Biomedical subjects
Publications and source records attributed to D L Wolbrette.
Proarrhythmia is defined as the aggravation of an existing arrhythmia or the development of a new arrhythmia secondary to antiarrhythmic drug. Proarrhythmic events include drug-induced bradyarrhythmias, atrial and ventricular proarrhythmias. New onset sustained or incessant ventricular tachycardia and torsade de pointes can be life threatening. This article reviews the incidence, aggravating factors, and treatment of proarrhythmia.
Routine postoperative testing of implanted defibrillators is still debated. While a high-risk subgroup of patients can be identified where this testing is mandatory, those with good results at implants may be less likely to benefit from further testing. Recent data suggests routine testing is justified due to a low, but potentially life-threatening, device failure rate found during postoperative testing. Additionally, patient education is important in the predischarge period. Patients must be knowledgeable regarding potential environmental electromagnetic interference with normal function of their device. Adequate discharge instructions will help reduce patient anxiety over returning to their normal daily activities, and help them adjust psychologically to their defibrillator.
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.
Amiodarone is an antiarrhythmic agent commonly used in the treatment of supraventricular and ventricular tachyarrhythmias. This paper reviews clinical trials in which amiodarone was used in one of the treatment arms. Key post-myocardial infarction trials include EMIAT and CAMIAT, both of which demonstrated that amiodarone reduced arrhythmic but not overall mortality. In patients with congestive heart failure (CHF), amiodarone was associated with a neutral survival in CHF/STAT and improvement in survival in GESICA. In patients with nonsustained ventricular tachycardia, the MADIT trial demonstrated that therapy with an implantable cardioverter-defibrillator (ICD) improved survival compared with the antiarrhythmic drug arm in such patients, most of whom were taking amiodarone. In sustained VT/VF patients, the CASCADE trial demonstrated that empiric amiodarone lowered arrhythmic recurrence rates compared with other drugs guided by serial Holter or electrophysiologic studies. Several trials including AVID, CIDS, and CASH have demonstrated the superiority of ICD therapy compared with empiric amiodarone in improving overall survival. Clinical implications of these trials are discussed.
New indications for pacing are being investigated in the areas of vasovagal syncope, hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy, and atrial fibrillation. It is hoped that pacing will offer an alternative therapy to patients who are refractory to medical therapy. Although pacing for vasovagal syncope continues to be controversial, it appears that a highly symptomatic group with a predominately cardioinhibitory component can benefit. Current data indicate that dual-chamber pacing should not be considered therapeutically equal to septal myectomy in patients with hypertrophic obstructive cardiomyopathy, but may be considered in those more than 65 years of age, or in others who are not good surgical candidates. Biventricular or left ventricular pacing appears promising in heart failure patients and may be combined with implantable cardioverter-defibrillator therapy. Lead technology for coronary vein placement needs further improvement. Dual-site atrial pacing appears to help prevent recurrences of atrial fibrillation and may become a useful adjunct to drug, ablative, and implantable cardioverter-defibrillator therapies.
Amiodarone is an antiarrhythmic agent commonly used in the treatment of supraventricular and ventricular tachyarrhythmias. This article reviews the results and clinical implications of primary and secondary prevention trials in which amiodarone was used in one of the treatment arms. Key post-myocardial infarction primary prevention trials include the European Myocardial Infarct Amiodarone Trial (EMIAT) and the Canadian Amiodarone Myocardial Infarction Trial (CAMIAT), both of which demonstrated that amiodarone reduced arrhythmic but not overall mortality. In congestive heart failure patients, amiodarone was studied as a primary prevention strategy in two pivotal trials: Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiac en Argentina (GESICA) and Amiodarone in Patients With Congestive Heart Failure and Asymptomatic Ventricular Arrhythmia (CHF-STAT). Amiodarone was associated with a neutral overall survival and a trend toward improved survival in nonischemic cardiomyopathy patients in CHF/STAT and improved survival in GESICA. In post-myocardial infarction patients with nonsustained ventricular tachycardia and a depressed ejection fraction, the Multicenter Automatic Defibrillator Implantation Trial (MADIT) demonstrated that implantable cardioverter-defibrillators (ICD) statistically improved survival compared to the antiarrhythmic drug arm, most of whose patients were taking amiodarone. In patients with histories of sustained ventricular tachycardia or ventricular fibrillation, the Cardiac Arrest Study in Seattle: Conventional Versus Amiodarone Drug Evaluation (CASCADE) trial demonstrated that empiric amiodarone lowered arrhythmic recurrence rates compared to other drugs guided by serial Holter or electrophysiologic studies. However, arrhythmic death rates were high in both treatment arms of the study. Several secondary prevention trials, including the Antiarrhythmics Versus Implantable Defibrillators Study (AVID), the Canadian Implantable Defibrillator Study (CIDS), and the Cardiac Arrest Study Hamburg (CASH), have demonstrated the superiority of ICD therapy compared to empiric amiodarone in improving overall survival. Based on the above findings, amiodarone is safe to use in post-myocardial infarction and congestive heart failure patients that need antiarrhythmic therapy. Although amiodarone is effective in treating malignant arrhythmias, high-risk patients should be considered for an ICD as frontline therapy.
Acute treatment of atrial fibrillation is costly although spontaneous conversion rates are high. We reviewed 114 patients admitted to our inpatient service via the emergency department with a principal diagnosis of atrial fibrillation and found the spontaneous conversion rate was 50% in 48 hours, the average length of stay was 3.9 +/- 5.2 days, and the average cost was $6,692 +/- $4,928.
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Multiple trials using antiarrhythmic drugs, pharmacologic therapy, and implantable cardioverter defibrillators have been performed in an attempt to improve survival in patients: (1) postmyocardial infarction; (2) with congestive heart failure, with and without nonsustained ventricular tachycardia; and (3) with sustained ventricular tachycardia and those who have survived an out-of-hospital cardiac arrest. This article reviews some of the key findings and limitations of completed and ongoing trials. We also make recommendations for the current treatment of such patients based on the results of these trials.
Atrial fibrillation is the most common arrhythmia in patients visiting a primary care practice. Although many patients with atrial fibrillation experience relief of symptoms with control of the heart rate, some patients require restoration of sinus rhythm. External direct current (DC) cardioversion is the most effective means of converting atrial fibrillation to sinus rhythm. Pharmacologic cardioversion, although less effective, offers an alternative to DC cardioversion. Several advances have been made in antiarrhythmic medications, including the development of ibutilide, a class III antiarrhythmic drug indicated for acute cardioversion of atrial fibrillation. Other methods of pharmacologic and nonpharmacologic cardioversion remain under development. Until the results of several large-scale randomized clinical trials are available, the decision to choose cardioversion or maintenance of sinus rhythm must be individualized, based on relief of symptoms and reduction of the morbidity and mortality associated with atrial fibrillation.