Incidence and prognostic significance of right bundle branch block in patients with acute myocardial infarction receiving thrombolytic therapy

In Hospital Outcomes of Patients With Right Bundle Branch Block and Anterior Wall ST-Segment Elevation Myocardial Infarction (From a Nationwide Study Using the National Inpatient Sample)

Previous studies have reported worse outcomes for patients with right bundle branch block (RBBB) complicating acute ST-segment elevation myocardial infarction (STEMI). There is a paucity of data examining outcomes with RBBB and STEMI in contemporary large-scale studies. This study aims to explore the outcomes of patients with anterior wall STEMI (AW-STEMI) and RBBB. Using ICD-9 codes, we queried the National Inpatient Sample of 1999 to 2014 to identify AW-STEMI admissions and stratified them for the presence of RBBB. Primary outcome was in-hospital mortality within 30 days. Secondary outcomes included acute heart failure, complete heart block, and permanent pacemaker implantation. Cox-proportional logistic regression models were used to determine the hazard ratios of the primary outcome and secondary outcomes and interventions. Among 1,075,875 weighted anterior wall STEMI (AW-STEMI) admissions, 19,153 (1.8%) had RBBB. Compared with patients without RBBB, mortality was significantly higher for patients with RBBB (9.2% vs 15.3%; p <0.0001). RBBB in the setting of AW-STEMI was associated with a 66% increased risk of 30-day in-hospital mortality (hazard ratios [HR], 1.66; 95% confidence interval [CI], 1.52 to1.81; p <0.0001) and a higher likelihood of acute heart failure (HR, 1.37; 95% CI, 1.29 to 1.45; p <0.0001), complete heart block (HR, 2.90; 95% CI, 2.64 to 3.18; p <0.0001) and utilization of a permanent pacemaker (HR, 2.51; 95% CI, 1.89 to 3.35; p <0.0001). In conclusion, the presence of RBBB in the setting of an AW-STEMI is a significant independent predictor of a poor prognosis, including a higher rate of acute heart failure, complete heart block, need for a permanent pacemaker, and a higher 30-day in-hospital mortality.

Right Bundle Branch Block in Acute Myocardial Infarction Treated by Primary Coronary Angioplasty and Stenting

Patients with right bundle branch block (RBBB) in acute myocardial infarction (AMI) have a significantly higher mortality rate even with the advent of thrombolytic therapy. This study was undertaken to assess the impact of primary percutaneous transluminal coronary angioplasty (PTCA) and stenting on the outcome of patients with RBBB in AMI. A total of 600 patients with AMI who underwent primary PTCA and stenting (rate: 61%) <12 hours of onset were studied. A 12-lead ECG was obtained at least every 6 hours. Serial creatine kinase was measured, and left ventricular ejection fraction was obtained during the hospital stay. Among 600 patients with AMI, 94 patients (15.7%) had RBBB; it was persistent in 31 (33%) and transient in 63 (67%). In-hospital mortality rate was 7.3% in patients without RBBB, 7.9% in transient RBBB, and 25.8% in persistent RBBB (p<0.02). The incidence of heart failure was 26.5% in those without RBBB, 34.9% in transient RBBB, and 58.1% in persistent RBBB (p<0.001). There was no significant difference among these 3 groups in ventricular arrhythmias and complete atrioventricular block. Peak creatine kinase was 3,214 ±2,293 U/L in those without RBBB, 4,558 ±3,316 U/L in transient RBBB (p<0.001), and 5,635 ±3,920 U/L in persistent RBBB (p<0.001). Left ventricular ejection fraction was 50 ±11% in those without RBBB, 47 ±11% in transient RBBB (p<0.05), and 42 ±13% in persistent RBBB (p<0.001). Patients with AMI treated by primary PTCA and stenting had an increased incidence of transient RBBB, especially following reperfusion therapy, although the clinical outcome was similar to that of those without RBBB. In contrast, there was no satisfactory improvement in clinical outcomes in those with persistent RBBB.

Clinical Characteristics, Management, and Outcomes of Acute Coronary Syndrome in Patients With Right Bundle Branch Block on Presentation

We examined the relations between right bundle branch block (RBBB) and clinical characteristics, management, and outcomes among a broad spectrum of patients with acute coronary syndrome (ACS). Admission electrocardiograms of patients enrolled in the Global Registry of Acute Coronary Events (GRACE) electrocardiogram substudy and the Canadian ACS Registry I were analyzed independently at a blinded core laboratory. We performed multivariable logistic regression analysis to assess the independent prognostic significance of admission RBBB on in-hospital and 6-month mortality. Of 11,830 eligible patients with ACS (mean age 65; 66% non-ST-elevation ACS), 5% had RBBB. RBBB on admission was associated with older age, male sex, more cardiovascular risk factors, worse Killip class, and higher GRACE risk score (all p <0.01). Patients with RBBB less frequently received in-hospital cardiac catheterization, coronary revascularization, or reperfusion therapy (all p <0.05). The RBBB group had higher unadjusted in-hospital (8.8% vs 3.8%, p <0.001) and 6-month mortality rates (15.1% vs 7.6%, p <0.001). After adjusting for established prognostic factors in the GRACE risk score, RBBB was a significant independent predictor of in-hospital death (odds ratio 1.45, 95% CI 1.02 to 2.07, p = 0.039), but not cumulative 6-month mortality (odds ratio 1.29, 95% CI 0.95 to 1.74, p = 0.098). There was no significant interaction between RBBB and the type of ACS for either in-hospital or 6-month mortality (both p >0.50). In conclusion, across a spectrum of ACS, RBBB was associated with preexisting cardiovascular disease, high-risk clinical features, fewer cardiac interventions, and worse unadjusted outcomes. After adjusting for components of the GRACE risk score, RBBB was a significant independent predictor of early mortality.

Right bundle-branch block in acute coronary syndrome: diagnostic and therapeutic implications for the emergency physician

Right bundle-branch block (RBBB) in the patient with acute coronary syndrome is a marker of significant potential cardiovascular risk; the RBBB pattern in the patient with acute coronary syndrome identifies a subgroup of patients with quite high short- and long-term morbidity and mortality. Right bundle-branch block is not an uncommon finding on an electrocardiogram in the emergency department patient, noted incidentally and thus without clinical import or, conversely, encountered in the early phase of significant cardiovascular dysfunction. This review will address RBBB in the acute coronary syndrome setting.

The 12-lead electrocardiogram as a predictive tool of mortality after acute myocardial infarction: current status in an era of revascularization and reperfusion

Many recently published studies established the admission electrocardiogram as an excellent source of prognostic information in patients presenting with acute myocardial infarction. Using our search criteria, we identified a large number of articles but selected only the most relevant in each category. The best predictors of increased short-term mortality are ventricular tachycardia (odds ratio [OR] 6.1, 95% CI 4.6-8.3), ST-segment deviations (OR 5.1, 95% CI 4.6-8.3), high-degree atrioventricular block (OR 5.1, 95% CI 2.1-11.9), and long QRS duration (OR 4.2, 95% CI 1.8-10.4). For increased long-term mortality, the best predictors were ST-segment depression (OR 5.7, 95% CI 2.8-11.6), ST-segment elevation (OR 3.3, 95% CI 2.1-5.1), and left bundle-branch block (OR 2.8, 95% CI 1.8-4.3). In addition, our review discusses electrocardiographic markers of poor outcome that were not independent risk factors on multivariate analysis, conflicting findings, and knowledge gaps that can help plan future research efforts.

Posterior myocardial infarction and complete right bundle- branch block

We describe two patients with posterior myocardial infarction (PMI) with unusually atypical clinical presentations and cardiac enzymatic profiles, but with the abrupt development of complete AV block in patient 1, and Mobitz II second-degree AV block with paroxysmal phases of higher degrees of AV block in patient 2, and mitral regurgitation leading to symptomatic pulmonary congestion. Also, both patients had complete right bundle-branch block (RBBB) [old in patient 1, new in patient 2], the pattern of which was altered due to the associated PMI. The alteration included tall R waves involving the early part of the QRS complex, and tall T waves, both noted in the right precordial leads. The mechanism of these ECG modulations of the RBBB pattern was believed to be a superimposition of the early depolarization and repolarization consequences of the PMI. The significance of this observation lies in the ECG detection of PMI, frequently underdiagnosed particularly in patients with an atypical presentation, and with the RBBB adding further to the complexity. Thus, it is gratifying to note the contribution of the ECG to diagnostics, the only modality that provided a pathophysiologic insight in these two patients who appeared to be abruptly deteriorating clinically without an apparent reason.

Bundle branch block as a predictor of long-term survival after acute myocardial infarction

Using a community-based population of patients with acute myocardial infarction (AMI), we sought to: (1) determine the prevalence of bundle branch block (BBB) on the presenting electrocardiogram (ECG), (2) compare the clinical characteristics and the treatment administered to patients with and without BBB, and (3) determine the association of BBB with mortality. We analyzed the admission ECGs of 894 consecutive patients with AMI from Olmsted County, Minnesota, seen at our institution from January 1988 to March 1998. Of these, 53 had left BBB (LBBB) (5.9%) and 60 had right BBB (RBBB) (6.7%). Patients with BBB were more likely to be older, have a history of AMI or hypertension, and to be in Killip class >I at presentation. They were less likely to receive primary reperfusion therapy, beta blockers, or heparin, but more likely to receive angiotensin-converting enzyme inhibitors. They had lower mean predischarge ejection fractions (38 +/- 16% vs 50 +/- 15%, p <0.0001). In-hospital mortality was 13.3%, 17.0%, and 9.1% for patients with RBBB, LBBB, and no BBB, respectively (p = 0.11). Respective postdischarge survival at 1, 3, and 5 years was 80%, 60%, and 50% in the RBBB group, 78%, 56%, and 51% in the LBBB group, and 92%, 85%, and 76% in the group without BBB (p <0.0001). Although BBB was not an independent predictor of mortality on multivariate analysis, the presence of transient or persistent BBB with AMI is an easily recognized clinical marker of increased mortality. Our conclusion from this study is that in a community-based population, patients who had LBBB or RBBB at the time of AMI had lower predischarge ejection fractions and higher in-hospital and long-term unadjusted mortality.

Partial characterization of a basic protein from Crotalus molossus molossus (northern blacktail rattlesnake) venom and production of a monoclonal antibody

The venom of Crotalus molossus molossus (blacktailed rattlesnake) is very basic compared to that of other Crotalinae venoms. Unlike other Crotalinae venoms that are separated by anion exchange chromatography, C. m. molossus venom must be fractionated by cation exchange chromatography. Electrophoretic titration (ET) was used to predict the isoelectric point (pI) and optimal conditions for isolation. The specific hemorrhagic activity for C. m. molossus venom was 7.5 mm/microg, making it one of the most hemorrhagic of Crotalinae venoms. Basic hemorrhagic and fibrinolytic proteins from the venom of C. m. molossus venom were further fractionated by cation exchange chromatography. A basic fibrinolytic/hemorrhagic protein (CMM4) was isolated. CMM4 has a molecular weight between 23 and 26 kDa and a pI of approximately 11.3. SDS electrophoresis revealed one band and ET curve revealed 3 bands with very similar surface charges at all pH. CMM4 did not activate plasminogen when tested with a Chrom Z-PLG assay. The proteins in CMM4 had similar N-terminal amino acid sequences to each other (D-Q-Q-N-L-P-Q-(S/A/R)-Y-(V/R/I)-E-L-V-V-V-A-D-H-R-L-F-M-K-Y-K-S-D-L- N-T). The differences in these proteins are in positions 8 and 10. CMM4 may contain isoforms that differ by minor sequence variations at their amino-termini. The amino acid sequences of CMM4 were very similar to other fibrinolytic and hemorrhagic metalloproteinases isolated from venoms of the genera Crotalus. The specific hemorrhagic activity of CMM4 decreased as the specific fibrinolytic activity increased. A monoclonal antibody (CMM1b) was produced against C. m. molossus venom that neutralized the hemorrhagic activity of some of its fractions. CMM1b also reacted with 11 of 29 venom samples tested via ELISA.

Significance of right bundle branch block in the diagnosis of myocardial ischemia in patients undergoing coronary artery bypass grafting

BACKGROUND

Perioperative diagnosis of myocardial ischemia following cardiac surgical procedures remains a challenging problem. Particularly, the role of new conduction disturbances as markers of postoperative ischemia is still questionable. The goal of this study was to elucidate the diagnostic significance of new postoperative right bundle branch block (RBBB) for the detection of perioperative myocardial ischemia in patients undergoing elective coronary artery bypass grafting (CABG).

METHODS

In 169 consecutive patients, three-channel Holter monitoring and serial assessment of serum enzymes were performed for 48 h, and 12-lead ECG repeated for up to 5 days postoperatively. Postoperative events were classified as either myocardial infarction (MI), transient ischemic events (TIE) or various conduction disturbances.

RESULTS

Transient (n=9) or permanent (n=4) RBBB occurred in 13 patients (8%); 14 patients (8%) showed signs of perioperative MI and 18 patients (11%) evidence of TIE. Peak activity of creatine-kinase (CK, 561+/-135 vs. 316+/-19, P<0.05) and CK-MB (22.7+/-3.2 vs. 13.4+/-0.8, P<0.01) were higher in patients with RBBB than in patients without perioperative ischemic events. Peak CK-MB levels were significantly higher in patients with MI as compared to those with RBBB (33.4+/-7.6 vs. 22.7+/-3.2, P<0. 05). Patients with TIE had similar perioperative enzyme levels as patients with no events.

CONCLUSION

It is concluded that the combined assessment of repeated 12-lead ECG, continuous Holter monitoring and enzyme analysis allows a reliable diagnosis of perioperative myocardial ischemia and conduction disturbances. The occurrence of new RBBB following elective CABG is indicative of perioperative myocardial necrosis and thus serves as a valuable tool for the diagnosis of new, perioperative ischemic events.

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

Screening for fibrinolytic activity in eight Viperid venoms

Snake venoms contain direct-acting fibrinolytic metalloproteinases (MMP) that could have important applications in medicine. Fibrinolytic enzymes isolated from venom can induce in vitro clot lysis by directly acting on a fibrin clot. The most ideal fibrinolytic enzyme would have high affinity for clots, dissolve clots directly without causing hemorrhage, and would not be neutralized in vivo by endogenous metalloproteinase inhibitors. The purpose of this study was to compare DEAE/HPLC venom profiles from Viperid snakes and identify fractions that contain fibrinolytic activity with no hemorrhagic activity and are not neutralized by animal sera. The sera selected were from four (Virginia opossum, Gray woodrat, Mexican ground squirrel, and Hispid cottonrat) animals known to neutralize hemorrhagic activity in snake venoms. Nineteen fractions from the Viperid venoms had fibrinolytic activity. Agkistrodon venom fractions contained the highest specific fibrinolytic activities. A. piscivorus leucostoma fraction 4 contained a high specific fibrinolytic activity, no hemorrhagic activity, and the fibrinolytic activity was not neutralized by the proteinase inhibitors of the four animal sera. A. contortrix laticinctus fraction 1 also had a high specific fibrinolytic activity and no hemorrhagic activity. However, the fibrinolytic activity was neutralized by Didelphis virginiana (Virginia opossum) serum.

Natural protease inhibitors to hemorrhagins in snake venoms and their potential use in medicine

Snake venoms are complex mixtures of many toxins and enzymes which effectively immobilize prey without a struggle and assist in digestion. Certain animals have a remarkable resistance to envenomation of snakes. Naturally occurring factors that neutralize snake venoms have been found in the sera of most snakes and a few warm-blooded animals. These antihemorrhagic and antineurotoxic factors have been purified from snake and mammalian sera. The antihemorrhagins are not immunoglobulins since they have different physical and chemical characteristics. The natural immunity to hemorrhagins is the result of tissue inhibitors of metalloproteinases (TIMP) found in animal sera of resistant animals. Most animals have matrix metalloproteinases (MMP) and TIMP that are implicated in a wide variety of normal physiological processes and pathological conditions. MMP in animals have many biological functions in embryogenesis, morphogenesis and tissue remodeling. MMP activities are precisely regulated by endogenous TIMP. Disruption of the balance between MMP and TIMP causes various diseases such as arthritis, periodontal diseases, diabetes, ophthalmologic conditions, neoplasia, metabolic bone disease, atherosclerosis and orthopedic conditions. Resistant animals that have a high titer of TIMP would have a survival advantage when bitten by poisonous snakes. Snake venoms are abundant and stable sources of MMP which are medically important. The venom MMP which cause unregulated destruction of tissue have sequences which have some degree of homology with mammalian MMP which control normal biological processes. Resistant animals are important sources of TIMP which can be used to study metalloproteinase related diseases. For these reasons the MMP in snakes and TIMP in resistant animal are excellent candidates for developing new drug therapies.