Effects of intravenous and chronic oral verapamil administration in patients with supraventricular tachyarrhythmias

Periprocedural, early, and long-term risks of pacemaker implantation after atrioventricular nodal re-entry tachycardia ablation: a French nationwide cohort

AIMS

Pacemaker implantation (PI) after atrioventricular nodal re-entry tachycardia (AVNRT) ablation is a dreadful complication. We aimed to assess periprocedural, early, and late risks for PI.

METHODS AND RESULTS

All 27 022 patients who underwent latest AVNRT ablation in France from 2009 to 2017, were identified in the nationwide medicalization database. A control group of 305 152 patients hospitalized for arm, leg, or skin injuries with no history of AVNRT or supraventricular tachycardia were selected. After propensity score matching, both groups had mean age of 53 ± 18 years and were predominantly female (64%). During this 9-year period, 822 of 27 022 (3.0%) AVNRT patients underwent PI, with significant higher risk in propensity-matched AVNRT patients compared to propensity-matched controls [2.9% vs. 0.9%; hazard ratio 3.4 (2.9-3.9), P < 0.0001]. This excess risk was significant during all follow-up, including periprocedural (1st month), early (1-6 months), and late (>6 months) risk periods. Annualized late risk per 100 AVNRT patients was 0.2%. In comparison to controls, excess risk was 0.2% in <30-year-old AVNRT patients; 0.7% in 30-50-year-old; 1.1% in 50-70-year-old and 6.5% over 70-year-olds. Risk for PI was also significantly different according to three procedural factors: centres, experience, and ablation date, with a 30% decrease since 2015.

CONCLUSION

Periprocedural, early, and late risks for PI were higher after AVNRT ablation compared to propensity-matched controls. Longer follow-up is needed as the excess risk seems to persist late after AVNRT ablation.

Sodium Hyaluronate Nanocomposite Respirable Microparticles to Tackle Antibiotic Resistance with Potential Application in Treatment of Mycobacterial Pulmonary Infections

Tuberculosis resistant cases have been estimated to grow every year. Besides Mycobacterium tuberculosis, other mycobacterial species are responsible for an increasing number of difficult-to-treat infections. To increase efficacy of pulmonary treatment of mycobacterial infections an inhalable antibiotic powder targeting infected alveolar macrophages (AMs) and including an efflux pump inhibitor was developed. Low molecular weight sodium hyaluronate sub-micron particles were efficiently loaded with rifampicin, isoniazid and verapamil, and transformed in highly respirable microparticles (mean volume diameter: 1 μm) by spray drying. These particles were able to regenerate their original size upon contact with aqueous environment with mechanical stirring or sonication. The in vitro drugs release profile from the powder was characterized by a slow release rate, favorable to maintain a high drug level inside AMs. In vitro antimicrobial activity and ex vivo macrophage infection assays employing susceptible and drug resistant strains were carried out. No significant differences were observed when the powder, which did not compromise the AMs viability after a five-day exposure, was compared to the same formulation without verapamil. However, both preparations achieved more than 80% reduction in bacterial viability irrespective of the drug resistance profile. This approach can be considered appropriate to treat mycobacterial respiratory infections, regardless the level of drug resistance.

Executive Summary: European Heart Rhythm Association Consensus Document on the Management of Supraventricular Arrhythmias: Endorsed by Heart Rhythm Society (HRS), Asia-Pacific Heart Rhythm Society (APHRS), and Sociedad Latinoamericana de Estimulación Cardiaca y Electrofisiologia (SOLAECE)

This paper is an executive summary of the full European Heart Rhythm Association (EHRA) consensus document on the management of supraventricular arrhythmias, published in Europace. It summarises developments in the field and provides recommendations for patient management, with particular emphasis on new advances since the previous European Society of Cardiology guidelines. The EHRA consensus document is available to read in full at http://europace.oxfordjournals.org.

Efficacy of Verapamil against Ventricular Arrhythmias Induced by Programmed Electrical Stimulation in the Late Myocardial Infarction Phase in Dogs

The aim of the present study was to investigate the antiarrhythmic potential of verapamil in the late myocardial infarction period in conscious dogs. Verapamil was administered in cumulative doses (0·3 + 0·3 mg kg−1). The drug significantly lowered systolic and diastolic blood pressure after both doses. ECG signals showed short-lasting significant decrease in RR and QT intervals together with an increase in QTc interval. The parameters of the atrioventricular conduction system (PQ interval, 2:1 AV-conduction point) were significantly prolonged over the entire observation period. Ventricular effective refractory periods remained unaltered. In contrast to results obtained during acute ischaemia and in the first week thereafter, the present study demonstrates that verapamil moderately increases intraventricular conduction time 14 days after acute myocardial infarction. Verapamil prevented the induction of arrhythmias by programmed electrical stimulation (PES) in only 11% of all induction attempts. The lack of lengthening of refractory periods in the presence of a prolongation of intraventricular conduction time may be responsible for the poor antiarrhythmic efficacy. We conclude that verapamil is only of negligible value for the management of PES-induced ventricular arrhythmias in the late myocardial infarction period.

DEVELOPMENT AND INNOVATION IN CARDIOVASCULAR MEDICINE

The last century has witnessed groundbreaking advances in clinical medicine across the entire diagnostic and therapeutic range, but inequities in access to these advances and innovations continue to be a major challenge to our societies.

Innovations are often initiated by "eureka" moments of discovery, but realising their full potential depend on a process of continuous incremental innovation and interaction involving complex networks. When developing systems that reward, encourage, and sustain medical advances, policy makers must recognise four important factors. First, "incremental" and "continuous" innovation is as important as "breakthrough" innovation. Second, investment across the entire innovation process is needed. Third, the ability of physicians to work across a wide range of scientific fields at "the bench and bedside" is critical to continuous innovation. And fourth, final medical advance that can result from an initial discovery may not be obvious and only occur following interaction with experts and innovations in other fields.

Broad complex atrial fibrillation

The management of broad complex atrial fibrillation is complex and may be a source of morbidity and mortality if not correctly recognized and treated appropriately. We present a case series of 3 patients who were managed in our emergency department after complaints of palpitations. They presented with varying forms of rapid atrial fibrillation that had broad complexes on the 12-lead electrocardiogram. The first 2 patients were treated with calcium channel blockers for rate control, and treatment was complicated by rapid arrhythmia that required cardioversion. The final patient was correctly treated with intravenous procainamide. The diagnosis of Wolff-Parkinson-White syndrome was eventually made in all these patients. Broad complex atrial fibrillation must be treated with respect. Cases with rapid ventricular rate can decompensate from mismanagement due to poor ability to recognize the possibility of Wolff-Parkinson-White syndrome in such patients. Procainamide forms the cornerstone of treatment in hemodynamically stable rapid broad complex atrial fibrillation of unknown origin.

The impact of therapeutic reference pricing on innovation in cardiovascular medicine

Therapeutic reference pricing (TRP) places medicines to treat the same medical condition into groups or 'clusters' with a single common reimbursed price. Underpinning this economic measure is an implicit assumption that the products included in the cluster have an equivalent effect on a typical patient with this disease. 'Truly innovative' products can be exempt from inclusion in the cluster. This increasingly common approach to cost containment allocates products into one of two categories - truly innovative or therapeutically equivalent. This study examines the implications of TRP against the step-wise evolution of drugs for cardiovascular conditions over the past 50 years. It illustrates the complex interactions between advances in understanding of cellular and molecular disease mechanisms, diagnostic techniques, treatment concepts, and the synthesis, testing and commercialisation of products. It confirms the highly unpredictable and incremental nature of the innovation process. Medical progress in terms of improvement in patient outcomes over the long-term depends on the cumulative effect of year after year of painstaking incremental advances. It shows that the parallel processes of advances in scientific knowledge and the industrial 'investment-innovative cycle' involve highly developed sets of complementary capabilities and resources. A framework is developed to assess the impact of TRP upon research and development investment decisions and the development of therapeutic classes. We conclude that a simple categorisation of products as either 'truly innovative' or 'therapeutically equivalent' is inconsistent with the incremental processes of innovation and the resulting differentiated product streams revealed by our analysis. Widespread introduction of TRP would probably have prematurely curtailed development of many incremental innovations that became the preferred 'product of choice' by physicians for some indications and patients in managing the incidence of cardiovascular disease.

Tachycardia-induced cardiomyopathy in a young Boxer dog with supraventricular tachycardia due to an accessory pathway

A 1-year-old male Boxer dog presented with sustained supraventricular tachycardia and tachycardia-induced cardiomyopathy. Conversion to sinus rhythm was achieved initially with intravenous lignocaine and subsequently with oral procainamide. Oral procainamide treatment was relatively successful in maintaining normal sinus rhythm with no side effects apart from a reversible change in coat colour. Electrophysiological studies demonstrated the presence of an accessory pathway connecting the right atrium to the right ventricle and confirmed the diagnosis of orthodromic atrioventricular reciprocating tachycardia. Radiofrequency catheter ablation of the accessory pathway led to permanent resolution of the supraventricular tachycardia and for 9.5 years the dog has had no further signs of cardiac disease. The successful treatment of this condition highlights the importance of differentiating tachycardia-induced cardiomyopathy from dilated cardiomyopathy.

Atrial Fibrillation

Our understanding of the pathophysiology and clinical consequences of atrial fibrillation has led to an evidence-based revolution in the management of atrial fibrillation over the last decade. As we improve in our ability to detect recurrent atrial fibrillation and treat it definitively, the patients who benefit from long-term anticoagulation may change. We can expect, however,that stroke prevention through systemic anticoagulation will be a cornerstone of atrial fibrillation management for decades to come. Innovations in anticoagulation therapy will make the use of these medications safer. Finally, as we further understand the underlying mechanisms of the development of atrial fibrillation, the pursuit of preventative therapy will be an investigational focus of great import.

Selection of drugs in pursuit of rate control strategy

Atrial fibrillation is the most common sustained arrhythmia. Based on multiple large randomized trials, rate control therapy has been shown to be safe and effective and is gaining greater acceptance as a frontline alternative to drugs to maintain sinus rhythm. Adequate rate control can be achieved by atrioventricular nodal blocking agents both in the acute and chronic settings. In refractory patients, other methods such as atrioventricular node ablation can be used to control rate.

New antiarrhythmic agents for atrial fibrillation and atrial flutter

Atrial fibrillation is the most common sustained cardiac arrhythmia and is a frequent reason for antiarrhythmic therapy. Existing antiarrhythmic drugs have important side effects and presently the therapy to maintain sinus rhythm is not superior to a strategy of controlling excessive heart rate. This review summarises current strategies to improve antiarrhythmic therapy for atrial fibrillation. The most important strategies are: i) to develop drugs without proarrhythmic effects--development of drugs devoid of QT prolonging potential is the main strategy; ii) multiple channel-blocking drugs--inspired by the efficacy of amiodarone, several drugs are being developed that have similar electrophysiological properties as amiodarone, but without the extracardiac side effects; iii) drugs that act exclusively in the atria--the atria contain specific potassium channels, and several drugs that act only on these channels are in development; and iv) antiarrhythmic therapy without effects on ion channels--inhibition of the renin-angiotensin system and steroid therapy has been shown to have some effect in the treatment of atrial fibrillation. Many drugs are in development and the therapeutic scenario for treatment of atrial fibrillation may change quickly.

Calcium antagonists

Calcium antagonists were introduced for the treatment of hypertension in the 1980s. Their use was subsequently expanded to additional disorders, such as angina pectoris, paroxysmal supraventricular tachycardias, hypertrophic cardiomyopathy, Raynaud phenomenon, pulmonary hypertension, diffuse esophageal spasms, and migraine. Calcium antagonists as a group are heterogeneous and include 3 main classes--phenylalkylamines, benzothiazepines, and dihydropyridines--that differ in their molecular structure, sites and modes of action, and effects on various other cardiovascular functions. Calcium antagonists lower blood pressure mainly through vasodilation and reduction of peripheral resistance. They maintain blood flow to vital organs, and are safe in patients with renal impairment. Unlike diuretics and beta-blockers, calcium antagonists do not impair glucose metabolism or lipid profile and may even attenuate the development of arteriosclerotic lesions. In long-term follow-up, patients treated with calcium antagonists had development of less overt diabetes mellitus than those who were treated with diuretics and beta-blockers. Moreover, calcium antagonists are able to reduce left ventricular mass and are effective in improving anginal pain. Recent prospective randomized studies attested to the beneficial effects of calcium antagonists in hypertensive patients. In comparison with placebo, calcium antagonist-based therapy reduced major cardiovascular events and cardiovascular death significantly in elderly hypertensive patients and in diabetic patients. In several comparative studies in hypertensive patients, treatment with calcium antagonists was equally effective as treatment with diuretics, beta-blockers, or angiotensin-converting enzyme inhibitors. From these studies, it seems that a calcium antagonist-based regimen is superior to other regimens in preventing stroke, equivalent in preventing ischemic heart disease, and inferior in preventing congestive heart failure. Calcium antagonists are also safe and effective as first-line or add-on therapy in diabetic hypertensive patients. Heart rate-lowering calcium antagonists (verapamil, diltiazem) may have an edge over the dihydropyridines in post-myocardial infarction patients and in diabetic nephropathy. Thus, calcium antagonists may be safely used in the management of hypertension and angina pectoris.

Sinus rhythm maintenance following DC cardioversion of atrial fibrillation is not improved by temporary precardioversion treatment with oral verapamil

OBJECTIVE

To evaluate prospectively the effects of pretreatment with verapamil on the maintenance of sinus rhythm after direct current (DC) cardioversion.

DESIGN

Randomised, active control, open label, parallel group comparison of verapamil versus digoxin.

SETTINGS

Multicentre study in three teaching and three non-teaching hospitals in Sweden.

PATIENTS

100 consecutive patients with atrial fibrillation (AF) of at least four weeks' duration and indications for cardioversion were assigned randomly to two groups, one treated with verapamil (verapamil group) and the other with digoxin (digoxin group) before cardioversion. Fifty patients were assigned randomly to each treatment arm. After dropout of four patients from the digoxin group and seven patients from the verapamil group, data obtained from 89 patients were analysed.

INTERVENTIONS

After randomly assigned pretreatment with either verapamil or digoxin for four weeks, DC cardioversion was performed. If sinus rhythm was restored then verapamil treatment was discontinued.

MAIN OUTCOME MEASURES

The rate of AF recurrence was assessed one, four, eight, and 12 weeks after cardioversion.

RESULTS

6 patients in the verapamil treated group and none in the digoxin treated group reverted to sinus rhythm spontaneously (p < 0.05). DC cardioversion restored sinus rhythm in 24 of 37 (65%) patients in the verapamil group and 41 of 46 patients (89%) in the digoxin group (p < 0.05). After 12 weeks' follow up 28% (13 of 46) of digoxin pretreated patients versus 9% (four of 43) of verapamil pretreated patients remained in sinus rhythm (p < 0.05).

CONCLUSION

Pretreatment with verapamil alone does not improve maintenance of sinus rhythm after DC cardioversion in patients with AF. The rate of spontaneous cardioversion may be improved by verapamil.

Beta-blocker therapy in atrial fibrillation

Beta-blocking agents are a generally established therapy to achieve rate control in patients with AF. With the widely spread belief that rhythm control is the therapy of choice, their use is currently limited to patients that were considered not suitable for specific antiarrhythmic drug therapy. In contrast to that belief, recent studies show that beta-blockers do have some benefit in maintaining sinus rhythm or reducing the frequency of paroxysmal AF and that this benefit might be comparable to conventionally used antiarrhythmic drugs, with the exception of amiodarone. In addition, four prospectively randomized studies recently presented concluded that rate control may be an appropriate aim as a first line approach in patients with AF. Hence, an increased use of beta-blockers in the treatment of patients with AF is to be expected, given the proven prognostic benefit of these drugs in many cardiovascular disorders that are associated with AF. However, no prospective study has yet proven that beta-blockers do exert the same benefit in patients in AF, and one retrospective analysis suggests that there may be differences with regard to the potential benefits of beta-blocker therapy when patients are in AF compared to sinus rhythm. The article summarizes available clinical studies and reviews some experimental data examining the treatment effects of antiadrenergic therapy in AF.

Atrial fibrillation in the elderly: facts and management

Although atrial fibrillation is not widely known by the general public, in developed countries it is the most common arrhythmia. The incidence increases markedly with advancing age. Thus, with the growing proportion of elderly individuals, atrial fibrillation will come to represent a significant medical and socioeconomic problem. The consequences of atrial fibrillation have the greatest impact. The risk of thromboembolism is well known; other outcomes of atrial fibrillation are less well recognised, such as its relationship with dementia, depression and death. Such consequences are responsible for diminished quality of life and considerable economic cost. Atrial fibrillation is characterised by rapid and disorganised atrial activity, with a frequency between 300 and 600 beats/minute. The ventricles react irregularly, and may contract rapidly or slowly depending on the health of the conduction system. Clinical symptoms are varied, including palpitations, syncope, dizziness or embolic events. Atrial fibrillation may be paroxysmal, persistent or chronic, and a number of attacks are asymptomatic. Suspicion or confirmation of atrial fibrillation necessitates investigation and, as far as possible, appropriate treatment of underlying causes such as hypertension, diabetes mellitus, hypoxia, hyperthyroidism and congestive heart failure. In the evaluation of atrial fibrillation, cardiac exploration is invaluable, including electrocardiogram (ECG) and echocardiography, with the aim of detecting cardiac abnormalities and directing management. In elderly patients (arbitrarily defined as aged >75 years), the management of atrial fibrillation varies; it requires an individual approach, which largely depends on comorbid conditions, underlying cardiac disease, and patient and physician preferences. This management is essentially based on pharmacological treatment, but there are also nonpharmacological options. Two alternatives are possible: restoration and maintenance of sinus rhythm, or control of ventricular rate, leaving the atria in arrhythmia. Pharmacological options include antiarrhythmic drugs, such as class III agents, beta-blockers and class IC agents. These drugs have some adverse effects, and careful monitoring is necessary. The nonpharmacological approach to atrial fibrillation includes external or internal direct-current cardioversion and new methods, such as catheter ablation of specific foci, an evolving science that has been shown to be successful in a very select group of atrial fibrillation patients. Another serious challenge in the management of chronic atrial fibrillation in older individuals is the prevention of stroke, its primary outcome, by choosing an appropriate antithrombotic treatment (aspirin or warfarin). Several risk-stratification schemes have been validated and may be helpful to determine the best antithrombotic choice in individual patients.

Complex AV nodal dynamics during ventricular-triggered atrial pacing in humans

In vitro experiments have shown that the complexity of atrioventricular nodal (AVN) conduction dynamics increases with heart rate. Although complex AVN dynamics (e.g., alternans) have been observed clinically, human AVN dynamics during rapid pacing have not been systematically investigated. We studied such dynamics during ventricular-triggered atrial pacing in 37 patients with normal AVN function (18 patients with dual AVN pathway physiology and 19 patients without). Alternans, which always resulted from single pathway conduction, occurred in 18 patients. In 16 patients (3 of whom also had alternans), quasisinusoidal AVN conduction oscillations occurred (mean frequency 0.02 Hz); such oscillations have not been previously reported. There were no significant differences in the dynamics for patients with or without dual AVN pathways. To illuminate the governing dynamic mechanism, a second atrial pacing trial was performed on 12 patients after autonomic blockade. Blockade facilitated alternans but inhibited oscillations. This study suggests that rapid AVN excitation in vivo can lead to autonomically mediated AVN conduction oscillations or single pathway alternans that are a function of inherent nonlinear dynamic AVN tissue properties.

Nonlinear-dynamical arrhythmia control in humans

Nonlinear-dynamical control techniques, also known as chaos control, have been used with great success to control a wide range of physical systems. Such techniques have been used to control the behavior of in vitro excitable biological tissue, suggesting their potential for clinical utility. However, the feasibility of using such techniques to control physiological processes has not been demonstrated in humans. Here we show that nonlinear-dynamical control can modulate human cardiac electrophysiological dynamics by rapidly stabilizing an unstable target rhythm. Specifically, in 52/54 control attempts in five patients, we successfully terminated pacing-induced period-2 atrioventricular-nodal conduction alternans by stabilizing the underlying unstable steady-state conduction. This proof-of-concept demonstration shows that nonlinear-dynamical control techniques are clinically feasible and provides a foundation for developing such techniques for more complex forms of clinical arrhythmia.

Interactions between cardiovascular treatments and anaesthesia

Circulatory stability is one of the main objectives of the perioperative management of high-risk patients. Most of these patients are chronically treated with cardiovascular treatments, which interfere with the functioning of several physiological systems aimed at maintaining the circulatory status when the loading conditions of the heart deteriorate, or limit the compensatory mechanisms used when metabolic needs increase. Taking into account the pharmacology of these medications, their repercussions on perioperative haemodynamics and their potential beneficial effects on regional circulations, it has become possible to determine whether or not they must be given or withdrawn perioperatively.

Pharmacologic management of atrial fibrillation: current therapeutic strategies

BACKGROUND

Atrial fibrillation (AF), the most common form of sustained arrhythmia, is associated with a frightening risk of embolic complications, tachycardia-related ventricular dysfunction, and often disabling symptoms. Pharmacologic therapy is the treatment used most commonly to restore and maintain sinus rhythm, to prevent recurrences, or to control ventricular response rate.

METHODS

This article reviews published data on pharmacologic treatment and discusses alternative systems to classify AF and to choose appropriate pharmacologic therapy.

RESULTS

AF is either paroxysmal or chronic. Attacks of paroxysmal AF can differ in duration, frequency, and functional tolerance. In the new classification system described, 3 clinical aspects of paroxysmal AF are distinguished on the basis of their implications for therapy. Chronic AF usually occurs in association with clinical conditions that cause atrial distention. The risk of chronic AF is significantly increased by the presence of congestive heart failure or rheumatic heart disease. Mortality rate is greater among patients with chronic AF regardless of the presence of coexisting cardiac disease. The various options available for the treatment of chronic AF include restoration of sinus rhythm or control of ventricular rate. Cardioversion may be accomplished with pharmacologic or electrical treatment. For patients in whom cardioversion is not indicated or who have not responded to this therapy, antiarrhythmic agents used to control ventricular response rate include nondihydropyridine calcium antagonists, digoxin, or beta-blockers. For patients who are successfully cardioverted, sodium channel blockers or potassium channel blockers such as sotalol, amiodarone, or a pure class III agent such as dofetilide, a selective potassium channel blocker, may be used to prevent recurrent AF to maintain normal sinus rhythm.

CONCLUSIONS

The ultimate choice of the antiarrhythmic drug will depend on the presence or absence of structural heart disease. An additional concern with chronic AF is the risk of arterial embolization resulting from atrial stasis and the formation of thrombi. In patients with chronic AF the risk of embolic stroke is increased 6-fold. Therefore anticoagulant therapy should be considered in patients at high risk for embolization. Selection of the appropriate treatment should be based on the concepts recently developed by the Sicilian Gambit Group (based on the specific channels blocked by the antiarrhythmic agent) and on clinical experience gained over the years with antiarrhythmic agents. For example, termination of AF is best accomplished with either a sodium channel blocker (class I agent) or a potassium channel blocker (class III agent). In contrast, ventricular response rate is readily controlled by a beta-blocker (propranolol) or a calcium channel blocker (verapamil). Alternatively, antiarrhythmic drug therapy may be chosen based on the Vaughan-Williams classification, which identifies the cellular electrophysiologic effects of the drug.

Cost-effective management of acute atrial fibrillation: role of rate control, spontaneous conversion, medical and direct current cardioversion, transesophageal echocardiography, and antiembolic therapy

Management strategies for the acute treatment of atrial fibrillation (AF) include: (1) the use of intravenous drugs for rate control, (2) drug termination, or (3) direct current (DC) cardioversion. Delays in cardioversion can promote atrial remodeling and add thromboembolic risk. Rate control awaiting spontaneous or pharmacologic conversion may be a cost-effective strategy in patients presenting with recent onset of symptoms. Early DC cardioversion can be cost-effective and minimize antiembolic therapy issues in the acute setting. In patients presenting with AF of unknown or >48 hours' duration, rate control and therapeutic warfarin for 3-4 weeks followed by medical or DC cardioversion is standard practice. However, delays in conversion promote atrial remodeling that makes restoration of sinus rhythm more difficult and increases the likelihood of postcardioversion AF recurrence. Transesophageal echocardiography can identify patients at low risk for a cardioversion-related embolic event and allows cardioversion to be performed earlier, thereby minimizing atrial remodeling.

Clinical features of Wolff-Parkinson-White syndrome

Wolff-Parkinson-White syndrome is the most common form of ventricular preexcitation. Understanding this syndrome is fundamental for anyone interested in learning about arrhythmias. This review addresses (1) the historic sequence of events that led to the understanding of this syndrome; (2) the pathologic, embryologic, and electrophysiologic properties of accessory pathways; (3) the epidemiology and genetics of this syndrome; (4) the clinical diagnosis of this syndrome, with special emphasis on the arrhythmias that patients with ventricular preexcitation are predisposed to; and (5) the therapy for patients with Wolff-Parkinson-White syndrome.

The peri-operative management of atrial fibrillation

Atrial fibrillation is a common arrhythmia frequently seen in surgical patients. The onset of new atrial fibrillation during the peri-operative period is less common. There are many possible precipitating factors, although volatile agents themselves may have an antifibrillatory action. The management of atrial fibrillation includes removal of any precipitating factors and treatment of the arrhythmia itself. Immediate management of acute-onset atrial fibrillation is usually direct current cardioversion. Alternatively, anti-arrhythmic drugs can be used to achieve cardioversion. In patients with rapid, chronic atrial fibrillation or those refractory to cardioversion, priority is given to control of the ventricular rate. Thrombo-embolism is a significant risk if atrial fibrillation is paroxysmal or persists for more than 48 h.

Rhythm management in atrial fibrillation--with a primary emphasis on pharmacological therapy: Part 1

Atrial fibrillation (AF) is the most common, sustained, symptomatic tachyarrhythmia that clinicians are called upon to manage. Management strategies include ventricular rate control coupled with anticoagulation, versus restoration and maintenance of sinus rhythm. Rate control may be achieved pharmacologically, with agents that impair AV nodal conduction directly and/or by increasing parasympathetic/sympathetic balance, or by modifying or ablating the AV nodal region anatomically. Rhythm control may be achieved by electrical or pharmacological conversion followed by maintenance of sinus rhythm by pharmacological (or occasionally ablative) therapies. This article will present current approaches to rate and rhythm control issues in AF. Part 1, the current manuscript, details approaches to rate control and includes a drug selection algorithmic conclusion. It also introduces the subject of the pursuit of sinus rhythm. Parts 2 and 3, to be published in subsequent editions of PACE, will deal with therapeutic measures to restore and maintain sinus rhythm.

Recognition and Management of Cardiac Arrhythmias: Part I. General Principles and Supraventricular Tachyarrhythmias

Management of cardiac arrhythmias has undergone major changes in the last few years. In the first part of this review, general principles of arrhythmia diagnosis are discussed. New techniques such as event recording and signal-averaged electrocardiography have a significant role in the clinical management of arrhythmias. Many new antiarrhythmic drugs are now available. Suppression of premature ventricular contractions to prevent malignant ventricular arrhythmias has been demonstrated to be an ineffective strategy. Implantable defibrillators and radio frequency ablation have revolutionized the treatment of arrhythmias. Differentiation of various supraventricular tachycardias has become very important since some these arrhythmias may be cured by radiofrequency ablation. Diagnosis and treatment of common supraventricular arrhythmias are discussed.

Early recurrences of atrial fibrillation after electrical cardioversion: a result of fibrillation-induced electrical remodeling of the atria?

OBJECTIVES

We sought to investigate whether, in humans, the timing and incidence of a relapse of atrial fibrillation (AF) during the first month after cardioversion indicates the presence of electrical remodeling and whether this could be influenced by prevention of intracellular calcium overload during AF.

BACKGROUND

Animal experiments have shown that AF induces shortening of the atrial refractory period, resulting in an increased vulnerability for reinduction of AF. This electrical remodeling was completely reversible within 1 week after cardioversion of AF and was presumably related to intracellular calcium overload.

METHODS

Using transtelephonic monitoring in 61 patients cardioverted for chronic AF, we evaluated the daily incidence of recurrence of AF and determined, by Cox regression analysis, the influence of patient characteristics and medication on relapse of AF.

RESULTS

During 1 month of follow-up, 35 patients (57%) had a relapse of AF, with a peak incidence during the first 5 days after cardioversion. Furthermore, in patients with a recurrence of AF, there was a positive correlation between the duration of the shortest coupling interval of the premature atrial beats after cardioversion and the timing of the recurrence of AF (p = 0.0013). Multivariate analysis revealed that the use of intracellular calcium-lowering drugs during AF was the only significant variable related to maintenance of sinus rhythm after cardioversion (p = 0.03).

CONCLUSIONS

The daily distribution of recurrences of AF suggests a temporary vulnerable electrophysiologic state of the atria. Use of intracellular calcium-lowering medications during AF appeared to reduce recurrences, possibly due to a reduction of electrical remodeling during AF.

Cardiac effects of calcium antagonists in systemic hypertension

The calcium antagonists are a class of heterogeneous drugs, with a wide spectrum of direct and indirect cardiac effects that vary a great deal from one drug to another and depend upon formulation and duration of action. Calcium antagonists act by decreasing total peripheral resistance to lower arterial pressure. As a consequence, reflex tachycardia, increased cardiac output, and increased plasma catecholamine and plasma renin activity are commonly seen, particularly with the initial dose and with short-acting dihydropyridines. The abrupt vasodilation can paradoxically elicit angina and even acute myocardial infarction. These hemodynamic and neuroendocrine changes are less pronounced with the long-acting formulations. Most calcium antagonists diminish automaticity of the sinus node, slow conduction in the atrioventricular node, and have little, if any, effect on the automaticity of the myocytes. The dihydropyridines generally have less effect on automaticity and cardiac conduction than nondihydropyridines. The negative inotropic effect is most profound with nondihydropyridines and is greatly reduced or absent with newer dihydropyridines, such as isradipine, felodipine, amlodipine, and nisoldipine. Long-acting calcium antagonists generally improve myocardial oxygenation by unloading the heart, increasing coronary blood flow, and reducing myocardial oxygen consumption. Thus, calcium antagonists have a variety of beneficial effects in patients with hypertensive heart disease: they reduce left ventricular hypertrophy and its sequelae, such as ventricular dysrhythmias, impaired filling and contractility, and myocardial ischemia. Ongoing studies should provide a more conclusive answer regarding the efficacy and safety of calcium antagonists.

Management of perioperative arrhythmias

Electrocardiography was the first application of electronic monitoring to anesthesia care. The detection of arrhythmias remains the most important use of this technology today. Several predisposing factors tend to emerge when perioperative arrhythmias are evaluated. These are the anesthetic given, the site of surgery, abnormalities of blood gases or electrolytes, tracheal intubation, reflexes such as vagal slowing and the oculocardiac reflex, stimulation of the central nervous system, the presence of preexisting heart disease, and the use of intracardiac devices. In the evaluation of cardiac arrhythmias, several facts need to be determined. The most important is to determine if there is an underlying complication of anesthesia and surgery that may explain the arrhythmia. In addition, it is vital to evaluate the heart rate, the regularity, the number of P waves per QRS, and the configuration of the QRS. The anesthesiologist needs to determine whether the rhythm is dangerous to the patient and whether it requires treatment. Prompt evaluation and management of perioperative arrhythmias reduce anesthetic morbidity and mortality. This article reviews the causes and pharmacological treatment of major abnormalities of atrial and ventricular cardiac arrhythmias occurring in the perioperative period.

Alternation of atrioventricular nodal conduction time during atrioventricular reentrant tachycardia: are dual pathways necessary?

INTRODUCTION

Alternation of atrial cycle length and AV nodal conduction time (NCT) is often observed during AV reentrant tachycardia. Both AV nodal dual pathway and rate-dependent function have been postulated to be involved in this phenomenon. This study was designed to determine the respective role of these two mechanisms in the alternation observed in an in vitro model of orthodromic AV reentrant tachycardia.

METHODS AND RESULTS

The tachycardia was produced by detecting each His-bundle activation and stimulating the atrium after a retrograde delay, thereby simulating retrograde pathway conduction, in six isolated rabbit heart preparations. After a 5-minute stabilization period at a fast rate, the retrograde delay was decremented by 2 msec every minute until nodal blocks occurred. We observed a sequential alternation of the cycle length and NCT in four preparations in the short retrograde delay range. The magnitude of the alternation gradually increased as the retrograde delay was decreased and reached 4.6 +/- 0.5 msec during 1:1 conduction. The alternation increased further just prior to termination of the tachycardia by an AV nodal block. None of the preparations showed discontinuous AV nodal recovery curves. Moreover, an electrode positioned over the endocardial surface of the node showed that the alternation developed distally to the nodal inputs, which are believed to constitute a major component of dual pathways. A mathematical model predicted the alternation from known characteristics of rate-dependent nodal functional properties.

CONCLUSIONS

NCT and cycle length alternation can arise during orthodromic AV reentrant tachycardia when the retrograde delay is sufficiently short. The characteristics of the alternation, presence of continuous recovery curves, intranodal location of the alternation, and mathematical modeling suggest that the alternation is predictable from the known functional properties of the AV node without postulating dual pathway physiology.

Effects of verapamil, propranolol, and procainamide on adenosine-induced negative dromotropism in human beings

Adenosine, verapamil, propranolol, and procainamide are widely used antiarrhythmic drugs. The interactions among them are still not known in human beings. Adenosine-induced negative dromotropic effects were assessed by rapid bolus injection of adenosine during constant high right atrial pacing in each patient. The initial dose of adenosine was 0.5 mg and was followed by a stepwise increment of 0.5 mg until atrioventricular (AV) nodal block occurred. The negative dromotropic actions of adenosine were examined in the control state and in the following three protocols in three groups of patients: (1) In 12 patients (group 1), intravenous verapamil, 0.15 mg/kg, was given; (2) In 12 patients (group 2), intravenous propranolol, 0.1 mg/kg, was given; and (3) in 10 patients (group 3), intravenous procainamide, 15 mg/kg, was given. The dose-response curves of adenosine on AV nodal conduction were almost identical in the control state and after verapamil, propranolol, or procainamide injection. However, verapamil, in contrast to propranolol, significantly reduced the dose of adenosine required to produce AV nodal block, from 4.4 +/- 0.7 mg to 2.7 +/- 0.3 mg (p < 0.01). Of note, procainamide exerted no significant effects on adenosine-induced negative dromotropism on AV nodal conduction or AV nodal block. In conclusion, the negative dromotropic effects of adenosine are preserved and independent even in the presence of verapamil, propranolol, or procainamide. Both verapamil and propranolol can exhibit additive effects with adenosine in prolonging AV nodal conduction time; however, only verapamil can reduce the dose of adenosine required to produce AV nodal block. This finding indicates that the dose of adenosine may be reduced for patients who have already been treated with verapamil.

Electrophysiological effects of clentiazem, a new Ca2+ antagonist, on rabbit hearts

Electrophysiological effects of clentiazem, a new 1,5-benzothiazepine type Ca(2+) antagonist, were examined in comparison with those of diltiazem in excised rabbit heart preparations. In Langendorff-perfused hearts electrically driven at basic cycle lengths of 400-500 ms, clentiazem (10(-8)-10(-6)M) and diltiazem (10(-8)-10(-6)M) caused a concentration-dependent prolongation of the atrio-His bundle conduction time (A-H interval) without affecting the His bundle-ventricular conduction time (H-V interval). The effects of clentiazem were equivalent to those of diltiazem. In isolated rabbit atrioventricular (A-V) node preparations electrically driven at 400- to 500-ms intervals, clentiazem and diltiazem at >10(-6)M concentrations produced concentration-dependent decreases in action potential amplitude (APA), maximum rate of depolarization (V max), and shortened action potential duration at 20 and 50% repolarization (APD(20) and APD(50)), whereas APD(90) was little affected. Application of 10(-6)M clentiazem prolonged effective refractory period (ERP) of the A-V node by approximately 7% of the control, an effect similar to that of diltiazem. In spontaneously beating sinoatrial (S-A) node preparations, clentiazem l0(-6)M or the higher concentration significantly decreased APA, V(max), and slope of slow diastolic depolarization, while reducing the maximum diastolic potential. The inhibitory effects of clentiazem showed strong suppression of APA and V(max) by 31.1 and 47.2% of the control, respectively, whereas both clentiazem (10(-7)-10(-5)M) and diltiazem (10(-7)-10(-5)M) had no effects on parameters of ventricular APs. These results suggest that dentiazem, like diltiazem, has a preferential inhibitory action on cardiac slow Ca(2+) channels.

The antiarrhythmic effect of verapamil on atrioventricular re-entry in the Wolff-Parkinson-White syndrome: a computer model study

Verapamil is supposed to suppress the initiation of circus movement supraventricular tachycardia by affecting the atrioventricular node. In electrophysiological tests, programmed stimulation is usually performed by using the same location for pacing and premature stimulus. Spontaneous ectopic activity starts from a different location than the sinus node and can therefore find altered re-entry conditions. In this study a 3D computer model based on Huygen's principle is used for simulation of the spread of excitation in the human heart in combination with a posterobasal, right or left lateral accessory pathway (AP). The effect of verapamil on properties of the atrioventricular node were modelled by prolonging the effective refractory period and basal conduction time. For each of the three APs, ectopic foci at the atrial base and between sinus node and AP were modelled at various coupling intervals for investigating re-entrant activation. In the control state (without verapamil) only orthodromic echoes were found. The maximum echo zone (EZ) range was found near the AP. If stimuli were selected further away from the AP on the atrial basis, the EZ range decreased until no EZ was found. The EZ range decreased from it's maximum value near the AP, towards the difference of the effective refractory periods between AP and AV-node near the sinus node Verapamil abolished the EZ in case of a posteroseptal AP. For a lateral AP the administration of verapamil resulted in an orthodromic and antidromic EZ depending on the atrial premature activation site. A maximum orthodromic EZ was found for premature stimuli near the AP. As stimulus site moved away from the AP, the EZ range first decreased continuously to zero leading eventually to an antidromic EZ. These findings suggest the important influence of the site of premature stimuli with respect to the accessory pathway and AV-node on the inducibility of atrial re-entry.

Long-term prevention of atrial fibrillation after coronary artery bypass surgery: comparison of quinidine, verapamil, and amiodarone in maintaining sinus rhythm

AIM OF STUDY

To evaluate the necessity and efficacy of quinidine fumarate, verapimil, or amiodarone prophylaxis for sinus rhythm maintenance in patients who experienced atrial fibrillation after coronary artery bypass surgery.

METHODS

Between 1992 and 1995, this prospective, randomized, placebo-controlled study examined 120 patients in whom atrial fibrillation occurred and was restored to sinus rhythm by pharmacological therapy or direct current cardioversion in the immediately postoperative period after coronary artery by-pass surgery. There were no significant differences in perioperative characteristics among the patients, who were randomly separated into four groups in the course of discharge. In group 1 (n = 30), patients did not receive antiarrhythmic drugs. Quinidine fumarate was given in group 2 (n = 30), verapimil in group 3 (n = 30), and amiodarone in group 4 (n = 30). Patients were monitored six times over a 90-day postoperative period by 24-hour Holter monitoring and routine examination.

RESULTS

The recurrent atrial fibrillation usually developed within 15 days of discharge. Atrial fibrillation occurred in one patient (3.33%) in group 1, and two each (6.66%) in groups 2, 3, and 4. Atrial fibrillation was asymptomatic and occurred with slow ventricular response in groups 3 and 4. Side effects occurred in 5 patients (16.6%) given quinidine, 1 patient given amiodarone, but in no patient given verapimil.

CONCLUSIONS

There were no significant differences in the maintenance of sinus rhythm among the four groups, so we suggest that long-term prevention of atrial fibrillation in patients with coronary artery bypass grafting was not necessary at the postdischarge period.