[High-degree atrioventricular (AV) block]

In elderly patients high-degree atrioventricular (AV) block is often due to irreversible degeneration of the cardiac conduction system. Reversible causes must however be excluded prior to pacemaker implantation. In younger patients reversible causes are more likely, as well as more unusual etiologies. Lyme carditis is a rare, but reversible cause of AV block. It is a manifestation of Lyme borreliosis - an infectious disease caused by the bacteria Borrelia burgdorferi. Lyme carditis should particularly be considered in young and middle-aged patients with a high-degree AV block. When pretest probability is intermediate to high, a positive serological test makes the diagnosis of Lyme carditis highly likely. In these cases antibiotic treatment may revert the conduction disturbance, thus preventing unnecessary implantation of a permanent pacemaker.

[Esophageal-ECG in the emergency department]

The management of tachycardias depends on their underlying pathophysiology. The key to uncovering this pathophysiology is in finding the temporal relationship between atrial and ventricular activation. The P-waves resulting from atrial activation can however be hard to detect on a traditional EKG in the setting of a tachycardia. Esophageal-EKG can help reveal the P-waves. The patient swallows an electrode, whose position in the esophagus is then adjusted to maximize the signal coming from the left atrium, clearly revealing atrial activity. This article describes the indications and contraindications for esophageal-EKG, as well as how it is performed and interpreted. Esophageal-EKG is of particular diagnostic value in the setting of a regular tachycardia with wide QRS complexes and no obvious signs of atrio-ventricular dissociation. In this setting, the esophageal-EKG can distinguish between ventricular tachycardia and a supraventricular tachycardia with aberrant conduction.

Cryoablation as standard treatment of atrial flutter: a prospective, 2-center study (CASTAF)

BACKGROUND

Cryoablation (CRYO) of cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) has been shown to be non-inferior to radiofrequency ablation (RF) in terms of ablation success and is associated with less pain. However, procedural time has been significantly longer with CRYO compared to RF. A possible explanation for this could be that operators had less experience with CRYO than with RF. The purpose of this study was to test the hypothesis that in the hands of experienced operators, cryoablation of CTI-dependent AFL is effective with procedure-time similar to what is reported for RF.

METHODS

This prospective 2-center study included 184 patients with CTI-dependent AFL - median age 66 years (range 28-83), 159 men (86%). Cryoablation was performed using a 9 F, 8 mm tip catheter (Freezor MAX, Medtronic, Inc, MN, USA). Ablation endpoint was bidirectional CTI-block. Pain was evaluated with a visual analogue scale (VAS 0-10). All operators had experience of at least 25 previous CTI-ablations with CRYO.

RESULTS

The acute success rate was 89%. Procedural time including an observation period of 30 min, was 115 ± 36 min which is similar to procedural times for RF in previous studies. Fluoroscopy time was 11 ± 9 min. Cryoablation was perceived as almost pain- free by the patients, VAS (mean) 1.8 ± 1.2. Success rate at 12-month follow-up (FU) was 88% in patients with primary success. No major adverse events occurred.

CONCLUSIONS

Cryoablation of CTI-dependent AFL is effective, with a low level of procedure-related pain. In experienced hands, the procedure time in this prospective non-randomised trial seems to be in the level of reported procedure times for RF. The long-term relapse rate appears to be higher than for RF.

Erroneous computer-based interpretations of atrial fibrillation and atrial flutter in a Swedish primary health care setting

Objective: To describe the incidence of incorrect computerized ECG interpretations of atrial fibrillation or atrial flutter in a Swedish primary care population, the rate of correction of computer misinterpretations, and the consequences of misdiagnosis.Design: Retrospective expert re-analysis of ECGs with a computer-suggested diagnosis of atrial fibrillation or atrial flutter.Setting: Primary health care in Region Kronoberg, Sweden.Subjects: All adult patients who had an ECG recorded between January 2016 and June 2016 with a computer statement including the words 'atrial fibrillation' or 'atrial flutter'.Main outcome measures: Number of incorrect computer interpretations of atrial fibrillation or atrial flutter; rate of correction by the interpreting primary care physician; consequences of misdiagnosis of atrial fibrillation or atrial flutter.Results: Among 988 ECGs with a computer diagnosis of atrial fibrillation or atrial flutter, 89 (9.0%) were incorrect, among which 36 were not corrected by the interpreting physician. In 12 cases, misdiagnosed atrial fibrillation/flutter led to inappropriate treatment with anticoagulant therapy. A larger proportion of atrial flutters, 27 out of 80 (34%), than atrial fibrillations, 62 out of 908 (7%), were incorrectly diagnosed by the computer.Conclusions: Among ECGs with a computer-based diagnosis of atrial fibrillation or atrial flutter, the diagnosis was incorrect in almost 10%. In almost half of the cases, the misdiagnosis was not corrected by the overreading primary-care physician. Twelve patients received inappropriate anticoagulant treatment as a result of misdiagnosis.Key pointsData regarding the incidence of misdiagnosed atrial fibrillation or atrial flutter in primary care are lacking. In a Swedish primary care setting, computer-based ECG interpretations of atrial fibrillation or atrial flutter were incorrect in 89 of 988 (9.0%) consecutive cases.Incorrect computer diagnoses of atrial fibrillation or atrial flutter were not corrected by the primary-care physician in 47% of cases.In 12 of the cases with an incorrect computer rhythm diagnosis, misdiagnosed atrial fibrillation or flutter led to inappropriate treatment with anticoagulant therapy.

Pheochromocytoma - An ECG diagnosis?

Pheochromocytoma is a rare catecholamine-secreting tumor in the adrenal medulla. In some cases, the first symptoms are cardiovascular. We report on two patients with pheochromocytoma, who both presented with bidirectional ventricular tachycardia (BDVT). We elaborate on the mechanisms of BDVT in the setting of pheochromocytoma.

Combination of a leadless pacemaker and subcutaneous defibrillator with nine effective shock treatments during follow-up of 18 months

We present a case of combination of a leadless pacemaker (Micra) and a subcutaneous implantable cardioverter-defibrillator (S-ICD). The patient had a total of nine adequate shock treatments of ventricular fibrillation during 18 months of follow-up after the implantation. The shock treatments did not lead to any alteration in the Micra. All three sensing vectors of the S-ICD worked well. After 18 months, the functioning of both Micra and S-ICD continues to be uneventful. This case demonstrates that S-ICD combined with Micra may be a safe and feasible approach to provide pacing and ICD treatment without intracardiac leads.

Exhaled particles and small airways

BACKGROUND

Originally, studies on exhaled droplets explored properties of airborne transmission of infectious diseases. More recently, the interest focuses on properties of exhaled droplets as biomarkers, enabled by the development of technical equipment and methods for chemical analysis. Because exhaled droplets contain nonvolatile substances, particles is the physical designation. This review aims to outline the development in the area of exhaled particles, particularly regarding biomarkers and the connection with small airways, i e airways with an internal diameter < 2 mm.

MAIN BODY

Generation mechanisms, sites of origin, number concentrations of exhaled particles and the content of nonvolatile substances are studied. Exhaled particles range in diameter from 0.01 and 1000 μm depending on generation mechanism and site of origin. Airway reopening is one scientifically substantiated particle generation mechanism. During deep expirations, small airways close and the reopening process produces minute particles. When exhaled, these particles have a diameter of < 4 μm. A size discriminating sampling of particles < 4 μm and determination of the size distribution, allows exhaled particle mass to be estimated. The median mass is represented by particles in the size range of 0.7 to 1.0 μm. Half an hour of repeated deep expirations result in samples in the order of nanogram to microgram. The source of these samples is the respiratory tract ling fluid of small airways and consists of lipids and proteins, similarly to surfactant. Early clinical studies of e g chronic obstructive pulmonary disease and asthma, reported altered particle formation and particle composition.

CONCLUSION

The physical properties and content of exhaled particles generated by the airway reopening mechanism offers an exciting noninvasive way to obtain samples from the respiratory tract lining fluid of small airways. The biomarker potential is only at the beginning to be explored.

[Acute coronary occlusion - possible to diagnose in patients with left bundle branch block]

Electrocardiographic diagnosis of acute coronary occlusion can be difficult in the setting of left bundle branch block. If presumably new bundle branch block is considered equivalent to ST-elevation myocardial infarction, unnecessary coronary angiographies will be performed. On the other hand, the diagnosis of an acute coronary occlusion should not be delayed. Presence of concordant ST-segment changes are specific, but not sensitive, findings in the diagnosis of acute coronary occlusion in patients with left bundle branch block.

Ventilation strategies and indoor particulate matter in a classroom

Particle mass and number concentrations were measured in a mechanically ventilated classroom as part of a study of ventilation strategies for energy conservation. The ventilation system was operated either continuously, intermittently, or shut down during nights while it was on during workdays. It appears that the nighttime ventilation scheme is not important for indoor particle concentrations the following day if fans are operated to give five air exchanges in advance of the workday. The highest concentrations of PM10 were found during and after workdays and were due to human activity in the classroom. The average workday PM10 concentration was 14 μg/m(3) , well below the WHO guideline values. The number concentration of particles with diameter <0.750 μm was typically between 0.5 × 10(3) and 3.5 × 10(3)  particle/cm(3) . These concentrations were largely independent of the occupants. Transient formation of small particles was observed when ventilation was shut down. Then remaining ozone reacted with terpenes emitted by indoor sources and gave up to 8 × 10(3)  particle/cm(3) before formation stopped due to lack of ozone. The intermittent ventilation regime was found least favorable for the indoor air quality in the classroom.

Electrocardiographic amplitudes: a new risk factor for sudden death in hypertrophic cardiomyopathy

Aims

Assessment of ECG-features as predictors of sudden death in adults with hypertrophic cardiomyopathy (HCM).

Methods and results

ECG-amplitude sums were measured in 44 normals, 34 athletes, a hospital-cohort of 87 HCM-patients, and 29 HCM-patients with sudden death or cardiac arrest (HCM-CA). HCM-patients with sudden death or cardiac arrest had substantially higher ECG-amplitudes than the HCM-cohort for limb-lead and 12-lead QRS-amplitude sums, and amplitude–duration products (P = 0.00003–P = 0.000002). Separation of HCM-CA from the HCM-cohort is obtained by limb-lead QRS-amplitude sum ≥7.7 mV (odds ratio 18.8, sensitivity 87%, negative predictive value (NPV) 94%, P < 0.0001), 12-lead amplitude–duration product ≥2.2 mV s (odds ratio 31.0, sensitivity 92%, NPV 97%, P < 0.0001), and limb-lead amplitude–duration product ≥0.70 mV s (odds ratio 31.5, sensitivity 93%, NPV 96%, P < 0.0001). Sensitivity in HCM-patients <40 years is 90, 100, and 100% for those ECG-variables, respectively. Qualitative analysis showed correlation with cardiac arrest for pathological T-wave-inversion (P = 0.0003), ST-depression (P = 0.0010), and dominant S-wave in V₄ (P = 0.0048). A risk score is proposed; a score ≥6 gives a sensitivity of 85% but a higher positive predictive value than above measures. Optimal separation between HCM-CA <40 years and athletes is obtained by a risk score ≥6 (odds ratio 345, sensitivity 85%, specificity 100%, P < 0.0001).

Conclusion

Twelve-lead ECG is a powerful instrument for risk-stratification in HCM.

Epicardial and endocardial dispersion of ventricular repolarization. A study of monophasic action potential mapping in healthy pigs

OBJECTIVES

To investigate the total dispersion of ventricular repolarization of the epi- and endocardium.

DESIGN

Monophasic action potentials (MAP) were recorded from 211+/-54 (151-353) left and right ventricular epi- and endocardial sites during atrial pacing in 10 pigs using the CARTO system. The activation time (AT), MAP duration (MAPd) and end of repolarization time (EOR) were measured.

RESULTS

The total dispersion of AT, EOR and MAPd, defined as the maximal differences of these parameters over both the epi- and endocardium, were 57+/-10, 84+/-20, and 75+/-21 ms respectively and were significantly larger than the respective epi- and endocardial dispersions (p<0.05). The epicardial dispersion of AT, EOR and MAPd of both the right and left ventricles were significantly larger than that of each ventricle alone (p<0.02). Sternotomy did not affect these dispersion parameters.

CONCLUSION

Detailed mapping of epicardial repolarization in vivo using the MAP mapping technique is feasible. Both the epi- and endocardium of the two ventricles contribute significantly to the total dispersion of repolarization.

Deterioration of interatrial conduction in patients with paroxysmal atrial fibrillation: electroanatomic mapping of the right atrium and coronary sinus

OBJECTIVES

The purpose of this study was to analyze the velocities across the coronary sinus ostium (cross-CSo) and within the coronary sinus (intra-CS) in patients with and without paroxysmal atrial (AF) fibrillation and to estimate the interatrial conduction deterioration area in AF patients.

BACKGROUND

Interatrial conduction delay in AF patients has been reported. However, localization of the interatrial conduction delay still is not clear.

METHODS

Thirteen patients with paroxysmal AF and 10 control patients with AV nodal reentrant tachycardia or ectopic atrial tachycardia were enrolled in the study. Right atrial and CS mapping were performed using the CARTO electroanatomic mapping system during sinus rhythm and during distal CS pacing. The activation times and spatial distances of cross-CSo and intra-CS were measured between paired sites, from which the activation velocities of cross-CSo and intra-CS were obtained.

RESULTS

During sinus rhythm, the activation velocities of cross-CSo in the AF group (1.2 +/- 0.2 m/s) were significantly slower than those in the control group (2.9 +/- 1.6 m/s, P < .05). During distal CS pacing, the cross-CSo velocities of the AF group (1.0 +/- 0.5 m/s) also appeared slower than those in the control group (1.4 +/- 0.2 m/s, P = .07). However, no difference was found in intra-CS activation velocities between the two groups (2.8 +/- 1.9 vs 3.2 +/- 2.2 m/s and 1.5 +/- 0.3 vs 1.4 +/- 0.3 m/s, P > .05 during sinus rhythm and distal CS pacing, respectively).

CONCLUSIONS

Interatrial conduction at the posteroparaseptal region across the CS ostium was significantly slower in patients with paroxysmal AF than in control patients, further supporting the link between interatrial conduction deterioration and paroxysmal AF.

Non-invasive evaluation of ventricular refractoriness and its dispersion during ventricular fibrillation in patients with implantable cardioverter defibrillator

Background

Local ventricular refractoriness and its dispersion during ventricular fibrillation (VF) have not been well evaluated, due to methodological difficulties.

Methods

In this study, a non-invasive method was used in evaluation of local ventricular refractoriness and its dispersion during induced VF in 11 patients with VF and/or polymorphic ventricular tachycardia (VT) who have implanted an implantable cardioverter defibrillator (ICD). Bipolar electrograms were simultaneously recorded from the lower oesophagus behind the posterior left ventricle (LV) via an oesophageal electrode and from the right ventricular (RV) apex via telemetry from the implanted ICD. VF intervals were used as an estimate of the ventricular effective refractory period (VERP). In 6 patients, VERP was also measured during sinus rhythm at the RV apex and outflow tract (RVOT) using conventional extra stimulus technique.

Results

Electrograms recorded from the RV apex and the lower esophagus behind the posterior LV manifested distinct differences of the local ventricular activities. The estimated VERPs during induced VF in the RV apex were significantly shorter than that measured during sinus rhythm using extra stimulus technique. The maximal dispersion of the estimated VERPs during induced VF between the RV apex and posterior LV was that of 10 percentile VF interval (40 ± 27 ms), that is markedly greater than the previously reported dispersion of ventricular repolarization without malignant ventricular arrhythmias (30–36 ms).

Conclusions

This study verified the feasibility of recording local ventricular activities via oesophageal electrode and via telemetry from an implanted ICD and the usefulness of VF intervals obtained using this non-invasive technique in evaluation of the dispersion of refractoriness in patients with ICD implantation.

Electroanatomic mapping of right atrial activation in patients with and without paroxysmal atrial fibrillation

Inter-atrial conduction delay in patients with atrial fibrillation (AF) has been reported. However, the area of this conduction delay has not been well identified. The activation time and conduction velocity over the right atrial endocardium were evaluated during sinus rhythm using the CARTO mapping technique in 6 patients with paroxysmal AF (AF group) and 11 patients without history of AF (control group). No significant differences were observed between the 2 groups in the mean activation times and conduction velocities from the earliest activation site to the superior septum, His bundle area and coronary sinus ostium, or in the total activation times of the right atrium. There was no significant difference between the two groups in the local conduction velocity between 2 adjacent sites in the free wall, septum and bottom of the right atrium. This study suggests the previously reported conduction delay in the posteroseptal region in patients with paroxysmal AF might locate within the posterior inter-atrial septum.

[Catheter ablation--new cure for paroxysmal atrial fibrillation. Case reports show how the trigger mechanism can be abolished]

The trigger mechanism of paroxysmal atrial fibrillation is usually an atrial ectopic beat originating in the muscular sleeves of the pulmonary veins. These and other origins of the trigger mechanisms can be explored with electroanatomical mapping technique. Once identified, the trigger mechanism may be abolished by using the catheter ablation technique to cure the arrhythmia. We present the results for two patients with trigger mechanisms of different origin whose arrhythmia has been cured using the focal ablation technique.

Clinical value of transesophageal atrial stimulation and recording in patients with arrhythmia-related symptoms or documented supraventricular tachycardia--correlation to clinical history and invasive studies

The main objective of the present study was to evaluate the clinical applicability of transesophageal atrial stimulation (TAS) and recording with regard to inducibility of supraventricular tachycardia (SVT) in patients with either an ECG-documented paroxysmal SVT or a clinical history of palpitations suggesting this disease. A further objective was to assess the inducibility of SVT and to compare the inducibility by TAS with that obtained by an invasive electrophysiologic study (EPS). A total of 64 patients (aged 13-74 years) with ECG-documented paroxysmal SVT (n = 50) or only a history of palpitations (n = 14) was referred for TAS. Preexcitation was present in 35 patients. The study protocol included single and double extrastimuli delivered at a basic paced interval of 500 ms, and incremental atrial stimulation until a cycle length of 275 ms or a second-degree AV block appeared. In 10 patients atropine intravenously was required for induction. The same protocol was used in 34 of the patients who also underwent invasive EPS. TAS was completed in 56 of 64 patients (88%). In this group SVT was induced during TAS in 84% (47/56). Of patients with ECG-documented tachycardia, clinical tachycardia was induced in 90% (35/39) with ECG-documented regular paroxysmal SVT and in 67% of patients (4/6) with ECG-documented atrial fibrillation. In patients without ECG-documented atrial fibrillation. In patients without ECG-documented tachycardia, clinically relevant arrhythmia was induced in 73% (8/11). In 30 of 32 patients (94%) with an inducible tachycardia during invasive EPS, it was also possible to induce the tachycardia by TAS.(ABSTRACT TRUNCATED AT 250 WORDS)