Preprocedural imaging in patients with transposition of the great arteries facilitates placement of cardiac resynchronization therapy leads.

OBJECTIVE: The purpose of this study is to review a series of patients with complex congenital heart disease in whom preprocedural imaging was used to assist placement of cardiac resynchronization therapy (CRT) leads. BACKGROUND: CRT may be beneficial in patients with a failing systemic ventricle and transposition of the great arteries (TGA). However, complex coronary venous anatomy can be challenging for placement of CRT leads. METHODS: Between October 2006 and June 2012, seven patients with either dextro-TGA (d-TGA) or levo-TGA (l-TGA) underwent preprocedural imaging prior to placement of CRT leads (three, d-TGA and four, l-TGA). Three patients underwent cardiac computed tomography (CT) and four underwent coronary angiography, which included levophase imaging of the coronary sinus (CS) or direct contrast injection of the CS. Where CS anatomy was appropriate with drainage into the systemic venous circulation, a transvenous approach was planned. In all other cases, the patient was referred for surgical placement of epicardial leads. RESULTS: Seven patients were identified with either d-TGA or l-TGA who had undergone preprocedural imaging prior to placement of CRT leads (three, d-TGA and four, l-TGA). Three patients underwent cardiac CT and four underwent coronary angiography, which included levophase imaging of the CS or direct contrast injection of the CS. All seven patients had successful CRT lead placement guided by preprocedure imaging. Three patients required surgical placement whereas four were able to undergo transvenous placement. There were no complications. The majority of patients (four of seven) had improvement in New York Heart Association class as well as subjective improvement in exercise tolerance and energy. The majority of patients also had subjective improvement in systemic right ventricular function by echocardiogram and objective improvement in fractional area change of the right ventricle. The follow-up period ranged from 13 months to 55 months with a mean follow-up of 39 months. CONCLUSIONS: Placement of biventricular leads for CRT in patients with l-TGA or d-TGA is feasible. Preprocedural imaging of the CS allows for better assessment of its anatomy and helps determine procedural approach for CRT placement, thereby limiting unnecessary procedures. In the majority of patients, there was subjective improvement in functional status and right ventricular function; in addition, there was objective improvement in echocardiographic parameters of right ventricular function after CRT placement.

Endocardial electrogram characteristics of epicardial ventricular arrhythmias.

INTRODUCTION: While most ventricular arrhythmias (VA) can be ablated successfully using an endocardial (endo) approach, epicardial (epi) mapping and ablation is sometimes required. There may be suggestive clues on the surface electrocardiogram; however, identification of an epi origin of VA with certainty remains problematic. METHODS AND RESULTS: All patients referred for ablation of ventricular tachycardia or frequent ventricular ectopy from June 2007 to July 2011 were evaluated. Patients with completed endo and epi electroanatomical activation maps of an epi VA were included (n = 10). Bipolar electrograms (EGMs) in the area of earliest endo activation were analyzed and compared to the area of early epi activation. An EGM component was characterized as far field if it was monophasic and there was inability to capture. We identified 3 characteristics from endo mapping that consistently indicated need for epi ablation: (1) Diffusely early activation (>2 cm(2) region of sites with equally earliest activation within 10 milliseconds). (2) Sequence of a far-field EGM followed by a near-field EGM in the region of earliest endo activation. (3) Inability to capture the far-field component of the earliest EGM (stim-QRS < egm-QRS time) or reproduce morphological features of the VA complex with stimulation at the earliest endo site of activation. CONCLUSIONS: The presence of a diffusely early area of activation and inability to capture a far-field endo EGM indicates that epi ablation may be needed to eliminate a VA.

Use of stored implanted cardiac defibrillator electrograms in catheter ablation of ventricular fibrillation.

BACKGROUND: Ventricular fibrillation (VF) can be abolished by targeting triggering ventricular ectopy, most often originating in the Purkinje network or right ventricular outflow tract (RVOT). This strategy relies upon the induction of premature ventricular complex (PVC) and/or VF. We sought to evaluate a VF ablation strategy that utilizes analysis of stored implantable cardioverter defibrillator (ICD) electrograms. METHODS: Eleven consecutive patients experiencing frequent VF episodes (≥three episodes in prior month) underwent electrophysiology study and ablation of VF triggers. PVC and VF induction was intentionally avoided or not possible in all of these patients. Pacemapping at likely sites for PVC triggers of VF using an analysis of the morphology and relative timing of the stored far- and near-field ICD electrograms of VF triggers was used to identify potential culprit locations. Radiofrequency energy was applied to these sites for ablation of the identified VF trigger. RESULTS: Areas targeted for ablation included the left posterior fascicle (six), left anterior fascicle (three), RVOT (three) and left ventricular outflow tract (one); two patients had two separate triggers. Ablation was completed successfully without any complications. With a mean follow-up of 288 days (range 45-649), 10 patients are free of VF. CONCLUSION: Ablation of VF triggers can be performed successfully with good short-term outcomes in patients with and without underlying heart disease. Use of stored ICD electrograms with a focus on likely target areas permit ablation without the need for PVC or VF induction. This can be useful when ectopy is not present for mapping and to avoid potentially dangerous initiation of multiple episodes of VF.

P-wave rejection in a transplanted heart.

BACKGROUND: Heart block can occur at multiple levels in patients with prior cardiac transplant. This diagnosis is usually ascertained using the surface electrocardiogram. RESULTS: A 24-year-old man with prior cardiac transplant presented with apparent complete atrioventricular nodal block and junctional escape on the surface ECG. During pacemaker implantation, we demonstrated sinus rhythm in the recipient atrium, block across the atrioatrial anastomosis, and sinus arrest with intact AV nodal conduction in the donor atrium. CONCLUSION: This case illustrates an unusual presentation of sinus arrest occurring 2 years after heart transplantation that appeared to be complete heart block.

Mastitis unmasks Brugada syndrome.

The Brugada syndrome is an important cause of sudden cardiac death primarily among males without structural heart disease. Although not widely known, it may be unmasked by an acute febrile illness. An association between mastitis and Brugada syndrome has not been previously reported. We describe an 18-year-old postpartum female who developed mastitis, fever, and syncope. Electrocardiography revealed type 1 Brugada pattern, which disappeared once her fever resolved. Although the role of pregnancy in this syndrome is unknown, clinicians should be aware that fever may precipitate Brugada syndrome among peripartum women.

Sequential dual chamber extrastimulation: a novel pacing maneuver to identify the presence of a slowly conducting concealed accessory pathway.

BACKGROUND: Transient VA block can be created in the AV node (AVN) when an atrial extrastimulus is delivered at the AVN effective refractory period (ERP) due to anterograde concealed conduction. OBJECTIVE: We hypothesized that ventricular stimulation during pacing-induced AVN refractoriness could identify concealed accessory pathways (APs) that remain hidden with standard maneuvers. METHODS: Patients undergoing electrophysiological study for supraventricular tachycardia were screened for presence of an AP using standard pacing maneuvers and/or V pacing during adenosine infusion. The dual-chamber sequential extrastimulation maneuver consisted of an 8-beat drive train of simultaneous AV pacing at 600 msec, followed by an A2 delivered at AVN ERP, followed by a V2 delivered at the drive train cycle length (600 msec). Repeat drives were then performed with decrements of 10 msec for V2 until VA block was seen. Retrograde AVN and AP ERP were recorded with standard (V1, V2) and dual-chamber extrastimulation (A1/V1, A2, V2). Patients with an AP identified with standard pacing, manifest pre-excitation, or A ERP < AVN ERP were excluded. RESULTS: Fourteen patients with and 19 patients without an AP were studied. In all patients with an AP, exclusive VA conduction over the AP, without fusion, was seen with the described pacing maneuver. In patients without an AP, retrograde AV nodal ERP was extended by a mean of 138 +/- 46 msec (range 50 to 210 msec) with the A2. Anterograde concealed conduction into the AP was also seen in some patients who showed AP conduction during standard V1V2 pacing (mean retrograde extension of ERP 12 +/- 8 msec, range 0 to 20 msec). CONCLUSION: Dual-chamber sequential extrastimulation is a useful maneuver for identifying slowly conducting APs not revealed with standard pacing maneuvers because of an ERP and conduction time similar to the AVN. The maneuver uses anterograde concealed conduction to prolong AVN refractoriness much more than that of a concealed AP, thereby allowing the AP to become manifest with the V2.

Torsade de pointes associated with very-high-dose methadone.

BACKGROUND: Methadone is an effective treatment for opioid dependency and chronic pain. A methadone derivative, levacetylmethadol, was withdrawn from the European market after being associated with torsade de pointes. To date, no association between methadone and this arrhythmia has been described. OBJECTIVE: To evaluate a series of methadone-treated patients experiencing torsade de pointes. DESIGN: Retrospective case series. SETTING: Methadone maintenance treatment programs in the United States and a pain management center in Canada. PATIENTS: 17 methadone-treated patients who developed torsade de pointes. MEASUREMENTS: Chart review for concomitant arrhythmia risk factors and quantification of corrected QT interval (QTc). RESULTS: The mean daily methadone dose was 397 +/- 283 mg, and the mean QTc interval was 615 +/- 77 msec. Fourteen patients had a predisposing risk factor for arrhythmia. A cardiac defibrillator or pacemaker was placed in 14 patients; all 17 patients survived. CONCLUSIONS: This series raises concern that very-high-dose methadone may be associated with torsade de pointes. Given the likely expansion of methadone treatment into primary care, further investigation of these findings is warranted.