Supraventricular Tachycardia—Part I

Left posterior fascicular ventricular tachycardia in a young infant with a structurally normal heart: Clinical course and caveats to electrocardiographic diagnosis

In this illustrative case report, we describe a rare case of left posterior fascicular ventricular tachycardia (LPFVT) in a 2 month-old infant with emphasis on electrocardiographic caveats to diagnosis. The clinical course, treatment, and eventual resolution of the VT over a 2 year follow-up is comprehensively compared and contrasted to a modicum of individual such case reports of infants. The corpus of each such case of infantile LPVT is systematically reviewed and succinctly summarized in a tabular compendium. The collective knowledge compiled here should allow for a refined approach to diagnosis and management of this unusual arrhythmia.

Outcomes in patients with dual antegrade conduction in the atrioventricular node: insights from a multicentre observational study

BACKGROUND

Supraventricular tachycardias induced by dual antegrade conduction via the atrioventricular (AV) node are rare but often misdiagnosed with severe consequences for the affected patients. As long-term follow-up in these patients was not available so far, this study investigates outcomes in patients with dual antegrade conduction in the AV node.

METHODS AND RESULTS

In this multicentre observational study, patients from six European centres were studied. Catheter ablation was performed in 17 patients (52 ± 16 years) with dual antegrade conduction via both AV nodal pathways between 2012 and 2018. Patients with the final diagnosis of a manifest dual AV nodal non-re-entrant tachycardia had a mean delay of the correct diagnosis of over 1 year (range 2-31 months). Two patients received prescription of non-indicated oral anticoagulation, two further patients suffered from inappropriate shocks of an implantable cardioverter defibrillator. In 12 patients, a co-existence of dual antegrade and re-entry conduction in the AV node was present. Mean fast pathway conduction time was 138 ± 61 ms and mean slow pathway conduction time was 593 ± 134 ms. Successful radiofrequency catheter ablation was performed in all patients. Post-procedurally oral anticoagulation was discontinued, without detection of cerebrovascular events or atrial fibrillation during a long-term follow-up of median 17 months (range 6-72 months).

CONCLUSION

This first multicentre study investigating patients with supraventricular tachycardia and dual antegrade conduction in the AV node demonstrates that catheter ablation is safe and effective while long-term patient outcome is good. Autonomic tone dependent changes in ante- vs. retrograde conduction via slow and/or fast pathway can challenge the diagnosis and therapy in some patients.

A Case of Intermittent Preexcitation and Palpitations: More than Meets the Eye

We discuss the case of a 22-year-old female who presented to the clinic experiencing recurrent palpitations. She was also found to have intermittent preexcitation on her electrocardiogram (ECG). Her palpitations were attributed to stress. Previously, she had gone to the emergency department a few times and was diagnosed with sinus tachycardia. Her ECG revealed a right-sided accessory pathway. Given her atypical finding of orthodromic reciprocating tachycardia, a 30-day event monitor was implanted, which revealed that one episode was correlated with sinus tachycardia, with a heart rate of 120 bpm. She mentioned experiencing other episodes that were severe, but she did not activate the monitor manually at the time of these incidents. After a long discussion with the patient about available management options for her symptoms, it was decided to proceed with long-term monitoring with an implantable loop recorder to gather better symptom–rhythm correlation data. At six months after surgery, the patient experienced multiple manually triggered transmissions from her device, which were all consistent with sinus tachycardia. She had no episode suggestive of any supraventricular tachycardia and is thus being treated for inappropriate sinus tachycardia. This case highlights the importance of gathering adequate symptom–rhythm correlation data before pursuing more invasive treatment options for an arrhythmic etiology in low-risk patients.

Atrioventricular Nodal Reentrant Tachycardia in Very Elderly Patients: A Single-center Experience

We present a series of elderly patients older than 80 years who had recurrent palpitations for decades and who were subsequently diagnosed with atrioventricular (AV) nodal reentrant tachycardia (AVNRT). Through a retrospective chart analysis, we identified 12 patients (nine females and three males) aged 88 years ± 3.7 years (range: 80–92 years) seen at our center from 2015 to 2016 for recurrent palpitations and supraventricular tachycardia (SVT) who were ultimately diagnosed with AVNRT. These patients had palpitations and had been treated for anxiety and panic attacks for decades. They underwent electrophysiology (EP) study and successful ablation of the slow pathway. The demographic data, symptoms, and EP characteristics during the EP studies of the patients were evaluated. All 12 patients experienced palpitations and all but three had documented SVT on a loop recorder or an event monitor. During EP study, all patients displayed slow-pathway conduction. Nine patients demonstrated discontinuous AV nodal conduction curves, while three showed continuous AV nodal conduction curves. The observed tachycardia rates were 496.7 ms ± 25.7 ms. Three patients had atrial fibrillation (AF), which was noted during monitoring with the implanted loop recorders. Tachycardia was induced with both burst atrial pacing and atrial extrastimuli in five patients and with extrastimuli only in two patients. In five patients, no tachycardia induction was noted, but these individuals showed evidence of dual AV node physiology. Successful elimination of residual slow-pathway conduction postablation and/or noninducibility of tachycardia in the postablation period were achieved in all patients. All patients remained symptom-free over a period of one year. The patients who had AF in addition to AVNRT also did not present any recurrent AF following AVNRT ablation but are being monitored for recurrence. AVNRT in elderly people is often confused with panic attacks; hence, reports of panic attacks in elderly people should be properly evaluated for an arrhythmic etiology.

Supraventricular tachycardia: An overview of diagnosis and management

Supraventricular tachycardia (SVT) is a common cause of hospital admissions and can cause significant patient discomfort and distress. The most common SVTs include atrioventricular nodal re-entrant tachycardia, atrioventricular re-entrant tachycardia and atrial tachycardia. In many cases, the underlying mechanism can be deduced from electrocardiography during tachycardia, comparing it with sinus rhythm, and assessing the onset and offset of tachycardia. Recent European Society of Cardiology guidelines continue to advocate the use of vagal manoeuvres and adenosine as first-line therapies in the acute diagnosis and management of SVT. Alternative therapies include the use of beta-blockers and calcium channel blockers. All patients treated for SVT should be referred for a heart rhythm specialist opinion. Long-term treatment is dependent on several factors including frequency of symptoms, risk stratification, and patient preference. Management can range from conservative, if symptoms are rare and the patient is low risk, to catheter ablation which is curative in the majority of patients.

Apoptosis and epicardial contributions act as complementary factors in remodeling of the atrioventricular canal myocardium and atrioventricular conduction patterns in the embryonic chick heart

BACKGROUND

During heart development, it has been hypothesized that apoptosis of atrioventricular canal myocardium and replacement by fibrous tissue derived from the epicardium are imperative to develop a mature atrioventricular conduction. To test this, apoptosis was blocked using an established caspase inhibitor and epicardial growth was delayed using the experimental epicardial inhibition model, both in chick embryonic hearts.

RESULTS

Chicken embryonic hearts were either treated with the peptide caspase inhibitor zVAD-fmk by intrapericardial injection in ovo (ED4) or underwent epicardial inhibition (ED2.5). Spontaneously beating embryonic hearts isolated (ED7-ED8) were then stained with voltage-sensitive dye Di-4-ANEPPS and imaged at 0.5-1 kHz. Apoptotic cells were quantified (ED5-ED7) by whole-mount LysoTracker Red and anti-active caspase 3 staining. zVAD-treated hearts showed a significantly increased proportion of immature (base to apex) activation patterns at ED8, including ventricular activation originating from the right atrioventricular junction, a pattern never observed in control hearts. zVAD-treated hearts showed decreased numbers of apoptotic cells in the atrioventricular canal myocardium at ED7. Hearts with delayed epicardial outgrowth showed also increased immature activation patterns at ED7.5 and ED8.5. However, the ventricular activation always originated from the left atrioventricular junction. Histological examination showed no changes in apoptosis rates, but a diminished presence of atrioventricular sulcus tissue compared with controls.

CONCLUSIONS

Apoptosis in the atrioventricular canal myocardium and controlled replacement of this myocardium by epicardially derived HCN4-/Trop1- sulcus tissue are essential determinants of mature ventricular activation pattern. Disruption can lead to persistence of accessory atrioventricular connections, forming a morphological substrate for ventricular pre-excitation. Developmental Dynamics 247:1033-1042, 2018. © 2018 Wiley Periodicals, Inc.

Concealed Accessory Pathways with a Single Ventricular and Two Discrete Atrial Insertion Sites

BACKGROUND

Atrioventricular reciprocating tachycardia (AVRT) utilizing a concealed accessory pathway is common. It is well appreciated that some patients may have multiple accessory pathways with separate atrial and ventricular insertion sites.

METHODS

We present three cases of AVRT utilizing concealed pathways with evidence that each utilizing a single ventricular insertion and two discrete atrial insertion sites.

RESULTS

In case one, two discrete atrial insertion sites were mapped in two separate procedures, and only during the second ablation was the Kent potential identified. Ablation of the Kent potential at this site remote from the two atrial insertion sites resulted in the termination of the retrograde conduction in both pathways. Case two presented with supraventricular tachycardia (SVT) with alternating eccentric atrial activation patterns without alteration in the tachycardia cycle length. The two distinct atrial insertion sites during orthodromic AVRT and ventricular pacing were targeted and each of the two atrial insertion sites were successfully mapped and ablated. In case three, retrograde decremental conduction utilizing both atrial insertion sites was identified prior to ablation. After mapping and ablation of the first discrete atrial insertion site, tachycardia persisted utilizing the second atrial insertion site. Only after ablation of the second atrial insertion site was SVT noninducible, and VA conduction was no longer present.

CONCLUSIONS

Concealed retrograde accessory pathways with discrete atrial insertion sites may have a common ventricular insertion site. Identification and ablation of the ventricular insertion site or the separate discrete atrial insertion sites result in successful treatment.

Ablatogenomics: can genotype guide catheter ablation for cardiac arrhythmias?

Previously confined to the management of rare inherited arrhythmia syndromes, a role for genetics within cardiac electrophysiology has begun to emerge for more common arrhythmias, including atrial fibrillation (AF). Catheter ablation for AF is an invasive procedure effective for restoring normal rhythm, however, fails in up to 40% of those undergoing their first procedure and carries a risk for serious adverse events. Recent studies have suggested that a common genetic variant within chromosome 4q25 may be a powerful predictor of procedural success, highlighting the potential of an 'ablatogenomic' strategy. Although still in its infancy, an ablatogenomic approach for AF may facilitate delivery of ablation to those most likely to benefit, while sparing those prone to fail from its risks.

Perinatal arrhythmias

Cardiac arrhythmias are very frequent in fetuses and newborns. The prognosis depends on the nature of the arrhythmias but is most often either spontaneously benign or following short-term medication administration. A correct diagnosis is essential for both management and prognosis. It is based on echocardiography during the fetal period and mainly on history, physical exam, and electrocardiogram after birth, but other modalities are available to record transient arrhythmic events. Irregular rhythms are mostly benign and rarely require therapy. In most fetuses and infants, tachyarrhythmias resolve spontaneously or require short-term administration of antiarrhythmics. Approximately one third of these may recur later on, especially during adolescence. Persistent bradyarrhythmias might require pacemaker implantation when associated with failure to thrive or with risk of sudden death.

CONCLUSION

Arrhythmias in fetuses and infants are very common and mostly benign. History, physical exam, and recording of the arrhythmia are essential to make a correct diagnosis and establish an appropriate management for the rare potentially harmful arrhythmias.

Current algorithms for the diagnosis of wide QRS complex tachycardias

The differential diagnosis of a regular, monomorphic wide QRS complex tachycardia (WCT) mechanism represents a great diagnostic dilemma commonly encountered by the practicing physician, which has important implications for acute arrhythmia management, further work-up, prognosis and chronic management as well. This comprehensive review discusses the causes and differential diagnosis of WCT, and since the ECG remains the cornerstone of WCT differential diagnosis, focuses on the application and diagnostic value of different ECG criteria and algorithms in this setting and also provides a practical clinical approach to patients with WCTs.

Wolff-Parkinson-White Syndrome Mimics a Conduction Disease

Background. It is important to recognise Wolff-Parkinson-White (WPW) syndrome in electrocardiograms (ECG), as it may mimic ischaemic heart disease, ventricular hypertrophy, and bundle branch block. Recognising WPW syndrome allows for risk stratification, the identification of associated conditions, and the institution of appropriate management. Objective. The present case showed that electrophysiological study is indicated in patients with abnormal ECG and syncope. Case Report. A 40-year-old man with Wolff-Parkinson-White syndrome was presented to emergency with syncope. A baseline ECG was a complete right branch block and posterior left hemiblock. He was admitted to the cardiac care unit for pacemaker implantation. The atypical figure of complete right branch block and posterior left hemiblock was thought to be a “false positive” of conduction abnormality. But the long anterograde refractory period of the both accessory pathway and atrioventricular conduction may cause difficulty in diagnosing Wolff-Parkinson-White syndrome, Conclusion. A Wolff-Parkinson-White Syndrome may mimic a conduction disease. No reliable algorithm exists for making an ECG diagnosis of a preexcitation syndrome with conduction disorders. This can lead to diagnostic and therapeutic dilemmas in the context of syncope.

Dual atrioventricular nodal pathways physiology: a review of relevant anatomy, electrophysiology, and electrocardiographic manifestations

More than half a century has passed since the concept of dual atrioventricular (AV) nodal pathways physiology was conceived. Dual AV nodal pathways have been shown to be responsible for many clinical arrhythmia syndromes, most notably AV nodal reentrant tachycardia. Although there has been a considerable amount of research on this topic, the subject of dual AV nodal pathways physiology remains heavily debated and discussed. Despite advances in understanding arrhythmia mechanisms and the widespread use of invasive electrophysiologic studies, there is still disagreement on the anatomy and physiology of the AV node that is the basis of discontinuous antegrade AV conduction. The purpose of this paper is to review the concept of dual AV nodal pathways physiology and its varied electrocardiographic manifestations.

Cryoablation versus radiofrequency ablation of atrioventricular nodal reentrant tachycardia

BACKGROUND

Ablation of the slow pathway is an established cure for atrioventricular nodal reentrant tachycardia (AVNRT). Periprocedural damage to the conduction system is a major concern during AVNRT ablation, and cryoablation (CRYO) has been suggested to improve the procedural safety compared to standard radiofrequency (RF) ablation, without reducing the procedural success.

OBJECTIVE

We performed a systematic review and meta-analysis of studies comparing CRYO with RF ablation of AVNRT.

METHODS

We searched PubMed, CENTRAL, the BioMed Central, EMBASE, CardioSource, clinicaltrials.gov, and ISI Web of Science (January 1980 to July 2013). No language restriction was applied. Two independent reviewers screened titles and abstracts to identify studies that compared the procedural outcomes of AVNRT ablation with either CRYO or RF energy. Two independent reviewers assessed the risk of bias according to the Cochrane Collaboration, and extracted patient, study characteristics, and procedural outcome data. Results are expressed as odds ratio (OR) or as weighted mean difference (WMD) with their 95 % confidence interval (CI).

RESULTS

Fourteen studies (5 prospective randomized and 9 observational) with 2,340 patients (mean age range 13 to 53 years, 1,522 (65 %) females) were included in the analysis. RF ablation was performed in 1,262 (54 %) patients, while CRYO in 1,078 (46 %) patients. Acute success (abolition of dual atrioventricular node physiology or single echo beats) was achieved in 88 % of patients treated with RF versus 83 % of those treated with CRYO (OR = 0.72, 95 % CI 0.46 to 1.13; P = 0.157). RF ablation was associated with shorter total procedure time (WMD = -13.7 min, 95 % CI -23 to -4.3 min; P = 0.004), but slightly longer fluoroscopy time (WMD = +4.6 min 95 % CI +1.7 to +7.6 min; P = 0.002). Permanent atrioventricular block occurred in 0.87 % RF cases and in no CRYO case (OR = 3.60, 95 % CI 1.09 to 11.81; P = 0.035). Over a median follow-up of 10.5 months (range 6 to 12 months), freedom from recurrent AVNRT was 96.5 % in the RF group versus 90.9 % in the CRYO group (OR = 0.40, 95 % CI 0.28 to 0.58; P < 0.001). At meta-regression analysis, no clinical or procedural variable had a significant interaction with the results above.

CONCLUSIONS

In patients undergoing AVNRT ablation, RF significantly reduces the risk of long-term arrhythmia recurrence compared to CRYO, but is associated with a higher risk of permanent atrioventricular block.

Aqueous fraction from Costus spiralis (Jacq.) Roscoe leaf reduces contractility by impairing the calcium inward current in the mammalian myocardium

ETHNOPHARMACOLOGICAL RELEVANCE

Brazilian folk medicine uses infusion of Costus spiralis leaf to help people to treat arterial hypertension and syndromes of cardiac hyperexcitability.

AIM OF THE STUDY

Evaluate the aqueous fraction (AqF) effect on atrial contractility and investigate its mechanism of action.

MATERIALS AND METHODS

The AqF effect on the cardiac contractility was studied on isolated electrically driven guinea pig left atria. Atropine and tetraethylammonium (TEA) were employed to investigate whether potassium contributes for the inotropic mechanism of the AqF. The role of calcium in this effect was also studied. This was done by analysing the AqF effect on the Bowditch's phenomenon, as well as by studying whether it could interfere with the concentration-effect curve for CaCl(2), isoproterenol, and BAY K8644. Mice isolated cardiomyocytes were submitted to a whole-cell patch-clamp technique in order to evaluate whether the L-type calcium current participates on the AqF effect. Furthermore, the intracellular calcium transient was studied by confocal fluorescence microscopy.

RESULTS

AqF depressed the atrial contractile force. It was the most potent fraction from C. spiralis leaf (EC(50)=305 ± 41 mg/l) (crude extract: EC(50)=712 ± 41; ethyl acetate: EC(50)=788 ± 121; chloroform: EC(50)=8,948 ± 1,346 mg/l). Sodium and potassium content in the AqF was 0.15 mM and 1.91 mM, respectively. Phytochemical analysis revealed phenols, tannins, flavones, xanthones, flavonoids, flavonols, flavononols, flavonones, and saponins. Experiments with atropine and TEA showed that potassium does not participate of the inotropic mechanism of AqF. However, this fraction decreased the force overshoot characteristic of the Bowditch's phenomenon, and shifted the concentration-response curve for CaCl(2) (EC(50) from 1.12 ± 0.07 to 7.23 ± 0.47 mM) indicating that calcium currents participate on its mechanism of action. Results obtained with isoproterenol (1-1,000 pM) and BAY K8644 (5-2000nM) showed that AqF abolished the inotropic effect of these substances. On cardiomyocytes, 48mg/l AqF reduced (∼23%) the L-type calcium current density from -6.3 ± 0.3 to -4.9 ± 0.2 A/F (n=5 cells, p<0.05) and reduced the intracellular calcium transient (∼20%, 4.7 ± 1.2 a.u., n=42 cells to 3.7 ± 1.00 a.u., n=35 cells, p<0.05). However, the decay time of the fluorescence was not changed (control: 860 ± 32 ms, n=42 cells; AqF: 876 ± 26 ms, n=35 cells, p>0.05).

CONCLUSIONS

The AqF of C. spiralis leaf depresses myocardial contractility by reducing the L-type calcium current and by decreasing the intracellular calcium transient. Despite the lack of data on the therapeutic dose of AqF used in folk medicine, our results support, at least in part, the traditional use of this plant to treat cardiac disorders.