Conduction System Abnormalities After Transcatheter Aortic Valve Replacement: Mechanism, Prediction, and Management.

Conduction disturbances following TAVR are a common occurrence given the proximity of the various conduction system tissues, including the AV node, His-bundle, and bundle branches to the left ventricular outflow tract and aortic root. Impairment of these conduction system abnormalities may necessitate permanent pacemaker implantation, which increases morbidity and mortality, as well as length of stay, for the patient. The incidence, mechanisms, and predictors of conduction abnormalities and treatment options are discussed in this up-to-date review of the topic.

An Imaging Protocol to Discriminate Specialized Conduction Tissue During Congenital Heart Surgery.

We performed preclinical validation of intraoperative fiber-optic confocal microscopy (FCM) and assessed its safety and efficacy in an ovine model of the pediatric heart. Intraoperative imaging was performed using an FCM system (Cellvizio, Mauna Kea Technology, Paris, France) with specialized imaging miniprobe (GastroFlex UHD, Mauna Kea Technologies). Before imaging, we applied an extracellular fluorophore, sodium fluorescein, to fluorescently label extracellular space. We imaged arrested hearts of ovine (1-6 months) under cardiopulmonary bypass. Image sequences (1-10 seconds duration) were acquired from regions of the sinoatrial and atrioventricular node, as well as subepicardial and subendocardial working myocardium from atria and ventricle. The surgical process was evaluated for integration of the imaging protocol during the operative procedure. In addition, fluorescein cardiotoxicity studies (n = 3 animals) were conducted by comparing electrocardiogram (PR and QRS intervals) and ejection fraction at baseline and after topical application of fluorescein at 1:10, 1:100, and 1:1000 dilutions on a beating ovine heart. Our studies suggest that intraoperative FCM can be used to identify regions associated with specialized conducting tissue in ovine hearts in situ. The imaging protocol was integrated with conventional open heart surgical procedures with minimal changes to the operative process. Application of fluorescein in varying concentrations did not affect the normalized PR interval, QRS interval, and ejection fraction. These preclinical validation studies demonstrated both safety and efficacy of the proposed intraoperative imaging approach. The studies constitute an important step toward first-in-human clinical trials.

Five seconds of 50-60 W radio frequency atrial ablations were transmural and safe: an in vitro mechanistic assessment and force-controlled in vivo validation.

AIMS: Longer procedural time is associated with complications in radiofrequency atrial fibrillation ablation. We sought to reduce ablation time and thereby potentially reduce complications. The aim was to compare the dimensions and complications of 40 W/30 s setting to that of high-power ablations (50-80 W) for 5 s in the in vitro and in vivo models. METHODS AND RESULTS: In vitro ablations-40 W/30 s were compared with 40-80 W powers for 5 s. In vivo ablations-40 W/30 s were compared with 50-80 W powers for 5 s. All in vivo ablations were performed with 10 g contact force and 30 mL/min irrigation rate. Steam pops and depth of lung lesions identified post-mortem were noted as complications. A total of 72 lesions on the non-trabeculated part of right atrium were performed in 10 Ovine. All in vitro ablations except for the 40 W/5 s setting achieved the critical lesion depth of 2 mm. For in vivo ablations, all lesions were transmural, and the lesion depths for the settings of 40 W/30 s, 50 W/5 s, 60 W/5 s, 70 W/5 s, and 80 W/5 s were 2.2 ± 0.5, 2.3 ± 0.5, 2.1 ± 0.4, 2.0 ± 0.3, and 2.3 ± 0.7 mm, respectively. The lesion depths of short-duration ablations were similar to that of the conventional ablation. Steam pops occurred in the ablation settings of 40 W/30 s and 80 W/5 s in 8 and 11% of ablations, respectively. Complications were absent in short-duration ablations of 50 and 60 W. CONCLUSION: High-power, short-duration atrial ablation was as safe and effective as the conventional ablation. Compared with the conventional 40 W/30 s setting, 50 and 60 W ablation for 5 s achieved transmurality and had fewer complications.

Comparison of the QRS Complex, ST-Segment, and T-Wave Among Patients with Left Bundle Branch Block with and without Acute Myocardial Infarction.

BACKGROUND: The modified Sgarbossa criteria have been validated as a rule for diagnosis of acute coronary occlusion (ACO) in left bundle branch block (LBBB). However, no analysis has been done on differences in the QRS complex, T-wave, or ST-segment concordance of < 1 mm in the derivation or validation studies. Furthermore, there was no comparison of patients with acute myocardial infarction (AMI) but without ACO (i.e., non-ST-elevation myocardial infarction [non-STEMI]) to patients with ACO or without AMI (no MI). OBJECTIVE: We compare findings involving the QRS amplitude, ST-segment morphology, ST-concordance < 1 mm, and T-waves in patients with LBBB with ACO, non-STEMI, and no MI. METHODS: Retrospectively, emergency department patients were identified with LBBB and ischemic symptoms but no MI, with angiographically proven ACO, and with non-STEMI. RESULTS: ACO, non-STEMI, and no MI groups consisted of 33, 24, and 105 patients. The sum of the maximum deflection of the QRS amplitude across all leads (ΣQRS) was smaller in patients with ACO than those without ACO (101.5 mm vs. 132.5 mm; p < 0.0001) and a cutoff of ΣQRS < 90 mm was 92% specific. For ACO, non-concave ST-segment morphology was 91% specific, any ST concordance ≥ 1 mm was 95% specific, and any ST concordance ≥ 0.5 mm was 94% sensitive. For non-STEMI, terminal T-wave concordance, analogous to biphasic T-waves, was moderately sensitive at 79%. CONCLUSIONS: We found differences in QRS amplitude, ST-segment morphology, and T-waves between patients with LBBB and ACO, non-STEMI, and no MI. However, none of these criteria outperformed the modified Sgarbossa criteria for diagnosis of ACO in LBBB.

Aortic root rupture: implications of catheter-guided aortic valve replacement.

PURPOSE OF REVIEW: The safety and efficiency of trans catheter aortic valve implantation (TAVI) has been clearly demonstrated. In high-risk patients, the number of procedures is constantly increasing and in western European countries this procedure is employed in more than 30% of isolated aortic valve replacements. The literature, however, focusing on perioperative aortic root (AoR) rupture is rather limited to just a few reports. The aim of this review is to analyze the pathophysiology of AoR rupture during TAVI, stressing the implications of the morphology of the AoR for this devastating complication. RECENT FINDINGS: Currently, perioperative AoR rupture ranges between 0.5 and 1.5% during TAVI, with almost 100% mortality. Recently, valve oversizing and balloon dilatation in a calcified and small AoR were considered as the most important predictive factors for this complication. SUMMARY: The most fragile unit of the AoR is its anchoring substrate to the ostium of the left ventricle. This membranous structure is not involved in the degenerative process leading to aortic valve stenosis. Due to the TAVI and/or balloon dilatation of the calcium stationed on the three leaflets and their attachment, a lesion may result on this structure. And, as a consequence, there is rupture of the AoR.

Cryoablation: how to improve results in atrioventricular nodal reentrant tachycardia ablation?

Ablation for atrioventricular nodal reentry tachycardia is very effective, with a potential for damage to the normal conduction system. Cryoablation is an alternative, as it allows cryomapping, which permits assessment of slow pathway elimination at innocent freezing temperatures, avoiding permanent damage to the normal conduction system. It is associated with shorter radiation times and the absence of heart block in all published data. We discuss in this overview different approaches of cryoenergy delivery (focusing on spot catheter ablation), and how lesion formation is influenced by catheter tip size, application duration, and freezing rate. Some advantages of cryoenergy are explained. Whether these features also apply for an approach with a cryoballoon, e.g. for atrial fibrillation is unclear.

The complete array of electrocardiogram abnormalities secondary to myocardial contusion in a single case.

Myocardial contusion is a complication of blunt thoracic injuries. Transthoracic echocardiography and electrocardiography (ECG) monitoring are important in suspected cases. We report a 54-year-old man, who sustained a number of injuries including blunt chest injury as a consequence of a road traffic accident. Electrocardiography monitoring over a 48 h period demonstrated sequential degrees of conduction system block coupled with a temporary cardio-version from persistent atrial fibrillation to sinus rhythm, suggesting coincident pulmonary vein contusion.

Coronary vasospasm triggered ventricular fibrillation delayed after radiofrequency ablation of the right accessory pathway.

Ventricular fibrillation associated with coronary vasospasm developed 8 h after successful radiofrequency (RF) ablation of the right accessory pathway in an 81-year-old male. A segment of the coronary vasospasm was located close to the accessory pathway, where seven RF ablations had been applied. Although rare, physicians should carefully consider the risk of such events when an RF current is applied near a coronary artery.

Macroreentrant atrial tachycardia with an isolated pathway mimicking focal activation on three-dimensional electroanatomical mapping.

A 76-year-old man with two different sustained atrial arrhythmias that occurred after coronary artery bypass grafting underwent electrophysiological studies. Macroreentrant atrial tachycardias were detected with an isolated slow pathway mimicking focal activation on three-dimensional electroanatomical mapping. The slow conduction pathway in the right atrial free wall was assumed to represent tissue damaged by right atrial cannulation during previous coronary artery bypass grafting.

Catheter-induced mechanical trauma to fast and slow pathways during radiofrequency ablation of atrioventricular nodal reentry tachycardia: incidence, predictors, and clinical implications.

BACKGROUND: Data on the incidence and significance of catheter-induced trauma to fast and slow pathways are scarce. OBJECTIVES: To evaluate the incidence, predictors, and clinical implications of inadvertent catheter-induced mechanical trauma to fast and slow pathways during radiofrequency ablation (RFA) of atrioventricular nodal reentry tachycardia (AVNRT). METHODS: A total of 901 consecutive patients (aged 9-92 years old) with inducible sustained AVNRT underwent RFA of the slow pathway. All procedures were closely monitored for appearance of catheter-induced mechanical block of fast or slow pathways. RESULTS: Catheter-induced mechanical trauma to fast and/or slow pathways was observed in 121 (13.4%) patients: 86 (71%) patients had trauma of the fast pathway, three (2.4%) had trauma of the slow pathway, and 32 (26.4%) had trauma of both pathways. Mechanical trauma lasted <1 minute in 87 (72%) patients, 1-30 minutes in 23 (19%) and >30 minutes in 11 (9%). A significantly increased procedure discontinuation rate was observed in patients with mechanical trauma as compared to those with no trauma (P < 0.0001). Young patient age (<35) was a strong predictor for the occurrence of mechanical trauma to AV nodal pathways. No significant difference between the trauma and non-trauma groups was found in respect to the number of catheters used during the procedure, the incidence of AV block, and the need for permanent pacemaker implantation. CONCLUSIONS: Mechanical trauma to fast and slow pathways during ablation of AVNRT is more common than previously recognized, occurring especially in patients aged <35 years.

Myocardial injury due to lightning strike--a case report.

Lightning strike is a natural phenomenon with potentially devastating effects and represents one of the leading causes of cardiac arrest and death from environmental phenomena. Almost every organ system may be impaired as lightning passes through the human body taking the shortest pathways between the contact points. In this paper, the authors report a 38-year-old man who was injured by lightning, a typical example of ;;side splash,'' and had transient electrocardiographic changes.

Relationship between cardiopulmonary resuscitation and injuries of the cardiac conduction system: pathological features and pathogenesis of such injuries.

OBJECTIVE: The purpose of this study was to assess the incidence, features, and pathogenesis of microscopic injuries to the cardiac conduction system caused by cardiopulmonary resuscitation. DESIGN: : Prospective study. SETTING: Autopsy unit of the university. PATIENTS: Victims who had been transferred to the emergency room due to cardiac arrest arising from nontraumatic cause plus age-matched control patients. INTERVENTIONS: None. MEASUREMENT AND MAIN RESULTS: The cardiac conduction system of 80 hearts without gross injury from patients who had received cardiopulmonary resuscitation due to nontraumatic causes was examined. Of these 80 patients, seven (9%) showed fresh injuries, including a lesion that had gone unreported in the previous literature. Localized hemorrhage without inflammatory reaction was evident in six of these patients. Three of the six patients showed hemorrhage in the sinoatrial node, whereas the other three patients showed hemorrhage in the atrioventricular conduction system. The remaining one patient showed localized dissection of the atrioventricular node artery with the appearance of red blood cells in the false lumen. There was no significant difference with regard to age, gender, cause of cardiopulmonary arrest, whether victim had received electrical shock treatment, whether victim had received anticoagulants, and the duration of cardiopulmonary resuscitation between the seven patients with fresh injuries and the other 73 patients. Fracture of the sternum or rib was found in only one of the seven patients but in 14 of the 73 patients. No pathologic lesions were found in the 30 control patients who did not receive cardiopulmonary resuscitation. CONCLUSIONS: It can be presumed that injuries to the conduction system do occur in limited regions during cardiopulmonary resuscitation. Minute differences in the location of the cardiac silhouette or cardiac conduction system also need to be considered, rather than just the severity of force to the anterior chest, when determining the pathogenesis of these injuries.

Complete heart block during central venous catheter placement in a patient with pre-existing left bundle branch block.

Heart block and arrhythmia are complications of pulmonary artery and cardiac catheterization. Injury to the conducting system of the heart often involves the right bundle causing right bundle branch block (RBBB). If patients already have left bundle branch block (LBBB), complete heart block (CHB) may result. After trauma, impairment of the right bundle is usually transient with recovery in hours, but complete heart block can lead to symptoms requiring invasive treatment. Similar complications are rare with insertion of central venous catheters, as they should not enter the heart. Injury to the right bundle during central venous catheter insertion can be by trauma from the guide wire or from the catheter itself. The function of the AV node and bundle of His in these patients has not been studied before. We report a patient with LBBB who developed CHB during insertion of a central venous cannula. Conduction through the AV node and His-Purkinje system was intact, showing that the transient RBBB was caused by traumatic injury rather than by other disease of the conduction system.

Shallow stitching close to the rim of the ventricular septal defect eliminates injury to the right bundle branch.

BACKGROUND: Complete right bundle branch block carries a deleterious effect on the long-term outcome of patients who undergo surgical treatment of the perimembranous ventricular septal defect. We describe a novel suturing method to reduce the prevalence of complete right bundle branch block. METHODS: From March 1996 through December 2000, 48 consecutive patients with perimembranous ventricular septal defect underwent patch closure using shallow stitches placed close to the rim (group 1). The same number of patients was randomly selected from those who had previously undergone surgery using deep stitches placed distant from the rim (group 2). Postoperative electrocardiograms were reviewed to compare the prevalence of complete right bundle branch block between groups. A morphologic study of the conduction system was performed to identify the vulnerable segment of the right bundle branch where the surgical damage tended to occur. Additional analyses were made to determine whether younger age and right ventriculotomy increased the prevalence of complete right bundle branch block. RESULTS: The prevalence of complete right bundle branch block in group 1 (6.3%) was significantly (p < 0.0001) lower than in group 2 (43.8%). The result was consistent with the morphologic finding that stitches of group 2 tended to damage the right bundle branch and those of group 1 did not. The younger age and right ventriculotomy did not increase the prevalence of complete right bundle branch block. CONCLUSIONS: Shallow stitches placed close to the rim of the perimembranus ventricular septal defect eliminate injury to the right bundle branch.

Evaluation of post-repolarization refractoriness for conduction block in cardiac muscle: studies in an artificial isthmus in the canine right atrium.

Post-repolarization refractoriness (PRR) is an important factor in determining conduction block and is the difference between the effective refractory period (ERP) and the duration of the monophasic action potential (MAPD). In the present study, conduction block in an artificial isthmus in the canine atrium was evaluated and the coupling interval of a premature beat, which caused the block, was defined as the block coupling interval (BCI). The usefulness of this value was also evaluated. Radiofrequency linear ablation was performed on the right atrial surface parallel to the atrioventricular groove in 5 mongrel dogs, and an artificial isthmus (8-10mm wide and 25-30mm long) was created. Fourteen simultaneous unipolar recordings were performed in the isthmus with a resolution of 1.2 mm. Single extra-stimuli with basic drive train were delivered to induce conduction block in the isthmus and when it occurred, the coupling interval at the recording site just proximal to the site of the block was defined as the BCI. At the site of the block, the ERP and MAPD at each drive cycle length were measured. The PRR was calculated using 2 different formulae: (1) [ERP-MAPD], and (2) [BCI-MAPD]. It was found that each value was shortened in accordance with the shortening of the basic drive cycle length. In all basic drive trains, BCI>ERP>MAPD, and [ERP-MAPD] was always shorter than [BCI-MAPD]. In the shorter cycle length of basic drives, the difference between [ERP-MAPD] and [BCI-MAPD] was more prominent. In the artificial isthmus model in the canine atrium, BCI was always longer than the ERP measured at the same site as the block. Because the ERP may not directly reflect the block phenomenon, the electrophysiologic evaluation should use the BCI instead, as in the PRR evaluation.

Catheter-induced mechanical trauma to accessory pathways during radiofrequency ablation: incidence, predictors and clinical implications.

OBJECTIVES: To evaluate the incidence, predictors and clinical implications of nonintentionally catheter-induced mechanical trauma to accessory pathways during radiofrequency ablation procedures. BACKGROUND: Data on the incidence and significance of catheter-induced trauma to accessory pathways are scarce. METHODS: Consecutive patients (n = 381) undergoing radiofrequency ablation of accessory pathways at two different institutions were closely monitored for appearance of mechanical block of accessory pathways during catheter manipulation. RESULTS: Mechanical trauma to accessory pathways was observed in 37 (9.7%) patients. According to a multivariate analysis, the only independent variable associated with this phenomenon was the anatomical pathway location (p = 0.0001). The incidence of trauma of either right anteroseptal (38.5%) or right atriofascicular pathways (33.3%) was significantly greater than that of pathways (< or =10%) at all remaining locations (p < 0.0001). The duration of conduction block observed ranged from < or =1 min to >30 min in 19% and 35% of patients, respectively. "Immediate" application of radiofrequency pulses at sites of mechanical block (<1 min after occurrence) was associated with a 78% long-term success rate at follow-up. This contrasted with a 25% long-term success rate in patients in whom pulses were delivered 30 min after occurrence of block ("delayed pulses"). Finally, in 24% of patients persistent trauma-induced conduction block led to discontinuation of the ablation procedure. CONCLUSIONS: Trauma to accessory pathways is more common than previously recognized and frequently results in prolongation or discontinuation of the ablation procedure and in lower success rates. The only independent predictor of catheter-trauma to accessory pathways is the pathway location.