Outcomes with Physiologic His Bundle Pacing in Patients with Narrow QRS Complex.

BACKGROUND: In patients with narrow QRS complex, both ventricular and biventricular pacing is associated with increased cardiac morbidity and mortality. This risk is not decreased by ventricular pacing avoidance algorithms which cause non-physiologic atrioventricular delays. OBJECTIVE: To report outcomes in patients with narrow QRS complex, when paced complex is in normal range and physiologic atrioventricular delays are programmed. METHODS: In 196 patients with QRS duration of 92 ± 10 msec, permanent pacing was done at site of His bundle electrogram. The pacemakers were then programmed to maintain physiologic AV delays and increase heart rates in response to exercise. Patients received usual care and were followed for 3-years. RESULTS: The paced complex exhibited a delta wave and the ventricular activation time, QRS axis and lead-I voltage remained in normal range. Physiologic programming resulted in His bundle pacing burden of 92%. In patients with decreased ejection fraction, there was significant improvement in left ventricular function, left ventricular dilatation and mitral regurgitation (p <0.003). In patients with normal ejection fraction, left ventricular function remained normal without new valvular abnormalities. The 3-year all-cause mortality was 10%, and there was no increase in heart failure admissions. CONCLUSION: In patients with narrow QRS complex, when paced QRS morphology is maintained in normal range and atrio-ventricular dyssynchrony is avoided, His bundle pacing is associated with a low all-cause mortality and improvement in abnormal echocardiographic parameters. The paced QRS morphology and physiologic atrioventricular delays may be important factors to evaluate in future trials of conduction system pacing.

Evidence for concealed fasciculo-ventricular connections as revealed by His bundle pacing.

BACKGROUND: It is almost 100 years ago since Mahaim described the so-called paraspecific connections between the ventricular conduction axis and the crest of the muscular ventricular septum, believing such pathways to be ubiquitous. These pathways, however, have yet to be considered as potential pathways for septal activation during His bundle pacing. MATERIALS: So as to explore the hypothesis that specialised septal pathways might provide the substrate for septal activation during His bundle pacing, we compared the findings from 22 serially sectioned histological datasets and 34 different individuals undergoing His bundle pacing. RESULTS: We found histologically specialised pathways connecting the branching component of the atrioventricular conduction axis with the crest of the muscular ventricular septum in almost four-fifths of the histological datasets. In 32 of 34 patients undergoing His bundle pacing, the QRS complex closely resembled published images of known conduction through fasciculo-ventricular pathways. In only two patients was a delta wave not seen at any pacing voltages. Capture of these connections varied according to pacing voltage, a finding which correlated with the distance of the pathways from the site of penetration of the ventricular conduction axis. Ventricular activation times remained normal in the presence of the delta wave at higher pacing voltage but were prolonged at lower voltages. CONCLUSIONS: Our histologic findings confirm fasciculo-ventricular connections, initially described by Mahaim as being paraspecific, are likely ubiquitous. Analysis of 12-lead electrocardiograms leads us to conclude that fasciculo-ventricular pathways, concealed during sinus rhythm, become manifest with His bundle pacing.

Confounding factors leading to misdiagnosing ventricular tachycardia as supraventricular in the emergency room.

Studies conducted during the last 50 years have proposed electrocardiographic criteria and algorithms to determine if a wide QRS tachycardia is ventricular or supraventricular in origin. Sustained ventricular tachycardia is an uncommon reason for consultation in the emergency room. The latter and the complexity of available electrocardiographic diagnostic criteria and algorithms result in frequent misdiagnoses. Good hemodynamic tolerance of tachycardia in the supine position does not exclude its ventricular origin. Although rare, ventricular tachycardia in patients with and without structural heart disease may show a QRS duration <120 ms. Interruption of tachycardia by coughing, carotid sinus massage, Valsalva maneuver, or following the infusion of adenosine or verapamil should not discard the ventricular origin of the arrhythmia. In patients with regular, uniform, sustained broad QRS tachycardia, the presence of structural heart disease or A-V dissociation strongly suggest its ventricular origin. Occasionally, ventricular tachycardia can present with AV dissociation without this being evident on the 12-lead ECG. Cardiac auscultation, examination of the jugular venous pulse, and arterial pulse palpation provide additional clues for identifying A-V dissociation during tachycardia. This paper does not review the electrocardiographic criteria for categorizing tachycardia as ventricular but rather why emergency physicians misdiagnose these patients.

Acometimento do Ventrículo Direito na Cardiomiopatia por Depósito de Glicogênio (PRKAG2): Análise Ecocardiográfica Convencional e Avançada / Right Ventricle Involvement by Glycogen Storage Cardiomyopathy (PRKAG2): Standard and Advanced Echocardiography Analyses

Resumo Fundamento A síndrome do PRKAG2 é uma doença hereditária autossômica dominante rara, de início precoce. Objetivamos descrever os achados ecocardiográficos do ventrículo direito (VD) usando modalidades bi e tridimensionais (2D e 3D), incluindo índices de deformação miocárdica nesta cardiomiopatia. Também objetivamos demonstrar se esta técnica poderia identificar alterações na função do VD que pudessem distinguir quaisquer achados particulares. Métodos Trinta pacientes com síndrome do PRKAG2 (R302Q e H401Q) geneticamente comprovada, 16 (53,3%) do sexo masculino, com idade média de 39,1 ± 15,4 anos, foram submetidos a exame ecocardiográfico completo. A visão de 4 câmaras com foco no VD foi adquirida para medições 2D e 3D. Os testes t de Student ou Wilcoxon-Mann-Whitney foram usados para comparar as variáveis numéricas entre 2 grupos, e p < 0,05 foi considerado significativo. Resultados Doze pacientes (40%) tiveram marca-passo implantado por 12,4 ± 9,9 anos. A espessura diastólica média da parede livre do VD foi de 7,9 ± 2,9 mm. O strain longitudinal de 4 câmaras do VD (SL4VD), incluindo a parede livre e o septo interventricular, foi de -17,3% ± 6,7%, e o strain longitudinal da parede livre do VD (SLPLVD) foi de −19,1% ± 8,5%. A razão apical do SLPLVD mediu 0,63 ± 0,15. A fração de ejeção (FE) 3D média do VD foi de 42,6% ± 10,9% e abaixo dos limites normais em 56,7% dos pacientes. Correlação positiva ocorreu entre FE 3D do VD, SL4VD e SLPLVD, principalmente para pacientes sem marca-passo (p = 0,006). Conclusão O envolvimento do VD em PRKAG2 é frequente e ocorre em diferentes graus. A ecocardiografia é uma ferramenta valiosa na detecção de anormalidades miocárdicas do VD nesta condição. O uso de SL4VD 2D, SLPLVD e FE 3D oferecem indicadores confiáveis de disfunção sistólica do VD nesta cardiomiopatia rara e desafiadora.

Abstract Background PRKAG2 syndrome is a rare, early-onset autosomal dominant inherited disease. We aimed to describe the right ventricle (RV) echocardiographic findings using two and three-dimensional (2D and 3D) modalities including myocardial deformation indices in this cardiomyopathy. We also aimed to demonstrate whether this technique could identify changes in RV function that could distinguish any particular findings. Methods Thirty patients with genetically proven PRKAG2 (R302Q and H401Q), 16 (53.3%) males, mean age 39.1 ± 15.4 years, underwent complete echocardiography examination. RV-focused, 4-chamber view was acquired for 2D and 3D measurements. Student's t or Wilcoxon-Mann-Whitney tests were used to compare numerical variables between 2 groups, and p < 0.05 was considered significant. Results Twelve patients (40%) had a pacemaker implanted for 12.4 ± 9.9 years. RV free wall mean diastolic thickness was 7.9 ± 2.9 mm. RV 4-chamber longitudinal strain (RV4LS), including the free wall and interventricular septum, was -17.3% ± 6.7%, and RV free wall longitudinal strain (RVFWLS) was −19.1% ± 8.5%. The RVFWLS apical ratio measured 0.63 ± 0.15. Mean RV 3D ejection fraction (EF) was 42.6% ± 10.9% and below normal limits in 56.7% of patients. Positive correlation occurred between RV 3DEF, RV4LS, and RVFWLS, especially for patients without a pacemaker (p = 0.006). Conclusion RV involvement in PRKAG2 syndrome is frequent, occurring in different degrees. Echocardiography is a valuable tool in detecting RV myocardial abnormalities in this condition. The use of 2D RV4LS, RVFWLS, and 3DEF offers reliable indicators of RV systolic dysfunction in this rare, challenging cardiomyopathy.

Right Ventricle Involvement by Glycogen Storage Cardiomyopathy (PRKAG2): Standard and Advanced Echocardiography Analyses. / Acometimento do Ventrículo Direito na Cardiomiopatia por Depósito de Glicogênio (PRKAG2): Análise Ecocardiográfica Convencional e Avançada.

BACKGROUND: PRKAG2 syndrome is a rare, early-onset autosomal dominant inherited disease. We aimed to describe the right ventricle (RV) echocardiographic findings using two and three-dimensional (2D and 3D) modalities including myocardial deformation indices in this cardiomyopathy. We also aimed to demonstrate whether this technique could identify changes in RV function that could distinguish any particular findings. METHODS: Thirty patients with genetically proven PRKAG2 (R302Q and H401Q), 16 (53.3%) males, mean age 39.1 ± 15.4 years, underwent complete echocardiography examination. RV-focused, 4-chamber view was acquired for 2D and 3D measurements. Student's t or Wilcoxon-Mann-Whitney tests were used to compare numerical variables between 2 groups, and p < 0.05 was considered significant. RESULTS: Twelve patients (40%) had a pacemaker implanted for 12.4 ± 9.9 years. RV free wall mean diastolic thickness was 7.9 ± 2.9 mm. RV 4-chamber longitudinal strain (RV4LS), including the free wall and interventricular septum, was -17.3% ± 6.7%, and RV free wall longitudinal strain (RVFWLS) was -19.1% ± 8.5%. The RVFWLS apical ratio measured 0.63 ± 0.15. Mean RV 3D ejection fraction (EF) was 42.6% ± 10.9% and below normal limits in 56.7% of patients. Positive correlation occurred between RV 3DEF, RV4LS, and RVFWLS, especially for patients without a pacemaker (p = 0.006). CONCLUSION: RV involvement in PRKAG2 syndrome is frequent, occurring in different degrees. Echocardiography is a valuable tool in detecting RV myocardial abnormalities in this condition. The use of 2D RV4LS, RVFWLS, and 3DEF offers reliable indicators of RV systolic dysfunction in this rare, challenging cardiomyopathy.

FUNDAMENTO: A síndrome do PRKAG2 é uma doença hereditária autossômica dominante rara, de início precoce. Objetivamos descrever os achados ecocardiográficos do ventrículo direito (VD) usando modalidades bi e tridimensionais (2D e 3D), incluindo índices de deformação miocárdica nesta cardiomiopatia. Também objetivamos demonstrar se esta técnica poderia identificar alterações na função do VD que pudessem distinguir quaisquer achados particulares. MÉTODOS: Trinta pacientes com síndrome do PRKAG2 (R302Q e H401Q) geneticamente comprovada, 16 (53,3%) do sexo masculino, com idade média de 39,1 ± 15,4 anos, foram submetidos a exame ecocardiográfico completo. A visão de 4 câmaras com foco no VD foi adquirida para medições 2D e 3D. Os testes t de Student ou Wilcoxon-Mann-Whitney foram usados para comparar as variáveis numéricas entre 2 grupos, e p < 0,05 foi considerado significativo. RESULTADOS: Doze pacientes (40%) tiveram marca-passo implantado por 12,4 ± 9,9 anos. A espessura diastólica média da parede livre do VD foi de 7,9 ± 2,9 mm. O strain longitudinal de 4 câmaras do VD (SL4VD), incluindo a parede livre e o septo interventricular, foi de -17,3% ± 6,7%, e o strain longitudinal da parede livre do VD (SLPLVD) foi de −19,1% ± 8,5%. A razão apical do SLPLVD mediu 0,63 ± 0,15. A fração de ejeção (FE) 3D média do VD foi de 42,6% ± 10,9% e abaixo dos limites normais em 56,7% dos pacientes. Correlação positiva ocorreu entre FE 3D do VD, SL4VD e SLPLVD, principalmente para pacientes sem marca-passo (p = 0,006). CONCLUSÃO: O envolvimento do VD em PRKAG2 é frequente e ocorre em diferentes graus. A ecocardiografia é uma ferramenta valiosa na detecção de anormalidades miocárdicas do VD nesta condição. O uso de SL4VD 2D, SLPLVD e FE 3D oferecem indicadores confiáveis de disfunção sistólica do VD nesta cardiomiopatia rara e desafiadora.

Mahaim Revisited.

The name Ivan Mahaim is well-known to electrophysiologists. However, alternative anatomical substrates can produce the abnormal rhythms initially interpreted on the basis of the pathways he first described. These facts have prompted suggestions that Mahaim should be deprived of his eponym. It is agreed that specificity is required when describing the pathways that produce the disordered cardiac conduction, and that the identified pathways should now be described in an attitudinally appropriate fashion. The authors remain to be convinced that understanding will be enhanced simply by discarding the term 'Mahaim physiology' from the lexicon. It is fascinating to look back at the history of accessory atrioventricular junctional conduction pathways outside the normal accessory atrioventricular conduction system, and their possible role in rhythm disturbances. It took both the anatomist and the clinical arrhythmologist quite some time to understand the complex anatomical architecture and the ensuing electrophysiological properties. Over the years, the name Mahaim was often mentioned in those discussions, although these pathways were not the ones that produced the eponym. The reason for this review, therefore, is to present relevant information about the person and what followed thereafter.

How does the cardiac impulse pass from the sinus to the atrioventricular node?

More than a century has passed since Tawara demonstrated the presence of the insulated pathways that extend from the "knoten" at the base of the atrial septum to their ramifications at the ventricular apexes. Having initially doubted the existence of the atrioventricular bundle until reading the monograph produced by Tawara, Keith, together with Flack, soon revealed the presence of the sinus node. Shortly thereafter, Thorel suggested that a special system might be found within the atrial walls, connecting the newly discovered atrial nodes. This prompted the convening of a special session of the German Pathological Society in 1910. The consensus was that no tracts existed within the atrial walls, with Aschoff and Mönckeberg establishing criteria to be met by those proposing recognition of "specialized" atrial conducting pathways. None of those who subsequently proposed the presence of such pathways have discussed their findings on the basis of the criteria established at the meeting of 1910. It remains the case, nonetheless, that drawings continue to be offered by cardiological experts showing narrow pathways within the atrial walls that parallel the arrangement used to show the ventricular conduction pathways. A similar drawing adorns the front cover of Heart Rhythm Journal. We are unaware of any evidence supporting the presence of pathways as illustrated existing within the overall walls of the atrial chambers. In this review, we summarize the evidence that shows, instead, that it is the aggregation of the working atrial cardiomyocytes within the atrial walls that underscores preferential anisotropic interatrial conduction.

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 1-Part III: 'Behind the scenes' in the triangle of Koch.

AIMS: To take full advantage of the knowledge of cardiac anatomy, structures should be considered in their correct attitudinal orientation. Our aim was to discuss the triangle of Koch in an attitudinally appropriate fashion. METHODS AND RESULTS: We reviewed our material prepared by histological sectioning, along with computed tomographic datasets of human hearts. The triangle of Koch is the right atrial surface of the inferior pyramidal space, being bordered by the tendon of Todaro and the hinge of the septal leaflet of the tricuspid valve, with its base at the inferior cavotricuspid isthmus. The fibro-adipose tissues of the inferior pyramidal space separate the atrial wall from the crest of the muscular interventricular septum, thus producing an atrioventricular muscular sandwich. The overall area is better approached as a pyramid rather than a triangle. The apex of the inferior pyramidal space overlaps the infero-septal recess of the subaortic outflow tract, permitting the atrioventricular conduction axis to transition directly to the crest of the muscular ventricular septum. The compact atrioventricular node is formed at the apex of the pyramid by union of its inferior extensions, which represent the slow pathway, with the septal components formed in the buttress of the atrial septum, thus providing the fast pathway. CONCLUSIONS: To understand its various implications in current cardiological catheter interventions, the triangle of Koch must be considered in conjunction with the inferior pyramidal space and the infero-septal recess. It is better to consider the overall region in terms of a pyramidal area of interest.

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.