Tachycardias of Right Ventricular Origin

Human Cardiac Mesenchymal Stromal Cells From Right and Left Ventricles Display Differences in Number, Function, and Transcriptomic Profile

BACKGROUND

Left ventricle (LV) and right ventricle (RV) are characterized by well-known physiological differences, mainly related to their different embryological origin, hemodynamic environment, function, structure, and cellular composition. Nevertheless, scarce information is available about cellular peculiarities between left and right ventricular chambers in physiological and pathological contexts. Cardiac mesenchymal stromal cells (C-MSC) are key cells affecting many functions of the heart. Differential features that distinguish LV from RV C-MSC are still underappreciated.

AIM

To analyze the physiological differential amount, function, and transcriptome of human C-MSC in LV versus (vs.) RV.

METHODS

Human cardiac specimens of LV and RV from healthy donors were used for tissue analysis of C-MSC number, and for C-MSC isolation. Paired LV and RV C-MSC were compared as for surface marker expression, cell proliferation/death ratio, migration, differentiation capabilities, and transcriptome profile.

RESULTS

Histological analysis showed a greater percentage of C-MSC in RV vs. LV tissue. Moreover, a higher C-MSC amount was obtained from RV than from LV after isolation procedures. LV and RV C-MSC are characterized by a similar proportion of surface markers. Functional studies revealed comparable cell growth curves in cells from both ventricles. Conversely, LV C-MSC displayed a higher apoptosis rate and RV C-MSC were characterized by a higher migration speed and collagen deposition. Consistently, transcriptome analysis showed that genes related to apoptosis regulation or extracellular matrix organization and integrins were over-expressed in LV and RV, respectively. Besides, we revealed additional pathways specifically associated with LV or RV C-MSC, including energy metabolism, inflammatory response, cardiac conduction, and pluripotency.

CONCLUSION

Taken together, these results contribute to the functional characterization of RV and LV C-MSC in physiological conditions. This information suggests a possible differential role of the stromal compartment in chamber-specific pathologic scenarios.

The Different Substrate Characteristics of Arrhythmogenic Triggers in Idiopathic Right Ventricular Outflow Tract Tachycardia and Arrhythmogenic Right Ventricular Dysplasia: New Insight from Noncontact Mapping

Background

The aim of this study was to investigate the different substrate characteristics of repetitive premature ventricular complexed (PVC) trigger sites by the non-contact mapping (NCM).

Methods

Thirty-five consecutive patients, including 14 with arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC) and 21 with idiopathic right ventricular outflow tract tachycardia (RVOT VT), were enrolled for electrophysiological study and catheter ablation guided by the NCM. Substrate and electrogram (Eg) characteristics of the earliest activation (EA) and breakout (BO) sites of PVCs were investigated, and these were confirmed by successful PVC elimination.

Results

Overall 35 dominant focal PVCs were identified. PVCs arose from the focal origins with preferential conduction, breakout, and spread to the whole right ventricle. The conduction time and distance from EA to BO site were both longer in the ARVC than the RVOT group. The conduction velocity was similar between the 2 groups. The negative deflection of local unipolar Eg at the EA site (EA slope_3,5,10ms values) was steeper in the RVOT, compared to ARVC patients. The PVCs of ARVC occurred in the diseased substrate in the ARVC patients. More radiofrequency applications were required to eliminate the triggers in ARVC patients.

Conclusions/Interpretation

The substrate characteristics of PVC trigger may help to differentiate between idiopathic RVOT VT and ARVC. The slowing and slurred QS unipolar electrograms and longer distance from EA to BO in RVOT endocardium suggest that the triggers of ARVC may originate from mid- or sub-epicardial myocardium. More extensive ablation to the trigger site was required in order to create deeper lesions for a successful outcome.

Quality of life and cost for patients with premature ventricular contractions by radiofrequency catheter ablation

OBJECTIVE

To evaluate the quality of life (QoL), health-care resource utilization, and cost for the patients with premature ventricular contractions (PVCs) by radiofrequency catheter ablation (RFCA).

METHODS

RFCA was performed in 58 patients with symptomatic PVCs that were refractory/easy to medication. A 24-hour ambulatory electrocardiographic monitoring, QoL, health-care resources utilization, and cost were assessed at a screening visit and 3 and 12 months after RFCA.

RESULTS

RFCA was successfully performed in 56 patients (96.6%). This resulted in a significant improvement in the QoL at 3 and 12 months after the procedure. There were no major complications related to the procedure. Nine patients (15.5%) had residual arrhythmia. Seven of them underwent repeated ablation with successful results. It also improved the QoL and reduced health-care resource utilization and cost.

CONCLUSIONS

RFCA is a safe and effective treatment for PVCs, and it is a viable alternative to drugs in the presence of disabling symptoms.

Right ventricle shape and contraction patterns and relation to magnetic resonance imaging findings

OBJECTIVE

To analyze and to describe the shape and contraction of the normal right ventricle (RV) as visualized by magnetic resonance imaging (MRI).

METHODS

Thirty normal volunteers were imaged using cine MRI in axial, short-axis, and long-axis planes. The shape and contraction of the RV were qualitatively evaluated. Quantitative evaluation of RV shape was performed by calculating the angle subtended between the planes of horizontal long-axis view (HLA) and axial view and the RV base-to-apex distance. Multiplanar reformation was used to visualize changes between corresponding views.

RESULTS

The spectrum of major RV shape (wedge, box, and round) was more variable on axial images (17%, 43%, and 23%, respectively) than on HLA images (63%, 20%, and 0%, respectively). Focal outpouching of the RV free wall was more frequent on the axial view than on the HLA view. The subtended plane angle and base-to-apex distance showed statistically significant dependence indicative of an artificially foreshortened RV in the axial view with a direct influence on RV variations.

CONCLUSIONS

With increasing subtended angles, variation of the normal RV appearance is substantially higher on axial views compared with HLA views.

Intraoperative fracture of the right coronary artery: recognition and management

We describe the recognition and management of two patients who developed intraoperative fracture of the right coronary artery (RCA). Both patients had a calcified RCA without a hemodynamically significant stenosis. Compression of the right atrioventricular groove during the surgical procedure resulted in fracture of the RCA, leading to ventricular arrhythmias and hemodynamic instability. Coronary bypass grafting without cardioplegic arrest was used for definitive diagnosis and treatment. Both patients made a rapid and uneventful recovery.

Arrhythmogenic right ventricular dysplasia

Right ventricular dysplasia (RVD) is a disease entity of unknown cause that is characterised by partial or total replacement of RV-muscle by adipose or fibrous tissue. It is a well-recognized cause of arrhythmia and premature sudden death, but usually underdiagnosed. Several noninvasive and invasive diagnostic modalities have been used, however, all may not be positive in a given case. Drug therapy with class 1c, beta-blocker, and amiodarone in variable combination produce varying success rates in preventing recurrent ventricular tachycardia. Failure of the above measures calls for insertion of implantable cardioverter defibrillator. The attention of emergency physicians is drown to this disease as they are the first medical personnel to be presented with this disease as an emergency. Hence their recognition of RVD will ensure early and proper management.

Significance of morphological abnormalities detected by MRI in patients undergoing successful ablation of right ventricular outflow tract tachycardia

BACKGROUND

MRI can demonstrate subtle morphological changes of the right ventricle in patients with idiopathic right ventricular outflow tract tachycardia (RVOT). The present study examines the incidence and significance of right ventricular (RV) abnormalities detected by MRI with respect to the site of successful radiofrequency catheter ablation of the clinical tachycardia.

METHODS AND RESULTS

The study population comprised 20 patients (mean age, 40+/-12 years) undergoing elimination of recurrent RVOT by radiofrequency catheter ablation. MRI studies were performed before ablation to assess RV volumes and function, as well as structural abnormalities of the RV myocardium. Ten healthy age- and sex-matched subjects served as control subjects. The successful ablation sites, as documented by radiographs of the catheter position, were compared with MRI findings. Patients with RVOT showed no difference in respect to RV volumes and ejection fractions compared with control subjects. Whereas RV abnormalities were limited to prominent fatty deposits of the right atrioventricular groove extending into the inlet portion of the RV wall in 2 of 10 control subjects, MRI studies demonstrated morphological changes of the RV free wall in 13 (65%) of 20 patients with RVOT, including presence of fatty tissue (n=5), wall thinning (n=9), and dyskinetic wall segments (n=4). Eight of these patients had additional fat deposits, thinning, or a saccular aneurysm in the RV outflow tract, corresponding with the ablation site in 6 patients.

CONCLUSIONS

In RVOT, structural abnormalities of the right ventricle can be detected in a substantial number of patients despite normal RV volumes and global function. MRI abnormalities within the RV outflow tract are significantly associated with the origin of tachycardia.

Electrocardiographic features of septal location of right ventricular outflow tract tachycardia

A consistent 12-lead electrocardiogram (ECG) morphology and characteristic frontal plane axis shift from sinus rhythm to ventricular tachycardia (VT) was demonstrated in 10 consecutive patients with idiopathic right ventricular outflow tract (RVOT) VT. All arrhythmias were successfully ablated on the septal side of the RVOT.

Radiofrequency catheter ablation of right ventricular outflow tachycardia in children and adolescents

OBJECTIVES

The current study reviews the safety and efficacy of radiofrequency catheter ablation for the treatment of right ventricular outflow tachycardia in children and adolescents and describes a modified method for mapping the tachycardia focus.

BACKGROUND

Although radiofrequency catheter ablation has proved highly effective for the treatment of supraventricular tachycardia during childhood and adolescence, its application in children with idiopathic right ventricular outflow tachycardia has been limited.

METHODS

Six children (mean [+/- SD] age 10.6 +/- 2.4 years, range 6 to 16) with right ventricular outflow tachycardia underwent seven radiofrequency catheter ablation procedures. The mean tachycardia cycle length was 323 +/- 24 ms (range 300 to 360). Two multipolar catheters were positioned in the right ventricular outflow tract to map the tachycardia focus.

RESULTS

Radiofrequency catheter ablation was successful in five (83%) of the six children (95% confidence interval 36% to 99%). At successful ablation sites, local endocardial activation time preceded the surface QRS onset by 46 +/- 5 ms (range 37 to 57), and there was concordance of the 12-lead pace map and the electrocardiogram (ECG) in 11 (one patient) to 12 ECG leads (four patients). One patient developed complete right bundle branch block during radiofrequency catheter ablation. There were no additional complications and no clinical recurrences over a mean follow-up period of 12.7 +/- 3.8 months (range 9 to 22).

CONCLUSIONS

These results suggest that radiofrequency catheter ablation is a safe and effective treatment for right ventricular outflow tachycardia during childhood and adolescence. In addition, tachycardia mapping may be enhanced by use of a multipolar right ventricular outflow catheter technique.

Current approaches in patients with ventricular tachyarrhythmias

The article has summarized the studies and ongoing trials looking at the significance and treatment of ventricular tachyarrhythmias. In most instances, the presence of these arrhythmias is associated with an increased risk of future arrhythmic events. Electrophysiologic studies are helpful in risk stratification in patients with coronary artery disease but can be misleading in the setting of dilated cardiomyopathy and often produce nonspecific results in patients with HCM. The need for an invasive electrophysiologic study is crucial in the diagnosis of certain ventricular arrhythmias that are amenable to cure with radiofrequency catheter ablation, such as idiopathic ventricular tachycardia and BBR-VT. The correct approach for patients with SVT not amenable to catheter ablation remains to be determined. In deciding whether to use a device or drug therapy, however, one should take into consideration the degree of left ventricular dysfunction and the overall health status of the patient. For example, device implantation clearly reduces sudden death in patients with severe left ventricular dysfunction but may not change total mortality because these same patients may die of congestive heart failure. Device therapy might be more cost-effective for patients with less severe depression of left ventricular function.

Ventricular tachycardia in patients without structural heart disease

The existence of ventricular tachycardia in subjects without detectable heart disease has been recognized for more than half a century. These rhythms occur in younger individuals and account for about 5% of referrals to the electrophysiology service. In contrast, ventricular tachycardia in the setting of chronic ischemic heart disease occurs in an older age group and accounts for more than 90% of all referrals. It is important to be able to distinguish between the different varieties of ventricular tachycardia, because in patients without structural heart disease sudden cardiac death is rare, compared with the very high mortality associated with postischemic recurrent ventricular tachycardia. The natural history of ventricular tachycardia occurring without structural heart disease tends to be benign even when the tachycardia is untreated. Thus these rhythms are more of an annoyance than a life-threatening event. This variety of ventricular tachycardia is frequently not inducible by atrial or ventricular programmed stimulation but is inducible by atrial or ventricular pacing, exercise testing, or isoproterenol infusion. The ventricular tachycardia in patients without structural heart disease is frequently responsive to drugs such as beta-blockers, verapamil, or adenosine that have little or no effect on ventricular tachycardia associated with previous infarction. These differences strongly suggest the possibility of a tachycardia mechanism other than reentry, although conclusive evidence is still lacking.