Multimodality cardiac imaging, including echocardiography, Cardiac CT (CCT), Cardiac MRI (CMR) and nuclear cardiology modalities; including Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), have propelled our knowledge and understanding of cardiac diseases remarkably over the last few years. Collectively, these modalities stand for a crucial component of today’s integrated and comprehensive cardiac care. The accelerated developments in technology and the fast-growing evidence of positive impact on clinical outcome yield a significantly expanded role of imaging in the average daily cardiology practice.
Historically, cardiac imaging served as the diagnostic function in the cardiovascular service chain. In a classic cardiac imaging service, the studies are performed conventionally, and an interpretation is provided by the cardiac imager. On occasions, the treating physician may pay a visit to the dark room to entertain a brief discussion around the case. This silo-shaped model of cardiac imaging service is hard to sustain as imaging is intersecting with cardiac services particularly catheter-based interventions along the entire patient’s clinical journey. This narrative summarizes the key roles of multimodality cardiac imaging at each stage of the patient’s journey in interventional cardiology (Figure 1).
Optimal Initial Diagnosis:
The principal function of cardiac imaging modalities has been to diagnose underlying cardiac abnormalities with variable capabilities of the different modalities. Echocardiography is the first diagnostic imaging modality that is widely accessible, fast to perform, and provides a wide spectrum of data. Such data, prior to intervention; are helpful in deciding the right therapeutic intervention and providing alternative explanation of the clinical presentation if needed. Advanced technology of cardiac imaging has improved the non-invasive assessment of coronaries significantly and reduced the downstream unnecessary invasive testing. Assessment of the extent of myocardial scar using delayed gadolinium imaging on CMR or metabolic uptake of FDG-PET can be of a great help prior to complex interventions of Complete Total Occlusion (CTO) lesions. Quantification of valvular regurgitation lesions on CMR using flow measurement offers a proper alternative to echocardiographic assessment that aid in more accurate grading of the lesion severity.
Planning for catheter-based interventions, especially structural; using the different imaging modalities is a key factor for the sustained success and continuous evolution of these interventions. Looking back when Trans-catheter Aortic Valve Implantation (TAVI) emerged as the new therapy for severe aortic stenosis in the first half of last decade, up to 50% of patients screened by echocardiography would have received an inappropriately sized transcatheter aortic valve1 . CCT came into the place as the gold standard modality to plan the procedure. Access to and utilization of an alternative modality such as CCT for pre-procedure planning of TAVI results in a significant reduction of paravalvular leak (PVL), aortic rupture, and death2. This enhanced the efficacy and safety of this procedure and pumped its class of indication rapidly. For a considerable portion of TAVI patients with kidney disease, Non-contrast CMR can serve as an alternative modality with overall good correlation with CCT in pre-procedural sizing of aortic annuls.
One challenging intervention is percutaneous closure of para valvular leak. In these scenarios, the complimentary role of the different modalities in procedure planning is obvious. Beyond the initial assessment with echocardiography and 3D transesophageal echocardiography, CCT helps in determining the site, size, and surrounding calcification with high accuracy. CMR offers an incremental value through the ability to provide quantification of the regurgitation by planimetry of the anatomic regurgitant orifice area, and also through phase-contrast velocity mapping analysis.
CCT plays a key role in planning the Trans-catheter Mitral Valve Replacement (TMVR) interventions (mitral valve-in-valve, valve-in-Mitral Annular Calcification (MAC), and valve-in-ring). The hemodynamic assessment by echocardiography is supplemented by CCT which provides highly accurate measurement of the annular size, simulation of the virtual valve and assessment of the structures that contribute to the formation of the new left ventricular outflow tract (Neo-LVOT)3.
In planning for left atrial appendage (LAA) closure, CCT can substitute transesophageal echocardiography, which can be challenging and highly operator dependent; in defining the shape of the appendage, ruling out presence of thrombus and providing the necessary measurements.
Intraprocedural echocardiography is a major factor that plays a role in the success of several structural heart disease interventions such as Trans-catheter Edge-to-Edge Repair (TEER) of mitral and tricuspid valves, percutaneous balloon mitral valvuloplasty and trans-catheter closure of Atrial Septal Defect (ASD), Patent Foramen Ovale (PFO) and LAA.
The role of imager during these procedures is vital at each step from crossing the inter-atrial septum to release of the device in the proper position and achieving the desired result. This requires a certain set of skills that can guide several interventional therapies given the need for adequate knowledge of the device and technical steps, instantaneous nature of image acquisition (including 3D images) and interpretation, non-standard views, and the profound impact on the outcome4.
Fusion imaging technology has the capability to project images from echocardiography and/or CCT onto the fluoroscopy to overcome the limitation of 2D projection of a complex 3D anatomy5. Despite the feasibility of this technology in observational studies, the clinical utility seems to be the greatest in complex interventions such as PVL repair, mitral valve-in-valve and valve-in-ring.
Transthoracic (and occasionally transesophageal) echocardiogram remains the modality of choice for routine follow up of patients post cardiac interventions. However, using other imaging modalities can supply more data to aid in evaluation of the implanted valve or device accurately. CCT is an example of the step-up imaging evaluation of prosthetic valve leaflet motion and delineating the attached masses. Metabolic imaging of masses attached to implanted prosthetic valves with FDG-PET is another advantage of a multimodality imaging service with a noticeable impact on the outcome.
The degree of intersection between cardiac imaging and interventional cardiology is multitude and diverse. However, to move from the current silos and achieve the desired synergy, imaging should be integrated in advanced cardiac intervention programs such as in structural and complex coronary interventions. This integration starts with building institutional imaging capabilities either internally or through collaboration. Although infrastructure of multimodality imaging service and trained personnel appear to be the core of a strongly integrated imaging-intervention program, the make-break component of a successful program is the effective team. A team that works with a clear vision, shared interest, and growth mindset.