The Electrophysiology of Atrial Fibrillation: From Basic Mechanisms to Catheter Ablation.

The electrophysiology of atrial fibrillation (AF) has always been a deep mystery in understanding this complex arrhythmia. The pathophysiological mechanisms of AF are complex and often remain unclear despite extensive research. Therefore, the implementation of basic science knowledge to clinical practice is challenging. After more than 20 years, pulmonary vein isolation (PVI) remains the cornerstone ablation strategy for maintaining the sinus rhythm (SR). However, there is no doubt that, in many cases, especially in persistent and long-standing persistent AF, PVI is not enough, and eventually, the restoration of SR occurs after additional intervention in the rest of the atrial myocardium. Substrate mapping is a modern challenge as it can reveal focal sources or rotational activities that may be responsible for maintaining AF. Whether these areas are actually the cause of the AF maintenance is unknown. If this really happens, then the targeted ablation may be the solution; otherwise, more rough techniques such as atrial compartmentalization may prove to be more effective. In this article, we attempt a broad review of the known pathophysiological mechanisms of AF, and we present the recent efforts of advanced technology initially to reveal the electrical impulse during AF and then to intervene effectively with ablation.

Incidence, electrophysiological characteristics, and long-term follow-up of perimitral atrial flutter in patients with previously confirmed mitral isthmus block.

INTRODUCTION: After mitral isthmus (ΜΙ) catheter ablation, perimitral atrial flutter (PMF) circuits can be maintained due to the preservation of residual myocardial connections, even if conventional pacing criteria for complete MI block are apparently met (MI pseudo-block). We aimed to study the incidence, the electrophysiological characteristics, and the long-term outcome of these patients. METHODS: Seventy-two consecutive patients (mean age 62.4 ± 10.2, 62.5% male) underwent MI ablation, either as part of an atrial fibrillation (AF) ablation strategy (n = 35), or to treat clinical reentrant atrial tachycardia (AT) (n = 32), or to treat AT that occurred during ablation for AF (n = 5). Ιn all patients, the electrophysiological characteristics of PMF circuits were studied by high-density mapping. RESULTS: Mitral isthmus block was successfully achieved in 69/72 patients (95.6%). Five patients developed PMF after confirming MI block. In these patients, high-density mapping during the PMF showed a breakthrough in MI with extremely low impulse conduction velocity (CV). In contrast, in usual PMF circuits that occurred after AF ablation, the lowest CV of the reentrant circuit was of significantly higher value (0.07 ± 0.02 m/s vs 0.25 ± 0.07 m/s, respectively; P < .001). Patients presented with clinical AT had better prognosis in maintaining sinus rhythm after MI ablation compared with patients presented with AF. CONCLUSION: Perimitral atrial flutter with MI pseudo-block may be present after MI ablation and has specific electrophysiological features characterized by remarkably slow CV in the MI. Thus, even after MI block is achieved, a more detailed mapping in the boundaries of the ablation line or reinduction attempts may be needed to exclude residual conduction.

Ventricular ectopy from the non-coronary cusp: Pathophysiological and anatomical considerations.

Non-coronary cusp (NCC) is a rare site for ventricular arrhythmias because it does not come into direct contact with the ventricular myocardium. Instead, the NCC comes in contact with the membranous septum near the His region. We describe a case of a young man with a ventricular ectopy who was successfully ablated in the NCC. In our case the much greater prematurity in the NCC than in the His region suggests that the arrhythmic site of origin is not in the peri-His area but most likely a myocardial extension adjoining the aortic root.

Radial artery occlusion after transradial coronary catheterization.

The transradial approach (TRA) for coronary angiography and interventions is increasingly utilized around the world. Radial artery occlusion (RAO) is the most common significant complication after transradial catheterization, with incidence varying between 1% and 10%. Although RAO is rarely accompanied by hand ischemia, it is an important complication because it prohibits future transradial access and radial artery utilization as a conduit for coronary artery bypass grafting or arteriovenous fistula formation. In this review, we discuss factors predicting the occurrence of RAO, aspects of accurate and prompt recognition, methods that contribute to its prevention and possible treatment options.

Needle versus cannula over needle for radial artery cannulation during transradial coronary angiography and interventions.

PURPOSE: To evaluate the efficacy of radial artery cannulation with needle versus cannula over needle during transradial coronary angiography and intervention. METHODS: Five hundred patients scheduled to undergo transradial catheterization were randomized between the two methods. Primary endpoint of the study was the combined endpoint of switching to another access site due to inability of successful sheath insertion or switching to another method of cannulation (from needle to cannula over needle and vice versa). RESULTS: The primary end point was met in 12 patients (4.8%) from the needle group and 14 patients (5.6%) from the cannula over needle group (p=0.695). There were no differences in switching of cannulation method [10 (4.0%)% versus 11 (4.4%), p=0.831], switching of access site [6 (2.8%) versus 9 (3.6%), p=0.441), time for artery cannulation [1.20 (0.80-2.20) min versus 1.26 (1.01-2.39) min, p=0.152], total procedure time [15.05 (9.47-29.03) min versus 19.14 (10.13-32.02) min, p=0.112] number of attempts [2 (1-4) versus 2 (1-5), p=0.244] and number of skin punctures [1 (1-2) versus 1 (1-2), p=0.399] before successful radial artery cannulation. There were no differences recorded in the safety endpoints of EASY grade III or more radial hematomas [2 (0.8%) versus 1 (0.4%), p=1.000] or the incidence of radial artery occlusion after the procedure [9 (3.6% versus 16 (6.8%), p=0.358]. CONCLUSION: Radial artery cannulation with needle and cannula over needle seems to be equal in terms of efficacy and safety.

ULnar Artery Transient Compression Facilitating Radial Artery Patent Hemostasis (ULTRA): A Novel Technique to Reduce Radial Artery Occlusion After Transradial Coronary Catheterization.

AIMS: To evaluate the safety and efficacy of a novel technique with simultaneous compression of the ulnar artery in order to reduce the incidence of radial artery occlusion (RAO) after transradial cardiac catheterizations. METHODS AND RESULTS: Ipsilateral ulnar artery transient compression for 1 hour facilitating radial artery patent hemostasis (ULTRA) was performed in all patients treated transradially in October 2015 and was compared with patients treated with conventional patent hemostasis in September 2015. The primary endpoint of the study was to evaluate the incidence of RAO within 1 hour after removing the closure device, confirmed by the absence of palpation and the consecutive absence of flow signal with Doppler examination. A total of 119 patients were treated with the ULTRA method and 121 patients with conventional patent hemostasis. None of the patients treated with ULTRA had RAO compared with 6 patients (5%) of those treated with conventional patent hemostasis (P=.01). No hematomas EASY class ≥3, nerve injury, or ischemic pain complications were recorded in either group. CONCLUSION: The ULTRA technique may reduce the incidence of RAO in patients treated with the radial approach compared with conventional patent hemostasis.