<< First issue in April 2021 >>
Come and listen to the editor in chief to introduce the most authoritative international heart rhythm research results
Peng-Sheng Chen
The first 4 papers related to COVID-19 and heart rhythm disorders. The first original article is titled “Atrial Fibrillation is an Independent Predictor for In-hospital mortality in Patients Admitted with SARS-CoV-2 Infection”. AF occurred in 1687 of 9564 patients (17.6%). Of those, 1109 patients (65.7%) had new-onset AF. There was a higher in-hospital mortality in the AF group than control. Within the AF group, there was higher in-hospital mortality in patients with new-onset AF as compared with those with a history of AF. The risk ratio of in-hospital mortality for new-onset AF in patients with sinus rhythm was 1.56. The authors conclude that in patients hospitalized with COVID-19, 17.6% experienced AF. AF, particularly new-onset, was an independent predictor of in-hospital mortality. This paper was followed by a Viewpoint article titled “The possible association between COVID-19 and postural orthostatic tachycardia syndrome” and an editorial on COVID-19 infection and heart rhythm disorders.
Up next is “Insulin-Like Growth Factor-Binding Protein-7 and risk of congestive heart failure hospitalization in patients with atrial fibrillation”. Insulin-like growth factor-binding protein 7 (IGFBP-7) is a marker of myocardial damage. The authors analyzed 2 prospective multicenter observational cohort studies that included 3691 AF patients. Levels of IGFBP-7 and NT-proBNP levels were measured from frozen plasma samples at baseline. The authors found that higher plasma levels of IGFBP-7 were strongly and independently associated with CHF hospitalization in AF patients. The prognostic information provided by IGFBP-7 was additive to that of NT-proBNP.
The following article is titled “Self-reported Physical Activity and Atrial Fibrillation Risk: A Systematic Review and Meta-analysis”. The authors analyzed 15 studies reporting data from 1.5 million individuals with a median age of 55.3 years. Individuals achieving guidelinerecommended level of physical activity had a significantly lower risk of AF with a hazard ratio of 0.94. Dose-response analysis showed that physical activity levels up to 1900 MET-minutes per week were associated with a lower risk of AF, with less certainty beyond that level. The authors conclude that physical activity at guideline-recommended levels and above are associated with a significantly lower AF risk. However, at 2000 MET-minutes per week and beyond, the benefit is less clear.
The next article is “Marshall bundle elimination, Pulmonary vein isolation, and Line completion for ANatomical ablation of persistent atrial fibrillation (Marshall-PLAN): Prospective, single-center study”. These studies were done strictly based on anatomical considerations. The authors included 75 consecutive patients. Vein of Marshall (VOM) ethanol infusion was completed in 69 patients (92%). At 12 months, 54 of 75 patients (72%) were free from AF/AT after a single procedure and without antiarrhythmic drugs in the overall cohort. The authors conclude that a novel ablation strategy that systematically targets anatomical atrial structures (VOM ethanol infusion, PVI, and prespecified linear lesions) is feasible, safe, and associated with a high rate of freedom from arrhythmia recurrence at 12 months in patients with persistent AF.
Following that article is one titled “The Decrease in Peak Atrial Longitudinal Strain in Patients with Atrial Fibrillation as a Practical Parameter for Stroke Risk Stratification”.Background: Decreased peak atrial longitudinal strain (LA strain) derived from 2-dimensional speckle tracking is frequently observed in patients with AF and associated with the risk of ischemic stroke. The authors studied 1364 subjects with AF. Among them, 105 encountered ischemic strokes during a mean follow-up period of 3 years. The standard score of LA strain was calculated and classified into 5 groups. The clinical end point was an ischemic stroke. The Kaplan-Meier analysis showed higher rates of stroke in worse LA strain groups. These data suggest that the decrease in LA strain could be applied in a stratified manner and is significantly associated with the risk of stroke independent of the baseline covariates.
Coming up next is “Catheter Ablation of Ventricular Arrhythmias in Left Ventricular NonCompaction Cardiomyopathy”. Forty-two nonrelated patients with left ventricular noncompaction (LVNC) and ventricular arrhythmias were included. Thirteen patients (31%) had isolated LVNC, 27 (64%) had LVNC associated with dilated cardiomyopathy, and 2 (5%) had LVNC associated with hypertrophic cardiomyopathy. Most patients have PVCs and VTs. Endocardial mapping and ablation were performed in 19 patients (45.2%) and epicardial ablation was performed in 3 cases. The authors found that the substrate of ventricular arrhythmias in LVNC cardiomyopathy is heterogeneous, with origin in ventricular outflow tracts, Purkinje system related, and resembling scar patterns in nonischemic cardiomyopathy.
The next one is titled “Temperature and flow controlled ablation / very high-power shortduration ablation vs Conventional power-controlled ablation: Comparison of focal and linear lesion characteristics”. Lesion characteristics in the right atrium, left atrium, and right ventricle (RV) of 6 sheep were compared between very-high-power short-duration (90 W/4 seconds) and standard radiofrequency settings (30 W/30 seconds). Lesions in the left ventricle (LV) were compared, targeting 50 W for 60-second applications. The authors found that temperature and flow controlled very-high-power short-duration ablation produces larger, shallower, more homogeneous, and less hemorrhagic lesions. Very-high-power short-duration ablation produces more transmural and contiguous linear lesions compared to power controlled ablation. They also found that LV lesions are more homogeneous with fewer steam pops in temperature and flow controlled ablation.
Up next is “Fixation beats: a novel marker for reaching the left bundle branch area during deep septal lead implantation.” The fixation beats are the ectopic beats with qR/rsR' morphology in lead V1 during lead fixation would predict whether the desired intraseptal lead depth had been reached, whereas the lack of fixation beats would indicate a too-shallow position and the need for more lead rotations. A total of 339 patients and 1278 lead rotation events were analyzed. In the retrospective phase, fixation beats were observed in 327 of 339 final lead positions and in 9 of 939 intermediate lead positions. Sensitivity, specificity, and positive and negative predictive values of the fixation beats as a marker for reaching the LBB area were around 96-97%. In the prospective, fixation beats-guided implantation phase, fixation beats were observed in all patients and only at the LBB capture depth. The authors conclude that monitoring fixation beats during deep septal lead deployment can facilitate the procedure and possibly increase the safety of lead implantation.
The next article is titled “Systematic Quantification of Histological Ventricular Fibrosis in Isolated Mitral Valve Prolapse and Sudden Cardiac Death.” The purpose of this study was to systematically quantify left and right ventricular fibrosis in individuals with isolated mitral valve prolapse (MVP) and sudden cardiac death. They found 17 cases and 17 matched controls. The mitral valve prolapse and sudden cardiac death group had increased LV and interventricular septum fibrosis but similar amounts of RV fibrosis compared to controls. The authors conclude that nonuniform left ventricular remodeling with both localized and generalized left ventricular fibrosis is important in the pathogenesis of SCD in individuals with mitral valve prolapse.
Up next is “Prognostic Value of Cardiac Magnetic Resonance Septal Late Gadolinium Enhancement Patterns for Periaortic Ventricular Tachycardia Ablation: Heterogeneity of the Anteroseptal Substrate in Nonischemic Cardiomyopathy.” Among 234 patients referred for scar-related VT ablation between 2017 and 2020, 25 patients and a total of 108 VTs were analyzed. A greater number of VT morphologies were induced in patients with full-length septal late gadolinium enhancement (LGE) compared to partial septal LGE. Patients with VT recurrence had larger septal LGE volumes compared to those without. At median follow-up of 16 months, overall freedom from VT recurrence was 52% and significantly higher in patients with partial septal LGE than in those with full-length septal LGE. The authors conclude that VT originating from an anteroseptal substrate is associated with heterogeneous patterns and extent of CMR septal scar. Preprocedural imaging may substratify this challenging patient population for the propensity for multiple induced VT morphologies and recurrence after catheter ablation.
That paper is followed by another paper on myocardial scar, titled “Prior myocarditis and ventricular arrhythmias: the importance of scar pattern”. This was a retrospective study of consecutive 144 patients with prior myocarditis and arrhythmic presentation. Anteroseptal scar was present in 44% of cases. Sixty-one patients (42%) underwent catheter ablation. The presence of anteroseptal scar was found to be an independent predictor of ventricular arrhythmia relapse both in patients treated with catheter ablation and in the overall population. The authors conclude that in patients with prior myocarditis and ventricular arrhythmia, the presence of anteroseptal scar negatively predicts outcomes irrespective of treatment strategy.
Next up is “Etiology and prognosis of patients with unexplained syncope and mid-range left ventricular dysfunction”. One hundred four patients were prospectively followed for 2 years. In 71 patients (68.3%), a diagnosis was reached. Arrhythmic causes were the most common etiology (45.2% AV block and 9.6% ventricular tachycardia). The mortality rate was 8.1% person-years, and the sudden or unknown death rate was 0.9% person-year. These finding indicate that in patients with mid-range left ventricular dysfunction and syncope of unknown cause, a systematic diagnostic strategy based on electrophysiology study and/or implantable cardiac monitor implantation allows a diagnosis to be reached in a high proportion of cases and guides the treatment. Arrhythmia is the most common cause of syncope in this population, particularly AV block.
The next article is “Twin Atrioventricular Nodes, Arrhythmias and Survival in Pediatric and Adult Patients with Heterotaxy Syndrome”. Of the 366 heterotaxy patients enrolled, 326 (89.1%) had right atrial isomerism (RAI), 35 (9.6%) had left atrial isomerism (LAI) and 5 (1.4%) had indeterminate isomerism; 71 (19.4%) patients were adults. Arrhythmias occurred in 37.2% of patients, most of them with supraventricular tachycardia. Twin AV nodes were identified in 51.5% of patients with RAI, 8.7% of patients with LAI, and 40.0% of patients with indeterminate isomerism and were the key predictors of SVT. The authors conclude that RAI was the predominant subtype of heterotaxy in this cohort. Collectively, the median RAI/LAI ratio was 0.731 and 5.450 in Western and East Asian studies, respectively. Arrhythmias, tachycardia, or paced bradycardia were common, but the spectrum was distinct among subtypes.
Up next is “The electrophysiological effects of ranolazine in a goat model of lone atrial fibrillation”. Ranolazine is an antiarrhythmic drug reported to have strong atrial selectivity. Electrode patches were implanted on the atrial epicardium of 8 Dutch milk goats. Experiments were performed at baseline and after 2 and 14 days of electrically maintained AF. Ranolazine significantly prolonged atrial effective refractory period and decreased atrial conduction velocity at baseline and after 2 days of AF. After 2 weeks of AF, ranolazine prolonged the AF cycle length but was not effective in restoring sinus rhythm. The authors conclude that high dose of ranolazine affected both atrial and ventricular EP parameters at different stages of AF-induced remodeling but was not efficacious in cardioverting AF to sinus rhythm in a goat model of lone AF.
The following paper is “High-Intensity Ultrasound Catheter Ablation Achieves Deep, MidMyocardial Lesions In-Vivo”. Irrigated 12F ultrasound catheters were tested in an ex vivo perfused swine myocardial ablation model. Maximal lesion depth and volume was achieved by 6.5 MHz catheters. Lesion depth by gross pathology was similar post-ablation and at 30 days. Lesion volume decreased postablation to 30 days, yet transmurality increased from 58% to 81%. Magnetic resonance imaging confirmed dense septal ablation by delayed enhancement, with increased T1 time post-ablation and at 30 days and increased T2 time only post-ablation. The authors conclude that high-intensity ultrasound catheter ablation may be an effective treatment of mid-myocardial or epicardial ventricular arrhythmias from an endocardial approach.
Up next is “Identification of two preclinical canine models of atrial fibrillation to facilitate drug discovery”. The purpose of this study was to provide a comprehensive head-to-head assessment of 5 canine AF models. Careful evaluation showed that acute atrial tachypacing, atrial tachypacing for 4 weeks, and the heart failure model all were unsuccessful in generating reproducible AF episodes of sufficient duration to study antiarrhythmic drugs. In contrast, intermittent long-term atrial tachypacing generated AF lasting ≥4.5 hours in ∼30% of animals. The acute model using carbachol and short-term atrial tachypacing resulted in AF induction of ≥15 minutes in ≥75% of animals, thus enabling testing of antiarrhythmic drugs. The authors conclude that intermittent long-term atrial tachypacing and the combination of local carbachol injection with successive short-term atrial tachypacing may contribute to future drug development efforts for AF treatment.
These above original articles are followed by a contemporary review titled“Current Strategies to Minimize Postoperative Hematoma Formation in Patients Undergoing Cardiac Implantable Electronic Device Implantation: A Review”. Dr Fred Morady wrote a Viewpoint titled “The Diagnosis and Cure of Supraventricular Tachycardia” as the 4th entry in our series of articles to celebrate the 30th year of RF ablation.
I hope you enjoyed this podcast. For Heart Rhythm, I’m the Editor-In-Chief, Dr. Peng-Sheng Chen.
