Don’t Get Your Eyes Tricked

AUTHORS

Luis Arabia, MD

Chief Electrophysiology and Arrhythmias Instituto Oulton, Cordoba, Argentina

*Corresponding author: Luis Arabia, MD, Chief Electrophysiology and Arrhythmias Instituto Oulton, Cordoba, Argentina

Received date: 15 May 2020; Accepted date: 05 June 2020; Published date: 10 June 2020

Citation: Arabia L (2020) Don’t Get Your Eyes Tricked. J Heart Cardiovasc Imag 1(1): https://doi.org/10.38207/jhci20001

Copyright: © 2020 Arabia L. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.



ARTICLE INFORMATION

Received date: 15 May 2020; Accepted date: 05 June 2020; Published date: 10 June 2020

Citation: Arabia L (2020) Don’t Get Your Eyes Tricked. J Heart Cardiovasc Imag 1(1): https://doi.org/10.38207/jhci20001

Copyright: © 2020 Arabia L. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.



ABSTRACT

Atrial fibrillation (AF) is the most common sustained arrhythmia, with a global incidence of 2 % in the general population, increasing with age, and growing every year. It has been estimated that more than 2.5 million people in America and 4.5 million in the European Union have any form of AF (paroxysmal, persistent, or permanent). Many years ago, it has been considered a benign rhythm disorder, but now, we know that it is not true, associated with increased mortality, and really linked with loss of quality of life, due to thromboembolic events, systemic or neurologic [1-5].


Keywords: Atrial fibrillation, aerosolization, Cardiogenic embolism


Atrial fibrillation (AF) is the most common sustained arrhythmia, with a global incidence of 2 % in the general population, increasing with age, and growing every year. It has been estimated that more than 2.5 million people in America and 4.5 million in the European Union have any form of AF (paroxysmal, persistent, or permanent). Many years ago, it has been considered a benign rhythm disorder, but now, we know that it is not true, associated with increased mortality, and really linked with loss of quality of life, due to thromboembolic events, systemic or neurologic [1-5].

Cardiogenic embolism has been estimated to be the source in 20-40 % of all cases of stroke, it is very important in cryptogenic events, and AF represents about 60% of all of them [6]. Sometimes it’s difficult to link these neurologic episodes with paroxysmal AF, implantable loop recorders (ILR) helped in that way, but left atrium (LA) and left atrium appendage (LAA) function are really important here, not only the presence of the arrhythmia.

Stroke associated with AF is a big concern because usually causes hight disability, with elevated recurrence and death in the first 30 days. Moreover, AF has been also related to cognitive impairment, but a direct relationship hasn’t been always proved.

On the other hand, LA procedures have increased a lot over time, AF ablation with pulmonary vein isolation (PVI), LAA closure with devices, percutaneous mitral valve treatment, and more... But to access the LA it has to be free of clots. In non-valvular AF about 90 % of them come from the LAA, so it’s mandatory to be sure that LA/LAA is clean before transeptal puncture [5].

The LAA is a very complex structure, located anterior and superior in the LA, with a different embryologic origin (it comes from the primordial left atrium and the rest of the LA cavity derives from an outgrowth of the pulmonary veins [7]. In more than two thirds, it has multiples lobes in differents planes, being not easy to see completely in a two-dimension image method, with blind spots where clots can hide. Its anatomic relationships are very important to plan an interventional procedure, for example in PVI or LAA closure.

Transesophageal echo (TEE), was and still is, the gold standard to evaluate the LAA and rule out thrombus. It is a semi-invasive study, with information in real-time not only about morphology but function using doppler to quantify the emptied flow velocity, but it has to be performed for trained operators, has a mild discomfort, sometimes with anesthetic support, it has a hight aerosolization of the environment, and in very few cases with the risk of esophagus perforation. Sometimes depending on the echo window and number and lobes orientation, the LAA can’t be seen completely, and thrombus can be missed. In this point doppler evaluation is crucial, normal flow velocity usually is over 50 cm/s, with less than 40 cm/s spontaneous echo contrast (smoke) is not surprising to be seen, and less than 20 cm/s clots are frequent, and the risk of stroke is really hight, with or without AF. Sometimes LAA dysfunction exists in patients in sinus rhythm, after an  LAA isolation in the context of AF ablation or not, in this last situation possibly LA myopathy is the cause, with or without left ventricle dysfunction [8].

The multidetector computed tomography scan (MDCT) has risen as a great method to evaluate LA, LAA, PV, coaxially from the interatrial septum to the LAA ostium to guide transeptal punctures in the LAA occlusion setting, LAA dimensión in the devices landing zones, proximity to the mitral valve and ridge of the left upper PV, aorta, coronary arteries, pulmonary artery, and more, in an integrated view in different planes, with 3D reconstruction. This is a very reliable method to do before the procedure and for the follow-up, but there are two main concerns, iodine contrast with the risk of nephrotoxicity and radiation exposure. Some years ago the most used was 64 multislice CT scan in the retrospective acquisition, with high doses of radiation, close to 15 mSv, now with new generations of MDCT, using prospective acquisition and volumetric reconstruction with low dose radiation protocols it fell to 1.5 to 2 mSv [9,10].

But what about LAA thrombus. As we said TEE is still the gold standard, but occasionally it can’t see it completely, dense smoke associated with severe LAA dysfunction can confuse and see more (thrombus than doesn't exist) or less (not see lobes in a different plane). Here MDCT is really very useful, but we have to keep in, mind that LAA filling defects on CT may represent thrombus or incomplete contrast mixing with blood, especially in those patients with severe LA/LAA dysfunction [8,11,12].

Some strategies were described to increase specificity, sensibility, positive, and negative predictor value (PPV and NPV respectively). The most common techniques are delayed acquisition to give more time to the contrast to fill all the LAA. Here, of course, there is not only one protocol, with a single or double bolus and different timing. Another option is to put the patient in a prone position and perform the images and compares it with supine ones. Hounsfield unit (HU) evaluation of the filling defect is very useful, and in a few labs, its comparison with the ascendant aorta is used. In a practical way, hight risk filling defects have to be considered when it is homogeneous, with less than 100 HU, well-defined borders, and persistent in a delayed sequence and/or prone position. Considering this the sensitivity and NPV are 100% in many series [12-14].

The best practice is to integrate information in difficult cases from both methods, TEE and MDCT, but sometimes the access to TEE can be limited, this situation is not uncommon in this historical moment that we are living due to the pandemic COVID-19 situation, with really less TEE being performed for the aerosolization risk. So it may be a reasonable alternative to use MDCT.

Conflict of Interest

I want to acknowledge to Ariel Arabia for his support and creativity.

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Received date: 15 May 2020; Accepted date: 05 June 2020; Published date: 10 June 2020

Citation: Arabia L (2020) Don’t Get Your Eyes Tricked. J Heart Cardiovasc Imag 1(1): https://doi.org/10.38207/jhci20001

Copyright: © 2020 Arabia L. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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