Sok-Sithikun Bun

Value of in vivo T2 measurement for myocardial fibrosis assessment in diabetic mice at 11.75 T.

Objective:The aim of the study was to assess the value of in vivo T2 measurements to noninvasively quantify myocardial fibrosis in diabetic mice at 11.75 T. Diabetic cardiomyopathy is characterized by extracellular matrix alteration and microcirculation impairment. These conditions might provide electrical heterogeneity, which is a substrate for arrhythmogenesis. T1 mapping has been proposed to quantify diffuse myocardial fibrosis in cardiac diseases but has several limitations. T2 measurement may represent an alternative for fibrosis quantification at high magnetic field. Materials and Methods:A magnetic resonance imaging protocol including in vivo T2 measurements at 11.75 T was performed in 9 male C57BL/6J mice after 8 weeks of streptozotocin-induced diabetes and in 9 control mice. Programmed ventricular stimulation was performed in both groups. T2 measurements were compared with histologic quantification of fibrosis using picrosirius red staining. Results:Myocardial T2 was significantly lower in diabetic mice (13.8 ± 2.8 ms) than in controls (18.9 ± 2.3 ms, P < 0.001). There was a good correlation between T2 and fibrosis area obtained by histopathology (R2 = 0.947, P < 0.001). During programmed ventricular stimulation, 3 nonsustained ventricular tachycardias were induced in diabetic mice versus none in the control group. Conclusions:The in vivo T2 relaxation time strongly correlated with myocardial fibrosis area assessed with histologic staining in diabetic mice.

Atrial flutter: more than just one of a kind

Since its first description about one century ago, our understanding of atrial flutter (AFL) circuits has considerably evolved. One AFL circuit can have variable electrocardiographic (ECG) manifestations depending on the presence of pre-existing atrial lesions, or impaired atrial substrate. Conversely, different (right sided or even left sided) atrial circuits including different mechanisms (macroreentrant, microreentrant, or focal) can present with a very similar surface ECG manifestation. The development of efficient high-resolution electroanatomical mapping systems has improved our knowledge about AFL mechanisms, as well as facilitated their curative treatment with radiofrequency catheter ablation. This article will review ECG features for typical and atypical flutters, and emphasize the limitations for circuit location from the surface ECG.

Quantification of myocardial blood flow and flow reserve in rats using arterial spin labeling MRI: comparison with a fluorescent microsphere technique

To quantify noninvasively myocardial blood flow (MBF) and MBF reserve in isoflurane‐anesthetized rats using the Look‐Locker flow‐alternating inversion recovery gradient‐echo arterial spin labeling technique (LLFAIRGE‐ASL), and to compare the results with the fluorescent microsphere (FM) technique. Male Wistar rats (weight = 200–240 g, n = 21) were anesthetized with 2.0% isoflurane. Hemodynamic parameters were recorded. In seven rats, MBF was assessed on a Bruker Biospec 4.7T MR system using an ECG‐ and respiration‐gated LLFAIRGE‐ASL (pixel size = 234 × 468µm2, TE = 1.52ms) at rest and during adenosine infusion (140 µg/kg/min). A mixture of 200 000 FM was injected into a second group of rats at rest and during adenosine infusion (n = 7 each), under similar physiologic conditions. Hearts and skeletal muscle samples were processed for fluorescence spectroscopy. Two‐tailed unpaired, paired Students t‐test and ANOVAwere used to compare groups. MBF measured with LLFAIRGE‐ASL was 5.2 ± 1.0 mL/g/min at rest and 13.3 ± 3.0 mL/g/min during adenosine infusion. Results obtained with fluorescent microspheres yielded 5.9 ± 2.3 mL/g/min (nonsignificant vs. LLFAIRGE‐ASL, p = 0.9) at rest and 13.1 ± 2.1 mL/g/min (nonsignificant vs. LLFAIRGE‐ASL, p = 0.4) during adenosine infusion. Myocardial blood flow reserve measured using LLFAIRGE‐ASL and FM were not significantly different (2.5 ± 0.6 vs. 2.4 ± 0.9, respectively; p = 0.8). Hemodynamic parameters during the experiments were not different between the groups. The myocardial blood flow reserve determined under isoflurane anesthesia was 2.5 ± 0.6, which was not different from the value obtained with FM. LLFAIRGE‐ASL provided MBF maps with high spatial resolution in rats under isoflurane anesthesia. LLFAIRGE‐ASL is a noninvasive measure to assess myocardial blood flow reserve and provides an interesting tool for cardiovascular research. Copyright

Ultrasound-guided venous puncture in electrophysiological procedures: a safe method, rapidly learned.

We sought to determine the feasibility and learning curve associated with systematic use of real‐time ultrasound‐guided venous puncture (UGVP) in patients undergoing electrophysiological (EP) procedures.

Selection of Critical Isthmus in Scar-Related Atrial Tachycardia Using a New Automated Ultrahigh Resolution Mapping System

Background— Accurate activation mapping of reentrant scar-related atrial tachycardias (AT) allows efficient radiofrequency ablation by targeting the critical isthmus (CI). We aimed to assess the electrophysiological properties of CI channels during mapping with the IntellaMap Orion basket and the Rhythmia system. Methods and Results— We prospectively studied 33 AT (post– atrial fibrillation ablation or surgical mitral valve repair). The noise of bipolar electrogram (EGM) was systematically measured at 10 prespecified sites, as well as on a standard catheter and on the surface ECG. Bipolar EGM of CI regions were analyzed for amplitude, duration, and conduction velocity. The isthmus region to be targeted was chosen based solely on propagation. For each AT, 25 684±14 276 EGMs were automatically annotated. Noise of the Orion EGM was 0.011±0.004 mV, lower than that of a standard catheter (0.016±0.019) and surface ECG (0.02±0.01; P<0.05). For reentrant AT, within the CI, bipolar EGM amplitude (0.08±0.11 mV) and conduction velocity (0.27±0.19 m/s) were lower than those orthodromically before (0.62±0.93 mV; 1±0.49 m/s) and after (0.80±1.59 mV; 1±0.73 m/s) the isthmus (P<0.001 for all). In 97% of AT, ablation at the CI resulted in AT termination. No complications occurred. Conclusions— This new automated ultrahigh resolution mapping system produces low noise and allows accurate diagnosis of AT circuits. CI on reentrant scar-related AT showed much lower EGM amplitude with a significantly slower conduction velocity than the surrounding parts of the circuit. Ablation of the areas of slow conduction resulted in a high acute success.

Electroanatomic characteristics of the mitral isthmus associated with successful mitral isthmus ablation

AIMS The success of mitral isthmus (MI) ablation has been related to CT scan defined MI anatomy. We sought to correlate electroanatomical MI characteristics with MI ablation success in patients with perimitral flutter (PMF). METHODS AND RESULTS In 53 consecutive patients (46 males, 61 ± 10 years) with PMF, MI was ablated with endocardial ± coronary sinus (CS) linear radiofrequency (RF) ablation lesion. Acute (termination of PMF during ablation) and long-term procedural success were studied. Mitral isthmus characteristics (thickness--minimal endocardial to CS distance, length, maximal MI bipolar voltage), as well as MI ablation line length and width, RF duration, and delivered energy were analysed. In 43 of the 53 patients (81%), acute success was observed. This was more frequently achieved in patients with thinner MI (2.4 ± 3.1 vs. 7 ± 3.2 mm; P = 0.0009). Mitral isthmus thickness predicted ablation failure with a ROC area of 0.84. The best threshold to predict MI ablation failure was 8.3 mm with a sensitivity of 67% and a specificity of 97%. Left atrial size was of greater importance in failed cases (2D echo surface: 24.1 ± 2.5 vs. 32.5 ± 6.9 cm2, P = 0.005; electroanatomic volume: 124 ± 32 vs. 165 ± 23 mL, P = 0.02). None of the other electroanatomical characteristics were associated with outcome. After a mean follow-up of 28 ± 15 months, 21 patients (39%) had atrial fibrillation (AF) or atypical flutter (PMF recurrence in four). CONCLUSION Smaller MI thickness is associated with acute success in PMF ablation. Mitral isthmus electroanatomical characteristics might be used for decision-making on strategy during persistent AF ablation and for selecting the best location for interrupting PMF.

Defibrillation testing can reveal ‘concealed’ lead fracture

A 68-year-old patient with ischemic cardiomyopathy was admitted for a single-chamber implantable cardioverter-defibrillator (ICD) generator replacement after normal battery depletion. He was implanted in 2001 with a dual-coil …

Radiofrequency catheter ablation of atrial fibrillation: Electrical modification suggesting transmurality is faster achieved with remote magnetic catheter in comparison with contact force use

Remote magnetic navigation (RMN) and contact force (CF) sensing catheters are available technologies for radiofrequency (RF) catheter ablation of atrial fibrillation (AF). Our purpose was to compare time to electrogram (EGM) modification suggesting transmural lesions between RMN and CF‐guided AF ablation.

Remotely controlled steerable sheath improves result and procedural parameters of atrial fibrillation ablation with magnetic navigation.

Aims The magnetic navigation (MN) system may be coupled with a new advancement system that fully controls both the catheter and a robotic deflectable sheath (RSh) or with a fixed-curve sheath and a catheter-only advancement system (CAS). We aimed to compare these approaches for atrial fibrillation (AF) ablation. Methods and results Atrial fibrillation ablation patients (45, 23 paroxysmal and 22 persistent) performed with MN–RSh (RSh group) were compared with a control group (37, 18 paroxysmal and19 persistent) performed with MN–CAS (CAS group). Setup duration was measured from the procedures start to operator transfer to control room. Ablation step duration was defined as the time from the beginning of the first radiofrequency (RF) pulse to the end of the last one and was separately acquired for the left and the right pulmonary vein (PV) pairs. Clinical characteristics, left atrial size, and AF-type distribution were similar between the groups. Setup duration as well as mapping times was also similar. Ablation step duration for the left PVs was similar, but was shorter for the right PVs in RSh group (46 ± 9 vs. 63 ± 12 min, P < 0.0001). Radiofrequency delivery time (34 ± 9 vs. 40 ± 11 min, P = 0.007) and procedure duration (227 ± 36 vs. 254 ± 62 min, P = 0.01) were shorter in RSh group. No complication occurred in RSh group. During follow-up, there were five recurrences (11%) in RSh group and 11 (29%) in CAS group (P = 0.027). Conclusion The use of the RSh for AF ablation with MN is safe and improves outcome. Right PV isolation is faster, RF delivery time and procedure time are reduced.

Ultra-High-Definition Mapping of Atrial Arrhythmias

The advantages of ultra-high-definition (UHD) mapping are presented in the context of different atrial arrhythmias, whether focal or macroreentrant. Not only are these sophisticated systems time-saving, but they also allow accurate identification of the substrate (scar quantification), as well as a more precise characterization of the critical isthmuses or focal sources of the atrial circuits. UHD mapping may become a standard approach for their curative treatment. This new technology allows automatic acquisition and accurate annotation of the electrograms, without the need for manual correction. Owing to better resolution, critical isthmuses and low-voltage regions of interest may now be successfully targeted without the need for entrainment maneuvers. Finally, the system also allows rapid assessment of the completeness of the lesions once delivered. (Circ J 2016; 80: 579-586).