Precordial electrode placement for optimal ECG monitoring: implications for ambulatory monitor devices and event recorders.

INTRODUCTION: Detection of QRS complexes, P-waves and atrial fibrillation f-waves in electrocardiographic (ECG) signals is critical for the correct diagnosis of arrhythmias. We aimed to find the best bipolar lead (BL) with the highest signal amplitude and shortest inter-electrode spacing. METHODS: ECG signals (120 seconds) were recorded in 36 patients with 16 precordial electrodes placed in a standardized pattern. An average signal was analysed for each of 120 possible BLs obtained by calculating the difference between pairs of unipolar leads. Peak-to-peak amplitudes of QRS waves (50ms around R-peak) and P waves (270-70ms before R-peak) were calculated. For patients with atrial fibrillation, power of the fibrillatory (f) wave was used instead. Maximum values at each distance were considered and differentiation analysis was performed based on incremental changes (amplitude to distance). RESULTS: There was a significant correlation between distance and QRS-amplitude (r=0.78, p<0.001), P-wave amplitude (r=0.60, p<0.01) and f-wave power (r=0.79, p<0.001). The range of values was: QRS-amplitude 0.7-2.33mV, P-wave amplitude 0.07-0.18mV, and f-wave power 0.55-2.12mV(2)/s. The maximum value for the shortest distance was on a heart-aligned axis over the left ventricle for the QRS complex (1.9mV at 8.7cm) and over the atria for the P-wave (0.98mV) and f-waves (1.45mV(2)/s at 8cm, respectively). CONCLUSION: There is a strong positive correlation between electrode distance and ECG signal-amplitude. Distance of 8cm on a heart-aligned axis and over the relevant heart-chamber provides the highest signal amplitude for the shortest distance. These findings are essential for the design and use of ambulatory monitoring devices.

A novel cryoballoon technique for mapping and isolating pulmonary veins: a feasibility and efficacy study.

INTRODUCTION: The study was designed to evaluate the feasibility and efficacy of a simplified cryoballoon technique in which a microcircular catheter was introduced into the central lumen of a cryoballoon catheter for the purpose of recording pulmonary vein (PV) potentials during ablation procedures and without interchanging catheters. METHODS AND RESULTS: A total of 23 consecutive patients with paroxysmal atrial fibrillation (AF) were enrolled. A single transseptal puncture was made and a cryoballoon catheter was inserted into the left atrium. A 6-pole mapping catheter with a 0.035-inch shaft diameter was introduced into the PV through the central lumen of the cryoballoon catheter. In addition to the function as a recording device, the mapping catheter was also used as a "guide-wire" during the procedure. A total of 84 PVs (84/92, 91.3%) were completely isolated using this novel cryoballoon technique. In 43 of the 84 veins (51.2%), isolation was observed in real time during the cryoablation; in the remaining 41 veins (48.8%), isolation was confirmed immediately post ablation attempt with the mapping catheter. Procedure time was 152.7 +/- 54.9 minutes, and fluoroscopy time was 33.2 +/- 17.3 minutes. At follow-up (7.4 months, range 2-18 months), 17 (73.9%) patients were free from AF. There was 1 occurrence of phrenic nerve palsy during ablation of a right superior PV, which fully resolved after 1 month. CONCLUSION: The use of a cryoballoon catheter equipped with a 6-pole micromapping catheter inserted through its central lumen for the purpose of mapping and ablation during PV isolation procedures is both feasible and effective.

Reconstructing and registering three-dimensional rotational angiogram of left atrium during ablation of atrial fibrillation.

BACKGROUND: Three-dimensional (3D) image of left atrium (LA) can greatly facilitate ablation of atrial fibrillation (AF). Reconstructing method using computed tomography (CT) has certain limitations. The 3D image of LA can be intraprocedurally reconstructed by a rotational angiography technique. METHODS: Forty-six patients undergoing AF ablation were included in this study. Preprocedural CT imaging and intraprocedural reconstructing 3D rotational angiogram (3DRA) of LA were performed in all the patients. Rapid ventricular pacing (RVP, 300 ms) was used to inhibit the drainage of atrium. During RVP, contrast medium was injected into the LA, and rotational angiography was performed. The 3DRA was reconstructed and was registered with the live fluoroscopy. The 3DRA was evaluated in comparison to the CT image. In the navigation of the registered 3DRA, the ablation of AF was performed. RESULTS: Forty-four 3DRAs (95.7%) were successfully reconstructed and registered with the live fluoroscopy. The LA anatomy was delineated in the 3DRA in comparison to a CT image. AF ablation was successfully performed in the 44 patients in the navigation of the registered 3DRA. There were good correlations in the PV ostial diameter and the LA volume as assessed by 3DRA in comparison to a CT image (r>=0.87). The radiation exposure in rotational angiography was substantially less than that in CT scanning (2.7+/-0.9 mSv vs. 24.9+/-3.1 mSv, P<0.001). CONCLUSIONS: It is feasible to reconstruct and register the 3DRA with live fluoroscopy using the RVP method during the ablation of AF.

Magnetic resonance imaging analysis of right ventricular pressure-volume loops: in vivo validation and clinical application in patients with pulmonary hypertension.

BACKGROUND: The aims of this study were to validate MRI-derived right ventricular (RV) pressure-volume loops for assessment of RV myocardial contractility and then to apply this technique in patients with chronic RV pressure overload for assessment of myocardial contractility, ventricular pump function, and VA coupling. METHODS AND RESULTS: Flow-directed catheters were guided under MR fluoroscopy (1.5 T) into the RV for invasive pressure measurements. Simultaneously, ventricular volumes and myocardial mass were assessed from cine MRI. From sampled data, RV pressure-volume loops were constructed, and maximal ventricular elastance indexed to myocardial mass (E(max_i)) was derived by use of a single-beat estimation method. This MRI method was first validated in vivo (6 swine), with conductance techniques used as reference. Bland-Altman test showed good agreement between methods (E(max_i)=5.1+/-0.5 versus 5.8+/-0.7 mm Hg x mL(-1) x 100 g(-1), respectively; P=0.08). Subsequently, the MRI method was applied in 12 subjects: 6 control subjects and 6 patients with chronic RV pressure overload from pulmonary hypertension. In these patients, indexes of RV pump function (cardiac index), E(max_i), and VA coupling (E(max)/E(a)) were assessed. In patients with pulmonary hypertension, RV pump function was decreased (cardiac index, 2.2+/-0.5 versus 2.9+/-0.4 L x min(-1) x m(-2); P<0.01), myocardial contractility was enhanced (E(max_I), 9.2+/-1.1 versus 5.0+/-0.9 mm Hg x mL(-1) x 100 g(-1); P<0.01), and VA coupling was inefficient (E(max)/E(a), 1.1+/-0.3 versus 1.9+/-0.4; P<0.01) compared with control subjects. CONCLUSIONS: RV myocardial contractility can be determined from MRI-derived pressure-volume loops. Chronic RV pressure overload was associated with reduced RV pump function despite enhanced RV myocardial contractility. The proposed MRI approach is a promising tool to assess RV contractility in the clinical setting.

Combined use of three-dimensional rotational angiogram of left atrium and circular multi-electrode ablation catheter for pulmonary vein isolation.

BACKGROUND: A novel circular pulmonary vein ablation catheter (PVAC) has been introduced for pulmonary vein isolation (PVI). Accurate delineation of left atrium-pulmonary vein (LA-PV) anatomy is important for this technique. The aim of this study was to test whether the 3-dimensional rotational angiography (3D RTA) of the left atrium can facilitate PVI using PVAC technique. METHODS: Twenty patients with paroxysmal atrial fibrillation (AF) were enrolled in this study. The 3D RTA was reconstructed and registered with live fluoroscopy in all the patients. AF ablation was performed with a PVAC catheter in the navigation of registered 3D RTA. RESULTS: The 3DRTA image was successfully reconstructed and registered with live fluoroscopy in all patients (100%). The LA-PV anatomy was delineated clearly in all patients. Navigation of the PVAC inside the registered 3D RTA, ensured accurate placement within the atrium to perform ablation, and the PVAC was correctly placed inside the PV ostium to verify the PVI. All the PVs were isolated. Total procedural time was (87.5 ± 12.1) minutes, and fluoroscopy time was (20.1 ± 6.3) minutes. Follow-up after (7.1 ± 1.5) months showed freedom from AF in 70% (14/20) patients. No PV stenosis was observed. CONCLUSIONS: Intraprocedure reconstructed and registered 3D RTA can clearly delineate the LA-PV anatomy in real-time. The results demonstrate the feasibility and reliability of combining use of 3DRA and PVAC in AF ablation procedures.

Rapid ventricular pacing to optimize rotational angiography in atrial fibrillation ablation.

BACKGROUND: Conventional pulmonary vein (PV) angiography cannot precisely delineate the left atrium (LA)-PV anatomy, which is essential for the ablation of atrial fibrillation (AF). The aim of the study was to test the feasibility of a novel method of rotational angiography for the AF ablation. METHODS AND RESULTS: Forty-one patients were enrolled in this study. CT scanning was performed in all patients before the procedure. Rotational angiography (rotating from right anterior oblique 55 degrees to left anterior oblique 55 degrees ) was performed before AF ablation. Rapid ventricular pacing (RVP, 300 ms) was carried out to reduce cardiac output while contrast medium was injected into the LA via a pigtail catheter. RVP was successfully performed in 36 (87.8%) patients. The ostia of all PVs and the LA appendage were visible in all these 36 cases. There was a good correlation in the PV ostial diameters as assessed by rotational angiography via RVP as compared to CT imaging (r (2) > 0.85). CONCLUSIONS: Rotational angiography by RVP is able to delineate the LA-PV anatomy. There is a good correlation in the PV ostial diameters as assessed by rotational angiography via RVP and CT imaging. Rotational angiography by RVP is feasible during AF ablation.

Human experience with transvenous biventricular defibrillation using an electrode in a left ventricular vein.

This study investigated the safety and feasibility of transvenous biventricular defibrillation in ICD patients. Some patients may have high DFTs due to weak shock field intensity on the LV. Animal studies showed a LV shocking electrode dramatically lowered DFTs. This approach might benefit heart failure patients already receiving a LV lead or conventional ICD patients with high DFTs. A modified guidewire was used as a temporary left venous access defibrillation electrode (LVA lead). In 24 patients receiving an ICD, the LVA lead was advanced through a guide catheter in the coronary sinus (CS) and into a randomized LV vein (anterior or posterior) using a venogram for guidance. Paired DFT testing compared a standard right ventricular defibrillation system to a biventricular defibrillation system. There were no complications or adverse events. As randomized, LVA lead insertion success was 87% and 71% for anterior and posterior veins, respectively, and 100% after crossover. Total insertion process time included venogram time (32.5 +/- 26.9 minutes, range 5-115, mode 15 minutes) and LVA lead insertion time (15 +/- 14 minutes, range 1-51, mode 7 minutes). An apical LVA lead position was achieved in 11 (45%) of 24 patients and 7 (64 %) of these 11 displayed a DFT reduction; however, mean DFTs were not statistically different. Transvenous biventricular defibrillation is feasible and was safe under the conditions tested. Additional clinical studies are justified to determine if optimized LV lead designs, lead placement, and shock configurations can yield the same large DFT reductions as observed in animals.