Left Bundle Branch Block Group Research Articles

60 * Greater mechanical dyssynchrony is demonstrated by cardiac magnetic resonance cine imaging amongst heart failure patients awaiting cardiac resynchronisation therapy with strict left bundle branch block

Introduction: The era of cardiac resynchronisation therapy (CRT) has led to improved understanding of left ventricular activation and stricter criteria have been proposed for left bundle branch block (LBBB). These criteria have shown a greater prediction for LV mechanical dyssynchrony with 2D strain echocardiography and cardiac MRI tagging. We have further tested this hypothesis using cardiac cine MRI endocardial tracking technology and also investigated the impact of this measure of mechanical dyssynchrony on CRT response rate. Methods: We investigated a total of 47 patients awaiting CRT with traditional LBBB with a cardiac MRI pre implant. Offline analysis of the cine imaging was undertaken in order to determine the endocardial volume change systolic dyssynchrony index (SDI) of 16 segments. Pre-implant ECGs were analyzed for strict LBBB (QRS ≥ 140ms for men, ≥130ms for women and mid QRS notching/slurring in ≥2 contiguous leads). Reverse remodeling was assessed at 6 months with echocardiography. Response was defined as ≥15% improvement in LV end systolic volume. Results: These patients were aged 66.1±11.7 years, 83% were male, and 45% had an ischaemic etiology. On ECG analysis 83% had strict LBBB. In the strict LBBB group the SDI was 12.3±5.2% where as in the traditional LBBB group it was 6.7±2.5% (p=0.005). Presence of an ischaemic aetiology had no impact on SDI (p=0.216). Linear regression of SDI vs. amount of remodeling (change in LVESV) generates a regression coefficient of 2.02 (p=0.01) and a correlation coefficient of R=0.49 (p=0.01). ROC analysis determines the optimum SDI cut-off for response as 10% with an area under the curve of 0.797, a sensitivity of 81% and a specificity of 79%. Conclusion: In patients with LBBB selected for CRT under current guidance the presence of strict LBBB predicts increased mechanical dyssynchrony demonstrated as SDI with cine MRI. Presence of mechanical dyssynchrony defined as an SDI ≥10% is a good predictor of volumetric response to CRT in this cohort. ![Graphic][1] [1]: /embed/inline-graphic-1.gif

Evaluation of plasma brain natriuretic peptid levels in patients with isolated left bundle branch block and preserved left ventricular systolic function

Introduction and aim: According to our knowledge, no clinical research on plasma brain natriuretic peptid (BNP) levels in patients with isolated left bundle branch block (LBBB) and in the range of plasma BNP level of normal population is found. We studied the effect of isolated LBBB on plasma BNP levels in patients with isolated LBBB and preserved left ventricular (LV) systolic function having no signs of heart failure according to the clinical and biochemical criteria. Method: This study was carried out by measuring plasma BNP levels in the patients who were diagnosed with isolated LBBB and normal LV ejection fraction (LVEF) and had normal coronary angiography. Total 8432 patients who applied to our clinic with various reasons were screened and 378 patients with LBBB were detected. People who are higher increases than in the range of plasma BNP level of normal population (0-100 pg/mL) were excluded from this study. Finally 42 patients with isolated LBBB who met inclusion and exclusion criteria. Additionally, 30 healthy people with normal ECG and echocardiography were included in the study. All subjects (n=72) were classified in according to the median value of the plasma BNP levels as low BNP group (BNP≤14.6 pg/mL) and high BNP group (BNP>14.6 pg/mL). Results: Mean plasma BNP level was higher in isolated LBBB group than in the control group (30.16±22.04 pg/mL vs 15.81±14.24 pg/mL, p=0.003). LVEF was lower in isolated LBBB group than in the control group (58.1±4.3% vs 62.6±4.9%, p=0,001). Acording to the control group, left atrial diameter and interventricular septal thickness increased in isolated LBBB (p<0.05, p<0.01 respectively). Plasma BNP levels showed a significantly positive correlation with age (r:0.35, p=0.002) and QRS duration (r:0.39, p=0.001). Logistic regression analysis showed that isolated LBBB (OR, 3.91 [95% CI,1.08 - 14.16], p= 0.038) and age (OR, 1.10 [95% CI,1.04 - 1.16], p= 0.001) independently effect plasma BNP level. Conclusion: This study shows that plasma BNP level increases in patients with isolated LBBB and preserved LV systolic function. Determining plasma BNP levels in asymptomatic individuals with isolated LBBB can contribute to the pre-detection of subclinical LV dysfunctions also in the range of plasma BNP level of normal population.

036 COMPARISON OF CLINICAL CHARACTERISTICS AND OUTCOMES IN PATIENTS WITH LEFT BUNDLE BRANCH BLOCK VERSUS ST ELEVATION MYOCARDIAL INFARCTION REFERRED FOR PRIMARY PCI

<h3>Aims</h3> Current national and international guidelines continue to recommend activation of the primary percutaneous coronary intervention (PPCI) pathway in patients presenting with chest pain and presumed new-onset left bundle branch block (LBBB). Previous research has suggested that a lower proportion of patients presenting with LBBB require emergency intervention. In this study we have compared baseline clinical characteristics, angiographic findings and subsequent outcome in patients with LBBB versus ST-elevation myocardial infarction (STEMI) referred to our tertiary centre for PPCI. <h3>Methods</h3> All patients accepted for PPCI within the period of September 2009 to November 2011 were included in the study. Patient data obtained from our Cardiac Services Database System (Phillips CVIS) were analysed and angiographic images reviewed on our Cardiac Image Database (McKesson Horizon). Mortality data were gathered from the Summary Care Record (SCR) database. Statistical comparisons of continuous variables were made by an unpaired t test. Categorical variables were compared using the χ² test. A p value of &lt;0.05 was considered to indicate statistical significance. <h3>Results</h3> During the study period, 1875 patients were referred for PPCI of whom 155 (8.3%) had LBBB. Compared with STEMI, patients with LBBB were significantly older, more likely to be female and have prior history of MI and CABG (table&nbsp;1). Patients with LBBB had similar door-to-balloon (DTB) and call-to-balloon (CTB) times. PCI was performed in 40 (26%) patients with LBBB although an acutely occluded culprit vessel was found in only 19 (12.2%) patients (table&nbsp;2). Furthermore, 85 (54.8%) patients had non-flow limiting coronary artery disease and of those with significant disease 12 (7.7%) patients required CABG (figure&nbsp;1). Overall, an acute coronary syndrome (defined as ischaemic chest pain with positive troponin) was confirmed in only 67 (43.2%) of patients presenting with LBBB. 30-day mortality was similar between LBBB and STEMI patients (table&nbsp;2). However, during a mean follow-up period of 2.1 years, overall mortality was significantly higher in the LBBB group compared to STEMI (HR 2.01, 95% CI 1.26 to 3.20) (figure&nbsp;2). <h3>Conclusions</h3> Our study shows that, in contrast to STEMI, only a small proportion of patients presenting with chest pain and LBBB had an acutely occluded coronary artery. Although short-term mortality was similar between the two groups, long-term outcome was significantly worse in patients with LBBB. Further work is needed to identify those patients presenting with LBBB who are most likely to have an acute coronary occlusion, in order to facilitate the appropriate use of emergency coronary angiography and PPCI.

Assessing Coronary Artery Disease in Patients With Anginal Chest Pain and Left Bundle Branch Block

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

Risk stratification and prognostic assessment by myocardial perfusion-gated SPECT in patients with left bundle-branch block and low-intermediate cardiac risk

In high-risk patients with left bundle-branch block (LBBB), functional but not perfusion parameters yield incremental prognostic information. The aim of our study was to evaluate the prognostic value of gated single photon emission computed tomography (SPECT) in low-intermediate risk LBBB patients. One hundred seventy-six subjects underwent stress-rest dual-day protocol 99mTc sestamibi-gated SPECT and were dichotomized in two groups: without LBBB (Group 1, n = 86) and with LBBB (Group 2, n = 90). Patients were followed for 32 ± 18 months. Cox regression multivariate analysis was used to determine which variable was the best predictor of cardiac event. Event-free survival curves were computed by Kaplan-Meier method. Myocardial perfusion scintigraphy was abnormal in 32 and 60 patients for Groups 1 and 2, respectively (37 vs. 67 %, p < 0.001). In Groups 1 and 2, the mean summed stress score (SSS) was 3.7 ± 5.6 versus 6.7 ± 6.4, while the mean summed difference score (SDS) was 1.6 ± 2.5 versus 2.7 ± 3.3 (both p < 0.005); therefore 34 % of patients in Group 1 and 53 % of those in Group 2 presented myocardial ischemia. All functional parameters were significantly different between the two subsets (all p < 0.005). Follow-up was completed in 161 patients (92 %); 10 events occurred in Group 1 and 20 in Group 2 (14 vs. 25 %). The event-free survival was significantly higher in patients with normal than in those with abnormal scan (85 vs. 63 %, p < 0.005); moreover, the prognosis of patients with LBBB was significantly worse. At multivariate analysis, SDS was found to be the only independent predictor of cardiac events both in all patients and in LBBB population (HR 3.08, and HR 4.99, p < 0.05). This is the first study to assess the prognostic value of gated SPECT in patients with LBBB and low-intermediate cardiac risk. Both perfusion and functional data obtained by gated SPECT are different between patients with and without LBBB. However, SDS is the only predictor of events. Thus, the amount of reversible ischemia at gated SPECT has a discriminative power in stratifying the cardiac risk of LBBB population.

Diagnostic and prognostic value of gated myocardial perfusion single-photon emission computed tomography in low-risk patients with left bundle-branch block

The abnormal left ventricular activation pattern in patients with a left bundle-branch block (LBBB) frequently induces myocardial perfusion defects, decreasing the specificity of noninvasive coronary-risk stratification with stress testing. We assessed the diagnostic and prognostic impact of gated single-photon emission computed tomography (SPECT) in low-risk patients with LBBB. A total of 114 patients underwent dual-day protocol Tc-99m sestamibi gated SPECT and were divided into two subsets: without LBBB (group 1, n = 57) and with LBBB (group 2, n = 57). Sixty-eight (60%) patients had negative coronary angiography and 46 (40%) were at a low risk for coronary artery disease. The variables incorporating the extent and severity of perfusion defects were calculated: summed stress score, summed rest score and summed difference score, end-diastolic volume (EDV), end-systolic volume (ESV), and left ventricular ejection fraction. The mean variations in EDV and ESV were computed as follows: rest volume-poststress volume. Cardiac events were classified as major and minor. Gated SPECT was positive in eight (14%) patients of group 1 and 33 (58%) patients of group 2 (P<0.001). The summed stress score was significantly higher in group 2 than in group 1 (4.7 ± 4.8 vs. 0.9 ± 1.8, P<0.001); similarly, EDV and ESV were significantly higher in LBBB patients (P<0.05 in both). The mean variation in EDV was -2.21 ml for group 1 and 1.32 ml for group 2 (P<0.05). After a mean follow-up period of 32 ± 19 months, cardiac events occurred in 22 (23%) patients, six of group 1 and 16 of group 2 (12 vs. 35%, P<0.01). Functional and perfusion parameters obtained by gated SPECT are different between patients with and without LBBB. In LBBB patients, the decrease in EDV between rest and poststress could be considered an early marker of diastolic dysfunction that might anticipate left ventricular ejection fraction reduction and may have an impact on prognosis.

ORAL PRESENTATION

ORAL PRESENTATION

Vectorcardiographic and electrocardiographic criteria to distinguish new and old left bundle branch block

There are no established criteria to differentiate new from old left bundle branch block (LBBB). This complicates management of patients with LBBB and suspected acute coronary syndrome. The purpose of this study was to develop electrocardiographic (ECG) criteria to differentiate new and old LBBB. All LBBB tracings (n = 3,706) in a hospital ECG database were retrieved. New (<24 hours, n = 39) and old (>24 hours, n = 1,760) LBBB tracings were identified. QRS and T-wave amplitudes, directions, and durations were measured digitally. Vectorcardiograms were reconstructed from 12-lead ECGs using inverse Dower transform and analyzed with Cardio3KG software. Receiver operator characteristic (ROC) curves were used to develop decision rules to distinguish new and old LBBB. The new LBBB group had larger T-vector magnitude (1.20 +/- 0.07 vs. 0.71 +/- 0.01 mV), smaller QRS vector magnitude (2.13 +/- 0.12 vs. 2.47 +/- 0.02 mV), and a lower QRS/T vector magnitude ratio (QRS/T; 1.79 +/- 0.03 vs. 3.92 +/- 0.04) compared with the old LBBB group (mean +/- standard error of the mean, P <.001). The ratio of deepest S to largest T wave in precordial leads (Max S/T) was significantly smaller in the new compared with in the old LBBB group (1.66 +/- 0.05 vs. 3.54 +/- 0.08; P <.001). A decision rule using QRS/T <2.25 and Max S/T <2.5 had 100% sensitivity and 96%-68% specificity in diagnosing new LBBB, including subsets of patients with tachycardia and ischemia. QRS/T and Max S/T allow accurate discrimination between new and old LBBB suitable for both computerized and manual analysis. If confirmed in prospective studies, this finding can improve management of patients with chest pain and LBBB.

Comparative Mechanical Activation Mapping of RV Pacing to LBBB by 2D and 3D Speckle Tracking and Association With Response to Resynchronization Therapy

The goals of this study were to compare patterns of mechanical activation in patients with chronic right ventricular (RV) pacing with those with left bundle branch block (LBBB) using 2-dimensional and novel 3-dimensional speckle tracking, and to compare ejection fraction (EF) response and long-term survival after cardiac resynchronization therapy (CRT). Several randomized CRT trials have excluded patients with chronic RV pacing, and current guidelines for CRT include patients with intrinsically widened QRS, typically LBBB. We studied 308 patients who were referred for CRT: 227 had LBBB, 81 were RV paced. Dyssynchrony was assessed by tissue Doppler, routine pulsed Doppler, and 2-dimensional speckle-tracking radial strain. 3D strain was assessed using speckle tracking from a pyramidal dataset in a subset of 57 patients for mechanical activation mapping. Survival after CRT was compared with survival in a group of 46 patients with attempted, but failed, CRT. Patients with chronic RV pacing and LBBB had similar intraventricular dyssynchrony, with opposing wall delays by tissue Doppler of 82 +/- 45 ms versus 87 +/- 63 ms and anteroseptum-to-posterior delays by speckle tracking of 225 +/- 142 ms, versus 211 +/- 107 ms, respectively. RV-paced patients, however, had greater interventricular dyssynchrony: 44 +/- 24 ms versus 35 +/- 21 ms (p < 0.01), which correlated with their greater QRS duration (p < 0.001). Sites of latest mechanical activation were most often posterior or lateral in both groups, but RV-paced patients had sites of earliest activation more often from the inferior-septum and apex (p < 0.05). EF response was similar in RV-paced and LBBB groups, and survival free from transplantation or mechanical support after CRT was similarly favorable as compared with failed CRT patients over 5 years (p < 0.01). RV-paced patients, when compared with LBBB patients, had similar dyssynchronous patterns of mechanical activation and greater interventricular dyssynchrony. Importantly, RV-paced patients had similar EF response and long-term outcome as those with LBBB, which supports their candidacy for CRT.

Circumferential myocardial strain in cardiomyopathy with and without left bundle branch block.

BackgroundCardiac resynchronization therapy (CRT) has been shown to decrease mortality in 60-70% of advanced heart failure patients with left bundle branch block (LBBB) and QRS duration > 120 ms. There have been intense efforts to find reproducible non-invasive parameters to predict CRT response. We hypothesized that different left ventricular contraction patterns may exist in LBBB patients with depressed systolic function and applied tagged cardiovascular magnetic resonance (CMR) to assess circumferential strain in this population.MethodsWe determined myocardial circumferential strain at the basal, mid, and apical ventricular level in 35 subjects (10 with ischemic cardiomyopathy, 15 with non-ischemic cardiomyopathy, and 10 healthy controls). Patterns of circumferential strain were analyzed. Time to peak systolic circumferential strain in each of the 6 segments in all three ventricular slices and the standard deviation of time to peak strain in the basal and mid ventricular slices were determined.ResultsDyskinesis of the anterior septum and the inferior septum in at least two ventricular levels was seen in 50% (5 out of 10) of LBBB patients while 30% had isolated dyskinesis of the anteroseptum, and 20% had no dyskinesis in any segments, similar to all of the non-LBBB patients and healthy controls. Peak circumferential strain shortening was significantly reduced in all cardiomyopathy patients at the mid-ventricular level (LBBB 9 ± 6%, non-LBBB 10 ± 4% vs. healthy 19 ± 4%; both p < 0.0001 compared to healthy), but was similar among the LBBB and non-LBBB groups (p = 0.20). The LBBB group had significantly greater dyssynchrony compared to the non-LBBB group and healthy controls assessed by opposing wall delays and 12-segment standard deviation (LBBB 164 ± 30 ms vs. non-LBBB 70 ± 17 ms (p < 0.0001), non-LBBB vs. healthy 65 ± 17 ms (p = 0.47)).ConclusionsSeptal dyskinesis exists in some patients with LBBB. Myocardial circumferential strain analysis enables detailed characterization of contraction patterns, strengths, and timing in cardiomyopathy patients with and without LBBB.

Cardiac Resynchronization Therapy in Non-Left Bundle Branch Block Morphologies

In select patients with systolic heart failure, cardiac resynchronization therapy (CRT) has been shown to improve quality of life, exercise capacity, ejection fraction (EF), and survival. Little is known about the response to CRT in patients with right bundle branch block (RBBB) or non-specific intraventricular conduction delay (IVCD) compared with traditionally studied patients with left bundle branch block (LBBB). We assessed 542 consecutive patients presenting for the new implantation of a CRT device. Patients were placed into one of three groups based on the preimplantation electrocardiogram morphology: LBBB, RBBB, or IVCD. Patients with a narrow QRS or paced ventricular rhythm were excluded. The primary endpoint was long-term survival. Secondary endpoints were changes in EF, left ventricular end-diastolic and systolic diameter, mitral regurgitation, and New York Heart Association (NYHA) functional class. Three hundred and thirty-five patients met inclusion criteria of which 204 had LBBB, 38 RBBB, and 93 IVCD. There were 32 deaths in the LBBB group, 10 in the RBBB, and 27 in the IVCD group over a mean follow up of 3.4 +/- 1.2 years. In multivariate analysis, no mortality difference amongst the three groups was noted. Patients with LBBB had greater improvements in most echocardiographic endpoints and NYHA functional class than those with IVCD and RBBB. There is no difference in 3-year survival in patients undergoing CRT based on baseline native QRS morphology. Patients with RBBB and IVCD derive less reverse cardiac remodeling and symptomatic benefit from CRT compared with those with a native LBBB.

Cardiac Resynchronization Therapy in Patients With Intrinsic and Right Ventricular Pacing-Induced Left Bundle Branch Block Pattern

We studied 95 consecutive patients, mean age 70 years, who received cardiac resynchronization therapy (CRT) for class III or IV heart failure with a left ventricular (LV) ejection fraction < or =35% and a QRS duration > or =120 ms. Sixty-seven patients had intrinsic left bundle branch block (LBBB) (group 1), and 28 patients had right ventricular pacing-induced LBBB (group 2). The time difference (TPW-TDI) between onset of QRS to the end of LV ejection by pulsed wave Doppler and onset of QRS to the end of systolic wave in the basal segment with greatest delay by tissue Doppler imaging was measured before CRT and at the last follow-up after CRT. TPW-TDI >50 ms was defined as left ventricular mechanical dyssynchrony. A positive response to CRT was defined as LV volume at end-systole decreasing > or =15% after CRT. The percentage of CRT responders in group 2 was significantly greater than that in group 1 (68% versus 42%, P = 0.04) during follow-up of 16 months. After adjusting for age, gender, and clinical features, this pattern of CRT response persisted (P = 0.008). Similarly, there was a greater reduction in QRS duration in group 2 (178 ms) after CRT versus 154 ms for group 1, P = 0.01. There was no significant difference in TPW-TDI between the 2 groups at baseline or at follow-up. There was no significant difference in mortality (15% versus 14%) and Kaplan-Meier survival plot during follow-up. Patients with heart failure and right ventricular pacing-induced LBBB have a better response rate to CRT than patients with intrinsic LBBB. The change in left ventricular mechanical dyssynchrony after CRT was similar in these 2 groups of patients.

Long-Term Clinical Response of Cardiac Resynchronization After Chronic Right Ventricular Pacing

Chronic right ventricular (RV) pacing might elicit unpredictably deleterious effects on left ventricular (LV) function similar to that of native left bundle branch block (LBBB). The objective of the present study was to evaluate the clinical and echocardiographic response to cardiac resynchronization therapy after years of chronic RV pacing. In this prospective observational study of 284 consecutive patients, cardiac resynchronization therapy was performed in 194 patients (68%) with a native LBBB and in 90 patients (32%) with a pacing-induced LBBB after chronic RV pacing (upgraded group). Echocardiographic and clinical parameters were evaluated in both groups at baseline and during 2 years of follow-up. The clinical response was defined as survival with improvement of > or =1 in the New York Heart Association class without heart failure hospitalization. Reverse LV remodeling was defined as LV end-systolic volume reduction of > or =15%. At baseline, the New York Heart Association class, quality of life, and exercise capacity were comparable but the LV ejection fraction was significant greater and the LV volumes were significant smaller in the upgraded group. Changes with time in the clinical parameters, echocardiographic parameters, and clinical response were not significantly different between the 2 groups. Reverse LV remodeling was observed in 86% in the upgraded group versus 78% of the native LBBB group after 1 year (p = 0.39). Survival was not significantly different between the 2 groups. In conclusion, comparable clinical and echocardiographic improvement was seen when resynchronization therapy was applied in patients with preceding chronic RV pacing compared with patients with a native LBBB.

Image quality of 16-slice computed tomography coronary angiography in patients with complete left bundle branch block

Noninvasive diagnosis of coronary artery disease in patients with left bundle branch block is challenging. Multislice computed tomography can be useful in this population; however, quality of images depends on the patterns of myocardial contractions. We investigated the influence of left bundle branch block on image quality of multislice computed tomography coronary angiography. Multislice computed tomography coronary angiography was performed in 30 patients with left bundle branch block and 30 patients without conduction disturbances. Image quality of each coronary segment was visually assessed and rated on a five-point scale (1=highest quality). Average image quality score in the best cardiac cycle phase did not differ significantly between groups (1.71+/-0.59 in the left bundle branch block group vs. 1.60+/-0.57 in the control group, P=0.46). In the left bundle branch block group, a significantly lower image quality score was observed in end-systolic cardiac phase (2.67+/-0.6 vs. 2.22+/-0.65 in the control group, P=0.007), whereas no difference was demonstrated in mid-diastolic phase (1.73+/-0.6 vs. 1.69+/-0.66 in the control group, P=0.81). After image assessment in multiple cardiac phases, an increase in image quality score was higher in the left bundle branch block than in the control group (0.2+/-0.17 vs. 0.11+/-0.14, P=0.003). A negative correlation was observed between image quality score and both the heart rate and heart rate variability in both groups (P<0.001). A nonsignificantly lower overall image quality of multislice computed tomography coronary angiography was demonstrated in the left bundle branch block group. In the presence of left bundle branch block, image quality in the end-systolic phase was significantly lower. Image assessment in multiple phases increased overall image quality and is therefore advisable in patients with left bundle branch block. Increased heart rate and heart rate variability worsened image quality in both groups.

Relation of Left bundle branch block in type II diabetes mellitus with left ventricular systolic function and hemoglobin A1C

SUMMARY The aim of the study was evaluation of left bundle branch block (LBBB) as a marker of cardiovascular involvement in diabetes mellitus (DM) patients by examining left ventricular systolic function and hemoglobin A 1c . Data on 25 DM patients with LBBB were compared with data on 25 DM patients without LBBB and 25 non-DM patients with LBBB. The mean age of patients in DM with LBBB, DM without LBBB, and non-DM with LBBB groups was 62.2±9.4, 62±6.3 and 63.6±8 years, respectively (p=NS). There were 72%, 65/4% and 50% of female patients, respectively (p=NS). Left ventricular ejection fraction in DM with LBBB was significantly lower than in DM without LBBB and non-DM with LBBB (32.8±10.8 vs. 58.9±7.7and 41±12; p<0.002). Left ventricular enddiastolic diameter was significantly higher in DM with LBBB than in DM without LBBB and non-DM with LBBB (61.6±7.1 vs. 50.6±3.7 and 58±10.1 mm;

Similar Degree in Mechanical Left Ventricular Dyssynchrony Between Right Ventricular Outflow Tract and Right Ventricular Apical Pacing: A Strain Doppler Imaging Study

Background and Objectives: Long-term right ventricular (RV) apex pacing has been associated with left ventricular (LV) systolic dysfunction. However, pacing in the RV outflow tract (RVOT) is associated with a narrower QRS duration and may have a more normal LV activation in comparison to RV apical (RVA) pacing. We hypothesized that RVOT pacing is associated with less mechanical dyssynchrony compared to RVA pacing and that it also more closely resembles mechanical activation in normal controls with a narrow QRS. Subjects and Methods: We studied 9 patients with RV pacing, 9 with left bundle branch block (LBBB), and 15 normal controls with a narrow QRS. In the RV pacing group, we paced from the RVA and RVOT. At the end of each pacing train, we obtained echocardiographic images in the apical 4- and 2-chamber views and obtained the following parameters: the compression/expansion crossover point (CEP) for myocardial strain and the time from QRS onset to the CEP in the strain image. The degree of dyssynchrony was evaluated using the dispersion and standard deviation of CEP times in 12 segments of the LV. Results: Significant dyssynchrony was observed in the RVOT pacing group compared to the group with normal QRS. No significant difference was observed in LV mechanical dyssynchrony among the RVOT pacing, RVA pacing, and LBBB groups. Conclusion: RVOT pacing is associated with significant LV dyssynchrony. Although the RVOT has been recommended as an alternative site for pacing, this approach may have adverse effects on long-term LV function. (Korean Circ J 2008;38:590-595)

The Effect of Isolated Left Bundle Branch Block on the Myocardial Velocities and Myocardial Performance Index

This study was planned in order to investigate the effect of left bundle branch block (LBBB) on myocardial velocities obtained by tissue Doppler echocardiography (TDE) and myocardial performance index (MPI). Subjects with LBBB (n = 61) and age-matched healthy subjects (n = 60) were enrolled in the study. Left ventricular (LV) ejection fraction (EF), mitral inflow velocities (E-wave and A-wave), isovolumetric contraction and relaxation time (ICT and IRT), ejection time (ET), and flow propagation velocity (Vp) were measured by conventional echocardiography. Systolic velocity (Sm), early and late diastolic velocities (Em and Am) and time intervals were measured by TDE. MPI was calculated by the formula (ICT + IRT)/ET. LVEF and mitral E/A ratio were similar in both groups. Vp was lower in the LBBB group than in the control group, whereas the E/Em and the E/Vp ratio was higher. LV Sm and Em/Am ratio were lower in LBBB group. Right ventricular Sm and Em/Am ratio were similar in both groups. LV mean and RV MPI were significantly increased in LBBB group. These findings obtained by TDE show that isolated LBBB impairs the ventricular functions. Both of the LV and RV dysfunctions shown by the new parameters may contribute to increased morbidity and mortality in cases with isolated LBBB.

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

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. 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. 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). 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). 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.

Gated spect myocardial perfusion scintigraphy for identifying septal perfusion artifacts in left bundle branch block.

To determine the role of gated Single Photon Emission Computed Tomography (SPECT) for accurate assessment of myocardial perfusion scintigraphy (MPS) of patients with left bundle branch block (LBBB). Analytical study. Punjab Institute of Nuclear Medicine (PINUM), Faisalabad, Pakistan, from June 2002 to April 2003. MPS data of patients with LBBB was analyzed. Resting gated SPECT MPS was performed after an injection of 740 MBq 99mTc-MIBI in 10 normal and 25 subjects with LBBB (with low probability of coronary artery disease). Visual and quantitative analyses were done on non-gated (NG), end diastolic (ED), end systolic (ES) images. Calculations included septal to lateral wall ratio (SLR), myocardial thickening (MT=% increase in counts during systole) at end systolic phase and myocardial thickening at peak level (% peak MT). Septal hypoperfusion was noted in 19 (76%) patients on NG images and in only 1 (4%) patient on gated SPECT ED images. On NG images of LBBB group, SLR was lower than in controls (0.68+/-0.07 vs. 0.87+/-0.05, p<0.001). SLR of LBBB patients approached to that of control group in gated SPECT ED data (0.86+/-0.06 vs 0.88+/-0.06, p=ns). Myocardial thickening at ES for septum was markedly lower in LBBB group than in controls (21.83%+/-10.86 vs. 66.32%+/-20.15, p<0.001). In patients with LBBB, reduced septal thickening results in artifactual septal perfusion defects. Gating the perfusion scintigraphy and reporting perfusion status on end diastolic frames in LBBB patients can eliminate these artifacts.

Assessment of cardiac function and synchronicity in subjects with isolated bundle branch block using Doppler imaging

Using tissue Doppler imaging and conventional echocardiographic technique, we examined the cardiac function and synchronicity in individuals with isolated right bundle branch block (RBBB) or left bundle branch block (LBBB) and assessed the relationship between QRS duration and synchronicity. Subjects with isolated RBBB (n = 20), LBBB (n = 10) and normal controls (n = 20) were studied with conventional echocardiography and tissue Doppler imaging. The difference between aortic and pulmonary preejection intervals was defined as interventricular delay. Parameters in septum and lateral wall were measured using tissue Doppler imaging, including peak sustained systolic velocity (S(M)), peak early (E(M)) and late (A(M)) diastolic velocities as well as time to peak velocities (T(S), T(E) and T(A)). Subjects with LBBB had lower S(M) and longer T(S) than did the RBBB and control groups (P < 0.05, P < 0.001 respectively). A significant difference was observed in E(M), being the lowest in the LBBB and the highest in the control group (P < 0.05). Moreover, T(E) was longer in the LBBB group compared with the other two groups (P < 0.001). Both A(M) and T(A) were similar among three groups (P > 0.05). In the bundle branch block groups, one ventricle lagged about 40 ms behind the other. A significant correlation was found between interventricular delay and QRS duration (r = 0.713, P < 0.001). Cardiac ventricles were not well synchronized with one ventricle lagging about 40 ms behind the other in subjects with LBBB or RBBB, even though only LBBB group showed barely perceptible, impaired cardiac function. In addition, QRS duration and cardiac asynchronicity were positively correlated.