A Review of New Techniques in the EP Lab

In this article, authors Ankush Verma, MS and Dr. Sanjeev Saksena discuss their research in intracardiac echocardiography for intraoperative assessment of CRT, as well as their techniques on biatrial mapping for atrial fibrillation using three-dimensional non-contact mapping. Use of ICE-Guided Optimization of Cardiac Resynchronization Therapy to Improve Outcomes We have been investigating a new application of intracardiac echocardiography (ICE) for intraoperative assessment of cardiac resynchronization therapy (CRT). In a recent study,1 we performed intraoperative ICE imaging to monitor left ventricular function, aortic valvular flow, and patient safety during implantation of a biventricular pacemaker defibrillator system. We also used ICE when managing CRT system lead placement in order to evaluate the impact of pacing modes and optimize device programming. Standard practice guidelines were used to select patients for CRT. In our pilot investigation, patients had been hospitalized for heart failure in the past 12 months and had either QRS duration of greater than 120 msec or evidence of ventricular dyssynchrony on echocardiography. Patients gave informed consent for the CRT implant and the procedure. Intracardiac imaging was performed prior to CRT system implantation and throughout the procedure until completion of device programming. The phased array ultrasound imaging system (St. Jude Medical, St. Paul, MN) was used, and images were visualized on the ViewMate® platform (St. Jude Medical). The ICE technique involved placement of the ICE catheter in the right ventricle through a curved deflectable sheath. This allowed for prolonged monitoring of left ventricular function during the entire procedure with B-mode and M-mode recordings. ICE was used to assess baseline left ventricular function and ejection fraction at the beginning of the procedure, and reassessed during lead placement at different venous sites and with different right and left ventricular pacing modes. It also allowed lead placement away from infarcted or non-contractile regions. The left ventricular pacing lead was placed in the selected left ventricular vein, and pacing was then assessed with ICE imaging during the procedure. After a final lead position was selected, the implant was completed and the device was programmed. AV interval optimization as well as VV interval optimization was performed using the ICE catheter to achieve maximal benefit. Based on the relative changes in left ventricular ejection fraction, individualized settings of AV and VV interval programming were achieved. In the initial study, 23 patients were enrolled. After ICE-guided optimization, there was an acute improvement in mean left ventricular ejection fraction, which was significant from a mean of 24% at baseline to 41% after optimization. During mean follow-up of 11 months, New York Heart Association (NYHA) class improved from a mean of 3.2 to 1.6, and mean LV ejection fraction improved from 19% to 34%. One-year patient survival was 83%. These findings were extremely encouraging, and suggest that the non-responsiveness to CRT can be greatly reduced by the use of optimization of LV lead position and device programming at implant. Biatrial Mapping Combined with 3-D Non-Contact Mapping: Enhanced Identification of Tachyarrhythmias Maintaining Atrial Fibrillation A clinical technique for simultaneous biatrial mapping of spontaneous atrial fibrillation (AF) was developed in our laboratory using multi electrode catheters and a non-contact EnSite® balloon array (St. Jude Medical) for high-resolution mapping. We recently updated our results of biatrial mapping of spontaneous AF in the Journal of Atrial Fibrillation.2 In this report, we included the results of mapping with this approach. Patients represented a wide spectrum of AF. Seventy-six consecutive patients with a mean age of 63 years, of whom 68% were male, were reported. The majority of the patients (79%) were in NYHA Class I and II. Sixty-six patients demonstrated spontaneous atrial premature beats (APBs), with 90 sites in the right atrium and 41 locations in the left atrium, with similar regional distributions regardless of structural heart disease. Forty-two patients (64%) had more than two disparate regional origins and biatrial regional foci demonstrated equal frequency in both paroxysmal and persistent AF. This study highlights the importance of having biatrial mapping techniques to identify triggering atrial premature beats in both atria or the septum. Fifty-six patients (74%) had 93 spontaneous episodes of AF during the mapping procedure. Sixty-one percent of the patients had AF episodes with the right-sided or septal origin, and 39% had left-sided origin of the atrial tachyarrhythmia (AT) during these episodes. Most patients had AF episodes originating in both atria. The regional distribution of AF origin was more extensive in persistent AF as compared to paroxysmal AF. Overall, focal or macroreentrant left ATs initiating or maintaining AF were seen in 18%, with macroreentrant left atrial flutter in 25%. Isthmus-dependent right atrial counterclockwise flutter was the most common arrhythmia seen in both populations, whereas non-isthmus-dependent right atrial flutter was most commonly seen in persistent AF (47%). The activation patterns on non-contact mapping were helpful in localizing focal origins such as from the pulmonary vein (showing single centrifugal propagation patterns) and in right ATs (macroreentrant tachycardias). These kinds of phenomena can only be seen on a beat-to-beat basis in high-resolution non-contact mapping of both atria. Standard mapping with a limited number of catheter electrodes fails to identify these patterns. In conclusion, the major findings from these experiences are: 1) There is a broad distribution of triggering beats in the right atrium, septum, left atrium and pulmonary veins in the drug-refractory AF population; 2) Both paroxysmal and persistent AF patients demonstrate equal frequency of biatrial regional foci, commonly with multiple regional sources of APBs in an individual patient; 3) At the onset of sustained atrial fibrillation, an organized tachyarrhythmia occurs, which may be focal or reentrant and may often localize to adjoining atrial regions. These ATs initiate or maintain AF episodes. These findings provide important new understandings of human atrial fibrillation.