Unresolved issues in implantable cardioverter-defibrillator therapy

Over the last 15 years, a series of well-designed randomized clinical trials has clearly demonstrated that implantable cardioverter-defibrillator (ICD) therapy reduces mortality in select high-risk populations. Despite the widespread acceptance of ICD therapy, many questions related to its optimal use remain. This article discusses several key issues now confronting clinicians.

Device therapies in the post-myocardial infarction patient with left ventricular dysfunction

The post-myocardial infarction (MI) patient with left ventricular dysfunction (LVD) is at risk for ventricular arrhythmias resulting in sudden cardiac death. In high-risk post-MI patients with a depressed left ventricular ejection fraction, prophylactic implantable cardioverter defibrillators (ICDs) may significantly improve survival. These benefits are in addition to those of optimal pharmacologic therapy, and ICD therapy should be considered the standard of care in these patients. Recent device trials have demonstrated the benefits of prophylactic ICD placement in patients who have been selected based on post-MI left ventricular systolic dysfunction alone. In addition, cardiac resynchronization therapy can improve the quality of life beyond that achievable with drug therapy alone and should be considered in patients with symptomatic heart failure with QRS prolongation. Further risk stratification studies of post-MI LVD patients will allow ICD therapy to be applied in a more cost-effective manner.

Real-time rotational ICE imaging of the relationship of the ablation catheter tip and the esophagus during atrial fibrillation ablation

INTRODUCTION

Atrioesophageal fistula is a rare complication of atrial fibrillation (AF) ablation that should be avoided. We investigated whether rotational intracardiac echocardiography (ICE) can help to minimize ablation close to the esophagus.

METHODS AND RESULTS

We studied 41 patients referred for catheter ablation of refractory AF. A rotational ICE catheter was inserted into the (LA) to determine the location of the esophagus. The esophagus was identified to be either adjacent to the pulmonary vein (PV) ostium or to a cuff 2 cm outside the ostium. Circumferential ablation was performed at the PV ostium, with the exact ablation location determined by ICE. The relationship of the catheter tip to the esophagus was imaged during energy delivery, allowing interruption when respiration moved the tip closer to the esophagus. Out of 41 patients, the esophagus was seen near left-sided PVs in 32 and near right-sided PVs in three patients. The median distance from LA endocardium to esophagus was 2.2 mm (range, 1.4-6 mm). In 21 of 35 patients with a closely related esophagus, ablation over the esophagus was avoided by ablating either lateral or medial to the esophagus. In 14 patients, the esophagus could not be avoided, and risk was minimized by limiting lesion size. Significant movement (>10 mm) of the esophagus during the procedure occurred in 3/41 cases.

CONCLUSION

Rotational ICE can accurately determine the distance of ablation sites from the esophagus. Real-time imaging of the relationship of the ablation catheter tip to the esophagus may reduce the incidence of esophageal injury.

Designation and distribution of events in the Multicenter UnSustained Tachycardia Trial (MUSTT)

Patients with coronary artery disease, depressed left ventricular ejection fraction, and nonsustained ventricular tachycardia (VT) have a high mortality rate due to arrhythmic (arrhythmic death/cardiac arrest) and other cardiac causes. The Multicenter UnSustained Tachycardia Trial (MUSTT) investigated whether electrophysiologic study (EPS) was helpful in choosing drug or defibrillator therapy in patients induced into sustained VT. The events committee attempted to categorize follow-up events in patients in MUSTT and to present a detailed breakdown of events. A derivative of the Hinkle-Thaler classification was used, incorporating lessons from other multicenter studies. The committee was blinded to results of EPS and implantable cardioverter-defibrillator (ICD) or other antiarrhythmic therapy status of patients. The primary end point was cardiac arrest or death from arrhythmia. Secondary end points were death from all causes, cardiac causes, and spontaneous sustained VT. Classifications were death and cardiac arrest. Each was similarly divided as arrhythmic with 14 subcategories, e.g., unwitnessed or related to EPS and nonarrhythmic with 10 subcategories, e.g., ischemia. Terminal VF in progressive heart failure was considered nonarrhythmic. Events were reviewed by 2 members. Disagreements were resolved by the 2 members or, if needed, by the full committee. Of the 2,202 patients in MUSTT, there were 902 deaths. Sustained VT requiring cardioversion occurred in 182 patients. An additional 94 patients had resuscitated cardiac arrests. Events occurred in 1,027 patients, and all were reviewed. The 3 leading events were deaths that were classed as sudden/unwitnessed (23% of 902), due to progressive heart failure (22%), or due to noncardiovascular causes (18%). Arrhythmic deaths or cardiac arrests were highest in inducible patients randomized to no antiarrhythmic therapy; next were inducible patients receiving an ICD; and lowest were in patients who were noninducible. In conclusion, the classification system provided a detailed breakdown of events in consistent categories, showing utility for event analysis and interpretation and development of therapeutic strategies. The classifications assigned by the committee were used in all MUSTT outcomes reports, thus affecting all reported outcomes and overall interpretations of the MUSTT.

Chagas myocarditis and syncope

This case report describes the diagnosis of Chagas myocarditis in a patient from Honduras who presented with syncope. The discussion summarizes the pathophysiology of cardiac Chagas disease. Acute, latent, and chronic Chagas myocarditis are described. The role of CMR in diagnosing Chagas myocarditis is discussed.

Psychological indices and phantom shocks in patients with ICD

INTRODUCTION

Some patients with ICDs experience the sensation of a shock in the absence of true therapy (phantom shock). We hypothesize that phantom shocks may be a manifestation of anxiety, depression or PTSD.

METHODS AND RESULTS

All patients over 18 years old with an ICD were eligible to enroll in the study. The first 75 subjects who agreed to participate were enrolled and divided into three groups: ICD patients with phantom shocks (n = 19); ICD patients who had actual shocks (n = 28) and ICD patients who had no shocks (n = 28). During a clinic visit a demographic questionnaire and three psychological rating scales were administered: the Spielberger State-Trait Anxiety Inventory (STAI); the Center for Epidemiologic Studies Depression Scale (CES-D) and the Posttraumatic Stress Checklist (PCL-C). No significant differences between groups were found in gender, race, age, history of MI or cardiac surgery status. Data analysis of the psychological indices using one-way ANOVA showed that the group with phantom shocks had more depression (CES-D p = 0.011) and more anxiety (STAI p = 0.010) than the other groups. Multiple comparisons of group means showed a greater percentage of clinically depressed patients in the phantom shock group than in the other groups.

CONCLUSION

Patients with phantom shocks are more likely to be clinically depressed and have higher levels of anxiety than other ICD patients, regardless of history of actual shocks.

Extent of myocardial viability predicts response to biventricular pacing in ischemic cardiomyopathy

BACKGROUND

The clinical response to biventricular pacing is unpredictable, especially in patients with ischemic cardiomyopathy.

OBJECTIVES

The purpose of this study was to prospectively examine the relationship between the extent of myocardial viability and the response to cardiac resynchronization therapy.

METHODS

Twenty-one patients with ischemic left ventricular (LV) dysfunction (left ventricular ejection fraction [LVEF] 21 +/- 5%), New York Heart Association (NYHA) functional class III-IV, and QRS >120 ms received biventricular devices. Myocardial viability was assessed by myocardial contrast echocardiography, and a perfusion score index (PSI) was calculated from summed segmental perfusion scores. LV performance was assessed by echocardiography on the day after implantation and at 6 months.

RESULTS

PSI was closely correlated with acute improvement in LVEF (P = .003, r = 0.65), stroke volume (P = .02, r = 0.54), and end-systolic volume (P = .05, r = -0.49). PSI also correlated with early diastolic LV relaxation (E', P < .05, r = 0.50) and global myocardial performance or Tei index (P = .003, r = 0.63). By multiple linear regression analysis, PSI provided incremental predictive value to the degree of dyssynchrony, measured by tissue Doppler imaging, for predicting improvement in LVEF. At 6 months, PSI remained positively correlated with improvement in ventricular performance and with reduction in LV end-diastolic dimension (P = .003, r = -0.68). PSI also influenced the clinical variables of NYHA class, 6-minute walk distance, quality-of-life score, and number of hospitalizations for heart failure.

CONCLUSION

In patients with ischemic cardiomyopathy, the extent of myocardial viability predicts acute and long-term improvement in LV performance, exercise tolerance, and reduction in LV end-diastolic dimension with biventricular pacing.

Placement of Transvenous Pacemaker and ICD Leads Across Total Chronic Occlusions

OBJECTIVE

To establish a method of implantation for device leads across total venous occlusions.

BACKGROUND

Indications for pacemaker and implantable cardiac defibrillator implantation continue to expand. Chronic venous occlusions are increasingly encountered with lead placement. Some degree of obstruction can be as high as 13% before device implantation and 50% after transvenous device implantation. We report an approach of venoplasty/dilatation of chronic total occlusions to allow lead placement.

METHODS

From January 1, 2002 through December 16, 2004, 1,356 systems (initial and upgrade) were implanted at the University of Virginia. At the time of device implant, seven patients were noted to have chronic venous occlusions and alternative access was precluded. Four of the seven patients had an existing system; the other three received initial implantations. Subsequently, these seven patients had a 5 Fr catheter placed in the basilic/axillary/subclavian vein and a venogram was obtained to demonstrate the area of chronic occlusion. A guide wire was advanced across the lesion for initial recanalization. Dilatation or venoplasty was performed at the occluded site. A guide wire was retained across the lesion and the patient underwent lead implantation.

RESULTS

In all seven patients, recanalization was achieved and leads were successfully placed. There were no complications or damage to the vessels or existing leads.

CONCLUSIONS

Venoplasty or dilatation of chronic total venous occlusion is a safe and effective technique, which allows for placement of transvenous leads.

Factors affecting bleeding risk during anticoagulant therapy in patients with atrial fibrillation: observations from the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study

BACKGROUND

Stroke and systemic thromboembolism are serious problems for patients with atrial fibrillation (AF), but their incidence can be substantially reduced by appropriate anticoagulation. Bleeding is the major complication of anticoagulant treatment, and the relative risks for bleeding vs stroke must be considered when starting anticoagulation.

METHODS

The AFFIRM trial included patients with AF and at least one risk factor for stroke, randomly assigning them to either a rate-control or rhythm-control strategy. All patients were initially treated with warfarin. The incidence of protocol-defined major and minor bleeding was documented during follow-up. Variables associated with bleeding were determined using a Cox proportional hazards model, using baseline and time-dependent covariates.

RESULTS

The 4060 patients in the AFFIRM trial were followed for an average of 3.5 years. Major bleeding occurred in 260 patients, an annual incidence of approximately 2% per year, with no significant difference between the rate-control and rhythm-control groups. Increased age, heart failure, hepatic or renal disease, diabetes, first AF episode, warfarin use, and aspirin use were significantly associated with major bleeding. Minor bleeding was common in both treatment arms, with 738 patients reporting this problem in one or more visits.

CONCLUSIONS

Bleeding is a significant problem that complicates management of patients with AF. Risk factors for bleeding can be identified, and knowledge of these risk factors can be used to plan therapy.

Clinical factors that influence response to treatment strategies in atrial fibrillation: the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study

BACKGROUND

The AFFIRM Study was a randomized multicenter comparison of 2 treatment strategies, rate-control versus rhythm-control, in high-risk patients with atrial fibrillation (AF). The primary outcome of the trial showed no overall difference in survival between strategies. However, there may be important patient subgroups for which there are identifiable differences in outcome with 1 of the 2 strategies.

METHODS AND RESULTS

Subgroups that were prespecified for analysis from the main AFFIRM Study were age, sex, coronary artery disease (CAD), hypertension, congestive heart failure (CHF), left ventricular ejection fraction (LVEF), rhythm at randomization, first episode of AF, and duration of the qualifying episode of AF. Baseline characteristics were analyzed for each subgroup. Adjusted hazard ratios for each subgroup and for each stratum were generated using Cox models, and these models were used to determine whether treatment strategy affected overall survival differentially by subgroup. Adjusted survival was worse for patients > or =65 years and for patients with a history of CHF, CAD, or an abnormal LVEF. In the adjusted analyses, the effect of treatment strategy was similar within all of the prespecified subgroups. When each subgroup stratum was analyzed separately, patients > or =65 years and patients without a history of CHF had significantly better outcome with rate-control therapy (each P < .01).

CONCLUSIONS

Overall, treatment effect for rate control versus rhythm control was the same within each subgroup. However, certain selected patient categories may have better survival with one particular strategy for management of AF.

Relationships between sinus rhythm, treatment, and survival in the Atrial Fibrillation Follow-Up Investigation of Rhythm Management (AFFIRM) Study

BACKGROUND

The AFFIRM Study showed that treatment of patients with atrial fibrillation and a high risk for stroke or death with a rhythm-control strategy offered no survival advantage over a rate-control strategy in an intention-to-treat analysis. This article reports an "on-treatment" analysis of the relationship of survival to cardiac rhythm and treatment as they changed over time.

METHODS AND RESULTS

Modeling techniques were used to determine the relationships among survival, baseline clinical variables, and time-dependent variables. The following baseline variables were significantly associated with an increased risk of death: increasing age, coronary artery disease, congestive heart failure, diabetes, stroke or transient ischemic attack, smoking, left ventricular dysfunction, and mitral regurgitation. Among the time-dependent variables, the presence of sinus rhythm (SR) was associated with a lower risk of death, as was warfarin use. Antiarrhythmic drugs (AADs) were associated with increased mortality only after adjustment for the presence of SR. Consistent with the original intention-to-treat analysis, AADs were no longer associated with mortality when SR was removed from the model.

CONCLUSIONS

Warfarin use improves survival. SR is either an important determinant of survival or a marker for other factors associated with survival that were not recorded, determined, or included in the survival model. Currently available AADs are not associated with improved survival, which suggests that any beneficial antiarrhythmic effects of AADs are offset by their adverse effects. If an effective method for maintaining SR with fewer adverse effects were available, it might be beneficial.