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

Assessment of Myocardial Viability in Ischemic Cardiomyopathy With Reduced Left Ventricular Function Undergoing Coronary Artery Bypass Grafting

BACKGROUND

We aim to provide a comprehensive review of the current state of knowledge of myocardial viability assessment in patients undergoing coronary artery bypass grafting (CABG), with a focus on the clinical markers of viability for each imaging modality. We also compare mortality between patients with viable myocardium and those without viability who undergo CABG.

METHODS

A systematic database search with meta-analysis was conducted of comparative original articles (both observations and randomized controlled studies) of patients undergoing CABG with either viable or nonviable myocardium, in EMBASE, MEDLINE, Cochrane database, and Google Scholar, from inception to 2022. Imaging modalities included were dobutamine stress echocardiography (DSE), cardiac magnetic resonance (CMR), single-photon emission computed tomography (SPECT), and positron emission tomography (PET).

RESULTS

A total of 17 studies incorporating a total of 2317 patients were included. Across all imaging modalities, the relative risk of death post-CABG was reduced in patients with versus without viability (random-effects model: odds ratio: 0.42; 95% confidence interval: 0.29-0.61; p < 0.001). Imaging for myocardial viability has significant clinical implications as it can affect the accuracy of the diagnosis, guide treatment decisions, and predict patient outcomes. Generally, based on local availability and expertise, either SPECT or DSE should be considered as the first step in evaluating viability, while PET or CMR would provide further evaluation of transmurality, perfusion metabolism, and extent of scar tissue.

CONCLUSION

The assessment of myocardial viability is an essential component of preoperative evaluation in patients with ischemic heart disease undergoing surgical revascularization. Careful patient selection and individualized assessment of viability remain paramount.

Myocardial perfusion and flow reserve in the asynchronous heart: mechanistic insight from a computational model

The tight coupling between myocardial oxygen demand and supply has been recognized for decades, but it remains controversial whether this coupling persists under asynchronous activation, such as during left bundle branch block (LBBB). Furthermore, it is unclear whether the amount of local cardiac wall growth, following longer-lasting asynchronous activation, can explain differences in myocardial perfusion distribution between subjects. For a better understanding of these matters, we built upon our existing modeling framework for cardiac mechanics-to-perfusion coupling by incorporating coronary autoregulation. Regional coronary flow was regulated with a vasodilator signal based on regional demand, as estimated from regional fiber stress-strain area. Volume of left ventricular wall segments was adapted with chronic asynchronous activation toward a homogeneous distribution of myocardial oxygen demand per tissue weight. Modeling results show that 1) both myocardial oxygen demand and supply are decreased in early activated regions and increased in late-activated regions; 2) but that regional hyperemic flow remains unaffected; while 3) regional myocardial flow reserve (the ratio of hyperemic to resting myocardial flow) decreases with increases in absolute regional myocardial oxygen demand as well as with decreases in wall thickness. These findings suggest that septal hypoperfusion in LBBB represents an autoregulatory response to reduced myocardial oxygen demand. Furthermore, oxygen demand-driven remodeling of wall mass can explain asymmetric hypertrophy and the related homogenization of myocardial perfusion and flow reserve. Finally, the inconsistent observations of myocardial perfusion distribution can primarily be explained by the degree of dyssynchrony, the degree of asymmetric hypertrophy, and the imaging modality used.NEW & NOTEWORTHY This versatile modeling framework couples myocardial oxygen demand to oxygen supply and myocardial growth, enabling simulation of resting and hyperemic myocardial flow during acute and chronic asynchronous ventricular activation. Model-based findings suggest that reported inconsistencies in myocardial perfusion and flow reserve responses with asynchronous ventricular activation between patients can primarily be explained by the degree of dyssynchrony and wall mass remodeling, which together determine the heterogeneity in regional oxygen demand and, hence, supply with autoregulation.

Five-year morbidity and mortality of patients with ischemia with non-obstructive coronary arteries and myocardial single-photon emission computed tomography perfusion defects

INTRODUCTION

Patients with angina and a positive single-photon emission computed tomography (SPECT) scan for reversible ischemia, with no or non-obstructive coronary artery disease (CAD) on invasive coronary angiography (ICA), represent a frequent clinical problem and predicting prognosis is challenging.

METHODS

This was a retrospective single-center study on patients who underwent elective ICA with angina and a positive SPECT with no or non-obstructive CAD over a seven-year period. Cardiovascular morbidity, mortality, and major adverse cardiac events were assessed during a follow-up of at least three years after ICA, with the aid of a telephone questionnaire.

RESULTS

Data on all patients who underwent ICA in our hospital over a period of seven years (between January 1, 2011 and December 31, 2017) were analyzed. A total of 569 patients fulfilled the pre-specified criteria. In the telephone survey, 285 (50.1%) were successfully contacted and agreed to participate. Mean age was 67.6 (SD 8.8) years (35.4% female) and mean follow-up was 5.53 years (SD 1.85). Mortality was 1.7% (four patients, from non-cardiac causes), 1.7% underwent revascularization, 31 (10.9%) were hospitalized for cardiac reasons and 10.9% reported symptoms of heart failure (no patients with NYHA class>II). Twenty-one had arrhythmic events and only two had mild anginal symptoms. It was also noteworthy that mortality in the uncontacted group (12 out of 284, 4.2%), derived from public social security records, did not differ significantly from the contacted group.

CONCLUSIONS

Patients with angina, a positive SPECT for reversible ischemia and no or non-obstructive CAD on ICA have excellent long-term cardiovascular prognosis for at least five years.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Mask-Related Motion Artifact on 99mTc-MIBI SPECT: Unexpected Pitfalls of SARS-CoV-2 Countermeasures

A 61-year-old man was referred for myocardial perfusion scintigraphy (MPS) by an occupational physician to exclude coronary artery disease (CAD). The patient had a complete left bundle branch block (LBBB) that rendered the routine exercise stress test non-diagnostic, but otherwise had no history of heart diseases, good stress tolerance with no symptoms of angina, and no abnormalities in transthoracic echocardiogram, apart from contraction patterns typical for LBBB. Initial MPS, performed using technetium-labeled Sestamibi on a Discovery NM 530c camera equipped with solid-state semiconductor detectors, revealed a significant stress-induced ischemia that did not match the good overall condition of the patient. A motion detection procedure revealed significant heart motion in Z-axis during the stress study. Upon inquiry, the patient reported breathing difficulties caused by the mandatory mask, which slipped into an uncomfortable position during the study. Repeated acquisition, without motion artifacts, revealed no features of ischemia.

Role of coronary flow regulation and cardiac-coronary coupling in mechanical dyssynchrony associated with right ventricular pacing

Mechanical dyssynchrony (MD) affects left ventricular (LV) mechanics and coronary perfusion. To understand the multifactorial effects of MD, we developed a computational model that bidirectionally couples the systemic circulation with the LV and coronary perfusion with flow regulation. In the model, coronary flow in the left anterior descending (LAD) and left circumflex (LCX) arteries affects the corresponding regional contractility based on a prescribed linear LV contractility-coronary flow relationship. The model is calibrated with experimental measurements of LV pressure and volume, as well as LAD and LCX flow rate waveforms acquired under regulated and fully dilated conditions from a swine under right atrial (RA) pacing. The calibrated model is applied to simulate MD. The model can simultaneously reproduce the reduction in mean LV pressure (39.3%), regulated flow (LAD: 7.9%; LCX: 1.9%), LAD passive flow (21.6%), and increase in LCX passive flow (15.9%). These changes are associated with right ventricular pacing compared with RA pacing measured in the same swine only when LV contractility is affected by flow alterations with a slope of 1.4 mmHg/mL² in a contractility-flow relationship. In sensitivity analyses, the model predicts that coronary flow reserve (CFR) decreases and increases in the LAD and LCX with increasing delay in LV free wall contraction. These findings suggest that asynchronous activation associated with MD impacts 1) the loading conditions that further affect the coronary flow, which may explain some of the changes in CFR, and 2) the coronary flow that reduces global contractility, which contributes to the reduction in LV pressure.NEW & NOTEWORTHY A computational model that couples the systemic circulation of the left ventricular (LV) and coronary perfusion with flow regulation is developed to study the effects of mechanical dyssynchrony. The delayed contraction in the LV free wall with respect to the septum has a significant effect on LV function and coronary flow reserve.

Effect of cardiac resynchronization therapy on septal perfusion and septal thickening: Association with left ventricular function, reverse remodelling and dyssynchrony

BACKGROUND

We evaluated the effect of cardiac resynchronization therapy (CRT) on septal perfusion and thickening at 6 months post implantation assessed on Tc99m-MIBI Gated myocardial perfusion SPECT (GMPS).We also studied the association of change in septal perfusion and thickening with primary outcome defined as at least one [improvement in ≥1NYHA class, left ventricular ejection fraction (LVEF) by ≥ 5%, reduction of end-systolic volume (ESV) by ≥ 15%, and improvement ≥ 5 points in Minnesota living with heart failure questionnaire (MLHFQ)].

METHOD

One hundred and five patients underwent clinical and GMPS evaluation before and at 6 months post CRT.

RESULT

Post CRT there was significant improvement in mean normalized septal perfusion uptake and in septal thickening (P value = 0.001, both). There was no significant relation between improvement in septal perfusion and primary outcome. However, improvement in septal thickening was statistically significant with favorable primary outcome (P = 0.001).There was no significant correlation between improvement of septal perfusion and improvement in LVEF, reduction in End diastolic volume (EDV), ESV, and Left ventricular Dyssynchrony (LVD). But, there was significant correlation between improvement of septal thickening and these parameters.

CONCLUSION

Improvement in septal thickening was associated with reverse remodeling, improvement in LVEF, and reduction of LVD.

Comparison of Quantitative Perfusion and Function Parameters of Gated-SPECT Myocardial Perfusion Imaging in Patients With Concordant and Discordant Left Bundle-Branch Block

BACKGROUND

Patients with left bundle-branch block (LBBB) can be classified to discordant LBBB (dLBBB) and concordant LBBB (cLBBB) according to T-wave orientation in lateral leads. This classification indicates different functional left ventricular (LV) parameters with worse prognosis in dLBBB patients. However, there are no data regarding the impact of this classification on perfusion status of the left ventricle. The aim of this study is to evaluate and compare the SPECT myocardial perfusion imaging (MPI) findings of LV perfusion and function between dLBBB and cLBBB patients.

METHODS

All patients who were referred for SPECT MPI during an 11 months' period were evaluated. Patients with evidence of LBBB on standard baseline 12-lead ECG were included, and their demographic, medical history, and imaging data were recorded. Quantitative perfusion and function parameters of LV included summed stress score, summed rest score, summed difference score, total perfusion deficit (TPD) at both phases with delta TPD, ejection fraction, end-diastolic volume, end-systolic volume, summed motion score, summed thickening score, phase SD, and phase histogram bandwidth. All baseline ECGs were further assessed by a cardiologist to categorize patients as the cLBBB or dLBBB group according to concordance of the T wave with QRS complex in lateral leads.

RESULTS

Finally, 97 patients with 46 cLBBB and 51 dLBBB cases were included. Baseline characteristics and cardiovascular risk factors including diabetes mellitus, hypertension, hyperlipidemia, history of coronary artery disease (CAD), family history of CAD, and smoking were not significantly different between the 2 groups. However, summed stress score (12.2 vs 6.7), summed difference score (4.0 vs 2.6), stress TPD (11.0 vs 6.4), and delta TPD (4.8 vs 3.9) were significantly higher in dLBBB patients. In addition, functional parameters were also significantly worse in dLBBB patients with lower ejection fraction and higher end-diastolic volume, end-systolic volume, summed motion score, and summed thickening score in these patients. Mean phase SD and phase histogram bandwidth were also significantly higher in dLBBB patients.

CONCLUSIONS

This study revealed that LBBB patients with discordant T wave in lateral leads have significantly higher ischemic scores and worse functional parameters with more dyssynchrony in gated SPECT MPI.

X-ray computed tomography and its potential in ecological research: A review of studies and optimization of specimen preparation

Imaging techniques are a cornerstone of contemporary biology. Over the last decades, advances in microscale imaging techniques have allowed fascinating new insights into cell and tissue morphology and internal anatomy of organisms across kingdoms. However, most studies so far provided snapshots of given reference taxa, describing organs and tissues under "idealized" conditions. Surprisingly, there is an almost complete lack of studies investigating how an organism's internal morphology changes in response to environmental drivers. Consequently, ecology as a scientific discipline has so far almost neglected the possibilities arising from modern microscale imaging techniques. Here, we provide an overview of recent developments of X-ray computed tomography as an affordable, simple method of high spatial resolution, allowing insights into three-dimensional anatomy both in vivo and ex vivo. We review ecological studies using this technique to investigate the three-dimensional internal structure of organisms. In addition, we provide practical comparisons between different preparation techniques for maximum contrast and tissue differentiation. In particular, we consider the novel modality of phase contrast by self-interference of the X-ray wave behind an object (i.e., phase contrast by free space propagation). Using the cricket Acheta domesticus (L.) as model organism, we found that the combination of FAE fixative and iodine staining provided the best results across different tissues. The drying technique also affected contrast and prevented artifacts in specific cases. Overall, we found that for the interests of ecological studies, X-ray computed tomography is useful when the tissue or structure of interest has sufficient contrast that allows for an automatic or semiautomatic segmentation. In particular, we show that reconstruction schemes which exploit phase contrast can yield enhanced image quality. Combined with suitable specimen preparation and automated analysis, X-ray CT can therefore become a promising quantitative 3D imaging technique to study organisms' responses to environmental drivers, in both ecology and evolution.

Myocardial perfusion scintigraphy - interpretation of gated imaging. Part 2

The first part of the review describes the basic aspects of interpreting myocardial perfusion defects in single photon emission computed tomography (SPECT) scintigraphy. It also presents indications for invasive diagnostics based on stress perfusion defects. This article provides basic information concerning the interpretation of gated SPECT imaging, including such parameters as left ventricular wall motion and thickening as well as left ventricular wall systolic and diastolic function. Gated examination combined with the assessment of myocardial perfusion reduces the rate of false positives results of myocardial perfusion scintigraphy in perfusion tests, additionally providing data on left ventricular systolic and diastolic function.

Cardiac Resynchronization Therapy Relieves Intractable Angina Due to Exercise-Induced Left Bundle Branch Block Without Left Ventricular Systolic Dysfunction: A Detailed Case Study

Exercise-induced left bundle branch block is rare and can be demonstrated with exercise testing. When the heart rate reaches a certain threshold, the QRS widens into left bundle branch block. This paper describes a patient with exercise-induced left bundle branch block related angina and dyspnea, who responded to cardiac resynchronization therapy. We documented the potential benefits of cardiac resynchronization therapy with a left ventricular rapid pacing study prior to its implantation. Although exercise-induced left bundle branch block is not a current indication for cardiac resynchronization therapy in patients such as ours, it could be considered when conventional drug therapy fails.

Septal and anterior reverse mismatch of myocardial perfusion and metabolism in patients with coronary artery disease and left bundle branch block

The effects of left bundle branch block (LBBB) on left ventricular myocardial metabolism have not been well investigated. This study evaluated these effects in patients with coronary artery disease (CAD).Sixty-five CAD patients with complete LBBB (mean age, 61.8 ± 9.7 years) and 65 without LBBB (mean age, 59.9 ± 8.4 years) underwent single photon emission computed tomography, positron emission tomography, and contrast coronary angiography. The relationship between myocardial perfusion and metabolism and reverse mismatch score, and that between QRS length and reverse mismatch score and wall motion score were evaluated.The incidence of left ventricular septum and anterior wall reverse mismatching between the two groups was significantly different (P < 0.001 and P = 0.002, respectively). The incidences of normal myocardial perfusion and metabolism in the left ventricular lateral and inferior walls were also significantly different between the two groups (P < 0.001 and P < 0.001, respectively). The incidence of septal reverse mismatching in patients with mild to moderate perfusion was significantly higher among those with LBBB than among those without LBBB (P < 0.001). In CAD patients with LBBB, septal reverse mismatching was significantly more common among those with mild to moderate perfusion than among those with severe perfusion defects (P = 0.002). The correlation between the septal reverse mismatch score and QRS length was significant (P = 0.026).In patients with CAD and LBBB, septal and anterior reverse mismatching of myocardial perfusion and metabolism was frequently present; the septal reverse mismatch score negatively correlated with the QRS interval.

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.

Noninvasive Detection of Functional Myocardial Ischemia: Multifunction Cardiogram Evaluation in Diagnosis of Functional Coronary Ischemia Study (MED-FIT)

BACKGROUND

Multifunction cardiogram (MCG) is a computer-enhanced, resting electrocardiogram analysis developed to detect hemodynamically relevant coronary artery disease (CAD). Based on data from previous studies suggesting excellent diagnostic accuracy in detecting CAD, MCG (approved by the Food and Drugs Administration) received a Current Procedure Terminology (CPT) code in 2010 in United States. However, there is no previous study validating MCG by using fractional flow reserve (FFR) as the reference standard.

METHODS

Multifunction cardiogram Evaluation in Diagnosis of Functional coronary Ischemia sTudy (MED-FIT) was designed as a single-center, prospective study enrolling 100 stable patients with suspected CAD scheduled for coronary angiography. The primary and secondary analyses evaluated the diagnostic performance of the MCG severity score to detect functional myocardial ischemia by FFR ≤0.80, and angiographically significant coronary stenosis (percent diameter stenosis ≥50%) by quantitative coronary angiography.

RESULTS

The current analysis set consisted of 91 patients in whom MCG data with adequate quality was obtained. The prevalence of positive functional myocardial ischemia and angiographically significant stenosis in the current study was 42.7% and 41.8%, respectively. Area under the receiver operating characteristics curve (AUC) of the MCG severity score for functional myocardial ischemia and angiographically significant stenosis was low (AUC 0.51, 95% confidence interval [CI] 0.38-0.63, and AUC 0.58, 95%CI 0.46-0.70, respectively). Sensitivity, and specificity of the MCG severity score for functional myocardial ischemia and angiographically significant stenosis was also low (32%/67%, and 37%/72%) using a cutoff value of 4.0.

CONCLUSIONS

Diagnostic performance of the MCG severity score was poor for both functional myocardial ischemia, and angiographically significant stenosis.

Current concepts relating coronary flow, myocardial perfusion and metabolism in left bundle branch block and cardiac resynchronisation therapy

Cardiac resynchronisation therapy (CRT) improves mortality and symptoms in heart failure patients with electromechanically dyssynchronous ventricles. There is a 50% non-response rate and reproducible biomarkers to predict non-response have not been forthcoming. Therefore, there has been increasing interest in the pathophysiological effects of dyssynchrony particularly focusing on coronary flow, myocardial perfusion and metabolism. Studies suggest that dyssynchronous electrical activation effects coronary flow throughout the coronary vasculature from the epicardial arteries to the microvascular bed and that these changes can be corrected by CRT. The effect of both electrical and mechanical dyssynchrony on myocardial perfusion is unclear with some studies suggesting there is a reduction in septal perfusion whilst others propose that there is an increase in lateral perfusion. Better understanding of these effects offers the possibility for better prediction of non-response. CRT appears to improve homogeneity in myocardial perfusion where heterogeneity is described in the initial substrate. Novel approaches to the identification of non-responders via metabolic phenotyping both invasively and non-invasively have been encouraging. There remains a need for further research to clarify the interaction of coronary flow with perfusion and metabolism in patients who undergo CRT.

Relationship of decreased accumulation of (99m)Tc-tetrofosmin on myocardial single-photon emission computed tomography images between QRS duration in dilated cardiomyopathy patient with left bundle branch block

PURPOSE

This study aimed to clarify the relationship between severity of conduction delay in the left ventricle and myocardial uptake of (99m)Tc-tetrofosmin (TF) in dilated cardiomyopathy (DCM) patients with left bundle branch block (LBBB).

METHODS AND RESULTS

Thirty-two DCM patients with LBBB underwent electrocardiography and (99m)Tc-TF myocardial single-photon emission computed tomography (SPECT). SPECT images were acquired at 30 min (early images) and 3 h (late images) after injection. We calculated the total defect score (TDS) using a 20-segment model with a 5-point scoring system. The TDS in early and late images was defined as the summed early score (SES) and summed late score (SLS), respectively. On early images, 29 of 32 patients (91%) had decreased tracer uptake in the septum. All patients showed a decreased tracer uptake in the septum on late images. A significant correlation was observed between TDS (both SES and SLS) and QRS duration, with SLS showing an excellent correlation (SES: r = 0.554, P < 0.001; SLS: r = 0.779, P < 0.0001).

CONCLUSIONS

These findings suggest that in DCM patients with LBBB, hypoperfusion and myocardial damage in the septum might occur in accordance with an increase in the QRS duration.

Cardiac resynchronization therapy restored ventricular septal myocardial perfusion and enhanced ventricular remodeling in patients with nonischemic cardiomyopathy presenting with left bundle branch block

BACKGROUND

Left bundle branch block (LBBB) causes intraventricular conductional delay, which results in left ventricle (LV) mechanical dyssynchrony. In the absence of coronary artery disease, patients with LBBB often have diminished accumulation of technetium-99m compounds at the myocardial septal area in electrocardiogram-gated single-photon emission computed tomography.

OBJECTIVE

To investigate whether cardiac resynchronization therapy (CRT) could improve septal myocardial perfusion, leading to favorable reverse remodeling.

METHODS

The study included all 26 patients with nonischemic cardiomyopathy eligible for CRT, who presented with LBBB, New York Heart Association class II-IV heart failure, and LV ejection fraction ≤35%. Single-photon emission computed tomography was performed at baseline and 6 months after CRT. Perfusion counts were measured at the ventricular septum and LV lateral free wall. Left ventricular end-systolic volume (LVESV) was measured by echocardiography to evaluate LV reverse remodeling by CRT.

RESULTS

At baseline, a perfusion defect at the LV septal myocardial area was confirmed in 19 of 26 (73%) patients. In these patients, septal perfusion significantly increased 6 months after CRT (56.1% ± 22.8% vs 82.9% ± 21.2%; P < .001). LVESV reduction and improved septal perfusion index were positively correlated (r = .561; P = .012), whereas no correlation was found between LVESV reduction and the difference of QRS duration before and 6 months after CRT (r = .218; P = .371). The improvement in LV septal perfusion was associated with LV reverse remodeling.

CONCLUSIONS

CRT could restore LV septal myocardial perfusion and ameliorate ventricular reverse remodeling in most patients with nonischemic cardiomyopathy and LBBB.

Implications of left bundle branch block in patient treatment

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

Evaluation of Risk Factors in Predicting Coronary Artery Disease in Patients with Left Bundle Branch Block

This retrospective study examined whether classical risk factors for coronary artery disease (CAD) could also be used to predict CAD in patients with left bundle branch block (LBBB). Clinical and demographic features were studied in patients with/without CAD who presented with LBBB on their surface electrocardiograms and had undergone coronary angiography. Of the 312 patients with LBBB, 161 (51.6%) had CAD. Patients with CAD were more likely to be older, male, have CAD risk factors and to be taking acetylsalicylic acid or angiotensin-converting enzyme inhibitors. A model with six independent variables (family history, smoking, angina, advanced age, hypertension and total cholesterol levels) was statistically significant in predicting CAD in patients with LBBB, with an ability to predict patients with and without CAD of 87.1% and 90.6%, respectively. Predictors of CAD in patients with LBBB are consistent with classical risk factors and may help the accurate prediction of patients with CAD.

Muscular ventricular septal defect visualized as nonreversible perfusion abnormality on myocardial perfusion SPECT and confirmed on cardiac computed tomography angiography images

A 47-year-old woman with no history of CAD presented with an episode of left-sided atypical chest pain. Her work-up was negative for acute MI. She underwent a myocardial perfusion Tc-99m tetrofosmin SPECT study to rule out myocardial ischemia. The SPECT images revealed a small nonreversible mid-anteroseptal perfusion defect. For additional evaluation coronary computed tomography angiography was performed. This revealed normal coronary arteries and demonstrated a small muscular ventricular septal defect which corresponded to the location of the fixed perfusion defect on the SPECT images. The presence of the ventricular septal defect should be considered in differential diagnosis of an isolated fixed septal perfusion abnormality on SPECT images in patients with no history of prior MI.