Tachycardia-induced cardiomyopathy: a reversible form of left ventricular dysfunction

Premature atrial contraction induced cardiomyopathy: A case report

This case report describes the successful management of a 45-year-old female patient with incessant premature atrial complexes (PACs) leading to left ventricular dysfunction. Despite initial treatment with beta-blockers, the patient's PACs persisted, prompting catheter ablation. Mapping in the left atrium identified the site of earliest atrial activation near the right superior pulmonary vein, and radiofrequency energy successfully terminated the PACs. Follow-up assessments showed the patient remained asymptomatic, with normalized left ventricular function. This case highlights the efficacy of catheter ablation in resolving PAC-induced cardiomyopathy and emphasizes the need for further research in this area.

Echocardiographic changes and heart failure hospitalizations following rhythm control for arrhythmia-induced cardiomyopathy: results from a multicenter, retrospective study

BACKGROUND

The incidence and prevalence of arrhythmia-induced cardiomyopathy (AIC) are unclear but likely underrecognized. LV dysfunction is common among patients with atrial fibrillation (AF), atrial flutter (AFL), and frequent premature ventricular contractions (PVC). The hallmark of AIC is the improvement of left ventricular ejection fraction (LVEF) following arrhythmia treatment. Changes in echocardiographic parameters and their effect on outcomes after rhythm control for AIC are not well understood. We aimed to study echocardiographic parameters and outcomes following rhythm control for AIC.

METHODS

A multicenter, retrospective study was conducted at 4 different medical centers involving patients with AIC. Clinical, echocardiographic, and outcome (mortality and heart failure hospitalizations [HFH]) parameters were extracted from the medical record.

RESULTS

Two hundred fifty-five patients (age 66 ± 11 years, 73% male) with AIC caused by AF (51%), atrial tachycardia/AFL (20%), and PVCs (29%) were included and followed for a median period of 6 months after successful rhythm control. Significant improvements in left ventricular (LV) ejection fraction (P < 0.0001), LV end-systolic volume (ml) (90 ± 48 to 58 ± 30; P < 0.0001), LV internal diameter end diastole (cm) (5.5 ± 0.78 to 5.3 ± 0.64; P = 0.0001) and end systole (4.7 ± 0.95 to 4.3 ± 1.02; P < 0.0001), right atrial pressure (mmHg) (11.3 ± 5.0 to 7.4 ± 3.2; P = 0.0001), and right ventricular function (n (%)) (42 (44) to 9 (11); P < 0.0001) were noted following arrhythmia treatment. No deaths occurred during follow-up. HFH occurred in 7 patients. Arrhythmia recurrence rate was 50.5%. Neither echocardiographic parameters nor recurrence of arrhythmia correlated with HFH.

CONCLUSION

Arrhythmia treatment significantly improved echocardiographic LV dimensions, LVEF, and RAP in this multicenter AIC cohort, underscoring the need for early recognition and aggressive rhythm control in suspected AIC patients. The event rate was too low to assess for outcome predictors.

Severe Cardiovascular Effects of Prolonged Untreated Hyperthyroidism Manifesting As Thyroid Storm

A thyroid storm is a rare but life-threatening manifestation of thyrotoxicosis. It still remains a diagnostic challenge as there are no specific laboratory investigations or universally accepted criteria for diagnosing thyroid storms. Diagnosis is mainly based on clinical findings, evidence of hyperthyroidism, and life-threatening symptoms. A thyroid storm has a high risk of mortality mostly due to multi-organ failure and heart failure. Cardiovascular manifestations are the most common presentation of hyperthyroidism; cardiac involvement also has the potential to be the most serious complication. Management of cardiovascular manifestations should be managed aggressively to prevent long-term myocardial damage. A high index of suspicion should be maintained in young adults presenting with heart failure and arrhythmia. We present a case of potentially life-threatening cardiovascular effects of thyroid storm and management in the ICU.

Atrial fibrillation-induced tachycardiomyopathy and heart failure: an underappreciated and elusive condition

Many patients with persistent, chronic, or frequently recurring paroxysmal atrial fibrillation (AF) may develop a tachycardiomyopathy (TCM) with left ventricular (LV) dysfunction and heart failure (HF), which is reversible upon restoration and maintenance of sinus rhythm, when feasible, or via better and tighter ventricular rate (VR) control. Mechanisms involved in producing this leading cause of TCM (AF-TCM) include loss of atrial contraction, irregular heart rate, fast VR, neurohumoral activation, and structural myocardial changes. The most important of all mechanisms relates to optimal VR control, which seems to be an elusive target. Uncontrolled AF may also worsen preexisting LV dysfunction and exacerbate HF symptoms. Data, albeit less robust, also point to deleterious effects of slow VRs on LV function. Thus, a J-shaped relationship between VR and clinical outcome has been suggested, with the optimal VR control hovering at ~ 65 bpm, ranging between 60 and 80 bpm; VRs above and below this range may confer higher morbidity and mortality rates. A convergence of recent guidelines is noted towards a stricter rather than a more lenient VR control with target heart rate < 80 bpm at rest and < 110 bpm during moderate exercise which seems to prevent TCM or improve LV function and exercise capacity and relieve TCM-related symptoms and signs. Of course, restoring and maintaining sinus rhythm is always a most desirable target, when feasible, either with drugs or more likely with ablation. All these issues are herein reviewed, current guidelines are discussed and relevant data are tabulated and pictorially illustrated.

Epicardial Adipose Tissue Thickness is Higher in Right Ventricular Outflow Tract Tachycardia

Introduction: Idiopathic ventricular arrhythmias, which occur in the absence of structural heart disease, are commonly originating from the outflow tract, and 80% of the them arise from the right ventricle. Epicardial adipose tissue (EAT), which originates from the splanchnopleuric mesoderm, has been shown to be an important source of inflammatory mediators and plays an important role in cardiac autonomic function by epicardial ganglionated plexuses. EAT may potentially contribute to the pathophysiology of idiopathic right ventricular outflow tract (RVOT) tachycardia by different mechanisms. In this study, we aimed to investigate the relationship between EAT thickness and RVOT tachycardia. Methods: This study included 55 patients (32 male, 23 female) with RVOT tachycardia and 60 control subjects (38 male, 22 female). Patients who had more than three consecutive ventricular beats over 100 bpm with specific morphological features on the electrocardiogram (ECG) were diagnosed with RVOT tachycardia. EAT thickness was measured by transthoracic echocardiography. Results: EAT thickness was significantly higher in the RVOT tachycardia group (p <0.05). Ejection fraction (EF), and the thickness of the posterior wall of the left ventricle and of the interventricular septum were significantly lower, and left ventricular end-diastolic diameter, left ventricular end-systolic diameter, and left atrial diameter were significantly higher in patients who had RVOT tachycardia compared to normal subjects (p <0.05). Conclusion: Patients who were diagnosed with RVOT tachycardia had increased EAT thickness compared to normal subjects. The underlying mechanism of the condition could be mechanical, metabolic, infiltrative, or autonomic effects of the EAT.

A retrospective evaluation of catheter ablation in atrial flutter post cardiac transplantation

BACKGROUND

Atrial flutter is the most common arrhythmia post cardiac transplantation. Observational studies in the non-transplant population have shown prognostic benefit with catheter ablation; however, there are no data in the heart transplant population.

OBJECTIVES

This study evaluated the experience of catheter ablation in atrial flutter post cardiac transplantation.

METHODS

A retrospective review of experience of late onset atrial flutter at the Freeman Hospital, Newcastle-upon-Tyne, UK, between 1985 and January 2020.

RESULTS

Sixty eight of the 722 patients who survived 6 months post cardiac transplantation developed late atrial flutter giving an incidence of 9.4%. Thirty-two patients were managed with ablation with treatment largely determined by time of flutter onset. Kaplan Meier estimates for arrhythmia free survival post first ablation for organized atrial arrhythmias was 83.3% at 1 year. Kaplan-Meier estimates for median survival post onset of atrial arrhythmias treated with ablation was 11.34 years (95% CI 8.00-14.57), compared to 5.79 years in patients managed medically (95%CI 2.26-9.32) (P = .026).

CONCLUSIONS

Atrial flutter is an important late complication of cardiac transplantation. Patients treated with ablation in the modern era had increased survival compared to a historical cohort.

Efficacy and Safety of SATAKE HotBalloon® Catheter for Treatment of Paroxysmal Atrial Fibrillation - A Post-Marketing Surveillance Study

BACKGROUND

SATAKE HotBalloon^®catheter (HBC) is a radiofrequency balloon catheter for the treatment of atrial fibrillation (AF), and was approved for use in Japan to treat drug-resistant paroxysmal AF in 2015. Post-marketing surveillance study was conducted by Toray Industries, Inc. to evaluate the efficacy and safety of HBC treatment in patients with paroxysmal AF in a real-world setting. This study is the first nation-wide survey of HBC treatment for paroxysmal AF in clinical practice in Japan.Methods and Results:This was a single-arm, multicenter observational study with an observation period of 48 weeks after ablation. Pulmonary vein isolation and AF non-recurrence rates were evaluated and adverse events (AEs) were observed at 46 sites in Japan. An AF event was defined as recurrence of AF or re-ablation from 12 to 48 weeks after ablation. The success rate of pulmonary vein isolation was 99.0% (486/491) for patients with AF. The cumulative AF non-recurrence rate was 94.1% at 24 weeks and 87.8% at 48 weeks. AEs were found to occur 21.5% (114/530), and ablation-related AEs were found to occur 2.6% (14/530) during the study period, with the most common being pericardial effusion (0.8%, 4/530).

CONCLUSIONS

This study demonstrates the efficacy and safety of HBC ablation in Japanese patients with recurrent symptomatic paroxysmal AF refractory to antiarrhythmic therapy.

Atypical location of Coumel Tachycardia in Adult: Case Report

Coumel Tachycardia or Incessant Junctional Reentrant (IJRT) generally affects the infant-juvenile population and is characterized by tachycardia due to atrioventricular reentry (AV) mediated by an exclusive, slow, decremental retrograde conduction pathway mostly located in the posterosseptal region of the tricuspid ring. Case report: The present study reported the case of an adult, 49 years old, with IJRT of atypical location. The patient reported feeling palpitations for 5 years with worsening in the last 6 months. After one of his seizures, an electrocardiogram (ECG) documented tachycardia due to AV reentry with a long RP ‘interval. Subjected to an electrophysiological study, an accessory pathway of exclusive retrograde conduction with decreasing characteristics was observed, located in the right mid-septal region. There was easy induction of IJRT, remaining sustained throughout the study. A radiofrequency ablation was performed in the mid-septal D region with interruption of tachycardia, with no more atrioventricular retrograde conduction, the procedure ended without complications. Discussion: Interestingly, the case described differs both in terms of the age range of the most frequent involvement of the IJRT (children and young people), as well as the most common location of the accessory pathway (posterior and postero-septal region of the tricuspid ring). Ablation proved to be effective in this case and is the treatment of choice for IJRT despite the anomalous location of the accessory pathway (Middle-septal D: described in bibliographic reviews in only 7% of IJRT cases) and a potentially dangerous region due to proximity to the trunk of the His beam.

Large Animal Models of Heart Failure: A Translational Bridge to Clinical Success

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Preclinical large animal models play a critical and expanding role in translating basic science findings to the development and clinical approval of novel cardiovascular therapeutics.

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This state-of-the-art review outlines existing methodologies and physiological phenotypes of several HF models developed in large animals. A comprehensive list of porcine, ovine, and canine models of disease are presented, and the translational importance of these studies to clinical success is highlighted through a brief overview of recent devices approved by the FDA alongside associated clinical trials and preclinical animal reports.

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Increasing the use of large animal models of HF holds significant potential for identifying new mechanisms underlying this disease and providing valuable information regarding the safety and efficacy of new therapies, thus, improving physiological and economical translation of animal research to the successful treatment of human HF.

Preclinical large animal models of heart failure (HF) play a critical and expanding role in translating basic science findings to the development and clinical approval of novel therapeutics and devices. The complex combination of cardiovascular events and risk factors leading to HF has proved challenging for the development of new treatments for these patients. This state-of-the-art review presents historical and recent studies in porcine, ovine, and canine models of HF and outlines existing methodologies and physiological phenotypes. The translational importance of large animal studies to clinical success is also highlighted with an overview of recent devices approved by the Food and Drug Administration, together with preclinical HF animal studies used to aid both development and safety and/or efficacy testing. Increasing the use of large animal models of HF holds significant potential for identifying the novel mechanisms underlying the clinical condition and to improving physiological and economical translation of animal research to successfully treat human HF.

Left Ventricular Extracellular Volume Expansion Is Not Associated with Atrial Fibrillation or Atrial Fibrillation-mediated Left Ventricular Systolic Dysfunction

PURPOSE

To determine whether left ventricular (LV) extracellular volume (ECV) expansion is associated with atrial fibrillation (AF) or AF-mediated LV systolic dysfunction (LVSD) while minimizing the influence of biologic and imaging methodologic confounders.

MATERIALS AND METHODS

This study examined the prevalence of LV ECV expansion in 137 patients with AF (mean age, 62 years ± 11 [standard deviation]; 92 male patients and 45 female patients; 83 paroxysmal and 54 persistent) who underwent preablation cardiovascular MRI. Biologic confounders were minimized by measuring the ECV fraction and excluding patients with severe LV hypertrophy, defined as wall thickness greater than 1.5 cm. Imaging confounders were minimized by using an arrhythmia-insensitive-rapid (AIR) cardiac T1 mapping pulse sequence. Other cardiac functional parameters, including LV ejection fraction (LVEF) and left atrial end-diastolic volume indexed to body surface area, were assessed using cine cardiovascular MRI. A substudy was conducted in 32 patients with no AF (mean age, 54 years ± 16) in sinus rhythm to establish control values and convert these values between the AIR sequence and literature-based modified Look-Locker inversion recovery (MOLLI) values.

RESULTS

The mean ECV was not significantly different (P > .05) between patients with AF with a normal LVEF (24.5% ± 2.8; n = 107), patients with AF with LVSD (24.5% ± 2.5; n = 30), and patients with no AF (24.4% ± 3.8; n = 32), but there was a significant interaction between ECV and CHA₂DS₂-VASc score (P = .045). Compared with the literature data obtained from healthy control patients scanned using MOLLI, 99.3% of patients with AF had ECV below the fibrosis cutoff point (32.8% when converted from MOLLI T1 mapping to AIR T1 mapping), including a subset of patients with AF (n = 28) with low CHA₂DS₂-VASc score (0/1 for men/women).

CONCLUSION

Study results suggest that an LV ECV expansion is not associated with AF or AF-mediated LVSD. Supplemental material is available for this article. © RSNA, 2020See also the commentary by Stillman in this issue.

Strict Versus Lenient Versus Poor Rate Control Among Patients With Atrial Fibrillation and Heart Failure (from the Get With The Guidelines - Heart Failure Program)

Randomized data suggest lenient rate control (resting heart rate <110 beats/min) is noninferior to strict rate control (resting heart rate <80 beats/min) in patients with atrial fibrillation (AF). However, the optimal rate control strategy in patients with AF and heart failure (HF) remains unknown. Accordingly, we performed an observational analysis using data from the Get With The Guidelines-HF Program linked with Medicare data from July 1, 2011, to September 30, 2014. Of 13,981 patients with AF and HF, 9,100 (65.0%) had strict rate control, 4,617 (33.0%) had lenient rate control, and 264 (1.9%) had poor rate control by resting heart rate on the day of discharge. After multivariable adjustment, compared with strict rate control, lenient rate control was associated with higher adjusted risks of death (hazard ratio [HR] 1.21, 95% confidence interval [CI] 1.11 to 1.33, p <0.001), all-cause readmission (HR 1.09, 95% CI 1.03 to 1.15, p <0.002), death or all-cause readmission (HR 1.11, 95% CI 1.05 to 1.18, p <0.001), but not cardiovascular readmission (HR1.08, 95% CI 1.00 to 1.16, p = 0.051) at 90 days. Associations were comparable in patients with poor rate control and with heart rate modeled as a continuous variable. The presence or absence of reduced ejection fraction did not impact the magnitude of most observed associations. In conclusion, in patients with HF and AF, 2 of 3 patients had a heart rate that met strict-control goals at discharge. Heart rates >80 beats/min were associated with adverse outcomes irrespective of left ventricular ejection fraction.

Left ventricular extracellular volume expansion does not predict recurrence of atrial fibrillation following catheter ablation

INTRODUCTION

A recent study reported that diffuse left ventricular (LV) fibrosis is a predictor of atrial fibrillation (AF) recurrence following catheter ablation, by measuring postcontrast cardiac T1 (an error prone metric as per the 2017 Society for Cardiovascular Magnetic Resonance consensus statement) using an inversion-recovery pulse sequence (an error prone method in arrhythmia) in AF ablation candidates. The purpose of this study was to verify the prior study, by measuring extracellular volume (ECV) fraction (an accurate metric) using a saturation-recovery pulse sequence (accurate method in arrhythmia).

METHODS AND RESULTS

This study examined 100 AF patients (mean age = 62 ± 11 years, 69 males and 31 females, 67 paroxysmal [pAF] and 33 persistent [peAF]) who underwent a preablation cardiovascular magnetic resonance (CMR) exam. LV ECV and left atrial (LA) and LV functional parameters were quantified using standard analysis methods. During an average follow-up period of 457 ± 261 days with 4 ± 3 rhythm checks per patient, 72 patients maintained sinus rhythm. Between those who maintained sinus rhythm (n = 72) and those who reverted to AF (n = 28), the only clinical characteristic that was significantly different was age (60 ± 12 years vs 66 ± 9 years); for CMR metrics, neither mean LV ECV (25.1 ± 3.3% vs 24.7 ± 3.7%), native LV T1 (1093.8 ± 73.5 ms vs 1070.2 ± 115.9 ms), left ventricular ejection fraction (54.1 ± 11.2% vs 55.7 ± 7.1%), nor LA end diastolic volume/body surface area (42.4 ± 14.8 mL/m2 vs 43.4 ± 19.6 mL/m2 ) were significantly different (P ≥ .23). According to Cox regression tests, none of the clinical and imaging variables predict AF recurrence.

CONCLUSION

Neither LV ECV nor other CMR metrics predict recurrence of AF following catheter ablation.

Tackling Patient-Reported Outcomes in Atrial Fibrillation and Heart Failure: Identifying Disease-Specific Symptoms?

Atrial fibrillation (AF) and heart failure (HF) both significantly affect morbidity and mortality and also account for high symptom burden and impaired health-related quality of life (hrQoL). Several well-designed and broadly implemented patient-reported outcome instruments are available for both AF and HF and can easily measure hrQoL in each disease process. A better understanding of the diverse phenotypes of AF and HF, as well as the heterogeneous treatment effects of disease-specific interventions, is necessary to further disentangle the complex relationship between symptoms of AF and HF.

Improvement in ejection fraction after cryoballoon pulmonary vein isolation for atrial fibrillation in individuals with systolic dysfunction

BACKGROUND

Cryoballoon pulmonary vein isolation (PVI) is commonly used for rhythm control of atrial fibrillation (AF). Data are limited examining the outcomes of cryoballoon PVI in patients with systolic dysfunction. We evaluate the impact of cryoballoon PVI in patients with systolic dysfunction.

METHODS

We evaluated a single-center prospective registry of patients undergoing cryoballoon PVI between 8/2011 and 6/2016. Patients with systolic dysfunction (EF < 55%) between the time of AF diagnosis and their cryoballoon PVI procedure were assessed for AF recurrence at 6 months and 1 year post-procedure, with a 3-month blanking period.

RESULTS

Final analysis included 66 patients with systolic dysfunction undergoing cryoballoon PVI. An AF diagnosis for ≥ 1 year prior to PVI was present in 62.1% (n = 41), and 53.0% (n = 35) had systolic dysfunction for ≥ 1 year pre-procedure. The proportion of AF-free patients at 1 year was 51.5%. Of patients with echocardiograms performed at 1 year (n = 43), a greater proportion of individuals without AF recurrence had an improvement in EF of ≥ 10% than in those with AF recurrence (54.2% vs. 25.0%, p = 0.039). Of the patients who had systolic dysfunction at the time of the ablation (EF < 55%), there was a significant increase in EF post-procedure (36.5% pre-procedure vs. 48.3% post-procedure, mean change 11.8%, p < 0.001).

CONCLUSION

In patients with systolic dysfunction, cryoballoon PVI provides an acceptable AF recurrence-free rate at 1 year. AF recurrence-free individuals were more likely to have improvement in EF. Further evaluation is needed to determine the potential role of early cryoballoon PVI in patients with a new diagnosis of systolic dysfunction and AF.

His Bundle Pacing: Concept to Reality

This article summarizes the initial experience with permanent His bundle pacing, the lessons learned, and the concepts that have been developed in the subsequent decade of experience with His bundle pacing. This article also addresses the advancements in technology, which have allowed His bundle pacing to be more widely adopted and used in various clinical situations.

Sustained atrial fibrillation increases the risk of anticoagulation-related bleeding in heart failure

BACKGROUND

Oral anticoagulation therapy in individuals with atrial fibrillation (AF) reduces the risk of thromboembolic events at cost of an increased bleeding risk. Whether anticoagulation-related outcomes differ between patients with paroxysmal and sustained AF receiving anticoagulation is controversially discussed.

METHODS

In the present analysis of the prospective multi-center cohort study thrombEVAL, the incidence of anticoagulation-related adverse events was analyzed according to the AF phenotype. Information on outcome was centrally recorded over 3 years, validated via medical records and adjudicated by an independent review panel. Study monitoring was provided by an independent institution.

RESULTS

Overall, the sample comprised 1089 AF individuals, of whom n = 398 had paroxysmal AF and n = 691 experienced sustained AF. In Cox regression analysis with adjustment for potential confounders, sustained AF indicated an independently elevated risk of clinically relevant bleeding compared to paroxysmal AF [hazard ratio (HR) 1.40 (1.02; 1.93); P = 0.038]. For clinically relevant bleeding, a significant interaction of the pattern of AF type with concomitant heart failure (HF) was detected: HR_HF 2.45 (1.51, 3.98) vs. HR_{no HF} 0.85 (0.55, 1.34); P_interaction = 0.003. In HF patients, sustained AF indicated also an elevated risk of major bleeding [HR 2.25 (1.26, 4.20); P = 0.006]. A simplified HAS-BLED score incorporating only information on age (> 65 years), bleeding history, and HF with sustained AF demonstrated better discriminative performance for clinically relevant bleeding than the original version: AUC_HAS-BLED: 0.583 vs. AUC_{simplifiedHAS-BLED}: 0.642 (P = 0.004).

CONCLUSIONS

In HF patients receiving oral anticoagulation, sustained AF indicates a substantially elevated risk of bleeding.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov , identifier: NCT01809015.

Modeling of Amiodarone Effect on Heart Rate Control in Critically Ill Patients with Atrial Tachyarrhythmias

AIMS

Amiodarone is the gold-standard medication to control heart rate in critically ill patients with atrial tachyarrhythmias (ATs); however, effective doses and covariates influencing its efficacy remain unknown. We therefore performed pharmacodynamic modeling of heart rate reduction induced by amiodarone in these patients.

METHODS AND RESULTS

This observational study included 80 consecutive severely ill patients receiving amiodarone to treat ATs. A total of 1348 time-heart rate observations with 361 amiodarone dose administrations were analyzed during a period of up to 6 days after hospital treatment initiation using a nonlinear mixed-effect model. Pretreatment with amiodarone before intensive care administration, paroxysmal versus persistent AT, catecholamine infusion, and fluid and magnesium loading were among the covariates assessed in the model. In case of paroxysmal AT in a patient not pretreated with amiodarone, a 300 mg intravenous loading dose combined with an 800 mg oral dose on the first day, followed by 800 mg/day orally for 4 days was effective in achieving a heart rate between 80 and 115 bpm within the first day, and to maintain it during the next 4 days. Corresponding doses were twice as high in patients with persistent AT. Use of intravenous magnesium (p < 0.02) and fluid loading (p < 0.02) was associated with an earlier and greater heart rate decrease, while use of dobutamine had an opposite influence (p < 0.05).

CONCLUSIONS

In critically ill patients with AT, the dose of amiodarone required to control heart rate is influenced by the type of AT and by other easily measurable conditions which may allow better individualization of amiodarone dosing.

Usefulness of the WCD in patients with suspected tachymyopathy

AIMS

The wearable cardioverter defibrillator (WCD) is used for temporary protection of patients deemed to be at high risk for sudden death. There is limited experience regarding the clinical development of patients with tachymyopathy. We aimed to evaluate the clinical development of tachymyopathy patients protected with a WCD in a single-center non-randomized patient cohort.

METHODS AND RESULTS

We fitted 130 consecutive patients deemed to be at high risk for ventricular tachyarrhythmias with the WCD. Of these, 20 patients (15%) presenting with newly diagnosed heart failure in the setting of rapidly conducted atrial fibrillation/flutter were suspected to suffer from tachymyopathy. The control group consisted of the remaining 110 patients with other indications for WCD therapy. LVEF increased by more than 10% in 13/20 (65%) tachymyopathy patients compared to 40/110 (36%) patients in the control population (p = 0.01). Similarly, BNP levels decreased in 15/20 (75%) tachymyopathy patients compared to 41/110 (37%) in the control group (p = 0.05). ICD implantation rates were lower in the tachymyopathy group (3/20) compared to the control population (40/110; p = 0.04). On further follow-up (mean 12 ± 8 months), patients with suspected tachymyopathy had no sustained ventricular arrhythmias. Compared to 5/110 patients in the control group, no tachymyopathy patient died.

CONCLUSION

Most of the patients with suspected tachymyopathy have a favorable clinical outcome. The WCD is useful for temporary protection while LV function recovers.

Integrated TK-TD modeling for drug-induced concurrent tachycardia and QT changes in beagle dogs

Drug-induced cardiotoxicity, including tachycardia and QT prolongation, remains a major safety concern that needs to be identified and its risk mitigated in early stages of drug development. In the present study, an integrated toxicokinetic-toxicodynamic (TK-TD) modeling approach within a nonlinear mixed-effect modeling framework is applied to investigate concurrent abnormal heart rate and QT changes in three beagle dogs, using a Novartis internal compound (NVS001) as the case example. By accounting for saturable drug absorption, circadian rhythms, drug-effect tolerance, and nonlinear rate-dependency of QT interval, the dynamic TK-TD model captures the experimentally observed drug effects on heart rate and QT interval across a wide dosing range of NVS001 in beagle dogs. Further analyses reveal that the NVS001-induced QT prolongation observed in the low-dose groups is potentially caused by direct drug inhibition on the hERG channel, while the apparent QT shortening in the high-dose groups may be due to strong rate-dependency of QT at high heart rates. This study also suggests that the TK-TD model can be used to identify direct drug effects on the non-rate-dependent QT component by dissociating QT changes from tachycardia and deriving a new QT correction method. The integrated TK-TD model presented here may serve as a novel quantitative framework for evaluating drug-induced concurrent changes in heart rate and QT to potentially facilitate preclinical and clinical safety studies.

PVCs, PVC-Induced Cardiomyopathy, and the Role of Catheter Ablation

Premature ventricular contractions (PVCs) are common arrhythmias noticed in the clinical setting because of premature depolarization of the ventricular myocytes. Although often thought to be reflective of underlying disease rather than intrinsically harmful, PVCs have recently been linked with worse outcomes in patients without significant cardiac disease. Long-term exposure to a high PVC burden can lead to the development of PVC-induced cardiomyopathy. The pathogenesis of this condition is poorly understood at the current time. Many studies have suggested that catheter ablation of these PVCs may result in reversal of the PVC-induced cardiomyopathy. This article will go over the natural history of PVCs and PVC-induced cardiomyopathy, as well as review the current literature on the role of catheter ablation in treating PVC-induced cardiomyopathy.

Comparative Efficacy of Nebivolol and Metoprolol to Prevent Tachycardia-Induced Cardiomyopathy in a Porcine Model

Chronic tachycardia is a well-known cause of nonischemic cardiomyopathy. We hypothesized that nebivolol, a β-blocker with nitric oxide activity, would be superior to a pure β-blocker in preventing tachycardia-induced cardiomyopathy in a porcine model. Fifteen healthy Yucatan pigs were randomly assigned to receive nebivolol, metoprolol, or placebo once a day. All pigs underwent dual-chamber pacemaker implantation. The medication was started the day after the pacemaker implantation. On day 7 after implantation, each pacemaker was set at atrioventricular pace (rate, 170 beats/min), and the pigs were observed for another 7 weeks. Transthoracic echocardiograms, serum catecholamine levels, and blood chemistry data were obtained at baseline and at the end of the study. At the end of week 8, the pigs were euthanized, and complete histopathologic studies were performed. All the pigs developed left ventricular cardiomyopathy but remained hemodynamically stable and survived to the end of the study. The mean left ventricular ejection fraction decreased from baseline by 34%, 20%, and 20% in the nebivolol, metoprolol, and placebo groups, respectively. These changes did not differ significantly among the 3 groups (P =0.51). Histopathologic analysis revealed mild left ventricular perivascular fibrosis with cardiomyocyte hypertrophy in 14 of the 15 pigs. Both nebivolol and metoprolol failed to prevent cardiomyopathy in our animal model of persistent tachycardia and a high catecholamine state.

2016 Guidelines of the Taiwan Heart Rhythm Society and the Taiwan Society of Cardiology for the management of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia. Both the incidence and prevalence of AF are increasing, and the burden of AF is becoming huge. Many innovative advances have emerged in the past decade for the diagnosis and management of AF, including a new scoring system for the prediction of stroke and bleeding events, the introduction of non-vitamin K antagonist oral anticoagulants and their special benefits in Asians, new rhythm- and rate-control concepts, optimal endpoints of rate control, upstream therapy, life-style modification to prevent AF recurrence, and new ablation techniques. The Taiwan Heart Rhythm Society and the Taiwan Society of Cardiology aimed to update the information and have appointed a jointed writing committee for new AF guidelines. The writing committee members comprehensively reviewed and summarized the literature, and completed the 2016 Guidelines of the Taiwan Heart Rhythm Society and the Taiwan Society of Cardiology for the Management of Atrial Fibrillation. This guideline presents the details of the updated recommendations, along with their background and rationale, focusing on data unique for Asians. The guidelines are not mandatory, and members of the writing committee fully realize that treatment of AF should be individualized. The physician's decision remains most important in AF management.

His bundle pacing: Initial experience and lessons learned

Direct His bundle pacing provides the most physiologic means of artificial pacing of the ventricles with a preserved His-Purkinje system and may play a role in patients with a diseased intrinsic conduction system. We describe our initial motivations and experience with permanent direct His bundle pacing and important lessons learned since that time.

Mortality After Atrioventricular Nodal Radiofrequency Catheter Ablation With Permanent Ventricular Pacing in Atrial Fibrillation

Background—

Atrioventricular nodal radiofrequency ablation (AVNA) with permanent ventricular pacing can be used to control rate in patients with atrial fibrillation (AF). However, long-term outcomes after AVNA are uncertain, especially in light of irreversible pacemaker dependence.

Methods and Results—

We examined 9122 consecutive patients with AF. The outcomes in 453 patients with AVNA (26% of whom underwent an implantable cardiac defibrillator implant and 37% underwent cardiac resynchronization therapy implant) were compared with AF patients without AVNA after propensity score 1:1 matching. During follow-up in the propensity-matched cohort (2.41±3.23 years, median 1.23, quartiles 0.33–3.12), 100 patients died (yearly rate of death 6.6%). Mode of death was available in 86% of patients, which was cardiovascular in 67% of the patients (related to heart failure in 38%, sudden death in 5%, and other cardiovascular reason in 24%) and noncardiovascular in 33%. AVNA in patients with AF was associated with a lower risk of mortality (odds ratio 0.47, 95% confidence interval, 0.29–0.77; P =0.003), a lower risk of cardiovascular mortality (odds ratio =0.41, 95% confidence interval 0.23–0.73; P =0.003), and nonsignificant lower risk of stroke and thromboembolic events (odds ratio =0.61, 95% confidence interval 0.36–1.06; P =0.08).

Conclusions—

In sick AF patients with multiple comorbidities, AVNA with permanent ventricular pacing for rate control seems safe during follow-up and may be associated with lower mortality.

What About Tachycardia-induced Cardiomyopathy?

Long-standing tachycardia is a well-recognised cause of heart failure and left ventricular dysfunction, and has led to the nomenclature, tachycardia-induced cardiomyopathy (TIC). TIC is generally a reversible cardiomyopathy if the causative tachycardia can be treated effectively, either with medications, surgery or catheter ablation. The diagnosis is usually made after demonstrating recovery of left ventricular function with normalisation of heart rate in the absence of other identifiable aetiologies. One hundred years after the first reported case of TIC, our understanding of the pathophysiology of TIC in humans remains limited despite extensive work in animal models of TIC. In this review we will discuss the proposed mechanisms of TIC, the causative tachyarrhythmias and their treatment, outcomes for patients diagnosed with TIC, and future directions for research and clinical care.

Management of Patients With Recovered Systolic Function

Advancements in the treatment of heart failure (HF) with systolic dysfunction have given rise to a new population of patients with improved ejection fraction (EF). The management of this distinct population is not well described due to a lack of consensus on the definition of myocardial recovery, a scarcity of data on the natural history of these patients, and the absence of focused clinical trials. Moreover, an improvement in EF may have different prognostic and management implications depending on the underlying etiology of cardiomyopathy. This can be challenging for the clinician who is approached by a patient inquiring about a reduction of medical therapy after apparent EF recovery. This review explores management strategies for HF patients with recovered EF in a disease-specific format.

Increased Heart Rate Is Associated With Higher Mortality in Patients With Atrial Fibrillation (AF): Results From the Outcomes Registry for Better Informed Treatment of AF (ORBIT-AF)

BACKGROUND

Most patients with atrial fibrillation (AF) require rate control; however, the optimal target heart rate remains under debate. We aimed to assess rate control and subsequent outcomes among patients with permanent AF.

METHODS AND RESULTS

We studied 2812 US outpatients with permanent AF in the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation. Resting heart rate was measured longitudinally and used as a time-dependent covariate in multivariable Cox models of all-cause and cause-specific mortality during a median follow-up of 24 months. At baseline, 7.4% (n=207) had resting heart rate <60 beats per minute (bpm), 62% (n=1755) 60 to 79 bpm, 29% (n=817) 80 to 109 bpm, and 1.2% (n=33) ≥110 bpm. Groups did not differ by age, previous cerebrovascular disease, heart failure status, CHA2DS2-VASc scores, renal function, or left ventricular function. There were significant differences in race (P=0.001), sinus node dysfunction (P=0.004), and treatment with calcium-channel blockers (P=0.006) and anticoagulation (P=0.009). In analyses of continuous heart rates, lower heart rate ≤65 bpm was associated with higher all-cause mortality (adjusted hazard ratio [HR], 1.15 per 5-bpm decrease; 95% CI, 1.01 to 1.32; P=0.04). Similarly, increasing heart rate >65 bpm was associated with higher all-cause mortality (adjusted HR, 1.10 per 5-bpm increase; 95% CI, 1.05 to 1.15; P<0.0001). This relationship was consistent across endpoints and in a broader sensitivity analysis of permanent and nonpermanent AF patients.

CONCLUSIONS

Among patients with permanent AF, there is a J-shaped relationship between heart rate and mortality. These data support current guideline recommendations, and clinical trials are warranted to determine optimal rate control.

CLINICAL TRIAL REGISTRATION

URL: http://clinicaltrials.gov/. Unique identifier: NCT01165710.

Atrial and ventricular tachyarrhythmias in military personnel

Although rare, sudden cardiac death does occur in British military personnel. In the majority of cases, the cause is considered to be a malignant ventricular tachyarrhythmia, which can be precipitated by a number of underlying pathologies. Conversely, a tachyarrhythmia may have a more benign and treatable cause, yet the initial clinical symptoms may be similar, making differentiation difficult. This is an overview of the mechanisms underlying the initiation and propagation of arrhythmias and the various pathological conditions that predispose to arrhythmia genesis, classified according to which parts of the heart are involved: atrial tachyarrhythmias, atrial and ventricular, as well as those affecting the ventricles alone. It encompasses atrial tachycardia, atrial flutter, supraventricular tachycardias and ventricular tachycardias, including the more commonly encountered inherited primary electrical diseases, also known as the channelopathies. The clinical features, investigation and management strategies are outlined. The occupational impact-in serving military personnel and potential recruits-is described, with explanations relating to the different conditions and their specific implication on continued military service.

Remodeling of left circumflex coronary arterial tree in pacing-induced heart failure

Congestive heart failure (CHF) is a very serious heart disease that manifests an imbalance between left ventricle supply and demand. Although the mechanical demand of the failing heart has been well characterized, the systematic remodeling of the entire coronary arterial tree that constitutes the supply of the myocardium is lacking. We hypothesize that the well-known increase in ventricle wall stress during CHF causes coronary vascular rarefaction to increase the vascular flow resistance, which in turn compromises the perfusion of the heart. Morphometric (diameters, length, and numbers) data of the swine left circumflex (LCx) arterial tree were measured in both CHF (n = 6) and control (n = 6) groups, from which a computer reconstruction of the entire LCx tree was implemented down to the capillary level to enable a hemodynamic analysis of coronary circulation. The vascular flow resistance was increased by ∼75% due to a significant decrease of vessel numbers (∼45%) and diameters in the first capillary segments (∼10%) of the LCx arterial tree after 3-4 wk of pacing. The structural remodeling significantly changed the wall shear stress in vessel segments of the entire LCx arterial tree of CHF animals. This study enhances our knowledge of coronary arterial tree remodeling in heart failure, which provides a deeper understanding of the deterioration of supply-demand relation in left ventricle.

Atrial fibrillation and heart failure: cause or effect?

Atrial fibrillation (AF) and heart failure (HF) are two epidemics of the century that have a close and complex relationship. The mechanisms underlying this association remain an area of ongoing intense research. In this review, we will describe the relationship between these two public health concerns, the mechanisms that fuel the development and perpetuation of both, and the evolving concepts that may revolutionize our approach to this dual epidemic.

Outcomes after nonemergent electrical cardioversion for atrial arrhythmias

Electrical cardioversion (ECV) is recommended for rhythm control in patients with atrial arrhythmia; yet, ECV use and outcomes in contemporary practice are unknown. We reviewed all nonemergent ECVs for atrial arrhythmias at a tertiary care center (2010 to 2013), stratifying patients by transesophageal echocardiography (TEE) use before ECV and comparing demographics, history, vitals, and laboratory studies. Outcomes included postprocedural success and complications and repeat cardioversion, rehospitalization, and death within 30 days. Overall, 1,017 patients underwent ECV, 760 (75%) for atrial fibrillation and 240 (24%) for atrial flutter; 633 underwent TEE before ECV and 384 did not. TEE recipients were more likely to be inpatients (74% vs 44%, p <0.001), have higher mean CHADS2 scores (2.6 vs 2.4, p = 0.03), and lower mean international normalized ratios (1.2 vs 2.1, p <0.001). Overall, 89 patients (8.8%) did not achieve sinus rhythm and 14 experienced procedural complications (1.4%). Within 30 days, 80 patients (7.9%) underwent repeat ECV, 113 (11%) were rehospitalized, and 14 (1.4%) died. Although ECV success was more common in patients who underwent TEE before ECV (77% vs 68%, p = 0.01), there were no differences in 30-day death or rehospitalization rates (11.1% vs 13.0%, p = 0.37). In multivariate analyses, higher pre-ECV heart rate was associated with increased rehospitalization or death (adjusted hazard ratio 1.15/10 beats/min, 95% confidence interval 1.07 to 1.24, p <0.001), whereas TEE use was associated with lower rates (adjusted hazard ratio 0.58, 95% confidence interval 0.39 to 0.86, p = 0.007). In conclusion, failures, complications, and rehospitalization after nonemergent ECV are common and associated more with patient condition than procedural characteristics. TEE use was associated with better clinical outcomes.

[Treatment of atrial fibrillation in intensive care units and emergency departments]

BACKGROUND

Atrial fibrillation is the most common arrhythmia in patients hospitalized in intensive care units and emergency departments and is associated with an increased morbidity and mortality. In critically ill patients, atrial fibrillation can cause hemodynamic instability and cardiogenic shock. The mechanisms and the management of atrial fibrillation are significantly different in critically ill patients compared to outpatients.

DIAGNOSIS AND TREATMENT

The initial management includes the evaluation of the hemodynamic consequences of new-onset atrial fibrillation and the optimization of reversible causes. In patients with hemodynamic instability the rapid restoration of an adequate perfusion pressure is the initial goal. Often, a rapid conversion in sinus rhythm is required to achieve hemodynamic stabilization. Electrical cardioversion, if possible performed after pretreatment with an antiarrhythmic drug to increase the success rate, frequently plays a central role in the conversion to sinus rhythm of hemodynamically unstable patients. Stable patients are initially treated with a short-acting intravenous β-blocker to achieve heart rate control. A conversion to sinus rhythm may be achieved pharmacologically with vernakalant, an atrial-specific multichannel blocker.

EVALUATION

All patients with atrial fibrillation lasting more than 48 h should be evaluated for anticoagulation in order to reduce cardio-embolic complications. After recovering from the acute illness, atrial fibrillation persists only in a minority of patients.

Atrial fibrillation: effects beyond the atrium?

Atrial fibrillation (AF) is the most common sustained clinical arrhythmia and is associated with significant morbidity, mostly secondary to heart failure and stroke, and an estimated two-fold increase in premature death. Efforts to increase our understanding of AF and its complications have focused on unravelling the mechanisms of electrical and structural remodelling of the atrial myocardium. Yet, it is increasingly recognized that AF is more than an atrial disease, being associated with systemic inflammation, endothelial dysfunction, and adverse effects on the structure and function of the left ventricular myocardium that may be prognostically important. Here, we review the molecular and in vivo evidence that underpins current knowledge regarding the effects of human or experimental AF on the ventricular myocardium. Potential mechanisms are explored including diffuse ventricular fibrosis, focal myocardial scarring, and impaired myocardial perfusion and perfusion reserve. The complex relationship between AF, systemic inflammation, as well as endothelial/microvascular dysfunction and the effects of AF on ventricular calcium handling and oxidative stress are also addressed. Finally, consideration is given to the clinical implications of these observations and concepts, with particular reference to rate vs. rhythm control.

Atrial fibrillation ablation in systolic dysfunction: clinical and echocardiographic outcomes

Background

Heart failure and atrial fibrillation (AF) often coexist in a deleterious cycle.

Objective

To evaluate the clinical and echocardiographic outcomes of patients with ventricular systolic dysfunction and AF treated with radiofrequency (RF) ablation.

Methods

Patients with ventricular systolic dysfunction [ejection fraction (EF) <50%] and AF refractory to drug therapy underwent stepwise RF ablation in the same session with pulmonary vein isolation, ablation of AF nests and of residual atrial tachycardia, named "background tachycardia". Clinical (NYHA functional class) and echocardiographic (EF, left atrial diameter) data were compared (McNemar test and t test) before and after ablation.

Results

31 patients (6 women, 25 men), aged 37 to 77 years (mean, 59.8±10.6), underwent RF ablation. The etiology was mainly idiopathic (19 p, 61%). During a mean follow-up of 20.3±17 months, 24 patients (77%) were in sinus rhythm, 11 (35%) being on amiodarone. Eight patients (26%) underwent more than one procedure (6 underwent 2 procedures, and 2 underwent 3 procedures). Significant NYHA functional class improvement was observed (pre-ablation: 2.23±0.56; postablation: 1.13±0.35; p<0.0001). The echocardiographic outcome also showed significant ventricular function improvement (EF pre: 44.68%±6.02%, post: 59%±13.2%, p=0.0005) and a significant left atrial diameter reduction (pre: 46.61±7.3 mm; post: 43.59±6.6 mm; p=0.026). No major complications occurred.

Conclusion

Our findings suggest that AF ablation in patients with ventricular systolic dysfunction is a safe and highly effective procedure. Arrhythmia control has a great impact on ventricular function recovery and functional class improvement.

New-onset atrial fibrillation predicts heart failure progression

BACKGROUND

Atrial fibrillation and heart failure with reduced left ventricular ejection fraction have interrelated pathophysiologies. New-onset atrial fibrillation in heart failure patients has been associated with increased mortality, but has not been definitively related to clinical heart failure progression.

METHODS

To test the hypothesis that new-onset atrial fibrillation is related to clinical heart failure progression, in 2392 patients without atrial fibrillation at randomization in the Beta-blocker Evaluation of Survival Trial we measured clinical endpoints in patients who did (Group 1, n = 190) or did not (Group 2, n = 2202) develop new-onset atrial fibrillation. Results were also compared with the 303 patients who entered the trial in atrial fibrillation (Baseline/chronic group), and in Group 1/2 patients we conducted a multivariate analysis of covariates potentially related to time to first heart failure hospitalization.

RESULTS

Compared with Group 2, Group 1 patients post atrial fibrillation onset had a ∼2-fold increase in mortality (P < .0001) and a ∼4.5-fold increase in all-cause or heart failure hospitalization days/patient (hospitalization burden, both P < .0001). In Group 1, both types of hospitalization burden were 2.9-fold greater than in the Baseline/chronic group (P < .001), and hospitalization burden increased ∼6-fold (P < .0001) compared with the pre-event period. On multivariate analysis, new-onset atrial fibrillation was a highly significant (P < .00001) predictor of heart failure hospitalization.

CONCLUSIONS

In addition to being a discrete electrophysiologic event, in heart failure patients, new-onset atrial fibrillation is a predictor of and trigger for clinical heart failure progression.