Rosenbaum MB, Elizari MV, Laarri JO. The Hemiblock. Florida : Tampa Tracings, Oldsmar, 1970.
J C Demoulin, H E Kulbertus
Histopathological examination of concept of left hemiblock.
Br Heart J. 1972 Aug;34(8):807-14.
Abstract/Text
Y Nakaya, T Hiraga
Reassessment of the subdivision block of the left bundle branch.
Jpn Circ J. 1981 Apr;45(4):503-16.
Abstract/Text
B E Kreger, K M Anderson, W B Kannel
Prevalence of intraventricular block in the general population: the Framingham Study.
Am Heart J. 1989 Apr;117(4):903-10.
Abstract/Text
QRS intervals in the ECGs of members of the Framingham Heart Study cohort and offspring were measured to provide an estimate of the prevalence of intraventricular block in the general population. Intervals of greater than or equal to 0.09 second appear in men twice as commonly as in women, are rare before age 50 to 60, and shift from a predominance of right bundle branch block in the young to an indeterminate pattern in the elderly. Complete intraventricular block (QRS interval greater than or equal to 0.12 second) is seen in 11% of elderly men and 5% of elderly women. Aside from age and sex, logistic regression indicates strong associations with concurrent manifestations of coronary heart disease, congestive heart failure, and atrioventricular block, as well as hypertension, left ventricular hypertrophy, and ventricular extrasystoles. Among those subjects free of clinical coronary disease and congestive heart failure, associations between QRS interval and age, sex, atrioventricular block, and ECG left ventricular hypertrophy remain significant by multivariate analysis. Whether people with prolonged QRS intervals need special monitoring or attention cannot be told from these data.
E B Sgarbossa, S L Pinski, A Barbagelata, D A Underwood, K B Gates, E J Topol, R M Califf, G S Wagner
Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators.
N Engl J Med. 1996 Feb 22;334(8):481-7. doi: 10.1056/NEJM199602223340801.
Abstract/Text
BACKGROUND: The presence of left bundle-branch block on the electrocardiogram may conceal the changes of acute myocardial infarction, which can delay both its recognition and treatment. We tested electrocardiographic criteria for the diagnosis of acute infarction in the presence of left bundle-branch block.
METHODS: The base-line electrocardiograms of patients enrolled in the GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) trial who had left bundle-branch block and acute myocardial infarction confirmed by enzyme studies were blindly compared with the electrocardiograms of control patients who had chronic coronary artery disease and left bundle-branch block. The electrocardiographic criteria for the diagnosis of infarction were then tested in an independent sample of patients presenting with acute chest pain and left bundle-branch block.
RESULTS: Of 26,003 North American patients, 131 (0.5 percent) with acute myocardial infarction had left bundle-branch block. The three electrocardiographic criteria with independent value in the diagnosis of acute infarction in these patients were an ST-segment elevation of 1 mm or more that was concordant with (in the same direction as) the QRS complex; ST-segment depression of 1 mm or more in lead V1, V2, or V3; and ST-segment elevation of 5 mm or more that was disconcordant with (in the opposite direction from) the QRS complex. We used these three criteria in a multivariate model to develop a scoring system (0 to 10), which allowed a highly specific diagnosis of acute myocardial infarction to be made.
CONCLUSIONS: We developed and validated a clinical prediction rule based on a set of electrocardiographic criteria for the diagnosis of acute myocardial infarction in patients with chest pain and left bundle-branch block. The use of these criteria, which are based on simple ST-segment changes, may help identify patients with acute myocardial infarction, who can then receive appropriate treatment.
J E Madias, A Sinha, H Agarwal, R Ashtiani
ST-segment elevation in leads V1-V3 in patients with LBBB.
J Electrocardiol. 2001 Jan;34(1):87-8.
Abstract/Text
G J Fahy, S L Pinski, D P Miller, N McCabe, C Pye, M J Walsh, K Robinson
Natural history of isolated bundle branch block.
Am J Cardiol. 1996 Jun 1;77(14):1185-90.
Abstract/Text
The purpose of this study was to determine the long-term outcome of patients with bundle branch block (BBB) who have no clinical evidence of cardiovascular disease. Among 110,000 participants in a screening program, 310 subjects with BBB without apparent of suspected heart disease were identified. Their outcome after a mean follow-up of 9.5 years was compared with that of 310 similarly screened age- and sex-matched controls. Among the screened population, isolated right BBB was more prevalent than isolated left BBB (0.18% vs 0.1%, respectively; p<0.001), and the prevalence of each abnormality increased with age (p<0.001). Total actuarial survival was no different for those with left BBB or right BBB and their respective controls. Cardiac mortality, however, was increased in the left BBB group when compared with their controls (p=0.01, log rank test). Left BBB, but not right BBB, was associated with an increased prevalence of cardiovascular disease at the follow-up (21% vs 11%; p=0.04). In the absence of clinically overt cardiac disease, the presence of left BBB or right BB is not associated with increased overall mortality. Isolated left BBB is associated with an increased risk of developing overt cardiovascular disease and increased cardiac mortality.
Inder S Anand, Peter Carson, Elizabeth Galle, Rui Song, John Boehmer, Jalal K Ghali, Brian Jaski, JoAnn Lindenfeld, Christopher O'Connor, Jonathan S Steinberg, Jill Leigh, Patrick Yong, Michael R Kosorok, Arthur M Feldman, David DeMets, Michael R Bristow
Cardiac resynchronization therapy reduces the risk of hospitalizations in patients with advanced heart failure: results from the Comparison of Medical Therapy, Pacing and Defibrillation in Heart Failure (COMPANION) trial.
Circulation. 2009 Feb 24;119(7):969-77. doi: 10.1161/CIRCULATIONAHA.108.793273. Epub 2009 Feb 9.
Abstract/Text
BACKGROUND: In the Comparison of Medical Therapy, Pacing and Defibrillation in Heart Failure (COMPANION) trial, 1520 patients with advanced heart failure were assigned in a 1:2:2 ratio to optimal pharmacological therapy or optimal pharmacological therapy plus cardiac resynchronization therapy (CRT-P) or CRT with defibrillator (CRT-D). Use of CRT-P and CRT-D was associated with a significant reduction in combined risk of death or all-cause hospitalizations. Because mortality also was significantly reduced (optimal pharmacological therapy versus CRT-D only), an assessment of the true reduction in hospitalization rates must consider the competing risk of death and varying follow-up times.
METHODS AND RESULTS: To overcome the challenges of comparing treatment groups, we used a nonparametric test of right-censored recurrent events that accounts for multiple hospital admissions, differential follow-up time between treatment groups, and death as a competing risk. An end-point committee adjudicated and classified all hospitalizations. Compared with optimal pharmacological therapy, CRT-P and CRT-D were associated with a 21% and 25% reduction in all-cause, 34% and 37% reduction in cardiac, and 44% and 41% reduction in heart failure hospital admissions per patient-year of follow-up, respectively. Similar reductions were seen in hospitalization days per patient-year. The reduction in hospitalization rate for heart failure in the CRT groups appeared within days of randomization and remained sustained. Noncardiac hospitalization rates were not different between groups.
CONCLUSIONS: Use of CRT with or without a defibrillator in advanced heart failure patients was associated with marked reductions in all-cause, cardiac, and heart failure hospitalization rates in an analysis that accounted for the competing risk of mortality and unequal follow-up time.
John G F Cleland, Jean-Claude Daubert, Erland Erdmann, Nick Freemantle, Daniel Gras, Lukas Kappenberger, Luigi Tavazzi, Cardiac Resynchronization-Heart Failure (CARE-HF) Study Investigators
The effect of cardiac resynchronization on morbidity and mortality in heart failure.
N Engl J Med. 2005 Apr 14;352(15):1539-49. doi: 10.1056/NEJMoa050496. Epub 2005 Mar 7.
Abstract/Text
BACKGROUND: Cardiac resynchronization reduces symptoms and improves left ventricular function in many patients with heart failure due to left ventricular systolic dysfunction and cardiac dyssynchrony. We evaluated its effects on morbidity and mortality.
METHODS: Patients with New York Heart Association class III or IV heart failure due to left ventricular systolic dysfunction and cardiac dyssynchrony who were receiving standard pharmacologic therapy were randomly assigned to receive medical therapy alone or with cardiac resynchronization. The primary end point was the time to death from any cause or an unplanned hospitalization for a major cardiovascular event. The principal secondary end point was death from any cause.
RESULTS: A total of 813 patients were enrolled and followed for a mean of 29.4 months. The primary end point was reached by 159 patients in the cardiac-resynchronization group, as compared with 224 patients in the medical-therapy group (39 percent vs. 55 percent; hazard ratio, 0.63; 95 percent confidence interval, 0.51 to 0.77; P<0.001). There were 82 deaths in the cardiac-resynchronization group, as compared with 120 in the medical-therapy group (20 percent vs. 30 percent; hazard ratio 0.64; 95 percent confidence interval, 0.48 to 0.85; P<0.002). As compared with medical therapy, cardiac resynchronization reduced the interventricular mechanical delay, the end-systolic volume index, and the area of the mitral regurgitant jet; increased the left ventricular ejection fraction; and improved symptoms and the quality of life (P<0.01 for all comparisons).
CONCLUSIONS: In patients with heart failure and cardiac dyssynchrony, cardiac resynchronization improves symptoms and the quality of life and reduces complications and the risk of death. These benefits are in addition to those afforded by standard pharmacologic therapy. The implantation of a cardiac-resynchronization device should routinely be considered in such patients.
Copyright 2005 Massachusetts Medical Society.
A Auricchio, C Stellbrink, M Block, S Sack, J Vogt, P Bakker, H Klein, A Kramer, J Ding, R Salo, B Tockman, T Pochet, J Spinelli
Effect of pacing chamber and atrioventricular delay on acute systolic function of paced patients with congestive heart failure. The Pacing Therapies for Congestive Heart Failure Study Group. The Guidant Congestive Heart Failure Research Group.
Circulation. 1999 Jun 15;99(23):2993-3001.
Abstract/Text
BACKGROUND: Previous studies of pacing therapy for dilated congestive heart failure (CHF) have not established the relative importance of pacing site, AV delay, and patient heterogeneity on outcome. These variables were compared by a novel technique that evaluated immediate changes in hemodynamic function during brief periods of atrial-synchronous ventricular pacing.
METHODS AND RESULTS: Twenty-seven CHF patients with severe left ventricular (LV) systolic dysfunction and LV conduction disorder were implanted with endocardial pacing leads in the right atrium and right ventricle (RV) and an epicardial lead on the LV and instrumented with micromanometer catheters in the LV, aorta, and RV. Patients in normal sinus rhythm were stimulated in the RV, LV, or both ventricles simultaneously (BV) at preselected AV delays in a repeating 5-paced/15-nonpaced beat sequence. Maximum LV pressure derivative (LV+dP/dt) and aortic pulse pressure (PP) changed immediately at pacing onset, increasing at a patient-specific optimal AV delay in 20 patients with wide surface QRS (180+/-22 ms) and decreasing at short AV delays in 5 patients with narrower QRS (128+/-12 ms) (P<0.0001). Overall, BV and LV pacing increased LV+dP/dt and PP more than RV pacing (P<0.01), whereas LV pacing increased LV+dP/dt more than BV pacing (P<0.01).
CONCLUSIONS: In this population, CHF patients with sufficiently wide surface QRS benefit from atrial-synchronous ventricular pacing, LV stimulation is required for maximum acute benefit, and the maximum benefit at any site occurs with a patient-specific AV delay.
Melissa J Byrne, Robert H Helm, Samantapudi Daya, Nael F Osman, Henry R Halperin, Ronald D Berger, David A Kass, Albert C Lardo
Diminished left ventricular dyssynchrony and impact of resynchronization in failing hearts with right versus left bundle branch block.
J Am Coll Cardiol. 2007 Oct 9;50(15):1484-90. doi: 10.1016/j.jacc.2007.07.011. Epub 2007 Sep 24.
Abstract/Text
OBJECTIVES: We compared mechanical dyssynchrony and the impact of cardiac resynchronization therapy (CRT) in failing hearts with a pure right (RBBB) versus left bundle branch block (LBBB).
BACKGROUND: Cardiac resynchronization therapy is effective for treating failing hearts with conduction delay and discoordinate contraction. Most data pertain to LBBB delays. With RBBB, the lateral wall contracts early so that biventricular (BiV) pre-excitation may not be needed. Furthermore, the magnitude of dyssynchrony and impact of CRT in pure RBBB versus LBBB remains largely unknown.
METHODS: Dogs with tachypacing-induced heart failure combined with right or left bundle branch radiofrequency ablation were studied. Basal dyssynchrony and effects of single and BiV CRT on left ventricular (LV) function were assessed by pressure-volume catheter and tagged magnetic resonance imaging, respectively.
RESULTS: Left bundle branch block and RBBB induced similar QRS widening, and LV function (ejection fraction, maximum time derivative of LV pressure [dP/dt(max)]) was similarly depressed in failing hearts with both conduction delays. Despite this, mechanical dyssynchrony was less in RBBB (circumferential uniformity ratio estimate [CURE] index: 0.80 +/- 0.03 vs. 0.58 +/- 0.09 for LBBB, p < 0.04; CURE 0-->1 is dyssynchronous-->synchronous). Cardiac resynchronization therapy had correspondingly less effect on hearts with RBBB than those with LBBB (i.e., 5.5 +/- 1.1% vs. 29.5 +/- 5.0% increase in dP/dt(max), p < 0.005), despite similar baselines. Furthermore, right ventricular-only pacing enhanced function and synchrony in RBBB as well or better than did BiV, whereas LV-only pacing worsened function.
CONCLUSIONS: Less mechanical dyssynchrony is induced by RBBB than LBBB in failing hearts, and the corresponding impact of CRT on the former is reduced. Right ventricular-only pacing may be equally efficacious as BiV CRT in hearts with pure right bundle branch conduction delay.
Majid Haghjoo, Ataallah Bagherzadeh, Maryam Moshkani Farahani, Zahra Ojaghi Haghighi, Mohammad Ali Sadr-Ameli
Significance of QRS morphology in determining the prevalence of mechanical dyssynchrony in heart failure patients eligible for cardiac resynchronization: particular focus on patients with right bundle branch block with and without coexistent left-sided conduction defects.
Europace. 2008 May;10(5):566-71. doi: 10.1093/europace/eun081. Epub 2008 Apr 3.
Abstract/Text
AIMS: The aim of this study was to assess the significance of QRS morphology in determining the prevalence of mechanical dyssynchrony in heart failure (HF) patients considered eligible for cardiac resynchronization.
METHODS AND RESULTS: A total of 200 consecutive HF patients (158 males, mean age 56 +/- 13.5 years) with standard indications for cardiac resynchronization therapy (CRT) were evaluated prospectively. The prevalence of an interventricular mechanical delay > or = 40 ms was lower in patients with pure right bundle branch block (RBBB) than that in those with RBBB plus left fascicular hemiblock (RBBB-LFH) and those with left bundle branch block (LBBB) (33 vs. 50 vs. 54%, P = 0.05). A maximal difference in peak myocardial systolic velocity among all 12 segments (Ts) > 100 ms was found in 63% of the patients with LBBB, whereas it was present in 31% of the patients with pure RBBB and in 42% of those with RBBB-LFH (P < 0.001). A standard deviation of Ts (Ts-SD) > 34 ms was present in 58% of the LBBB subjects, but in only 29% and 42% of the patients with pure RBBB and RBBB-LFH, respectively (P < 0.001). Intraventricular dyssynchrony, however, was not different in patients with pure RBBB and in those with RBBB-LFH in terms of maximal difference in Ts (P = 0.25) and Ts-SD (P = 0.17).
CONCLUSIONS: Although LBBB was more often associated with intraventricular dyssynchrony, ECG sign of additional left ventricular (LV) conduction delay is not a helpful tool for the identification of intra-LV mechanical dyssynchrony in HF patients with RBBB who would benefit from CRT.
John Rickard, Dharam J Kumbhani, Eiran Z Gorodeski, Bryan Baranowski, Oussama Wazni, David O Martin, Richard Grimm, Bruce L Wilkoff
Cardiac resynchronization therapy in non-left bundle branch block morphologies.
Pacing Clin Electrophysiol. 2010 May;33(5):590-5. doi: 10.1111/j.1540-8159.2009.02649.x. Epub 2009 Dec 16.
Abstract/Text
INTRODUCTION: 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).
METHODS: 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.
RESULTS: 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.
CONCLUSION: 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.
Wojciech Zareba, Helmut Klein, Iwona Cygankiewicz, W Jackson Hall, Scott McNitt, Mary Brown, David Cannom, James P Daubert, Michael Eldar, Michael R Gold, Jeffrey J Goldberger, Ilan Goldenberg, Edgar Lichstein, Heinz Pitschner, Mayer Rashtian, Scott Solomon, Sami Viskin, Paul Wang, Arthur J Moss, MADIT-CRT Investigators
Effectiveness of Cardiac Resynchronization Therapy by QRS Morphology in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT).
Circulation. 2011 Mar 15;123(10):1061-72. doi: 10.1161/CIRCULATIONAHA.110.960898. Epub 2011 Feb 28.
Abstract/Text
BACKGROUND: This study aimed to determine whether QRS morphology identifies patients who benefit from cardiac resynchronization therapy with a defibrillator (CRT-D) and whether it influences the risk of primary and secondary end points in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) trial.
METHODS AND RESULTS: Baseline 12-lead ECGs were evaluated with regard to QRS morphology. Heart failure event or death was the primary end point of the trial. Death, heart failure event, ventricular tachycardia, and ventricular fibrillation were secondary end points. Among 1817 patients with available sinus rhythm ECGs at baseline, there were 1281 (70%) with left bundle-branch block (LBBB), 228 (13%) with right bundle-branch block, and 308 (17%) with nonspecific intraventricular conduction disturbances. The latter 2 groups were defined as non-LBBB groups. Hazard ratios for the primary end point for comparisons of CRT-D patients versus patients who only received an implantable cardioverter defibrillator (ICD) were significantly (P < 0.001) lower in LBBB patients (0.47; P < 0.001) than in non-LBBB patients (1.24; P = 0.257). The risk of ventricular tachycardia, ventricular fibrillation, or death was decreased significantly in CRT-D patients with LBBB but not in non-LBBB patients. Echocardiographic parameters showed significantly (P < 0.001) greater reduction in left ventricular volumes and increase in ejection fraction with CRT-D in LBBB than in non-LBBB patients.
CONCLUSIONS: Heart failure patients with New York Heart Association class I or II and ejection fraction ≤ 30% and LBBB derive substantial clinical benefit from CRT-D: a reduction in heart failure progression and a reduction in the risk of ventricular tachyarrhythmias. No clinical benefit was observed in patients with a non-LBBB QRS pattern (right bundle-branch block or intraventricular conduction disturbances).
CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00180271.
