Gated blood-pool SPECT evaluation of changes after radiofrequency catheter ablation of accessory pathways: evidence for persistent ventricular preexcitation despite successful therapy

Radionuclide Assessment of Cardiac Function and Dyssynchrony in Children with Idiopathic Ventricular Tachycardia

BACKGROUND

The aim of the study was to evaluate the impact of idiopathic ventricular tachycardia and premature ventricular beats on cardiac function and dyssynchrony and to elucidate relationships between data of scintigraphic and intracardiac electrophysiology studies (EPSs).

METHODS

The study comprised 64 patients with idiopathic ventricular arrhythmias (VAs; median age of 14 years ranging from 8 to 18 years). The control group comprised 20 patients (median age of 12 ranging from 7 to 16 years) without cardiac arrhythmias. EPS and radiofrequency ablation (RFA) procedure for VA were performed in 21 children according to indications. The functional state of both ventricles was assessed by gated blood pool single photon emission computer tomography (GBP-SPECT) before and after RFA in all patients.

RESULTS

Patients with VA had local areas of asynchronous myocardial contraction (AMC). Compared with the control group, VA patients had significantly higher values of end-diastolic volume, end-systolic volume, and lower contractility indices. Negative association was found between total numbers of AMC areas and cardiac contractility indices. Ectopic foci localization, determined based on EPS data, was associated with AMC areas topography based on GBP-SPECT. RFA procedure significantly improved cardiac contractility indices; AMC areas completely disappeared or decreased compared with the preoperative conditions.

CONCLUSION

In VA patients, AMC areas were localized mostly in the right ventricle. Comparison of the results of GBP-SPECT and EPS studies showed a relationship between AMC localizations and ectopic foci topography. The fact that AMC areas disappeared after RFA supports the hypothesis stating that the presence of AMC areas is a scintigraphic symptom of ectopic focus.

LV dyssynchrony as assessed by phase analysis of gated SPECT myocardial perfusion imaging in patients with Wolff-Parkinson-White syndrome

PURPOSE

The purpose of this study was to evaluate left ventricular (LV) mechanical dyssynchrony in patients with Wolff-Parkinson-White (WPW) syndrome pre- and post-radiofrequency catheter ablation (RFA) using phase analysis of gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI).

METHODS

Forty-five WPW patients were enrolled and had gated SPECT MPI pre- and 2-3 days post-RFA. Electrophysiological study (EPS) was used to locate accessory pathways (APs) and categorize the patients according to the AP locations (septal, left and right free wall). Electrocardiography (ECG) was performed pre- and post-RFA to confirm successful elimination of the APs. Phase analysis of gated SPECT MPI was used to assess LV dyssynchrony pre- and post-RFA.

RESULTS

Among the 45 patients, 3 had gating errors, and thus 42 had SPECT phase analysis. Twenty-two patients (52.4%) had baseline LV dyssynchrony. Baseline LV dyssynchrony was more prominent in the patients with septal APs than in the patients with left or right APs (p < 0.05). RFA improved LV synchrony in the entire cohort and in the patients with septal APs (p < 0.01).

CONCLUSION

Phase analysis of gated SPECT MPI demonstrated that LV mechanical dyssynchrony can be present in patients with WPW syndrome. Septal APs result in the greatest degree of LV mechanical dyssynchrony and afford the most benefit after RFA. This study supports further investigation in the relationship between electrical and mechanical activation using EPS and phase analysis of gated SPECT MPI.

Two-dimensional speckle-tracking echocardiography for atrioventricular accessory pathways persistent ventricular pre-excitation despite successful radiofrequency ablation

AIMS

The present study was undertaken to investigate the concordance between longitudinal two-dimensional (2D)-speckle-tracking data and endocardial mapping for localizing atrioventricular accessory pathways (AP), and whether longitudinal 2D-speckle-tracking imaging accurately identifies the contractile abnormalities associated with AP and the effect of radiofrequency ablation.

METHODS AND RESULTS

Echocardiograms were repeated twice in 40 patients with Wolff-Parkinson-White (WPW) syndrome (before and early after ablation) and in 40 healthy controls to obtain longitudinal 2D strain and strain rate data. The site of ablation was considered as the gold standard for the AP localization. While control patients had a homogeneous strain pattern, all but two patients with WPW had an abnormal deformation pattern with three peaks in one or two basal contiguous segments: an early peak concomitantly with the delta wave followed by a systolic and a post-sytolic one. The rapid increase in LV longitudinal deformation within the basal pre-excited zone resulted in a pre-systolic peak strain rate at the beginning of the delta wave by SR imaging that was not found in controls. The early basal contraction spread towards the mid-ventricle before merging with the normal activated segments in 15 patients (39%). Contractile abnormalities were no more than one adjacent segment different compared with the AP ablation site in all these 38 patients. Regional strain was impaired in the pre-excited areas especially in AP localized in the interventricular septum. The abnormal deformation pattern persisted in 16 (42%) patients despite successful radiofrequency ablation. However, the difference in the regional strain between WPW patients and controls did not remain after ablation.

CONCLUSION

Longitudinal 2D-speckle-tracking data accurately match with endocardial mapping findings for localizing AP. Longitudinal 2D-speckle-tracking imaging accurately identifies AP-associated contractile abnormalities. Longitudinal 2D-speckle-tracking identifies persistence of local ventricular pre-excitation immediately after successful ablation.

Detection and quantification by deformation imaging of the functional impact of septal compared to free wall preexcitation in the Wolff-Parkinson-White syndrome

Pacing experiments in healthy animal hearts have suggested a larger detrimental effect of septal compared to free wall preexcitation. We investigated the intrinsic relation among the site of electrical preexcitation, mechanical dyssynchrony, and dysfunction in human patients. In 33 patients with Wolff-Parkinson-White (WPW) syndrome and 18 controls, regional myocardial deformation was assessed by speckle tracking mapping (ST-Map) to assess the preexcitation site, shortening sequences and dyssynchrony, and the extent of local and global ejecting shortening. The ST-Map data in patients with accessory atrioventricular pathways correctly diagnosed as located in the interventricular septum (IVS) (n = 11) or left ventricular free wall (LFW) (n = 12) were compared to the corresponding control values. A local ejecting shortening of <2 SD of the control values identified hypokinetic segments. The localization of the atrioventricular pathways by ST-Map matched with the invasive electrophysiology findings in 23 of 33 patients and was one segment different in 5 of 33 patients. In both WPW-IVS and WPW-LFW, local ejecting shortening was impaired at the preexcitation site (p <0.01). However, at similar electrical and mechanical dyssynchrony, WPW-IVS had more extensive hypokinesia than did WPW-LFW (3.6 +/- 0.9 vs 1.8 +/- 1.3 segments, p <0.01). Compared to controls, the left ventricular function was significantly reduced only in WPW-IVS (global ejecting shortening 17 +/- 2% vs 19 +/- 2%, p = 0.01; ejection fraction 55 +/- 5% vs 59 +/- 3%, p = 0.02). In conclusion, preexcitation is associated with local hypokinesia, which at comparable preexcitation is more extensive in WPW-IVS than in WPW-LFW and could adversely affect ventricular function. ST-Map might have a future role in detecting and guiding treatment of septal pathways with significant mechanical effects.

Nuclear Cardiology: Present and Future

Nuclear cardiology has made significant advances since the first reports of planar scintigraphy for the evaluation of left ventricular perfusion and function. While the current "state of the art" of gated myocardial perfusion single-photon emission computed tomographic (SPECT) imaging offers invaluable diagnostic and prognostic information for the evaluation of patients with suspected or known coronary artery disease (CAD), advances in the cellular and molecular biology of the cardiovascular system have helped to usher in a new modality in nuclear cardiology, namely, molecular imaging. In this review, we will discuss the current state of the art in nuclear cardiology, which includes SPECT and positron emission tomographic evaluation of myocardial perfusion, evaluation of left ventricular function by gated myocardial perfusion SPECT and gated blood pool SPECT, and the evaluation of myocardial viability with PET and SPECT methods. In addition, we will discuss the future of nuclear cardiology and the role that molecular imaging will play in the early detection of CAD at the level of the vulnerable plaque, the evaluation of cardiac remodeling, and monitoring of important new therapies including gene therapy and stem cell therapy.

Radiofrequency catheter ablation of left-sided accessory pathways in pediatric patients

In many cases, radiofrequency catheter ablation has replaced the long-term use of antiarrhythmic medication for symptomatic tachycardia, and has all but eliminated arrhythmia surgery. The most common substrate for radiofrequency catheter ablation in pediatric patients is atrioventricular (AV) reentry tachycardia due to a concealed or manifest accessory pathway. Accessory pathways are distributed unevenly along the right and left atrioventricular valve annuli, and left-sided accessory pathways are most common. Although some centers advocate an abbreviated diagnostic and mapping approach to both concealed and manifest left-sided accessory pathways, most still use a complete electrophysiological evaluation and complex catheter manipulation for mapping, followed by the application of radiofrequency energy. Left-sided accessory pathways may be approached from the transatrial approach, the retrograde aortic approach, or less commonly from within the coronary sinus. Each approach has proven to be associated with success, but also with a distinct set of risks. Possibly because left-sided accessory pathways are most common, catheter ablation of this substrate has proven highly successful and has the lowest risk of recurrence. However, recent data also suggest that this substrate is associated with greater risk of complications than of right-sided accessory pathways or pathways located in the posteroseptal region. The following report reviews some of the recently described diagnostic and mapping techniques, success rates, risks and follow-up data in pediatric patients undergoing radiofrequency catheter ablation of left-sided accessory pathways.