Left Bundle-Branch Block Induced by Transcatheter Aortic Valve Implantation Increases Risk of Death

Background—

Transcatheter aortic valve implantation (TAVI) is a novel therapy for treatment of severe aortic stenosis. Although 30% to 50% of patients develop new left bundle-branch block (LBBB), its effect on clinical outcome is unclear.

Methods and Results—

Data were collected in a multicenter registry encompassing TAVI patients from 2005 until 2010. The all-cause mortality rate at follow-up was compared between patients who did and did not develop new LBBB. Of 679 patients analyzed, 387 (57.0%) underwent TAVI with the Medtronic CoreValve System and 292 (43.0%) with the Edwards SAPIEN valve. A total of 233 patients (34.3%) developed new LBBB. Median follow-up was 449.5 (interquartile range, 174–834) days in patients with and 450 (interquartile range, 253–725) days in patients without LBBB ( P =0.90). All-cause mortality was 37.8% (n=88) in patients with LBBB and 24.0% (n=107) in patients without LBBB ( P =0.002). By multivariate regression analysis, independent predictors of all-cause mortality were TAVI-induced LBBB (hazard ratio [HR], 1.54; confidence interval [CI], 1.12–2.10), chronic obstructive lung disease (HR, 1.56; CI, 1.15–2.10), female sex (HR, 1.39; CI, 1.04–1.85), left ventricular ejection fraction ≤50% (HR, 1.38; CI, 1.02–1.86), and baseline creatinine (HR, 1.32; CI, 1.19–1.43). LBBB was more frequent after implantation of the Medtronic CoreValve System than after Edwards SAPIEN implantation (51.1% and 12.0%, respectively; P <0.001), but device type did not influence the mortality risk of TAVI-induced LBBB.

Conclusions—

All-cause mortality after TAVI is higher in patients who develop LBBB than in patients who do not. TAVI-induced LBBB is an independent predictor of mortality.

[Prehospital thrombolysis acute coronary syndrome in patients with acute left bundle branch block]

Analyzed 30-days survival in 18 patients after a system of dark prehospital thrombolysis performed for an acute coronary syndrome (ACS) with acute left bundle branch block (LBBB). Survival after thrombolytic therapy (TLT) was 4 times higher than in patients with acute coronary syndrome and acute blockade LBBB without TLT. It is concluded that thrombolytic therapy leads to a reduction of the QRS complex in 66% of patients.

Prognostic impact of electrocardiographic signs in patients with Type 2 diabetes and cardiovascular disease: results from the PROactive study

AIMS

Although a resting electrocardiograph is broadly applied in clinical practice for evaluating patients with Type 2 diabetes and cardiovascular disease, the independent prognostic relevance of electrocardiographic signs has not thoroughly been examined.

METHODS

Baseline 12-lead electrocardiographs available in 5231 of the 5238 participants of the PROactive trial were analysed for heart rate, heart rate corrected QT-interval, presence of atrial fibrillation/flutter, left axis deviation, right and left bundle branch block. The association of electrocardiographic signs with total mortality, the principal secondary composite endpoint (death, myocardial infarction and stroke) and serious adverse heart failure events was examined by Cox-regression analysis.

RESULTS

Two hundred and twenty-three (4.3%) patients showed atrial fibrillation/flutter, 213 (4.1%) patients had right bundle branch block, 111 (2.1%) patients had left bundle branch block and 706 (13.5%) patients had left axis deviation. Mean cQT-interval was 418 ms (± 25 ms) and mean heart rate was 72/min (± 14/min). In multivariate adjusted analyses, heart rate and cQT-interval were significantly associated with mortality, the composite secondary endpoint and heart failure, whereas right and left bundle branch blocks were significantly associated with heart failure only. Left axis deviation was associated with heart failure and atrial fibrillation/flutter was associated with mortality and heart failure in univariate but not multivariate analyses.

CONCLUSION

Easily assessable electrocardiographic signs such as heart rate, cQT-interval and bundle branch blocks were predictive for adverse outcome independently of multiple risk factor adjustment and should be considered in clinical care.

[Cardiac resynchronisation therapy : new data and technical developments]

Cardiac resynchronisation therapy (CRT) has opened up new perspectives over the past 10 years for highly symptomatic patients with severe systolic heart failure. The present article analyses and comments on recent publications which have lead to an expansion of the indication to patients with mild symptoms of heart failure, and which resulted in the modification of current European guidelines in 2010. The data available from narrow QRS complex studies are critically examined. Furthermore, the latest technical innovations in the field of CRT, which have helped to ease the implantation procedure and achieve higher success rates, are presented. Finally, new wireless ultrasound technology to stimulate the left ventricle, currently in an early clinical phase of evaluation, is presented as a potential alternative in the future.

Impact of a well-organized collaborative team approach on mortality in patients with ST-segment elevation myocardial infarction

OBJECTIVE

Fibrinolytic therapy remains a legitimate option for many patients presenting with acute ST-segment elevation myocardial infarction (STEMI). Shorter time- to- treatment for patients with STEMI administered fibrinolytic therapy has repeatedly been shown to reduce mortality. A well-organized collaborative team approach was implemented in April 2007. The purpose of this study was to examine the effect of implementing a well-organized collaborative team approach on the outcome in patients with acute STEMI treated with fibrinolysis.

METHODS

Sociodemographic, clinical, laboratory, and time interval data were prospectively collected on 109 consecutive patients (the study group) and 155 patients from the years 2005-2007 (the control group) retrospectively. A single-phone call was made to discuss case. Emergency department evaluation was bypassed for definitive case. An electrocardiogram was faxed to the on-call cardiologist for suspected case. Door-to-needle times were calculated as medians. Mortality was assessed by reviewing records of all patients visiting outpatient clinic. For the rest, information was obtained over the phone. Median door-to-needle times were compared using Mann-Whitney U test. The Fisher's exact test was used to compare 6-month mortalities.

RESULTS

Improvements were seen in door-to- needle times in the study group regardless of time of presentation (reduced from 59 minutes to 29 minutes during off hours) (reduced from 35 minutes to 18 minutes during regular hours) (p<0.0001). Mortality was significantly reduced in the study group (2 deaths, 1.8%) compared with the control group (12 deaths, 7.7%, p=0.048).

CONCLUSION

The mortality of patients presenting with acute STEMI treated with fibrinolytic therapy was significantly reduced after optimal hospital organization.

Prognostic value of lead V1 ST elevation during acute inferior myocardial infarction

BACKGROUND

Lead V(1) directly faces the right ventricle and may exhibit ST elevation during an acute inferior myocardial infarction when the right ventricle is also involved. Leads V(1) and V(3) indirectly face the posterolateral left ventricle, and ST depression ("mirror-image" ST elevation) in V(1) through V(3) may reflect concomitant posterolateral infarction. The prognostic significance of V(1) ST elevation during an acute inferior myocardial infarction may therefore be dependent on V(3) ST changes.

METHODS AND RESULTS

In 7967 patients with acute inferior myocardial infarction in the Hirulog and Early Reperfusion or Occlusion-2 (HERO-2) trial, V(1) ST levels were analyzed with adjustment for lead V(3) ST level for predicting 30-day mortality. V(1) ST elevation at baseline, analyzed as a continuous variable, was associated with higher mortality. Unadjusted, each 0.5-mm-step increase in ST level above the isoelectric level was associated with approximately 25% increase in 30-day mortality; this was true whether V(3) ST depression was present or not. The odds ratio for mortality was 1.21 (95% confidence interval, 1.07 to 1.37) after adjustment for inferolateral ST elevation and clinical factors and 1.24 (95% confidence interval, 1.09 to 1.40) if also adjusted for V(3) ST level. In contrast, lead V(1) ST depression was not associated with mortality after adjustment for V(3) ST level. V(1) ST elevation >or=1 mm, analyzed dichotomously in all patients, was associated with higher mortality. The odds ratio was 1.28 (95% confidence interval, 1.01 to 1.61) unadjusted, 1.51 (95% confidence interval, 1.19 to 1.92) adjusted for V(3) ST level, and 1.35 (95% confidence interval, 1.04 to 1.76) adjusted for ECG and clinical factors. Persistence of V(1) ST elevation >or=1 mm 60 minutes after fibrinolysis was associated with higher mortality (10.8% versus 5.5%, P=0.001).

CONCLUSIONS

V(1) ST elevation identifies patients with acute inferior myocardial infarction who are at higher risk.

In-hospital outcome in patients with ST elevation myocardial infarction and right bundle branch block. A sub-study from RENASICA II, a national multicenter registry

OBJECTIVE

Compare in-hospital outcome in patients with ST-elevation myocardial infarction with right versus left bundle branch block.

METHODS

RENASICA II, a national Mexican registry enrolled 8098 patients with final diagnosis of acute coronary syndrome secondary to ischemic heart disease. In 4555 STEMI patients, 545 had bundle branch block, 318 (58.3%) with right and 225 patients with left (41.6%). Both groups were compared in terms of in-hospital outcome through major cardiovascular adverse events; (cardiovascular death, recurrent ischemia and reinfarction). Multivariable analysis was performed to identify in-hospital mortality risk among right and left bundle branch block patients.

RESULTS

There were not statistical differences in both groups regarding baseline characteristics, time of ischemia, myocardial infarction location, ventricular dysfunction and reperfusion strategies. In-hospital outcome in bundle branch block group was characterized by a high incidence of major cardiovascular adverse events with a trend to higher mortality in patients with right bundle branch block (OR 1.70, CI 1.19 - 2.42, p < 0.003), compared to left bundle branch block patients.

CONCLUSION

In this sub-study right bundle branch block accompanying ST-elevation myocardial infarction of any location at emergency room presentation was an independent predictor of high in-hospital mortality.

Complete right bundle branch block predicts mortality in Thai patients with chronic heart failure with reduced ejection fraction

BACKGROUND

Previous studies have shown that intraventricular conduction defect is associated with increased mortality in heart failure (HF) population. However, it is conflicting whether left bundle branch block (LBBB) or right bundle branch block (RBBB) is a better predictor for mortality.

OBJECTIVE

To evaluate the relationship between patterns of bundle branch block (BBB) and all-cause mortality in Thai patients with chronic heart failure with reduced ejection fraction (HFrEF) and to compare the prognostic values of RBBB and LBBB in this population.

MATERIAL AND METHOD

The authors retrospectively studied a cohort of 170 patients (age 58 +/- 14 years, male=117) with HFrEF requiring hospitalization and were followed-up in a heart failure clinic. Predictors of mortality were evaluated by Cox proportional hazard analysis.

RESULTS

Wide QRS complex (duration >120 ms) was present in 26% of patients, 15% with LBBB, 11% with RBBB. During an average follow-up of 1.8 +/-1.6 years, 22 patients (13%) died. By univariate analysis, presence of chronic renal insufficiency, chronic obstructive pulmonary disease, severe left ventricular systolic dysfunction and RBBB, but not LBBB were associated with increased mortality. After multivariate adjustment, the presence of RBBB was the only strong predictor of mortality in HF patients (OR 3.9, 95% CI 1.3-11.7, p < 0.05).

CONCLUSION

The presence of RBBB was the only independent predictor of mortality in Thai patients with HFrEE

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.

Prognostic significance of bundle-branch block in acute myocardial infarction: the importance of location and time of appearance

BACKGROUND

The presence of bundle-branch block (BBB) is associated with high mortality rates and is considered an important predictor of poor outcome in patients with acute myocardial infarction (AMI).

HYPOTHESIS

The objective of this study was to assess the prognostic significance of BBB in patients with AMI depending on its form of presentation.

METHODS

A multicenter prospective 1-year follow-up study involving 1,239 consecutive patients diagnosed with AMI was performed.

RESULTS

Bundle-branch block was present in 177 cases (14.2%), associated with worse clinical characteristics, lower rate of thrombolytic therapy, and higher mortality: in-hospital (23.8 vs. 9.7%, p < .01) and 1-year (40.9 vs. 16.9%, p < 0.01). Compared with right BBB (n = 135), left BBB (n = 42) was more often associated with female gender and higher prevalence of cardiovascular diseases, but had a similar 1-year mortality. In the absence of heart failure or complete atrioventricular (AV) block, there was no difference in in-hospital mortality of patients with BBB (n = 76) and without BBB (n = 786) (2.6 vs. 3.9%). Compared with existing BBB (n = 113), BBB of new appearance (n = 64) was more often accompanied by complete AV block and heart failure and higher in-hospital and 1-year mortality rates. Only BBB of new appearance was an independent predictor of mortality: in-hospital (odds ratio [OR] 2.3, 95% confidence interval [CI] 1.1-4.7) and 1-year mortality (OR 3.2, 95% CI, 1.7-9.1).

CONCLUSIONS

In patients with AMI, the classification of BBB according not only to location but also to time of appearance is of practical interest. New BBB is an independent predictor of short- and long-term mortality.

[Structural-functional peculiarities of the heart and survival of elderly patients with chronic heart failure and left bundle branch block]

AIM

To study structural-functional characteristics of the heart and survival of elderly patients with chronic heart failure (CHF) and left bundle branch block (LBBB).

MATERIAL AND METHODS

We examined and followed-up 108 patients aged 60-85 years with NYHA class II-IV CHF with and without LBBB.

RESULTS

Patients of both groups were comparable according to sex, age, CHF duration and severity, hemodynamic parameters, clinical condition, quality of life, and spectrum of taken drugs. Patients with LBBB had statistically significant increases of end diastolic (p<0.001) and systolic (p<0.001) dimensions, end diastolic (p<0.001) and systolic (p<0.001) volumes, sphericity index (p<0.001), long axis (p<0.05), decreases of relative thickness of the left ventricle (p<0.05), interventricular septum (p<0.001), and left ventricular ejection fraction (p<0.001). Pronounced mitral regurgitation also was more frequent in patients with LBBB (p<0.01). During follow up 14/34 patients (41.2%) with LBBB and 19/74 patients (25.7%) without LBBB died. There were 10 and 9 sudden deaths among patients with and without LBBB, respectively.

CONCLUSION

In patients with LBBB development of CHF is associated with changes of left ventricular geometry. Sudden death is the most frequent cause of death of these patients.

Prognostic impact of left bundle-branch block in the early stable phase after acute myocardial infarction

BACKGROUND

Diagnostic marker parameters are needed to enable timely identification of high risk patients after acute myocardial infarction (MI). We assessed risk factors for death and sudden death in stable revascularized patients undergoing guideline-based therapy during an in-patient rehabilitation program more than 3 weeks after acute myocardial infarction.

METHODS

During an in-patient rehabilitation program, 939 patients with a recent myocardial infarction were prospectively included. Besides demographic and clinical data, ejection fraction (EF), Holter ECG, standard 12-lead electrocardiogram (ECG) and baseline laboratory values were determined. Patients were followed up for 18 months.

RESULTS

Among multiple variables, left bundle-branch block (LBBB) was the most significant parameter affecting the outcome (combination endpoint of death, resuscitation or ventricular tachycardia (VT)), hazard ratio 7.74 (3.2-18.7, P<0.0001). 42% of the 24 patients with LBBB but only 11.5% of the 62 patients with a left ventricular EF </=30% died during follow-up (P<0.001).

CONCLUSION

LBBB observed during a rehabilitation program following an acute MI indicates a grave prognosis with a high mortality rate (mainly caused by sudden death). Future studies are required to establish whether this simple marker characterizes a group of patients that will profit from preventive defibrillator implantation and/or biventricular pacing.

Influence of left bundle branch block on long-term mortality in a population with heart failure

BACKGROUND

The purpose of this study was to assess the independent contribution of left bundle branch block (LBBB) on long-term mortality in a large cohort with symptomatic heart failure (HF) requiring hospitalization.

METHODS AND RESULTS

We studied a prospective cohort of 21 685 cases of symptomatic HF requiring hospitalization in the Register of Information and Knowledge about Swedish Heart Intensive care Admissions in 1995-2003. Long-term mortality was evaluated by Logistic regression analysis, adjusted for multiple covariates that could influence long-term prognosis. LBBB was present in 20% (4395 of 21 685) of HF admissions. Patients with LBBB had a higher prevalence of cardiac comorbid conditions than patients with no LBBB. 1-, 5-, and 10-year mortality was 31.5 vs. 28.4%, 69.3 vs. 61.3%, and 90.1 vs. 84.7% for HF patients with and without respectively LBBB. When adjusting for comorbidity, LBBB was associated with increased 5-year mortality (OR, 1.21; 95% CI, 1.10-1.35; P < 0.001). When left ventricular ejection fraction was included in the analysis LBBB had no longer any independent influence on 5-mortality (OR, 0.99; 95% CI, 0.62-1.56; P = 0.953).

CONCLUSION

LBBB occurs in 1/5 in HF patients requiring hospitalization and is associated with a very high mortality. However, the high long-term mortality appears to be caused by cardiac comorbidities and myocardial dysfunction rather than the LBBB per se.

Prognostic value of tissue Doppler-derived ventricular asynchrony in patients with left bundle branch block but not advanced heart failure

OBJECTIVES

The aim of the present study was to evaluate the prognostic significance of tissue Doppler echocardiography (TDE)-derived ventricular asynchrony in patients with left bundle branch block (LBBB) but not advanced heart failure.

METHODS

Fifty-five patients (mean age 66 +/- 13 years; 33 male) with complete LBBB (QRS > 120 ms) hospitalized for an acute episode of decompensated heart failure and in New York Heart Association class II for at least 6 months before the study admission underwent standard Doppler echo and pulsed-wave TDE. Precontraction time (PCTm) from the beginning of Q wave of electrocardiogram to the onset of systolic myocardial velocity wave was evaluated in four different left ventricular (LV) basal myocardial segments (LV anterior, inferior, septal and lateral walls) and in one right ventricular (RV) lateral wall. Intraventricular activation delay (IntraV-del) was calculated by the difference of PCTm of each LV myocardial segment. Interventricular activation delay (InterV-del) was calculated by the difference of PCTm between the most delayed LV segment and RV lateral wall.

RESULTS

The mean value of EF was 40 +/- 9% and of InterV-del, IntraV-del was, respectively (97.4 +/- 46.7 and 57.9 +/- 35.5 ms). InterV-del was inversely related to EF (r = -0.68; P < 0001). During the follow-up (26 months, range 11-37 months) cardiac events were recorded in 23 (41%) patients: a worsening of heart failure (WHF) in 23 patients and cardiac death in ten patients. Cox proportional hazard multivariate analysis showed that age, and InterV-del [HR = 1.02 (P < 0.05) and 1.03 (P < 0005)] predicted mortality. A Receiver operating characteristic analysis showed that a cut-off value of InterV-del 100 ms (AUC = 0.86; P < 0001) predicted WHF and mortality with sensitivity and specificity of 75% and 90%; 81% and 84%, respectively.

CONCLUSIONS

TDE-derived interventricular asynchrony represents a prognostic indicator of major cardiac events at 2 years of follow-up in patients with LBBB but not advanced heart failure.

Effect of bundle branch block on microvolt T-wave alternans and electrophysiologic testing in patients with ischemic cardiomyopathy

BACKGROUND

T-wave alternans (TWA) and electrophysiology study (EPS) are used for risk stratification for sudden death.

OBJECTIVE

The purpose of the study was to determine the effect of bundle branch block or intraventricular conduction delay on TWA and EPS.

METHODS

386 patients with coronary artery disease, nonsustained ventricular tachycardia, and left ventricular ejection fraction < or =40% underwent TWA and EPS, and were followed for 40 +/- 19 months.

RESULTS

Patients with wide QRS were more likely than narrow QRS patients to have nonnegative TWA (77% vs 63%, P <.01) or positive EPS (60% vs 48%, P = .03). Nonnegative TWA predicted the combined endpoint of ventricular tachyarrhythmia or death in narrow QRS (HR = 1.64, P = .04) but not wide QRS patients (HR = 1.04, P = .91). Similarly, positive EPS predicted the combined endpoint in narrow QRS (HR = 2.28, P <.001) but not wide QRS patients (HR = 0.94, P = .84). In multivariate analysis, QRS width and TWA, as well as QRS width and EPS, were independent predictors of events. There was no TWA- or EPS-based difference in arrhythmia-free survival within any specific wide QRS morphology.

CONCLUSION

TWA and EPS are more often abnormal in patients with a wide QRS than in those with a narrow QRS. In patients with narrow QRS, both TWA and EPS stratify patients according to their risk of ventricular tachyarrhythmia or death. However, among patients with a wide QRS, regardless of specific QRS morphology, the risk is high and comparable regardless of TWA or EPS results. Therefore, the only truly low-risk group consists of those patients with negative test results and a narrow QRS.

Mortality in insureds with complete right or left bundle branch block

BACKGROUND

On May 1, 1954, a prospective mortality study was instituted in the Medical Department of the New England Mutual Life Insurance Company for all persons on whom an electrocardiogram (ECG) was made. Details were coded on an 80-column, mark-sense punched card for the ECG interpretation, for clinical findings, and for demographic/insurance data.

RESULTS

Mortality is based on the experience of 231 policy-holders with complete right bundle branch block (RBBB) and 45 policyholders with complete left bundle branch block (LBBB). These were drawn from 28,687 interpretation records 1954-1966, if there was some follow-up (FU) exposure between 1954 and 1975. Mortality data are for all ages and all durations combined. In cases with associated rated cardiovascular (CV) impairment, there were 22 observed vs 7.72 expected deaths in RBBB, and 6 observed vs 2.72 expected deaths in LBBB. Exposures and deaths were smaller when there was no rated CV impairment associated with the ECG abnormality: 11 observed vs 8.11 expected deaths in RBBB, and 3 observed vs 1.78 expected deaths in LBBB.

CONCLUSIONS

In complete RBBB, excess mortality was significant at the Poisson 95% confidence level when a rated CV impairment was associated with the RBBB, but the excess was minimal and not significant when the RBBB was essentially an isolated finding with no associated CV impairment. In LBBB the numbers of deaths were too few to permit even a 90% confidence level of significance when there was an associated CV impairment (the 2.72 expected deaths were just above the lower limit of 2.6 deaths at the 90% level).

Fascicular Conduction Disturbances After Coronary Artery Bypass Surgery: A Review With a Meta-Analysis of Their Long-term Significance

Fascicular conduction abnormalities are frequently reported following adult cardiac surgery, but their pathogenesis and long-term outcomes remain unclear. In this article, we review the epidemiological features, pathogenesis, diagnosis, and management, and the short-term and long-term significance of fascicular conduction abnormalities following coronary artery bypass graft (CABG) surgery, based on data from 30 studies. Conduction disturbances have an incidence of 3.4% to 55.8% after CABG surgery, the most common being right bundle branch block (RBBB). RBBB is usually transient and benign. Although a slew of factors have been implicated in the pathogenesis of fascicular conduction disturbances, the two most important factors are myocardial ischemia and type of cardioplegia. While a 12-lead electrocardiogram is the gold standard for diagnosis, additional tests such as myocardial enzymes or echocardiography may have additional diagnostic and prognostic value. Short-term prognosis after RBBB is good, but its impact on long-term survival is unclear. We conducted a meta-analysis, the first of its kind in this area, using long-term survival data from five studies. There was no difference in long-term survival between patients who developed conduction disturbances after CABG surgery, and those who did not, indicating a benign influence of conduction disturbances on long-term survival, and the lack of the necessity for monitoring or pacing. While the older literature reported an adverse impact of fascicular conduction disturbances on long-term survival, the more recent studies report a substantially reduced mortality after CABG surgery, despite a higher incidence of conduction disturbances, pointing to the effect of improved surgical techniques.

Noninvasive risk stratification of subjects with a Brugada-type electrocardiogram and no history of cardiac arrest

BACKGROUND

Recent studies suggest that the Brugada-type electrocardiogram (ECG) is much more prevalent than the manifest Brugada syndrome. Although invasive electrophysiologic investigations have been proposed as a risk stratifier, their value is controversial, and alternative noninvasive techniques may be preferred. We sought a noninvasive strategy to detect a high-risk group in a long-term follow-up study of subjects with a Brugada-type ECG, and no history of cardiac arrest.

METHODS

This study enrolled 124 consecutive subjects with a Brugada-type ECG. Prognostic indices included: age, sex, a family history of sudden death, syncopal episodes, a spontaneous coved-type ST-segment elevation, maximal magnitude of ST-segment elevation, a spontaneous change in ST segment, a mean QRS duration, maximal QT interval, QT dispersion, late potentials (LP) by signal-averaged ECG, and microvolt T-wave alternans.

RESULTS

Of the 124 subjects, 20 consenting subjects had an implantable defibrillator before follow-up. During a 40 +/- 19-month follow-up, 12 subjects (9.7%) reached one of the endpoints (sudden death or ventricular tachyarrhythmia). Of the 12 risk indices, a family history of sudden death, syncopal episodes, a spontaneous coved-type ST-segment elevation, a spontaneous change in ST segment, and LP had significant values. In multivariate analysis, a spontaneous change in ST segment had the most significance (a relative hazard, 9.2; P = 0.036). Combined assessment of this index and other significant indices obtained higher positive predictive values (43-71%).

CONCLUSIONS

A spontaneous change in ST segment is associated with the highest risk for subsequent events in subjects with a Brugada-type ECG. The presence of syncopal episodes, a history of familial sudden death, and/or LP may increase its value.

Risk factor implications of incidentally discovered uncomplicated bundle branch block

OBJECTIVE

To evaluate the long-term outcome of a community-based patient population with incidentally discovered asymptomatic and uncomplicated bundle branch block (BBB).

PATIENTS AND METHODS

A retrospective observational cohort study was undertaken of patients in Olmsted County, Minnesota, who were evaluated between 1975 and 1999 and were incidentally diagnosed as having BBB. We performed Kaplan-Meier analyses of all-cause mortality and development of first cardiac morbidity after the diagnosis of BBB, along with matched control group comparisons.

RESULTS

A total of 723 patients with left BBB (LBBB) (58.1%) and right BBB (41.9%) met criteria. Mortality was higher in patients with BBB compared with controls (absolute difference of approximately 10% over 20 years; hazard ratio = 1.27; confidence interval, 1.02-1.58; P=.03) as was the development of first cardiac-related morbidity (hazard ratio = 1.32; confidence interval, 1.14-1.54; P<.001). Patients with BBB and without the risk factors of diabetes, hypertension, and/or hypercholesterolemia showed increased long-term mortality compared with matched controls (no BBB) also without risk factors (P=.02). However, comparable mortality was shown between patients with BBB who did not have these risk factors and matched control patients who had these risk factors. The risk of developing cardiac-related morbidity also was increased in the presence of BBB, particularly LBBB.

CONCLUSIONS

Uncomplicated asymptomatic BBB (notably LBBB) with normal left ventricular ejection fraction is not benign. Our findings indicate that the presence of isolated BBB denotes a high-risk patient subgroup that has a compromised long-term outcome comparable to patients with conventional cardiovascular risk factors.

[Right bundle branch block: electrocardiographic and prognostic features]

The electrocardiographic appearances and the significance of right bundle branch block were described at the beginning of the 20th century. Typical appearances include prolongation > 0.12 s of the QRS complex, RR' or rR' or Rr' appearances in V1 and widened S waves in the leads exploring the left ventricle (SI, aVL, V5 and V6). A delay in the appearance of the intrinsic deflection > 0.08 s may also be observed in the right precordial leads and negative T waves with ST depression may be seen in V1 and sometimes in V2. Left axis deviation of the QRS complex greater than - 45 degrees suggests associated left anterior hemiblock. Right axis deviation beyond + 120 degrees is equivocal. The principal differential ECG diagnosis is the Brugada syndrome, a familial arrhythmogenic autosomal dominant cardiomyopathy of variable penetration. This diagnosis is suggested when ECG abnormalities are observed in patients with a personal or family history of sudden death. Right bundle branch block only seems to have haemodynamic consequences in cardiac failure with associated asynchrony of the left ventricle or in certain cases of right ventricular dilatation encountered in congenital heart disease. The prognosis of right bundle branch block in the absence of underlying cardiac disease is good but it may be poor in other cases, particularly coronary artery disease. Moreover, the prognosis of right bundle branch block to complete atrioventricular block is rare in the absence of associated cardiac disease.