RiskScape: A Data Visualization and Aggregation Platform for Public Health Surveillance Using Routine Electronic Health Record Data.

Automated analysis of electronic health record (EHR) data is a complementary tool for public health surveillance. Analyzing and presenting these data, however, demands new methods of data communication optimized to the detail, flexibility, and timeliness of EHR data.RiskScape is an open-source, interactive, Web-based, user-friendly data aggregation and visualization platform for public health surveillance using EHR data. RiskScape displays near-real-time surveillance data and enables clinical practices and health departments to review, analyze, map, and trend aggregate data on chronic conditions and infectious diseases. Data presentations include heat maps of prevalence by zip code, time series with statistics for trends, and care cascades for conditions such as HIV and HCV. The platform's flexibility enables it to be modified to incorporate new conditions quickly-such as COVID-19.The Massachusetts Department of Public Health (MDPH) uses RiskScape to monitor conditions of interest using data that are updated monthly from clinical practice groups that cover approximately 20% of the state population. RiskScape serves an essential role in demonstrating need and burden for MDPH's applications for funding, particularly through the identification of inequitably burdened populations.

More Screening or More Disease? Gonorrhea Testing and Positivity Patterns Among Men in 3 Large Clinical Practices in Massachusetts, 2010-2017.

BACKGROUND: Gonorrhea diagnosis rates in the United States increased by 75% during 2009-2017, predominantly in men. It is unclear whether the increase among men is being driven by more screening, an increase in the prevalence of disease, or both. We sought to evaluate changes in gonorrhea testing patterns and positivity among men in Massachusetts. METHODS: The analysis included men (aged ≥15 years) who received care during 2010-2017 in 3 clinical practice groups. We calculated annual percentages of men with ≥1 gonorrhea test and men with ≥1 positive result, among men tested. Log-binomial regression models were used to examine trends in these outcomes. We adjusted for clinical and demographic characteristics that may influence the predilection to test and probability of gonorrhea disease. RESULTS: On average, 306 348 men had clinical encounters each year. There was a significant increase in men with ≥1 gonorrhea test from 2010 (3.1%) to 2017 (6.4%; adjusted annual risk ratio, 1.12; 95% confidence interval, 1.12-1.13). There was a significant, albeit lesser, increase in the percentage of tested men with ≥1 positive result (1.0% in 2010 to 1.5% in 2017; adjusted annual risk ratio, 1.07; 95% confidence interval, 1.04-1.09). CONCLUSIONS: We estimated significant increases in the annual percentages of men with ≥1 gonorrhea test and men with ≥1 positive gonorrhea test result between 2010 and 2017. These results suggest that observed increases in gonorrhea rates could be explained by both increases in screening and the prevalence of gonorrhea.

Increased myocardial native T1 relaxation time in patients with nonischemic dilated cardiomyopathy with complex ventricular arrhythmia.

PURPOSE: To study the relationship between diffuse myocardial fibrosis and complex ventricular arrhythmias (ComVA) in patients with nonischemic dilated cardiomyopathy (NICM). We hypothesized that NICM patients with ComVA would have a higher native myocardial T1 time, suggesting more extensive myocardial diffuse fibrosis. MATERIALS AND METHODS: We prospectively enrolled NICM patients with a history of ComVA (n = 50) and age-matched NICM patients without ComVA (n = 57). Imaging was performed at 1.5T with a protocol that included cine magnetic resonance imaging (MRI) for left ventricular (LV) function, late gadolinium enhancement (LGE) for focal scar, and native T1 mapping for diffuse fibrosis assessment. RESULTS: Global native T1 time was significantly higher in patients with NICM with ComVA when compared to patients with NICM without ComVA (1131 ± 42 vs. 1107 ± 45 msec, P = 0.006), and this finding remained after excluding segments with scar on LGE (1124 ± 36 vs. 1102 ± 44 msec, P = 0.006). Native T1 was similar in NICM patients with and without the presence of LGE (1121 ± 39 vs. 1117 ± 48 msec, P = 0.68) and mildly correlated with LV end-diastolic volume index (r = 0.27, P = 0.005), LV end-systolic volume index (r = 0.24, P = 0.01), and LV ejection fraction (r = -0.28, P = 0.003). Native T1 value for each 10-msec increment was an independent predictor of ComVA (odds ratio 1.14, 95% confidence interval 1.03-1.25; P = 0.008) beyond LV function and LGE. CONCLUSION: NICM patients with ComVA have higher native T1 compared to NICM without any documented ComVA. Native myocardial T1 is independently associated with ComVA, after adjusting for LV function and LGE. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:779-786. In memoriam: The authors are grateful for Dr. Josephson's inspiring guidance and contributions to this study.

High-Resolution Mapping of Postinfarction Reentrant Ventricular Tachycardia: Electrophysiological Characterization of the Circuit.

BACKGROUND: In vivo description of ventricular tachycardia (VT) circuits is limited by insufficient spatiotemporal resolution. We used a novel high-resolution mapping technology to characterize the electrophysiological properties of the postinfarction reentrant VT circuit. METHODS: In 15 swine, myocardial infarction was induced by left anterior descending artery balloon occlusion. Animals were studied 6 to 8 weeks after myocardial infarction. Activation mapping of VTs was performed by using the Rhythmia mapping system. Activation time was based on a combination of bipolar and unipolar electrograms. The response to overdrive pacing from different zones of the circuit was examined. RESULTS: A total of 56 monomorphic VTs were induced (3.8±2.1 per animal). Among these, 21 (37.5%) were hemodynamically stable and allowed mapping of the circuit. Isthmuses were 16.4±7.2 mm long and 7.4±2.8 mm wide. Conduction velocities were slowest at the inward curvature into the isthmus entrance (0.28±0.2 m/s), slightly faster at the outward curvature exit (0.40±0.3 m/s) and nearly normal at the central isthmus (0.62±0.2 m/s). In 3 animals, 2 VT morphologies with opposite axes sharing the same isthmus were mapped. Conduction velocities within the shared isthmus were dependent on the activation vector, consistently slower at the proximal curvature. Overdrive pacing from isthmus sites determined by activation mapping was consistent with entrainment criteria for isthmus. However, dimensions of the isthmus defined by entrainment exceeded dimensions of the isthmus measured by activation mapping by 32±18%. CONCLUSIONS: In postinfarction reentrant VT, conduction velocities are slowest at the proximal and distal curvatures. Entrainment mapping overestimates the true size of the isthmus. High-resolution activation mapping of VT may better guide ablation therapy.

Global Electric Heterogeneity Risk Score for Prediction of Sudden Cardiac Death in the General Population: The Atherosclerosis Risk in Communities (ARIC) and Cardiovascular Health (CHS) Studies.

BACKGROUND: Asymptomatic individuals account for the majority of sudden cardiac deaths (SCDs). Development of effective, low-cost, and noninvasive SCD risk stratification tools is necessary. METHODS AND RESULTS: Participants from the Atherosclerosis Risk in Communities study and Cardiovascular Health Study (n=20 177; age, 59.3±10.1 years; age range, 44-100 years; 56% female; 77% white) were followed up for 14.0 years (median). Five ECG markers of global electric heterogeneity (GEH; sum absolute QRST integral, spatial QRST angle, spatial ventricular gradient [SVG] magnitude, SVG elevation, and SVG azimuth) were measured on standard 12-lead ECGs. Cox proportional hazards and competing risks models evaluated associations between GEH electrocardiographic parameters and SCD. An SCD competing risks score was derived from demographics, comorbidities, and GEH parameters. SCD incidence was 1.86 per 1000 person-years. After multivariable adjustment, baseline GEH parameters and large increases in GEH parameters over time were independently associated with SCD. Final SCD risk scores included age, sex, race, diabetes mellitus, hypertension, coronary heart disease, stroke, and GEH parameters as continuous variables. When GEH parameters were added to clinical/demographic factors, the C statistic increased from 0.777 to 0.790 (P=0.008), the risk score classified 10-year SCD risk as high (>5%) in 7.2% of participants, 10% of SCD victims were appropriately reclassified into a high-risk category, and only 1.4% of SCD victims were inappropriately reclassified from high to intermediate risk. The net reclassification index was 18.3%. CONCLUSIONS: Abnormal electrophysiological substrate quantified by GEH parameters is independently associated with SCD in the general population. The addition of GEH parameters to clinical characteristics improves SCD risk prediction.

Catheter Ablation of Atypical Atrioventricular Nodal Reentrant Tachycardia.

BACKGROUND: Because of its low prevalence, data on atypical atrioventricular nodal reentrant tachycardia (AVNRT) are scarce, and the optimal ablation method has not been established. Our study aimed at assessing the efficacy and safety of conventional slow pathway ablation, as applied for typical cases, in atypical AVNRT. METHODS: We studied 2079 patients with AVNRT subjected to slow pathway ablation. In 113 patients, mean age 48.5±18.1 years, 68 female, atypical AVNRT or coexistent atypical and typical AVNRT without other concomitant arrhythmia was diagnosed. Ablation data and outcomes were compared with a group of age- and sex-matched control patients with typical AVNRT. RESULTS: Fluoroscopy and radiofrequency current delivery times were not different in the atypical and typical groups, 20.3±12.2 versus 20.8±12.9 minutes (P=0.730) and 5.9±5.0 versus 5.5±4.5 minutes (P=0.650), respectively. Slow pathway ablation was accomplished from the right septum in 110 patients, and from the left septum in 3 patients, in the atypical group. There was no need for additional ablation lesions at other anatomic sites, and no cases of atrioventricular block were encountered. Recurrence rates of the arrhythmia were 5.6% in the atypical (6/108 patients) and 1.8% in the typical (2/111 patients) groups in the next 3 months following ablation (P=0.167). CONCLUSIONS: Conventional ablation at the anatomic area of the slow pathway is the therapy of choice for symptomatic AVNRT, regardless of whether the typical or atypical form is present.

Interlead heterogeneity of R- and T-wave morphology in standard 12-lead ECGs predicts sustained ventricular tachycardia/fibrillation and arrhythmic death in patients with cardiomyopathy.

INTRODUCTION: Nonuniformities in depolarization and repolarization morphology are critical factors in ventricular arrhythmogenesis. METHODS AND RESULTS: We assessed interlead R-wave heterogeneity (RWH) and T-wave heterogeneity (TWH) in standard 12-lead electrocardiograms (ECGs) using second central moment analysis. This technique quantifies variance about the mean morphology of beats in adjoining precordial leads, V4 , V5 , and V6 in this study. The study was conducted in 120 consecutive patients without an apparent reversible trigger for ventricular tachycardia (VT), recent myocardial infarction, or active ischemia, who presented for electrophysiologic study, implantable cardioverter defibrillator (ICD) placement, or generator change at our institution from 2008 to 2011. Primary outcome was sustained VT/ventricular fibrillation (VF) or appropriate ICD therapies. Secondary outcome was arrhythmic death or resuscitated cardiac arrest. Cutpoints for elevated RWH (>160 µV) and TWH (>80 µV) identified 67% of primary outcome cases and 85% of secondary outcome cases. Cardiomyopathy patients who met the primary outcome (n = 42) had significantly higher TWH than those who did not (n = 28) (TWH: 95 ± 11 µV vs. 44 ± 9 µV, P < 0.002). Likewise, cardiomyopathy patients who met secondary outcome (N = 13) had VT/VF during follow-up and also had significantly higher TWH than survivors (N = 57) (TWH: 105 ± 24 µV vs. 67 ± 8 µV, P < 0.002). Kaplan-Meier analysis revealed significant differences in arrhythmia-free survival (P = 0.012) and total survival (P = 0.011) among cardiomyopathy patients with (n = 37) compared to without (n = 33) elevated RWH and/or TWH independent of age, sex, and left ventricular ejection fraction (LVEF). CONCLUSION: Interlead RWH and TWH in 12-lead ECGs predict sustained ventricular arrhythmia, appropriate ICD therapies, and arrhythmic death or cardiac arrest in cardiomyopathy patients independent of LVEF and other standard variables.

State and Local Chronic Disease Surveillance Using Electronic Health Record Systems.

OBJECTIVES: To assess the feasibility of chronic disease surveillance using distributed analysis of electronic health records and to compare results with Behavioral Risk Factor Surveillance System (BRFSS) state and small-area estimates. METHODS: We queried the electronic health records of 3 independent Massachusetts-based practice groups using a distributed analysis tool called MDPHnet to measure the prevalence of diabetes, asthma, smoking, hypertension, and obesity in adults for the state and 13 cities. We adjusted observed rates for age, gender, and race/ethnicity relative to census data and compared them with BRFSS state and small-area estimates. RESULTS: The MDPHnet population under surveillance included 1 073 545 adults (21.8% of the state adult population). MDPHnet and BRFSS state-level estimates were similar: 9.4% versus 9.7% for diabetes, 10.0% versus 12.0% for asthma, 13.5% versus 14.7% for smoking, 26.3% versus 29.6% for hypertension, and 22.8% versus 23.8% for obesity. Correlation coefficients for MDPHnet versus BRFSS small-area estimates ranged from 0.890 for diabetes to 0.646 for obesity. CONCLUSIONS: Chronic disease surveillance using electronic health record data is feasible and generates estimates comparable with BRFSS state and small-area estimates.

Catheter ablation vs. antiarrhythmic drug therapy in patients with symptomatic atrioventricular nodal re-entrant tachycardia: a randomized, controlled trial.

AIMS: To conduct a randomized trial in order to guide the optimum therapy of symptomatic atrioventricular nodal re-entrant tachycardia (AVNRT). METHODS AND RESULTS: Patients with at least one symptomatic episode of tachycardia per month and an electrophysiologic diagnosis of AVNRT were randomly assigned to catheter ablation or chronic antiarrhythmic drug (AAD) therapy with bisoprolol (5 mg od) and/or diltiazem (120-300 mg od). All patients were properly educated to treat subsequent tachycardia episodes with autonomic manoeuvres or a 'pill in the pocket' approach. The primary endpoint of the study was hospital admission for persistent tachycardia cardioversion, during a follow-up period of 5 years. Sixty-one patients were included in the study. In the ablation group, 1 patient was lost to follow-up, and 29 were free of arrhythmia or conduction disturbances at a 5-year follow-up. In the AAD group, three patients were lost to follow-up. Of the remainder, 10 patients (35.7%) continued with initial therapy, 11 patients (39.2%) remained on diltiazem alone, and 7 patients (25%) interrupted their therapy within the first 3 months following randomization, and subsequently developed an episode requiring cardioversion. During a follow-up of 5 years, 21 patients in the AAD group required hospital admission for cardioversion. Survival free from the study endpoint was significantly higher in the ablation group compared with the AAD group (log-rank test, P < 0.001). CONCLUSIONS: Catheter ablation is the therapy of choice for symptomatic AVNRT. Antiarrhythmic drug therapy is ineffective and not well tolerated.

Paroxysmal atrioventricular block: Electrophysiological mechanism of phase 4 conduction block in the His-Purkinje system: A comparison with phase 3 block.

BACKGROUND: Paroxysmal atrioventricular (A-V) block is relatively rare, and due to its transient nature, it is often under recognized. It is often triggered by atrial, junctional, or ventricular premature beats, and occurs in the presence of a diseased His-Purkinje system (HPS). Here, we present a 45-year-old white male who was admitted for observation due to recurrent syncope and near-syncope, who had paroxysmal A-V block. The likely cellular electrophysiological mechanisms(s) of paroxysmal A-V block and its differential diagnosis and management are discussed. METHODS: Continuous electrocardiographic monitoring was done while the patient was in the cardiac unit. RESULTS: Multiple episodes of paroxysmal A-V block were documented in this case. All episodes were initiated and terminated with atrial/junctional premature beats. The patient underwent permanent pacemaker implantation and has remained asymptomatic since then. CONCLUSIONS: Paroxysmal A-V block is rare and often causes syncope or near-syncope. Permanent pacemaker implantation is indicated according to the current guidelines. Paroxysmal A-V block occurs in the setting of diseased HPS and is bradycardia-dependent. The detailed electrophysiological mechanisms, which involve phase 4 diastolic depolarization, and differential diagnosis are discussed.

Concordance Between Common Hypertension Control Algorithms in Electronic Medical Record Data.

Because quality improvement metrics and treatment guidelines are used to conduct research, evaluate care quality, and assess population health, they should, ideally, align. We used electronic medical record data to analyze variation between blood pressure control estimates calculated by using thresholds derived from National Quality Forum 0018 (NQF 0018) and Joint National Committee (JNC) treatment guidelines in a cohort of patients with hypertension. Percentage of patients with controlled blood pressure derived from each quality improvement or treatment guideline cutoff varied up to 16.1 percentage points. This variance demonstrates that discrepancies in blood pressure thresholds produce considerable variation in estimates; thus, treatment guidance and metrics should be selected carefully.

Incidence and risk factors for symptomatic heart failure after catheter ablation of atrial fibrillation and atrial flutter.

AIMS: To determine the incidence and risk factors for development of symptomatic heart failure (HF) following catheter ablation for atrial fibrillation (AF) and atrial flutter. METHODS AND RESULTS: We prospectively enrolled consecutive patients undergoing pulmonary vein isolation (PVI) or cavotricuspid isthmus (CTI) ablation between November 2013 and June 2014. Post-discharge symptoms were assessed via telephone follow-up and clinic visits. The primary outcome was symptomatic HF requiring treatment with new/increased diuretic dosing. Secondary outcomes were prolonged index hospitalization and readmission for HF ≤30 days. Univariate and multivariable logistic regressions were used to assess the relationship between patient/procedural characteristic and post-ablation HF. Among 111 PVI patients [median age 62.0 years; left ventricular ejection fraction (LVEF) 55%], 29 patients (26.1%) developed symptomatic HF, 6 patients (5.4%) required prolonged index hospitalization, and 8 patients (7.2%) were readmitted for HF. In univariate analyses, persistent AF [odds ratio (OR) 2.97, P = 0.02], AF at start of the procedure (OR 2.99, P = 0.01), additional ablation lines (OR 11.07, P < 0.0001), and final left atrial pressure (OR 1.10 per 1 mmHg increase, P = 0.02) were associated with HF development. Peri-procedural diuresis, net fluid balance, and LVEF were not correlated. In multivariable analyses, only additional ablation lines (ORadj 9.17, P = 0.007) were independently associated with post-ablation HF. Six patients (16.7%) developed HF after CTI ablation. CONCLUSION: A 26.1% of patients undergoing PVI and 16.7% of patients undergoing CTI ablation developed symptomatic HF when prospectively and uniformly assessed. 12.6% of patients experienced prolonged index hospitalizations or readmission for management of HF within 1 week after PVI. Improved understanding of risk factors for post-ablation HF may be critical in developing strategies to address during AF ablation.

Quantitative Assessment of Vectorcardiographic Loop Morphology.

Vectorcardiography (VCG), developed 100years ago, characterizes clinically important electrophysiological properties of the heart. In this study, VCG QRS loop roundness, planarity, thickness, rotational angle, and dihedral angle were measured in 81 healthy control subjects (39.0±14.2y; 51.8% male; 94% white), and 8 patients with infarct-cardiomyopathy and sustained monomorphic ventricular tachycardia (VT) (68.0±7.8y, 37.5% male). The angle between two consecutive QRS vectors was defined as the rotational angle, while dihedral angle quantified planar alteration over the QRS loop. In VT subjects, planarity index decreased (0.63±0.22 vs. 0.88±0.10; P=0.014), and dihedral angle was significantly more variable (variance of dihedral angle, median (IQR): 897(575-1450) vs. 542(343-773); P=0.029; rMSSD: 47.7±12.7 vs. 35.1±13.1; P=0.027). Abnormal electrophysiological substrate in VT patients is characterized by the appearance of QRS loop folding, likely due to local conduction block. The presence of fragmented QRS complexes on the 12-lead ECG had low sensitivity (31%) for detecting QRS loop folding on the VCG.

Prognostic value of pulmonary vein size in prediction of atrial fibrillation recurrence after pulmonary vein isolation: a cardiovascular magnetic resonance study.

BACKGROUND: The relationship between pulmonary vein (PV) anatomy and successful catheter ablation of atrial fibrillation (AF) is poorly understood METHODS: First-pass contrast enhanced PV magnetic resonance angiography was performed in 71 consecutive patients prior to PV isolation. PV diameter and cross-sectional area (CSA) were measured prior to PV isolation. Any symptomatic or asymptomatic AF >10s was considered a recurrence. Early recurrence was defined as recurrent AF ≤30 days after PV isolation, while late recurrence of AF was defined as recurrent AF >30 days after. RESULTS: At 1 year, 57% had any recurrence of AF while 41% had late recurrence of AF. Study subjects with one or more PV diameter in the top 10(th) percentile had trend toward more early recurrent AF (HR 1.99, p = 0.053). Study subjects with one or more PV CSA in the top 10th percentile had more late recurrent AF (HR 2.25, p = 0.039) and a trend toward more early recurrent AF (HR 1.94, p = 0.064). With multivariate analysis, PV size was not associated with early recurrent AF, but late recurrent AF was associated with one or more large PV, increased left atrial size, and non-paroxysmal AF. Study subjects with all three of these risk factors had a 100% rate of late recurrent AF at 1 year, while those with none had a 7% rate of late recurrent AF. CONCLUSIONS: Larger PV size is independently associated with more late recurrent AF after PV isolation. Determination of PV size prior to PV isolation may predict procedural success.

Comparison between single- and multi-sensor oesophageal temperature probes during atrial fibrillation ablation: thermodynamic characteristics.

AIMS: Oesophageal temperature monitoring with single-sensor probe (SSP) has a variable ability to predict oesophageal ulceration as a consequence of pulmonary vein isolation (PVI). Multi-sensor self-expandable probes (MSPs) may offer improved thermal monitoring. The objective of this study was to compare the thermodynamic characteristics of both probes during PVI. METHODS AND RESULTS: This prospective study enrolled 20 patients undergoing index PVI. Ten patients (group A) underwent dual monitoring with SSP and MSP and 10 control patients (group B) were monitored with SSP alone. Time to initial rise (>0.2°C), time to 1.0°C rise, peak temperature, and decay were recorded with each posterior wall lesion (20 W, 198 applications). The operator was blinded to the MSP temperature data and ablation was only interrupted when SSP temperature increased by ≥2°C. All patients underwent endoscopy within 24 h. Initial temperature increase was detected earlier with MSP (13.4 ± 7.5 vs. 30.5 ± 15.4 s; P < 0.001); led to shorter time to 1.0°C rise (18.5 ± 10.1 vs. 32.1 ± 12.0 s; P < 0.001); and higher change in peak temperature (1.6 ± 2.0 vs. 0.60 ± 0.53°C; P < 0.001). Decay time was similar between the probes (146.1 ± 35.3 vs. 150.4 ± 48.4 s; P = 0.89). The incidence of oesophageal ulceration was similar between the Groups A and B (5 and 4, respectively). Multi-sensor self-expandable probe provided greater sensitivity (100 vs. 60%) and similar specificity (60%) for detection of oesophageal ulceration. Five swine underwent oesophageal mapping before and after MSP placement without alteration in size or position. CONCLUSION: Multi-sensor probes provide a superior thermodynamic profile. Its clinical value in reducing oesophageal injury requires further evaluation.

Atypical atrioventricular nodal reentrant tachycardia: prevalence, electrophysiologic characteristics, and tachycardia circuit.

AIMS: This study aimed at assessing the prevalence, electrophysiologic characteristics, and mechanism of atypical atrioventricular nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS: We studied 925 consecutive patients with AVNRT. Atrial-His (AH) and His-atrial (HA) intervals were measured during atypical AVNRT (HA > 70 ms), and compared with measurements in 34 patients with typical (slow-fast) AVNRT. Assuming that conduction velocity over the fast pathway is similar in the anterograde and retrograde directions, the AH interval during the fast-slow form should be smaller than the HA during slow-fast. Atypical AVNRT was diagnosed in 59 patients (6.4%), median age 50 years (range 19-79 years), and 37 (59.7%) of them female. Fast-slow AVNRT was diagnosed in 44 patients (74.5%), and slow-slow AVNRT in 9 patients (15.2%). The remaining six patients (10.2%) could not be reliably classified due to inconsistent AH, and HA/AH patterns or variable intervals. Tachycardia induction with anterograde conduction jumps was seen in two patients with the fast-slow, and in three patients with slow-slow or intermediate forms. Atrial-His in the fast-slow group was significantly longer than HA in the slow-fast group, 99.7 ± 40.5 ms vs. 45.8 ± 7.7 ms, P < 0.001. Tachycardia cycle length was longer in fast-slow compared with slow-fast, 379.1 ± 68.5 ms vs. 317.1 ± 42.8 ms, P < 0.001. CONCLUSION: Of AVNRT cases, 6.4% are atypical and may display patterns that do not necessarily correspond to the fast-slow or slow-slow conventional types. Atypical fast-slow and typical AVNRT do not appear to utilize the same limb for fast conduction.

Frequency content and characteristics of ventricular conduction.

The spectrum of frequencies producing the QRS complex has not been fully explored. In this manuscript we review previous studies of QRS frequency content, and discuss our novel method of the conjoint analysis of the ECG signal in six dimensions: in the domain of three space dimensions, in time domain, and in frequency domain. Orbital frequency of QRS loop is introduced as a six-dimensional characteristic of ventricular conduction, which helped to reveal inapparent ventricular conduction, and to characterize electrophysiological substrate. In this paper, we review our novel method in the historical context.

Idiopathic ventricular fibrillation originating from the moderator band.

We report a case of a 59-year-old man with idiopathic ventricular fibrillation storm. Ventricular fibrillation was pause-dependent and triggered by an early-coupled right ventricular premature complex. The characteristic premature beat was mapped and successfully ablated from Purkinje fibers of the moderator band.