Congenital Long QT Syndrome: A Clinician's Guide

Congenital long QT syndrome (LQTS) is a familial cardiac ion channelopathy first described over sixty years ago. It is characterised by prolonged ventricular repolarization (long QT on ECG), ventricular arrhythmias and associated syncope or sudden cardiac death. As the most closely studied cardiac channelopathy, over the decades we have gained a deep appreciation of the complex genetic model of LQTS. Variability in genetic expression and incomplete penetrance leads to a heterogenous phenotype that can be challenging to clinically classify. In recent times, progress has been made in diagnostic method, risk stratification and treatment options. This review has been written as a guide for the general cardiologist to understand the basic pathophysiology, diagnosis, and management priorities for the most encountered LQTS subtypes: LQT1, LQT2 and LQT3. This article is protected by copyright. All rights reserved.

Prevention of Pathological Atrial Remodeling and Atrial Fibrillation: JACC State-of-the-Art Review

Atrial enlargement in response to pathological stimuli (e.g., hypertension, mitral valve disease) and physiological stimuli (exercise, pregnancy) can be comparable in magnitude, but the diseased enlarged atria is associated with complications such as atrial fibrillation (AF), whereas physiological atrial enlargement is not. Pathological atrial enlargement and AF is also observed in a small percentage of athletes undergoing extreme/intense endurance sport and pregnant women with preeclampsia. Differences between physiological and pathological atrial enlargement and underlying mechanisms are poorly understood. This review describes human and animal studies characterizing atrial enlargement under physiological and pathological conditions and highlights key knowledge gaps and clinical challenges, including: 1) the limited ability of atria to reverse remodel; and 2) distinguishing physiological and pathological enlargement via imaging/biomarkers. Finally, this review discusses how targeting distinct molecular mechanisms underlying physiological and pathological atrial enlargement could provide new therapeutic and diagnostic strategies for preventing or reversing atrial enlargement and AF.

Predictors of long-term success after catheter ablation of premature ventricular complexes

INTRODUCTION

Some patients have late recurrence after acutely successful radiofrequency catheter ablation (RFCA) of premature ventricular complexes (PVCs). The aim of this study was to evaluate predictors of long-term success following acutely successful PVC RFCA.

METHODS

We identified consecutive patients at our institution with frequent PVCs undergoing RFCA and reviewed procedural data and medical records. Acute success was defined as elimination of targeted PVCs for at least 30-min after RFCA. Long-term success was defined as absence of targeted PVCs during all follow-up visits and PVC-burden <5% on follow-up monitoring.

RESULTS

Among 241 patients (mean age 57 ± 15 years, 58% male), 161 (66.8%) had long-term success with median follow-up of 17.7 (IQR, 12.2-29.8) months. Unadjusted predictors of late PVC recurrence were increasing age, diabetes mellitus and alcohol use, while female-sex, shorter ablation-time, right ventricular PVC-origin, single PVC morphology, and earliest bipolar activation ≥24 ms pre-QRS were predictors of long-term success. In multivariate-analysis, female-sex, single-PVC morphology and earliest-onset of PVC ≥ 24 ms pre-QRS were independent predictors for long-term success. The positive-predictive value of earliest-bipolar onset of PVC ≥ 24 ms pre-QRS for long-term success was 0.77 (p < .001). Negative-predictive value of PVC < 15 ms pre-QRS for long-term success was 0.86 (p = .003), suggesting that RFCA when the bipolar electrogram preceded QRS by <15 ms was unlikely to result in long-term success.

CONCLUSIONS

Female-sex, single-PVC morphology, and earliest-onset of bipolar electrogram ≥24 ms pre-QRS were multivariable predictors of long-term success in patients with PVCs undergoing RFCA. RFCA at sites with local onset <15 ms pre-QRS are unlikely to be successful.

A prospective evaluation of the impact of individual RF applications for slow pathway ablation for AVNRT: Markers of acute success

BACKGROUND

Catheter ablation is highly effective for atrioventricular nodal re-entrant tachycardia (AVNRT). Generally junctional rhythm (JR) is an accepted requirement for successful ablation however there is a lack of detailed prospective studies to determine the characteristics of JR and the impact on slow pathway conduction.

METHODS

Multicentre prospective observational study evaluating the impact of individual radiofrequency (RF) applications in typical AVNRT (slow/fast). Characteristics of JR during ablation were documented and detailed testing was performed after every RF application to determine outcome. Procedural success was defined as ≤1 AV nodal echo.

RESULTS

Sixty-seven patients were included (mean age 53 ± 18years, 57% female and a history of SVT 2.9 ± 4.7 years). RF (50w, 60°) ablation for AVNRT was applied in 301 locations with JR in 178 (59%). Successful slow pathway modification was achieved in 66 (99%) patients with slow pathway block in 30 (46%). Success was associated with JR in all patients. Success was achieved in six patients with RF < 10 s. There was no significant difference in the CL of JR during RF between effective (587 ± 150 ms) versus ineffective (611 ± 193 ms, p = .4) applications. Inadvertent junctional beat-atrial (JA) block with immediate termination of RF was observed in 19 (28%) patients with AVNRT no longer inducible in 14 (74%). Freedom from SVT was achieved in 66 (99%) patients at a mean follow up of 15 ± 6 months.

CONCLUSION

In this prospective study, JR was required during RF for acute success in AVNRT. Cycle length of JR during RF was not predictive of success. Although unintended JA block during faster JR was associated with slow pathway block, this is a precursor to fast pathway block and should not be intentionally targeted.

A prospective STudy using invAsive haemodynamic measurements foLLowing catheter ablation for AF and early HFpEF: STALL AF-HFpEF

AIMS

The impact of atrial fibrillation (AF) ablation in early heart failure with preserved ejection fraction (HFpEF) is unknown. Our aim was to determine the impact of AF ablation on symptoms and exercise haemodynamic parameters of early HFpEF.

METHODS AND RESULTS

Symptomatic AF patients referred for index AF ablation with ejection fraction ≥50% underwent baseline quality of life questionnaires, echocardiography, cardiac magnetic resonance imaging, exercise right heart catheterisation (exRHC), and brain natriuretic peptide (BNP) testing. HFpEF was defined by resting pulmonary capillary wedge pressure (PCWP) ≥15 mmHg or peak exercise PCWP ≥25 mmHg. Patients with HFpEF were offered AF ablation and follow-up exRHC ≥6 months post-ablation. Of 54 patients undergoing baseline evaluation, 35 (65%) had HFpEF identified by exRHC. HFpEF patients were older (64 ± 10 vs. 54 ± 13 years, P < 0.01), and more frequently female (54% vs. 16%, P < 0.01), hypertensive (63% vs. 16%, P < 0.001), and suffering persistent AF (66% vs. 11%, P < 0.001), compared to those without HFpEF. Twenty HFpEF patients underwent AF ablation and follow-up exRHC 12 ± 6 months post-ablation. Nine (45%) patients no longer fulfilled exRHC criteria for HFpEF at follow-up. Patients remaining arrhythmia free (n = 9, 45%) showed significant improvements in peak exercise PCWP (29 ± 4 to 23 ± 2 mmHg, P < 0.01) and Minnesota Living with Heart Failure (MLHF) score (55 ± 30 to 22 ± 30, P < 0.01) while the remainder did not (PCWP 31 ± 5 to 30.0 ± 4 mmHg, P = NS; MLHF score 55 ± 23 to 25 ± 20, P = NS).

CONCLUSION

Heart failure with preserved ejection fraction frequently coexists in patients with symptomatic AF and preserved ejection fraction. Restoration and maintenance of sinus rhythm in patients with comorbid AF and HFpEF improves haemodynamic parameters, BNP and symptoms associated with HFpEF.

Acute electrical, autonomic and structural effects of binge drinking: Insights into the 'holiday heart syndrome'

BACKGROUND

Binge drinking is a common atrial fibrillation (AF) trigger, however the mechanisms are poorly understood.

OBJECTIVE

To investigate the effects of alcohol intoxication and hangover with rhythm monitoring and cardiac MRI.

METHODS

Patients underwent serial cardiac MRI pre- and post-binge with continuous Holter monitoring. Time periods analyzed: baseline (24 h pre-binge), consumption, hangover (0- 24 h post-consumption) and post-hangover (24-48 h post-consumption).

RESULTS

50 patients (age 49 ± 15 years, 40% paroxysmal AF) completed the study (intake 8.4 ± 3.1 standard drinks). Mean heart rate increased from 72 ± 10 to 80 ± 13 beats per minute (bpm) during consumption (p < 0.001). The hangover period was characterised by higher daily atrial ectopic count (50, IQR 10-132 vs baseline 43, IQR 10-113; p = 0.04) and reduced heart rate variability (SDNN 55 ms, IQR 40-65 versus 62 ms, IQR 51-66; p = 0.007). There was evidence of heightened parasympathetic activity post-hangover with heart rate slowing (mean HR 54 ± 6 bpm; p = 0.03) and increased activity in the High frequency band when separating the complex heart rate variability waveform into its component rhythms (291 ms², 97-538 versus baseline 237 ms², IQR 104-332; p = 0.04). Three patients developed AF 11, 29 and 34 h post-binge. Cardiac MRI (2.7 ± 0.7 days post-binge) demonstrated a decrease in left atrial (LA) emptying fraction (57.9 ± 8.5 to 53.5 ± 6.7%; p = 0.003) but no change in LA volume, left ventricular ejection fraction or markers of ventricular inflammation.

CONCLUSION

Binge drinking is associated with sympathetic activation followed by a 'rebound' parasympathetic response and atrial mechanical dysfunction which may explain the propensity and temporal association between binge drinking and AF.

Complex Re-Entrant Arrhythmias Involving the His-Purkinje System: A Structured Approach to Diagnosis and Management

OBJECTIVES

This study sought to characterize the presentations, electrophysiological features and diagnostic maneuvers for a series of unique arrhythmias involving the HPS.

BACKGROUND

By virtue of its unique anatomy and ion channel composition, the His-Purkinje system (HPS) is prone to a variety of arrhythmic perturbations.

METHODS

The authors present a collaborative multicenter case series of 6 patients with HPS-related arrhythmias. All patients underwent electrophysiological studies using standard multipolar catheters.

RESULTS

In 3 patients, both typical and reverse bundle branch re-entry were seen, with 1 patient demonstrating "figure of 8" re-entry likely involving the septal fascicle. One patient presented with systolic dysfunction associated with a high premature ventricular complex burden, with the mechanism being bundle-to-bundle re-entrant beats masquerading as dual response to a single sinus impulse. Two patients were diagnosed with interfascicular re-entry. Diagnosis was aided by careful assessment of HV interval in sinus rhythm and ventricular tachycardia, multipolar catheters to assess the activation sequence of the His-right bundle branch, and fascicles and entrainment of different components of the HPS. Cure of the arrhythmia was achieved by ablation of the right bundle branch block in 3 patients, the left septal fascicle in 2 patients, and the left posterior fascicle in 1 patient.

CONCLUSIONS

Proper diagnosis of re-entrant arrhythmias involving the HPS may prove challenging. We emphasize a structured approach for diagnosis and effective therapy.

Electrophysiologic approach to diagnosis and ablation of patients with permanent junctional reciprocating tachycardia associated with complex anatomy and/or physiology

INTRODUCTION

Permanent junctional reciprocating tachycardia (PJRT) is a rare supraventricular tachycardia (SVT), typically involving a single decremental posteroseptal accessory pathway (AP).

METHODS

Four patients with long RP SVT underwent electrophysiology (EP) study and ablation. The cases were reviewed.

RESULTS

Case 1 recurred despite 3 prior ablations at the site of earliest retrograde atrial activation during orthodromic reciprocating tachycardia (ORT). Mapping during a repeat EP study demonstrated a prepotential in the coronary sinus (CS). Ablation over the earliest atrial activation in the CS resulted in dissociation of the potential from the atrium during sinus rhythm. The potential was traced back to the CS os and ablated. Case 2 underwent successful ablation at 6 o'clock on the mitral annulus (MA). ORT recurred and successful ablation was performed at 1 o'clock on the MA. Case 3 had tachycardia with variation in both V-A and A-H intervals which precluded the use of usual maneuvers so we used simultaneous atrial and ventricular pacing and introduced a premature atrial contraction with a closely coupled premature ventricular contraction. Case 4 had had two prior atrial fibrillation ablations with continued SVT over a decremental atrioventricular bypass tract that was successfully ablated at 5 o'clock on the tricuspid annulus. A second SVT consistent with a concealed nodoventricular pathway was successfully ablated at the right inferior extension of the AV nodal slow pathway.

CONCLUSION

We describe challenging cases of PJRT by virtue of complex anatomy, diagnostic features, and multiple arrhythmia mechanisms.

Genetic Susceptibility to Atrial Fibrillation Is Associated With Atrial Electrical Remodeling and Adverse Post-Ablation Outcome

OBJECTIVES

This study sought to assess the atrial electrophysiological properties and post-ablation outcomes in patients with atrial fibrillation (AF) with and without the rs2200733 single nucleotide variant.

BACKGROUND

The phenotype associated with chromosome 4q25 of the AF-susceptibility locus remains unknown.

METHODS

In this study, 102 consecutive patients (ages 61 ± 9 years, 64% male) with paroxysmal or persistent AF were prospectively recruited prior to ablation. Patients were genotyped for rs2200733 and high-density left atrial (LA) electroanatomic maps were created using a multipolar catheter during distal coronary sinus (CS) pacing at 600 ms. Voltage, conduction velocity (CV), CV heterogeneity, and fractionated signals of 6 LA segments were determined. Arrhythmia recurrence was assessed by continuous device (51%) and Holter monitoring.

RESULTS

Overall, 41 patients (40%) were single nucleotide variant carriers (38 heterozygous, 3 homozygous). A mean of 2,239 ± 852 points per patient were collected. Carriers had relatively increased CV heterogeneity (45.7 ± 7.5% vs. 35.9 ± 2.3%; p < 0.001), complex signals (9.4 ± 2.9% vs 6.0 ± 1.2%; p = 0.008), regional LA slowing, or conduction block (31.7 ± 8.2% vs. 17.9 ± 1.9%; p = 0.013) particularly in the posterior and lateral walls. There were no differences in CV, voltage, atrial refractoriness, or sinus node function. At follow-up (median: 27 months; range 19 to 31 months), carriers had lower arrhythmia-free survival (51% vs. 80%; p = 0.003). On multivariable analysis, carrier status was independently associated with CV heterogeneity (p = 0.001), complex signals (p = 0.002), and arrhythmia recurrence (p = 0.019).

CONCLUSIONS

These data provide the first evidence that the rs2200733-tagged haplotype alters LA electrical remodeling and is a determinant of long-term outcome following AF ablation. The molecular mechanisms underpinning these changes warrant further investigation.

Reduction in mortality from implantable cardioverter-defibrillators in non-ischaemic cardiomyopathy patients is dependent on the presence of left ventricular scar

Aims

In patients with non-ischaemic cardiomyopathy (NICM), the mortality benefit of a primary prevention implantable cardioverter-defibrillator (ICD) has been challenged. Left ventricular (LV) scar identified by cardiac magnetic resonance (CMR) imaging is associated with a high risk of malignant arrhythmia in NICM. We aimed to determine the impact of LV scar on the mortality benefit from a primary prevention ICD in NICM.

Methods and results

We recruited 452 consecutive heart failure patients [New York Heart Association (NYHA) Class II/III] with NICM and LV ejection fraction ≤35% from a state-wide CMR service. All patients fulfilled European Society of Cardiology guidelines for primary prevention ICD implantation; however, the decision to implant was at the treating physician's discretion. Baseline clinical and CMR data were recorded prospectively and heart failure mortality risk (MAGGIC score) was calculated. The primary study outcome measurement was all-cause mortality based on presence or absence of ICD, stratified by LV scar. Median follow-up was 37.9 months and there was no difference in MAGGIC score between those who did and did not receive a primary prevention ICD (19.30 ± 5.46 vs. 18.90 ± 5.67, P = 0.50). In patients without LV scar, ICD implantation was not associated with improved mortality [hazard ratio (HR) = 1.22, 95% confidence interval (CI): 0.53-2.78, P = 0.64]. In patients with LV scar, ICD implantation was independently associated with reduced mortality (HR = 0.45, 95% CI: 0.26-0.77, P = 0.003).

Conclusions

In patients with NICM, primary prevention ICD implantation is only associated with reduced mortality in patients with LV scar. This may enable more effective selection of NICM patients for ICD implantation compared with current guidelines.

Endocardial-Epicardial Phase Mapping of Prolonged Persistent Atrial Fibrillation Recordings

Background:

Endocardial-epicardial dissociation and focal breakthroughs in humans with atrial fibrillation (AF) have been recently demonstrated using activation mapping of short 10-second AF segments. In the current study, we used simultaneous endo-epi phase mapping to characterize endo-epi activation patterns on long segments of human persistent AF.

Methods:

Simultaneous intraoperative mapping of endo- and epicardial lateral right atrium wall was performed in patients with persistent AF using 2 high-density grid catheters (16 electrodes, 3 mm spacing). Filtered unipolar and bipolar electrograms of continuous 2-minute AF recordings and electrodes locations were exported for phase analyses. We defined endocardial-epicardial dissociation as phase difference of ≥20 ms between paired endo-epi electrodes. Wavefronts were classified as rotations, single wavefronts, focal waves, or disorganized activity as per standard criteria. Endo-Epi wavefront patterns were simultaneously compared on dynamic phase maps. Complex fractionated electrograms were defined as bipolar electrograms with ≥5 directional changes occupying at least 70% of sample duration.

Results:

Fourteen patients with persistent AF undergoing cardiac surgery were included. Endocardial-epicardial dissociation was seen in 50.3% of phase maps with significant temporal heterogeneity. Disorganized activity (Endo: 41.3% versus Epi: 46.8%, P =0.0194) and single wavefronts (Endo: 31.3% versus Epi: 28.1%, P =0.129) were the dominant patterns. Transient rotations (Endo: 22% versus Epi: 19.2%, P =0.169; mean duration: 590±140 ms) and nonsustained focal waves (Endo: 1.2% versus Epi: 1.6%, P =0.669) were also observed. Apparent transmural migration of rotational activations (n=6) from the epi- to the endocardium was seen in 2 patients. Electrogram fractionation was significantly higher in the epicardium than endocardium (61.2% versus 51.6%, P <0.0001).

Conclusions:

Simultaneous endo-epi phase mapping of prolonged human persistent AF recordings shows significant Endocardial-epicardial dissociation marked temporal heterogeneity, discordant and transitioning wavefronts patterns and complex fractionations. No sustained focal activity was observed. Such complex 3-dimensional interactions provide insight into why endocardial mapping alone may not fully characterize the AF mechanism and why endocardial ablation may not be sufficient.

Graphic Abstract:

A graphic abstract is available for this article.

Measuring atrial stasis during sinus rhythm in patients with paroxysmal atrial fibrillation using 4 Dimensional flow imaging: 4D flow imaging of atrial stasis

BACKGROUND

Paroxysmal atrial fibrillation (PAF) is associated with cardioembolic risk, however events may occur during sinus rhythm (SR). 4D-flow cardiac magnetic resonance (CMR) imaging allows visualisation of left atrial blood flow, to determine the residence time distribution (RTD), an assessment of atrial transit time.

OBJECTIVE

To determine if atrial transit time is prolonged in PAF patients during SR, consistent with underlying atrial stasis.

METHOD

91 participants with PAF and 18 healthy volunteers underwent 4D flow analysis in SR. Velocity fields were produced RTDs, calculated by seeding virtual 'particles' at the right upper pulmonary vein and counting them exiting the mitral valve. An exponential decay curve quantified residence time of particles in the left atrium, and atrial stasis was expressed as the derived constant (RTD_TC) based on heartbeats. The RTD_TC was evaluated within the PAF group, and compared to healthy volunteers.

RESULTS

Patients with PAF (n = 91) had higher RTD_TC compared with gender-matched controls (n = 18) consistent with greater atrial stasis (1.68 ± 0.46 beats vs 1.51 ± 0.20 beats; p = .005). PAF patients with greater thromboembolic risk had greater atrial stasis (median RTD_TC of 1.72 beats in CHA₂DS₂-VASc≥2 vs 1.52 beats in CHA₂DS₂-VASc<2; p = .03), only female gender and left ventricular ejection fraction contributed significantly to the atrial RTD_TC (p = .006 and p = .023 respectively).

CONCLUSIONS

Atrial stasis quantified by 4D flow is greater in PAF, correlating with higher CHA₂DS₂-VASc scores. Female gender and systolic dysfunction are associated with atrial stasis. RTD offers an insight into atrial flow that may be developed to provide a personalised assessment of thromboembolic risk.

Direct Thrombin Inhibitors as an Alternative to Heparin During Catheter Ablation: A Multicenter Experience

OBJECTIVES

The goal of this study was to report a multicenter series of left-sided catheter ablations performed by using intravenous direct thrombin inhibitors (DTIs) as an alternative to heparin.

BACKGROUND

Amidst a looming worldwide shortage of heparin, there are insufficient data to guide nonheparin-based peri-procedural anticoagulation in patients undergoing catheter ablation.

METHODS

This study reviewed all catheter ablations at 6 institutions between 2006 and 2019 to assess the safety and efficacy of DTIs for left-sided radiofrequency catheter ablation of atrial fibrillation and ventricular tachycardia.

RESULTS

In total, 53 patients (age 63.0 ± 9.3 years, 68% male, CHA₂DS₂-VASc [congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, stroke/transient ischemic attack, vascular disease, age 65 to 74 years, sex category] score 2.8 ± 1.6, left ventricular ejection fraction 46 ± 15%) underwent ablation with DTIs (75% bivalirudin, 25% argatroban) due to heparin contraindication(s) (72% heparin-induced thrombocytopenia, 21% heparin allergy, 4% protamine reaction, and 4% religious reasons). The patient's usual oral anticoagulant was continued without interruption in 69%. Procedures were performed for atrial fibrillation (64%) or ventricular tachycardia/premature ventricular contractions (36%). Transseptal puncture was undertaken in 81%, and a contact force-sensing catheter was used in 70%. Vascular ultrasound was used in 71%, and femoral arterial access was gained in 36%. A bolus followed by infusion was used in all but 4 cases, and activated clotting time was monitored peri-procedurally in 72%, with 32% receiving additional boluses. Procedure duration was 216 ± 116 min, and ablation time was 51 ± 22 min. No major bleeding or embolic complications were observed. Four patients had minor self-limiting bleeding complications, including a small pericardial effusion (<1 cm), a small groin hematoma, and hematuria.

CONCLUSIONS

In this multicenter series, intravenous DTIs were safely used as an alternative to heparin for left-sided catheter ablation.

Alcohol Abstinence in Drinkers with Atrial Fibrillation

BACKGROUND

Excessive alcohol consumption is associated with incident atrial fibrillation and adverse atrial remodeling; however, the effect of abstinence from alcohol on secondary prevention of atrial fibrillation is unclear.

METHODS

We conducted a multicenter, prospective, open-label, randomized, controlled trial at six hospitals in Australia. Adults who consumed 10 or more standard drinks (with 1 standard drink containing approximately 12 g of pure alcohol) per week and who had paroxysmal or persistent atrial fibrillation in sinus rhythm at baseline were randomly assigned in a 1:1 ratio to either abstain from alcohol or continue their usual alcohol consumption. The two primary end points were freedom from recurrence of atrial fibrillation (after a 2-week "blanking period") and total atrial fibrillation burden (proportion of time in atrial fibrillation) during 6 months of follow-up.

RESULTS

Of 140 patients who underwent randomization (85% men; mean [±SD] age, 62±9 years), 70 were assigned to the abstinence group and 70 to the control group. Patients in the abstinence group reduced their alcohol intake from 16.8±7.7 to 2.1±3.7 standard drinks per week (a reduction of 87.5%), and patients in the control group reduced their alcohol intake from 16.4±6.9 to 13.2±6.5 drinks per week (a reduction of 19.5%). After a 2-week blanking period, atrial fibrillation recurred in 37 of 70 patients (53%) in the abstinence group and in 51 of 70 patients (73%) in the control group. The abstinence group had a longer period before recurrence of atrial fibrillation than the control group (hazard ratio, 0.55; 95% confidence interval, 0.36 to 0.84; P = 0.005). The atrial fibrillation burden over 6 months of follow-up was significantly lower in the abstinence group than in the control group (median percentage of time in atrial fibrillation, 0.5% [interquartile range, 0.0 to 3.0] vs. 1.2% [interquartile range, 0.0 to 10.3]; P = 0.01).

CONCLUSIONS

Abstinence from alcohol reduced arrhythmia recurrences in regular drinkers with atrial fibrillation. (Funded by the Government of Victoria Operational Infrastructure Support Program and others; Australian New Zealand Clinical Trials Registry number, ACTRN12616000256471.).