Left Atrial Volume and Function Assessment by Magnetic Resonance Imaging

Left Atrial Volume and Function Assessment Introduction: In patients with atrial fibrillation undergoing catheter ablation, magnetic resonance imaging (MRI) can determine left atrial (LA) volume and function before and after ablation. The most accurate, but time consuming, method to determine LA volume is the multiple slice method (MSM), which involves manual tracing of LA area on each slice. The area length method (ALM) offers a simplified, but unvalidated, alternative for LA volume assessment by MRI. The aim of this study was to compare LA volume and function assessment by ALM with MSM. Methods and Results: MRI was performed before and after catheter ablation in 40 patients with atrial fibrillation (30 male, mean age 57 years). All patients had sinus rhythm during imaging. In total, 72 MRI scans were available. LA end‐diastolic and end‐systolic volumes (EDV, respectively ESV) were measured by both methods. LA function was determined by calculating LA ejection fraction (EF = (EDV‐ESV)/EDV). Measured by ALM, mean LA EDV and ESV were significantly lower than using MSM (102 mL and 49 mL vs 111 mL and 65 mL, respectively, P < 0.001) with a larger difference in mean ESV than EDV (16 mL vs 9 mL). This resulted in an overestimation of LA EF by ALM with a mean of 11% (54% by ALM and 42% by MSM, P < 0.001). ALM correlated well with MSM for LA EDV and ESV (r = 0.77, respectively 0.85), and showed no significant difference in intraobserver and interobserver variability. Conclusion: ALM significantly underestimates LA volumes and overestimates LA function, but correlates well with the more accurate MSM. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1247‐1250, November 2010)     

Strategies for the Management of SVC Stent Migration into the Right Atrium

Purpose Stent migration into the right atrium is a potentially fatal complication of stenting in the venous system and is most likely to occur during the treatment of superior vena cava obstruction. Endovascular approaches that can salvage this hazardous situation are described and the keys to successful treatment are highlighted. Materials and Methods Four different strategies are reviewed: (1) snaring the stent directly, (2) angioplasty balloon-assisted snaring of the stent, (3) guide wire-assisted snaring of the stent, and (4) superior vena cava-to-inferior vena cava bridging stent. Results These techniques have been employed in the successful management of four cases. No short- or long-term complications as a result of these maneuvers have been identified. Additional treatment of the underlying disease was possible at the same time in each case. Conclusion We conclude that prompt management of right atrial stent migration is essential and can be successfully achieved by a variety of “bale-out” techniques which are within the technical range of most interventional radiologists.     

The anatomical study of left atrium diverticulum by multi-detector row CT

The purpose of this study was to describe radiologic anatomy of the left atrium diverticulum. There were 20 patients with 27 left atrium diverticulums in 120 consecutive patients who underwent CT of coronary angiography. The presence probability of left atrium diverticulum was 16.7%, male of it was 13.0%, female was 17.6%. There was no difference on gender (P > 0.05). There were four patients accompanying with variation of pulmonary vein at one time. The diverticulum might be single or multiple, cystiform or tubiform. It could locate anterior wall or posterior wall or superior wall of left atrium. Left atrium diverticulums which was single, cystiform, and located in anterior wall were common. The cervix width of diverticulum was 4.9 ± 3.2 mm, the body height of them was 5.4 ± 2.0 mm. The ratio of body height to cervix width was from 0.47 to 4.08 (median 1.16). Ten patients of them undertook cardiac ultrasound examination at same time. There were five patients who left atrial diastolic function decreased, four patients who left ventricular systolic function decreased. Three of them both existed left atrial diastolic function decreasing and left ventricular systolic function decreasing, accompanied with mitral or aortic regurgitation. No patient was found that left atrium pressure or left ventricle diastolic pressure was increasing. The left atrium diverticulums of ten patients were probably congenital because their hemodynamical status cannot lead to diverticulum formation. It can be proved by reexamination after therapy or autopsy at last. In conclusion, multi-detector row computed tomography could provide anatomy details of left atrium diverticulum to help to finish heart and chest surgery successfully.     

Improved intra-atrial conduction delay after successful ablation for atrial fibrillation by scar homogenization in right atrium

Atrial fibrosis in the right atrium (RA) presenting as a low-voltage zone might be the mechanism of atrial fibrillation (AF) and intra-atrial conduction delay. The impact of scar homogenization in RA on intra-atrial conduction delay is unknown. We describe a patient with paroxysmal AF and significant intra-atrial conduction delay with repetitive atrial flutter, triggered from the lateral free wall in the RA between the significant low-voltage zone and slow conduction area after pulmonary vein isolation. Linear ablation along the trabeculated lateral free wall in the RA to homogenize the scar was successfully performed, and the intra-atrial conduction delay improved ultimately.     

Separating the left cardiac ventricle from the atrium in short axis MR images using the equation of the atrioventricular plane

Short axis (SA) images obtained from cardiac magnetic resonance imaging are used to advantage in the calculation of important clinical parameters such as the ejection fraction and stroke volume (SV). A prerequisite for these calculations is the separation of the left ventricle and the left atrium. When only using the information seen in the SA images this separation can be a source of error due to the through-plane motion of the basal part of the left ventricle. In this study a method is proposed where the separation of the left ventricle and the atrium is performed by identifying the intersections of the atrioventricular plane in the SA images. The equation of the atrioventricular plane was determined in both systole and diastole using long axis and four chamber image views. Stroke volumes were measured in 20 patients using SA images where the endocardium had been delineated. The SV obtained using the new method was compared with quantitative flow measurements and the conventional technique for calculation of SV from SA images, respectively. The agreement of SV was, according to Bland-Altman analysis, 2.0 ml (95% CI -12.0 to 15.9 ml) in comparison with the flow measurements and 2.2 ml (95% CI -9.2 to 13.6 ml) compared to the conventional method. Inter- and intra-observer variability, when using the new proposed method, was small. This study shows that the identification of the left atrioventricular plane in SA images can be used in the separation of the left atrium and ventricle.     

Endocardial irregularities of the left atrial roof as seen on coronary CT angiography

Objective To describe and characterize morphological characteristics of endocardial irregularities in the roof of the left atrium as seen on coronary CT angiography. Methods We retrospectively evaluated the left atrium in 50 consecutive coronary CT patients with multiplanar reformatting, volume rendering, and virtual endoscopy. Results Twenty-one of the 50 patients had an endocardial irregularity at the roof of the left atrium. The most common finding (n = 14) was a smooth diverticulum, arising near the venoatrial junction of the right superior pulmonary vein. Conclusion Endocardial irregularities of the left atrium can be identified on coronary CT and may be more common than previously considered. The findings probably represent remnants of the cardinal venous system during embryological development. Further work should focus on the true prevalence and potential clinical significance.     

Echocardiographic features of patients with paroxysmal atrial fibrillation

Background. There are several risk factors for the initiation of paroxysmal atrial fibrillation (PAF) and the underlying mechanisms are multifactorial. Our study aims to explore the echocardiographic parameters that can identify in patients with PAF compared to normal subjects. Methods. Eighty consecutive patients who were with PAF detected by 24-h Holter monitoring (HM) were assigned in our study. The control group (n = 80) consisted individuals with no PAF on HM. Indication for HM was palpitations at rest. All patients underwent routine echocardiographic evaluation. Patients with aortic and mitral stenosis, hyperthyroidism, and hypothyroidism were excluded from the study. Comprehensive clinical data were collected. Results. Mean age of the patients with PAF was 63 ± 11 years and of those 42% were male subjects. There was no difference in the prevalence of hypertension in both groups. Mean left ventricular ejection fraction (LVEF) was 57 ± 15% in PAF group and 64 ± 2% in control subjects (p < 0.001). Mean values of left atrial (LA) diameter for PAF and control groups were 3.7 ± 0.6 cm vs. 3.1 ± 0.4 cm (p < 0.001), respectively. Patients with PAF had more severe valve insufficiency, higher values of mean pulmonary artery systolic pressures (PAP) (29 ± 10 mmHg vs. 25 ± 2 mmHg, respectively; p = 0.001) and deteriorated MV inflow velocities (E:A ratio 0.9 ± 0.4 vs. 1.1 ± 0.3, respectively; p = 0.008) when compared to control group. In multivariate logistic regression analysis, LA diameter predicted the development of PAF after adjusted for age and gender. Conclusion. Our results indicate that LA diameter predicts the development of PAF.