Multifocal atrial tachycardia: a toxic effect of theophylline

HRAS-Mutant Cardiomyocyte Model of Multifocal Atrial Tachycardia

BACKGROUND

Germline HRAS gain-of-function pathogenic variants cause Costello syndrome (CS). During early childhood, 50% of patients develop multifocal atrial tachycardia, a treatment-resistant tachyarrhythmia of unknown pathogenesis. This study investigated how overactive HRAS activity triggers arrhythmogenesis in atrial-like cardiomyocytes (ACMs) derived from human-induced pluripotent stem cells bearing CS-associated HRAS variants.

METHODS

HRAS Gly12 mutations were introduced into a human-induced pluripotent stem cells-ACM reporter line. Human-induced pluripotent stem cells were generated from patients with CS exhibiting tachyarrhythmia. Calcium transients and action potentials were assessed in induced pluripotent stem cell-derived ACMs. Automated patch clamping assessed funny currents. HCN inhibitors targeted pacemaker-like activity in mutant ACMs. Transcriptomic data were analyzed via differential gene expression and gene ontology. Immunoblotting evaluated protein expression associated with calcium handling and pacemaker-nodal expression.

RESULTS

ACMs harboring HRAS variants displayed higher beating rates compared with healthy controls. The hyperpolarization activated cyclic nucleotide gated potassium channel inhibitor ivabradine and the Nav1.5 blocker flecainide significantly decreased beating rates in mutant ACMs, whereas voltage-gated calcium channel 1.2 blocker verapamil attenuated their irregularity. Electrophysiological assessment revealed an increased number of pacemaker-like cells with elevated funny current densities among mutant ACMs. Mutant ACMs demonstrated elevated gene expression (ie, ISL1, TBX3, TBX18) related to intracellular calcium homeostasis, heart rate, RAS signaling, and induction of pacemaker-nodal-like transcriptional programming. Immunoblotting confirmed increased protein levels for genes of interest and suppressed MAPK (mitogen-activated protein kinase) activity in mutant ACMs.

CONCLUSIONS

CS-associated gain-of-function HRASG12 mutations in induced pluripotent stem cells-derived ACMs trigger transcriptional changes associated with enhanced automaticity and arrhythmic activity consistent with multifocal atrial tachycardia. This is the first human-induced pluripotent stem cell model establishing the mechanistic basis for multifocal atrial tachycardia in CS.

Comparative monitoring of oral theophylline treatment in blood serum, saliva, and nasal mucus

BACKGROUND

Theophylline, used in the treatment for various pulmonary pathologies, is usually given orally with drug levels measured primarily in blood serum and occasionally in saliva. Although theophylline treatment is now not commonly used it has been effective to correct smell loss (hyposmia). This is important because 21 million people in the United States exhibit hyposmia and oral theophylline has corrected hyposmia in about 50% of these patients. This result suggests that oral theophylline may result in the drug not only appearing in the serum but also in nasal mucus, thereby playing a role in correcting hyposmia. No prior report of theophylline in nasal mucus has been made and no comparison of levels in nasal mucus, blood serum, or saliva has been previously reported.

PURPOSE

The aim was to determine, after oral theophylline treatment, if it is present in nasal mucus and, if present, to compare the levels with those in serum and saliva.

METHODS

Oral theophylline was given to 23 hyposmic patients at daily doses of 200, 300, 400, 600, and 800 mg for periods of 2-10 months. During each period, blood serum, saliva, and nasal mucus were collected and theophylline measured in each fluid.

RESULTS

Theophylline was found in nasal mucus and in saliva and blood serum at each drug dose in each patient to whom it was given. The mean level of theophylline in nasal mucus was 74% that of serum; mean level in saliva was 67% of serum; mean level in nasal mucus was 111% that in saliva.

CONCLUSIONS

Theophylline is present in nasal mucus after oral administration. Levels in nasal mucus reflect blood and saliva levels in a consistent manner and offer a simple convenient noninvasive method to monitor theophylline doses of the oral drug.

Development of multifocal atrial tachycardia in a patient using aminophylline -A case report-

An 82-year-old female, with left femoral neck fracture was scheduled for left hip hemiarthroplasty, under spinal anaesthesia. She had been suffering from diabetes, hypertension, lung cancer and was previously treated with IV aminophylline for respiratory insufficiency. She was given spinal anaesthesia with 10 mg of 0.5% hyperbaric bupivacaine, and T6 sensory block level was established. After 10 minutes, her blood pressure dropped to 80/60 mmHg, so intravenous ephedrine was given. At that moment, multifocal atrial tachycardia (MAT) appeared on electrocardiogram (ECG). Intravenous infusion of phenylephrine and procainamide was given and conversion of MAT to sinus rhythm was successfully achieved. We report a case of MAT after spinal anaesthesia, in a patient with respiratory insufficiency previously treated with IV aminophylline, which was successfully treated by intravenous infusion of phenylephrine and procainamide.

Use of theophylline in chronic obstructive pulmonary disease: examining the evidence

PURPOSE OF REVIEW

The role of theophylline in the management of chronic obstructive pulmonary disease remains controversial. This review was undertaken to determine the efficacy of theophylline in patients with stable disease.

RECENT FINDINGS

Twenty-two good quality randomized controlled trials were included in this systematic review. The review showed that theophylline significantly improved forced expiratory volume in 1 s and forced vital capacity (weighted mean difference 0.10 L; 95% confidence interval 0.04-0.16 and weighted mean difference 0.21 L; 95% confidence interval 0.10-0.31, respectively). V also improved with theophylline (weighted mean difference 195.27 mL/min; 95% confidence interval 112.71-277.83), as did Pa and Pa (weighted mean difference 1.45 mmHg; 95% confidence interval 0.26-2.65 and weighted mean difference -1.09 mmHg; 95% confidence interval -1.83 to -0.35, respectively). Patients preferred theophylline over placebo (relative risk 2.27; 95% confidence interval 1.26-4.11). Theophylline increased the risk of nausea, however, compared with placebo (relative risk 7.67; 95% confidence interval 1.47-39.94).

SUMMARY

This review has shown that oral theophylline plays an important role in the management of patients with stable chronic obstructive pulmonary disease by improving lung function, arterial blood gas tensions and ventilatory capacity. Patients also preferred treatment with theophylline when compared with placebo. The benefits of theophylline in stable chronic obstructive pulmonary disease, however, have to be weighed against the risk of adverse effects, particularly nausea.

The use of bronchodilators in the treatment of airway obstruction in elderly patients

Ageing is associated with important anatomical, physiological and psychosocial changes that may have an impact on the management of obstructive airway diseases (asthma and chronic obstructive pulmonary disease (COPD)) and on their optimal therapy. Ageing-related modifications might be responsible for a different effectiveness of bronchodilators in the elderly patients as compared to younger subjects. Furthermore, the physiological involution of organs and the frequent comorbidity, often interfere with pharmacokinetics of bronchodilator drugs used in asthma and COPD. This review will focus on the use of bronchodilators in the elderly, with particular attention to the achievable goals and to rationale, utility and pitfalls in using the inhalation therapy in this age group. beta(2)-agonists, anticholinergics and methylxanthines will be discussed and their side effects in the elderly will be considered.

Efficacy of theophylline in people with stable chronic obstructive pulmonary disease: a systematic review and meta-analysis

OBJECTIVES

To determine the efficacy of oral theophylline compared with placebo in people with stable chronic obstructive pulmonary disease (COPD).

METHODS

Systematic review of randomized-controlled trials comparing oral theophylline with placebo for a minimum of 7 days in people with stable COPD.

RESULTS

Twenty randomized-controlled trials were included in this review. The following outcomes showed significant improvement with theophylline compared with placebo: FEV1 and FVC both improved with theophylline (weighted mean difference [WMD] 0.10 L; 95% confidence interval [95% CI] 0.04-0.16 and WMD 0.21 L; 95% CI 0.10-0.32, respectively). VO2 max also improved with theophylline (WMD 195.27mL/ min; 95% CI 112.71-277.83), as did PaO2 and PaCO2 (WMD 3.18 mmHg; 95% CI 1.23-5.13 and WMD -2.36mmHg; 95% CI -3.52 to -1.21, respectively). Patients preferred theophylline over placebo (relative risk 2.27; 95% CI 1.26-4.11). Theophylline increased the risk of nausea compared with placebo (RR 7.67; 95% CI 1.47-39.94).

CONCLUSION

This review has shown that theophylline still has a role in the management of stable COPD, and is preferred by patients over placebo. However, the benefits of theophylline in stable COPD have to be weighed against the risk of adverse effects.

Oral theophylline for chronic obstructive pulmonary disease

BACKGROUND

Oral theophylline has, for many years, been used as a bronchodilator in patients with COPD. Despite the introduction of new drugs, and its narrow therapeutic index, theophylline is still recommended for COPD treatment.

OBJECTIVES

To determine the effectiveness of oral theophylline when compared to placebo in patients with stable COPD.

SEARCH STRATEGY

The Cochrane Airways Review Group and Cochrane Controlled Clinical Registers were searched.

SELECTION CRITERIA

All studies were randomised controlled trials (RCTs).

DATA COLLECTION AND ANALYSIS

Data were independently abstracted and the methodological quality assessed by two reviewers.

MAIN RESULTS

Twenty RCTs met the inclusion criteria. Concomitant therapy varied from none to any other bronchodilator plus corticosteroid (oral and inhaled). The following outcomes were significantly different when compared to placebo. FEV1 improved with treatment: Weighted Mean Difference (WMD) 100 ml; 95% Confidence Interval (95%CI) 40, 160 ml. Similarly for FVC: WMD 210 ml 95%CI 100, 320. Two studies reported an improvement in VO2max; WMD 195 ml/min, 95%CI 113,27). At rest, PaO2 and PaCO2 both improved with treatment (WMD 3.2 mmHg; 95%CI = 1.2, 5., and WMD -2.4 mmHg; 95%CI = -3.5, -1.2, respectively). Walking distance tests did not improve (4 studies, Standardised Mean Difference 0.30, 95%CI -0.01, 0.62), neither did Visual Analogue Score for breathlessness isn two small studies (WMD 3.6, 95%CI -4.6, 11.8). The Relative Risk (RR) of nausea was greater with theophylline (RR 7.7; 95%CI 1.5, 39.9). However, patients' preference for theophylline was greater than that for placebo (RR 2.27; 95%CI = 1.26, 4.11). Very few patient withdrew from these studies for any reason.

REVIEWER'S CONCLUSIONS

Theophylline has a modest effect on FEV1 and FVC and slightly improves arterial blood gas tensions in moderate to severe COPD. These benefits were seen in patients receiving a variety of different concomitant therapies. Improvement in exercise performance depended on the method of testing. There was a very low dropout rate in the studies that could be included in this review, which suggests that recruited patients may have been known by the investigators to be theophylline tolerant. This may limit the generalisability of these studies.

Radiofrequency catheter modification of atrioventricular junction in patients with COPD and medically refractory multifocal atrial tachycardia

BACKGROUND

Multifocal atrial tachycardia (MAT) is a difficult clinical problem generally associated with acute cardiorespiratory illness. The purpose of this study was to assess the feasibility and clinical usefulness of atrioventricular (AV) junction modification as a nonpharmacologic therapy for medically refractory MAT.

METHODS AND RESULTS

Thirteen patients with COPD and medically refractory MAT underwent AV junction modification. Complications and outcome of this procedure were monitored. Subjective perceptions of quality of life assessed by a semiquantitative questionnaire and cardiac performance study were obtained before ablation (baseline) and 1 and 6 months after ablation. Radiofrequency energy was applied until the average ventricular rate fell to < 100 beats/min. Ablation procedures controlled the ventricular response in 11 of 13 patients (84%). One patient had unsuccessful modification. Another patient developed delayed complete AV block on the second day after ablation. In these 13 patients, average ventricular rate was reduced from a mean of 145 +/- 11 to 89 +/- 22 beats/min immediately after the ablation (p < 0.01). One patient had recurrent symptomatic MAT at 1 month after ablation; this patient underwent a second procedure without late recurrence. All patients were followed up for at least 6 months (mean, 11 +/- 5 months; range, 6 to 18 months). General quality of life and frequency of significant symptoms improved significantly in patients with successful modification at 1 and 6 months. The left ventricular ejection fraction increased significantly after ablation (44.5 +/- 7.3% at baseline, 49.4 +/- 4. 2% at 1 month, and 50.0 +/- 4.9% at 6 months; all p < 0.05). However, right ventricular ejection fraction remained unchanged (34.7 +/- 6. 2% at baseline, 35.7 +/- 4.4% at 1 month, and 34.3 +/- 4.6% at 6 months; all p > 0.05). The consumption of health-care resources (including frequency of hospital admission and emergency department attendance, antiarrhythmic drug trials) decreased significantly 6 months after AV junction modification. Pulmonary function and theophylline level remained unchanged during follow-up.

CONCLUSIONS

AV junction modification offers an effective therapy for controlling ventricular rate in medically refractory MAT. This procedure improves the quality of life and left ventricular function in selected patients with symptomatic and medically refractory MAT.

Multifocal atrial tachycardia

Multifocal atrial tachycardia is typically seen in elderly patients with severe illnesses, most commonly COPD. The mechanism of the arrhythmia may be delayed afterdepolarizations leading to triggered activity, but this has not been firmly established. The initial treatment of multifocal atrial tachycardia should include supportive measures and aggressive reversal of precipitating causes. Since multifocal atrial tachycardia is commonly a secondary phenomenon, the role for antiarrhythmic therapy is unclear. Metoprolol, magnesium, and verapamil have been evaluated in a few treatment studies, and may have a role in the treatment of multifocal atrial tachycardia.

Association between Helicobacter pylori infection and serum pepsinogen concentrations in gastroduodenal disease

AIM

To investigate the association between Helicobacter pylori infection and serum pepsinogen (PG) 1 and 2 concentrations in various gastroduodenal diseases.

METHODS

Serum PG1 and 2 concentrations and antibodies to H pylori were measured by enzyme linked immunosorbent assay (ELISA); gastric mucosal pH was assessed and urease activity in biopsy tissue was determined. A comparison of the ELISA and urease test results permitted division of the cases into positive, false positive, false negative and negative categories for control, gastritis, and ulcer groups.

RESULTS

The gastric mucosal pH and serum PG2 in cases positive for H pylori were significantly increased in ulcer and gastritis cases compared with H pylori negative cases. Similar tendencies were observed for the false positive and false negative categories.

CONCLUSIONS

A positive ELISA reaction for antibodies and an increased serum PG2 concentration are reliable indicators of H pylori infection.

The clinical implication of theophylline intoxication in the Emergency Department

We reviewed the clinical manifestations of 53 episodes of theophylline intoxication in 50 patients over a one year study period, in order to identify the specific features as they presented to the Emergency Department (ED). There was a trend to an increase in the serum theophylline concentration with increased severity of clinical features, but the difference between the mild and the moderate cases was not statistically significant. The most common symptoms and signs were gastrointestinal complaints, sinus tachycardia, and atrial arrhythmias. Mixed atrial and ventricular arrhythmias, which are rarely mentioned as a specific feature of theophylline intoxication, were found in 16% of our patients and accounted for 29% of the cardiovascular manifestations. Four patients developed rhabdomyolysis, which presumably was secondary to a seizure or profound hypokalaemia. Cases of theophylline intoxication presenting to the ED had higher serum concentrations of theophylline and tended to have more severe toxicity than those patients in the non-ED group. Delayed diagnosis may contribute to the severity of the outcome, since severe cases in the ED were usually suspected to have developed intoxication at some point later in the stay in the ED than at the time of presentation, or after admission to the hospital, thus permitting the occurrence of an additional iatrogenic component to the intoxication. They also complained of symptoms not associated with the theophylline toxicity, which may have diverted the physician's attention from recognizing this concurrent problem.(ABSTRACT TRUNCATED AT 250 WORDS)

Recognition and treatment of multifocal atrial tachycardia: a critical review

Multifocal atrial tachycardia (MAT) is an uncommon but clinically important tachydysrhythmia that is usually seen in the setting of severe cardiopulmonary illness. Diagnostic criteria include the presence of at least three different, nonsinus P waves in the same lead; an atrial rate greater than 100 beats per minute; and an isoelectric baseline between P waves. MAT is often difficult to differentiate from atrial fibrillation. The pathogenesis of MAT is unknown; however, it is probably incited by "triggered" electrical activity, a form of abnormal automaticity. This electrophysiologic model has led to several small, uncontrolled clinical trials using calcium channel and beta-adrenergic blocking agents, specifically verapamil and metropolol. None of these trials meets rigorous methodologic standards, and all exclude unstable patients who are at greatest risk for hemodynamic compromise from the tachycardia. Treatment of MAT should first be directed at potential predisposing factors, such as hypoxia, congestive heart failure, and theophylline toxicity. Pharmacologic treatment includes intravenous metoprolol or verapamil; in published reports both agents have been well tolerated and have controlled the heart rate in a majority of patients.

Metabolic correlates of theophylline therapy: a concentration-related phenomenon

OBJECTIVE

To determine the relationship of serum theophylline concentration with electrolyte and glucose abnormalities across a broad range of theophylline concentrations.

DESIGN

Retrospective review of a computerized laboratory database between June 1, 1984 and June 1, 1986.

SETTING

A midwestern university medical center.

PATIENTS

Eight hundred sixty-nine patients with serum theophylline concentrations of > 5.5 mumol/L and a random unmatched sample (control group) of 350 in- and outpatient adults and children with no history of reactive airways disease or theophylline exposure.

RESULTS

Patients with measurable theophylline had a higher risk of hypokalemia, hyponatremia, hyperglycemia, hypophosphatemia, and hypomagnesemia compared with the unexposed control group. Unadjusted odds ratios (OR) were: (1) hypokalemia OR = 4.2 (95 percent CI 2.2 to 7.9); (2) hyponatremia OR = 5.4 (95 percent CI 2.0 to 12.9); (3) hypomagnesemia OR = 1.6 (95 percent CI 1.0 to 2.5); (4) hyperglycemia OR = 2.3 (95 percent CI 1.7 to 3.0); and (5) hypophosphatemia OR = 2.7 (95 percent CI 1.2 to 5.3). A linear concentration-response relationship was documented between serum theophylline concentration and all metabolic disturbances.

CONCLUSIONS

Measurable theophylline was associated with increased risk for glucose and electrolyte abnormalities in a concentration-related fashion across a broad range of theophylline concentrations from 5.5 to > or = 110 mumol/L.

Aminophylline induced atrial fibrillation

Atrial fibrillation (AF) with a rapid ventricular response was induced by intravenous (i.v.) aminophylline during treatment for symptomatic pulmonary disease in three patients who had no evidence of underlying heart disease or previous cardiac arrhythmia. Serum theophylline concentration was therapeutic in two patients and toxic in the third. Previous reports of AF related to aminophylline have underscored its association with toxic serum theophylline concentration. Conversion to sinus rhythm occurred at a time interval (9-14 hours) appropriate to the serum decay of aminophylline, after its cessation. A shortened atrial refractory period and dispersed recovery of excitability consequent to aminophylline may engender multiple reentrant circuits and lead to AF. i.v. diltiazem was more effective than digoxin in the ventricular rate control of AF prior to conversion to sinus rhythm.

The rational pharmacology of digoxin

Although digoxin remains one of the most widely prescribed drugs in the United States, potential pharmacodynamic and pharmacokinetic interactions between this compound and other drugs, diseases, and events commonly encountered in the perioperative period remain largely unappreciated. Furthermore, the therapeutic benefit of discontinuing or initiating digoxin treatment preoperatively remains unclear. We present a basic review of current knowledge regarding digoxin pharmacology and examine those concepts from the perspective of clinical anesthesiologists.

Cardiac evaluation

Over the past decade there has been a dramatic, rapid development of new imaging modalities used in the evaluation of the cardiac patient. These newer techniques are frequently complex and specialized in their application and interpretation. Nonetheless, the prevalence of cardiac disease in the United States, and the wide application of these diagnostic tests, mandate that the well-rounded clinician has a basic understanding of the utility of these diagnostic modalities. Unfortunately, the burgeoning field of cardiac imaging seems at times to overshadow our most important basic diagnostic tools, namely, the history, physical exam, chest radiograph, and electrocardiogram (ECG). This review will attempt to impart a basic understanding of the newer cardiac diagnostic tests and their utility in various disease states. Emphasis on the importance of the basic clinical exam and the precise integration of specific diagnostic tests into the cardiac evaluation will be emphasized. The article will deliver a basic review of exercise treadmill testing, echocardiography, radionuclide imaging techniques, magnetic resonance imaging, and cardiac catheterization. It is hoped that this review will impart to the noncardiologist clinician a basic understanding of the cardiovascular diagnostic techniques so that an accurate, precise, cost-effective, efficient diagnostic plan for the patient with cardiovascular disease can be developed and applied.

Prehospital recognition of multifocal atrial tachycardia: association with acute myocardial infarction

Patients with chronic obstructive pulmonary disease and acute decompensation commonly present with an irregularly irregular supraventricular tachycardia that is, in fact, multifocal atrial tachycardia, but frequently misdiagnosed as atrial fibrillation. To heighten awareness of this arrhythmia, its clinical and electrocardiographic presentations, and its potential therapeutic implications, two patients are reported who presented with multifocal atrial tachycardia during prehospital care. In these two patients the clinical substrate was not chronic obstructive pulmonary disease but instead acute myocardial infarction. By means of a high index of clinical suspicion and close scrutiny of an electrocardiogram, a diagnosis of multifocal atrial tachycardia can be established during prehospital management, and potentially ineffective therapeutic interventions can be avoided, both during prehospital care and in the emergency department.

Electrophysiologic Study of the Effects of Aminophylline and Metaproterenol on Canine Myocardium

Aminophylline and beta-adrenergic agonists are widely used in the treatment of obstructive lung diseases. It has been suggested that combined aminophylline and beta-agonist therapy may promote the development of atrial and ventricular arrhythmias. The effects of these agents in combination on myocardial conduction and tissue refractoriness have not been documented. We evaluated the electrophysiologic effects of intravenous aminophylline and inhaled metaproterenol on canine myocardium. Aminophylline produced significant decreases from baseline in the AH interval (85 +/- 6.5 [SD] to 63 +/- 4.1 ms [p less than 0.02]), Wenckebach cycle length (WCL) (226 +/- 8.7 to 182 +/- 5.8 ms [p less than 0.02]), and ventricular effective refractory period (VERP) (166 +/- 6.0 to 148 +/- 4.9 ms [p less than 0.01]). Metaproterenol produced similar results, except metaproterenol significantly decreased the atrial effective refractory period (AERP) from 152 +/- 6.6 to 130 +/- 3.2 ms (p less than 0.02), an effect not seen with aminophylline alone. Metaproterenol also produced significantly greater reductions in AH interval and WCL, as well as a greater increase in heart rate than aminophylline did. When compared with aminophylline alone, combined metaproterenol and aminophylline therapy produced significantly greater reductions in the AH interval (63 +/- 4.1 versus 48 +/- 1.2 ms for combined therapy [p less than 0.01]), HV interval (32 +/- 1.2 versus 28 +/- 2.0 ms for combined therapy [p less than 0.02]), WCL (182 +/- 5.8 versus 150 +/- 7.1 ms for combined therapy [p less than 0.02]), and VERP (148 +/- 4.9 versus 132 +/- 2.0 ms for combined therapy [p less than 0.02]). We conclude that both aminophylline and metaproterenol significantly enhance AV nodal and His-Purkinje conduction. Metaproterenol produced significant changes in both atrial and ventricular tissue refractoriness. Metaproterenol produced significantly greater changes than aminophylline alone, and inhaled metaproterenol combined with intravenous aminophylline produced greater changes in AV nodal and His-Purkinje conduction and ventricular refractoriness than did aminophylline alone in a canine model.

The bronchodilator terbutaline enhances digitalis-induced arrhythmia

The hypothesis that beta 2-sympathomimetics augment digitalis-induced arrhythmias and antagonize its positive inotropic action was tested in isolated, electrically driven guinea-pig left atria. Alone, 0.3 mM terbutaline enhanced myocardial force generation but did not induce dysrhythmia. Terbutaline shortened the time to the onset of 3 microM ouabain-induced arrhythmia by approximately 75% from 19.7 +/- 3.2 minutes to 5.7 +/- 1.2 minutes (p less than 0.005). The enhancement of arrhythmias appeared to be the result of triggering ouabain-induced delayed afterdepolarizations (DAD) into overt arrhythmia. The effect of terbutaline was antagonized by blocking cardiac beta-adrenoceptors with propranolol. Terbutaline did not affect the ability of ouabain to increase myocardial contractility.

The arrhythmogenicity of theophylline. A multivariate analysis of clinical determinants

OBJECTIVE

to determine the relation of serum theophylline concentrations (STC) to the occurrence of cardiac arrhythmias in a population of hospitalized patients.

STUDY DESIGN

A cross-sectional study of 100 patients receiving theophylline who had electrocardiograms at the time STC had been obtained. Categorization was based on STC without knowledge of clinical status: group 1 (25) had STC less than 2.5 mg/L; group 2 (25), STC greater than or equal to 2.5 less than 10 (6.2 +/- 0.4) mg/L; group 3 (25), STC greater than or equal to 10 less than or equal to 20 (15.8 +/- 0.4) mg/L; and group 4 (25), STC greater than 20 (27.8 +/- 1.1) mg/L.

SETTING

A university-affiliated teaching hospital.

RESULTS

Two-thirds of the patients were receiving theophylline in an oral form, with a similar distribution found in all groups. Groups were not different with respect to age, clinical diagnoses, electrocardiographic patterns, arterial pH or gases, serum calcium, or treatment with beta-agonists. Although fewer patients in group 1 were receiving steroids than those in the other groups, and serum potassium was lower in group 3 than in group 1 (4.0 +/- 0.6 vs 4.5 +/- 0.5 mEq/L, p less than 0.05), on multivariate analysis, serum potassium was not an independent predictor of arrhythmia, and treatment with steroids or digoxin was, at most, only weakly associated with the presence of arrhythmia. Heart rate was directly related to STC (r = 0.64, p less than 0.01), and STC was the strongest independent predictor of arrhythmia in this population. Although only 20 percent of patients in group 1 or 2 had arrhythmias, 48 percent of group 3 (p less than 0.05) and 56 percent of group 4 (p less than 0.05) had this finding. Moreover, the odds ratio of group 3 having an arrhythmia compared with group 1 was 3.7, 1.5 to 11.7, p less than 0.01. Multifocal atrial tachycardia was found in 8 percent of the patients in group 3 and 16 percent in group 4 but in none of the patients in groups 1 or 2. Two patients with multifocal atrial tachycardia died suddenly within 24 hours of having their STC measurement; none had concomitant ventricular ectopy.

CONCLUSION

Theophylline causes tachycardia and serious arrhythmias even at STC considered to be therapeutic. Multifocal atrial tachycardia, an arrhythmia associated with use of this drug, may herald sudden cardiac death.

Cardiac arrhythmias during theophylline toxicity. A prospective continuous electrocardiographic study

To examine the effects of theophylline toxicity on cardiac rhythm, patients underwent continuous ambulatory ECG recording during acute theophylline toxicity and recovery. The patients, who were recruited form inpatient wards, intensive care units, and emergency departments of a University Medical Center and a Veterans Administration Medical Center, had serum theophylline concentrations (STC) greater than 30 mg/L. There were 14 men and two women with a mean age of 66 years. Fourteen patients had COPD and developed toxicity following long-term theophylline overmedication. Two patients had asthma and ingested an intentional overdose. The STC at the onset of ECG recording ranged from 23 to 67 mg/L. The principal rhythm was sinus in 15 patients; one patient had atrial fibrillation. Sinus tachycardia (heart rate greater than 100/min) was common, and heart rate fell in proportion to STC as toxicity resolved. Supraventricular ectopic beats (SVEs) were noted in seven patients with multiple runs of SVE being present in four. One patient developed multifocal atrial tachycardia (MAT) during toxicity that resolved spontaneously. During the 11 +/- 8 hours of recording during toxicity (STC greater than 20 mg/L), 80 percent of patients had ventricular premature beats (VPBs), 44 percent had paired VPBs, and 25 percent had ventricular runs. One elderly patient with heart disease developed sustained ventricular tachycardia (VT) when STC = 66 mg/L. No other patient had ventricular ectopy that required intervention. During the 10 +/- 6 hours of recording during the "recovery phase" (STC less than 20 mg/L), all patients with VPBs continued to have ectopy; however, the number of VPBs declined significantly. A follow-up 24-hour ECG recording obtained one week after recovery from toxicity in the patient with sustained VT demonstrated marked reduction in the frequency and complexity of VPBs. Patients with frequent (greater than 10/h) or repetitive VPBs were older (p less than 0.05) than those without complex ectopy. There was a trend (p = 0.07) suggesting patients with underlying heart disease were at risk for having complex ventricular ectopy. We conclude that sinus tachycardia, SVE, and VPBs are common among patients with theophylline toxicity; however, sustained ventricular or supraventricular tachyarrhythmias that require antiarrhythmic therapy are uncommon.

Risk of toxicity in patients with elevated theophylline levels

Toxic side effects of elevated theophylline levels range from minor symptoms to life-threatening complications. We investigated the incidence of life-threatening events in patients with elevated levels in order to identify those at low risk for significant theophylline toxicity. Five hundred ten episodes of elevated levels were reviewed in 214 hospitalized patients. Four seizures occurred in patients with prior seizures, while two had new onset seizures with levels of 27 and 30 micrograms/mL. All eight episodes of ventricular tachycardia occurred in patients who had a history of arrhythmias or who were critically ill. Seven patients had new supraventricular arrhythmias with levels of 21 to 40 micrograms/mL. Life-threatening events may occur in critically ill patients or patients with past seizures or arrhythmias with mildly elevated levels, although the extent to which theophylline toxicity contributes to morbidity or mortality in these patients is unclear. Patients who are otherwise healthy are unlikely to have significant theophylline toxicity with levels less than 25 micrograms/mL.

Pacemaker activity is modulated by tissue levels of cyclic adenosine 3',5'-monophosphate in human atrial fibers

We studied the role of tissue cyclic AMP levels in the chronotropic effects of theophylline on automatic human atrial fibers obtained from the hearts of 17 patients undergoing corrective open-heart surgery. Atrial fibers were perfused with Tyrode solution and transmembrane action potentials were recorded with a conventional microelectrode technique. In normal Tyrode solution, theophylline (0.1-1 mM) often decreased the late diastolic slope and the spontaneous rate. In the presence of 0.3-1 microM epinephrine, however, theophylline dose-dependently increased the diastolic slope, the rate of spontaneous discharges and the force of contraction. The increase in tissue level of cyclic AMP (+288 +/- 69%) induced by 0.3 mM theophylline in the presence of epinephrine was much greater than the increase (+73 +/- 19%) in the absence of epinephrine. It is concluded that pacemaker activity in human atrial fibers is modulated by tissue levels of cyclic AMP and theophylline may induce atrial tachycardia through an increase in the diastolic slope and the rate of discharges of automatic atrial fibers.

Theophylline and salbutamol in combination in patients with obstructive pulmonary disease and concurrent heart disease: effect on cardiac arrhythmias

We compared the frequency and severity of cardiac arrhythmias during combined oral theophylline and inhaled salbutamol vs. salbutamol therapy alone in 18 patients with moderate to severe chronic obstructive pulmonary disease who had concurrent cardiac disease. Seventeen patients showed at least one supraventricular premature complex (SVPC) on the 24-h ECG recording when receiving salbutamol alone: eight patients had isolated SVPCs, less than 10/h; five patients had greater than or equal to 10 SVPCs/h; eight patients showed runs of supraventricular tachycardia or paroxysmal atrial fibrillation. Seventeen patients also had at least one ventricular premature complex: seven patients had less than 10 isolated PVCs/h, five patients greater than or equal to 10 PVCs/h; eight patients had paired or multifocal PVCs and one patient a run of ventricular tachycardia. The addition of oral theophylline at an average dose of 600 mg in the evening (blood concentrations showed a mean maximum of 13.4 +/- 4.0 (SD) and minimum of 5.5 +/- 2.9 mg/l) had no influence on the frequency or severity of either ventricular or supraventricular arrhythmias. Thus, cardiac arrhythmias are very common in patients with chronic obstructive pulmonary disease and concomitant heart disease, but oral theophylline added to a regimen of salbutamol does not seem to affect the occurrence or severity of arrhythmias.

Multifocal atrial tachycardia: mechanisms, clinical correlates, and treatment

MAT is an uncommon arrhythmia most often seen in elderly patients with chronic pulmonary disease who are critically ill due to acute respiratory or cardiac decompensation. Its importance lies in the fact that it is commonly mistaken for AF, since both disorders are characterized by narrow ventricular complexes, irregular rates, and (depending on the ECG lead observed in MAT) by an apparent lack of P wave activity. This may lead to treatment with digoxin, a drug known to be ineffective in the therapy of MAT, with the potential for producing toxicity in patients who are predisposed. The incidence of MAT in hospitalized patients in various studies ranges from 0.13% to 0.40%. The mechanism of the arrhythmia is thought to be triggered activity arising from increased intracellular calcium stores that may be produced by hypokalemia, hypoxia, acidemia, and increased catecholamines, characteristics commonly found in patients with MAT. COPD, coronary artery disease, CHF, and infection (both pulmonary and nonpulmonary) are the most common clinical settings of MAT. Mortality is very high in all patients studied, ranging from 38% to 62%, and is due to their underlying disease processes and not to the arrhythmia. The need for intubation and mechanically assisted ventilation portends a particularly poor prognosis for survival. Treatment should initially consist of correction of the precipitating causes, as it is common for patients to convert to sinus rhythm both spontaneously and after these measures are taken.(ABSTRACT TRUNCATED AT 250 WORDS)

Methylxanthines: toxicity to humans. 1. Theophylline

While there are several comprehensive reviews on the toxic effects of theophylline, caffeine and theobromine in animals, data on the toxicity of these methylxanthines in humans have not been extensively reviewed in one document. This question will be addressed in a series of three papers. This paper provides an overview of the human toxicity of theophylline. Only pertinent and recent information on theophylline toxicity is summarized. In addition, some information regarding the use and benefits of theophylline, the mechanism of its effects and factors that affect variability in its clearance and half-life is also provided. Some problems in the analytical methodology of theophylline, problems that may be responsible for the controversy in the reported dose-response effects, are critically reviewed.

Evaluation of theophylline overdoses and toxicities

Patients presenting with elevated theophylline concentrations and manifestations of toxicity may be categorized as being either overdose or iatrogenic toxic. In addition to severe cardiac and neurologic toxicities, such as arrhythmias and seizures, OD patients probably require monitoring for manifestation of gastrointestinal hemorrhage, electrolyte abnormalities, and hypotension. The possibility of a delayed peak theophylline concentration after sustained release product ingestion must be considered. Patients with initial serum concentrations of less than 60 mg/L may receive a single dose of oral activated charcoal and have repeat concentrations drawn to ensure the avoidance of continued absorption. The presence of a serum concentration exceeding 60 mg/L in OD patients warrants initiation of elimination-enhancing modalities. Oral activated charcoal is the fastest and most readily available. Multiple-dose oral activated charcoal should be given until serum theophylline concentrations of 60 mg/L or less are reached. Cardiac monitoring and seizure precautions are recommended. Admission to the intensive care unit should be considered when serum concentrations do not decline after several hours of charcoal therapy or when seizures and severe cardiovascular manifestations occur. Patients having initial concentrations exceeding 100 mg/L and/or rapidly rising concentrations 100 mg/L over baseline values should be considered as candidates for CHP or RHP if available. If both CHP and RHP are unavailable or will be excessively delayed, HD is a reasonable alternative. Patients on chronic theophylline therapy (IA patients) presenting with symptoms of toxicity must be evaluated carefully. If serum concentrations are less than 20 mg/L, short-term observation or a reduction in dose should be sufficient. Patients with concentrations between 20 and 60 mg/L should be candidates for seizure precautions and cardiac monitoring. Oral activated charcoal may be started and continued until levels are below 20 mg/mL. Patients with concentrations in excess of 60 mg/L require intensive monitoring (including seizure precautions and cardiac monitoring) as well as initiation of MOAC or CHP/RHP as situation, availability, and patient tolerance dictate. Again, HD may be a reasonable alternative if the others are unavailable or contraindicated.

Arrhythmogenic effects of theophylline in human atrial tissue

We studied the effects of theophylline on the transmembrane action potential and the contractile force of human atrial fibers obtained from the hearts of 15 patients, undergoing corrective open-heart surgery. Atrial fibers were perfused with Tyrode solution and driven electrically at a constant rate of 60 beats per min. Theophylline (0.1-1 mM) steepened the diastolic depolarization, increased the amplitude of oscillatory potential during diastole and facilitated the development of spontaneous slow response action potentials. These arrhythmogenic effects of theophylline were suppressed after diltiazem (0.1-0.3 microM) pretreatment. The present findings provide the electrophysiologic evidence that abnormal atrial automaticity as a result of triggered activity may be the underlying cause for atrial ectopic activity and multifocal atrial tachycardia in patients taking theophylline.

Pharmacologic management of obstructive lung disease. Current perspectives

Pharmacotherapy of obstructive lung disease has improved both quantitatively and qualitatively in recent decades: quantitatively with improvements in adrenergic and methylxanthine drugs and qualitatively with the addition of new classes of drugs, such as steroids, cromolyn, and, most recently, anticholinergic agents. Management of airways disease is based upon several principles: near-normal airways function should be aimed for; long-term, systemic, moderate-to-high-dose corticosteroids should be avoided if at all possible; the judicious use of polypharmacy should be undertaken whenever necessary to provide effective treatment while minimizing drug side effects; and the therapeutic program for a given individual should be tailored to that patient's specific responses to various treatments. Available pharmacologic agents have varying efficacies and adverse effects. The various agents may be used in a number of combinations.

Cardiac arrhythmias during the combined use of beta-adrenergic agonist drugs and theophylline

We studied 15 nonsmoking, clinically stable asthmatic subjects aged 27 to 39 years to evaluate the potential cardiotoxic effects of combined use of a beta-adrenergic agonist drug and theophylline in the treatment of asthma. Subjects underwent a one-week washout period followed by two one-week periods of study receiving either oral terbutaline or sustained-release theophylline during week 1 and both drugs during week 2. Thirty-six-hour Holter monitoring was performed at the end of each period of study. No significant increase in the total number of ventricular premature beats was noted, although the average heart rate increased significantly between each period of study. Although not statistically significant, the number of individuals with multiform or complete and repetitive ventricular premature beats increased from one at baseline to three during each period of study, including one subject with ventricular tachycardia on combined therapy. These data suggest that combined therapy with theophylline and a beta-adrenergic agonist in young, otherwise healthy asthmatic subjects does not lead to an increase in the total number of ectopic beats but may increase the degree of complexity of ventricular premature beats.

Atrial arrhythmias exacerbated by theophylline. Response to verapamil and evidence for triggered activity in man

A 75-year-old woman with acute respiratory failure due to pneumonia superimposed on bronchospastic chronic obstructive pulmonary disease and dilated cardiomyopathy developed multifocal and unifocal atrial tachycardia. Arrhythmia recurrence appeared to be dependent on reaching a critical but "nontoxic" serum theophylline concentration in the presence of high normal levels of digoxin. The arrhythmias responded to a decrease in serum theophylline concentration or to the administration of verapamil. The precipitation of the atrial arrhythmias by theophylline in the presence of digitalis, both of which may increase intracellular calcium and a dramatic response to verapamil, which inhibits calcium uptake and release, suggests that these arrhythmias may represent an example of "triggered activity" in man.

Update on the pharmacodynamics and pharmacokinetics of theophylline

Theophylline has emerged as a major prophylactic agent for controlling the symptoms of chronic asthma, but it provides little if any relief of pulmonary symptoms caused by irreversible chronic airways obstruction. Although in vitro it inhibits phosphodiesterase and antagonizes adenosine receptors, theophylline's mechanism of action in asthma is unknown. Often, 10 to 20 micrograms/ml is used as the range of serum concentrations where there is the greatest likelihood of obtaining maximal benefit safely. Slow-release products have the potential to provide more stable serum concentrations with longer dosing intervals. However, clinically important differences in rate and sometimes extent of absorption exist between the 15 formulations sold under 29 brand names in this country. In patients with more rapid elimination, few products have sufficiently slow absorption to allow twice-daily use. Often these formulations must be administered every eight hours to prevent breakthrough in asthmatic symptoms despite promotional claims to the contrary. In patients with slower elimination, differences among products are unlikely to be clinically important with 12-hour dosing intervals. Current products approved for "once-a-day" dosing are clinically inadequate because of erratic absorption or excessive serum concentration fluctuations. Moreover, food induces dose dumping of potentially toxic amounts of theophylline from Theo-24, greatly increases the extent of absorption of theophylline from Uniphyl, decreases extent of absorption from Theo-dur-Sprinkle capsules, but has no clinically important effect on Theo-Dur tablets, Theobid, Slo-Bid, or Somophyllin-CRT. The effects of food or other factors that alter gastrointestinal physiology on theophylline absorption are unknown for most other products.