NONSURGICAL ACQUIRED HEART BLOCK*

Takotsubo cardiomyopathy in the setting of complete heart block

Few cases of coincident takotsubo cardiomyopathy and complete heart block (CHB) have been reported. A 62-year-old woman presented with typical chest pain and was found to have CHB with a left ventricular ejection fraction of 35% and apical ballooning on ventriculogram. The patient was transvenously paced and a permanent biventricular pacemaker was placed when the CHB did not resolve. Repeat echocardiography 15 days after the event showed the ejection fraction to be 50%. This case highlights management strategies in this unique situation.

Recommendations for the use of electrophysiological study: Update 2018

The field of cardiac electrophysiology has greatly developed during the past decades. Consequently, the use of electrophysiological studies (EPSs) in clinical practice has also significantly augmented, with a progressively increasing number of certified electrophysiology centers and specialists. Since Zipes et al published the Guidelines for Clinical Intracardiac Electrophysiology and Catheter Ablation Procedures in 1995, no official document summarizing current EPS indications has been published. The current paper focuses on summarizing all relevant data of the role of EPS in patients with different types of cardiac pathologies and provides up-to-date recommendations on this topic. For this purpose, the PubMed database was screened for relevant articles in English up to December 2018 and ESC and ACC/AHA Clinical Practice Guidelines, and EHRA/HRS/APHRS position statements related to the current topic were analyzed. Current recommendations for the use of EPS in clinical practice are discussed and presented in 17 distinct cardiac pathologies. A short rationale, evidence, and indications are provided for each cardiac disease/group of diseases. In conclusion, because of its capability to establish a diagnosis in patients with a variety of cardiac pathologies, the EPS remains a useful tool in the evaluation of patients with cardiac arrhythmias and conduction disorders and is capable of establishing indications for cardiac device implantation and guide catheter ablation procedures.

[Treatment of syncope]

The therapy of patients with syncope is oriented to the underlying pathophysiological mechanisms. Patients with reflex syncope require careful education regarding recognition of warning signs and the avoidance of trigger factors. Treatment with beta blockers is nowadays obsolete. Even other drugs have failed to show any benefit. Pacemaker therapy should only be considered if syncope attacks are frequent and if there is a correlation between symptoms and the electrocardiogram (ECG). Because autonomic failure in patients with orthostatic hypotension is often drug-induced, reduction of the dosage or the complete elimination is the treatment of choice in these patients. A higher than normal salt and fluid intake as well as general measures to avoid delayed venous backflow, e.g. elastic stockings, may also be helpful. A change in blood pressure medication can be decisive for therapy success, especially in elderly patients with arterial hypertension. Pacemaker and defibrillator therapy is the treatment of choice in patients with bradycardia and tachycardia arrhythmias, respectively. Although these measures are simple but effective, in individual cases it is still difficult to find clinical proof that arrhythmic disorders are the causal factors for the syncope. However, also in these patients cardiac pacing should be based on a symptom ECG correlation. The recently conducted market release of the injectable miniaturized ECG recorder will alleviate the diagnostic process. The limits of this approach, however, become obvious when there is the suspicion of a life-threatening rhythm disorder, because the only difference between syncope and sudden cardiac death is that in one case the patient wakes up again.

Pacemaker reuse for patients in resource poor countries: is something always better than nothing?

Cardiovascular disease is the most common cause of death across the globe. Large disparities in access to cardiovascular care exist in the world. An estimated one million people die each year due to lack of access to life saving pacemaker therapy. We discuss the concept of justice in health and health care as it relates to the use of refurbished pacemakers in patients in low- and middle- income countries, where financial circumstances severely limit access to brand new devices. Egalitarianism, utilitarianism, and justice as fairness are examined, as they relate to provision of re-processed pacemakers. This practice, since it holds promise to improve human functioning and capabilities, can be morally justified with some conditions: transparency, further research in is its safety and efficacy, and its impact on other needs and priorities in those countries.

Total beta-adrenoceptor knockout slows conduction and reduces inducible arrhythmias in the mouse heart

INTRODUCTION

Beta-adrenoceptors (β-AR) play an important role in the neurohumoral regulation of cardiac function. Three β-AR subtypes (β(1), β(2), β(3)) have been described so far. Total deficiency of these adrenoceptors (TKO) results in cardiac hypotrophy and negative inotropy. TKO represents a unique mouse model mimicking total unselective medical β-blocker therapy in men. Electrophysiological characteristics of TKO have not yet been investigated in an animal model.

METHODS

In vivo electrophysiological studies using right heart catheterisation were performed in 10 TKO mice and 10 129SV wild type control mice (WT) at the age of 15 weeks. Standard surface ECG, intracardiac and electrophysiological parameters, and arrhythmia inducibility were analyzed.

RESULTS

The surface ECG of TKO mice revealed a reduced heart rate (359.2±20.9 bpm vs. 461.1±33.3 bpm; p<0.001), prolonged P wave (17.5±3.0 ms vs. 15.1±1.2 ms; p = 0.019) and PQ time (40.8±2.4 ms vs. 37.3±3.0 ms; p = 0.013) compared to WT. Intracardiac ECG showed a significantly prolonged infra-Hisian conductance (HV-interval: 12.9±1.4 ms vs. 6.8±1.0 ms; p<0.001). Functional testing showed prolonged atrial and ventricular refractory periods in TKO (40.5±15.5 ms vs. 21.3±5.8 ms; p = 0.004; and 41.0±9.7 ms vs. 28.3±6.6 ms; p = 0.004, respectively). In TKO both the probability of induction of atrial fibrillation (12% vs. 24%; p<0.001) and of ventricular tachycardias (0% vs. 26%; p<0.001) were significantly reduced.

CONCLUSION

TKO results in significant prolongations of cardiac conduction times and refractory periods. This was accompanied by a highly significant reduction of atrial and ventricular arrhythmias. Our finding confirms the importance of β-AR in arrhythmogenesis and the potential role of unspecific beta-receptor-blockade as therapeutic target.

First-degree atrioventricular block is associated with heart failure and death in persons with stable coronary artery disease: data from the Heart and Soul Study

AIMS

First-degree atrioventricular block (AVB) has traditionally been considered a benign electrocardiographic finding in healthy individuals. However, the clinical significance of first-degree AVB has not been evaluated in patients with stable coronary heart disease. We investigated whether first-degree AVB is associated with heart failure (HF) and mortality in a prospective cohort study of outpatients with stable coronary artery disease (CAD).

METHODS AND RESULTS

We measured the P-R interval in 938 patients with stable CAD and classified them into those with (P-R interval ≥ 220 ms) and without (P-R interval <220 ms) first-degree AVB. Hazard ratios (HRs) and 95% confidence intervals were calculated for HF hospitalization and all-cause mortality. During 5 years of follow-up, there were 123 hospitalizations for HF and 285 deaths. Compared with patients who had normal atrioventricular conduction, those with first-degree AVB were at increased risk for HF hospitalization (age-adjusted HR 2.33: 95% CI 1.49-3.65; P= 0.0002), mortality [age-adjusted HR 1.58; 95% CI (1.13-2.20); P = 0.008], cardiovascular (CV) mortality [age-adjusted HR 2.33; 95% CI (1.28-4.22); P= 0.005], and the combined endpoint of HF hospitalization or CV mortality (age-adjusted HR 2.43: 95% CI 1.64-3.61; P ≤ 0.0001). These associations persisted after multivariable adjustment for heart rate, medication use, ischaemic burden, and QRS duration. Adjustment for left ventricular systolic and diastolic function partially attenuated the effect, but first-degree AVB remained associated with the combined endpoint of HF or CV death (HR 1.61, CI 1.02-2.54; P= 0.04).

CONCLUSION

In a large cohort of patients with stable coronary artery disease, first-degree AVB is associated with HF and death.

Correlates of prolonged HV conduction in aortic stenosis

Forty-eight patients with predominant aortic stenosis underwent His bundle electrography (HBE) at the time of diagnostic catheterization. Patients were divided into four groups based upon severity of calcification of the aortic valve fluoroscopically as judged independently by three angiographers. Of 48 patients, three had no calcification, 11 had mild, 18 had moderate, and 16 had severe aortic valve calcification. No correlation was found between HV interval and severity of aortic valve calcification. Significant correlation was found between HV interval prolongation and aortic valve area (p less than 0.02), history of congestive heart failure (p less than 0.02), and increasing left ventricular end-diastolic pressure (p less than 0.05). Left ventricular ejection fraction less than 45% had greater likelihood of HV interval prolongation (p less than 0.01). No correlation was established between HV interval and age, aortic valve gradient, left ventricular peak systolic pressure, syncope, and coronary artery disease. Aortic valve area was the most significant independent predictor of HV prolongation, with history of congestive heart failure second. We conclude that HV interval prolongation in aortic stenosis with calcified valves is best predicted by evidence of declining left ventricular function rather than severity of aortic valve calcification.

Natural course of a prolonged PR interval and the relation between PR and incidence of coronary heart disease. A 7-year follow-up study of 1832 apparently healthy men aged 40-59 years

During a baseline cardiovascular survey PR was measured in a strictly standardized way in 1832 men aged 40-59 years, free from coronary heart disease (CHD). Of 1758 men still alive, 1585 underwent an identical follow-up study 7 years later. A total of 1570 were in sinus rhythm. The following findings were made: (1) Baseline and follow-up prevalence of a prolonged PR (greater than or equal to 0.22 s) was identical (5.3 vs. 5.4%). (2) Only 60% of restudied men with a prolonged PR also had prolonged PR at follow-up. (3) Only 1 of 98 with a prolonged baseline PR had a more advanced AV block at follow-up, whereas an additional 4 had conditions which might influence the AV node (1 Bechterew's disease and 3 mild aortic valve stenosis). (4) The incidence of all CHD events found during the follow-up study (CHD deaths, myocardial infarction, angina pectoris, and pathologic exercise ECGs) was moderately but significantly lower in men with a prolonged PR than among men with a PR less than or equal to 0.21 s. Thus a prolonged PR is rarely an indicator of impending, more severe conduction disturbances; it is mostly a benign, functional finding in middle-aged men free from overt heart disease and is not positively associated with CHD. Rather PR may be moderately and inversely associated with latent CHD.

Unsuspected coronary artery disease as cause of chronic atrioventricular block in middle age

Attention has recently been drawn to the relatively poor prognosis of middle aged patients paced for chronic atrioventricular block when age-linked expectation of life is taken into account, and it has been suggested that this may be the result of underlying coronary artery disease, despite the absence of symptoms to suggest this. It was the purpose of this study to determine the incidence of unsuspected coronary artery disease in middle aged patients presenting with chronic atrioventricular block. Studies were made on a consecutive series of 30 patients aged 45 to 65 (mean age 56 years) with chronic atrioventricular disease who had been referred for pacing. Patients presenting with acute myocardial infarction or angina or with sinuatrial disease without atrioventricular disease were excluded. Coronary arteriography disclosed the presence of severe coronary artery disease in 13 patients. Of the remaining 17 patients, four had congestive cardiomyopathy, two had hypertrophic cardiomyopathy, one had aortic stenosis, and in 10 patients the aetiology of the heart block was unknown. Myocardial revascularisation was undertaken in six patients with paroxysmal atrioventricular block caused by coronary artery disease. Operation did not result in any sustained improvement in atrioventricular conduction.

Atrioventricular conduction in patients with clinical indications for transvenous cardiac pacing

Eighty patients with clinical indications for cardiac pacing had atrioventricular conduction analysed by His bundle study. The indications for cardiac pacing included high grade atrioventricular block, sick sinus node syndrome without tachycardia, bradycardia-tachycardia syndrome, unstable bilateral bundle-branch block, and uncontrolled ventricular irritability. Complete heart block, Wenckeback block (Mobitz I), and 2:1 block were noted proximal and distal to the His bundle. Mobitz II block only occurred distal to the His bundle. Of special interest were the high incidence of distal conduction abnormalities by His bundle analysis (40/80, 50%), the re-establishment of normal atrioventricular conduction in acutely ill patients with recent evidence of heart block, and the high incidence of intraventricular conduction disturbances on standard electrocardiogram (48/80, 60%).

Cardiac arrhythmias. 5. Disturbances in cardiac conduction and their management

A simple classification of atrioventricular block, criteria for diagnosis, and suggested therapy are discussed. The differences between Mobitz I and II second-degree A-V block are reviewed.

Good management of patients who have bundle-branch or other forms of intraventricular block depends on informed judgment which includes consideration of (1) the effect of intraventricular conduction disturbances on the pumping action of the heart, and (2) the likelihood that a specific intraventricular conduction disturbance will be complicated by complete heart block.

Evidence suggests that common forms of intraventricular disturbance, unlike ventricular fibrillation, do not alter significantly the pumping action of the heart. The role of intraventricular conduction disturbances in the genesis of ventricular fibrillation is assessed.

We concluded that only when right bundle-branch block is combined with block of the anterior or posterior fascicle of the left bundle branch is complete heart block sufficiently imminent to warrant special concern. If bilateral block is associated with symptoms of episodic severe bradycardia, pacemaker therapy is indicated.

Cardiac arrhythmias. 1. Anatomy of the conduction system

Some, but not all, cardiac arrhythmias are related to pathologic lesions of the cardiac conduction system. Common atrial dysrhythmias and first-degree atrioventricular (A-V) block rarely are explained on the basis of anatomic lesions in specific sites of the conduction system or its blood supply. Second-degree A-V block of Mobitz type II, which may be a precursor of complete (third-degree) heart block, commonly is associated with fibrotic lesions of uncertain etiology in the branching part of the bundle of His or the bundle branches. Ischemic lesions are found less often, and other pathologic processes rarely are present. Chronic complete heart block most often results from nonspecific, fibrotic interruption of the distal bundle of His, or of the first parts of the bundle branches after their origins. Ischemic lesions are uncommonly the cause of chronic block. High-grade A-V block complicating acute myocardial infarction may be associated with infarction of the A-V conduction system, but often morphologic evidence of ischemia cannot be identified. Congenital variants in anatomy of the conduction system are responsible for some relatively uncommon arrhythmias.

Long-term evaluation of the General Electric cardiac pacemaker

A review of General Electric (G.E.) electronic cardiac pacemakers for symptomatic complete A-V heart block in two sequential three-year periods at the University of Michigan Medical Center indicates that there has been no increase in the useful life of these units. With G.E. epicardial pacemakers failure occurred after an average of 12 months. In the early years the major cause of failure was wire breakage, and the later major cause was battery exhaustion or component failure. Exit block was a major complication. There was no improvement when G.E. catheter pacemakers were used instead of the epicardial type. The Medtronic catheter pacemakers lasted longer, with fewer battery and component failures and no instances of exit block. Although infection was more common with Medtronic pacemakers, secondary to erosion of the power unit or the catheter through the skin, it may be that this complication could be eliminated by locating the battery box beneath the latissimus dorsi muscle in the axilla and by careful catheter placement to avoid pressure necrosis and subsequent cutaneous perforation.

Transthoracic and transvenous pacemakers. A comparative clinical experience with 131 implantable units

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Aetiology of chronic heart block. A clinico-pathological correlation in 65 cases

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Causes of death in patients with complete heart block and aritificial pacemakers

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Permanent ventricular pacemakers. Comparison of transthoracic and transvenous implantation

In the series of 86 patients with the Stokes-Adams syndrome or with symptomatic bradycardia managed with permanently implanted ventricular pacemakers reported on, 35 patients had primary implantation of epicardial leads at thoracotomy and 51 had transvenous endocardial electrodes passed via the jugular venous system for permanent ventricular pacing. The transvenous method of permanent pacemaker implantation appears to be easier to apply with less serious complications and provides the same overall mortality as the transthoracic approach. However, pacemaker failure, both permanent and temporary, is more likely to occur with the transvenous approach.

A series of unique complications and findings noted in the transvenous group were thought to be related to the permanent pacing electrode catheter. These included myothought cardial perforation, pericardial friction rubs, intermittent ventricular pacing, and diaphragmatic stimulation.

The experience suggests that it is reasonable to employ a transvenous pacemaker initially, recognizing that replacement with a transthoracic pacemaker will be necessary in approximately 16% of the patients and remanipulation of the electrode catheter will be needed in another 13%. Therefore, to undertake transvenous permanent implantation of a pacemaker, one must also be prepared to employ the transthoracic approach in a small but significant number of patients.