Safety and efficacy of intravenous diltiazem in atrial fibrillation or atrial flutter

The Safety and Efficacy of Verapamil Versus Diltiazem Continuous Infusion for Acute Rate Control of Atrial Fibrillation at an Academic Medical Center

Purpose

Due to critical shortages of intravenous diltiazem in 2018, the Ohio State University Wexner Medical Center (OSUWMC) adopted intravenous verapamil as an alternative. However, there is a paucity of data supporting the use of intravenous verapamil infusions for rate control in the acute treatment of atrial arrhythmias. The purpose of this study was to determine the safety and efficacy of intravenous verapamil as compared with diltiazem for the acute treatment of atrial arrhythmias.

Methods

This retrospective, case-control study compared patients who received verapamil infusions between June 1 and September 30, 2018, with patients who received diltiazem infusions between June 1 and September 30, 2017, at OSUWMC. Patients were matched 1:1 based on age, sex, and the presence of comorbid heart failure with reduced ejection fraction (≤40%).

Results

A total of 73 patients who received at least 1 verapamil infusion and 73 patients who received at least 1 diltiazem infusion met inclusion criteria. The composite need for inotrope or vasopressor was similar for both groups (5% with verapamil versus 4% with diltiazem, P = .999). The rate of hypotension was similar between groups (37% versus 33% experiencing a systolic blood pressure <90 mm Hg, P = .603, and 27% versus 23% experiencing a mean arterial pressure <65 mm Hg, P = .704), as was the rate of bradycardia (19% versus 18%, P = .831). The efficacy outcomes of this study were similar for both groups, with 89% of patients in the verapamil group and 90% of patients in the diltiazem group achieving a heart rate less than 110 beats per minute (P = .785).

Conclusion

Intravenous verapamil and diltiazem infusions had similar safety and efficacy outcomes when used for acute treatment of atrial arrhythmias in the institutional setting.

Weight-based versus non-weight-based diltiazem dosing in the setting of atrial fibrillation with rapid ventricular response

PURPOSE

There is conflicting evidence to support the superiority of weight-based (WB) dosing of intravenous (IV) diltiazem over non-weight-based (NWB) dosing strategies in the management of atrial fibrillation (AFib) with rapid ventricular response (RVR).

METHODS

A retrospective review evaluated patients presenting to the emergency department (ED) in AFib with RVR and receiving IV diltiazem from 2015 to 2018. Those receiving a NWB dose were compared with those receiving a WB dose based on actual body weight (ABW). Secondary analyses evaluated safety profiles of the regimens and compared response in groups defined by ABW or ideal body weight (IBW).

RESULTS

A total of 371 patients were included in the analysis. No significant difference was observed in achieving a therapeutic response (66.5% vs. 73.1%, p = 0.18) or adverse events between the groups. Patients receiving a WB dose were significantly more likely to have a HR < 100 bpm than those receiving a NWB dose (40.9% vs. 53.5%, p = 0.01). When groups were defined by IBW, WB dosing was associated with a significantly higher incidence of achieving a therapeutic response (62.7% vs. 74.3%, p = 0.02).

CONCLUSION

In patients presenting with AF with RVR, there was no significant difference in achieving a therapeutic response between the two strategies. A WB dosing approach did result in a greater proportion of patients with a HR < 100 bpm. The utilization of IBW for WB dosing may result in an increased achievement of a therapeutic response.

Frequency of "on-label" use of intravenous diltiazem for rate control in patients with acute-onset atrial fibrillation or atrial flutter

Purpose

The study was designed to characterize "on-label" use of i.v. diltiazem in patients with acute atrial fibrillation or flutter (AFF).

Methods

An IRB-approved, single-center, retrospective, observational design was used. Eligible patients had acute AFF with heart rate >120 bpm and received i.v. diltiazem from June 1, 2012, to June 30, 2014. The primary outcome was frequency of on-label use of i.v. diltiazem, defined as use of at least one FDA-approved weight-based bolus dose followed by an infusion, if appropriate, in the absence of contraindications.

Results

A total of 300 patients were screened; 97 patients were included for analysis. I.V. diltiazem was used on-label in only 14 patients (14%). Of the 96 patients who received an initial diltiazem bolus injection, the median dose was significantly higher in patients for whom the diltiazem dose was on-label, as follows: 17.5 mg (interquartile range [IQR]), 10-20 mg vs. 10.0 mg (IQR, 10-20 mg), p < 0.02). Twenty-nine patients (35%) in the off-label group had a therapeutic response to diltiazem alone compared with 8 patients (57%) in the on-label group (p = 0.11). More patients treated with off-label diltiazem bolus injection required additional rate control medications (41% vs. 7%, p < 0.04).

Conclusion

In most patients, i.v. diltiazem was not used in accordance with FDA labeling. For most, i.v. diltiazem doses were lower than recommended and many of these patients required additional rate control medications to achieve a therapeutic response.

Comparison of Weight-Based Dose vs. Standard Dose Diltiazem in Patients with Atrial Fibrillation Presenting to the Emergency Department

BACKGROUND

Despite evidence-based recommended weight-based (WB) dosing of diltiazem for the initial treatment of atrial fibrillation (AF) with rapid ventricular response (RVR), many providers utilize lower initial doses of diltiazem.

OBJECTIVE

We sought to determine whether a low, standard dose of diltiazem is noninferior to WB diltiazem as an initial bolus dose in the treatment of AF with RVR.

METHODS

This retrospective review included patients who presented to the emergency department (ED) of an urban, academic tertiary medical center experiencing AF with RVR from November 2010 to August 2014. Adult patients were categorized by the dose of diltiazem received; 10 mg standard dose or 0.2-0.3 mg/kg WB dose. The primary outcome of successful treatment was defined as a composite of the following parameters 15 min after the initial bolus dose: heart rate (HR) < 100 beats/min, reduction of HR ≥ 20%, or a conversion to normal sinus rhythm.

RESULTS

Four hundred and fifty-six patients who received diltiazem were included for study evaluation (standard dose: n = 255 patients, WB: n = 201 patients). Baseline characteristics, medical history, and medication use before ED presentation were similar between the groups. Significant differences at baseline between the groups included weight and HR at presentation. The primary outcome of successful treatment was attained in 60.8% of the standard dose patients and 68.7% of the WB patients (p = 0.082).

CONCLUSIONS

In patients presenting to the ED, we found that standard dose diltiazem was noninferior to WB dosing in the initial treatment of AF with RVR.

Conversion of Atrial Fibrillation to Sinus Rhythm During Treatment With Intravenous Esmolol or Diltiazem: A Prospective, Randomized Comparison

Prior studies have suggested that intravenous diltiazem reduces the probability of spontaneous conversion of atrial fibrillation (AF) to sinus rhythm in the electrophysiology laboratory and in patients with postoperative AF. Whether diltiazem exerts the same effect in patients presenting to the emergency department (ED) with spontaneous AF is unclear. Fifty patients presenting to the ED with new-onset or paroxysmal AF and a rapid ventricular rate (>100 beats per minute) were randomly assigned to receive intravenous diltiazem or esmolol during the first 24 hours of presentation. Conversion to sinus rhythm occurred in 10 patients (42%) in the diltiazem group compared with 10 patients (39%) in the esmolol group ( P = 1.0). Diltiazem does not decrease the likelihood of spontaneous conversion of AF to sinus rhythm in the ED setting.

Clinical Experience with Diltiazem in the Treatment of Cardiovascular Diseases

Abstract

Cardiovascular diseases are the leading cause of death in the world. Coronary artery diseases, atrial fibrillation or hypertensive heart disease, are among the most important cardiovascular disorders. Hypertension represents a significant risk factor for cardiovascular mortality; thus, control of high blood pressure has become a priority to prevent major complications. Although the choice of drugs for treating hypertension remains controversial, extensive clinical evidences point to calcium channel blockers as first-line agents. Diltiazem, a non-dihydropyridine calcium channel blocker, is an effective and safe antihypertensive drug, alone or in combination with other agents. Diltiazem lowers myocardial oxygen demand through a reduction in heart rate, blood pressure, and cardiac contractility, representing also a good alternative for the treatment of stable chronic angina. Furthermore, diltiazem reduces conduction in atrioventricular node, which is also useful for heart rate control in patients with atrial fibrillation. In this review, clinical experts highlight studies on diltiazem effectiveness and safety for the treatment of several cardiovascular diseases and make evidence-based recommendations regarding the management of diltiazem in the clinical practice.

Funding

Lacer Spain.

Advance of studies on anti-atherosclerosis mechanism of berberine

Coptis Chinensis is a traditional Chinese medicine herb that has the effect of clearing heat and drying dampness, purging fire to eliminate toxin. Berberine is the main alkaloid of Coptis Chinensis, and, recent researches showed that berberine had the effect of anti-atherosclerosis. This paper reviewed the anti-atherosclerosis mechanism of berberine, which may be related to regulating lipids, anti-inflammation, decompression, reducing blood sugar, and inhibiting vascular smooth muscle cell proliferation.

Postoperative Care of the Cardiac Surgical Patient

The subspecialty of interventional cardiology began in 1977. Since then, the discipline of interventional cardiology has matured rapidly, particularly with regards to ischemic heart disease. As a result, more patients are undergoing percutaneous catheter interventional therapy for ischemic heart disease and fewer patients are undergoing surgical myocardial revascularization. Those patients referred for surgical revascularization are generally older and have more complex problems. Furthermore, as the population ages more patients are referred to surgery for valvular heart disease. The result of these changes is a population of surgical patients older and sicker than previously treated.

Pharmacologic approaches to rhythm versus rate control in atrial fibrillation—where are we now?

Until recently, contemporary drug treatment of atrial fibrillation (AF) focused primarily on restoration and maintenance of sinus rhythm, predicated on the belief that if AF is abolished then problems associated with AF would be abolished too. Recently completed clinical trials using drug therapy and comparing maintenance of sinus rhythm with control of ventricular rate have challenged this assumption, showing that simple control of ventricular rate with anticoagulation is an acceptable primary therapy, notably in older patients with persistent AF, minimally symptomatic or asymptomatic, and at increased risk for thromboembolic events. However, rate control and anticoagulation is not a panacea; existing trial results should not be interpreted to mean all patients should be treated with the rate control approach. Despite the limited efficacy and poor safety of current antiarrhythmic drugs, strategies for maintenance of sinus rhythm remain justified in many patients, such as those with first-episode AF, highly symptomatic patients, younger patients, and those with a history of congestive heart failure (CHF). Commonly used current and some investigational agents designated for "rhythm control" have enough pharmacologic overlap with rate control agents to be considered to have a dual mode of action, simultaneously addressing both rhythm and rate control. Furthermore, there is much interest in non-pharmacologic therapies, such as radiofrequency ablation, for rhythm control. The lack of appropriately designed and controlled trials at this time makes it difficult to determine the place of radiofrequency ablation and its impact on the rhythm versus rate question.

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 channel blocker class heterogeneity: select aspects of pharmacokinetics and pharmacodynamics

Calcium channel blockers (CCBs) comprise a heterogeneous group of compounds with unique structures and pharmacologic characteristics. These agents are employed in the treatment of hypertension, coronary ischemia, and/or supraventricular arrhythmias. CCBs are both substrates for, and in the instance of verapamil and diltiazem inhibitors of, cytochrome P450 3A4. In the case of verapamil and diltiazem, this inhibitory effect increases the likelihood of drug-drug interactions with other compounds similarly metabolized by cytochrome P450 3A4. Much of the debate with reference to a cardiovascular risk for CCBs has been quieted with the advent of sustained-release delivery systems that offer a more gradual rate of drug delivery. The most common side effects with CCBs are vasodilatory in nature and include peripheral edema, flushing, and headache. Despite the potential for side effects with CCBs, their potent blood pressure-lowering effect makes them a prerequisite for blood pressure control in many patients.

Calcium chloride before i.v. diltiazem in the management of atrial fibrillation

Diltiazem is commonly used to treat atrial fibrillation or flutter (AFF) with rapid ventricular response (RVR). Although it is very effective for rate control, up to an 18% prevalence of reported diltiazem-induced hypotension [defined by systolic blood pressure (SBP) < 90 mm Hg], and a mean of 9.7% hypotension have been reported from several studies totaling over 450 patients. This hypotension may complicate therapy. Our objective was to determine if calcium chloride (CaCl(2)) pre-treatment would blunt a SBP drop after i.v. diltiazem, while allowing diltiazem to maintain its efficacy. A prospective, randomized, double-blind, placebo-controlled study was conducted. Seventy-eight patients with AFF and a ventricular rate of >/= 120 beats per minute were enrolled. Half received i.v. CaCl(2) pre-treatment; the other half received placebo. All patients then received i.v. diltiazem in a standard, weight-based dose. A second dose of CaCl(2) pre-treatment or placebo and diltiazem was given if clinically indicated for additional rate control. Both CaCl(2) and placebo pre-treatment groups had equal lowering of heart rate (p < 0.001). There were no adverse events in the calcium pre-treatment study arm. One patient in the placebo group became paradoxically more tachycardic and apneic after the diltiazem infusion. Although i.v. CaCl(2) seems to be equally safe compared to placebo as a pre-treatment in the management of AFF with RVR, we were unable to find a statistically significant blunting of SBP drop with CaCl(2) i.v. pre-treatment. Until further research determines a benefit exists, we cannot recommend i.v. CaCl(2) pre-treatment before diltiazem in the treatment of AFF with RVR.

The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study

OBJECTIVES

We sought to evaluate approaches used to control rate, the effectiveness of rate control, and switches from one drug class to another in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study.

BACKGROUND

The AFFIRM study showed that atrial fibrillation (AF) can be treated effectively with rate control and anticoagulation, but drug efficacy to control rate remains uncertain.

METHODS

Patients (n = 2,027) randomized to rate control in the AFFIRM study were given rate-controlling drugs by their treating physicians. Standardized rate-control efficacy criteria developed a priori included resting heart rate and 6-min walk tests and/or ambulatory electrocardiographic results.

RESULTS

Average follow-up was 3.5 +/- 1.3 years. Initial treatment included a beta-adrenergic blocker (beta-blocker) alone in 24%, a calcium channel blocker alone in 17%, digoxin alone in 16%, a beta-blocker and digoxin in 14%, or a calcium channel blocker and digoxin in 14% of patients. Overall rate control was achieved in 70% of patients given beta-blockers as the first drug (with or without digoxin), 54% with calcium channel blockers (with or without digoxin), and 58% with digoxin alone. Adequate overall rate control was achieved in 58% of patients with the first drug or combination. Multivariate analysis revealed an association between first drug class and several clinical variables. There were more changes to beta-blockers than to the other two-drug classes (p < 0.0001).

CONCLUSIONS

Rate control in AF is possible in the majority of patients with AF. Beta-blockers were the most effective drugs. To achieve the goal of adequate rate control in all patients, frequent medication changes and drug combinations were needed.

Left ventricular performance during acute rate control in atrial fibrillation: the importance of heart rate and agent used

BACKGROUND

The relation between heart rate and left ventricular function during rate control in atrial fibrillation is incompletely understood.

METHODS

Twenty-four patients (age 67 +/- 11 years) with symptomatic recent onset rapid atrial fibrillation and rapid ventricular rate (> 110 bpm) were randomly assigned to receive either intravenous digoxin (13 mcg/kg) or intravenous diltiazem (0.25 mg/kg bolus plus a maintenance infusion). A portable radionuclide detector was used to collect validated measures of relative left ventricular volumes, along with heart rate data, every 15 seconds for 6 hours.

RESULTS

Heart rate decreased significantly at 15 minutes and 180 minutes in the diltiazem group (from 133 +/- 18 bpm to 111 +/- 26 bpm [P <.01] to 94 +/- 24 bpm [P <.001]) but not in the digoxin group (from 129 +/- 18 bpm to 126 +/- 17 bpm [P = NS] to 118 +/- 15 bpm [P = NS]). Left ventricular ejection fraction improved in both groups to a similar extent (from 39 +/- 10% to 50 +/- 8%, [P <.05] after diltiazem, and from 38 +/- 8% to 52 +/- 11% [P <.05] after digoxin at baseline vs 180 minutes, respectively). The ejection fraction vs heart rate slope was steeper in the digoxin group than in the diltiazem group (-0.34 +/- 0.18 vs -0.16 +/- 0.17, P =.048) indicating a more pronounced improvement in ejection fraction per unit decrease in heart rate.

CONCLUSION

In patients with acute atrial fibrillation, digoxin led to similar improvements in ejection fraction compared to diltiazem despite a slower and less potent heart rate slowing.

Ventricular rate control in the elderly: is digoxin enough?

The ventricular response in untreated patients with atrial fibrillation often exceeds 120 beats/min at rest. Digoxin can slow this rate, but its efficacy during exertion may be limited. Alternatives, or additions, to digoxin therapy include the beta blockers and diltiazem or verapamil. This review discusses the role of digoxin in relation to these other drugs, with particular reference to the elderly population.

Atrial fibrillation: beyond irregularly irregular: the basis for acute and chronic treatment

Today atrial fibrillation is the most prevalent sustained arrhythmia encountered in clinical practice; it places a heavy burden on the healthcare system. The purpose of this article is to explore the principles underlying the treatment of both acute and chronic atrial fibrillation.

Protective effect of trimetazidine in a model of ischemia-reperfusion in the rat retina

Trimetazidine is an anti-ischemic agent which is frequently prescribed as a prophylactic treatment of episodes of angina pectoris and as a symptomatic treatment of vertigo and tinnitus. It has also shown beneficial effects in models of visual dysfunction, but the mechanism(s) by which this occurs is as yet undefined. The present study was intended to evaluate the influence of trimetazidine on retinal damage induced by ischemia-reperfusion in a rat model. Retinal ischemia was induced by increasing intraocular pressure to 160 mm Hg for 60 min. Trimetazidine or buffer controls were administered 3 days before the ischemia or in the postischemic period. The degree of retinal damage was assessed after 15 and 30 days of reperfusion after the ischemic insult by histopathologic study according to Hughes' quantification of ischemic damage. Retinal ischemia led to significant reductions in thickness and cell number, mainly in the inner retinal layers. The results from the study demonstrate that treatment with intraperitoneally injected trimetazidine conferred significant protection against retinal ischemic damage. Better results were obtained in the pretreatment group after 15 days of reperfusion. Trimetazidine protects the rat retina from pressure-induced ischemic injury and might be considered a potential therapeutic modality for combating retinal ischemia.

Clinical assessment of clonidine in the treatment of new-onset rapid atrial fibrillation: a prospective, randomized clinical trial

PURPOSE

The role of digoxin and verapamil in the control of ventricular response in rapid atrial fibrillation is well established. This study investigates how clonidine compares with these standard therapies in rate control for new-onset rapid atrial fibrillation. We set out to test the hypothesis that clonidine effectively reduces heart rate in patients with new-onset rapid atrial fibrillation.

SUBJECTS AND METHODS

Forty patients were seen in the emergency department with new-onset (< or =24 hours' duration), stable, rapid atrial fibrillation. Eligible patients were randomized to receive either clonidine, digoxin, or verapamil. Changes in heart rate and blood pressure over 6 hours, as well as frequency of conversion to sinus rhythm were recorded and analyzed.

RESULTS

The mean reduction in heart rate over 6 hours was 44.4 beats/min (95% confidence interval [CI] 28.4-60.4 beats/min) in the clonidine group, 52.1 beats/min (95% CI 40.8-63.4 beats/min) in the digoxin group, and 41.8 beats/min (95% CI 22.5-61.0 beats/min) in the verapamil group. Analysis of variance of the heart rate changes in the 3 groups after 6 hours was not significant (P =.55). At 6 hours, 7 of 12 clonidine patients, 8 of 15 digoxin patients, and 7 of 13 verapamil patients remained in atrial fibrillation (P =.962 on chi(2)).

CONCLUSION

Clonidine controls ventricular rate in new-onset atrial fibrillation with an efficacy comparable to that of standard agents.

Intravenous magnesium sulfate versus diltiazem in paroxysmal atrial fibrillation

BACKGROUND

Drugs currently available for the acute treatment of paroxysmal atrial fibrillation have significant limitations. We assessed the safety and effectiveness of intravenous magnesium sulfate versus diltiazem therapy in patients with prolonged episodes of paroxysmal atrial fibrillation.

METHODS

In a prospective randomized trial, 46 symptomatic patients presenting with paroxysmal atrial fibrillation were given intravenous magnesium sulfate (n=23) or diltiazem (n=23) therapy. Primary outcome measures were effects on ventricular rate control and proportion of patients restored to sinus rhythm at 6 h after initiation of treatment.

RESULTS

There were no differences in baseline characteristics between the two groups. Both forms of treatment were well tolerated, with no adverse clinical events. Both drugs had similar efficacy in reducing the ventricular rate at the first hour of treatment (P<0.05) with a tendency toward a further decrease during infusion times of 2 (P<0.01), 3, 4, 5 and 6 h, respectively (P<0.001). However, at the end of the 6-h treatment period, restoration of sinus rhythm was observed in a significantly higher proportion of patients in the magnesium group compared with the diltiazem group [13 of 23 patients, (57%), versus five of 23 patients, (22%), P=0.03].

CONCLUSIONS

Magnesium sulfate favorably affects rate control and seems to promote the conversion of long lasting episodes of paroxysmal atrial fibrillation to sinus rhythm, representing a safe, reliable and cost-effective alternative treatment strategy to diltiazem.

Electrophysiologic effects of a novel selective adenosine A1 agonist (CVT-510) on atrioventricular nodal conduction in humans

BACKGROUND

CVT-510, N-(3(R)-tetrahydrofuranyl)-6-aminopurine riboside, is a selective A(1)-adenosine receptor agonist with potential potent antiarrhythmic effects in tachycardias involving the atrioventricular (AV) node. This study, the first in humans, was designed to determine the effects of CVT-510 on AV nodal conduction and hemodynamics.

METHODS AND RESULTS

Patients in sinus rhythm with normal AV nodal function at electrophysiologic study (n = 32) received a single intravenous bolus of CVT-510. AH and HV intervals were measured during sinus rhythm and during atrial pacing at 1, 5, 10, 15, 20, 30, 45, and 60 minutes after the bolus. Increasing doses of CVT-510 (0.3 to 10 microg/kg) caused a dose-dependent increase in the AH interval. At 1 minute, a dose of 10 microg/kg increased the AH interval during sinus rhythm from 93 +/- 23 msec to 114 +/- 37 msec, p = 0.01 and from 114 +/- 31 msec to 146 +/- 44 msec during atrial pacing at 600 msec, p = 0.003). The AH interval returned to baseline by 20 minutes. CVT-510 at doses of 0.3 to 10 microg/kg had no effect on sinus rate, HV interval, or systemic blood pressure, and was not associated with serious adverse effects. At doses of 15 and 30 microg/kg, CVT-510 produced transient second/third degree AV heart block in all four patients treated. One of these patients also had a prolonged sedative effect that was reversed with aminophylline.

CONCLUSIONS

CVT-510 promptly prolongs AV nodal conduction and does not affect sinus rate or blood pressure. Selective stimulation of the A(1)-adenosine receptor by CVT-510 may be useful for immediate control of heart rate in atrial fibrillation/flutter and to convert paroxysmal supraventricular tachycardia to sinus rhythm, while avoiding vasodilatation mediated by the A(2)-adenosine receptor, as well as the vasodepressor and negative inotropic effects associated with beta-adrenergic receptor blockade and/or calcium channel blockers.

The use of diltiazem for treating rapid atrial fibrillation in the out-of-hospital setting

STUDY OBJECTIVE

We sought to evaluate the use of intravenous diltiazem for treatment of rapid atrial fibrillation or flutter (RAF) in the out-of-hospital setting.

METHODS

This study is a retrospective review of data with historical control subjects. Data were drawn from out-of-hospital patients reported to a statewide paramedic system who presented with atrial fibrillation or flutter and a ventricular response rate (VRR) of 150 beats/min or greater. The intervention (diltiazem) group included patients who received diltiazem during a 9-month period in 1999. The control group included patients from 1998 who did not receive diltiazem. Patients who were intubated or underwent cardioversion were omitted. Therapeutic response was defined as the occurrence of change to sinus rhythm, reduction of VRR to 100 beats/min or less, or reduction of baseline VRR by 20% or greater. Data were analyzed by using the chi(2) test, the Student's t test, and odds ratios (ORs). A Bonferroni adjusted P value of.005 was used to define statistical significance.

RESULTS

Forty-three patients receiving diltiazem and 27 control subjects were included in the study. The mean total diltiazem dose was 19.8 mg (95% confidence interval 17.8 to 21.8). The diltiazem and control groups did not significantly differ with respect to age; sex; history of atrial fibrillation; prior use of digitalis, beta-blockers, or calcium channel blockers; concurrent out-of-hospital therapies; or baseline VRR or systolic blood pressure (P =.09 to 1.00). The difference in VRR reduction between the diltiazem and control groups was 38 beats/min (95% confidence interval 24 to 52); this difference was statistically significant (P <.001). The mean percentage reduction of VRR in the diltiazem group was -33.1%. The difference in systolic blood pressure change between the diltiazem and control groups was not statistically significant (P =.17). The diltiazem group had a higher prevalence of achieving VRR reduction to 100 beats/min or less than did the control group (OR 22.6; P <.001), of achieving a VRR reduction of 20% or greater (OR 19.3; P <.001), and of achieving overall therapeutic response (OR 19.3; P <.001). Few changed to sinus rhythm in either group (estimated OR 6.3; P =.15). No patients in the diltiazem group required treatment for hypotension, endotracheal intubation, resuscitation from cardiac arrest, or emergency treatment of unstable dysrhythmias.

CONCLUSION

The effects of diltiazem on RAF can be appreciated within the constraints of the out-of-hospital environment. Diltiazem should be considered as a viable field therapy for rate control of RAF.

Continuous intravenous diltiazem infusion for short-term ventricular rate control in children

Intravenous diltiazem was administered to 10 pediatric patients with primary atrial tachyarrhythmias with rapid ventricular response. Rapid, consistent, and safe temporary ventricular rate control was obtained in all patients given this medication.

The Management of Atrial Fibrillation in the ICU

Atrial tachyarrhythmias are the most frequent arrhythmias occurring in ICU patients, being particularly common in patients with cardiovascular and respiratory failure. Unlike ambulatory patients in whom atrial fibrillation/flutter (AF) is likely to be short lived, in the critically ill these arrhythmias are unlikely to resolve until the underlying disease process has improved. Urgent cardioversion is indicated for hemodynamic instability. Treatment in hemodynamically stable patients includes correction of treatable precipitating factors, control of the ventricular response rate, conversion to sinus rhythm, and prophylaxis against thromboembolic events in those patients who remain in AF. Diltiazem is the preferred agent for rate control, while procainamide and amiodarone are generally considered to be the antiarrhythmic agents of choice.

Rapid reversal of life-threatening diltiazem-induced tetany with calcium chloride

We describe a patient who developed tetany with sudden respiratory arrest after the infusion of intravenous diltiazem. The administration of calcium chloride rapidly resolved the patient's tetany with prompt recovery of respiratory function, averting the need for more aggressive airway management and ventilatory support. The emergency physician should be aware that life-threatening tetany may accompany the administration of intravenous diltiazem and that calcium chloride may be a rapid and effective remedy.

A randomized, double-blind comparison of intravenous diltiazem and digoxin for atrial fibrillation after coronary artery bypass surgery

BACKGROUND

Atrial fibrillation (AF) after coronary bypass graft surgery may result in hypotension, heart failure symptoms, embolic complications, and prolongation in length of hospital stay (LOHS). The purpose of this study was to determine whether intravenous diltiazem is more effective than digoxin for ventricular rate control in AF after coronary artery bypass graft surgery. A secondary end point was to determine whether ventricular rate control with diltiazem reduces postoperative LOHS compared with digoxin.

METHODS AND RESULTS

Patients with AF and ventricular rate > 100 beats/min within 7 days after coronary artery bypass graft surgery were randomly assigned to receive intravenous therapy with diltiazem (n = 20) or digoxin (n = 20). Efficacy was measured with ambulatory electrocardiography (Holter monitoring). Safety was assessed by clinical monitoring and electrocardiographic recording. LOHS was measured from the day of surgery. Data were analyzed with the intention-to-treat principle in all randomly assigned patients. In addition, a separate intention-to-treat analysis was performed excluding patients who spontaneously converted to sinus rhythm. In the analysis of all randomly assigned patients, those who received diltiazem achieved ventricular rate control (> or = 20% decrease in pretreatment ventricular rate) in a mean of 10 +/- 20 (median 2) minutes compared with 352 +/- 312 (median 228) minutes for patients who received digoxin (p < 0.0001). At 2 hours, the proportion of patients who achieved rate control was significantly higher in patients treated with diltiazem (75% vs 35%, p = 0.03). Similarly, at 6 hours, the response rate associated with diltiazem was higher than that in the digoxin group (85% vs 45%, p = 0.02). However, response rates associated with diltiazem and digoxin at 12 and 24 hours were not significantly different. At 24 hours, conversion to sinus rhythm had occurred in 11 of 20 (55%) patients receiving diltiazem and 13 of 20 (65%) patients receiving digoxin (p = 0.75). Results of the analysis of only those patients who remained in AF were similar to those presented above. There was no difference between the diltiazem-treated and digoxin-treated groups in postoperative LOHS (8.6 +/- 2.2 vs 7.7 +/- 2.0 days, respectively, p = 0.43).

CONCLUSIONS

Ventricular rate control occurs more rapidly with intravenous diltiazem than digoxin in AF after coronary artery bypass graft surgery. However, 12- and 24-hour response rates and duration of postoperative hospital stay associated with the two drugs are similar.

The medical management of atrial fibrillation

Atrial fibrillation is an extremely common arrhythmia that is associated with significant sequelae. Certain aspects of therapy, such as anticoagulation, are studied in well-constructed randomized trials. Other therapy, such as the maintenance of sinus rhythm with antiarrhythmic agents, is supported by limited evidence. This article reviews the epidemiology and medical treatment of this arrhythmia, addressing anticoagulation, ventricular rate control, and restoration and maintenance of sinus rhythm. Randomized trials in progress that attempt to answer important questions in the management of atrial fibrillation are also discussed.

Dilemmas in the acute pharmacologic treatment of uncontrolled atrial fibrillation

A recently conducted observational study of the prehospital treatment of uncontrolled atrial fibrillation brought to light therapeutic inconsistencies by emergency providers in dealing with this dysrhythmia. A review of the literature suggests that digoxin lacks efficacy in controlling ventricular rate in atrial fibrillation and that the slow onset of digoxin makes its use in the emergency setting questionable. Because of their demonstrated ability to rapidly slow ventricular rate, the calcium channel blocker, diltiazem, or the beta-adrenergic blocker, esmolol, should be the preferred agents for treating rapid atrial fibrillation in the emergency department or the paramedic ambulance.

Control of heart rate during transition from intravenous to oral diltiazem in atrial fibrillation or flutter

We tested whether patients presenting with atrial fibrillation (AF) or flutter (AFl) with a rapid ventricular response could maintain control of heart rate while transferring from a bolus and continuous infusion of intravenous diltiazem to oral diltiazem. Forty patients with AF or AFI and sustained ventricular rate > or = 120 beats/min received intravenous diltiazem "bolus" (20 to 25 mg for 2 minutes) and "infusion" (5 to 15 mg/hour for 6 to 20 hours). Oral long-acting diltiazem (diltiazem CD 180, 300, or 360 mg/24 hours) was administered in patients in whom stable heart rate control was attained during constant infusion. Intravenous diltiazem infusion was discontinued 4 hours after the first oral dose, and patients were monitored during 48 subsequent hours of "transition" to oral therapy. Response to diltiazem was defined as heart rate <100 beats/min, > or = 20% decrease in heart rate from baseline, or conversion to sinus rhythm. Other rate control or antiarrhythmic medications were not allowed during the study period. Thirty-seven of 40 patients maintained heart rate control during the bolus, and 35 of the remaining 37 maintained control during the infusion of intravenous diltiazem. Of the 35 patients achieving heart rate control with intravenous diltiazem who entered the transition to oral therapy, 27 maintained heart rate control (response rate of 77%/, 95% confidence interval 63% to 91%). The median infusion rate of intravenous diltiazem was 10 mg/hour, and the median dose of oral diltiazem CD was 300 mg/day. Oral long-acting diltiazem was 77% effective in controlling ventricular response over 48 hours in patients with AF or AFl in whom ventricular response was initially controlled with intravenous diltiazem.