Exploring TTN variants as genetic insights into cardiomyopathy pathogenesis and potential emerging clues to molecular mechanisms in cardiomyopathies

The giant protein titin (TTN) is a sarcomeric protein that forms the myofibrillar backbone for the components of the contractile machinery which plays a crucial role in muscle disorders and cardiomyopathies. Diagnosing TTN pathogenic variants has important implications for patient management and genetic counseling. Genetic testing for TTN variants can help identify individuals at risk for developing cardiomyopathies, allowing for early intervention and personalized treatment strategies. Furthermore, identifying TTN variants can inform prognosis and guide therapeutic decisions. Deciphering the intricate genotype-phenotype correlations between TTN variants and their pathologic traits in cardiomyopathies is imperative for gene-based diagnosis, risk assessment, and personalized clinical management. With the increasing use of next-generation sequencing (NGS), a high number of variants in the TTN gene have been detected in patients with cardiomyopathies. However, not all TTN variants detected in cardiomyopathy cohorts can be assumed to be disease-causing. The interpretation of TTN variants remains challenging due to high background population variation. This narrative review aimed to comprehensively summarize current evidence on TTN variants identified in published cardiomyopathy studies and determine which specific variants are likely pathogenic contributors to cardiomyopathy development.

Comparison of de novo implantation vs. upgrade cardiac resynchronisation therapy: a multicentre experience

BACKGROUND

The clinical safety and consequences of upgrade procedures compared with de novo cardiac resynchronisation therapy (CRT) implantation in heart failure remain unclear. The present study aimed to assess clinical and procedural consequences of patients undergoing CRT upgrade as compared to de novo CRT implantations.

METHODS

In this prospective cohort study, two subgroups were considered as the study population as (1) de novo group that CRT was considered on optimised medical treatment with heart failure of NYHA functional class from II to IV, left ventricular ejection fraction (LVEF) of ≤35%, and QRS width of >130 ms and (2) upgrade group including the patients with previously implantable cardioverter defibrillator (ICD) with the indications for upgrading to CRT. The two groups were compared regarding the changes in clinical outcome and echocardiography parameters.

RESULTS

The procedure was successful in 95.9% of patients who underwent CRT upgrade and 100% of those who underwent de novo CRT implantation. It showed a significant improvement in LVEF, severity of mitral regurgitation and NYHA functional classification, without any difference between the two study groups. Overall procedural related complications were reported in 10.8% and 3.8% (p = .093) and cardiac death in 5.4% and 2.5% (p = .360), respectively, with no overall difference in postoperative outcome between the two groups.

CONCLUSIONS

Upgrading to CRT is a safe and effective procedure regarding improvement of functional class, left ventricular function status and post-procedural outcome.

Electrocardiographic manifestations of pulmonary stenosis versus pulmonary hypertension

BACKGROUND

Right ventricular hypertrophy can be caused by conditions such as pulmonary stenosis and pulmonary hypertension. ECG is a readily available and affordable test, the aim of this study was the evaluation of the electrocardiographic aspects of pulmonary stenosis, and pulmonary hypertension.

METHODS

A list of patients diagnosed with isolated pulmonary stenosis and pulmonary hypertension patients hospitalized and treated between 2019 and 2021 were extracted from the hospital archives. Furthermore, the ECG of the patients was analyzed in terms of the prevalence of the variables in the study using FECG Caliper software. Finally, the data of 93 patients (in both groups) were analyzed.

RESULTS

In this study, 46 patients were in the severe pulmonary stenosis group, and 49 were in the severe or moderate-to-severe pulmonary hypertension group. The heart rate in the pulmonary hypertension group was significantly higher. R/S > 1 in precordial leads differs between the two groups and higher amplitude R wave in V1(p-value = 0.05). in the pulmonary stenosis group. While in the pulmonary hypertension group, R wave growth occurs later, and this ratio is greater than one after V4. Bundle block in the form of RBBB(p-value <0.001) and maximum QRS duration is more in the pulmonary stenosis group(p-value = 0.001).

CONCLUSION

Our findings show the different strains of the right ventricle in two groups. It can be concluded that the effects of severe pulmonary stenosis on the ECG are more on the QRS wave and in the form of a block, while severe pulmonary hypertension affects the ST segment and T wave.

Role of non-coding variants in cardiovascular disease

Cardiovascular diseases (CVDs) constitute one of the significant causes of death worldwide. Different pathological states are linked to CVDs, which despite interventions and treatments, still have poor prognoses. The genetic component, as a beneficial tool in the risk stratification of CVD development, plays a role in the pathogenesis of this group of diseases. The emergence of genome-wide association studies (GWAS) have led to the identification of non-coding parts associated with cardiovascular traits and disorders. Variants located in functional non-coding regions, including promoters/enhancers, introns, miRNAs and 5'/3' UTRs, account for 90% of all identified single-nucleotide polymorphisms associated with CVDs. Here, for the first time, we conducted a comprehensive review on the reported non-coding variants for different CVDs, including hypercholesterolemia, cardiomyopathies, congenital heart diseases, thoracic aortic aneurysms/dissections and coronary artery diseases. Additionally, we present the most commonly reported genes involved in each CVD. In total, 1469 non-coding variants constitute most reports on familial hypercholesterolemia, hypertrophic cardiomyopathy and dilated cardiomyopathy. The application and identification of non-coding variants are beneficial for the genetic diagnosis and better therapeutic management of CVDs.

Identification of a novel pathogenic variant in KCNH2 in an Iranian family with long QT syndrome 2 by whole-exome sequencing

Background

Long QT syndrome (LQTS) is a lethal cardiac condition. However, the clinical implementation of genetic testing has now made LQTS eminently treatable. Next-generation sequencing has remarkable potential for both clinical diagnostics and research of LQTS. Here, we investigated the genetic etiology in an LQTS-suspected Iranian pedigree by whole-exome sequencing and collected all KCNH2 variants with consensus based on publications.

Methods

WES was performed on the proband of this pedigree to reveal the underlying cause of sudden cardiac death (SCD). The variant found was validated and segregated by polymerase chain reaction and Sanger sequencing. Based on the literature review, KCNH2 variants were retrospectively analyzed to identify pathogenic variants, likely pathogenic variants, and variants of uncertain significance by using different prediction tools.

Results

WES identified an autosomal dominant nonsense variant, c.1425C>A: p.Tyr475Ter, in the KCNH2 gene, which appeared to be the most likely cause of LQTS in this pedigree. Moreover, our comprehensive literature review yielded 511 KCNH2 variants in association with the LQTS phenotype, with c.3002G>A (CADD Phred=49) being the most pathogenic variant.

Conclusions

Variants in the KCNH2 gene are considered a major cause of LQTS worldwide. The detected c.1425C>A is a novel variant to be reported from Iran for the first time. This result indicates the importance of KCNH2 screening in a pedigree with SCD cases.

A survival analysis of bipolar steroid-eluting and unipolar nonsteroid-eluting epicardial leads

INTRODUCTION

Epicardial pacemakers are known as an alternative for endocardial pacemakers in some cases such as heart block, and complex congenital heart diseases. Considering recent advances and improvement of epicardial lead subtypes, it is essential to investigate the long-term function of them. In this study, we aimed to assess the sensing and pacing characteristics, and survival of bipolar steroid-eluting and unipolar nonsteroid-eluting epicardial pacemakers.

METHODS

We conducted an entirely concentrated search on the documents of all patients who had undergone epicardial lead implantation in the Shaheed Rajaie Cardiovascular, Medical & Research Center during 2015-2018. Implant, and follow-up data were extracted. Kaplan-Meier analysis and Weibull regression hazards model were applied for the survival analysis.

RESULTS

Eighty-nine leads were implanted for 77 patients. Of the total leads, 52.81%, 53.93%, and 47.19% were implanted in children (under 18-year-old), females, and patients with congenital heart diseases, respectively. Bipolar steroid-eluting leads comprised 33.71% of 89 leads. The pacing threshold of unipolar nonsteroid-eluting leads that were implanted on the left ventricle and right atrium increased significantly during the follow-up to greater records than bipolar steroid-eluting leads. Survival analysis also revealed that bipolar steroid-eluting leads are significantly better in 48-month survival (Weibull hazard ratio [HR]: 0.13 (95% confidence interval [CI]: 0.02-0.99), p = .049). Age, ventricular location of the lead, and acute pacing characteristics were not associated with survival.

CONCLUSIONS

Bipolar steroid-eluting epicardial leads have an acceptable survival compared with unipolar nonsteroid-eluting, without a significant difference regarding patients age. Therefore, they could be an excellent alternative for endocardial ones.

The Role of Heart Rate Variability and Fragmented QRS for Determination of Subclinical Cardiac Involvement in Beta-Thalassemia Major

Background

Iron accumulation leads to increased susceptibility to cardiovascular diseases in thalassemia major (TM) patients. Depressed heart rate variability (HRV) and development of arrhythmia are among the manifestations of subclinical cardiac involvement in TM cases. Determination of subclinical cardiac involvement is essential for preventive measures. Thus, we aimed to evaluate the best method for identification of subclinical cardiac dysfunction in TM cases.

Materials and Methods

In this prospective study, 45 TM and 45 non-TM cases, who were referred for cardiac evaluation, were enrolled. Exclusion criteria included non-sinus rhythm and overt cardiac disease. TM cases underwent cardiac MRI, electrocardiography (ECG), and Holter monitoring. TM cases were divided into two groups of normal versus iron overload with a cardiac T2* of more or less than 20 ms, respectively. The non-TM cases underwent only ECG and Holter monitoring.

Results

We observed no significant difference regarding HRV between normal versus iron overload TM and non-TM cases. Higher rates of premature atrial complex, low limb voltage, low atrial rhythm, as well as minimum and average HR with lower QRS duration and PR interval were detected in TM versus non-TM cases (p value <0.05).

Conclusions

We observed a higher prevalence of low limb voltage and low atrial rhythm in TM cases versus non-TM cases. Indeed, the role of fragmented QRS (fQRS) for subclinical detection of cardiac disease in TM cases is still so controversial and needs more evaluation. Application of HRV and fQRS in this regard may need to be performed at the right time point after initiation of blood transfusion, but this needs to be determined.

Identification of a Novel KCNQ1 Frameshift Mutation and Review of the Literature among Iranian Long QT Families

Background

Long QT syndrome (LQTS) is characterized by the prolongation of QT interval, which results in syncope and sudden cardiac death in young people. KCNQ1 is the most common gene responsible for this syndrome.

Methods

Molecular investigation was performed by DNA Sanger sequencing in Iranian families with a history of syncope. In silico examinations were performed for predicting the pathogenicity of the novel variant.

Results

A novel homozygous KCNQ1 frameshift mutation, c.1426_1429delATGC (M476Pfs*4), was identified, and then the current literatures of five patients were reviewed regarding the LQTS.

Conclusion

The novel frameshift mutation has been reported for the first time among the Iranian population. Our finding along with the case series study of LQTS patients illustrates the importance of genetic and case series in precise detection of the frequency of LQTS carriers.

Detection of a new KCNQ1 frameshift mutation associated with Jervell and Lange-Nielsen syndrome in 2 Iranian families

Jervell-Lange Nielsen syndrome (JLNS) with autosomal recessive inheritance is a congenital cardiovascular disorder characterized by prolongation of QT interval on the ECG and deafness. We have performed molecular investigation by haplotype analysis and DNA Sanger sequencing in 2 unrelated Iranian families with a history of syncope. Mutational screening of KCNQ1 gene revealed the novel homozygous frameshift mutation c.733-734delGG (p.G245Rfs*39) in 2 obviously unrelated cases of JLNS which is probably a founder mutation in Iran. The novel mutation detected in this study is the first time reported among Iranian population and will be beneficial in the tribe and region-specific cascade screening of LQTS in Iran.

Novel frameshift mutation in the KCNQ1 gene responsible for Jervell and Lange-Nielsen syndrome

Objectives

Jervell and Lange-Nielsen syndrome is an autosomal recessive disorder caused by mutations in KCNQ1 or KCNE1 genes. The disease is characterized by sensorineural hearing loss and long QT syndrome.

Materials and Methods

Here we present a 3.5-year-old female patient, an offspring of consanguineous marriage, who had a history of recurrent syncope and congenital sensorineural deafness. The patient and the family members were screened for mutations in KCNQ1 gene by linkage analysis and DNA sequencing.

Results

DNA sequencing showed a c.1532_1534delG (p. A512Pfs*81) mutation in the KCNQ1 gene in homozygous form. The results of short tandem repeat (STR) markers showed that the disease in the family is linked to the KCNQ1 gene. The mutation was confirmed in the parents in heterozygous form.

Conclusion

This is the first report of this variant in KCNQ1 gene in an Iranian family. The data of this study could be used for early diagnosis of the condition in the family and genetic counseling.

A case of dual atrioventricular nodal nonreentrant tachycardia: An unusual cause of tachycardia-induced cardiomyopathy

We report on a 45-year-old female who developed cardiomyopathy due to incessant dual atrioventricular nodal nonreentrant tachycardia. Her condition was completely resolved by performing radiofrequency ablation of the slow pathway.

[Clinical polymorphisms and approaches of arrhythmias treatment in a family with δKPQ1505-1507 deletion in SCN5A gene]

BACKGROUND

The aim of the study was to analyze spectrum of manifestation and treatment response in large family with rhythm disturbances caused by p.delKPQ1505-1507 mutation in SCN5A gene.

PATIENTS AND METHODS

We had under our observation 18 members of large Iranian family with various combination of inherited arrhythmic syndromes. Careful cardiological examination, genetic councelling and venous blood sampling for molecular genetic study were performed for family members. Mutation screening in SCN5A gene was performed using bidirectional Sanger sequencing.

RESULTS

Here by we show the observation of Iranian family with known mutation p.delKPQ 1505-1507 in SCN5A gene, who display not only LQ-TS phenotype but also some of the carriers of this mutation have had LQ-TS and Brugada syndrome (combine phenotype), interestingly.

CONCLUSION

The overlapping phenotype associated with high risk of sudden cardiac death may require complex approaches to antiarrhythmic therapy, surgical treatment and prevention of sudden cardiac death in the family.

Clinical and electrocardiographic predictors of positive response to the intravenous sodium channel blockers in patients suspected of the Brugada syndrome

BACKGROUND/OBJECTIVES

Sodium channel blockers are used to unmask the diagnostic ECG pattern of the Brugada syndrome (BrS) in case of a non-diagnostic baseline ECG. The aim of the study was to determine clinical and ECG predictors of a positive challenge test in patients suspected to the BrS.

METHODS

A total of 106 consecutive patients (91 men; mean age, 35 ± 12 years) suspected of the BrS underwent the intravenous sodium channel blocker challenge test with procainamide or flecainide.

RESULTS

Of the 106 patients, positive tests were detected in 20 (19%) patients. During test, a transient episode of a second-degree atrioventricular block and isolated ventricular ectopies were observed in 1 (0.9%) and 2 (1.9%) patients, respectively. A QRS prolongation ≥ 30% was observed in 4 (3.8%) patients. Baseline QRS duration in V1 ≥ 110 ms had a sensitivity of 70% and a specificity of 80% for a positive response. An ST-segment elevation ≥ 0.17 mV in V2 had a sensitivity of 60% and a specificity of 82% for a positive response. Of the multiple clinical and ECG variables entered into a binary logistic regression analysis, a history of syncope (P=0.001), previous cardiac arrest (P=0.001), baseline QRS duration in V1 ≥ 110 ms (P=0.001), and baseline ST-segment elevation in V2 ≥ 0.17 mV (P=0.012) emerged as the independent predictors of a positive response to the intravenous challenge with sodium channel blockers.

CONCLUSION

The results of the sodium channel blocker challenge test can be predicted by clinical presentation and baseline ECG features.

Efficacy and safety of different antitachycardia pacing sites in the termination of ventricular tachycardia in patients with biventricular implantable cardioverter-defibrillator

AIMS

We sought to evaluate the efficacy and safety of different antitachycardia pacing (ATP) sites in heart failure (HF) patients with a biventricular implantable cardioverter-defibrillator (ICD).

METHODS AND RESULTS

Between January 2003 and December 2008, 89 consecutive patients with biventricular (BiV) ICDs (Medtronic Inc., St Paul, Minnesota, USA) were enrolled. In these patients, stored electrograms of the true spontaneous ventricular tachycardia (VT) episodes with at least one ATP therapy were analysed. Out of the 89 patients, 46 experienced 259 VT episodes. When we considered all VT forms, both left ventricular (LV)-ATP (91%) and BiV-ATP (89%) were significantly better than right ventricular (RV)-ATP (72%) in terminating VTs (P = 0.03 and 0.04, respectively). In the fastVT zone, there was a trend for higher efficacy of BiV-ATP compared with RV-ATP and LV-ATP (75 vs. 60 vs. 60%, P = 0.10). Fast VT acceleration occurred to a similar extent in all ATP groups (20% in RV-ATP vs. 20% in LV-ATP vs. 20% in BiV-ATP, P = NS). In the slow VT zone, RV-ATP was significantly less effective than LV-ATP (74 vs. 100%, P = 0.001) and BiV-ATP (74 vs. 100%, P = 0.014). Incidence of acceleration was lower with LV-ATP and BiV-ATP than RV-ATP (0 vs. 0 vs. 9%, P = 0.03) in the slow VT zone.

CONCLUSIONS

In HF patients treated with BiV ICD, overall ATP efficacy is higher when delivered from LV or BiV than from RV. Biventricular-ATP and LV-ATP are also safer than RV-ATP in the slow VT zone.

Delayed cardiac perforation by one small body diameter defibrillator lead

We report a 37-year-old man who presented with continuous chest pain 6 weeks after implantable cardioverter-defibrillator implantation. Implantable cardioverter-defibrillator interrogation indicated complete loss of capture even with maximum output. Chest radiography and echocardiography confirmed extracardiac location of lead tip. After lead repositioning in electrophysiology laboratory, acceptable pacing threshold was obtained with no complication. This report demonstrates a case of delayed cardiac perforation after implantation of the St Jude Medical Durata implantable cardioverter-defibrillator lead.

Predictors of ventricular tachycardia induction in syncopal patients with mild to moderate left ventricular dysfunction

BACKGROUND

In patients with mild to moderate left ventricular dysfunction (LVD) (35% pound LVEF pound 50%) who present with syncope, demonstration of tachy and/or brady-arrhythmia has prognostic value. In this group of patients electrophysiological study (EPS) is often necessary.

METHODS

A total of 53 consecutive patients with mild to moderate LVD and history of undetermined syncope underwent EPS. Sinus node function, His-Purkinje system conduction and ventricular electrical stability were evaluated.

RESULTS

Twenty eight patients (52.8%) had induction of sustained monomorphic ventricular tachycardia (VT) and five (9.4%) patients had a sustained ventricular arrhythmia other than monomorphic VT (ventricular flutter, ventricular fibrillation, and polymorphic VT) induced during EPS. Abnormal sinus node function and/or His-Purkinje system conduction was found in five (9.4%) patients. Age, gender, history of myocardial infarction, type of underlying heart disease and history of revascularization were not predictors of VT induction. Wide QRS morphology independently, and lower left ventricular ejection fraction and presence of pathologic q wave in precordial leads dependently, could increase risk of VT induction.

CONCLUSIONS

The EPS can determine which patient with syncope and mild to moderate LVD is likely to benefit from placing an ICD for prevention of sudden cardiac death. Pathologic precordial q wave, wide QRS morphology and lower left ventricular ejection fraction could be predictors of VT induction during EPS. Wide QRS morphology has an independent effect in this category.

Can prodromal symptoms predict recurrence of vasovagal syncope?

BACKGROUND

Vasovagal syncope (VVS) is a common symptom with empirical therapy and high recurrence rate. Our goal was to determine whether the pattern of presyncopal prodromal symptoms can predict the recurrence probability of vasovagal syncope.

METHODS

Seventy-nine consecutive patients (male/female: 53/26) with history of VVS and positive tilt table test (TTT) were enrolled in the study and completed the follow-up time for one year. They all had normal electrocardiograms and cardiac echocardiography without underlying disease. All of them were evaluated meticulously for prodromal symptoms (diaphoresis, nausea, palpitation and blurred vision) and frequency of syncopal spells in their past medical history. They received metoprolol at maximum tolerated dose and were taught tilt training as an empirical therapy after TTT.

RESULTS

Fifty-four patients (68.4%) reported at least one of the four main prodromal symptoms. Median syncopal +/- presyncopal spells were 4 episodes. Forty-two patients (53.2%) experienced recurrence of syncope or presyncope during the follow-up period. In recurrent symptomatic patients, diaphoresis had been more significantly reported in their past medical history (p = 0.018) and they had more syncopal spells before TTT (p = 0.001). Age, gender and type of TTT response did not have any effect on the recurrence of VVS.

CONCLUSIONS

Patients with a history of diaphoresis as a prodromal symptom and more pretilt syncopal attacks experience more syncopal or presyncopal spells during follow-up.

Relationship between QRS complex notch and ventricular dyssynchrony in patients with heart failure and prolonged QRS duration

BACKGROUND

Cardiac resynchronization therapy (CRT) has been accepted as an established therapy for advanced systolic heart failure. Electrical and mechanical dyssynchrony are usually evaluated to increase the percentage of CRT responders. We postulated that QRS notch can increase mechanical LV dyssynchrony independently of other known predictors such as left ventricular ejection fraction and QRS duration.

METHODS

A total of 87 consecutive patients with advanced systolic heart failure and QRS duration more than 120 ms with an LBBB-like pattern in V1 were prospectively evaluated. Twelve-lead electrocardiogram was used for detection of QRS notch. Complete echocardiographic examination including tissue Doppler imaging, pulse wave Doppler and M-mode echocardiography were done for all patients.

RESULTS

Eighty-seven patients, 65 male (75%) and 22 female (25%), with mean (SD) age of 56.7 (12.3) years were enrolled the study. Ischemic cardiomyopathy was the underlying heart disease in 58% of the subjects, and in the others it was idiopathic. Patients had a mean (SD) QRS duration of 155.13 (23.34) ms. QRS notch was seen in 49.4% of the patients in any of two precordial or limb leads. Interventricular mechanical delay was the only mechanical dyssynchrony index that was significantly longer in the group of patients with QRS notch. Multivariate analysis revealed that the observed association was actually caused by the effect of QRS duration, rather than the presence of notch per se.

CONCLUSIONS

QRS notch was not an independent predictor of higher mechanical dyssynchrony indices in patients with wide QRS complex and symptomatic systolic heart failure; however, there was a borderline association between QRS notch and interventricular delay.

Can successful radiofrequency ablation of atrioventricular nodal reentrant tachycardia be predicted by pattern of junctional ectopy?

BACKGROUND

Emergence of junctional rhythm (JR) during radiofrequency (RF) current delivery directed at the periatrioventricular nodal region has been shown to be a marker of success in atrioventricular nodal reentrant tachycardia (AVNRT). Whereas the characteristics of JR during RF ablation of slow pathway have already been studied, the electrophysiologic features of different patterns of JR are yet to be evaluated. The aim of this study was to investigate in detail the characteristics of the JR that develops during the RF ablation of the slow pathway.

MATERIALS AND RESULTS

The study population consisted of 95 patients: 56 women and 33 men (mean age, 47.2 +/- 16.3 years) who underwent slow pathway ablation because of AVNRT. A combined anatomical and electrogram mapping approach was used, and AVNRT was successfully eliminated in all patients. This study identified 7 patterns for JR during the RF ablation of slow pathway: junction-junction-junction, sinus-junction-sinus, intermittent burst, sparse, no junction, sinus-junction-junction, and sinus-junction-block . The characteristics of JR, such as mean cycle length and total number, were gathered. The incidence of JR was significantly higher during effective applications of RF energy than during ineffective applications (P = .001). The mean number of junctional ectopy was 19.6 +/- 19. The total number of junctional ectopy was significantly higher during effective applications of RF energy than during ineffective applications (24.6 +/- 18.8 vs 8.4 +/- 13.2; P < .001). We found a significant difference between the effective and ineffective applications of RF energy in the mean cycle length of the junctional ectopy (464.6 +/- 167.5 vs 263.4 +/- 250.2; P < .01). The patterns of JR were compared between effective and ineffective applications. We managed to show a significant correlation between patterns of JR and successful ablation (P = .01). Logistic regression analysis revealed that the presence of sinus-junction-sinus, sinus-junction-junction, and sinus-junction-block patterns of JR was a predictor of a successful RF ablation (confidence interval [CI], 1.67-15.92 [P < .004]; CI, 1.02-85.62 [P = .048]; and CI, 1.06-32.02 [P = .042], respectively).

CONCLUSION

This study confirms that JR is often present during successful slow pathway ablation. The pattern of JR is useful as indicator of success.

Early septal activation, successful lateral ablation

The coronary sinus activation pattern is an important clue for the detection of arrhythmia mechanisms and/or localization of accessory pathways. Any change in this pattern during radiofrequency ablation should be evaluated carefully to recognize the presence of another accessory pathway or innocence of the accessory pathway during arrhythmia. Intra-atrial conduction block can change the coronary sinus activation pattern. Negligence regarding this phenomenon can cause irreversible complications. Here we describe a case with left lateral accessory pathway conduction in which intra-atrial conduction block completely reversed the coronary sinus activation pattern.

Optimal β-blocker for prevention of atrial fibrillation after on-pump coronary artery bypass graft surgery: Carvedilol versus metoprolol

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia after coronary artery bypass graft (CABG) surgery. It has been shown that prophylactic oral beta-blocker administration reduces the incidence of post-CABG AF. However, the optimal beta-blocker has not been identified.

OBJECTIVE

This study sought to determine whether oral carvedilol (with its unique anti-inflammatory and antioxidant properties) is more effective than oral metoprolol for prevention of AF after CABG surgery.

METHODS

Between April 2006 and December 2006, 120 patients (63 men, mean age 61 +/- 9.4 years) who were scheduled to undergo their first on-pump CABG were enrolled in this study. The patients were randomized in a prospective 1:1 manner to receive either oral carvedilol (n = 60) or oral metoprolol (n = 60). The end point of the study was the occurrence of the new-onset AF during the first 5 days after CABG.

RESULTS

AF occurred in 29 of 120 patients (24.0%). The incidence of postoperative AF was 15.0% (9 of 60) in the carvedilol group and 33% (20 of 60) in the metoprolol group (P = .022). The carvedilol group was treated with mean daily dose of 46 +/- 9 mg and metoprolol group with mean daily dose of 93 +/- 11 mg. There were no differences between the study groups regarding any known preoperative, perioperative, or postoperative characteristics (all values were P >.05). No significant adverse effect was observed in either group.

CONCLUSION

This prospective study suggested that oral carvedilol is more effective than oral metoprolol in the prevention of AF after on-pump CABG. It is well tolerated when started before and continued after the surgery. However, further prospective studies are needed to clarify this issue.

Prevalence of Mechanical Dyssynchrony in Heart Failure Patients with Different QRS Durations

BACKGROUND

Cardiac resynchronization therapy (CRT) has emerged as an established therapy for congestive heart failure. However, up to 30% of patients fail to respond to CRT despite prolonged QRS.

OBJECTIVES

This study aimed at defining the prevalence of interventricular and intraventricular dyssynchrony in heart failure patients with different QRS durations.

METHODS

A total of 123 consecutive patients with severe heart failure (LVEF < 35% and NYHA class III-IV) were prospectively evaluated using 12-lead electrocardiogram and complete echocardiographic examination including tissue Doppler imaging.

RESULTS

According to the QRS duration, 56 patients had a QRS duration < or = 120 ms (Group 1), 33 patients had a QRS duration between 120 and 150 ms (Group 2), and 34 patients had a QRS duration > or = 150 ms (Group 3). Intraventricular dyssynchrony was present in 36% of Group 1 patients, in 58% of Group 2 patients, and in 79% of Group 3 patients (P < 0.000). Linear regression demonstrated a weak relation between QRS and intraventricular dyssynchrony. A greater proportion of patients with interventricular dyssynchrony was observed in Group 3 or Group 2 compared to patients with normal QRS duration (32% in Group 1 vs. 51.5% in Group 2 vs. 76.5% in Group 3, P < 0.000). Linear regression demonstrated a significant relation between QRS duration and interventricular mechanical delay.

CONCLUSIONS

Although both interventricular and intraventricular dyssynchrony increased with the increasing QRS duration, the correlation between intraventricular mechanical and electrical dyssynchrony was weak. The lack of intraventricular dyssynchrony in a fraction of patients with standard CRT indication by QRS duration may provide us insight into the nonresponders rates.

Predictors of venous obstruction following pacemaker or implantable cardioverter-defibrillator implantation: a contrast venographic study on 100 patients admitted for generator change, lead revision, or device upgrade

AIM

Venous obstruction following transvenous device implantation rarely cause immediate clinical problems. When lead revision or device upgrade is indicated, venous obstruction become a significant challenge. The aim of this study was to determine the predictors of venous obstruction after transvenous device implantation, and to asess likely effects of antiplatelet/anticoagulant drugs in preventing venous thrombosis.

METHODS AND RESULTS

Between March 2005 and July 2006, contrast venography was performed in 100 patients who were candidates for generator change, lead revision, or device upgrade. Vessel patency was graded as either completely obstructed, partially obstructed (>70%), or patent. The incidence of venous obstruction was 26%, with 9% of patients having total obstruction and 17% of patients exhibiting partial obstruction. No statistically significant differences between obstructed and non-obstructed patients were seen for age, sex, indication for device implantation, atrial fibrillation, cardiothoracic ratio, insulation material, operative technique, device type, and manufacturer (all Ps > 0.05). In a univariate analysis, multiple leads (P = 0.033), and presence of dilated cardiomyopathy (P = 0.036) were associated with higher risk of venous obstruction, whereas anticoagulant/antiplatelet therapy (P = 0.047) significantly reduced incidence of venous obstruction. Multivariate logistic regression analysis showed that only number of the leads (P = 0.039, OR: 2.22, and 95% CI: 1.03-4.76) and antiplatelet/anticoagulant therapy (P = 0.044, OR: 2.79, and 95% CI: 0.98-7.96) were predictors of venous obstruction.

CONCLUSION

Total or partial obstruction of the access veins occurs relatively frequently after pacemaker or ICD implantation. Multiple pacing or ICD leads are associated with an increased risk of venous obstruction, whereas antiplatelet/anticoagulant therapy appears to have a preventive effect on development of access vein thrombosis.

Correlation between results of head-up tilt test and clinical features in patients with syncope or presyncope

BACKGROUND

Head-up tilt test (HUTT) is a well-established diagnostic tool in patients with suspected vasovagal syncope. Identification of factors that predict a positive HUTT result could simplify diagnostic steps. The aim of this study was to assess the correlation between clinical characteristics of patients with suspected neurocardiogenic syncope or presyncope and results of HUTT.

MATERIALS AND METHODS

The study group consisted of 90 patients (55 men, 35 women; mean age, 43.2 +/- 17 years) with a history of syncope or presyncope. Cardiological and neurologic test findings were normal in every patient. The patients were tilted to a 70 degrees position for 45 minutes. If the first phase produced a negative response, the patients received 400 mug of sublingual nitroglycerin for the second phase and continued to be tilted for an additional 15 minutes.

RESULTS

Sixty-four patients had a positive HUTT result, characterized by a vasodepressive response in 26 patients, mixed response in 24 patients, and cardioinhibitory response in 14 patients. In logistic regression analysis, the presence of prodromal symptoms was a predictor of a positive HUTT result (P = .002).

CONCLUSION

We showed that the prognostic performance of clinical features, including the time interval between the last episode and HUTT, the number of syncope or presyncope episodes, age, and sex, was not ideal. The presence of prodromal symptoms might be more likely to predict a positive response during HUTT.

Electrophysiologic characteristics and results of radiofrequency catheter ablation in elderly patients with atrioventricular nodal reentrant tachycardia

BACKGROUND

As in the general population, atrioventricular nodal reentrant tachycardia (AVNRT) is the most common regular supraventricular tachycardia in the elderly patients. We tried to compare electrophysiologic characteristics, efficacy, and risks of the radiofrequency (RF) catheter ablation of the slow pathway in elderly and young patients with AVNRT.

METHODS

Between April 2001 and March 2005, 268 consecutive patients (190 females; mean age, 49 +/- 14 years) with AVNRT underwent RF catheter ablation at our institution. The patients were categorized into 2 groups: group 1 consists of patients younger than 65 years (n = 156), and group 2 consists of patients 65 years or older (n = 112).

RESULTS

Compared with the younger subgroup, elderly patients more often had structural heart disease (11.6% vs 2.5%, P = .004), but there were no statistically significant differences in sex and symptoms during tachycardia (all P > .05). AVNRT cycle length was significantly longer in group 2 than in group 1 patients (P = .005). Among the conduction intervals of tachycardia, only atrio-his interval was significantly longer in group 2 patients (P = .007). The ablation fluoroscopy time, RF pulse duration, target temperature, applied energy, and number of RF applications were comparable in the 2 groups (All P > .05). Risk of atrioventricular block, pericardial effusion, and vascular thrombosis were similar in both groups (All P > .05). During follow-up with duration of 14 months, similar rate of recurrence was observed in the 2 groups (P = .94).

CONCLUSIONS

In elderly patients, slow pathway ablation is as effective and safe as in younger patients. Therefore, when considering different treatment options in elderly patients, an increased risk of complications or lower efficacy should not be a factor in determining the best therapeutic approach.

Spontaneous alternans in Brugada ECG morphology

A 23-year-old man presented with sick sinus syndrome and Brugada-like ECG pattern. Coved type ECG (type 1) converted to saddleback configuration (type 2) when R-R interval decreased and it changed to coved type pattern with increasing R-R cycle length. During stable heart rate, there was no change in Brugada ECG pattern. The R-R interval effect on these patterns can be explained by intensity or kinetics of ion currents and autonomic tone.

The effect of preoperative aspirin use on postoperative bleeding and perioperative myocardial infarction in patients undergoing coronary artery bypass surgery

BACKGROUND

We tried to evaluate the clinical outcomes (mortality, postoperative bleeding and perioperative myocardial infarction) of patients who underwent first elective coronary artery bypass grafting and received aspirin during the preoperative period.

METHODS

The study was a prospective, randomized and single-blinded clinical trial. Two hundred patients were included and divided into two groups. One group received aspirin 80-160 mg, while in the other aspirin was stopped at least seven days before surgery. The primary end-points of the study were in-hospital mortality and hemorrhage-related complications (postoperative blood loss in the intensive care unit, re-exploration for bleeding and red blood cell and non-red blood cell requirements). The secondary end-point was perioperative myocardial infarction.

RESULTS

There were no differences in patient characteristics between the aspirin users and non-aspirin users. We found a significant difference between postoperative blood loss (608 +/- +/- 359.7 ml vs. 483 +/- 251.5 ml; p = 0.005) and red blood cell product requirements (1.32 +/- +/- 0.97 unit packed cell vs. 0.94 +/- 1.02 unit packed cell; p = 0.008). There was no significant difference between the two groups regarding platelet requirement and the rate of in-hospital mortality and re-exploration for bleeding. Similarly, we found no significant difference in the incidence of definite and probable perioperative myocardial infarction (p = 0.24 and p = 0.56 respectively) or in-hospital mortality between the two groups.

CONCLUSION

Preoperative aspirin administration increased postoperative bleeding and red blood cell requirements with no effect on mortality, re-exploration rate and perioperative myocardial infarction. We recommend withdrawal of aspirin seven days prior to surgery. (Cardiol J 2007; 14: 453-457).

A patient with sick sinus syndrome, atrial flutter and bidirectional ventricular tachycardia: Coincident or concomitant presentations?

Channelopathies are among the major causes of syncope or sudden cardiac death in patients with structurally normal hearts. In these patients, the atrium, ventricle or both could be affected and reveal different presentations. In this case, we present a patient with an apparently structurally normal heart and recurrent syncope, presented as sick sinus syndrome with atrial flutter and bidirectional ventricular tachycardia. (Cardiol J 2007; 14: 585-588).

Early risk stratification for arrhythmic death in patients with ST-elevation myocardial infarction

BACKGROUND

Sudden cardiac death is a leading cause of death in patients with ST-elevation myocardial infarction (MI). According to high cost of modern therapeutic modalities it is of paramount importance to define protocols for risk stratification of post-MI patients before considering expensive devices such as implantable cardioverter-defibrillator.

METHODS

One hundred and thirty seven patients with acute ST-elevation MI were selected and underwent echocardiographic study, holter monitoring and signal-averaged electrocardiography (SAECG). Then, the patients were followed for 12 +/-3 months.

RESULTS

During follow-up, 13 deaths (9.5%) occurred; nine cases happened as sudden cardiac death (6.6%). The effect of ejection fraction (EF) less than 40% on occurrence of arrhythmic events was significant (P<0.001). Sensitivity and positive predictive value of EF<40% was 100% and 76.95% respectively. Although with lesser sensitivity and predictive power than EF<40%, abnormal heart rate variability (HRV) and SAECG had also significant effects on occurrence of sudden death (P=0.02 and P=0.003 respectively). Nonsustained ventricular tachycardia was not significantly related to risk of sudden death in this study (P=0.20).

CONCLUSION

This study indicated that EF less than 40% is the most powerful predictor of sudden cardiac death in post MI patients. Abnormal HRV and SAECG are also important predictors and can be added to EF for better risk stratification.

Latent Atriofascicular Pathway Participating in a Wide Complex Tachycardia: Differentiation from Ventricular Tachycardia

Accessory pathways with anterograde decremental conduction properties usually are characterized by presence of antegrade preexcitation during atrial pacing. We report a 38-year-old man with frequent episodes of palpitation. No evidence of ventricular preexcitation was seen during sinus rhythm or atrial pacing. All electrophysiologic maneuvers were compatible with an antidromic tachycardia using atriofascicular pathway as the antegrade limb and the atrioventricular nodal pathway as retrograde limb. Radiofrequency ablation at recording site of accessory pathway potential resulted in cure of tachycardia with no recurrence during 3-month follow-up. This report indicated that atriofascicular pathway-mediated tachycardia should be considered in differential diagnosis of all cases of wide complex tachycardia with left bundle branch morphology and left axis.

A Randomized Trial Oral Propranolol versus Metroprolol in Treatment of Neurally Medicated Cyncope

BACKGROUND

Beta-blockers has been claimed to be useful in chronic prophylaxis of neurally mediated syncope with frequent recurrences. However, efficacy of cardioselective and non-cardioselective beta-blockers has never been compared in a randomized study.

METHODS

From October 2003 to December 2004, 62 patients (32 men, mean age 44.8 +/- 19.3 years) who had at least one episode of syncope per month during previous 6-months and had positive tilt test were enrolled in this study. The patients were randomly assigned to receive either propranolol (Group I, n = 31) or metoprolol (Group II, n = 31). After one month, efficacy of treatment was also tested by a repeat head-up tilt test (HUTT).

RESULTS

There were no statistically significant differences between the two groups with respect to the HUTT pattern (P=0.25) and requirement for sublingual NTG during test (P=0.20). After one month of treatment, oral beta-blockers prevented the occurrence of syncope during second HUTT in 11 patients (35.5%) in the Group I and 9 (29%) patients in the Group II (P=0.58) and delayed the occurrence of symptoms in 9 Group I patients (29%) and 8 Group II patients (16%) (P=0.77). During the 16-months follow-up, 53 patients (85.5%) remained free of syncope. No statistically significant difference was observed between the two groups with respect to recurrence of syncope (P=0.47). In both groups, the patients in whom treatment efficacy was proved by a negative tilt test had similar recurrence of syncope as those patients who had a positive tilt test (Both P>0.05).

CONCLUSIONS

Both cardioselective and noncardioselective oral beta-blockers were similarly effective in preventing recurrence of syncope in patients with neurally-mediated syncope. In both groups, HUTT performed one month after the treatment had no role in prediction of responders.

Optimal target temperature for slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia

OBJECTIVE

To define optimal target temperature for the slow pathway ablation.

MATERIALS AND METHODS

In this study, 268 patients with atrioventricular nodal reentrant tachycardia (190 females; mean age, 49 +/- 14 years) who underwent slow pathway ablation using a combined electroanatomic approach were enrolled. The patients were categorized into Group 1 if target temperature was < 55 degrees C or into Group 2 if target temperature was > or = 55 degrees C. Group 2 was divided into three subgroups of 55 degrees C (Sgp-1), 60 degrees C (Sgp-2), and 65 degrees C (Sgp-3).

RESULTS

Acute success rate was similar in both groups (P = 0.83). The ablation time (26.2 +/- 20 vs. 36.5 +/- 28 min; P = 0.014), fluoroscopy time (11.6 +/- 9.7 vs. 17.8 +/- 16.6 min; P = 0.035), and number of applications (4.1 +/- 3.2 vs. 9.1 +/- 6.5; P = 0.02) were lower for Group 2 than Group 1 patients. The frequency of AV or VA block, impedance rise, and coagulum formation were comparable in two groups (all P > 0.05). During mean follow-up of 14 +/- 3 months, recurrence of the arrhythmia was seen in higher proportion of Group 1 than Group 2 patients (P = 0.036). Among the Group 2 patients, there were no significant differences between the three subgroups in terms of acute success rate, fluoroscopy time, risks of AV and VA block, pericardial effusion, and recurrence (All P > 0.05). Number of applications and RF pulse duration were lower in Sgp-2 and 3 compared to Sgp-1 (All P > 0.05). Impedance rise and coagulum formation were slightly higher in Sgp-3 compared to Sgp-1 and 2 but this difference did not reach statistical significance (All P > 0.05).

CONCLUSIONS

Compared to less than 55 degrees C, target temperatures > or = 55 degrees C during slow pathway ablation significantly reduces fluoroscopy time, RF pulse duration, number of RF applications, and recurrence of AVNRT without increase in risk of AV or VA block or coagulum formation.

Effect of first ventricular tachycardia cycle length on rate of ventricular arrhythmia recurrence in patients with implantable cardioverter-defibrillator

BACKGROUND

Some controversies exist regarding the proper treatment of hemodynamically tolerated and slow ventricular tachycardia (VT). We intended to assess the effect of cycle length of first VT episode on total ventricular arrhythmia burden in a cohort of patients with implantable cardioverter-defibrillator (ICD).

METHOD

Between March 2000 and March 2005, 195 patients underwent ICD implantation at our center. We included 158 patients (mean age, 58.3 +/- 12.9 years) with follow-up of 3 months or more in this study. Clinical, electrocardiographic, and ICD-stored data and electrograms were collected and analyzed.

RESULTS

During the follow-up of 16.7 +/- 10.6 months, 45 (28.5%) and 20 (12.6%) patients received first appropriate ICD therapy for VT and ventricular fibrillation, respectively. We divided the 45 patients with VT (based on the median value of VT cycle length) into 2 groups. Although patients with VT cycle length of less than 350 had higher total mean number of appropriate ICD therapy (25 vs 6.3, P = .023), during multivariate regression analysis, only left ventricular ejection fraction (EF) of less than 25% (P = .020) was correlated with total number of appropriate ICD therapy. First VT cycle length (P = .341), QRS duration (P = .126), age (P = .405), underlying heart disease (P = .310), indication of ICD implantation (P = .113), and sex (P = .886) have failed to predict the total burden of ventricular arrhythmia during the follow-up period.

CONCLUSION

After adjustment for left ventricular EF, initial VT cycle length per se did not confer a lower risk for subsequent ventricular arrhythmia recurrence compared with those with faster VT. Left ventricular EF of less than 25% was correlated with higher ventricular arrhythmia burden in patients with ICD.

Brugada-Type ECG Association with Unexpected Sick Sinus Syndrome

A 23-year-old man was referred to our center for atrial flutter ablation. After arrhythmia termination sinus node dysfunction unmasked and persisted after 2 months drug-free follow-up. Secondary causes such as antiarrhythmic drug consumption, organic heart disease, or electrolyte disturbance could be excluded. Standard 12-lead ECG showed a coved-type ST elevation in V1-V3, which increased after flecainide provocative test. Following an unexpected sick sinus syndrome, a Brugada-type ECG should be noted.

Prevalence and predictors of electrical storm in patients with implantable cardioverter-defibrillator

Identifying predictors of electrical storm in patients with implantable cardioverter-defibrillators (ICDs) could help identify those at risk and reduce the incidence of this emergency situation, which has a detrimental effect on mortality and morbidity in patients with ICDs. This retrospective study sought to determine the prevalence and predictors of electrical storm in patients with ICDs. One hundred sixty-two patients (126 men; mean age 58 +/- 13 years) who received ICDs from January 2001 to January 2005 were included in the study. Clinical, electrocardiographic, and ICD stored data and electrograms were collected and analyzed. Twenty-two patients (14%) developed electrical storm during a mean follow-up of 14.3 +/- 10 months. Using Cox multiple regression analysis, it was found that an ejection fraction <25% (p = 0.007), QRS width > or =120 ms (p = 0.002), and a lack of adjunctive angiotensin-converting enzyme inhibitor and beta-blocker therapy (both p < 0.001) were correlated with a greater probability of electrical storm. Adjunctive amiodarone and digoxin therapy, indication of ICD implantation, and age were not correlated with the occurrence of electrical storm during follow-up (all p = NS). In conclusion, electrical storm is not uncommon in patients with ICDs. Optimum medical therapy with beta blockers and angiotensin-converting enzyme inhibitors could reduce the occurrence of electrical storm, and this especially should be considered in those at greater risk for this complication (i.e., those with left ventricular ejection fractions <25% and QRS widths > or =120 ms).

Heart Rate Variability: Does it Change After RF Ablation of Reentrant Supraventricular Tachycardia?

BACKGROUND

Following RF ablation of reentrant supraventricular tachycardia, inappropriate sinus tachycardia may occur. Local parasympathetic denervation is a possible mechanism for these rhythm disturbances. The purpose of this study was to determine the incidence of sinus tachycardia and to determine the relation between endocardial lesions at different ablation sites and alterations in autonomic tone in several different groups of patients with supraventricular tachycardia, using techniques of heart rate variability analysis.

METHODS

The subjects of this study were 75 patients (48 women, 27 men) with a mean age of 39.99 (SD = 13.39). They underwent RF ablation of AV nodal slow pathways (40 cases), posteroseptal APs (23 cases), left lateral and right free wall APs (12 cases) because of symptomatic tachycardias. The mean sinus rate and time domain (standard deviation of RR intervals and root mean square of differences of adjacent RR intervals) and frequency domain (low frequency, high frequency and low frequency/high frequency ratio) analyses of heart rate variability were obtained by use of 24 hour Holter monitoring before and 1 month after ablation compared with pre-ablation values.

RESULTS

Analysis of 24 hour ambulatory Holter-monitors, performed 1 month after RF ablation, showed no significant changes in time and frequency domain parameters of heart rate variability in different groups. A significant increase in mean heart rate was noted after RF ablation at AV nodal slow pathway group and left freewall/right free wall accessory pathways group. Patients undergoing RF ablation of right or left posteroseptal accessory pathways had no significant increase in the mean heart rate.

CONCLUSION

In summary, an increase in sinus tachycardia may be initiated by RF ablation of atrioventricular reentrant tachycardia (AVNRT) and right free wall or left free wall accessory pathways. This finding shows that the modifications of heart rate are not directly related to the posteroseptal region or to the accessory pathways.

Inappropriate ICD discharge due to T-wave oversensing in a patient with the brugada syndrome

Accurate sensing is an essential requirement for appropriate functioning of implantable cardioverter-defibrillator (ICD). T-wave oversensing remains as an annoying problem in currently available ICD. The Brugada syndrome with its inherent dynamic variations in electrophysiologic phenomena may complicate ICD therapy. We report a patient with diagnosis of Brugada syndrome who presented with frequent inappropriate therapy due to intermittent T-wave oversensing. This problem could not be eliminated by device reprogramming and necessitated implantation of a new sense/pace lead.

Familial Atrial Standstill in Association with Dilated Cardiomyopathy

. Atrial standstill is an extremely uncommon arrhythmia that rarely appears to be familial and genetically determined. Atrial standstill has been associated with several conditions including, but not restricted to, congenital heart disease, valvular heart disease, conduction disturbances, Brugada syndrome, myocardial infarction, and amyloidosis. Only a few cases of familial clustering of atrial standstill have been reported so far. This report represents a family with atrial standstill associated with syncope, dilated cardiomyopathy, and sudden cardiac death.

Effect of conduction mode and location on electrophysiologic characteristics of accessory pathways

The conduction properties of accessory pathways (APs) are independent of location and conduction mode (except in patients with multiple, Mahaim, and slowly conducting APs). Patients with right-sided APs show higher rates of atrial fibrillation and longer arrhythmia cycle length due to slower anterograde conduction over the atrioventricular node during atrioventricular reentrant tachycardia.

Comparison of Presystolic Purkinje and Late Diastolic Potentials for Selection of Ablation Site in Idiopathic Verapamil Sensitive Left Ventricular Tachycardia

BACKGROUND

Idiopathic verapamil-sensitive left ventricular tachycardia (ILVT) is the most common form of idiopathic left ventricular tachycardia (VT). Different methods have been proposed for ablation of ILVT.

METHODS

Between June 2002 and February 2004, 15 patients (12 men; age 28 +/- 11 years, range 12 to 51) with ILVT underwent radiofrequency (RF) ablation at our center. We retrospectively assessed the significance of recording purkinje potential (PP) and late diastolic potential (DP) and its effect on selection of ablation target and number of RF application.

RESULTS

Sixteen VTs were observed. The clinical VT had either RBBB and left axis morphology (14 cases) or RBBB and right axis morphology (2 cases). The QRS duration during tachycardia was 124 +/- 12 ms and the tachycardia cycle length was 356 +/- 53 ms. DP and PP were recorded at the targeted area for RF ablation in 11 and 9 patients respectively. The PP-Q interval, DP-Q interval and DP width were 18 +/- 4, 53 +/- 18 and 14 +/- 8 ms, respectively. The number of RF application was 7.2 +/- 4.3. Fewer applications were needed in whom RF ablation was initially targeted to PP (with or without DP) recording site (10 patients, 4.7 +/- 1.8) compared to those targeted to DP recording site (5 patients, 12.2 +/- 3.3) ( P < 0.05).

CONCLUSION

Compared to DP alone, earliest PP (with or without concomitant DP) might be superior for selection of target site of RF ablation in patients with ILVT.