Electrophysiologic and electrocardiographic characteristics and radiofrequency catheter ablation of focal atrial tachycardia originating from the left atrial appendage

BACKGROUND

The left atrial appendage (LAA) is one of the major sources of focal atrial tachycardias (ATs).

OBJECTIVE

The purpose of this study was to investigate the detailed electrophysiologic characteristics and catheter ablation of focal ATs originating from the LAA.

METHODS

The study population consisted of 47 consecutive patients with 50 focal ATs originating from the left atrium (LA): LAA in 13, left pulmonary veins (PVs) in 14, right PVs in 12, and mitral annulus in 11. Programmed electrical stimulation and pharmacologic testing were performed to examine the mechanism of LAA AT. Left atriography was performed prior to radiofrequency ablation to identify the focus in the LAA.

RESULTS

The mechanism of LAA AT was automaticity in 11 and triggered activity in 2. The 13 LAA foci were located mainly at the LAA base: 11 on the medial side and 2 on the lateral side. Atrial activation sequences within the distal coronary sinus were helpful in differentiating these LAA foci. The criterion of a negative P wave in leads I and aVL indicating an LAA AT focus was associated with sensitivity of 92.3%, specificity 97.3%, positive predictive value 92.3%, and negative predictive value 97.3%. No complications occurred in any of the 13 patients. All 13 patients were free of atrial arrhythmias without any antiarrhythmic drugs during follow-up of 8 +/- 3 years.

CONCLUSION

LAA ATs have typical electrophysiologic and electrocardiographic characteristics that are helpful in guiding radiofrequency catheter ablation.

Efficacy of electroanatomic mapping in the catheter ablation of premature ventricular contractions originating from the right ventricular outflow tract

BACKGROUND

Mapping of premature ventricular contractions (PVCs) originating from the right ventricular outflow tract (RVOT) sometimes is not easy because of an unstable incidence and multiple foci of the PVCs. The aim of this study was to evaluate the effectiveness of electroanatomic mapping in catheter ablation of those PVCs.

METHODS AND RESULTS

One hundred patients with 134 RVOT origin PVCs were randomly allotted to undergo either conventional (group I; 50 patients with 65 PVCs) or electroanatomic mapping (group II; 50 patients with 69 PVCs). In group II, electroanatomic mapping of the RVOT was performed using auto-freeze maps in patients with frequent PVCs, and pace mapping was performed marking the pacing sites on the remap which was made by extracting the anatomic frame out of the baseline map during sinus rhythm in patients with infrequent PVCs. Successful ablation was achieved in 44 (88%) group I patients and 48 (96%) group II patients (p = 0.14). The fluoroscopy and procedure times and those per PVC morphology were all significantly shorter in group II than group I overall (p < 0.0001 for all comparisons), and in each patient group with infrequent PVCs, frequent PVCs or unstable PVCs (p < 0.05-0.0001). The number of RF applications and that per PVC was significantly smaller in group II than group I (5.3 +/- 1.8 vs 6.2 +/- 2.4, and 4.4 +/- 1.2 vs 5.2 +/- 2.1; p < 0.05).

CONCLUSIONS

The use of electroanatomic mapping may reduce the fluoroscopy and procedure times in the ablation of RVOT PVCs, but there is no evidence that it improves the overall efficacy of the procedure.

Evidence-based approach to ablating atrial fibrillation

Catheter ablation of atrial fibrillation (AF) has made considerable advances over the past decade. Although pulmonary vein (PV) isolation has proven to be a reliable curative treatment, especially for paroxysmal AF, it still has several issues to resolve. Because the AF mechanisms are complex and multifactorial, especially in persistent or permanent AF, they cannot be eliminated altogether by PV isolation alone. Beyond PV isolation, several other techniques have shown promise in improving the long-term success. Several recent reports comparing the superiority between AF ablation and antiarrhythmic drug therapy have shown early evidence suggesting that AF ablation warrants consideration as a first-line therapy in selected patients.

Preferential Conduction Across the Ventricular Outflow Septum in Ventricular Arrhythmias Originating From the Aortic Sinus Cusp

OBJECTIVES

The purpose of this study was to examine the relationship between the origin and breakout site of idiopathic ventricular tachycardia (VT) or premature ventricular contractions (PVCs) originating from the myocardium around the ventricular outflow tract.

BACKGROUND

The myocardial network around the ventricular outflow tract is not well known.

METHODS

We studied 70 patients with idiopathic VT (n = 23) or PVCs (n = 47) with a left bundle branch block and inferior QRS axis morphology. Electroanatomical mapping was performed in both the right ventricular outflow tract (RVOT) and aortic sinus cusp (ASC) during VT or PVCs.

RESULTS

The earliest ventricular activation (EVA) was recorded in the RVOT in 55 patients (group R) and in the ASC in 15 (group A). In all group R patients, the closest pace map and successful ablation were achieved at the EVA site. Although a successful ablation was achieved at the EVA site in all group A patients, the closest pace map was obtained at the EVA site in 8 and RVOT in 7 (with an excellent pace map in 4). The stimulus to QRS interval was 0 ms during pacing from the RVOT and 36 +/- 8 ms from the ASC. The distance between the EVA and perfect pace map sites in those 4 patients was 11.9 +/- 3.0 mm.

CONCLUSIONS

Ventricular arrhythmias originating from the ASC often show preferential conduction to the RVOT, which may render pace mapping or some algorithms using the electrocardiographic characteristics less reliable. In some of those cases, an insulated myocardial fiber across the ventricular outflow septum may exist.

A Wide QRS Complex Tachycardia with Different Initiation Patterns: What is the Mechanism?

A 47-year-old man with palpitations underwent electrophysiologic testing (EPS). Burst atrial pacing while infusing isoproterenol induced non-reproducible wide QRS tachycardias with an unusual pattern of an H-A-V activation with the same tachycardia cycle length and two different initiation patterns. The tachycardia had the earliest atrial activation at the His bundle region. No dual atrioventricular (AV) nodal physiology was demonstrated by programmed atrial stimulation. Though a definite diagnosis of AV nodal reentrant tachycardia was not obtained, slow pathway ablation was performed in order to avoid inadvertent AV block as a complication. Thereafter, no tachycardias were induced by repeat burst atrial pacing.

One-puncture, double-transseptal catheterization manoeuvre in the catheter ablation of atrial fibrillation

Pulmonary vein isolation (PVI) guided by circumferential mapping has been established as a curative treatment of atrial fibrillation. In the PVI technique, two transseptal catheters are necessary for mapping and catheter ablation. The one-puncture, double-transseptal catheterization manoeuvre is generally used in the PVI technique. However, to the best of our knowledge, there have been no reports describing transseptal manoeuvre in detail. In this article, the manoeuvre to achieve double-transseptal catheterization easily and safely is described.

A Very Narrow Preexisting Isthmus in a Case with Typical Atrial Flutter

A 61-year-old woman with typical atrial flutter underwent an electrophysiologic study and radiofrequency catheter ablation. The electroanatomic mapping revealed two contiguous lines of distinct double potentials (DPs) extending anteriorly/posteriorly from the coronary sinus ostium to the inferior vena cava (IVC) border. A large part of the anterior line of the DPs was close and parallel to the tricuspid annulus (TA). An initial discrete radiofrequency application at the very narrow preexisting isthmus between the TA and anterior line of the DPs completed the IVC-TA isthmus conduction block.

Evaluation of left ventricular mechanical dyssynchrony as determined by phase analysis of ECG-gated SPECT myocardial perfusion imaging in patients with left ventricular dysfunction and conduction disturbances

BACKGROUND

Cardiac resynchronization therapy (CRT) is approved for the treatment of patients with advanced systolic heart failure and evidence of dyssynchrony on electrocardiograms. However, a significant percentage of patients do not demonstrate improvement with CRT. Echocardiographic techniques have been used for more accurate determination of dyssynchrony. Single photon emission computed tomography (SPECT) myocardial perfusion imaging has not previously been used to evaluate cardiac dyssynchrony. The objective of this study is to evaluate mechanical dyssynchrony as described by phase analysis of gated SPECT images in patients with left ventricular dysfunction, conduction delays, and ventricular paced rhythms.

METHODS AND RESULTS

A novel count-based method is used to extract regional systolic wall thickening amplitude and phase from gated SPECT images. Five indices describing the phase dispersion of the onset of mechanical contraction are determined: peak phase, phase SD, bandwidth, skewness, and kurtosis. These indices were determined in consecutive patients with left ventricular dysfunction (n = 120), left bundle branch block (n = 33), right bundle branch block (n = 19), and ventricular paced rhythms (n = 23) and were compared with normal control subjects (n = 157). Phase SD, bandwidth, skewness, and kurtosis were significantly different between patients with left ventricular dysfunction, left bundle branch block, right bundle branch block, and ventricular paced rhythms and normal control subjects (all P < .001) Peak phase was significantly different between patients with right ventricular paced rhythms and normal control subjects (P = .001).

CONCLUSIONS

A novel SPECT technique for describing left ventricular mechanical dyssynchrony has been developed and may prove useful in the evaluation of patients for CRT.

Left ventricular lead implantation in an unusual anatomy of the proximal coronary sinus

A 62-year-old man with Class III heart failure and left bundle branch block underwent cardiac resynchronization therapy. Because prior implantation attempts from the left side were unsuccessful, the right side approach was attempted. However, it was still impossible to advance the pre-shaped sheaths into the distal coronary sinus (CS) because the CS was abnormal with a posterior vertical take off followed by a sharp sigmoid curve before the AV groove. Ultimately, a straight sheath was adjusted to fit the sigmoid curve with the guidance of an electrophysiologic catheter and a left ventricular lead was then passed into the anterolateral vein.

Atrial tachycardia with slow pathway conduction mimicking typical atrioventricular nodal reentrant tachycardia

A 68-year-old woman with palpitations underwent electrophysiologic testing. During burst atrial pacing the PR interval exceeded the RR interval and induced a supraventricular tachycardia consistent with a typical AV nodal reentrant tachycardia (AVNRT). Radiofrequency ablation of the slow pathway during the tachycardia immediately produced 2 : 1 AV conduction. After slow AV nodal pathway ablation an atrial tachycardia (AT) remained inducible with the earliest atrial activation around the HB region. Radiofrequency ablation at the site of earliest atrial activation interrupted the AT without AV block. AT originating from the HB region with slow pathway conduction may mimic typical AVNRT.

Detour conduction can mimic complete conduction block at the cavo-tricuspid isthmus

A 54-year-old man with typical atrial flutter underwent linear ablation at the cavo-tricuspid isthmus. Though standard tricuspid annulus (TA) mapping and differential pacing suggested complete isthmus conduction block, electroanatomic mapping revealed that detoured conduction through a residual conduction gap around the inferior vena cava far from the TA mimicked complete conduction block. Though the double potential interval along the block line was not long enough to guarantee a complete line of block after eliminating the conduction gap, electroanatomic remapping accurately confirmed a complete block line, suggesting electroanatomic mapping may be the most reliable method to confirm complete isthmus conduction block.

Adenosine can also improve the conduction between the superior vena cava and right atrium after isolation

A 64-year-old man with atrial tachycardia (AT) 3 years after a superior vena cava (SVC) isolation for atrial fibrillation underwent electrophysiologic testing. SVC mapping with a basket catheter revealed a more frequent activation in the SVC than in either of the atria during the AT and consequently the recovered conduction between the SVC and right atrium. The conduction improved from 3 or 4-1 conduction to 2-1 conduction after adenosine was administered. Ectopic firing in the SVC persisted even after restoration of sinus rhythm by the successful SVC isolation, which was confirmed by adenosine.

Implant experience with an implantable hemodynamic monitor for the management of symptomatic heart failure

INTRODUCTION

Management of congestive heart failure is a serious public health problem. The use of implantable hemodynamic monitors (IHMs) may assist in this management by providing continuous ambulatory filling pressure status for optimal volume management.

METHODS AND RESULTS

The Chronicle system includes an implanted monitor, a pressure sensor lead with passive fixation, an external pressure reference (EPR), and data retrieval and viewing components. The tip of the lead is placed near the right ventricular outflow tract to minimize risk of sensor tissue encapsulation. Implant technique and lead placement is similar to that of a permanent pacemaker. After the system had been successfully implanted in 148 patients, the type and frequency of implant-related adverse events were similar to a single-chamber pacemaker implant. R-wave amplitude was 15.2 +/- 6.7 mV and the pressure waveform signal was acceptable in all but two patients in whom presence of artifacts required lead repositioning. Implant procedure time was not influenced by experience, remaining constant throughout the study.

CONCLUSION

Based on this evaluation, permanent placement of an IHM in symptomatic heart failure patients is technically feasible. Further investigation is warranted to evaluate the use of the continuous hemodynamic data in management of heart failure patients.

Decrease in fluoroscopic cardiac silhouette excursion precedes hemodynamic compromise in intraprocedural tamponade

BACKGROUND

Acute pericardial tamponade is a life-threatening complication of invasive cardiovascular procedures. Survival depends on early recognition and treatment. A diagnostic test to detect pericardial fluid accumulation before a significant fall in blood pressure and without contamination of the sterile field would be valuable.

OBJECTIVE

We tested the hypothesis that fluoroscopic excursion of the cardiac silhouette decreases early in the course of acute pericardial tamponade and precedes hemodynamic compromise.

METHODS

The pericardial space of seven pigs was accessed by a sub-xiphoid puncture. Tamponade was produced by intrapericardial saline infusion at 20-25 mL/minute until the pericardial pressure equalized with right ventricular end diastolic pressure or the systolic blood pressure reached 40 mmHg. Supine fluoroscopic images were obtained every 2 minutes in the left anterior oblique view with simultaneous echocardiography. The fluoroscopic heart silhouette was digitized, and the maximum excursion during the cardiac cycle was quantified by custom software. The qualitative excursion of the fluoroscopic heart silhouette on randomly selected video images was also graded by two independent observers who were blinded to the time course of the experiment and the hemodynamics.

RESULTS

During progressive pericardial fluid accumulation, the cardiac silhouette excursion quantified by the custom software (p < 0.001) and by video rating (p < 0.0001) was significantly reduced within 2 minutes. A statistically significant fall in blood pressure compared with baseline did not occur until 6 minutes (89 +/- 21 vs. 121 +/- 15 mmHg, p < 0.001). The interobserver agreement was very close, with a kappa statistic of 0.78. The reduction in cardiac silhouette excursion was apparent as soon as the effusion was detected by echocardiography.

CONCLUSION

Cardiac silhouette excursion becomes reduced early in the course of acute pericardial fluid accumulation. This fluoroscopic observation can be used to detect impending pericardial tamponade before hemodynamic collapse.

Transvenous Catheter Cryoablation for Treatment of Atrial Fibrillation:. Results of a Feasibility Study

Pulmonary vein (PV) isolation using radiofrequency (RF) ablation can induce PV stenosis. Cryoablation may offer a safer alternative energy source for PV isolation. PV isolation with cryoablation was attempted in 31 patients with paroxysmal atrial fibrillation (AF). Event monitors were used to measure the AF episode burden. Serial spiral CT scans were obtained to monitor PV stenosis pre- and postcryoablation. Cryoablation was immediately successful for PV isolation in 29 of 31 patients (94%), with 5.9 +/- 1.2 months of follow-up. Additional RF ablation was performed for AF recurrences in seven patients. The remaining 22 patients with a single cryoablation procedure demonstrated a time-dependent, long-term reduction in the frequency of AF episodes. At 6 months of follow-up, 18 of 22 of cryo-treated only patients (82%) were free of symptomatic AF episodes, and antiarrhythmic drugs were discontinued in 12 of 22 patients. Serial spiral CT scans demonstrated no change in the cryo-treated PV ostial diameter. PV cryoablation was effective to control paroxysmal AF in most patients. Early recurrences of AF postcryoablation were common, though tended to resolve within 6 months postablation, consistent with a process of reverse atrial remodeling. Cryoablation of the PVs did not cause PV stenosis or other serious adverse events.

Prophylactic implantable cardioverter-defibrillator therapy in patients with left ventricular systolic dysfunction

Strategies to decrease sudden cardiac death in patients with left ventricular systolic dysfunction are evolving. Recent clinical trials have evaluated the role of prophylactic implantable cardioverter-defibrillators (ICDs) in patients with and without additional risk stratifiers. We pooled studies comparing treatment with and without ICDs from published data and presented abstracts, irrespective of QRS duration and etiology of systolic dysfunction. On the basis of the available clinical trials, implantation of an ICD for primary prevention of death provides a 7.9% absolute mortality reduction (p = 0.003) in patients with left ventricular (LV) systolic dysfunction who were receiving optimized medical therapy. This finding was not sensitive to the exclusion of any individual trial. The ICD is an effective primary preventative measure in patients who are at risk for death; however, the application of this therapy needs to be individualized for the patient, similar to drug therapies in LV systolic dysfunction. In health care settings without unlimited resources, optimal use of this therapy will require better risk stratification methods or lowering of the initial device cost.