Adenosine thallium-201 is superior to exercise thallium-201 for detecting coronary artery disease in patients with left bundle branch block

Prognostic value of regadenoson stress myocardial perfusion imaging in patients with left bundle branch block or ventricular paced rhythm

BACKGROUND

Vasodilator stress myocardial perfusion imaging (MPI) is the provocative test of choice in patients with left bundle branch block (LBBB) or ventricular paced (V-paced) rhythm. The prognostic value of regadenoson SPECT myocardial perfusion imaging (MPI) in these patients has not been studied.

METHODS AND RESULTS

We conducted a retrospective cohort study of 562 patients [mean age, 69 ± 11 years; men, 53.3%] with LBBB (50.7%) or V-paced rhythm (49.3%) who underwent regadenoson stress SPECT-MPI. There were 321 (57.1%) subjects with abnormal MPI and 192 (34.2%) with myocardial ischemia. During a mean follow-up of 2.5 ± 1.9 years, 39 (6.9%) patients had a major adverse cardiac event (MACE), defined as cardiac death or myocardial infarction. The annualized MACE rate in patients with normal MPI was 0.9% (LBBB, 0.8%; V-paced, 1.0%). There was a significant stepwise increase in MACE rates with increasing burdens of perfusion abnormality (P < 0.001) and myocardial ischemia (P = 0.001). Increased risk with abnormal MPI [adjusted hazard ratio, 4.26; P = 0.001] and myocardial ischemia [adjusted hazard ratio, 2.70; P = 0.003] was independent of and incremental to important clinical covariates. Abnormal MPI and myocardial ischemia predicted MACE similarly in both LBBB and V-paced subgroups (interaction P values > 0.05).

CONCLUSION

In patients with LBBB and V-paced rhythm, regadenoson stress SPECT-MPI provides independent and incremental prognostic value in predicting adverse cardiac events.

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.

Severe myocardial ischemia in a patient with diabetes mellitus and left bundle branch block

We present the case of a 69-year-old woman with diabetes mellitus, left bundle branch block, and obesity who develops cardiogenic shock after undergoing myocardial perfusion imaging and diagnostic left heart catheterization, but prior to coronary revascularization. This case highlights the risk of cardiac decompensation awaiting surgery in patients with multivessel coronary artery disease. It also emphasizes the subtleties involved in imaging patients with diabetes mellitus and left bundle branch block, as well as the risk of developing complete heart block in the setting of ischemia with underlying conduction disease.

Incidence of atrioventricular block with vasodilator stress SPECT: A meta-analysis

BACKGROUND

Adenosine or regadenoson are often used with pharmacologic stress testing. Adenosine may trigger atrioventricular block (AVB). Despite its higher selectivity, regadenoson has also been associated with AVB. We studied the incidence of de novo AVB with these agents.

METHODS

A comprehensive search of SCOPUS was performed from inception to March 2016. Studies of at least 10 patients, using adenosine and/or regadenoson with SPECT-MPI, reporting rates of AVB were selected for further review.

RESULTS

Thirty four studies were pooled including 22,957 patients. Adenosine was used in 21 studies and regadenoson in 15. Both were administered in two studies. The estimated incidence of overall and high-grade AVB was 3.81% (95% CI 1.99%-6.19%) and 1.93% (95% CI 0.77%-3.59%), respectively. The incidence of AVB (8.58%; 95% CI 5.55%-12.21% vs 0.30%; 95% CI 0.04%-0.82%, respectively, P < .001) and high-grade AVB (5.21%; 95% CI 2.81%-8.30% vs 0.05%; 95% CI < .001%-0.19% respectively, P < .001) were higher with adenosine compared to regadenoson.

CONCLUSION

AVB is seen in about 4% of patients undergoing vasodilator stress test. Both overall and high-grade AVB are more frequent with adenosine compared to regadenoson.

Differential effect of regadenoson versus dipyridamole on heart rate in patients with left bundle branch block: How does it affect the results of pharmacological nuclear stress testing?

Background

Myocardial perfusion imaging (MPI) stress test is performed either using exercise as a stress modality or through the use of pharmacological vasodilator agents in those who cannot exercise. Regadenoson and dipyridamole are some of the most common vasodilator agents used. We aim to study the effect of these agents on the heart rate and the imaging results.

Methods

This was a retrospective study which included 187 patients with left bundle branch block. Patients received either dipyridamole or regadenoson during the myocardial perfusion imaging stress test. Charts were reviewed, and patient characteristics were recorded, as well as baseline heart rate, peak heart rate during stress, and angiographic data if available.

Results

Regadenoson increased peak, absolute and relative heart rates significantly more compared to dipyridamole. The peak heart rate for Regadenoson was 94.1 ± 17.36 and for dipyridamole it was 85.38 ± 16.48 BPM (P < 0.001). The relative and absolute heart rate increase in the regadenoson group were 40.75 ± 23.01% and 26.06 ± 13.44 BPM, respectively. The relative and absolute heart rate increase in the dipyridamole group were 24.61 ± 18.25% and 16.23 ± 10.97 BPM. The frequency of reversible septal defects was similar in both groups (54% for Regadenoson vs. 63% for Dipyridamole; P = 0.24).

Conclusions

There is a statistically significant increase in heart rate with the use of regadenoson for MPI compared to dipyridamole. However, the number of septal perfusion defects was similar between the two groups. The effect of this increase in heart rate, while statistically significant, is likely of no clinical significance.

Comparison of the current reasons for undergoing pharmacologic stress during echocardiographic and radionuclide stress testing

BACKGROUND

Symptom-limited exercise is the preferred method of cardiac stress testing, but pharmacologic testing has been increasing over time. The exact reasons for pharmacologic stress testing have not been rigorously categorized. Thus, we systematically explored the reasons for pharmacologic stress testing in patients referred for cardiac stress imaging.

METHODS

We studied consecutive patients referred for stress imaging [stress echocardiography or radionuclide myocardial perfusion imaging (MPI)] at Mount Sinai St Luke's hospital between August 2013 and April 2014. Baseline information was obtained using a standardized questionnaire and a trained physician triaged the patient for symptom-limited exercise stress testing or pharmacologic stress testing.

RESULTS

In total, 551(48%) of our entire stress cohort underwent cardiac imaging following initial exercise testing and 589 (52%) underwent imaging with initial pharmacologic stress testing. Deconditioning and inability to walk (primarily due to musculoskeletal conditions) constituted the top two reasons for performing pharmacologic stress, followed by frailty, left bundle branch block (for MPI), resting wall motion abnormality (for echocardiography), and failed exercise attempts. The reasons for performing pharmacologic stress testing were similar in the MPI and echocardiography patients, despite a much higher level of disease acuity in the MPI group.

CONCLUSIONS

We have applied a systematic approach for categorizing the reasons for pharmacologic stress. These reasons are heterogeneous, but similar across MPI and echo stress laboratories.

Myocardial blood flow assessment with 82rubidium-PET imaging in patients with left bundle branch block

OBJECTIVES

Perfusion abnormalities are frequently seen in Single Photon Emission Computed Tomography (SPECT) when a left bundle branch block is present. A few studies have shown decreased coronary flow reserve in the left anterior descending territory, regardless of the presence of coronary artery disease.

OBJECTIVE

We sought to investigate rubidium-82 (82Rb) positron emission tomography imaging in the assessment of myocardial blood flow and coronary flow reserve in patients with left bundle branch block.

METHODS

Thirty-eight patients with left bundle branch block (GI), median age 63.5 years, 22 (58%) female, 12 with coronary artery disease (≥70%; GI-A) and 26 with no evidence of significant coronary artery disease (GI-B), underwent rest-dipyridamole stress 82Rb-positron emission tomography with absolute quantitative flow measurements using Cedars-Sinai software (mL/min/g). The relative myocardial perfusion and left ventricular ejection fraction were assessed in 17 segments. These parameters were compared with those obtained from 30 patients with normal 82Rb-positron emission tomography studies and without left bundle branch block (GII).

RESULTS

Stress myocardial blood flow and coronary flow reserve were significantly lower in GI than in GII (p<0.05). The comparison of coronary flow reserve between GI-A and GI-B showed that it was different from the global coronary flow reserve (p<0.05) and the stress flow was significantly lower in the anterior than in the septal wall for both groups. Perfusion abnormalities were more prevalent in GI-A (p=0.06) and the left ventricular ejection fraction was not different between GI-A and GI-B, whereas it was lower in GI than in GII (p<0.001).

CONCLUSION

The data confirm that patients with left bundle branch block had decreased myocardial blood flow and coronary flow reserve and coronary flow reserve assessed by 82Rb-positron emission tomography imaging may be useful in identifying coronary artery disease in patients with left bundle branch block.

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.

Is regadenoson an appropriate stressor for MPI in patients with left bundle branch block or pacemakers?

BACKGROUND

Patients with LBBB or ventricular pacemaker undergoing MPI are at risk for false positive MPI results in the setting of an elevated heart rate (HR) with exercise or dobutamine stress. The areas of increased apparent ischemia are typically the LAD and septal territories.

METHODS

In a subanalysis of the ADVANCE MPI 1 and 2 studies, perfusion on an initial adenosine and a second MPI study with regadenoson or adenosine was compared by visual and quantitative analysis. Among 2,015 patients, 64 had LBBB and 93 had pacemakers. The hemodynamic response during the second scan was compared in those with and without LBBB and PM.

RESULTS

Following regadenoson, peak HR in the LBBB group increased by a mean of 25.4 compared to 15.3 bpm following adenosine (P = .0083). In the pacemaker group HR was blunted, 11.8 and 8.1 following regadenoson and adenosine, respectively (P = .1262). However, the visually assessed summed difference score and the quantitatively assessed extent of ischemia for the LAD and septal territories and the entire LV did not differ between the initial adenosine and subsequent regadenoson scans.

CONCLUSIONS

The significant increase in HR observed with regadenoson compared to adenosine did not translate into greater perfusion defects in the LAD or septal territories in patients undergoing regadenoson stress.

[Myocardial perfusion scintigraphy - short form of the German guideline]

This guideline is a short summary of the guideline for myocardial perfusion scintigraphy published by the Association of the Scientific Medical Societies in Ger-many (AWMF). The purpose of this guideline is to provide practical assistance for indication and examination procedures as well as image analysis and to present the state-of-the-art of myocardial-perfusion-scintigraphy. After a short introduction on the fundamentals of imaging, precise and detailed information is given on the indications, patient preparation, stress testing, radiopharmaceuticals, examination protocols and techniques, radiation exposure, data reconstruction as well as information on visual and quantitative image analysis and interpretation. In addition possible pitfalls, artefacts and key elements of reporting are described.

Nurse-led pharmacological stress testing: an overview

Myocardial perfusion imaging (MPI) is a noninvasive diagnostic tool that can provide valuable information on coronary blood flow at rest and during stress. Dynamic exercise is the stress technique of choice with patients who can achieve an acceptable workload; for those unable to do so, pharmacological stress testing with adenosine or dobutamine can be used. Nurses trained in ECG interpretation and advanced resuscitation skills are increasingly involved in supervising pharmacological stress tests. This article provides an overview of nurse-led pharmacological stress testing.

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.

Transthoracic Doppler echocardiographic coronary flow imaging in identification of left anterior descending coronary artery stenosis in patients with left bundle branch block

BACKGROUND

Conventional noninvasive methods have well-known limitations for the detection of coronary artery disease (CAD) in patients with left bundle branch block (LBBB). However, advancements in Doppler echocardiography permit transthoracic imaging of coronary flow velocities (CFV) and measurement of coronary flow reserve (CFR). Our aim was to evaluate the diagnostic value of transthoracic CFR measurements for detection of significant left anterior descending (LAD) stenosis in patients with LBBB and compare it to that of myocardial perfusion scintigraphy (MPS).

METHODS

Simultaneous transthoracic CFR measurements and MPS were analyzed in 44 consecutive patients with suspected CAD and permanent LBBB. Typical diastolic predominant phasic CFV Doppler spectra of distal LAD were obtained at rest and during a two-step (0.56-0.84 mg/kg) dipyridamole infusion protocol. CFR was defined as the ratio of peak hyperemic velocities to the baseline values. A reversible perfusion defect at LAD territory was accepted as a positive scintigraphy finding for significant LAD stenosis. A coronary angiography was performed within 5 days of the CFR studies.

RESULTS

The hyperemic diastolic peak velocity (44 +/- 9 cm/sec vs 62 +/- 2 cm/sec; P=0.01) and diastolic CFR (1.38 +/- 0.17 vs 1.93 +/- 0.3; P=0.001) were significantly lower in patients with LAD stenosis compared to those without LAD stenosis. The diastolic CFR values of <1.6 yielded a sensitivity of 100% and a specificity of 94% in the identification of significant LAD stenosis. In comparison, MPS detected LAD stenosis with a sensitivity of 100% and a specificity of 29%.

CONCLUSIONS

CFR measurement by transthoracic Doppler echocardiography is an accurate method that may improve noninvasive identification of LAD stenosis in patients with LBBB.

Tissue Velocity Imaging with Dobutamine Stress Echocardiography–A Quantitative Technique for Identification of Coronary Artery Disease in Patients with Left Bundle Branch Block

BACKGROUND

Patients with left bundle branch block (LBBB) exhibit abnormal septal motion that may limit the interpretation of stress echocardiograms and persuade the results of myocardial scintigraphy.

OBJECTIVES

We sought to analyze whether the use of tissue velocity imaging during graded dobutamine infusion is useful to identify and predict coronary artery disease (CAD) in patients with complete LBBB.

METHODS

In all, 62 patients with LBBB (mean age 62 years, 34 men) with suggested CAD underwent dobutamine stress-tissue Doppler echocardiography within 6 weeks before coronary arteriography. Dobutamine infusion started at 5 micro/kg/min and increased up to 40 micro/kg/min with additional atropine during submaximal heart rate responses. In addition to wall-motion analysis, pulsed wave tissue Doppler sampling of mitral annulus at 5 corners was performed at rest in the apical 4-chamber plus aorta and 2-chamber apical views. The measurements were repeated at low dose (10-15 micro/kg/min) and at peak stress. Tissue Doppler echocardiography measurements included early peak systolic velocity (PSV), postsystolic shortening (PSS) velocity, peak early diastolic velocity (Ve), and peak late diastolic velocity. The results were compared with 20 healthy subjects as a control group. Patients were classified into two groups according to angiographic results: LBBB with CAD (n = 32) and LBBB without CAD (n = 30).

RESULTS

There was no significant difference between LBBB groups in global wall-motion score index at rest; the delta changes in each group were almost similar during peak stress test (P > .05). In the LBBB with CAD group, PSV increased during peak stress to a smaller extent (6.3 +/- 1.1-7.2 +/- 2.0 cm/s, approximately 24% P < .03) than in non-CAD group (6.8 +/- 1.0-9.6 +/- 2.7 cm/s, approximately 46% P < .01). Similarly, Ve increased to a lesser extent in CAD group (deltaVe 1.6 +/- 1.7 vs 2.8 +/- 1.7 cm/s, approximately 25% vs 42% P < .0001). There were no significant difference in delta late diastolic velocity between LBBB and control groups or between each of them. PSS could be recorded at rest in 24 of 32 patients (75%) in CAD group and 17 of 30 patients (57%) in non-CAD group. In LBBB with CAD group, PSS was developed and significantly augmented from 4.7 +/- 3.1 to 6.3 +/- 3.4 cm/s (P < .001) during stress. Increment less than 2.5 cm/s in PSV and Ve during peak stress identified CAD with 88% sensitivity (for each) and 90% and 87% specificity, respectively. The cut-off values of PSS velocity greater than 4 cm/s at peak stress have strong diagnostic power for prediction of obstructive CAD in patients with LBBB (82% accuracy).

CONCLUSION

Tissue Doppler echocardiography with dobutamine stress allows a diagnostic benefit in the detection of CAD in patients with LBBB. The magnitude of change of PSV and Ve in addition to PSS are quantitative parameters to identify CAD in patients with LBBB where subjective wall-motion analysis failed.

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

OBJECTIVE

The non-invasive assessment of coronary artery disease (CAD) in patients with left bundle branch block (LBBB) is troublesome. In this study, we investigated the diagnostic accuracy of myocardial contrast echocardiography (MCE) with adenosine to detect CAD in asymptomatic patients with LBBB, and we compared it with single photon emission computed tomography (SPECT) with adenosine.

METHODS

Forty-seven patients with LBBB, and no previously documented CAD, initially underwent SPECT imaging and 1-3 days later MCE. Coronary arteriography was performed within 1 week from the latter procedure.

RESULTS

The overall sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, and kappa index of concordance of SPECT were 73%, 72%, 44%, 90%, 72%, and 0.37+/-0.13, respectively, whereas those of MCE were 91%, 92%, 77%, 97%, 92%, and 0.77+/-0.1, respectively (p<0.05 for all comparisons). Significant CAD was present in 11 patients (23%). Left anterior descending coronary artery was involved in 8 patients, left circumflex artery in 2 patients, and right coronary artery in 4 patients. Concerning the left anterior descending artery disease detection, SPECT had a sensitivity of 75%, a specificity of 79%, a positive predictive value of 43%, a negative predictive value of 94%, and a diagnostic accuracy of 79%. The respective values of MCE were 100% for all of the above variables.

CONCLUSIONS

MCE with adenosine has a higher global diagnostic accuracy compared to SPECT for the detection of CAD in patients with LBBB, mainly due to the poor specificity of SPECT concerning perfusion defects detection in the left anterior descending artery territory.

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.

Left Bundle Branch Block Disturbs Left Anterior Descending Coronary Artery Flow: Study Using Transthoracic Doppler Echocardiography

BACKGROUND

This study was performed to evaluate the influence of left bundle branch block (LBBB) on left anterior descending coronary artery (LAD) flow.

METHODS

We divided 89 subjects (34 males and 55 females, mean age 64 +/- 14 years) into an LBBB group (n = 40), a right ventricular (RV) pacing group (n = 26), and a control group (n = 23). All of the patients were examined with surface electrocardiography (ECG) and underwent transthoracic Doppler echocardiography (TTE) to measure QRS duration on the ECG, left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV), and left ventricular end-systolic volume (LVESV). Coronary flow velocity was measured in the distal LAD with TTE, and the percentage of diastolic flow duration (%DD) was expressed as the percentage of diastolic duration of coronary artery flow divided by the R-R interval.

RESULTS

The %DD of the LAD was significantly shorter in the LBBB group (40.4% +/- 12.4%) with LVEF < 50% than in the RV pacing group (60.3% +/- 7.3%) and the control group (59.3% +/- 7.6%) (P < .01 vs the control and RV pacing groups), and it was also significantly shorter in the LBBB group (49.3% +/- 10.5%) with LVEF > or = 50% than in the control and RV pacing groups (P < .01 vs the control and RV pacing groups). In the LBBB group, the %DD of the LAD had a positive correlation with LVEF (P < .05; r = .50), a negative correlation with LVEDV (P < .05; r = -.57), and a negative correlation with QRS duration (P < .05; r = -.41).

CONCLUSIONS

Unlike RV pacing, LBBB itself can disturb the coronary perfusion of the LAD through shortening of the diastolic flow duration. Furthermore, systolic dysfunction potentiates the shortening effect of diastolic flow duration by LBBB. Whether left ventricular systolic dysfunction is the result of the coronary flow disturbance by LBBB or vice versa merits further investigation.

The prognostic value of pharmacologic stress myocardial perfusion imaging in patients with permanent pacemakers

BACKGROUND

The aim of this study is to assess the prognostic value of pharmacologic stress (adenosine or dipyridamole) myocardial perfusion imaging in patients with permanent electronic ventricular pacemakers.

METHODS AND RESULTS

Between October 1986 and December 1995, 93 patients with pacemakers underwent pharmacologic stress testing with myocardial perfusion single photon emission computed tomography imaging. Follow-up information on 91 patients (98%) was obtained. Mean follow-up was 5.6 +/- 2.4 years. Previously published clinical and image variables were analyzed for their prognostic significance with regard to cardiac death, cardiac death/nonfatal myocardial infarction, and cardiac death/nonfatal myocardial infarction/late revascularization. The presence of a high-risk scan was a significant predictor of subsequent cardiac death by both univariate (chi 2 = 9.4, P < .001) and multivariate analysis (chi 2 = 6.5, P = .01) after adjustment for clinical score. Clinical score was not a significant predictor of cardiac death.

CONCLUSION

This study demonstrates that pharmacologic stress myocardial perfusion imaging provides significant prognostic information in patients with permanent pacemakers. In this population, pharmacologic stress myocardial perfusion imaging can differentiate patients at high risk of a subsequent cardiac event from those at low risk. These results support the American College of Cardiology/American Heart Association guideline recommendations for pharmacologic stress perfusion imaging in patients with permanent pacemakers.

Technetium-99m-Sestamibi SPECT myocardial perfusion imaging in patients with complete left bundle branch block

BACKGROUND

Diagnosis of coronary artery disease (CAD) in patients with left bundle branch block (LBBB) is considered a challenge in cardiology due to low accuracy of noninvasive methods such as basal and exercise stress test. Recently, myocardial perfusion imaging showed attainment of higher sensitivity and specificity. Scintigraphy with thallium-201 has been widely used in these patients. Few have used technetium-99m-Sestamibi and single photon emission computed tomography (SPECT). The aim of the study was to assess the diagnostic value of Tc-99m Sestamibi SPECT myocardial perfusion imaging in patients with complete LBBB.

METHODS

We studied 57 consecutive patients with complete LBBB using Tc-99m-Sestamibi SPECT and treadmill or dipyridamole stress to evaluate CAD. Eighteen patients also underwent coronary angiography. Perfusion defects were classified as fixed or reversible.

RESULTS

Prevalence of resting perfusion abnormalities in anterior, septal, and apical regions was 51, 56, and 19%, respectively. Sensitivity for detecting >50% left anterior descending artery (LAD) stenosis was 67 and 56% for anterior or septal defects, and 56% for specificity. Apical perfusion abnormality showed 21% sensitivity and 89% specificity. Among six patients with reversibility and who underwent coronary angiography, all had >50% LAD stenosis.

CONCLUSIONS

With Tc-99m-MIBI SPECT imaging, prevalence of anteroseptal perfusion abnormalities was >50% in patients with LBBB. The test has moderate sensitivity and specificity for LAD disease. Absence of apical defect is specific for excluding LAD disease. Reversible changes in anteroseptal wall should be considered as an indicator of ischemia in this territory.

The usefulness of adenosine 99mTc tetrofosmin SPECT for the diagnosis of left anterior descending coronary artery disease in patients with chest pain and left bundle branch block

OBJECTIVES

The aim of this study was to assess the usefulness of 99mTc tetrofosmin single photon emission computed tomography (SPECT) for the diagnosis of left anterior descending (LAD) coronary artery disease in 60 subjects with left bundle branch block (LBBB) admitted for chest pain.

METHODS AND RESULTS

Adenosine 99mTc tetrofosmin SPECT, transthoracic echocardiogram and coronary angiography were performed, by protocol, in 60 non-infarcted consecutive patients. The mean left ventricular ejection fraction (LVEF) was 41.6 +/- 10.8%. A significant angiographic disease of the LAD was found in 15 (25%) patients. The sensitivity and the specificity of SPECT was found to be 75% and 89%, respectively; the positive predictive value (PPV) was 70% with a negative predictive value (NPV) of 91%. During the adenosine infusion the QRS complex width reduced from 131.3 +/- 29.6 ms to 125.5 +/- 28.6 ms in the patients without LAD involvement (P = 0.008) but remained unchanged in LAD disease patients (P = 0.1). Combining SPECT information and QRS analysis the sensitivity increased to 87% with unchanged specificity, the PPV was 74% and the NPV resulted 95%. At 2-year follow-up 13 (22%) patients experienced a cardiac event. Using Kaplan-Meier analysis, an LVEF of < or = 35% was the only predictor of cardiac events (P = 0.01, log-rank 6.2).

CONCLUSIONS

A quarter of patients with LBBB complaining of chest pain had LAD coronary disease. The highly negative predictive value of adenosine SPECT could help in the exclusion of LAD disease, especially when the SPECT image is combined with the QRS analysis.

Usefulness of myocardial perfusion SPECT in patients with left bundle branch block and previous myocardial infarction

BACKGROUND

The diagnostic value of myocardial perfusion scintigraphy in patients with left bundle branch block (LBBB) and previous acute myocardial infarction has not been evaluated.

OBJECTIVE

To determine the utility of single photon emission computed tomography (SPECT) in patients with LBBB and previous acute myocardial infarction.

METHODS

Seventy two consecutive patients with permanent LBBB and previous acute myocardial infarction were studied with stress-rest SPECT using 99mTc compounds. The same stress procedures were followed in all patients: (1) exercise alone when it was sufficient; (2) exercise plus simultaneous administration of dipyridamole if exercise was insufficient.

RESULTS

In 26 of 28 patients (93%) who had a Q wave acute myocardial infarct before the development of LBBB, there was concordance between abnormal Q waves and rest SPECT in the localisation of myocardial necrosis (kappa = 0.836; p = 0.0001). In 48 patients who had coronary angiography, the positive predictive value of exercise (+dipyridamole) myocardial SPECT for the diagnosis of left anterior descending coronary artery stenosis was 93%, for left circumflex coronary artery stenosis, 96%, and for right coronary artery stenosis, 89%. Specificity values were 83%, 91%, and 69%, respectively. However, sensitivity (69%, 64%, and 89%) and negative predictive values (48%, 46%, and 82%) were suboptimal.

CONCLUSIONS

Rest myocardial perfusion SPECT with technetium compounds is useful for localising healed myocardial infarction in patients with LBBB, and exercise (+dipyridamole) SPECT has a high positive predictive value and specificity for the diagnosis of coronary stenosis in these patients.

Myocardial perfusion and adrenergic innervation in patients with RBBB and LAfB: the effect of altering the activation sequence with right ventricular apical pacing

The aim of this study was to investigate myocardial perfusion and adrenergic innervation in patients with intraventricular conduction disturbances and to detect any changes caused by alteration of the ventricular activation sequence as a result of right ventricular apical pacing. We studied 15 patients with right bundle branch block (RBBB) and left anterior fascicular block (LAFB), while 15 healthy individuals served as controls. All patients underwent planar and single-photon emission computed tomography (SPECT) myocardial imaging after intravenous infusion of 5mCi 123I-metaiodobenzylguanidine (123I-MIBG) and a SPECT thallium201 myocardial perfusion study before and 3 months after pacemaker implantation. The heart to mediastinum ratio was calculated during the 123I-MIBG study in order to assess the global cardiac sympathetic activity and was significantly smaller in patients than in controls (P < 0.001). Patients with RBBB and LAFB revealed regional adrenergic innervation defects, mostly in the inferior and posterior walls. After a medium-term pacing period, a redistribution of 123I-MIBG uptake was detected, with aggravation of adrenergic innervation defects in the apical and posterior walls and amelioration in septal and anterior walls. Five patients showed perfusion defects that remained unchanged after pacing. Two others displayed mild myocardial perfusion defects that did not exist before pacing. In conclusion, patients with RBBB and LAFB reveal global and regional disturbances of myocardial adrenergic innervation, which shows redistribution as a result of the altered propagation of the ventricular electrical activation. To a smaller degree these patients reveal myocardial perfusion disturbances in which pacing has a limited medium-term effect.

Pharmacologic radionuclide myocardial perfusion imaging

Pharmacologic stress testing with myocardial perfusion imaging has enabled patients who cannot complete adequate exercise to undergo diagnostic and prognostic evaluation for coronary artery disease. Pharmacologic stress agents belong to two groups: vasodilators (such as adenosine and dipyridamole), and inotropes (such as dobutamine). All have similar sensitivity (89%-91%) and specificity (78%-86%) for the diagnosis of coronary disease. For risk stratification, the risk of future cardiac events is related to the extent and severity of perfusion abnormalities. Pharmacologic stress testing permits risk stratification as early as 1 to 4 days following an acute myocardial infarction, and is superior to exercise stress testing in this regard. Similarly, it identifies patients at high risk for perioperative cardiac events prior to noncardiac surgery. This review summarizes the current evidence available regarding the diagnostic and prognostic use of pharmacologic stress testing.

Use of pharmaceuticals in noninvasive cardiovascular diagnosis

A number of pharmaceuticals are employed as diagnostic agents for cardiovascular diseases. Four groups of agents are reviewed here: 1) vasoactive substances employed as adjuncts to physical maneuvers in diagnosis of structural heart disease; 2) vasodilators used to produce heterogeneity of coronary flow; 3) sympathomimetic agents simulating the effects of exercise on the heart for the purpose of detection of coronary artery stenosis; and 4) ultrasonic contrast agents used to enhance myocardial imaging for the assessment of segmental wall motion. In the first group are amyl nitrate, a vasodilator, and methoxamine and phenylephrine, both vasopressors. The vasodilators of the second group are dipyridamole and adenosine. When combined with scintigraphic perfusion imaging or with echocardiographic assessment of segmental wall motion, these agents can detect single- or multiple-vessel coronary artery disease with sensitivity and specificity comparable to submaximal exercise. They are especially useful for preoperative risk assessment before noncardiac surgery. The sympathomimetic agents of the third group, dobutamine and arbutamine, increase myocardial contractility and heart rate, and dilate the peripheral vasculature. As with the vasodilators, when combined with nuclear or echocardiographic techniques they are equivalent to exercise in detection of coronary disease. They are especially useful in patients with bronchospastic disease and for assessment of myocardial viability. Agents from groups 2 and 3 have acceptable side-effect and safety profiles. The last group reviewed includes echocardiographic contrast agents that, in this investigative setting, are employed to enhance detection of segmental wall motion when used with agents from groups 2 and 3.

The diagnosis of coronary artery disease in hypertensive patients with chest pain and complete left bundle branch block: utility of adenosine Tc-99m tetrofosmin SPECT

PURPOSE

Hypertensive patients with complete left bundle branch block who experience chest pain present special problems in the radionuclide diagnosis of coronary artery disease (CAD). The aim of this study was to assess the utility of Tc-99m tetrofosmin SPECT for the diagnosis of CAD in 35 hypertensive patients with left bundle branch block hospitalized for chest pain.

MATERIALS AND METHODS

Images were analyzed semiquantitatively for the presence of both fixed or reversible perfusion defects (method A) or only reversible defects (method B) in the distribution of the left anterior descending artery (LAD) territory. Perfusion defects observed in the territory of any other coronary artery were always considered. Thirty-five patients without infarction underwent adenosine Tc-99m tetrofosmin SPECT, transthoracic echocardiography, and coronary angiography.

RESULTS

The mean left ventricular ejection fraction was calculated as 39.9% +/- 11.6%, and the prevalence of CAD was 29%. The sensitivity of SPECT was identical for the two methods at 89%. The specificity increased 19% with method A and 54% with method B. The positive predictive value remained unsatisfactorily low with both methods (27% for method A and 40% for method B), and the negative predictive value improved from 83% with method A to 93% with method B.

CONCLUSIONS

Only reversible perfusion defects in the LAD territory should be considered significant for CAD, and these patients should undergo coronary angiography. Reversible or fixed perfusion defects in the left circumflex and right coronary artery territories should be evaluated according to other clinical parameters (global left ventricular ejection fraction, extension of perfusion defects). The highly negative predictive value of adenosine SPECT could help in the exclusion of CAD.

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.

Tc-99m sestamibi gated SPECT in patients with left bundle branch block

PURPOSE

The purpose of this study was to assess the diagnostic role of a Tc-99m sestamibi gated SPECT technique in patients with left bundle branch block (LBBB) without known coronary artery disease.

MATERIALS AND METHODS

Twenty consecutive patients with constant complete LBBB were included. A same-day rest-stress protocol was used, and dipyridamole stress (14 patients) or treadmill exercise (6 patients) was applied. Electrocardiograph (ECG)-gated SPECT images were acquired 15 minutes after the administration of 0.31 mCi/kg Tc-99m sestamibi at peak stress. Regional myocardial perfusion was analyzed in relation to the cardiac cycle.

RESULTS

Eleven of 14 patients who underwent a dipyridamole stress test had hypoactivity in the left anterior descending (LAD) artery territory in the ungated (summed) stress-rest images (abnormality ratio, 78%). On the ungated images, the abnormality was completely reversible in one patient (9%), partially reversible in five patients (46%), irreversible in two patients (18%), and reverse perfusion was identified in three patients (27%). Abnormality ratios of end-systolic and end-diastolic data were 93% and 29%, respectively. Conversely, the ungated rest-stress and end-systolic images of all the patients who performed treadmill exercise were abnormal despite the presence of normal or nearly normal end-diastolic myocardial perfusion. The angiographic findings correlated best with those of end-diastolic images. In 13 patients without coronary artery disease, normal or nearly normal regional perfusion was observed on end-diastole, but four patients with abnormal end-diastolic perfusion, which involved the LAD territory in all but one, had substantial coronary artery disease. The number of the involved segments was similar on the end-systolic and ungated data. Most of these artifactual defects were localized to the anteroseptal, septal, and inferoseptal segments.

CONCLUSIONS

These preliminary data indicate that end-diastolic images can significantly reduce artifactual defects in patients with LBBB. The resolution of an LBBB pattern on end-diastolic data would significantly improve the diagnostic role of myocardial perfusion studies in these patients.

Standard provocative manoeuvres in patients with and without left bundle branch block studied with myocardial SPECT

BACKGROUND

The objective of this study was to determine the prevalence of anterior and septal defects in patients with left bundle branch block (LBBB), and to assess the diagnostic accuracy of myocardial single photon emission computed tomography (SPECT) with technetium compounds in patients with and without LBBB using standard provocative manoeuvres.

METHODS

Five hundred and nine consecutive patients (456 without LBBB and 53 with LBBB) without previous infarction who had a coronary angiography performed within <3 months of the scintigraphic study were retrospectively evaluated. The same stress procedures were followed in all patients. (1) Only exercise when it was sufficient; and (2) exercise + simultaneous administration of dypiridamole if exercise was insufficient. Only reversible defects were considered positive and > or =50% of coronary stenosis was considered significant.

RESULTS

Prevalence of reversible anterior and septal defects was low (33% and 12%, respectively) in patients with LBBB. Although lower values of global sensitivity (81%) and specificity (73%) were obtained in these patients, there were no significant differences with respect to the patients without LBBB (89% and 86%, respectively). Specificity values for the diagnosis of stenosis of left anterior descending (78%), left circumflex (96%) and right coronary artery (74%) in patients with LBBB were lower, but without significant statistical differences with respect patients without LBBB (90%, 96% and 82%, respectively).

CONCLUSIONS

Myocardial SPECT with technetium compounds, using standard provocation manoeuvres, can be used in patients with LBBB with only a mild decrease in diagnostic accuracy as compared to patients without LBBB.

Does inadequate exercise lower the accuracy of myocardial perfusion scintigraphy?

The predictive accuracy of exercise myocardial perfusion scintigraphy (EMPS) in detecting coronary artery disease (CAD) in patients who fail to achieve an adequate level of exercise is not clear. This investigation was carried out in order to compare the sensitivity, specificity and accuracy of EMPS in adequate exercise patients with those in inadequate exercise patients. We have retrospectively compared the results of EMPS with coronary angiography (CAG). One hundred and forty-eight patients with both tests within 6 weeks were included. Adequate exercise was defined as > or = 85% maximally predicted heart rate for age. The overall sensitivity and specificity of EMPS to detect CAD were 92.5% (74/80) and 75%, (51/68), respectively. The sensitivity and specificity in adequate exercise patients were 94.1% (32/34) and 67.6% (23/34), whereas those in inadequate exercise patients were 91.3% (42/46) and 82.4% (28/34). The accuracy was 80.9% (55/68) and 87.5% (70/80), respectively. Patients with inadequate exercise had lower sensitivity but higher specificity of EMPS for detecting CAD, and achieved a higher accuracy than those with adequate exercise.

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.

[Utility of SPECT with 99m Tc-tetrofosmin and stimulus with dipyridamole in patients with permanent ventricular pacemakers]

BACKGROUND AND OBJECTIVE

Patients with permanent ventricular pacemakers (PP) are a difficult subgroup to assess in the study of coronary artery disease. The objective of this study was to evaluate the diagnostic value of the myocardial perfusion scintigraphy with 99mTC-Tetrofosmin (Tc-Tf) and stimulus with dipyridamole in patients with PP and suspected coronary artery disease.

PATIENTS AND METHODS

Fourteen patients with suspected coronary artery disease and without structural cardiopathy, who underwent Tc-Tf and cardiac catheterization, were studied retrospectively. Sensitivity, specificity, predictive values and Kappa index were calculated for the diagnosis of coronary artery disease, multivessel disease, and for each one of the coronary arteries (left anterior descending, right coronary, and circumflex). In addition, the correlation between the number of territories with perfusion defects and the number of diseased vessels was studied.

RESULTS

In regards to the diagnosis of coronary artery disease, sensitivity, specificity, positive predictive value, negative predictive value and the Kappa index were 100%, 50%, 83%, 100% and 0.55, respectively. For multi-vessel disease, these values were 83%, 64%, 64%, 83% and 0.43 respectively. The correlation coefficient between the number of territories with perfusion defects and the number of diseased vessels was 0.61 (p = 0.02). In the diagnosis of anterior descending disease, sensitivity and specificity were 83% and 88% respectively. For the right coronary artery, these values were 100% and 44% and for the circumflex artery 38% and 83%, respectively.

CONCLUSION

In patients with PP and suspected coronary artery disease, myocardial perfusion scintigraphy with Tc-Tf and stimulus with dipyridamole is of great value in the diagnosis of coronary artery disease and in the assessment of its extension.