Left Atrial Flow Velocity Research Articles

Left atrial thrombus in patients with atrial fibrillation and under oral anticoagulant therapy; 3-D transesophageal echocardiographic study.

Ischemic stroke is the major complication of atrial fibrillation (AF) and only proven preventive therapy is oral anticoagulant therapy (OAC). Previous studies reported the presence of thrombus in the left atrium (LA) or left atrial appendage (LAA) despite anticoagulant therapy. We aim to investigate the predictors of LA/LAA thrombus in patients under OAC therapy and long-term clinical impact of thrombus. We prospectively enrolled consecutive patients with permanent AF under OAC therapy. Patients baseline characteristics were recorded. Transesophageal echocardiographic study performed after complete transthoracic echocardiographic study. 3-D evaluation of LAA was made using 3-D zoom mode and thrombus was defined when echo reflecting, mobile mass detected. Patients clinical outcomes were decided according to hospital records or via phone calls. Among 184 patients, 28 LAT were detected. Mean CHA2DS2-VASc score was significantly higher in patients with LAT in comparison to patients without LAT. CHA2DS2-VASc score (p: 0.001), left atrial volume (p: 0.001), left atrial flow velocity (p: 0.006) and left ventricular ejection fraction (p: 0.014) were independently associated with LAT. Among the parameters in CHA2DS2-VASc score, the previous history of stroke and age were independently related to LAT. After 12months of follow-up, patients with LAT had more ischemic stroke than patients without LAT (7.1% vs 4.4%, p: 0.001 respectively). Although oral anticoagulation is the default treatment strategy for prevention of LAT and thromboembolism in patients with non-valvular AF, LAT still can be detected especially in patients with a high CHA2DS2-VASc score. Furthermore, the presence of LAT is significantly associated with future ischemic stroke.

Left atrial flow velocity distribution and flow coherence using four‐dimensional FLOW MRI: A pilot study investigating the impact of age and Pre‐ and Postintervention atrial fibrillation on atrial hemodynamics

To use four-dimensional (4D) flow MRI to characterize and quantify 3D blood flow in the left atria (LA) of patients with a history of atrial fibrillation (AF). The 4D flow MRI was acquired in 19 volunteers (n = 9<30 years, n = 10>50 years) and 10 patients with AF (62 ± 9.6 years; n = 4 in persistent AF, n = 6 postintervention). The LA in each dataset was segmented, and intra-atrial blood flow velocity was quantified. Flow coherence was measured as the consistency of the net blood flow vector. Quantification of atrial flow revealed significant differences in atrial hemodynamics between age groups. Postintervention AF patients had a mean blood flow of 0.22 ± 0.04 m/s, which was not significantly different than age-matched volunteers (0.21 ± 0.03 m/s). Patients with persistent AF had a mean blood flow of 0.13 ± 0.01 m/s, lower than AF patients in sinus rhythm (0.22 ± 0.04 m/s, P = 0.005), or age-matched volunteers (0.21 ± 0.03 m/s, P < 0.001). Flow coherence was significantly impaired in patients in AF. Flow-sensitive MRI shows that patients with a history of AF had global hemodynamics in the LA similar to those of age-matched volunteers. Additional studies with larger cohorts of AF patients and correlation with outcome are needed to further investigate the potential of atrial 4D flow MRI to flow patterns indicative of stroke risk in AF.

Quantification of left atrial flow velocity distribution in atrial fibrillation using 4D flow MRI

Background Atrial fibrillation (AF) is an arrhythmia characterized by irregular electrical activity in the left atrium (LA). Thromboembolism is the most serious complication of AF, usually manifesting as stroke or systemic embolism (1). This is thought to be linked to the increased risk of thrombus formation in the LA due to a decrease in blood velocity (stasis) or flow abnormalities. A better appreciation of the underlying mechanisms and risk factors for thrombus formation in the individual patient are needed to improve risk stratification and therapy planning. Using 4D-flow MRI, time resolved blood velocity measurements can be made in patients with AF. The aim of this study was to compare LA velocity distributions in different groups of AF patients. We hypothesize that persistent AF results in more deranged LA flow patterns with reduced velocities which may be related to an increased risk of thrombus formation and thus stroke. Methods MRI data were acquired from 31 AF patients (mean age 63+/-10.5) from two groups (n=21 post-treatment, in sinus rhythm, n=10 in persistent AF). Each subject underwent gated 4D-Flow MRI on 1.5T and 3T MR systems (Siemens, Erlangen, Germany). After noise filtering, Maxwell, and eddy current correction, time resolved pathlines were emitted from planes placed manually over the pulmonary veins at the junction with the LA (Fig 1). The LA was segmented and the distribution of velocities was quantified by histogram analysis. Mean velocities were calculated for each subject group. In addition number of voxels with velocities greater than 0.2m/s was calculated. The selection of the velocity threshold was based on previous TEE results which found that systolic LA velocities less than 0.2m/s constitute a risk factor for stroke (2). Results Qualitative observation of the blood flow patterns in patients showed very different patterns between those subjects imaged in sinus rhythm and those in persistent AF. Fig 1 displays clear differences in blood flow at end systole (A,D), early diastole (B,E), and mid diastole (C,F) for a post-intervention AF patient in sinus rhythm and in persistent AF. The quantitative results from all subjects are summarized in fig 2. Patients with persistent AF had a mean blood flow of 0.14±0.03m/s, lower than AF patients in sinus rhythm (0.19±0.04m/s, p=0.006). 14% of the velocity values for patients in AF were greater than 0.2m/s, lower than patients in sinus (35%, p=0.004).

Therapeutic Strategies After Examination by Transesophageal Echocardiography in 503 Patients With Ischemic Stroke

Transesophageal echocardiography (TEE) is the gold standard in detecting high-risk (ie, aortic thrombi) and potential sources (ie, patent foramen ovale [PFO]) of cerebral embolism. We sought to evaluate the additional information and therapeutic impact provided by TEE in stroke patients and to characterize patients in whom TEE is indispensable. We included 503 consecutive patients (mean age 62.2 years) with acute brain ischemia. Each patient received TEE and the following routine diagnostics: ultrasound of brain supplying arteries, ECG or Holter-ECG, transthoracic echocardiography, and brain imaging (computed tomography or MRI). Stroke etiology was classified according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. High-risk sources in TEE were: aortic thrombi or plaques > or =4 mm, thrombi in left atrial cavity/left atrial appendage, spontaneous echo contrast, and left atrial flow velocity <30 cm/s. Potential sources in TEE were PFO, atrial septal aneurysm, and aortic plaques <4 mm. Stroke etiology was determined by routine diagnostics in 276 of 503 patients (54.9%). Of the remaining 227 patients (undetermined etiology), 212 (93.4%) were candidates for oral anticoagulation (OA). TEE revealed a high-risk source, with indication for OA in 17 of them (8.0%). A potential source leading to OA was found in an additional 48 patients (22.6%). The remaining 147 patients (69.3%) were treated by platelet inhibitors or statins. TEE strongly influenced secondary prevention and led to OA in one third of our patients with stroke of undetermined etiology. TEE is indispensable in all patients being candidates for OA when routine diagnostics cannot clarify stroke etiology.

Usefulness of transesophageal echocardiography using a combined probe when converting atrial fibrillation to sinus rhythm

We studied the feasibility and efficacy of transesophageal echocardiography (TEE) combined with transesophageal cardioversion (TEC). Secondary aims were to study left atrial flow velocities before and 1 and 5 minutes after TEC, biochemical markers of myocardial damage, and patient tolerability. TEC after a short period of anticoagulation and exclusion of a clot with TEE was safe. TEC was well tolerated and efficacious. The use of a combined probe for TEE and TEC therefore can save time and be more effective. A custom-made probe for combined TEE plus TEC was used. TEC was performed with a step-up protocol (20 J to between 30 and 50 J) and with biphasic shocks. Presence of spontaneous echo contrast was scored. Cumulative energy needed to achieve sinus rhythm was calculated. Discomfort was scored on a scale of 0 to 10. Twenty-six patients underwent combined TEE/TEC. Sinus rhythm was achieved in 24 of 26 patients (92%) with a mean cumulative energy of 42.3 J. Sixteen of 26 patients were cardioverted with a 20-J shock, and 6 of these patients had early recurrence of atrial fibrillation. All biochemical markers were unaffected, and TEE/TEC was well tolerated. Left atrial appendage velocity decreased significantly after TEC. Thus, the use of a TEE/TEC probe offers effective cardioversion with low energy levels, is well tolerated, and hemodynamics during and immediately after cardioversion can be monitored. Early cardioversion after exclusion of a clot with this combined probe is time saving and cost effective.

Hemodynamic and hemorheologic determinants of left atrial spontaneous echo contrast and thrombus formation in patients with idiopathic dilated cardiomyopathy

The purpose of the present study was to evaluate the specific role of hemorheologic and hemodynamic parameters for spontaneous echo contrast and thrombus formation in vivo. We therefore investigated the association between the presence of left atrial spontaneous echo contrast and thrombus formation by transesophageal echocardiography and multiple clinical, hemodynamic, and hemorheologic parameters in 70 patients with idiopathic dilated cardiomyopathy. Transesophageal echocardiography showed left atrial spontaneous echo contrast and left atrial thrombi in 33% and 19% of patients, respectively. Patients with left atrial spontaneous echo contrast had a lower cardiac index (2.1 ± 0.9 versus 2.6 ± 0.9 L/min/m 2; p < 0.02), a lower left atrial (21 ± 8 versus 38 ± 10 cm/sec; p < 0.001) and left atrial appendage flow velocity (17 ± 14 versus 39 ± 13 cm/sec; p < 0.001), a larger left atrial diameter (53 ± 6 versus 46 ± 10 mm; p < 0.002), and more often presented with atrial fibrillation (62% versus 32%; p < 0.02). Plasma fibrinogen concentration (4.0 ± 1.1 versus 3.5 ± 0.7 gm/L; p < 0.02) and plasma viscosity (1.83 ± 0.10 versus 1.76 ± 0.15 mPa · sec; p < 0.05) were higher in patients with spontaneous echo contrast. Multivariate analysis revealed an association between the presence of spontaneous echo contrast and left atrial flow velocity ( p < 0.0001) and plasma viscosity ( p < 0.01). In patients with left atrial (appendage) thrombus or a history of embolism, left atrial appendage flow velocity was lower (15.0 ± 8.2 versus 29.6 ± 14.5 cm/sec; p < 0.005) and spontaneous echo contrast was more frequently observed (52% versus 23%; p < 0.05). Hemorheologic parameters were not significantly different between patients with and without left atrial thrombus. In conclusion, left atrial thrombi and spontaneous echo contrast represent frequent findings in idiopathic dilated cardiomyopathy. They are both primarily related to a low left atrial blood flow velocity. Hemorheologic factors may contribute to spontaneous echo contrast formation in vivo, but are unlikely to play a significant role for thrombus formation.

Contributing factors to formation of left atrial spontaneous echo contrast in mitral valvular disease.

The formation of left atrial spontaneous echo contrast may relate to blood stasis. This study analyzed the factors contributing to the formation of that contrast. Transesophageal echocardiography, transthoracic echocardiography, cardiac catheterization, and left ventricular angiography were performed in 139 patients, divided into five groups. Predominant mitral stenosis with atrial fibrillation was found in 36 patients (group I); normal porcine valve in the mitral valvular area with atrial fibrillation in 31 (group II); predominant mitral stenosis with normal sinus rhythm in 26 (group III); moderate to severe mitral regurgitation with atrial fibrillation in 25 (group IV); atrial fibrillation with normal mitral valve in 21 (group V). The results showed left atrial spontaneous contrast echo was found in only 1 of 139 patients by transthoracic echocardiography and 62 of 139 cases were detected by transesophageal echocardiography. There was a high incidence of left atrial spontaneous echo contrast in cases of mitral obstruction with atrial fibrillation and enlarged left atrium (group I, 88%; group II, 74%), but a lower incidence in cases with normal sinus rhythm (group III, 4%), atrial fibrillation alone (group V, 16%), and increased left atrial flow velocity (group IV, 9.5%). The diameter of the left atrium was significantly different between presence and absence of left atrial spontaneous contrast echo (54.3 +/- 9.2 mm vs. 48.3 +/- 8.6 mm, p less than 0.01). The mean pressure gradient was similar in groups I and III (14.6 +/- 0.6 mHg and 14.4 +/- 2.8 mHg, respectively) but different in group II (10.9 +/- 3.2 mHg, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic and Doppler flow observations in obstructed and nonobstructed hypertrophic cardiomyopathy

Some investigators have suggested that left ventricular (LV) ejection is completed much earlier than normal in patients with hypertrophic cardiomyopathy (HC), whether or not a LV outflow gradient is present, and they have therefore concluded that LV ejection is not impeded in HC, but merely ends early because of early completion of LV emptying. This possibility was examined using pulsed Doppler echocardiography to record ascending aortic flow velocity patterns in 20 patients with HC, 12 with evidence of LV outflow gradient at rest (obstructed HC) and 8 without evidence of a significant resting gradient (nonobstructed HC). Peak aortic flow velocity was similar in patients with nonobstructed HC (92 ± 26 cm/s) and those with obstructed HC (94 ± 26 cm/s) and in 20 normal subjects (92 ± 11 cm/s). However, mean ejection time measured from the aortic flow velocity tracing or aortic echogram was longer in those with obstructed HC (345 ± 30 ms) than in those with nonobstructed HC (296 ± 24 ms, p < 0.02) and in normal subjects (294 ± 19 ms, p < 0.01). Furthermore, a rapid decrease in aortic flow velocity in midsystole was seen in 11 of 12 patients with obstructed HC, but in none of the patients with nonobstructed HC or normal subjects. Doppler left atrial flow velocity recordings, obtained in 11 patients, demonstrated mitral regurgitation in 4 of 5 patients with obstructed HC but in none of 6 patients with nonobstructed HC. The temporal relation between the decrease in Doppler aortic flow velocity, the peaking of Doppler mitral regurgitant flow, and the onset of mitral valve-septal contact in midsystole—as well as observations regarding LV internal dimensional changes—suggest that the early deceleration of aortic blood flow in the patient with obstructed HC is not merely a result of early completion of mechanical systole by a hyperdynamic left ventricle. Rather, midsystolic aortic flow deceleration is at least in part a result of the anterior leaflet of the mitral valve impeding LV outflow and causing ejection of blood by an alternate route into the left atrium.