Pectus excavatum: uncommon electrical abnormalities caused by extrinsic right ventricular compression.

We report a case of pectus excavatum associated with ventricular tachycardia provoked by exercise in a 19-year-old man. Although this chest deformity has been associated with supraventricular dysrhythmias, documented ventricular tachycardia has only been reported once. Our patient's ventricular dysrhythmia was treated by surgical correction of his pectus excavatum only, and at 3 years follow-up he has had no recurrence of his ventricular tachycardia.

Catheter ablation of ventricular fibrillation storm in a long QT syndrome genotype carrier with normal QT interval.

Patients with long QT syndrome can sometimes present with a ventricular fibrillation (VF) storm. Catheter ablation of culprit premature ventricular complexes responsible for the triggering of the VF episodes may be required in rare cases of electrical storm that do not respond to conventional measures, and this can be life-saving. We describe a case of emergency catheter ablation in a young woman with a normal corrected QT interval, who presented with malignant VF storm for the first time. We also discuss the diagnostic and management challenges involved, as well as the value of genetic testing in refining the diagnosis.

Catheter ablation of ventricular fibrillation triggers and electrical storm.

Ventricular fibrillation (VF) and electrical storm remain challenging conditions to manage despite the availability of various treatment modalities. Insertion of an implantable cardioverter defibrillator (ICD) remains the gold standard method for lowering the risk of sudden cardiac death in patients deemed to be at greatest risk of ventricular arrhythmias. However, ICDs do not alter the underlying substrate responsible for the arrhythmic events and a significant proportion of patients with ICDs may experience VF storm which may be life threatening and difficult to control with medication. Catheter ablation (CA) of the triggers or abnormal electrical substrate responsible for VF storm is an important treatment option in rare cases. In this article, we present an overview of the current theories underlying the mechanisms of VF and discuss how the technique of CA may be used to treat the triggers of VF and electrical storm. We review the literature on outcomes in patients who have undergone CA for VF in a variety of different settings, including those with structural heart disease and structurally normal hearts (e.g. patients with inherited arrhythmogenic diseases and idiopathic VF) and discuss the future directions in this field.

Complete atrioventricular block complicating acute anterior myocardial infarction can be reversed with acute coronary angioplasty.

INTRODUCTION: A retrospective case series of acute anterior myocardial infarction (MI) patients complicated by complete atrioventricular block (AVB) treated with acute percutaneous transluminal coronary angioplasty (PTCA). CLINICAL PICTURE: Eight patients with anterior MI and complete AVB underwent acute PTCA between 2000 and 2005. Mean onset of complete AVB was 16.6 +/- 16.9 hours from chest pain onset. TREATMENT: All patients underwent successful PTCA to the left anterior descending artery. OUTCOME: Complete AVB resolved with PTCA in 88%; mean time of resolution was 89 +/- 144 minutes after revascularisation. One patient had permanent pacemaker implanted at Day 12 after developing an 8-second ventricular standstill during hospitalisation but not pacing-dependent on follow-up. The rhythm on discharge for the other surviving patients was normal sinus rhythm. CONCLUSION: This case series suggests that complete AVB complicating anterior MI is reversible with acute PTCA and survivors are not at increased risk of recurrent AVB. Nevertheless, this condition is associated with extensive myocardial damage and high mortality during the acute hospitalisation was not improved with correction of AVB with temporary pacing.

Outcomes of long-standing persistent atrial fibrillation ablation: a systematic review.

BACKGROUND: Ablation of long-standing persistent atrial fibrillation (AF) is highly variable, with differing techniques and outcomes. OBJECTIVE: The purpose of this study was to undertake a systematic review of the literature with regard to the impact of ablation technique on the outcomes of long-standing persistent AF ablation. METHODS: A systematic search of the contemporary English scientific literature (from January 1, 1990 to June 1, 2009) in the PubMed database identified 32 studies on persistent/long-standing persistent or long-standing persistent AF ablation (including four randomized controlled trials). Data on single-procedure, drug-free success, multiple procedure success, and pharmaceutically assisted success at longest follow-up were collated. RESULTS: Four studies performed pulmonary vein isolation alone (21%-22% success). Four studies performed pulmonary vein antrum ablation with isolation (PVAI; n = 2; 38%-40% success) or without confirmed isolation (PVA; n = 2; 37%-56% success). Ten studies performed linear ablation in addition to PVA (n = 5; 11%-74% success) or PVAI (n = 5; 38%-57% success). Three studies performed posterior wall box isolation (n = 3; 44%-50% success). Five studies performed complex fractionated atrial electrogram ablation (n = 5; 24%-63% success). Six studies performed complex fractionated atrial electrogram ablation as an adjunct to PVA (n = 2; 50%-51% success), PVAI (n = 3; 36%-61% success), or PVAI and linear (n = 1; 68% success) ablation. Five studies performed the stepwise ablation approach (38%-62% success). CONCLUSION: The variation in success within and between techniques suggests that the optimal ablation technique for long-standing persistent AF is unclear. Nevertheless, long-standing persistent AF can be effectively treated with a composite of extensive index catheter ablation, repeat procedures, and/or pharmaceuticals.

Comprehensive mutation scanning of KCNQ1 in 111 Han Chinese patients with lone atrial fibrillation.

OBJECTIVE: To determine the extent to which genetic variation in the potassium channel gene KCNQ1 causes atrial fibrillation (AF). DESIGN: Case-control study. SETTING: National University Hospital, Singapore. PATIENTS: Han Chinese patients (n=111) with lone AF (onset <60 years and lacking risk factors) and 265 Han Chinese controls. INTERVENTIONS: Blood draw, 12-lead electrocardiogram and transthoracic echocardiogram were performed on patients with AF at enrolment. MAIN OUTCOME MEASURES: DNA sequence variants in the coding region and exon-intron boundaries of KCNQ1 as detected by direct sequencing. RESULTS: Four previously reported coding variants were identified: I145I, S546S, P448R and G643S. An additional 19 non-coding variants were identified, nine of which are newly reported. None were predicted to create a cryptic splicing site. The allele frequencies of the two non-synonymous variants did not differ significantly in the AF cases compared with 265 Han Chinese controls (P448R: 10.8% in cases vs 8.6% in controls, p=0.41; G643S: 1.4% in cases vs 0.8% in controls, p=0.43). CONCLUSIONS: Comprehensive mutation scanning of KCNQ1 did not identify novel pathogenic mutations or risk-conferring polymorphisms. As in Caucasians, genetic variation in KCNQ1 is not a common cause of AF in Han Chinese. Routine genetic testing of KCNQ1 for AF is, therefore, not warranted.

Implantation of lumenless pacing leads at the inter-atrial septum and right ventricular outflow tract with deflectable catheter-sheath.

Current permanent right ventricular and right atrial endocardial pacing leads are implanted utilizing a central lumen stylet. Right ventricular apex pacing initiates an abnormal asynchronous electrical activation pattern, which results in asynchronous ventricular contraction and relaxation. When pacing from right atrial appendage, the conduction time between two atria will be prolonged, which results in heterogeneity for both depolarization and repolarization. Six patients with Class I indication for permanent pacing were implanted with either single chamber or dual chamber pacemaker. The SelectSecure 3830 4-French (Fr) lumenless lead and the SelectSite C304 8.5-Fr steerable catheter-sheath (Medtronic Inc., USA) were used. Pre-selected pacing sites included inter-atrial septum and right ventricular outflow tract, which were defined by ECG and fluoroscopic criteria. All the implanting procedures were successful without complication. Testing results (mean atrial pacing threshold: 0.87 V; mean P wave amplitude: 2.28 mV; mean ventricular pacing threshold: 0.53V; mean R wave amplitude: 8.75 mV) were satisfactory. It is concluded that implantation of a 4-Fr lumenless pacing lead by using a streerable catheter-sheath to achieve inter-atrial septum or right ventricular outflow tract pacing is safe and feasible.

Complete isolation of the pulmonary veins and posterior left atrium in chronic atrial fibrillation. Long-term clinical outcome.

AIMS: To evaluate the contribution of the posterior left atrium (LA) to chronic atrial fibrillation (AF). METHODS AND RESULTS: Twenty-seven patients with chronic-AF were studied. After pulmonary vein (PV) isolation, the posterior-LA was isolated by ablation joining the right- and left-PVs using an irrigated-tip catheter. Isolation was demonstrated by absent/dissociated posterior-LA activity and the inability to pace the region. Ablation impact was determined by the effect on cycle length (CL) and AF termination. Posterior-LA isolation was achieved using 35 +/- 12 min of radiofrequency with total fluoroscopic and procedural durations of 64 +/- 16 and 199 +/- 46 min, resulting in abolition of electrograms (n = 21) or autonomous activity (n = 6; CL 820 +/- 343 ms). AFCL increased from 156 +/- 28 ms to 162 +/- 27 ms with PV-isolation and to 175 +/- 32 ms by posterior-LA exclusion (P < 0.0001). AF persisted in all after PV-isolation and terminated in 5 (19%) during posterior-LA-isolation. After 10 +/- 6 months, 12 patients developed atrial tachycardia (four) or AF (eight); four underwent repeat posterior-LA-isolation, while the others required additional ablation/antiarrhythmics. After 21 +/- 5 months, 17 (63%) were in sinus rhythm following posterior-LA-isolation. CONCLUSION: This study demonstrates the feasibility of complete posterior-LA exclusion by catheter ablation. This strategy results in maintenance of sinus rhythm in 63% at 2 years follow-up.

Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST-segment elevation, short QT intervals, and sudden cardiac death.

BACKGROUND: Cardiac ion channelopathies are responsible for an ever-increasing number and diversity of familial cardiac arrhythmia syndromes. We describe a new clinical entity that consists of an ST-segment elevation in the right precordial ECG leads, a shorter-than-normal QT interval, and a history of sudden cardiac death. METHODS AND RESULTS: Eighty-two consecutive probands with Brugada syndrome were screened for ion channel gene mutations with direct sequencing. Site-directed mutagenesis was performed, and CHO-K1 cells were cotransfected with cDNAs encoding wild-type or mutant CACNB2b (Ca(v beta2b)), CACNA2D1 (Ca(v alpha2delta1)), and CACNA1C tagged with enhanced yellow fluorescent protein (Ca(v)1.2). Whole-cell patch-clamp studies were performed after 48 to 72 hours. Three probands displaying ST-segment elevation and corrected QT intervals < or = 360 ms had mutations in genes encoding the cardiac L-type calcium channel. Corrected QT ranged from 330 to 370 ms among probands and clinically affected family members. Rate adaptation of QT interval was reduced. Quinidine normalized the QT interval and prevented stimulation-induced ventricular tachycardia. Genetic and heterologous expression studies revealed loss-of-function missense mutations in CACNA1C (A39V and G490R) and CACNB2 (S481L) encoding the alpha1- and beta2b-subunits of the L-type calcium channel. Confocal microscopy revealed a defect in trafficking of A39V Ca(v)1.2 channels but normal trafficking of channels containing G490R Ca(v)1.2 or S481L Ca(v beta2b)-subunits. CONCLUSIONS: This is the first report of loss-of-function mutations in genes encoding the cardiac L-type calcium channel to be associated with a familial sudden cardiac death syndrome in which a Brugada syndrome phenotype is combined with shorter-than-normal QT intervals.

Impact of left ventricular epicardial and biventricular pacing on ventricular repolarization in normal-heart individuals and patients with congestive heart failure.

AIMS: Malignant ventricular arrhythmias can arise in a subset of congestive heart failure (CHF) patients after they undergo cardiac resynchronization therapy (CRT), thus counteracting the haemodynamic benefits typically associated with biventricular pacing. This study seeks to assess whether alteration of the ventricular transmural repolarization and conduction due to reversal of the depolarization sequence during epicardial or biventricular pacing facilitate the development of ventricular arrhythmias. METHODS AND RESULTS: ECGs and monophasic action potential (MAP) were recorded during programmed stimulation from right ventricle (RV) endocardium (RV-Endo), left ventricle (LV) epicardium (LV-Epi), or both (biventricular, Bi-V) in 15 individuals without structural heart diseases. In patients with severe CHF and CRT (n=21), ECGs were collected during RV-Endo, LV-Epi, and Bi-V pacing. MAP duration on intracardiac electrogram, the QT, JT, and T(peak)-T(end) intervals on ECGs at different pacing sites were measured and compared. In subjects with or without structural heart disease, compared with RV-Endo pacing, LV-Epi and Bi-V pacing resulted in a longer JT (341.78+/-61.97 ms with LV-Epi, 325.86+/-59.69 ms with Bi-V vs. 286.14+/-38.68 ms with RV-Endo in CHF individuals, P<0.0001) or T(peak)-T(end) interval (121.55+/-19.88 ms with LV-Epi, 117.71+/-42.63 ms with Bi-V vs. 102.28+/-12.62 ms with RV-Endo in normal-heart subjects, P<0.0001; 199.70+/-62.44 ms with LV-Epi, 184.89+/-74.08 ms with Bi-V vs. 146.41+/-31.06 ms with RV-Endo in CHF patients, P<0.0001), in addition to prolonged myocardial repolarization time and delayed endocardial activation. During follow-up, sudden death and arrhythmia storm occurred in two CHF patients after CRT. CONCLUSION: Epicardial and biventricular pacing prolong the time and increase the dispersion of myocardial repolarization and delay the transmural conduction. All of these should be considered as potential arrhythmogenic factors in CHF patients who receive CRT.

Frequency mapping of the pulmonary veins in paroxysmal versus permanent atrial fibrillation.

INTRODUCTION: The pulmonary veins (PVs) are a dominant source of triggers initiating atrial fibrillation (AF). While recent evidence implicates these structures in the maintenance of paroxysmal AF, their role in permanent AF is not known. The current study aims to compare the contribution of PV activity to the maintenance of paroxysmal and permanent AF. METHODS AND RESULTS: Thirty-four patients with paroxysmal AF (n = 20) or permanent AF (n = 14) undergoing ablation were studied. Prior to ablation, 32 seconds of electrograms were acquired from each PV and the coronary sinus (CS). The frequency of activity of each PV and CS was defined as the highest amplitude frequency on spectral analysis. The effects of ablation on the AF cycle length (AFCL) and frequency and on AF termination were determined. Significant differences were observed between paroxysmal and permanent AF. Paroxysmal AF demonstrates higher frequency PV activity (11.0 +/- 3.1 vs 8.8 +/- 3.0 Hz; P = 0.0003) but lower CS frequency (5.8 +/- 1.2 vs 6.9 +/- 1.4 Hz; P = 0.01) and longer AFCL (182 +/- 17 vs 158 +/- 21 msec; P = 0.002), resulting in greater PV to atrial frequency gradient (7.2 +/- 2.2 vs 4.2 +/- 2.9 Hz; P = 0.006). PV isolation in paroxysmal AF resulted in a greater decrease in atrial frequency (1.0 +/- 0.7 vs -0.05 +/- 0.4 Hz; P < 0.0001), greater prolongation of the AFCL (49 +/- 35 vs 5 +/- 6 msec; P < 0.0001), and more frequent AF termination (11/20 vs 0/14; P = 0.0007) compared to permanent AF. CONCLUSION: Paroxysmal AF is associated with higher frequency PV activity and lesser CS frequency compared to permanent AF. Isolation of the PVs had a greater impact on the fibrillatory process in paroxysmal AF compared to permanent AF, suggesting that while the PVs have a role in maintaining paroxysmal AF, these structures independently contribute less to the maintenance of permanent AF.

Characterization of conduction recovery across left atrial linear lesions in patients with paroxysmal and persistent atrial fibrillation.

BACKGROUND: Left atrial (LA) linear lesions are effective in substrate modification for atrial fibrillation (AF). However, achievement of complete conduction block remains challenging and conduction recovery is commonly observed. The aim of the study was to investigate the localization of gap sites of recovered LA linear lesions. METHODS AND RESULTS: Forty-eight patients with paroxysmal (n = 26) and persistent/permanent (n = 22) AF underwent repeat ablation after pulmonary vein (PV) isolation and LA linear ablation at the LA roof and/or mitral isthmus due to recurrences of AF or flutter. In 35 patients, conduction through the mitral isthmus line (ML) had recovered whereas roof-line recovery was observed in 30 patients. The gaps within the ML were distributed to the junction between left inferior PV and left atrial appendage in 66%, the middle part of the ML in 20%, and in 8% to the endocardial aspect of the ML while only 6% of lines showed an epicardial site of recovery. The RL predominantly recovered close to the right superior PV (54%) and less frequently in the mid roof or close to the left PV (both 23%). Reablation of lines required significantly shorter RF durations (ML: 7.24 +/- 5.55 minutes vs 24.08 +/- 9.38 minutes, RL: 4.24 +/- 2.34 minutes vs 11.54 +/- 6.49 minutes; P = 0.0001). Patients with persistent/permanent AF demonstrated a significantly longer conduction delay circumventing the complete lines than patients with paroxysmal AF (228 +/- 77 ms vs 164 +/- 36 ms, P = 0.001). CONCLUSIONS: Gaps in recovered LA lines were predominantly located close to the PVs where catheter stability is often difficult to achieve. Shorter RF durations are required for reablation of recovered linear lesions. Conduction times around complete LA lines are significantly longer in patients with persistent/permanent AF as compared to patients with paroxysmal AF.

Fibrillating areas isolated within the left atrium after radiofrequency linear catheter ablation.

INTRODUCTION: Nonpulmonary vein sources have been implicated as potential drivers of atrial fibrillation (AF). This observational study describes regions of fibrillating atrial tissue isolated inadvertently from the left atrium (LA) following linear catheter ablation for AF. METHODS AND RESULTS: We report four patients with persistent/permanent AF who underwent pulmonary vein isolation with additional linear lesions and who presented with recurrent AF (mean AF cycle length [AFCL] 175-270 ms). Further catheter ablation resulted in the inadvertent electrical isolation of significant areas of the LA in which AF persisted at the same AFCL as was measured prior to disconnection, despite the restoration of sinus rhythm (SR) in all other left and right atrial areas, strongly suggesting that these islands were driving the remaining atria into fibrillation. The disconnected areas were located in the lateral LA, including the left atrial appendage (LAA) in three patients (limited to the LAA in one) and in the posterior LA in one patient. These isolated fibrillating regions represented 15-24% of the global LA surface, as estimated by electroanatomic mapping. CONCLUSION: Fibrillation can be maintained within electrically isolated regions of the LA following catheter ablation of AF, demonstrating the importance of atrial drivers in the maintenance of AF. Further mapping of these drivers is needed to characterize their mechanism and thereby allow for a more specific ablation strategy.

Phrenic nerve injury after atrial fibrillation catheter ablation: characterization and outcome in a multicenter study.

OBJECTIVES: The purpose of this study was to characterize the occurrence of phrenic nerve injury (PNI) and its outcome after radiofrequency (RF) ablation of atrial fibrillation (AF). BACKGROUND: It is recognized that extra-myocardial damage may develop owing to penetration of ablative energy. METHODS: Between 1997 and 2004, 3,755 consecutive patients underwent AF ablation at five centers. Among them, 18 patients (0.48%; 9 male, 54 +/- 10 years) had PNI (16 right, 2 left). The procedure consisted of pulmonary vein (PV) isolation in 15 patients and anatomic circumferential ablation in 3 patients, with additional left atrial lesions (n = 11) and/or superior vena cava (SVC) disconnection (n = 4). RESULTS: Right PNI occurred during ablation of right superior PV (n = 12) or SVC disconnection (n = 3). Left PNI occurred during ablation at the left atrial appendage. Immediate features were dyspnea, cough, hiccup, and/or sudden diaphragmatic elevation in 9, and in the remaining the diagnosis was made after ablation owing to dyspnea (n = 7) or on routine radiographic evaluation (n = 2). Four patients (22%) were asymptomatic. Complete recovery occurred in 12 patients (66%). Recovery occurred within 24 h in the two patients with left PNI and in one patient with right PNI occurring with SVC disconnection. In the other nine patients, right PNI recovery occurred after 4 +/- 5 months (1 to 12 months) with respiratory rehabilitation. After a mean follow-up of 36 +/- 33 months, six patients have persistent PNI (three with partial and three with no recovery). CONCLUSIONS: In this multicenter experience, PNI was a rare complication (0.48%) of AF ablation. Ablation of the right superior PV, SVC, and left atrial appendage were associated with PNI. Complete (66%) or partial (17%) recovery was observed in the majority.

Flutter localized to the anterior left atrium after catheter ablation of atrial fibrillation.

INTRODUCTION: Organized atrial arrhythmias following atrial fibrillation (AF) ablation are typically due to recovered pulmonary vein (PV) conduction or reentry at incomplete ablation lines. We describe the role of nonablated anterior left atrium (LA) in arrhythmias observed after AF ablation. METHODS: A total of 275 consecutive patients with paroxysmal (n = 200) or chronic (n = 75) AF had PV isolation with/without additional linear ablation at the mitral isthmus (n = 106), LA roof (n = 23), or both (n = 88). Organized arrhythmias occurring after ablation were evaluated utilizing activation and entrainment mapping. RESULTS: Fourteen patients (11 female, 65 +/- 13 years, 10 chronic AF, 10 structural heart disease) demonstrated tachycardia localized to the anterior LA, an area not targeted by prior ablation. Eight had ECG features during sinus rhythm suggestive of impaired anterior LA conduction at baseline. These arrhythmias demonstrated a distinctive ECG flutter morphology in 7 of 10 (70%) with discrete -/+ or +/-/+ aspect in inferior leads. Mapping the anterior LA revealed electrograms spanning the entire tachycardia cycle length (325 +/- 125 msec). Entrainment was possible in all with a postpacing interval exceeding the tachycardia cycle length by 9 +/- 10 msec. Electroanatomic mapping in 6 demonstrated small reentrant circuits rotating clockwise in 4 and counterclockwise in 2. Low-amplitude, fractionated mid-diastolic potentials with long duration (200 +/- 80 msec) occupying 63 +/- 22% of the cycle length were targeted for ablation resulting in termination and subsequent noninducibility. CONCLUSION: Organized arrhythmias occurring after AF ablation can be due to reentrant circuits localized to the anterior LA, predominantly in females with chronic AF, structural heart disease, and abnormal atrial conduction. They are characterized by a distinctive surface ECG and highly responsive to RF ablation at the slow conduction area.

Shortening of fibrillatory cycle length in the pulmonary vein during vagal excitation.

OBJECTIVES: The goal of the present prospective study is to evaluate the impact of vagal excitation on ongoing atrial fibrillation (AF) during pulmonary vein (PV) isolation. BACKGROUND: The role of vagal tone in maintenance of AF is controversial in humans. METHODS: Twenty-five patients (18 with paroxysmal AF, 7 with chronic AF) were selected by occurrence of vagal excitation during AF (atrioventricular [AV] block: R-R interval >3 s) produced by PV isolation. Fibrillatory cycle length (CL) in the targeted PV and coronary sinus (CS) were determined before, during, and after vagal excitation. The CL was available at PV ostium during vagal excitation in 11 patients. RESULTS: Forty-eight episodes of vagal excitation were observed. During vagal excitation, CL abruptly decreased both in CS and PV (CS, 164 +/- 20 ms to 155 +/- 23 ms, p < 0.0001; PV, 160 +/- 22 ms to 143 +/- 28 ms, p < 0.0001), and both returned to the baseline value with resumption of AV conduction. The decrease in PVCL occurred earlier (2.5 +/- 1.5 s vs. 4.0 +/- 2.6 s, p < 0.01) and was of greater magnitude than that in CSCL (16 +/- 16 ms vs. 8 +/- 9 ms, p < 0.01). A sequential gradient of CL was observed from PV to PV ostium and CS during vagal excitation (138 +/- 29 ms, 149 +/- 24 ms, and 159 +/- 26 ms, respectively). The decrease in CL was significantly greater in paroxysmal than in chronic AF (CS, 11 +/- 9 ms vs. 5 +/- 7 ms, p < 0.05; PV, 23 +/- 25 ms vs. 8 +/- 14 ms, p < 0.05). CONCLUSIONS: Vagal excitation is associated with shortening of fibrillatory CL. This occurs earlier in PV with a sequential gradient to PV ostium and CS, suggesting that vagal excitation enhances a driving role of PV.