Multimodality Imaging for Planning and Follow-up of Transcatheter Aortic Valve Replacement

Multimodality Imaging for Discordant Low-Gradient Aortic Stenosis: Assessing the Valve and the Myocardium

Aortic stenosis (AS) is a disease of the valve and the myocardium. A correct assessment of the valve disease severity is key to define the need for aortic valve replacement (AVR), but a better understanding of the myocardial consequences of the increased afterload is paramount to optimize the timing of the intervention. Transthoracic echocardiography remains the cornerstone of AS assessment, as it is universally available, and it allows a comprehensive structural and hemodynamic evaluation of both the aortic valve and the rest of the heart. However, it may not be sufficient as a significant proportion of patients with severe AS presents with discordant grading (i.e., an AVA ≤ 1 cm² and a mean gradient <40 mmHg) which raises uncertainty about the true severity of AS and the need for AVR. Several imaging modalities (transesophageal or stress echocardiography, computed tomography, cardiovascular magnetic resonance, positron emission tomography) exist that allow a detailed assessment of the stenotic aortic valve and the myocardial remodeling response. This review aims to provide an updated overview of these multimodality imaging techniques and seeks to highlight a practical approach to help clinical decision making in the challenging group of patients with discordant low-gradient AS.

Aortic roots assessment by an automated three-dimensional transesophageal echocardiography: an intra-individual comparison

To evaluate the accuracy, reproducibility, and transcatheter heart valve (THV) sizing efficiency of an automated 3-dimensional transesophageal echocardiographic (3D-TEE) post-processing software in the assessments of aortic roots, intra-individually compared with multidetector computed tomography (MDCT). We prospectively studied 67 patients with normal aortic roots. We measured diameters of aortic annulus (AA), sinus of Valsalva (SOV), and sino-tubular junction (STJ) by full-automated and semi-automated methods using 3D-TEE datasets, then compared them to corresponding transthoracic echocardiography and MDCT values. THV sizes were chosen based on echocardiography and MDCT measurements according to recommended criterion. Taking MDCT planimetered diameters as reference, the full-automated (r: 0.4745-0.8792) and semi-automated (r: 0.6647-0.8805) 3D-TEE measurements were linearly correlated (p < 0.0001). The average differences between semi-automated or full-automated measurements and reference were 0.3 mm or 1.3 mm for AA, - 1.9 mm or - 0.5 mm for SOV, and - 0.1 mm or 1.9 mm for STJ, respectively. The intra-class correlation coefficients of semi-automated method were 0.79-0.96 (intra-observer) and 0.75-0.92 (inter-observer). THV sizing by semi-automated measurements using echocardiographic criteria was larger than that by MDCT measurements using MDCT criteria (p < 0.0001) but equivalent (p > 0.05) if both using MDCT standards. The new automated 3D-TEE software allows modeling and quantifying aortic roots with high reproducibility. Measurements by the semi-automated method closely approximate and well correlate with the corresponding MDCT, thus THV sizing by this modeled 3D-TEE measurements should adopt recommended MDCT criteria but not echocardiographic criteria. The full-automated 3D-TEE segmentations are yet immature. (Semi-automated assessMent of Aortic Roots by Three-dimensional transEsophageal echocaRdiography [SMARTER], NCT02724709).

320-row CT transcatheter aortic valve replacement planning with a single reduced contrast media bolus injection

OBJECTIVE

To reduce the iodine load required for CT Transcatheter Aortic Valve Replacement (TAVR) planning on a 320-row scanner by acquiring the two CT TAVR steps (ECG-gated aortic root CTA and non-gated aorto-ilio-femoral CTA) within a single contrast media bolus injection.

METHODS

50 consecutive patients (82.6±6.9 years; 56% female) were prospectively enrolled and underwent a TAVR planning using a 320-row CT, with ECG-gated aortic root CTA immediately followed by a non-gated aorto-iliac acquisition, all within a single bolus of 40-70mL of Iohexol 350mgI/mL. The Iodine load, image quality, SNR, CNR and radiation dose were compared using a Mann-Whitney test to that of 24 consecutive patients (84.3±4.8 years, 58% female) previously imaged on a 64-row scanner with a conventional two-step protocol.

RESULTS

Iodine load was reduced by 44%. All examinations were of diagnostic quality, with improvement of the aortic root CTA image quality (4.9±0.3 versus 4.6±0.5, p<0.01) and a non-significant decrease of the aorto-iliac CTA image quality (4.7±0.6 versus 4.9±0.3, p = 0.07). SNR and CNR were significantly improved in the aortic root CTA (14.0±5.3 and 10.4±4.5 versus 10.3±4.2 and 6.8±3.3, p<0.01 for both) and non-significantly higher in the aorto-iliac CTA (16.5±8.0 and 14.1±7.9 versus 14.7±5.5 and 12.5±5.0, p = 0.42 and p = 0.66). Total radiation dose was reduced by 32%.

CONCLUSION

320-row CT scanner enables a 44% reduction of iodine load in TAVR planning, while maintaining excellent aorto-ilio-femoral arterial enhancement and lowering radiation dose.

Role of MDCT Imaging in Planning Mitral Valve Intervention

PURPOSE OF REVIEW

Recent advancements in transcatheter valvular interventions have resulted in a growing demand for advanced cardiac imaging to help guide these procedures.

RECENT FINDINGS

Both echocardiography and multi-detector computed tomography have played essential roles in the maturation of transcatheter aortic valve replacement and are now building on these experiences and helping inform the nascent field of transcatheter mitral interventions. Advanced imaging is essential to aid in the diagnosis and determination of the mechanism of mitral regurgitation. In addition, they are integral to annular sizing, determination of the suitability of patient anatomy for specific devices and increasingly important in the determination of the risk of left ventricular outflow tract obstruction and providing appropriate patient-specific fluoroscopic angulation in advance of the procedure.

A new look at the heart-novel imaging techniques

The development and successful implementation of cutting-edge imaging technologies to visualise cardiac anatomy and function is a key component of effective diagnostic efforts in cardiology. Here, we describe a number of recent exciting advances in the field of cardiology spanning from macro- to micro- to nano-scales of observation, including magnetic resonance imaging, computed tomography, optical mapping, photoacoustic imaging, and electron tomography. The methodologies discussed are currently making the transition from scientific research to routine clinical use, albeit at different paces. We discuss the most likely trajectory of this transition into clinical research and standard diagnostics, and highlight the key challenges and opportunities associated with each of the methodologies.