High Yield Review of the Uses of Cardiac CT in Heart Failure

Citation: Spencer S Kitchin, Venkat Sanjay Manubolu and Mathew J Budoff (2022) High Yield Review of the Uses of Cardiac CT in Heart Failure 21st Century Cardiol, Volume 2 (5): 125

Abstract

Heart failure (HF) is a widespread disease. These patients need evaluation into the etiology of the heart failure, and require personalized cardiovascular care tailored to their heart disease (coronary artery disease, structural, electrophysiology). One of the ways these patients can be managed is with cardiac computed tomography (CT), which is a versatile tool that can be used to rule out ischemic etiology of heart failure, assess hemodynamic consequences of coronary artery disease, evaluate the myocardium, and assist in various procedural interventions. Cardiac CT has seen huge advances in technology allowing for novel uses over the last decade. Recently, the authors wrote a detailed narrative review on the uses of cardiac CT in heart failure to review these uses [1]. This commentary will address high yield topics on how cardiac CT can be integrated into the clinical care of patients with HF in accordance with major society guidelines, as well as future uses of this modality.

Keywords:

Cardiac computed tomography; Heart failure; Valvular disease; Coronary artery disease

Introduction

Heart failure (HF) is a widespread disease with significant morbidity and mortality attached to it. These patients require investigation into the etiology and complications of heart failure so that they can be treated with customized care targeted towards any combination of coronary artery disease (CAD), structural disease, and arrythmias. One of the ways these patients can be managed is with cardiac computed tomography (CT), which is a versatile tool by which physicians can glean significant information about their patients. Cardiac CT is a rapidly evolving field, and providers may feel overwhelmed and underprepared to use this modality. Recently, the authors wrote a detailed narrative review on the uses of cardiac CT in heart failure to remedy this [1]. This commentary will address high yield topics on how cardiac CT can be integrated into the clinical care of patients with HF in accordance with major society guidelines, as well as future uses of this modality.

Discussion

The core use of cardiac CT to date is in ruling out CAD. Coronary artery calcium (CAC) scans, which are rapid, safe, and non-contrast CT scans that can be used in predicting cardiovascular risk. The 2018 ACC/AHA Cholesterol Guideline states that coronary artery calcium (CAC) testing may be considered in adults with intermediate risk [2]. Regarding patients with HF, a prospective, blinded study showed that CAC scans have sensitivity of 99% and overall accuracy of 92% in patients with LVEF <40% [3]. This is one way to rule out an ischemic etiology of HF in patients with low-intermediate risk of CAD.

While CAC scans are useful, computed coronary tomographic angiography (CCTA) is even more robust. CCTA is another form of CT scan that?s fast (occurring in a single breath hold), extremely accurate, and safe (Figures 1-3). One large multi-centered prospective trial showed that CCTA has sensitivity, specificity, negative predictive value, and positive predictive value of 92-100%, 83-93%, 88-100%, 81-92%, respectively, for detection of coronary lesions with >50% luminal stenosis [4]. With regard to safety, the radiation does is relatively low at 3.5msV and CCTA has been proven to be safer than invasive coronary angiography [4,5]. Lastly, CCTA is widely applicable and retains accuracy (albeit with decreased sensitivity) in patients with atrial fibrillation, acute decompensated heart failure, prior history of CAD with stents, and end stage renal disease [6-9].

Figure 1: Three-dimensional rendering of CCTA.

Figure 2: CCTA image of right coronary artery.

Figure 3: CCTA image of left anterior descending artery.

 

The 2021 AHA/ACC guidelines on chest pain list CCTA is a class 1A recommendation for patients with acute chest pain and no known CAD, after a negative or inconclusive workup for acute coronary syndrome. It?s also considered a key element in the initial workup of heart failure by the ESC guidelines [10,11]. Although both along with nuclear myocardial perfusion imaging (nMPI) and CCTA have their respective strengths, it should be noted that in the evidence to date, CCTA has outperformed nMPI in terms of accuracy for detecting CAD [12], and CCTA is a Class 1a, while nMPI has been reduced to a Class Ib recommendation.

A second myocardial technique called perfusion scanning can also be used to evaluate CAD that effects blood flow to the myocardium (Figure 4) [13]. One paper considered whether cardiac CT might be considered a ?one stop shop? for CAD imaging [14]. This model suggests that combined protocols be used to identify coronary artery luminal stenosis, deficits in myocardial perfusion, and myocardial scar at the same time. Currently, there may be limitations to this approach related to high contrast load and radiation exposure.

Figure 4: Three-dimensional rendering of myocardial CT perfusion scanning.

 

Another use of cardiac CT has been to image myocardial fibrosis using a technique called myocardial CT delayed enhancement (CTDE). One example is the imaging of myocardial scar related to ischemic heart disease. Magnetic resonance imaging (MRI) with late gadolinium enhancement (LGE) has been the gold standard in this field, and myocardial CTDE has comparable performance to cardiac MRI [15]. Because fibrosis represents the end stage manifestation of multiple disease pathways (such as aortic stenosis, cardiac sarcoidosis, cardiac amyloidosis, etc), myocardial CTDE has a variety of possible uses, many of which are still evolving and are not yet included in major society guidelines. In general, MRI supersedes myocardial CTDE in this arena, and so myocardial CTDE can be thought of as an alternative to MRI where cost, access, or expertise prevent MRI acquisition.

Next, cardiac CT has numerous applications in structural and electrical cardiac disease. The basis for these applications is the excellent spatial and temporal resolution of cardiac CT. It is considered vital to any TAVR program, as it is the gold standard for aortic annular sizing (Figure 5) [16]. Moreover, cardiac CT can be used peri-procedurally in transcatheter mitral valve replacement device selection, left atrial appendage occlusion planning, and cardiac resynchronization therapy lead placement [17-19].

Figure 5: Cardiac CT image of calcified aortic valve.

 

Future uses of cardiac CT include hardware improvements to for more detailed anatomic images, improved perfusion imaging, and upgraded assessment of myocardial viability. It is also possible that it will be more routinely used peri-procedurally. Specifically, cardiac CT is a rapid imaging modality to assist radiofrequency catheter ablation planning in lieu of MRI in cases where patients do not have MRI compatible devices or are too sick to spend much time in the MRI scanner [20]. Another example was recently published, whereby three-dimensional images from CT can be synchronized with two dimensional fluoroscopic images in the catheterization laboratory to guide interventionalists intra-procedurally [21].

Current limitations of cardiac CT include radiation exposure, which is decreasing with time. Furthermore, the use of iodine contrast in certain protocols can make providers hesitant to utilize this modality in patients with kidney disease. Lastly, more work needs to be done on standardizing cut-offs and protocols for the more recent applications of this modality.

Conclusion

In summary, cardiac CT is a viable, robust, and versatile tool to assist in the complicated care of patients with HF.