Miniseries 2-Septal and paraseptal accessory pathways-Part IV: Inferior paraseptal accessory pathways-lessons from surgical and catheter ablation.

Surgeons and electrophysiologists performing accessory pathway ablation procedures have used the term 'posteroseptal' region. This area, however, is neither septal nor posterior, but paraseptal and inferior; paraseptal because it includes the fibro-adipose tissues filling the pyramidal space and not the muscular septum itself and inferior because it is part of the heart adjacent to the diaphragm. It should properly be described, therefore, as being inferior and paraseptal. Pathways in this region can be ablated at three areas, which we term right inferior, mid-inferior, and left inferior paraseptal. The right- and left inferior paraseptal pathways connect the right and left atrial vestibules with the right and left paraseptal segments of the parietal ventricular walls. The mid-inferior paraseptal pathways take a subepicardial course from the myocardial sleeves surrounding the coronary sinus and its tributaries. Our review addresses the evolution of the anatomical concept of the inferior paraseptal region derived from surgical and catheter ablation procedures. We also highlight the limitations of the 12-lead electrocardiogram in identifying, without catheter electrode mapping, which are the pathways that can be ablated without a coronary sinus, or left heart approach.

Miniseries 2-Septal and paraseptal accessory pathways-Part I: The anatomic basis for the understanding of para-Hisian accessory atrioventricular pathways.

AIMS: Although the anatomy of the atrioventricular conduction axis was well described over a century ago, the precise arrangement in the regions surrounding its transition from the atrioventricular node to the so-called bundle of His remain uncertain. We aimed to clarify these relationships. METHODS AND RESULTS: We have used our various datasets to examine the development and anatomical arrangement of the atrioventricular conduction axis, paying particular attention to the regions surrounding the point of penetration of the bundle of His. It is the areas directly adjacent to the transition of the atrioventricular conduction axis from the atrioventricular node to the non-branching atrioventricular bundle that constitute the para-Hisian areas. The atrioventricular conduction axis itself traverses the membranous part of the ventricular septum as it extends from the node to become the bundle, but the para-Hisian areas themselves are paraseptal. This is because they incorporate the fibrofatty tissues of the inferior pyramidal space and the superior atrioventricular groove. In this initial overarching review, we summarize the developmental and anatomical features of these areas along with the location and landmarks of the atrioventricular conduction axis. We emphasize the relationships between the inferior pyramidal space and the infero-septal recess of the subaortic outflow tract. The details are then explored in greater detail in the additional reviews provided within our miniseries. CONCLUSION: Our anatomical findings, described here, provide the basis for our concomitant clinical review of the so-called para-Hisian arrhythmias. The findings also provide the basis for understanding the other variants of ventricular pre-excitation.

Miniseries 2-Septal and paraseptal accessory pathways-Part III: Mid-paraseptal accessory pathways-revisiting bypass tracts crossing the pyramidal space.

The mid-paraseptal region corresponds to the portion of the pyramidal space whose right atrial aspect is known as the triangle of Koch. The superior area of this mid-paraseptal region is also para-Hisian, and is close to the compact atrioventricular node and the His bundle. The inferior sector of the mid-paraseptal area is unrelated to the normal atrioventricular conduction pathways. It is, therefore, a safe zone in which, if necessary, to perform catheter ablation. The middle part of the mid-paraseptal zone may, however, in some patients, house components of the compact atrioventricular node. This suggests the need for adopting a prudent attitude when considering catheter ablation in this area. The inferior extensions of the atrioventricular node, which may represent the substrate for the slow atrioventricular nodal pathway, take their course through the middle, and even the inferior, sectors of the mid-paraseptal region. In this review, we contend that the middle and inferior areas of the mid-paraseptal region correspond to what, in the past, was labelled by most groups as the 'midseptal' zone. We describe the electrocardiographic patterns observed during pre-excitation and orthodromic reciprocating tachycardia in patients with pathways ablated in the middle or inferior sectors of the region. We discuss the modification of the ventriculo-atrial conduction times during tachycardia after the development of bundle branch block aberrancy. We conclude that the so-called 'intermediate septal' pathways, as described in the era of surgical ablation, were insufficiently characterized. They should not be considered the surrogate of the 'midseptal' pathways defined using endocardial catheter electrode mapping.

Miniseries 2-Septal and paraseptal accessory pathways-Part II: Para-Hisian accessory pathways-so-called anteroseptal pathways revisited.

Surgeons, when dividing bypass tracts adjacent to the His bundle, considered them to be 'anteroseptal'. The area was subsequently recognized to be superior and paraseptal, although this description is not entirely accurate anatomically, and conveys little about the potential risk during catheter interventions. We now describe the area as being para-Hisian, and it harbours two types of accessory pathways. The first variant crosses the membranous septum to insert into the muscular ventricular septum without exiting the heart, and hence being truly septal. The second variant inserts distally in the paraseptal components of the supraventricular crest, and consequently is crestal. The site of ventricular insertion determines the electrocardiographic expression of pre-excitation during sinus rhythm, with the two types producing distinct patterns. In both instances, the QRS and the delta wave are positive in leads I, II, and aVF. In crestal pathways, however, the QRS is ≥ 140 ms, and exhibits an rS configuration in V1-2. The delta wave in V1-2 precedes by 20-50 ms the apparent onset of the QRS in I, II, III, and aVF. In the true septal pathways, the QRS complex occupies ∼120 ms, presenting a QS, W-shaped, morphology in V1-2. The delta wave has a simultaneous onset in all leads. Our proposed terminology facilitates the understanding of the electrocardiographic manifestations of both types of para-Hisian pathways during pre-excitation and orthodromic tachycardia, and informs on the level of risk during catheter ablation.

An unusual ectopic ventricular rhythm in a young woman.

A case of a 22-year-old young pregnant woman with palpitations and near syncope is presented. Holter monitoring showed very frequent premature beats and runs of wide complex tachycardia, refractory to antiarrhythmic drugs. Electrophysiologic evaluation disclosed spontaneous automatism arising in an atriofascicular pathway. Differential diagnosis is discussed.

Unusual variants of pre-excitation: From anatomy to ablation: Part III-Clinical presentation, electrophysiologic characteristics, when and how to ablate nodoventricular, nodofascicular, fasciculoventricular pathways, along with considerations of permanent junctional reciprocating tachycardia.

The recognition of the presence, location, and properties of unusual accessory pathways for atrioventricular conduction is an exciting, but frequently a difficult, challenge for the clinical cardiac arrhythmologist. In this third part of our series of reviews, we discuss the different steps required to come to the correct diagnosis and management decision in patients with nodofascicular, nodoventricular, and fasciculo-ventricular pathways. We also discuss the concealed accessory atrioventricular pathways with the properties of decremental retrograde conduction that are associated with the so-called permanent form of junctional reciprocating tachycardia. Careful analysis of the 12-lead electrocardiogram during sinus rhythm and tachycardias should always precede the investigation in the catheterization room. When using programmed electrical stimulation of the heart from different intracardiac locations, combined with activation mapping, it should be possible to localize both the proximal and distal ends of the accessory connections. This, in turn, should then permit the determination of their electrophysiologic properties, providing the answer to the question "are they incorporated in a tachycardia circuit?". It is this information that is essential for decision-making with regard to the need for catheter ablation, and if necessary, its appropriate site.

Part II-Clinical presentation, electrophysiologic characteristics, and when and how to ablate atriofascicular pathways and long and short decrementally conducting accessory pathways.

Recognition of the presence, location, and properties of unusual accessory pathways for atrioventricular conduction is an exciting, frequently difficult, challenge for the clinical cardiac arrhythmologist. In this second part of our series of reviews relative to this topic, we discuss the steps required to achieve the correct diagnosis and appropriate management in patients with the so-called "Mahaim" variants of pre-excitation. We indicate that, nowadays, it is recognized that these abnormal rhythms are manifest because of the presence of atriofascicular pathways. These anatomical substrates, however, need to be distinguished from the other long and short accessory pathways which produce decremental atrioventricular conduction. The atriofascicular pathways, along with the long decrementally conducting pathways, have their atrial components located within the vestibule of the tricuspid valve. The short decremental pathways, in contrast, can originate in the vestibules of either the mitral or tricuspid valves. As a starting point, careful analysis of the 12-lead electrocardiogram, taken during both sinus rhythm and tachycardias, should precede any investigation in the catheterization room. When assessing the patient in the electrophysiological laboratory, the use of programmed electrical stimulation from different intracardiac locations, combined with entrainment technique and activation mapping, should permit the establishment of the properties of the accessory pathways, and localization of its proximal and distal ends. This should provide the answer to the question "is the pathway incorporated into the circuit underlying the clinical tachycardia". That information is essential for decision-making with regard to need, and localization of the proper site, for catheter ablation.

Atypical bypass tracts: can they be recognized during sinus rhythm?

Atypical bypass tracts or variants of ventricular pre-excitation are rare anatomic structures often with rate-dependent slowing in conduction, called decremental conduction. During sinus rhythm, electrocardiographic recognition of those structures may be difficult because unlike in the Wolff-Parkinson-White syndrome where usually overt ventricular pre-excitation is present, the electrocardiogram (ECG) often shows a subtle pre-excitation pattern because of less contribution to ventricular activation over the slow and decrementally conducting bypass. Following the structure described by Ivan Mahaim and Benatt corresponding to a fasciculoventricular pathway, several other new variants of ventricular pre-excitation were reported. In this review, we aim to discuss the electrocardiographic pattern of the different subtypes of variants of ventricular pre-excitation, including the atriofascicular pathway, long and short decrementally conducting atrioventricular pathways, fasciculoventricular pathway, the atrio-Hisian bypass tract, and nodoventricular and nodofascicular fibres. Emphasis will be on the ECG findings during sinus rhythm.

Reappraisal and new observations on atrial tachycardia ablated from the non-coronary aortic sinus of Valsalva.

Aims: The clinical characteristics of atrial tachycardias (AT) ablated from the non-coronary aortic sinus (NCS) are thus far described only in small series. We aimed to outline, in a large cohort of patients, the clinical, electrocardiographic, electrophysiological characteristics of this tachycardia. Methods and results: We analysed data pertaining to clinical, electrocardiographic, and electrophysiological characteristics of 43 consecutive patients from an overall cohort of 441 with AT who were successfully ablated from the NCS. The tachycardias ablated from the NCS were paroxysmal (98%) and adenosine sensitive (35/35). The patients were aged 54.6 ± 12.4 years, showing female preponderance (74%). No P wave pattern was predictive of the location of ablation. Electrophysiological findings suggested a possible micro-reentrant mechanism. During tachycardia, atrial electrograms recorded in the NCS preceded the A in the His region by 10.9 ± 7.4 ms. Fractionated atrial electrograms were noted at the site of ablation in 42 patients during the tachycardia. Radiofrequency ablation terminated the tachycardia within 5 s in 88%, with thermal automaticity seen only in 3 patients. The site of ablation at the base of the NCS was adjacent to the presumed site of the retroaortic node, a remnant of the initial atrio-ventricular canal musculature. Conclusions: AT ablated from the NCS is a paroxysmal arrhythmia in middle-aged women, with distinct electrocardiographic and electrophysiological characteristics. We suspect the retroaortic node to be involved in the tachycardia circuit.

The value of the 12-lead electrocardiogram in localizing the scar in non-ischaemic cardiomyopathy.

AIMS: Patients with non-ischaemic cardiomyopathy (NICM) and ventricular tachycardia can be categorized as anteroseptal (AS) or inferolateral (IL) scar sub-types based on imaging and voltage mapping studies. The aim of this study was to correlate the baseline electrocardiogram (ECG) with endo-epicardial voltage maps created during ablation procedures and identify the ECG characteristics that may help to distinguish the scar as AS or IL. METHODS AND RESULTS: We assessed 108 baseline ECGs; 72 patients fulfilled criteria for dilated cardiomyopathy whereas 36 showed minimal structural abnormalities. Based on the unipolar low-voltage distribution, the scar pattern was classified as predominantly AS (n = 59) or IL (n = 49). Three ECG criteria (PR interval < 170 ms or QRS voltage in inferior leads <0.6 mV or a lateral q wave) resulted in 92% sensitivity and 90% specificity for predicting an IL pattern in patients with preserved ejection fraction (EF). The four-step algorithm for dilated cardiomyopathy included a paced ventricular rhythm or PR > 230 ms or QRS > 170 ms or an r ≤ 0.3 mV in V3 having 92 and 81% of sensitivity and specificity, respectively, in predicting AS scar pattern. A significant negative correlation was found between the extension of the endocardial unipolar low voltage area and left ventricular EF (rs = -0.719, P < 0.001). The extent of endocardial AS unipolar low voltage was correlated with PR interval and QRS duration (rs = 0.583 and rs = 0.680, P < 0.001, respectively) and the IL epicardial unipolar low voltage with the mean voltage of the limb leads (rs = -0.639, P < 0.001). CONCLUSION: Baseline ECG features are well correlated with the distribution of unipolar voltage abnormalities in NICM and may help to predict the location of scar in this population.

Risk stratification for sudden cardiac death: current status and challenges for the future.

Sudden cardiac death (SCD) remains a daunting problem. It is a major public health issue for several reasons: from its prevalence (20% of total mortality in the industrialized world) to the devastating psycho-social impact on society and on the families of victims often still in their prime, and it represents a challenge for medicine, and especially for cardiology. This text summarizes the discussions and opinions of a group of investigators with a long-standing interest in this field. We addressed the occurrence of SCD in individuals apparently healthy, in patients with heart disease and mild or severe cardiac dysfunction, and in those with genetically based arrhythmic diseases. Recognizing the need for more accurate registries of the global and regional distribution of SCD in these different categories, we focused on the assessment of risk for SCD in these four groups, looking at the significance of alterations in cardiac function, of signs of electrical instability identified by ECG abnormalities or by autonomic tests, and of the progressive impact of genetic screening. Special attention was given to the identification of areas of research more or less likely to provide useful information, and thereby more or less suitable for the investment of time and of research funds.

Is the 12-lead electrocardiogram during antidromic circus movement tachycardia helpful in predicting the ablation site in atriofascicular pathways?

AIMS: Unlike in the Wolff-Parkinson-White syndrome, there has been no systematic study on the role of the pre-excitation pattern in predicting the ablation site in patients with atriofascicular (AF) pathways. We assessed in a large cohort the value of the 12-lead electrocardiogram (ECG) during antidromic tachycardia (ADT) to predict the site of ablation. METHODS AND RESULTS: Forty-five patients were studied, 23 males (51%), mean age of 27 ± 12 years with 46 AF pathways and 48 ADT using the AF pathway for A-V conduction. Inclusion required induction of a sustained ADT and successful ablation. Ablation site was assessed during LAO 45° projection and clockwise classified as hours in posteroseptal, posterolateral, lateral, anterolateral, and anteroseptal tricuspid annulus as follows: 05:00-07:00, >07:00-08:00, >08:00-09:00, >09:00-11:00, and >11:00-13:00 o'clock. The QRS axis was assessed during ADT and classified as normal (>+15°), horizontal (+15° to -30°), and superior (<-30°). During ADT axis was superior (-57° ± 10°) in 15 (31%), horizontal (-11° ± 14°) in 22 (46%), and normal (+45° ± 16°) in 11 (23%) patients. The correct ablation site did not differ between the different groups of QRS axis. QRS width during ADT was narrower in patients with a normal when compared with a horizontal and leftward axis (127 ± 14 vs. 145 ± 12 ms, P < 0.0001), and the V-H interval was shorter (4 ± 3 ms vs. 19 ± 22 ms, P = 0.03). CONCLUSIONS: There was no correlation between the AF pathway ablation site and the QRS axis during ADT. The 12-lead ECG during maximal pre-excitation does not predict the proper site of tricuspid annulus ablation in patients with A-V conduction over an AF pathway.

Radiological and electrocardiographic characterization of right ventricular outflow tract pacing.

AIMS: The right ventricular outflow tract (RVOT) is used as an alternative pacing site, but its superiority to the RV apex remains to be established. This lack of proof may in part be explained by heterogeneity within the RVOT-paced group, due to poor definitions of the RVOT. The aim of the present study is to characterize the RVOT in terms of fluoroscopic and electrocardiographic parameters. METHODS AND RESULTS: One hundred and forty-three patients who underwent pacemaker implantation with a ventricular lead in the RVOT were included. Lead position was determined by fluoroscopy. The RVOT was divided into three areas: anterior, septal, and free wall (FW). On a 12-lead electrocardiogram (ECG) during forced ventricular pacing, QRS duration, configuration, and amplitude was determined. Lead position was judged to be anterior in 52 (36%), septal in 43 (30%), and FW in 48 (34%) patients, respectively. QRS duration is not significantly different between groups. QRS axis differs significantly between pacing sites (septal 79 ± 31°, anterior 60 ± 46°, FW 47 ± 38°, P < 0.05). QRS vector in lead I and QRS morphology and vector in lead aVL differ significantly between pacing sites. Precordial transition is earlier (towards V1) in septal pacing. CONCLUSIONS: This study demonstrates heterogeneity of pacing site and depolarization pattern within a cohort of patients paced form the RVOT. However, due to considerable overlap, we could not define clear cut-off point or devise flow-charts to match ECG and pacing site.

Reperfusion ventricular arrhythmia 'bursts' predict larger infarct size despite TIMI 3 flow restoration with primary angioplasty for anterior ST-elevation myocardial infarction.

Aims Successful epicardial reperfusion with primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI) can paradoxically evoke myocardial reperfusion injury, which may be signalled by temporally associated ventricular arrhythmias (VAs). We correlated reperfusion VA 'bursts' with final infarct size (IS) in patients with restored TIMI 3 flow following PCI for anterior STEMI. Methods and results All 128 anterior STEMI patients with final TIMI 3 flow had continuous 24 h digital 12-lead ECG with simultaneous Holter recording initiated prior to PCI, and Day 7/discharge SPECT imaging IS assessment. Angiography, SPECT imaging, continuous ST recovery, and quantitative rhythm analyses were performed. Reperfusion VA bursts were defined against patient-specific background VA rates and timed as concomitant with or following first angiographic TIMI 3 flow restoration associated with > or =50% stable ST recovery; they were then correlated with IS and global left ventricular ejection fraction (LVEF) at Day 7/discharge. Bursts occurred in 81/128 (63%) patients and were significantly correlated with larger IS and worse LVEF (median: 21.0 vs. 10.0%, P < 0.001; 35.5 vs. 46.5%, P < 0.001, respectively). In multivariable analyses that adjusted for known predictors of IS, the association of bursts with larger IS remained significant; similar results were seen for worse LVEF. Conclusion Reperfusion VA bursts predict larger IS despite TIMI 3 flow restoration with > or =50% stable ST recovery following PCI for anterior STEMI. Well-characterized reperfusion VAs may provide a novel biomarker of reperfusion injury.

Long-Term Outcome of the Randomized DAPA Trial.

BACKGROUND: The randomized DAPA trial (Defibrillator After Primary Angioplasty) aimed to evaluate the survival benefit of prophylactic implantable cardioverter defibrillator (ICD) implantation in early selected high-risk patients after primary percutaneous coronary intervention for ST-segment-elevation myocardial infarction. METHODS: A randomized, multicenter, controlled trial compared ICD versus conventional medical therapy in high-risk patients with primary percutaneous coronary intervention, based on one of the following factors: left ventricular ejection fraction <30% within 4 days after ST-segment-elevation myocardial infarction, primary ventricular fibrillation, Killip class ≥2 or TIMI (Thrombolysis in Myocardial Infarction) flow <3 after percutaneous coronary intervention. ICD was implanted 30 to 60 days after MI. Primary end point was all-cause mortality at 3 years follow-up. The trial prematurely ended after inclusion of 266 patients (38% of the calculated sample size). Additional survival assessment was performed in February 2019 for the primary end point. RESULTS: A total of 266 patients, 78.2% males, with a mean age of 60.8±11.3 years, were enrolled. One hundred thirty-one patients were randomized to the ICD arm and 135 patients to the control arm. All-cause mortality was significant lower in the ICD group (5% versus 13%, hazard ratio, 0.37 [95% CI, 0.15-0.95]) after 3 years follow-up. Appropriate ICD therapy occurred in 9 patients at 3 years follow-up (5 within the first 8 months after implantation). After a median long-term follow-up of 9 years (interquartile range, 3-11), total mortality (18% versus 38%; hazard ratio, 0.58 [95% CI, 0.37-0.91]), and cardiac mortality (hazard ratio, 0.52 [95% CI, 0.28-0.99]) was significant lower in the ICD group. Noncardiac death was not significantly different between groups. Left ventricular ejection fraction increased ≥10% in 46.5% of the patients during follow-up, and the extent of improvement was similar in both study groups. CONCLUSIONS: In this prematurely terminated and thus underpowered randomized trial, early prophylactic ICD implantation demonstrated lower total and cardiac mortality in patients with high-risk ST-segment-elevation myocardial infarction treated with primary percutaneous coronary intervention. Registration: URL: https://www.trialregister.nl; Unique identifier: Trial NL74 (NTR105).

Left bundle-branch block with right axis deviation--a unique aberrancy during supraventricular tachycardia.

A tachycardia with left bundle-branch block morphology and right axis deviation points to the diagnosis of ventricular tachycardia. Conversely, any supraventricular tachycardia with left bundle-branch block is typically associated with a normal or leftward QRS axis. We present the case of a 34-year-old man showing atrioventricular nodal reentrant tachycardia with left bundle-branch block/right axis deviation as an exception to this rule.

Can common-type atrial flutter be a sign of an arrhythmogenic substrate in paroxysmal atrial fibrillation? Clinical and ablative consequences in patients with coexistent paroxysmal atrial fibrillation/atrial flutter.

BACKGROUND: The coexistence of atrial fibrillation (AF) and atrial flutter (AFL) is well recognized. AF precedes the onset of AFL in almost all instances. We evaluated the effect of 2 ablation strategies in patients with paroxysmal AF (PAF) and AFL. METHODS AND RESULTS: Ninety-eight patients with PAF/AFL were prospectively recruited to undergo pulmonary vein cryoisolation (PVI). Those with at least 1 episode of sustained common-type AFL were assigned to cavotricuspid isthmus cryoablation followed by a 6-week monitoring period and a subsequent PVI (n=36; group I). Patients with PAF only underwent PVI (n=62; group II). The study included 76 men with a mean age of 50+/-10 years. Most patients (76 [78%]) had no structural heart disease. When the 2 groups were compared, residual AF after a blanking period of 3 months after PVI occurred in 24 patients (67%) in group I versus 7 (11%) in group II (P<0.05). CONCLUSIONS: In patients with PAF and no documented common-type AFL, PVI alone prevented the occurrence of AF in 82%, whereas in patients with AFL/PAF, cavotricuspid isthmus cryoablation and PVI were used successfully to treat sustained common-type AFL but appeared to be insufficient to prevent recurrences of AF. In this population, AFL can be a sign that non-pulmonary vein triggers are the culprit behind AF or that sufficient electrical remodeling has already occurred in both atria, and thus a strategy that includes substrate modification may be required.