Bundle branch block and sudden death

The Aging Heart: A Molecular and Clinical Challenge

Aging is associated with an increasing burden of morbidity, especially for cardiovascular diseases (CVDs). General cardiovascular risk factors, ischemic heart diseases, heart failure, arrhythmias, and cardiomyopathies present a significant prevalence in older people, and are characterized by peculiar clinical manifestations that have distinct features compared with the same conditions in a younger population. Remarkably, the aging heart phenotype in both healthy individuals and patients with CVD reflects modifications at the cellular level. An improvement in the knowledge of the physiological and pathological molecular mechanisms underlying cardiac aging could improve clinical management of older patients and offer new therapeutic targets.

Trends, Prevalence, and Outcomes of Sudden Cardiac Arrest Post Cardiac Transplant: A Nationwide 16-Year Study

Heart transplantation is the most effective long-term therapy for end-stage heart disease. There is limited data related to sudden cardiac arrest (SCA) in postheart transplant recipients. We aimed to describe the trends, and rate of SCA following heart transplantation and thereby identify clinical predictors as well as outcomes of SCA in patients post-transplant. We queried the National Inpatient Sample (NIS) with administrative codes for SCA and heart transplant. We assessed baseline differences between SCA and non-SCA admissions, with hazard ratios adjusted for age, gender, CCI, and race. Multivariable logistic regression models were generated to identify the independent predictors for SCA. There was a total of 30,020 hospitalizations of heart transplant recipients between 1999 and 2014 in the United States and among these 1,953 patients (6.5%) suffered SCA with an increasing trend of admissions for SCA. Among the patients who suffered from SCA, 18.83% died during the same hospitalization, 19.29% were discharged to a long-term facility, and 61.38% were discharged home. Multivariate analysis demonstrated that conduction system disorders (Hazard ratio [95% confidence interval]; 7.1 [4.5-11.1]), female gender (HR:1.2 [1.1-1.3]), diabetes (HR:1.4 [1.2-1.6]), and hypertension (HR:1.2 [1.1-1.4]) were the strongest predictors for SCA. SCA hospitalizations occur in 6.5% of patients post cardiac transplant and have been increasing from 1999 to 2014. Conduction block, graft rejection, female gender, hypertension, diabetes are independent predictors for SCA in heart transplant recipients.

Basic Principles of Cardiac Electrophysiology

This article represents an overview of the basic concepts of cardiac electrophysiology. This relatively new field became a subspecialty of cardiology in the mid-1990s due to the rapid development of equipment that allowed the study and cure of cardiac arrhythmias percutaneously. Simultaneously, technology provided the field with percutaneous cardiac implantable electronic devices designed to protect patients from life-threatening bradyarrhythmias and tachyarrhythmias. Recently, the field has focused on the ablative treatment of atrial fibrillation, the most common arrhythmia facing an aging population, and the diagnosis and management of many inherited arrhythmias through advances in understanding of their genetic cause.

Arrhythmias in Patients ≥80 Years of Age: Pathophysiology, Management, and Outcomes

Advances in medical care have led to an increase in the number of octogenarians and even older patients, forming an important and unique patient subgroup. It is clear that advancing age is an independent risk factor for the development of most arrhythmias, causing substantial morbidity and mortality. Patients ≥80 years of age have significant structural and electrical remodeling of cardiac tissue; accrue competing comorbidities; react differently to drug therapy; and may experience falls, frailty, and cognitive impairment, presenting significant therapeutic challenges. Unfortunately, very old patients are under-represented in clinical trials, leading to critical gaps in evidence to guide effective and safe treatment of arrhythmias. In this state-of-the-art review, we examine the pathophysiology of aging and arrhythmias and then present the available evidence on age-specific management of the most common arrhythmias, including drugs, catheter ablation, and cardiac implantable electronic devices.

QT prolongation and ventricular fibrillation in acute myocardial infarction

Fourteen acute myocardial infarction (AMI) patients with early ventricular fibrillation (VF) were compared to 27 control patients without VF with regard to the corrected QT interval (QTc) and the QRS duration. Patients with complete bundle branch block (BBB) had been excluded. The QTc tended to be longer in the VF group than in the controls, but the difference, 13 msec, disappeared after exclusion of a further 5 VF patients and one control with QRS duration greater than 0.10 sec of other configurations than complete BBB. In the long QT syndrome of various types, VF is characteristically preceded by diastolic waves (DW) with larger amplitudes than the preceding T waves. None of the 5 AMI patients with an evaluable recording of the onset of VF, showed DWs preceding the arrhythmia. The results of this study do not support the opinion that VG is associated with a prolonged QT interval in AMI in the same way as in the long QT syndrome. The longer QT interval in patients with VF seems to be mainly secondary to the longer QRS duration.

Arrhythmic complications of acute coronary syndromes

Cardiac arrhythmias routinely manifest during or following an acute coronary syndrome (ACS). Although the incidence of arrhythmia is directly related to the type of ACS the patient is experiencing, the clinician needs to be cautious with all patients in these categories. As an example, nearly 90% of patients who experience acute myocardial infarction (AMI) develop some cardiac rhythm abnormality and 25% have a cardiac conduction disturbance within 24 hours of infarct onset. In this patient population, the incidence of serious arrhythmias, such as ventricular fibrillation (4.5%) ,is greatest in the first hour of an AMI and declines rapidly thereafter. This article addresses the identification and treatment of arrhythmias and conduction disturbances that complicate the course of patients who have ACS, particularly AMI and thrombolysis. Emphasis is placed on mechanisms and therapeutic strategies.

Arrhythmias associated with acute myocardial infarction and thrombolysis

Ninety percent of patients with acute myocardial infarction have some cardiac rhythm abnormality, and approximately twenty-five percent have cardiac conduction disturbance within 24 hours following infarct onset. Almost any rhythm disturbance can be associated with acute myocardial infarction, including bradyarrhythmias, supraventricular tachyarrhythmias, ventricular arrhythmias, and atrioventricular block. With the advent of thrombolytic therapy, it was found that some rhythm disturbances in patients with acute myocardial infarction may be related to successful coronary artery reperfusion. This article addresses the role and treatment of arrhythmias and conduction disturbances that complicate the course of patients with acute infarction and thrombolysis.

Acute myocardial infarction and complete bundle branch block at hospital admission: clinical characteristics and outcome in the thrombolytic era. GUSTO-I Investigators. Global Utilization of Streptokinase and t-PA [tissue-type plasminogen activator] for Occluded Coronary Arteries

OBJECTIVES

We sought to assess the outcome of patients with acute myocardial infarction (MI) and bundle branch block in the thrombolytic era.

BACKGROUND

Studies of patients with acute MI and bundle branch block have reported high mortality rates and poor overall prognosis.

METHODS

The North American population with acute MI and bundle branch block enrolled in the Global Utilization of Streptokinase and t-PA [tissue-type plasminogen activator] for Occluded Coronary Arteries (GUSTO-I) trial was matched by age and Killip class with an equal number of GUSTO-I patients without conduction defects.

RESULTS

Of all 26,003 North American patients in GUSTO-I, 420 (1.6%) had left (n = 131) or right (n = 289) bundle branch block. These patients had higher 30-day mortality rates than matched control subjects (18% vs. 11%, p = 0.003, odds ratio [OR] 1.8) and were more likely to experience cardiogenic shock (19% vs. 11%, p = 0.008, OR 1.78) or atrioventricular block/asystole (30% vs. 19%, p < 0.012, OR 1.57) and to require ventricular pacing (18% vs. 11%, p = 0.006, OR 1.73). Bundle branch block also carried an independent 53% higher risk for 30-day mortality. Thirty-day mortality rates for patients with complete, partial and no reversion of the bundle branch block were 8%, 12% and 20%, respectively (two-tailed chi-square test for trend 5.61, p = 0.02, OR 0.34 for complete reversion, OR 0.55 for partial reversion).

CONCLUSIONS

Bundle branch block at hospital admission in patients with acute MI predicts in-hospital complications and poor short-term survival.

Admission clinical and electrocardiographic characteristics predicting in-hospital development of high-degree atrioventricular block in inferior wall acute myocardial infarction

This study assessed the ability of simple clinical and electrocardiographic variables routinely obtained on admission to identify patients who are at high risk of developing high-degree atrioventricular (AV) block during hospitalization in 1,336 patients with inferior wall acute myocardial infarction (AMI). Patients were classified into 2 initial electrocardiographic patterns based on the J-point to R-wave amplitude ratio: pattern 1: those with J point/R wave <0.5 and pattern 2: patients with J point/R wave > or =0.5 in > or =2 leads of the inferior leads II, III, and aVF. High-degree AV block was found in 6.7% of patients (41 of 615) with pattern 1 versus 11.8% of the patients (85 of 721) with pattern 2 on admission electrocardiogram (p = 0.0008). Multivariate logistic regression analysis revealed that the only variables found to be independently associated with high-degree AV block were female gender (odds ratio [OR] 1.48; 95% confidence interval [CI] 0.98 to 2.23; p = 0.06); Killip class on admission > or =2 (OR 2.24; CI 1.43 to 3.51; p = 0.0004); initial electrocardiographic pattern 2 versus pattern 1 (OR 1.82; CI 1.22 to 2.21; p = 0.003); and absence of abnormal Q waves on admission (OR yes vs no 0.68; CI 0.44 to 1.05; p = 0.08). A simple electrocardiographic sign (J point/R wave > or =0.5 in > or =2 leads) is a reliable predictor of the development of advanced AV block among patients receiving thrombolytic therapy for inferior wall AMI.

Prognostic value of an abnormal signal-averaged electrocardiogram in patients with nonischemic congestive cardiomyopathy

BACKGROUND

An abnormal signal-averaged ECG (SAECG) has predictive value for arrhythmic events in patients with coronary artery disease. The purpose of this study was to investigate whether an abnormal SAECG could provide prognostic information in patients with nonischemic dilated cardiomyopathy.

METHODS AND RESULTS

We prospectively obtained SAECGs in 114 patients with dilated nonischemic cardiomyopathy. Twelve-lead ECGs, left ventricular ejection fractions, hemodynamic measurements, and peak exercise oxygen consumption (VO2) also were measured. An SAECG was defined as abnormal by any one of the three following criteria: filtered QRS duration > 120 msec, root-mean-square voltage in the last 40 msec < 20 microV, or duration < 40 microV > 38 msec at 40 Hz. Sixty-six patients had a normal SAECG, 20 patients had an abnormal SAECG, and 28 patients had bundle branch block (BBB). Mean follow-up was 10 +/- 5 months. Age, ejection fraction, peak VO2, pulmonary capillary wedge pressure, and cardiac index were not statistically different among the three groups. Use of antiarrhythmic drugs was similar among the three groups, although patients with BBB had more implantable defibrillators (p < 0.05). The incidence of previous atrial arrhythmias was similar for the three groups. Patients with abnormal SAECG or BBB had more past episodes of sustained ventricular tachycardia and/or sudden death episodes (n = 9) than patients with normal SAECG (n = 1) (p < 0.01). Prospectively, none of the 66 patients with normal SAECG died suddenly or had sustained ventricular arrhythmias. Two deaths occurred from progressive heart failure, and three patients required urgent transplant. In the 20 patients with an abnormal SAECG, four patients had sustained ventricular tachycardia, five patients died suddenly, two patients died from progressive heart failure, and one patient required urgent transplant. In the patients with BBB, four patients had sustained ventricular tachycardia, and four patients required urgent transplant. One-year event-free survival, i.e., absence of ventricular tachycardia and/or death, was 95% in patients with normal SAECG, 88% in patients with BBB, and only 39% in patients with an abnormal SAECG (p < 0.001). Multivariate analysis demonstrated that SAECG and New York Heart Association classification were independent predictors of survival.

CONCLUSIONS

Patients with an abnormal SAECG had a statistically significant increase in sustained ventricular arrhythmias and/or death than did patients with a normal SAECG or BBB. This study demonstrates that an abnormal SAECG is a marker of past and future arrhythmic events in patients with nonischemic dilated cardiomyopathy. In contrast, patients with a dilated cardiomyopathy with a normal SAECG have an excellent prognosis with adverse outcome only from progressive heart failure.

Rapid resolution of new right bundle branch block in acute anterior myocardial infarction patients after thrombolytic therapy

The objectives of this retrospective study are to describe the effect of thrombolytic treatment on the clinical course of patients with acute anterior myocardial infarction complicated by acute right bundle branch block. Patients admitted to the intensive cardiac care unit within < 4 hours from onset of symptoms, and demonstrating an acute right bundle branch block with, or without left axis deviation, on the qualifying ECG were included. All were given intravenous thrombolytic treatment consisting of: streptokinase (1,500,000 IU/40 min) or recombinant tissue type plasminogen activator (120 mg/6 hours). Following admission, patients were continuously monitored and a 12-lead ECG was recorded during each of the first 3 hours and then every 3 hours over the next 21 hours. Eight patients were included (8/211 = 3.8%). Their mean age was 62 +/- 7 years and time elapse from onset to treatment was 122 +/- 26 minutes. Complete resolution of the right bundle branch block occurred within < 3 hours in all and left axis deviation normalized in two patients. Mean peak creatine kinase was 1214 +/- 604 IU and global left ventricular ejection fraction, measured by isotope ventriculography within 24 hours from admission, was 39% +/- 15%. Only one patient was prophylactically paced. In the others, rapid normalization of the conduction block with reperfusion exceeded the logistics required for the transvenous pacemaker implantation procedure. Coronary angiography performed in six patients during 72 hours from admission revealed high grade stenoses in the proximal portion of the left anterior descending coronary artery in five patients and complete occlusion in one.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiography of myocarditis revisited: clinical and prognostic significance of electrocardiographic changes

To clarify the clinical and prognostic value of the ECG, an ECG review was undertaken in 45 consecutive patients with a histologic diagnosis of active myocarditis (29 men and boys and 16 women and girls; age, 36.8 +/- 15 years; idiopathic myocarditis, 39 cases). In patients (21) with symptoms of recent onset (less than or equal to 1 month) AV block and repolarization abnormalities were the prevailing ECG features at the time of admission, and a pseudoinfarction pattern (Q waves plus ST-segment elevation) frequently heralded a rapidly fatal course ("fulminant myocarditis"). Left atrial enlargement and atrial fibrillation, left ventricular hypertrophy and LBBB, which prevailed in patients who had symptoms for longer periods, corresponded to the most severe degree of left ventricular dysfunction during the initial hemodynamic and echocardiographic evaluation. The overall mortality rate after 58 +/- 24 months from the time of diagnosis was 29%. Abnormal QRS complexes and LBBB were markers of poor survival, independently of initial indexes of left and right ventricular function, both of which indicate an increased propensity for sudden cardiac death.

Pacemaker therapy

This article reviews the indications for pacemaker implantation and the techniques and devices currently in use. The management of patients who require permanent pacemakers and the potential complications involved are discussed. The article concludes with a brief synopsis of temporary pacing.

Role of the electrocardiogram in identifying the patient at increased risk for sudden death

Published data dealing with the electrocardiogram as a means of identifying individuals at increased risk for sudden death are meager. The available information suggests that the sensitivity of the electrocardiogram in association with other signs of heart disease is relatively good and that this may vary with the severity of the underlying disease. In contrast, its specificity for sudden death is poor; many patients with abnormal electrocardiograms do not die suddenly or of cardiac causes. The prognosis of any electrocardiographic abnormality is that of the underlying disease.

Indications for and management of cardiac pacemakers

Cardiac pacemakers are now at the forefront of medical technology. The ability to provide pacing therapy adapted to the individual patient has resulted in significant patient benefit. Although the indications for cardiac pacing have changed little over the past decade, the types of pacemakers available for specific bradyarrhythmias have proliferated in leaps and bounds. This technology is complex and sophisticated and requires in-depth knowledge for appropriate utilization. Artificial replacement of the human conduction system is now a reality. Still other advances remain to be achieved in this area, mainly in sensor technology and pacing therapy for tachyarrhythmias. At the current rate of development, the outlook is indeed promising.

Pacemaker dependence in patients with bifascicular block during acute anterior myocardial infarction

Eleven patients with bifascicular block complicating anteroseptal acute myocardial infarction were studied to determine the effect of prophylactic permanent pacing; eight of them also had transient high grade atrioventricular block during the acute phase of the infarction. One month after the infarction an electrophysiological study was performed and a bradycardia indicating pacemaker implanted. All the patients were followed for two years. Six had bradycardia detected, two of whom did not have high grade atrioventricular block during the index infarction. Seven patients died, four of them suddenly. There was no correlation between the electrophysiological findings and subsequent development of bradycardia. Thus pacemaker dependence seems to be common in patients with bifascicular block complicating acute myocardial infarction. Mortality is, however, also high in patients treated with pacemakers. Prospective studies to determine the predictive factors in those patients with an anterior acute myocardial infarction and who benefit from a combination of permanent pacemaker treatment and antiarrhythmic treatment are needed.

Transient asystole associated with amphotericin B infusion

Amphotericin B, a systemic antifungal agent, has not been associated with clinical evidence of cardiac toxicity. We report the case of a 76-year-old patient who developed transient asystole with cardiovascular collapse on two occasions, which coincided with infusion of amphotericin B. The patient was semicomatose and had candida septicemia and renal failure. Serum potassium and digoxin levels were elevated, and serum calcium was low when these episodes occurred. Subsequent postmortem examination revealed no gross evidence of cardiac disease apart from fungal vegetations on the aortic valve. A clear causal relationship between amphotericin B and transient asystole is not demonstrated, but a temporal association, confirmed with rechallenge, is documented in this patient. No similar cases were found in a review of the literature.

Bundle branch block in acute myocardial infarction

The management of patients with acute myocardial infarction complicated by bundle branch block is a significant clinical problem and represents 8% to 13% of patients with acute infarction. This study reviews the records of 606 patients with myocardial infarction admitted to our coronary care unit. Forty-seven (8%) had complete bundle branch block. The risk of developing high-degree AV block in these 47 patients was reviewed. There are no established therapeutic guidelines for patients with pre-existing bundle branch block and left bundle branch block in acute myocardial infarction. We found a high risk of progression in patients with pre-existing bifascicular block in the presence of anterior wall infarction (25%) as well as in patients with left bundle branch block with acute anterior wall infarction (100%). On the basis of our data and careful review of the literature, we recommend prophylactic pacemaker insertion in these high-risk groups.