Presence Of Left Bundle Branch Block Research Articles

Left ventricular rotational dyssynchrony before cardiac resynchronization therapy: a step forward into ventricular mechanics.

Heart failure patients show impaired left ventricular rotation and twist. In patients undergoing cardiac resynchronization therapy (CRT) significance of preimplant left ventricular rotational timing between different ventricular regions is unknown. We thoroughly evaluated, in patients eligible for CRT, baseline left ventricular rotational mechanics, also assessing segmental rotational timing, and investigated whether the presence of rotational dyssynchrony may be associated with echocardiographic response. By two-dimensional speckle-tracking echocardiography, baseline peak apical and basal rotation, peak twist, and time-related parameters, such as delays between opposite segments at base and apex, were assessed in 55 CRT patients and 11 healthy participants. At 6 months, 30 (54%) patients were echocardiographic responders. Left ventricular rotation and twist had no association with response. All time-related parameters were significantly altered in CRT patients. Maximum basal and apical segments delay, and anteroseptal-posterior delays at base and apex, were longer in responders than in nonresponders (P < 0.05 for all), regardless of the presence of left bundle branch block (LBBB) and QRS duration. At multivariable analysis, apical anteroseptal-posterior delay resulted as independently associated with response [odds ratio (OR): 1.022 (1.007-1.038); P = 0.004]. A cut-off value of 97.5 ms for apical anteroseptal-posterior delay predicted response with 96% specificity and 57% sensitivity (AUC = 0.83). Magnitude of left ventricular reverse remodeling was significantly related to apical anteroseptal-posterior delay (P = 0.001). In heart failure patients eligible for CRT, left ventricular rotational timing is altered. Dyssynchrony in rotational mechanics shows a specific pattern in responders regardless of the presence of LBBB. Apical anteroseptal-posterior rotational delay is independently associated with left ventricular reverse remodeling.

Left bundle branch block, chest pain and catheterization laboratory activation: an unavoidable cascade reaction?

Identification of acute myocardial infarction (AMI) in the presence of left bundle branch block (LBBB) remains challenging.European guidelines recommend prompt reperfusion therapy in patients with suspected ongoing myocardial ischemia and new or presumably new LBBB, whereas AHA/ACC guidelines state that LBBB should not be considered diagnostic of AMI in isolation.Sgarbossa criteria and their recent modified version with the introduction of ST/S ratio can be helpful in this setting. A clinical–instrumental algorithm to manage suspected AMI in the presence of LBBB has been recently proposed. We present five paradigmatic clinical cases.

Prognostic Impact of QRS Axis Deviation in Patients Treated With Cardiac Resynchronization Therapy.

QRS duration and morphology are currently recognized as recommended criteria for the selection of CRT candidates. It has recently been shown that patients with left bundle branch block (LBBB) derive substantial clinical benefit from CRT. The aim of this study is to investigate the prognostic impact of QRS axis deviation (AD) in HF patients with LBBB undergoing CRT. We retrospectively evaluated 707 HF patients with LBBB who underwent CRT at five centers. Baseline QRS axis was defined as normal (NA: -30° to 90°), right axis deviation (RAD: 90° to 180°) and left axis deviation (LAD: <-30°). The primary endpoint was a composite of all cause death/HF hospitalization. The risk of endpoint by AD was evaluated with both Kaplan-Meier and Cox proportional hazard analysis. Among 707 patients (73% M, median age: 71 [62,77] years), 323 (46%) had NA, 359 (51%) LAD, and 25 (3.5%) RAD. Baseline clinical characteristics were similar between the three groups. Over a mean follow-up of 32 ± 25 months, 141 deaths occurred (21%) and 36% (n = 255) met with the composite endpoint. A significantly higher proportion of RAD patients (52%) reached the endpoint (LAD 40%, NA 30%). KM analysis showed that RAD and LAD patients had worse event free survival and in multivariate analysis both LAD (HR: 1.40; 95% CI: 1.05-1.86; P = 0.021) and RAD (HR: 2.49; 95% CI: 1.31-4.74; P = 0.005) were independently associated with worse clinical outcome. Right or left axis deviation in the presence of LBBB in HF patients undergoing CRT are independent predictors of poor prognosis.

Abstract 14660: Effect of PR Interval on Mortality Reduction With Cardiac Resynchronization Therapy - A Secondary Analysis of the COMPANION Trial

Introduction: Prolonged PR intervals may impair atrioventricular mechanical coupling and adversely affect cardiac performance. We hypothesize that patients with advanced systolic heart failure, wide QRS complexes, and prolonged PR intervals will have improved survival from cardiac resynchronization therapy with defibrillator (CRT-D) regardless of whether left bundle branch block (LBBB) or non-LBBB is present. Methods: Patients enrolled in the optimal pharmacologic therapy (OPT) and CRT-D arms of the COMPANION trial were included in a multivariable Cox model of all-cause mortality as a function of presence of LBBB and value of PR interval at baseline. Hazard ratios representing the mortality reduction for CRT-D versus OPT were estimated together with pointwise 95% confidence intervals (CIs). Results: A total of 308 OPT and 595 CRT-D patients were included in the analysis. In both the LBBB (n=648) and non-LBBB (n=255) subgroups, the mortality reduction associated with CRT-D compared to OPT was greater with increasingly prolonged baseline PR interval (Figure 1, p=0.02 for each subgroup). Hazard ratios for CRT-D versus OPT (with 95% CIs) for PR intervals of 200ms and 250ms were 0.51 [0.35,0.74] and 0.30 [0.18,0.50] respectively for the LBBB subgroup, and 0.86 [0.50,1.5] and 0.39 [0.18,0.86] respectively for the non-LBBB subgroup. For non-LBBB patients with PR interval ≤200ms, there was no evidence of mortality benefit with CRT-D (p=0.60). Conclusions: In patients with advanced systolic heart failure, wide QRS complexes, and prolonged PR intervals, restoration of atrioventricular mechanical coupling with CRT-D may improve survival in both LBBB and non-LBBB recipients. In patients with non-LBBB, a benefit from CRT-D may occur in patients with prolonged PR intervals. Figure 1: Risk for all-cause mortality by hazard ratios stratified according to PR interval quartiles.

BUNDLE BRANCH BLOCKS AND OUTCOMES IN STEMI PATIENTS TREATED WITH PRIMARY PCI

Bundle branch blocks (BBB) are associated with increased mortality in ST-elevation myocardial infarction (STEMI) patients treated with fibrinolysis. We assessed the relationship between BBB in STEMI patients treated with primary percutaneous coronary intervention (PCI) and acute and long-term outcomes. A prospective cohort of 3829 patients undergoing primary PCI for treatment of STEMI from Jan 1, 2002 to Dec 31, 2012 was analyzed. Old ECG’s from 1996 until presentation were obtained for patients with BBB to determine if the BBB previously existed. For patients with left bundle branch block (LBBB), only those with inappropriately concordant ST changes were included. Mortality data was obtained through hospital and provincial mortality records. Using patients with a QRS interval of < 120ms as a reference, crude and multivariate adjusted odds ratios (ORs) for ventricular arrhythmias during primary PCI, intra-aortic balloon pump (IABP) use, and for 30-day and 1-year mortality were calculated for different BBB types. For patients with RBBB (n=259), the ORs for 30-day and 1-year mortality were 7.73 (95%CI 5.35, 11.16) and 5.78 (4.16-8.05), respectively; and 6.03 (4.09-8.90) and 4.44 (3.12-6.32) after adjustment. Presence of RBBB was associated with malignant arrhythmias during catheterization (adjusted OR 3.12, 95%CI 2.00-4.87) and IABP use (adjusted OR 4.15, 95%CI 3.02-5.72). New persistent RBBB and transient RBBB were both associated with increased 30-day and 1-year mortality, whereas pre-existing RBBB was not. For patients with LBBB and inappropriate ST-segment concordance (n=55), the OR for 30-day and 1-year mortality were 11.31 (95%CI 5.97-21.40) and 8.75 (95%CI 4.40-17.40), respectively; and 11.46 (95%CI 6.47-20.28) and 8.86 (95%CI 4.77-16.45) after adjustment. In patients treated directly with PCI, the presence of LBBB with inappropriate ST-segment concordance or development of a new RBBB in STEMI is predictive of increased mortality. The timing of RBBB is associated with risk.

Impact of ECG findings and process-of-care characteristics on the likelihood of not receiving reperfusion therapy in patients with ST-elevation myocardial infarction: results of a field evaluation.

BackgroundMany patients with ST-elevation myocardial infarction (STEMI) do not receive reperfusion therapy and are known to have poorer outcomes. We aimed to perform the first population-level, integrated analysis of clinical, ECG and hospital characteristics associated with non-receipt of reperfusion therapy in patients with STEMI.Methods and ResultsThis systematic evaluation of STEMI care in 82 hospitals in Quebec included all patients with a discharge diagnosis of myocardial infarction, presenting with characteristic symptoms and an ECG showing STEMI as attested by at least one of two study cardiologists or left bundle branch block (LBBB). Excluding LBBB, an ECG was considered a definite STEMI diagnosis if both cardiologists scored ‘certain STEMI’ and ambiguous if one scored ‘uncertain’ or ‘not STEMI’. Centers were classified according to accessibility to primary percutaneous coronary intervention (PPCI): 1) on-site PPCI; 2) routine transfer for PPCI; 3) varying mix of PPCI transfer and on-site fibrinolysis; and 4) routine on-site fibrinolysis. Of 3730 STEMI/LBBB patients, 812 (21.8%) did not receive reperfusion therapy. In multivariate analysis, likelihood of no reperfusion therapy was a function of PPCI accessibility (odds ratio [OR] for fibrinolysis versus PPCI centers = 3.1; 95% CI: 2.2–4.4), presence of LBBB (OR = 24.1; 95% CI: 17.8–32.9) and an ECG ambiguous for STEMI (OR = 4.1; 95% CI: 3.3–5.1). When the ECG was ambiguous, likelihood of no reperfusion therapy was highest in hospitals most distant from PPCI centers.ConclusionsECG diagnostic ambiguity, LBBB and PPCI accessibility are important predictors of not receiving reperfusion therapy, suggesting opportunities for improving outcomes.

Impact of left bundle branch block on heart rate and its relationship to treatment with ivabradine in chronic heart failure

Left bundle branch block (LBBB) increases morbidity and mortality in heart failure (HF). Heart rate reduction with ivabradine improves outcomes in patients with systolic HF. Therefore, we aimed to analyse the impact of LBBB on outcomes in patients with systolic HF as a function of heart rate, and the relationship between LBBB and the effect of treatment with ivabradine. Patients from the SHIFT (n = 6505) were divided into groups with (n = 912) or without (n = 5593) LBBB at baseline, and according to tertiles of heart rate (70-73, 74-80, and ≥81 b.p.m.). The effect of LBBB, heart rate, and ivabradine on the primary endpoint (cardiovascular death or HF hospitalization) and other endpoints was analysed. LBBB was associated with increases in the primary endpoint by 65%, cardiovascular mortality by 49%, HF hospitalization by 86%, and all-cause mortality by 49% (all P < 0.001). No interaction appeared between the impact of heart rate on outcomes and presence of LBBB (P = 0.83 for the primary endpoint); thus LBBB increases risk for all heart rates. No interaction was apparent in the effect of ivabradine with LBBB or without LBBB. Ivabradine did not increase the prevalence of bradycardia in patients with LBBB. LBBB increases risk in HF patients with heart rates ≥70 b.p.m. in sinus rhythm, unmodulated by heart rate. Ivabradine was safe in LBBB. Its effect was directionally similar to that in patients without LBBB, but did not reach statistical significance, possibly due to lack of power to test this effect because of the small number of LBBB patients.

New ST-segment elevation myocardial infarction criteria for left bundle branch block based on QRS area

BackgroundECG detection of ST-segment elevation myocardial infarction (STEMI) in the presence of left bundle-branch block (LBBB) is challenging due to ST deviation from the altered conduction. The purpose of this study was to introduce a new algorithm for STEMI detection in LBBB and compare the performance to three existing algorithms. MethodsSource data of the study group (143 with acute MI and 239 controls) comes from multiple sources. ECGs were selected by computer interpretation of LBBB. Acute MI reference was hospital discharge diagnosis. Automated measurements came from the Philips DXL algorithm. Three existing algorithms were compared, (1) Sgarbossa criteria, (2) Selvester 10% RS criteria and (3) Smith 25% S-wave criteria. The new algorithm uses an ST threshold based on QRS area. All algorithms share the concordant ST elevation and anterior ST depression criteria from the Sgarbossa score. The difference is in the threshold for discordant ST elevation. The Sgarbossa, Selvester, Smith and Philips discordant ST elevation criteria are (1) ST elevation ≥500μV, (2) ST elevation ≥10% of |S|-|R| plus STEMI limits, (3) ST elevation ≥25% of the S-wave amplitude and (4) ST elevation ≥100μV+1050μV/Ash * QRS area. The Smith S-wave and Philips QRS area criteria were tested using both a single and 2 lead requirement. Algorithm performance was measured by sensitivity, specificity, and positive likelihood ratio (LR+). ResultsAlgorithm performance can be organized in bands of similar sensitivity and specificity ranging from Sgarbossa score ≥3 with the lowest sensitivity and highest specificity, 13.3% and 97.9%, to the Selvester 10% rule with the highest sensitivity and lower specificity of 30.1% and 93.2%. The Smith S-wave and Philips QRS area algorithms were in the middle band with sensitivity and specificity of (20.3%, 94.9%) and (23.8%, 95.8%) respectively. ConclusionAs can be seen from the difference between Sgarbossa score ≥3 and other algorithms for STEMI in LBBB, a discordant ST elevation criterion improves the sensitivity for detection but also results in a drop in specificity. For applications of automated STEMI detection that require higher sensitivity, the Selvester algorithm is better. For applications that require a low false positive rate such as relying on the algorithm for pre-hospital activation of cardiac catheterization laboratory for urgent PCI, it may be better to use the 2 lead Philips QRS area or Smith 25% S-wave algorithm.

Left bundle-branch block: The relationship between electrocardiogram electrical activation and echocardiography mechanical contraction

The relationship between myocardial electrical activation by electrocardiogram (ECG) and mechanical contraction by echocardiography in left bundle-branch block (LBBB) has never been clearly demonstrated. New strict criteria for LBBB based on a fundamental understanding of physiology have recently been independently published for both ECG and echocardiography. The relationship between the 2 modalities and the relation to cardiac resynchronization therapy (CRT) response was investigated. Sixty-six patients with LBBB by conventional criteria had a standard 12-lead ECG and 2-dimensional strain echocardiography performed before CRT implantation. Criteria for LBBB by echocardiography included early termination of contraction in one wall and prestretch and late contraction in opposing wall(s). New strict criteria by ECG included QRS duration ≥140 ms (men) or 130 ms (women), QS or rS in leads V1 and V2, and mid-QRS notching or slurring in ≥2 of leads V1, V2, V5, V6, I, and aVL. Response was defined as >15% decrease in left ventricular end-systolic volume after 6 months. In 64 of 66 patients, ECG analysis was possible. Echo and ECG readings for LBBB presence were concordant in 54 (84%) of 64. Thirty-seven (82%) of 45 patients with LBBB by strict ECG criteria responded to CRT, whereas only 4 (21%) of the 19 patients without LBBB responded (sensitivity 90% and specificity 65%). Thirty-six (95%) of 38 patients with concordance for the presence of LBBB responded to CRT. In patients with concordance for the absence of LBBB, 15 (94%) of 16 did not respond. For the first time, a close relation has been demonstrated between electrical activation by ECG and mechanical contraction by echocardiography. These findings may help identify CRT candidates.

Evaluating strict and conventional left bundle branch block criteria using electrocardiographic simulations

Left bundle branch block (LBBB) is a critical predictor of patient benefit from cardiac resynchronization therapy (CRT), but recent studies suggest that one-third of patients diagnosed with LBBB by conventional electrocardiographic (ECG) criteria may have a false-positive diagnosis. In this study, we tested the hypothesis that recently proposed strict LBBB ECG criteria improve specificity in cases of left ventricular hypertrophy (LVH) /dilatation and incomplete LBBB. We developed five heart models based on a healthy male with increasing degrees of LV hypertrophy and/or dilation. With each model, we simulated six conduction types: normal conduction, four increments of delayed initiation of LV activation (incomplete LBBB), and complete LBBB. Simulated ECGs were evaluated for the presence of LBBB by conventional (LV conduction delay and QRSd ≥120 ms) and strict ECG criteria (LV conduction delay, QRSd ≥140 ms men or ≥130 ms women, and mid-QRS notching in at least two of the leads I, aVL, V1, V2, V5, and/or V6). Both conventional and strict LBBB criteria had 100% sensitivity. However, conventional criteria falsely diagnosed LBBB in cases with LVH + LV dilated 10 mm, LVH or LV dilated 10 mm combined with LV initiation ≥6 ms after the right ventricle (RV), and with LV dilated 5 mm combined with LV initiation ≥12 ms after RV (48% specificity). Strict LBBB criteria resulted in no false positives (100% specificity). New strict LBBB criteria increase the specificity of complete LBBB diagnosis in the presence of LV hypertrophy/dilatation and incomplete LBBB, which is critical for selecting CRT patients.

Noninvasive Electrocardiographic Mapping to Improve Patient Selection for Cardiac Resynchronization Therapy: Beyond QRS Duration and Left Bundle Branch Block Morphology

This study sought to investigate whether noninvasive electrocardiographic activation mapping is a useful method for predicting response to cardiac resynchronization therapy (CRT). One third of the patients appear not to respond to CRT when they are selected according to QRS duration. We performed electrocardiographic activation mapping in 33 consecutive CRT candidates (QRS duration≥120 ms). In 18 patients, the 12-lead electrocardiographic morphology was left bundle branch block (LBBB), and in 15, it was nonspecific intraventricular conduction disturbance (NICD). Three indexes of electrical dyssynchrony were derived from intrinsic maps: right and left ventricular total activation times and ventricular electrical uncoupling (VEU) (difference between the left ventricular [LV] and right ventricular mean activation times). We assessed the ability of these parameters to predict response, measured using a clinical composite score, after 6 months of CRT. Electrocardiographic maps revealed homogeneous patterns of activation and consistently greater VEU and LV total activation time (LVTAT) in patients with LBBB compared with heterogeneous activation sequences and shorter VEU and LVTAT in NICD patients (VEU: 75 ± 12 ms vs. 40 ± 22 ms; p< 0.001; LVTAT: 115 ± 21 ms vs. 91 ± 34 ms; p= 0.03). LBBB and NICD patients had similar right ventricular total activation times (62 ± 30 ms vs. 58 ± 26 ms; p= 0.7). The area under the receiver-operating characteristic curve indicated that VEU (area under the curve [AUC]:0.88) was significantly superior to QRS duration (AUC: 0.73) and LVTAT (AUC: 0.72) for predicting CRT response (p<0.05). With a 50-ms cutoff value, VEU identified CRT responders with 90% sensitivity and 82% specificity whether LBBB was present or not. Ventricular electrical uncoupling measured by electrocardiographic mapping predicted clinical CRT response better than QRS duration or the presence of LBBB.

Incidence and predictors of heart failure hospitalization and death in permanent pacemaker patients: a single-centre experience over medium-term follow-up

The aim of this study was to assess the incidence and clinical predictors of the development of new-onset heart failure (HF) over medium-term follow-up, in patients treated with permanent pacing in daily clinical practice. We retrospectively enrolled all consecutive patients who underwent single- or dual-chamber pacemaker implantation at the study centre. Patients with a left ventricular ejection fraction (LVEF) ≤35% or a prior diagnosis of HF were excluded. Ventricular leads were routinely implanted in the right apex. Pacemakers were implanted in 490 patients with a standard pacemaker indication and LVEF >35%. Left bundle-branch block (LBBB) was reported in 30 (8%) patients, and an LVEF <50% in 64 (13%) patients. During a follow-up of 27 ± 21 months, 32 (7%) patients reached the combined endpoint of HF death or hospitalization. On multivariate analysis, LBBB (HR, 3.50; 95% CI, 1.1-11.1; P = 0.033) and LVEF <50% (HR, 5.1; 95% CI, 1.9-14.2; P = 0.002) were confirmed as independent predictors of HF death or hospitalization. Patients with LVEF <50% and/or LBBB displayed significantly higher rates of HF death or hospitalization (log-rank test, all P<0.001). The majority of patients with a standard indication for permanent pacing and normal LV function remained in a clinically stable condition after pacemaker implantation. However, ∼7% of patients developed new-onset HF over a period of follow-up of 27 months, and the presence of LBBB and LVEF <50% at the baseline predicted HF death or hospitalization.

Impact of electrocardiographic interpretability on outcome in patients referred for stress testing

There is limited insight into the association of electrocardiographic interpretability with outcome in patients referred for stress testing. Exercise echocardiography was performed in 8226 patients with known or suspected coronary artery disease. Electrocardiograms were considered uninterpretable in the presence of left bundle-branch block (LBBB), left ventricular hypertrophy (LVH) with strain, repolarization abnormalities because of digitalis therapy, ventricular paced rhythm, preexcitation or ST depression ≥ 0.1 mV because of other causes. End points were all-cause mortality, cardiac death and hard cardiac events (i.e. cardiac death or nonfatal myocardial infarction). A total of 2450 patients had uninterpretable electrocardiograms. During a follow-up period of 4.1 ± 3.5 years, there were 1011 deaths (of which 478 were cardiac deaths) and 1069 patients experienced a hard cardiac event. The 5-year rates of death, cardiac death and hard cardiac events were, respectively, 18.7%, 10.9% and 18.8% in patients with uninterpretable ECGs, compared with 9.5%, 4.1% and 10.9% in those with interpretable ECGs (P < 0.001). After covariate adjustment, lack of ECG interpretability remained an independent predictor of all-cause mortality (hazard ratio [HR] 1.25, 95% confidence interval [CI] 1.08-1.44, P = 0.002), cardiac death (HR 1.63, 95% CI 1.32-2.01, P < 0.001) and hard cardiac events (HR 1.28, 95% CI 1.11-1.47, P < 0.001). When the specific ECG abnormalities were included as covariates, LBBB, LVH and digitalis therapy remained predictors of cardiac death; LBBB and LVH were predictors of hard cardiac events, and LVH remained predictive of all-cause mortality. Uninterpretable ECGs portend a worse prognosis in patients referred for stress testing.

Abstract P318: Why Do Some Patients Not Receive Reperfusion Therapy for ST-Elevation Myocardial Infarction (STEMI)? A Field Evaluation With Expert Core Laboratory Electrocardiographic Analysis

Many apparently eligible patients with ST-elevation myocardial infarction (STEMI) do not receive reperfusion treatment for reasons that remain poorly understood. We explored predictors for not receiving reperfusion treatment, defined as fibrinolysis or urgent referral (≤ 4 hours after triage) for primary angioplasty, in patients with STEMI. A field evaluation systematically reviewed STEMI care in 80 hospitals in 2006-7. Patients with myocardial infarction, acute presenting symptoms, and medical chart mention of STEMI, had a copy of their first electrocardiogram (ECG) interpreted independently at the field evaluation center by 2 cardiologists as being definite STEMI, not STEMI, or uncertain. Left bundle branch block (LBBB) was classified separately. Patients with at least one definite or uncertain ECG interpretation (including LBBB) were considered to have STEMI (n=2,137); of these, 524 (24.5%) did not receive reperfusion therapy. Their 30-day and 1-year mortality was 17.9% and 29.4% compared to 5.6% and 7.8%, respectively, in patients receiving reperfusion treatment (p &lt;0.001). Independent predictors of not receiving reperfusion treatment included: older age, female gender, heart rate &gt;100 beats/min and longer symptom duration. Among patients without LBBB (n=1930), lack of ECG-based agreement for definite STEMI was strongly and independently associated with no reperfusion [OR=6.1; 95% CI: 4.7-8.0]. For only 20.0% of patients not receiving reperfusion treatment did the 2 cardiologists agree on definite STEMI on ECG. Presence of LBBB was also a strong predictor of no reperfusion [OR=13.1 (95% CI: 8.8-19.6)]; only 17.4% of patients with LBBB received reperfusion treatment. Thus, this study confirms the high-risk clinical features and poor prognosis of STEMI patients who do not receive reperfusion and indicates that lack of expert agreement on definite STEMI and presence of LBBB are important predictors of no reperfusion therapy. Further study is needed to determine whether these high-risk patients may benefit from immediate referral for cardiac catheterization.

Diagnosing Acute Myocardial Infarction in Patients With Left Bundle Branch Block

We compared the clinical features, laboratory and coronary angiographic findings, treatments, and outcomes among patients with ST-segment elevation myocardial infarction (MI) with and without left bundle branch block (LBBB). We examined 5,742 patients with ST-segment elevation MI with and without LBBB treated with primary percutaneous coronary intervention in the Assessment of Pexelizumab in Acute Myocardial Infarction trial. The main outcome measures were obstructive coronary disease, MI, positive cardiac biomarkers, angiographic Thrombolysis In Myocardial Infarction flow, and death, MI, or congestive heart failure at 90 days. LBBB was present in 98 patients (1.7%). According to the protocol, patients with LBBB were eligible only if they had ≥1 mm concordant ST-segment elevation. Obstructive coronary artery disease was present in >87% of the patients with LBBB. Documented MI (elevated biomarkers) with an initially occluded infarct artery was more common in patients with LBBB with concordant ST-segment elevation (71.4%) than in patients without (44.1%; p = 0.027). The use of ST-segment elevation concordance criteria in the presence of LBBB was more often associated with documented MI with an identifiable culprit vessel with an initially occluded infarct-related artery. In conclusion, because a substantial proportion of patients with LBBB have acute MI with a culprit lesion and positive biomarkers, these data support immediate catheterization with the intent for primary percutaneous coronary intervention for all patients presenting with suspected ST-segment elevation myocardial infarction, ischemic symptoms, and presumed new LBBB, particularly if concordant ST-segment elevation is present.

Bundle branch block during primary angioplasty: reperfusion success remains encrypted in the ECG!

It has been known for years that the finding of bundle branch block (BBB) in patients with ST-segment elevation myocardial infarction (STEMI) is associated with a high mortality rate [1]. In the prethrombolytic era, several studies demonstrated that the presence of left BBB (LBBB) and right BBB (RBBB) was associated with large infarct sizes often accompanied by heart failure, ventricular arrhythmias or cardiovascular death [2]. Although thrombolytic reperfusion decreased mortality in STEMI patients, the appearance of BBB was still associated with a poor short- and long-term prognosis [3–6]. Current guidelines recommend primary percutaneous coronary intervention (PCI) as the gold- standard therapy for the management of patients with STEMI [7–9]. There are some reports addressing the incidence and prognosis of BBB in this setting, but hardly anyone addresses the importance of different kinds of BBB; is it the same as a previous (already known) BBB or a de novo (transient vs persistent after reperfusion) BBB? Why are BBBs associated with such a poor prognosis? The mechanisms explaining why BBBs are asso ciated with such a dismal prognosis remain poorly understood. Previous studies have speculated that the high mortality might be related to the bundle branches’ blood supply. Interestingly, both right and left bundle branches are irrigated by branches arising from proximal coronary arteries, and their occlusion induces large infarctions unless reperfusion therapy is carried out promptly [10]. It is worth noting that the right bundle branch often has a dual blood supply and therefore the involvement of the two main coronary arteries is theor etically required for the appearance of RBBB. Therefore, the association between BBB and an acute myocardial infarction reveals a poor prognosis. However, if the patient presents the BBB before the onset of the STEMI, it is possible that this finding is not associated with the same poor prognosis (Figure 1).

Lack of association between left bundle-branch block and acute myocardial infarction in symptomatic ED patients

Objective Guidelines recommend treating patients with a new or presumed new left bundle-branch block (LBBB) similar to those with an acute ST-segment elevation myocardial infarction. It is often unclear which emergency department (ED) patients with potentially ischemic symptoms actually have an acute myocardial infarction (AMI), even in the setting of LBBB. Our null hypothesis was that in ED patients with potential AMI, the presence of a new or presumed new LBBB would not predict an increased likelihood of AMI. Methods This was an observational cohort study. Patients older than 30 years who presented with chest pain or other ischemic equivalent and had an electrocardiogram (ECG) to evaluate potential acute coronary syndrome (ACS) were enrolled. Data collected include demographics, history, ECG, and cardiac markers. Electrocardiograms were classified according to the standardized guidelines, including LBBB not known to be old (new or presumed new LBBB), LBBB known to be old, or no LBBB. The hospital course was followed, and 30-day follow-up was performed on all patients. Our main outcome was AMI. Results There were 7937 visits (mean age, 54.3 ± 15 years, 57% female, 68% black): 55 had new or presumed new LBBB, 136 had old LBBB, and 7746 had no LBBB. The rate of AMI was not significantly different between the 3 groups (7.3% vs 5.2% vs 6.1%; P = .75). Revascularization (7.8% vs old 5.2% vs 4.3%; P = .04) and coronary artery disease were more common in patients with new or presumed new LBBB (19.2% vs 11.9% vs 10.1%; P = .0004). Conclusions Despite guideline recommendations that patients with potential ACS and new or presumed new LBBB should be treated similar to STEMI, ED patients with a new or presumed new LBBB are not at increased risk of AMI. In fact, the presence of LBBB, whether new or old, did not predict AMI. Caution should be used in applying recommendations derived from patients with definite AMI to ED patients with potential ACS that may or may not be sustaining an AMI.

Acute myocardial infarction with left bundle-branch block: disproportional anterior ST elevation due to right ventricular myocardial infarction in the presence of left bundle-branch block

A case of inferior and right ventricular acute myocardial infarction in the presence of left bundle-branch block is presented. The electrocardiogram manifests disproportional, discordant ST elevation in leads II, III, and aVF and in leads V 1 through V 4.

ACC/AHA 2007 Guidelines on Perioperative Cardiovascular Evaluation and Care for Noncardiac Surgery

2007;50;e159-e242; originally published online Sep 27, 2007; J. Am. Coll. Cardiol. Tarkington, and Clyde W. Yancy Lytle, Rick Nishimura, Joseph P. Ornato, Richard L. Page, Barbara Riegel, Lynn G. W. Valentin Fuster, Jonathan L. Halperin, Loren F. Hiratzka, Sharon A. Hunt, Bruce Christopher E. Buller, Mark A. Creager, Steven M. Ettinger, David P. Faxon, Alice K. Jacobs, Cynthia D. Adams, Jeffrey L. Anderson, Elliott M. Antman, K. Kasper, Judy R. Kersten, Barbara Riegel, John F. Robb, Sidney C. Smith, Jr, Chaikof, Kirsten E. Fleischmann, William K. Freeman, James B. Froehlich, Edward Lee A. Fleisher, Joshua A. Beckman, Kenneth A. Brown, Hugh Calkins, Elliott L. Vascular Surgery Interventions, Society for Vascular Medicine and Biology, and Society for and Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography Society of Nuclear Cardiology, Heart Rhythm Society, Society of Collaboration With the American Society of Echocardiography, American Developed in Cardiovascular Evaluation for Noncardiac Surgery) (Writing Committee to Revise the 2002 Guidelines on Perioperative Cardiology/American Heart Association Task Force on Practice Guidelines Care for Noncardiac Surgery: A Report of the American College of ACC/AHA 2007 Guidelines on Perioperative Cardiovascular Evaluation and This information is current as of March 25, 2009 http://content.onlinejacc.org/cgi/content/full/50/17/e159 located on the World Wide Web at: The online version of this article, along with updated information and services, is

Predicting outcome in severe heart failure. Who will benefit from device therapy (CRT)?

Dyssynchronous ventricular contraction in severe heart failure contributes to low cardiac output, worsening symptoms, and poor prognosis. Recognition of the effect of dyssynchrony in heart failure, and the possibility of manipulating the sequence of electrical cardiac activation to improve the efficiency of mechanical events, led Cazeau et al. to attempt four-chamber pacing in 1994.1 This early system could stimulate both atria and both ventricles extrinsically, and could dictate the temporal relationship between atrial systole and ventricular systole, and the ventriculo-ventricular relationship. Modern cardiac resynchronization therapy (CRT), involving pacing of the right and left ventricles, with right atrial pacing to optimize atrio-ventricular delay, has evolved rapidly from this beginning. Left bundle branch block (LBBB) on the surface electrocardiogram (ECG) has been considered a marker of mechanical dyssynchrony as it represents a delay in conduction of depolarization to the left ventricle, with the greatest delay usually being in the lateral free wall. The presence of LBBB, seen in about one-third of patients with heart failure,2 is associated with a poorer outcome than when LBBB is not present.3,4 Furthermore, the wider the QRS complex in LBBB, the worse the prognosis. The presence of a broad QRS complex with LBBB morphology has been an important entry criterion to most of the trials of CRT, which has now been evaluated in randomized clinical trials involving > 4000 patients.5–9 The European Society of Cardiology has now incorporated recommendations for use in clinical practice guidelines.10 The patients for whom CRT is recommended in these guidelines are those who represent a similar group to those involved in the randomized controlled trials, where in most cases the objective evidence of dyssynchrony was a broad QRS complex on the 12-lead ECG. The pharmacological and device-based therapies recommended in … *Corresponding author. Tel: +64 9 373 7599 ext. 89804; fax: +64 9 367 7146. E-mail address: r.doughty{at}auckland.ac.nz