Alexis Harrison

Atrial Fibrillation Ablation Outcome Is Predicted by Left Atrial Remodeling on MRI

Background—Although catheter ablation therapy for atrial fibrillation (AF) is becoming more common, results vary widely, and patient selection criteria remain poorly defined. We hypothesized that late gadolinium enhancement MRI (LGE-MRI) can identify left atrial (LA) wall structural remodeling (SRM) and stratify patients who are likely or not to benefit from ablation therapy. Methods and Results—LGE-MRI was performed on 426 consecutive patients with AF without contraindications to MRI before undergoing their first ablation procedure and on 21 non-AF control subjects. Patients were categorized by SRM stage (I–IV) based on the percentage of LA wall enhancement for correlation with procedure outcomes. Histological validation of SRM was performed comparing LGE-MRI with surgical biopsy. A total of 386 patients (91%) with adequate LGE-MRI scans were included in the study. After ablation, 123 patients (31.9%) experienced recurrent atrial arrhythmias during the 1-year follow-up. Recurrent arrhythmias (failed ablations) occurred at higher SRM stages with 28 of 133 (21.0%) in stage I, 40 of 140 (29.3%) in stage II, 24 of 71 (33.8%) in stage III, and 30 of 42 (71.4%) in stage IV. In multivariate analysis, ablation outcome was best predicted by advanced SRM stage (hazard ratio, 4.89; P<0.0001) and diabetes mellitus (hazard ratio, 1.64; P=0.036), whereas increased LA volume and persistent AF were not significant predictors. LA wall enhancement was significantly greater in patients with AF versus non-AF controls (16.6±11.2% versus 3.1±1.9%; P<0.0001). Histological evidence of remodeling from surgical biopsy specimens correlated with SRM on LGE-MRI. Conclusions—Atrial SRM is identified on LGE-MRI, and extensive LGE (≥30% LA wall enhancement) predicts poor response to catheter ablation therapy for AF.

Highly accelerated real-time cardiac cine MRI using k-t SPARSE-SENSE.

For patients with impaired breath‐hold capacity and/or arrhythmias, real‐time cine MRI may be more clinically useful than breath‐hold cine MRI. However, commercially available real‐time cine MRI methods using parallel imaging typically yield relatively poor spatio‐temporal resolution due to their low image acquisition speed. We sought to achieve relatively high spatial resolution (∼2.5 × 2.5 mm2) and temporal resolution (∼40 ms), to produce high‐quality real‐time cine MR images that could be applied clinically for wall motion assessment and measurement of left ventricular function. In this work, we present an eightfold accelerated real‐time cardiac cine MRI pulse sequence using a combination of compressed sensing and parallel imaging (k‐t SPARSE‐SENSE). Compared with reference, breath‐hold cine MRI, our eightfold accelerated real‐time cine MRI produced significantly worse qualitative grades (1–5 scale), but its image quality and temporal fidelity scores were above 3.0 (adequate) and artifacts and noise scores were below 3.0 (moderate), suggesting that acceptable diagnostic image quality can be achieved. Additionally, both eightfold accelerated real‐time cine and breath‐hold cine MRI yielded comparable left ventricular function measurements, with coefficient of variation <10% for left ventricular volumes. Our proposed eightfold accelerated real‐time cine MRI with k–t SPARSE‐SENSE is a promising modality for rapid imaging of myocardial function. J. Magn. Reson. Imaging 2013.

The right ventricle under pressure: evaluating the adaptive and maladaptive changes in the right ventricle in pulmonary arterial hypertension using echocardiography (2013 Grover Conference series)

The importance of the right ventricle (RV) in pulmonary arterial hypertension (PAH) has been gaining increased recognition. This has included a reconceptualization of the RV as part of an RV–pulmonary circulation interrelated unit and the observation that RV function is a major determinant of prognosis in PAH. Noninvasive imaging of RV size and function is critical to the longitudinal management of patients with PAH, and continued understanding of the pathophysiology of pulmonary vascular disease relies on the response of the RV to pulmonary vascular remodeling. Echocardiography, in particular the newer echocardiographic measurements and techniques, allows easy, readily accessible means to assess and follow RV size and function.

Self-gated cardiac magnetic resonance perfusion imaging compared with X-ray angiography: a pilot study

Background Cardiovascular Magnetic Resonance (CMR) stress perfusion is an effective noninvasive diagnostic clinical tool when combined with late gadolinium enhancement imaging (LGE) for evaluation of ischemia, infarct, and cardiac prognosis. Good ECG-gating is essential to the commonly used perfusion sequences, but ECG-gating is problematic in obese patients, high field magnetic fields, and patients with arrhythmias. We describe a rapid radial-based self-gated (SG) perfusion acquisition for detection of perfusion defects and compare this to LGE and X-ray coronary angiography (XCA) in the detection of infarction or ischemia. Methods

Detection of late radiation damage on left atrial fibrosis using cardiac late gadolinium enhancement magnetic resonance imaging

Purpose This is a proof-of-principle study investigating the feasibility of using late gadolinium enhancement magnetic resonance imaging (LGE-MRI) to detect left atrium (LA) radiation damage. Methods and materials LGE-MRI data were acquired for 7 patients with previous external beam radiation therapy (EBRT) histories. The enhancement in LA scar was delineated and fused to the computed tomography images used in dose calculation for radiation therapy. Dosimetric and normal tissue complication probability analyses were performed to investigate the relationship between LA scar enhancement and radiation doses. Results The average LA scar volume for the subjects was 2.5 cm3 (range, 1.2-4.1 cm3; median, 2.6 cm3). The overall average of the mean dose to the LA scar was 25.9 Gy (range, 5.8-49.2 Gy). Linear relationships were found between the amount of radiation dose (mean dose) (R2 = 0.8514, P = .03) to the LA scar-enhanced volume. The ratio of the cardiac tissue change (LA scar/LA wall) also demonstrated a linear relationship with the level of radiation received by the cardiac tissue (R2 = 0.9787, P < .01). Last, the normal tissue complication probability analysis suggested a dose response function to the LA scar enhancement. Conclusions With LGE-MRI and 3-dimensional dose mapping on the treatment planning system, it is possible to define subclinical cardiac damage and distinguish intrinsic cardiac tissue change from radiation induced cardiac tissue damage. Imaging myocardial injury secondary to EBRT using MRI may be a useful modality to follow cardiac toxicity from EBRT and help identify individuals who are more susceptible to EBRT damage. LGE-MRI may provide essential information to identify early screening strategy for affected cancer survivors after EBRT treatment.

A NOVEL UNGATED CARDIAC MAGNETIC RESONANCE PERFUSION PROTOCOL FOR THE DETECTION OF SIGNIFICANT SINGLE AND MULTIVESSEL CORONARY DISEASE IN PATIENTS WITH ATRIAL FIBRILLATION

Cardiovascular magnetic resonance (CMR) myocardial perfusion detection of significant obstructive coronary disease (CAD) is well established. With concerns of ECG-gating in arrhythmia and true-rest after regadenoson, we investigated the diagnostic accuracy and discrimination of a rapid rest-first

Initial results of a new very rapid rest/regadenoson stress myocardial perfusion protocol in patients with atrial fibrillation

Background Cardiovascular magnetic resonance (CMR) myocardial perfusion is a well established method for detection of significant obstructive coronary artery disease (CAD). In patients with arrhythmias, standard methods using ECGgating can result in poor image quality. Additionally, with typical stress/rest protocols, a true rest state may not be achieved after administration of regadenoson. However, rest-first may present issues with peri-infarct ischemia and so here we give little time for late enhancement by keeping rest and stress perfusion scans close in time. Given these issues, the two-fold aim of this study is to evaluate the accuracy of a rapid rest-first protocol using an ungated myocardial image pulse sequence.

Left atrial late gadolinium enhancement following external beam radiation for lymphoma: a potential model for exploring radiation-related heart disease

We are able to detect subclinical post-irradiation changes to the heart with left atrial late gadolinium enhanced magnetic resonance imaging (LGE-MRI).

REAL-TIME MRI EVALUATION OF ACUTE LEFT ATRIAL INJURY PROGRESSION DURING RADIOFREQUENCY ABLATION OF ATRIAL FIBRILLATION

Methods: 5 animal models were utilized. A single RF lesion was placed at the interatrial septum. A T2w DIR-FSE sequence was performed immediately after lesion placement and repeated 10 minutes later. Sequence parameters were: TE = 83 ms, TR = 2RR, ETL = 21, fat suppression using SPAIR, in-plane resolution of 1.25 x 1.25 mm, slice thickness of 4 mm, 20 slices, GRAPPA with R = 2 and 42 reference lines. Typical scan time was 6 minutes.

A direct comparison of adenosine and regadenoson myocardial perfusion reserves measured by MRI

Methods 8 subjects (5 female, 3 male) without ischemia were imaged on a 3 T Siemens Trio system. Imaging was done first at rest, and then during adenosine infusion (140 ug/ kg/min) and 34 ± 4 minutes later with regadenoson injection (0.4 mg/5 ml). A 5 cc/sec injection of Gd-BOPTA (MultihanceTM) was used, with doses of 0.02, 0.03 and 0.03 mmol/kg, respectively. The contrast was injected ~3 minutes after the start of the adenosine infusion, and ~90 seconds after the regadenoson injection. A saturation recovery radial turboFLASH sequence was used with 72 rays acquired after each saturation pulse. Scan parameters were TR = 2.6 msec, TE = 1.14 msec, flip = 14, slice thickness = 8 mm. Reconstruction was performed by iteratively minimizing a cost function as in [1] with total variation constraints in both space and time dimensions. Processing was performed in a manner similar to [2] to convert the arterial input functions into gadolinium concentration to remove the effects of saturation. Images were registered and segmented to give time curves from 6 tissue regions per slice. The curves were fit to a two compartment model and Ktrans used as an index of perfusion.