Alessio Borrelli

Different Automatic Mode Switching in DDDR Pacemakers

Mode-switching algorithms are designed to alleviate symptoms related to tracking of atrial arrhythmias, that may result in inappropriately rapid or irregular ventricular pacing[1–19]. The ideal mode-switching algorithm should discriminate sinus tachycardia, a rhythm that should be tracked, from pathological atrial arrhythmias, rhythms that generally should not be tracked. In order to minimize symptoms related to the occurrence of atrial arrhythmias, the mode-switching algorithm should change quickly from a tracking to a non-tracking mode at the onset of the pathological atrial rhythm and remains in this mode until the arrhythmia terminates. Once sinus rhythm has been restored, the pacemaker should revert quickly to the normal atrial tracking mode. There are several potential causes of symptoms that relate to mode switching. First, an irregular paced ventricular intervals at the onset of an atrial arrhythmia before conversion to a non-tracking mode. Second, failure of the device to convert to a non-tracking mode because of intermittent undersensing of the atrial electrocardiogram may result in continued irregular or rapid ventricular pacing [20]. Third, inappropriate reversion to a tracking mode despite persistence of an atrial arrhythmia may also be caused by intermittent undersensing of the atrial electrocardiogram. Fourth, an overly sensitive mode-switching algorithm may result in loss of atrio-ventricular (AV) synchrony in sinus rhythm [2,11,17,19]. Finally, intrinsic AV conduction of an atrial arrhythmia may produce symptoms that are unrelated to the pacemaker [21]. Although all manufacturers of dual chamber pacemakers offer devices that provide mechanisms for managing the occurrence of atrial arrhythmias, the mode-switching algorithms that are available differ significantly in their sensitivity, specificity, and speed of mode conversion at the onset and termination of atrial arrhythmias. There are potential compromises between sensitivity and specificity with these algorithms, the balance of which may determine the frequency of arrhythmia-related symptoms. Atrial-based pacing is associated with a risk of developing atrial fibrillation lower than ventricular-based pacing for patients with sinus node dysfunction [22-25].

Patients with left bundle branch block and left axis deviation show a specific left ventricular asynchrony pattern: Implications for left ventricular lead placement during CRT implantation

BACKGROUND Left bundle branch block (LBBB) and left axis deviation (LAD) patients may have poor response to resynchronization therapy (CRT). We sought to assess if LBBB and LAD patients show a specific pattern of mechanical asynchrony. METHODS CRT candidates with non-ischemic cardiomyopathy and LBBB were categorized as having normal QRS axis (within -30° and +90°) or LAD (within -30° and -90°). Patients underwent tissue Doppler imaging (TDI) to measure time interval between onset of QRS complex and peak systolic velocity in ejection period (Q-peak) at basal segments of septal, inferior, lateral and anterior walls, as expression of local timing of mechanical activation. RESULTS Thirty patients (mean age 70.6years; 19 males) were included. Mean left ventricular ejection fraction was 0.28±0.06. Mean QRS duration was 172.5±13.9ms. Fifteen patients showed LBBB with LAD (QRS duration 173±14; EF 0.27±0.06). The other 15 patients had LBBB with a normal QRS axis (QRS duration 172±14; EF 0.29±0.05). Among patients with LAD, Q-peak interval was significantly longer at the anterior wall in comparison to each other walls (septal 201±46ms, inferior 242±58ms, lateral 267±45ms, anterior 302±50ms; p<0.0001). Conversely, in patients without LAD Q-peak interval was longer at lateral wall, when compared to each other (septal 228±65ms, inferior 250±64ms, lateral 328±98ms, anterior 291±86ms; p<0.0001). CONCLUSIONS Patients with heart failure, presenting LBBB and LAD, show a specific pattern of ventricular asynchrony, with latest activation at anterior wall. This finding could affect target vessel selection during CRT procedures in these patients.

An unusual case of arrhythmic palpitations in a volleyball player

A case of a 31 years old woman volleyball player highly symptomatic for arrhythmic palpitations is reported. The woman was disqualified from competitive sport and referred to our centre for atrial fibrillation (AF) ablation. During symptoms surface ECG had documented irregular supraventricular tachyarrhythmia interpreted as AF. Electrophysiological study could reveal double-His conduction as the true arrhythmia mechanism and the patient was successfully treated with nodal slow pathway ablation. Patient was totally asymptomatic at a 12 months follow up and he was readmitted to competitive sport. The case further underlines the concept that young subjects with suspected lone AF should undergo to a careful clinical evaluation in order to reconstruct the exact electrophysiological mechanism to plan a safe and effective therapy.

Safety and feasibility of atrial fibrillation ablation using Amigo® system versus manual approach: A pilot study

Background The Amigo® Remote Catheter System is a relatively new robotic system for catheter navigation. This study compared feasibility and safety using Amigo (RCM) versus manual catheter manipulation (MCM) to treat paroxysmal atrial fibrillation (PAF). Contact force (CF) and force-time integral (FTI) values obtained during pulmonary vein isolation (PVI) ablation were compared. Methods Forty patients were randomly selected for either RCM (20) or MCM (20). All were studied with the Thermocool® SmartTouch® force-sensing catheter (STc). Contact Force (CF), Force Time Integral (FTI) and procedure-related data, were measured/stored in the CARTO®3. Results All cases achieved complete PVI without major complications. Mean CF was significantly higher in the RCM group (13.3 ± 7.7 g in RCM vs. 12.04 ± 7.42 g in MCM p < 0.001), as was overall mean FTI (425.6 gs ± 199.6 gs with RCM and 407.5 gs ± 288.0 gs in MCM (p = 0.007) and was more likely to fall into the optimal FTI range (400-1000) using RCM (66.1% versus 49.1%, p < 0.001). FTI was significantly more likely to fall within the optimal range in each PV, as was CF within its optimal range in the right PVs, but trended higher in the left PVs. Freedom from atrial tachyarrhythmia was 90.0% for the RCM and 70.0% for the MCM group (p = 0,12) at 540 days follow-up. Conclusions This pilot study suggests that use of the Amigo RCM system, with STc catheter, seems to be safe and effective for PVI ablation in paroxysmal AF patients. A not statistically significant favorable trend was observed for RCM in term of AF-free survival.

Carotid sinus hypersensitivity syncope: is there a possiblealternative approach to pacemaker implantation in youngpatients?

Carotid sinus hypersensitivity (CSH) is frequently found in about one third of elderly patients with syncope and trauma, but it may also be a common finding in younger patients. Pacemaker implantation is recommended in patients with recurrent syncope once CSH has been recognised. Cardioneuroablation (CNA) has been reported as an effective treatment in cardioinhibitory syncope [1, 2]. A few reports are currently available in neurally mediated syncope and functional atrioventricular block [3, 4], but no previous experiences are available in carotid sinus hypersensitivity syncope. A 42-year-old female patient, with normal heart and no relevant medical history, was referred to our centre for recurrent CSH syncope. As the patient refused PM implantation, autonomic nervous system modulation through CNA was proposed. At the basic EP study normal atrioventricular conduction parameters (AH 68 ms, HV 50 ms) were documented; during CSM a sinus arrest of up to 5.4 s occurred. Electroanatomical mapping of the right atrium with identification of phrenic nerve course was performed (Figure 1 A). Anterior right CNA (35 W, 43°C, 2 min and 40 s of RF delivery) at the level of the septal aspect of the superior vena cava determined a shortening of the basal sinus cycle length (from 975 ms to 730 ms). Vagal stimulation by manual CSM did not cause any pause. After 20 min, a new CSM showed suprahisian atrioventricular block with normal HV (RR max of 2608 ms) (Figure 1 B). Inferior right CNA (35 W, 43°C, 1 min and 30 s of RF delivery) posterior to the coronary sinus ostium was performed, in a region previously reported to be involved in AV conduction neuromodulation (located between the inferior vena cava and the right/left atrium) [1–3]. At CSM after RF and after 30 min of observation no longer pathological pauses were documented (RR max 1.4 s). Shorter AV conduction intervals were observed (AH 48 ms, HV 50 ms). At 6-month follow-up the patient is still asymptomatic for syncope and dizziness. Ablation lesions were performed using an anatomical approach (without AF-Nest mapping); no pharmacological test was performed to confirm the denervation; only right atrial CNA was performed in order to minimize the risk of complications; a longer follow-up period is needed to confirm ablation results. The CNA restricted to the right atrium, if properly standardized, could be an attractive and safer alternative to PM implantation to treat CSH syncope, especially in younger patients who are more vulnerable to mediumand long-term complications related to device implantation.

In-Hospital Cardiac Arrest: Are We Well Enough Equipped and Prepared to Face It?

Sudden death is a real concern for nowadays medicine, especially as it can occur in people with no signs of disease at all. It can be the first symptom of an underlying problem. It may be defined as an unexpected event occurring with no warning signs, within less than an hour, in a person with a known but stable cardiac problem, or in a person with an unknown but pre-existing problem. Often a cardiac problem is the substrate for cardiac arrest (Table 1), but many other diseases can be the underlying cause of sudden death, which in 75% of cases is due to ventricular fibrillation or tachycardia, in 20% to brad- yarrhythmia, and in 5% atrioventricular dissociation [1, 2]. In Italy it strikes more than 60 000 people per year, with a 10% overall mortality, 20% of which is made up of people with no previous signs of disease at all [1].

Electromagnetic Interference in Biventricular and/or ICD Paced Patients

The potential risk of interaction between electronic systems and implantable cardioverter-defibrillators (ICDs) is well documented and frequently reported on by the scientific press [1-4]. When an electronic medical device is exposed to radiofrequency (RF) signals by electronic systems, the RF energy (Table 1) is absorbed by the electronic circuitry and other components, and functioning may be altered. In a technologically advanced world, radiation from electronic system is omnipresent at home, work, and other everyday environments (Table 2). It is spread by different modes such as electrical leads or cables, electrostatic induction, electromagnetic radiation, intentional transmitters (radar, radio, TV and satellite transmissions, mobile telecommunication systems, scientific equipments), and unintentional transmitters (induction heaters, electrical equipment, car ignition systems, diathermy generators), and constitutes the main source of disturbances to active medical devices equipped with an electrical circuit prone to detect them.