assessment in LBBB patients revealed that exercise ECG and MPI had the highest sensitivity, while SE had the highest specificity. The prognostic accuracy of MPI and SE appeared similar.

The use of stress echocardiography for prognostication in coronary artery disease: an overview

PURPOSE OF REVIEW

Stress echocardiography has a high accuracy for the detection of coronary artery disease. Additionally, it provides clinically useful prognostic information, such as resting left ventricular function, myocardial viability, stress-induced ischemia, vascular extent of wall motion abnormalities, and changes in end-systolic volume and ejection fraction with stress.

RECENT DEVELOPMENTS

The timing, extent, and severity of the stress-induced wall motion abnormalities are important determinants of long-term prognosis. Previous studies have shown the efficacy of stress echocardiography in predicting long-term cardiac events in mixed patient groups and the value of this test in selected patient subsets.

SUMMARY

This review attempts to define the role of stress echocardiography for prognostication in coronary artery disease, pointing out the ability of this technique to identify low-risk and high-risk subsets among patients with known or suspected coronary artery disease and thus guide patient management decisions.

Decreased septal wall thickening in patients with left bundle branch block

OBJECTIVES

Septal wall motion abnormalities are frequently observed in patients with left bundle branch block (LBBB). However, septal wall thickening in LBBB patients has not been thoroughly evaluated.

METHODS AND RESULTS

To investigate the relationship between septal wall motion and wall thickening, we studied 31 normal control subjects, 24 LBBB patients with normal wall motion (LBBB-NWM), and 24 LBBB patients with septal dyssynchrony (LBBB-SDS), all with a low likelihood (<15%) of coronary artery disease. The septal and lateral quadrants of the left ventricle were analyzed in stress 8-frame gated technetium 99m sestamibi tomograms. The percent wall thickening was calculated by use of a 25-segment polar map with the p-FAST software program by two independent methods: the regional count density increase from end diastole to end systole (CD method) and the geometric increase in the distance between the 50% thresholded endocardial and epicardial borders from end diastole to end systole (GD method). In addition, the ratio of septal/lateral percent wall thickening was calculated. The relative septal wall thickening in the entire LBBB population was decreased as compared with the normal control subjects (0.35 +/- 0.37 vs 0.81 +/- 0.17, P <.001). Decreased wall thickening was observed in not only LBBB-SDS patients but also to a lesser degree in LBBB-NWM patients (0.12 +/- 0.35, P <.001; 0.57 +/- 0.24, P =.005, respectively). This abnormality was most apparent when the CD method was used.

CONCLUSIONS

Septal wall thickening is decreased in patients with LBBB even with normal wall motion. LBBB per se may compromise septal wall thickening, and dyssynchronous wall motion results in further deterioration of wall thickening.

Differentiation of ischemic from nonischemic cardiomyopathy during dobutamine stress by left ventricular long-axis function: additional effect of left bundle-branch block

BACKGROUND

Resting regional wall-motion abnormalities do not reliably distinguish ischemic from nonischemic cardiomyopathy. Dobutamine stress echocardiography with use of the wall-motion score index (WMSI) identifies coronary artery disease (CAD) in dilated cardiomyopathy (DCM), but the technique is subjective and further complicated by left bundle-branch block (LBBB). Long-axis motion is sensitive to ischemia and can be assessed quantitatively. We aimed to compare long-axis function with WMSI for detecting CAD in DCM with or without LBBB.

METHODS AND RESULTS

Seventy-three patients with DCM, 48 with CAD (16 with LBBB), and 25 without CAD (10 with LBBB) were studied. Long-axis M-mode, pulsed-wave tissue Doppler echograms (lateral, septal, and posterior walls), and WMSI were assessed at rest and at peak dobutamine stress. Failure to increase systolic amplitude (total amplitude minus postejection shortening) by 2 mm or early diastolic velocity by 1.1 cm/s was the best discriminator for CAD (systolic amplitude, sensitivity 85%, specificity 86%; lengthening velocity, 71% and 94%, respectively; P=NS). Both had greater predictive accuracy than did WMSI (sensitivity 67%, specificity 76%; P<0.001). The predictive accuracy of changes in septal long-axis function was similar to those of average long-axis function (systolic amplitude cutoff=1.5 mm, lengthening velocity cutoff=1.5 cm/s). However in LBBB, systolic amplitude proved to be the only significant discriminator for CAD, with sensitivity and specificity reaching 94% and 100%, respectively (P<0.01 versus early diastolic lengthening velocity).

CONCLUSIONS

Quantified stress long-axis function identifies CAD in DCM with greater sensitivity and specificity than does standard WMSI, particularly in the presence of LBBB.

Prognostic implications of intraventricular conduction defects in patients undergoing stress echocardiography for suspected coronary artery disease

PURPOSE

To investigate the prognostic implications of conduction defects in subjects without proven coronary artery disease who had been referred for stress echocardiography.

METHODS

The study sample consisted of 1230 patients (574 men and 656 women; mean [+/- SD] age, 63 +/- 10 years) who underwent stress echocardiography with dipyridamole (n = 780) or dobutamine (n = 450) to evaluate suspected coronary artery disease. A summary wall motion score (on a 1 to 4 scale) was calculated. Patients were followed for a mean of 41 +/- 27 months; mortality was the only endpoint.

RESULTS

Four hundred and twenty patients (34%) had intraventricular conduction defects on a resting electrocardiogram (173 with complete left bundle branch block, 98 with isolated right bundle branch block, 43 with right bundle branch block with left anterior hemiblock, and 106 with left anterior hemiblock). Ischemia at stress echo (new or worsening of preexisting wall motion abnormality) was found in 250 patients (20%). There were 56 deaths during follow-up; 138 patients underwent revascularization and were censored. Multivariate predictors of mortality were resting wall motion score index (hazard ratio [HR] = 6.0 per unit increase; 95% confidence interval [CI]: 2.3 to 16; P <0.0001), ischemia at stress echo (HR = 3.9; 95% CI: 2.2 to 6.7; P <0.0001), age >65 years (HR = 3.2; 95% CI: 1.7 to 5.9; P <0.0001), hypertension (HR = 1.8; 95% CI: 1.1 to 3.2; P = 0.03), and right bundle branch block with left anterior hemiblock (HR = 3.7; 95% CI: 1.8 to 7.5; P <0.0001). The other three forms of intraventricular conduction defects (left bundle branch block, isolated complete right bundle branch block, and left anterior hemiblock) were not associated with mortality in multivariate analyses, or among the 980 patients who did not have ischemia.

CONCLUSION

Right bundle branch block with left anterior hemiblock is an independent predictor of mortality in patients with suspected coronary artery disease undergoing stress echocardiography, whereas isolated right bundle branch block is associated with outcomes similar to those observed in patients with no conduction defects.

Clinical assessment in ischaemic cardiomyopathy

Despite the trend of decreasing death rates attributable to ischaemic heart disease and stroke, the prevalence of heart failure and the resultant death rates in the United States have almost tripled between 1974 and 1994 [1]. Coronary artery disease is the commonest cause of heart failure in developed countries, accounting for up to 60% of cases. Advances in medical therapy, particularly the use of angiotensin-converting enzyme inhibitors and beta-blockers, have served to reduce morbidity and mortality in patients with left ventricular (LV) dysfunction due to coronary artery disease [2-5]. However, these improvements have been modest, and despite these therapies, patients with severe ischaemic cardiomyopathy continue to have a high mortality when treated medically. It is increasingly clear that the impaired LV function in these patients is not always an irreversible process. Traditionally, these observations have been made following demonstrable improvements in systolic function after coronary revascularization procedures. Diagnostic testing to evaluate the presence and extent of viable myocardium has therefore become an important component of the clinical assessment of patients with chronic coronary artery disease and LV dysfunction.

Dipyridamole stress echocardiography vs dipyridamole sestamibi scintigraphy for diagnosing coronary artery disease in left bundle-branch block

STUDY OBJECTIVES

To evaluate dipyridamole stress echocardiography (DSE) for predicting coronary artery diseases (CADs) in patients with complete left bundle-branch block (LBBB).

DESIGN

Comparison of DSE and dipyridamole sestamibi myocardial perfusion scintigraphy (sestamibi).

SETTING

Tertiary-care cardiac referral center.

PATIENTS

Fifty-four consecutive patients (26 men; mean [+/- SD] age, 59 +/- 7 years) with complete LBBB (14 patients with left ventricular [LV] dilatation) and intermediate probability of CAD.

METHODS

Simultaneous single photon emission CT scan (20 mCi technetium Tc 99m stress/rest sestamibi) and echocardiography (second harmonic imaging) during a two-step (0.56 to 0.84 mg/kg) dipyridamole infusion protocol. Two sestamibi readings were performed. The first reading considered only those studies with reversible defects (sestamibi-1) to be positive. The second reading considered those studies with any defect (sestamibi-2) to be positive. CAD was defined as a >or= 50% reduction in diameter in at least one major vessel seen on coronary angiography.

RESULTS

CAD was present in 17 patients (31.5%). The global predictive accuracy for CAD was significantly higher for DSE (87.0%) and sestamibi-1 (79.6%) than for sestamibi-2 (57.4%) [p < 0.01 vs DSE; p < 0.05 vs sestamibi-1]. No significant differences in sensitivity were present, but specificity was significantly higher for DSE (94.6%) and sestamibi-1 (81.1%) than for sestamibi-2 (43.2%; p < 0.01 vs both the other two tests). Of 14 patients with LV dilatation, 26.8% were falsely positive for CAD (in some cases for posterior defects) as determined by sestamibi-1 and 64.3% were falsely positive for CAD by sestamibi-2 vs none by DSE.

CONCLUSIONS

DSE is at least as accurate as dipyridamole sestamibi scintigraphy for predicting CAD in patients with complete LBBB and tends to be more specific in those patients with underlying LV dilatation.

Prognostic value of pharmacologic stress echocardiography in patients with left bundle branch block

PURPOSE

Although coronary artery disease is a frequent cause of left bundle branch block, the prognostic value of myocardial ischemia in patients with this conduction abnormality has not been defined. We investigated the value of pharmacologic stress echocardiography in risk stratification of patients with left bundle branch block.

PATIENTS AND METHODS

Three hundred eighty-seven patients [230 men and 157 women, mean (+/- SD) age, 64 +/- 9 years] with complete left bundle branch block on the resting electrocardiogram underwent dobutamine (n = 217) or dipyridamole (n = 170) stress echocardiography to evaluate suspected or known coronary artery disease. A summary wall motion score (on a one to four scale) was calculated. The primary end points were cardiac death and nonfatal myocardial infarction.

RESULTS

A positive echocardiographic result (evidence of ischemia) was detected in 109 (28%) patients. During a mean follow-up of 29 +/- 26 months, there were 21 cardiac deaths and 20 myocardial infarctions, 63 patients underwent coronary revascularization, and 1 patient received a heart transplant. In a multivariate analysis, four clinical and echocardiographic variables were associated with increased risk of cardiac death: resting wall motion score index [hazard ratio (HR) = 7.5 per unit; 95% confidence interval (CI), 2.8 to 20; P = 0.001], previous myocardial infarction (HR = 2.9; 95% CI, 1.1 to 7.3; P = 0.02), diabetes (HR = 2.7; 95% CI, 1.1 to 6.6; P = 0.03), and the change in wall motion score index from rest to peak stress (HR = 3.0 per unit; 95% CI, 1.0 to 8.6; P = 0.04). The 5-year survival was 77% in the ischemic group and 92% in the nonischemic group (P = 0.02). Four variables were associated with increased risk of cardiac death or infarction: previous myocardial infarction (HR = 3.4; 95% CI, 1.7 to 6.8; P = 0.0005), diabetes (HR = 2.4; 95% CI, 1.2 to 4.6; P = 0.01), resting wall motion score index (HR = 2.2 per unit; 95% CI, 1.1 to 4.1; P = 0.02), and positive echocardiographic result (HR = 2.2; 95% CI, 1.1 to 4.5; P = 0.03). The 5-year infarction-free survival was 60% in the ischemic group and 87% in the nonischemic group (P < 0.0001). Stress echocardiography significantly improved risk stratification in patients without previous myocardial infarction (P = 0.0001), but not in those with previous myocardial infarction (P = 0.08). In particular, it provided additional value over clinical and resting echocardiographic findings in predicting cardiac events among patients without previous infarction.

CONCLUSIONS

Myocardial ischemia during pharmacologic stress echocardiography is a strong prognostic predictor in patients with left bundle branch block, particularly in those without previous myocardial infarction.

Stress echocardiography in the diagnosis of coronary artery disease

Stress echocardiography (SE) is currently a widely accepted method for the diagnostic and prognostic assessment of coronary artery disease. This article reviews new concepts in SE, such as new stress techniques, new methods of endocardial border detection, strain, tissue Doppler velocities, and others. Although some of these techniques are in their infancy, we believe that they will become widely accepted.