Computed tomography evaluation for transcatheter aortic valve implantation (TAVI): imaging of the aortic root and iliac arteries

For patients with severe aortic stenosis, open-heart surgical valve replacement remains the current clinical standard with documented, excellent long-term outcome. Over the past few years, transcatheter aortic valve implantation (TAVI) has developed into a treatment alternative for high-risk patients with severe aortic stenosis. Because transcatheter valvular procedures are characterized by lack of exposure of the operative field, image guidance is critical. This Pictorial Essay describes the role of 3-dimensional imaging with multidetector row computed tomography for detailed reconstructions of the aortic valve, aortic root, and iliac arteries in the context of TAVI.

Aortic volume as an indicator of disease progression in patients with untreated infrarenal abdominal aneurysm

OBJECTIVE

The maximal diameter of an abdominal aortic aneurysm (AAA) and the change in diameter over time reflect rupture risk and are used for surgical planning. However, evidence has emerged that aneurysm volume may be a better indicator of AAA remodeling. The purpose of this study was to assess the relationship between the volume and maximal diameter of the abdominal aorta in patients with untreated infrarenal AAA.

MATERIALS AND METHODS

This was a retrospective study of 100 patients with infrarenal AAA who were followed for more than 6 months. We examined 2 sets of computed tomography images for each patient, acquired ≥ 6 months apart. The maximal diameter and volume of the infrarenal abdominal aorta were determined by semiautomated segmentation software.

RESULTS

At baseline, mean maximal infrarenal diameter was 5.1 ± 1.0 cm and mean aortic volume was 139 ± 72 mL. There was good correlation between the maximal diameter and aortic volume at baseline (r(2) = 0.55; P<0.001). The mean change in maximal diameter between studies was 0.2 ± 0.3 cm and the mean volume change was 19 ± 19 mL. However, the correlation between diameter change and volume change was modest (r(2) = 0.34; P=0.001). Most patients (n = 64) had no measurable change in maximal diameter between studies (≤ 2 mm), but the change in volume was found to vary widely (-2 to 69 mL).

CONCLUSION

In patients with untreated infrarenal AAA, a change in aortic volume can occur in the absence of a significant change in maximal diameter. Additional work is needed to examine the relationship between change in AAA volume and outcomes in this patient group.

Extent of thoracic aortic atheroma burden and long-term mortality after cardiothoracic surgery: a computed tomography study

OBJECTIVES

We hypothesized that the extent of aortic atheroma of the entire thoracic aorta, determined by pre-operative multidetector-row computed tomographic angiography (MDCTA), is associated with long-term mortality following nonaortic cardiothoracic surgery.

BACKGROUND

In patients evaluated for cardiothoracic surgery, presence of severe aortic atheroma is associated with adverse short- and long-term post-operative outcome. However, the relationship between aortic plaque burden and mortality remains unknown.

METHODS

We reviewed clinical and imaging data from all patients who underwent electrocardiographic-gated contrast-enhanced MDCTA prior to coronary bypass or valvular heart surgery at our institution between 2002 and 2008. MDCTA studies were analyzed for thickness and circumferential extent of aortic atheroma in 5 segments of the thoracic aorta. A semiquantitative total plaque-burden score (TPBS) was calculated by assigning a score of 1 to 3 to plaque thickness and to circumferential plaque extent. When combined, this resulted in a score of 0 to 6 for each of the 5 segments and, hence, an overall score from 0 to 30. The primary end point was all-cause mortality during long-term follow-up.

RESULTS

A total of 862 patients (71% men, 67.8 years) were included and followed over a mean period of 25 ± 16 months. The mean TPBS was 8.6 (SD: ±6.0). The TPBS was a statistically significant predictor of mortality (p < 0.0001) while controlling for baseline demographics, cardiovascular risk factors, and type of surgery including reoperative status. The estimated hazard ratio for TPBS was 1.08 (95% confidence interval: 1.045 to 1.12). Other independent predictors of mortality were glomerular filtration rate (p = 0.015), type of surgery (p = 0.007), and peripheral artery disease (p = 0.03).

CONCLUSIONS

Extent of thoracic aortic atheroma burden is independently associated with increased long-term mortality in patients following cardiothoracic surgery. Although our data do not provide definitive evidence, they suggest a relationship to the systemic atherosclerotic disease process and, therefore, have important implications for secondary prevention in post-operative rehabilitation programs.

Atherosclerosis imaging in progression/regression trials: surrogate marker or direct window into the atherosclerotic disease process?

CAD remains a major global cause of morbidity and mortality. Comprehensive drug development programs of novel pharmacological treatment strategies frequently utilize traditional mortality/morbidity endpoints studies and additional surrogate endpoints trials. This parallel approach allows an assessment of efficacy several years in advance of the availability of data from clinical endpoint trials. Several atherosclerosis imaging markers have been introduced into these drug-development strategies, including angiography, carotid ultrasound, IVUS, MRI, and CT. This review will discuss the current status of atherosclerosis imaging as an endpoint in progression/regression trials, with an emphasis on evidence-based data. In addition to a discussion of the results of individual imaging modalities, the emerging data comparing different modalities and approaches are presented.

Identification of the metabolic syndrome and imaging of subclinical coronary artery disease: early markers of cardiovascular risk

The metabolic syndrome and imaging of subclinical coronary artery disease are novel approaches to identify cardiovascular risk at an early disease stage before the onset of complications. The metabolic syndrome is defined as a combination of major and emerging cardiovascular risk factors that are related to underlying insulin resistance. These risk factors accelerate atherosclerotic disease progression and increase the risk for future cardiovascular events. Atherosclerosis imaging visualizes the presence of subclinical disease burden many years before the onset of symptoms. The early identification of asymptomatic persons with increased cardiovascular risk provides the opportunity to prevent of future disease complications. The relationship between the metabolic syndrome and sublinical disease burden is incompletely understood. Although further evaluation of the potential role for the emerging biomarkers and imaging techniques in the setting of the metabolic syndrome is needed, it is obvious that cardiovascular nurses need to develop a heightened awareness of patients at risk for future events.

Determinants of Arterial Wall Remodeling During Lipid-Lowering Therapy

Background— Coronary plaque progression and instability are associated with expansive remodeling of the arterial wall. However, the remodeling response during plaque-stabilizing therapy and its relationship to markers of lipid metabolism and inflammation are incompletely understood.

Methods and Results— Serial intravascular ultrasound (IVUS) data from the Reversal of Atherosclerosis with Aggressive Lipid Lowering Therapy (REVERSAL) trial were obtained during 18 months of intensive versus moderate lipid-lowering therapy. In a subgroup of 210 patients, focal coronary lesions with mild luminal narrowing were identified. Lumen area, external elastic membrane (EEM) area, and plaque area were determined at the lesion and proximal reference sites at baseline and during follow-up. The remodeling ratio (RR) was calculated by dividing the lesion EEM area by the reference EEM area. The relationship between the change in remodeling, change in plaque area, lipid profile, and inflammatory markers was examined. At the lesion site, a progression in plaque area (8.9±25.7%) and a decrease in the RR (−3.0±11.2%) occurred during follow-up. In multivariable analyses, the percentage change in plaque area ( P <0.0001), baseline RR ( P <0.0001), baseline lesion lumen area (0.019), logarithmic value of the change in high-sensitivity C-reactive protein ( P =0.027), and hypertension at baseline ( P =0.014) showed a significant, direct relation with the RR at follow-up. Lesion location in the right coronary artery ( P =0.006), percentage change in triglyceride levels ( P =0.049), and age ( P =0.037) demonstrated a significant, inverse relation with the RR at follow-up. Changes in LDL cholesterol, HDL cholesterol, and treatment group demonstrated no significant associations.

Conclusions— Constrictive remodeling of the arterial wall was observed during plaque-stabilizing therapy with statin medications and appears related to their antiinflammatory effects.

Intravascular ultrasonography: using imaging end points in coronary atherosclerosis trials

Intravascular ultrasonography (IVUS) can precisely measure plaque burden and is being used to test new drug therapies. Other imaging tests may also prove useful to monitor treatment of atherosclerosis and identify populations at risk for coronary artery disease (CAD).

Pharmacologic strategies for the prevention of atherosclerotic plaque progression

Despite improved treatment options, coronary artery disease remains the leading cause of death in men and women in industrialized societies. Reduction of atherosclerotic disease will require the development and evaluation of new classes of pharmacologic agents capable of modifying the development and progression of the atherosclerotic disease process. The direct observation of coronary plaque burden and morphology with in vivo imaging modalities has been evaluated as an end point in serial pharmacologic intervention trials. This review will describe the use of intravascular ultrasound for such studies, summarize results from recent trials and outline potential future pharmacologic targets.

Noninvasive imaging of coronary arteries: current and future role of multi-detector row CT

While invasive imaging techniques, especially selective conventional coronary angiography, will remain vital to planning and guiding catheter-based and surgical treatment of significantly stenotic coronary lesions, the comprehensive and serial assessment of asymptomatic or minimally symptomatic stages of coronary artery disease (CAD) for preventive purposes will eventually need to rely on noninvasive imaging techniques. Cardiovascular imaging with tomographic modalities, including computed tomography (CT) and magnetic resonance imaging, has great potential for providing valuable information. This review article will describe the current and future role of cardiac CT, and in particular that of multi-detector row CT, for imaging of atherosclerotic and other pathologic changes of the coronary arteries. It will describe how tomographic coronary imaging may eventually supplement traditional angiographic techniques in understanding the patterns of atherosclerotic CAD development.

Coronary atherosclerotic disease burden: an emerging endpoint in progression/regression studies using intravascular ultrasound

Coronary artery disease (CAD) represents the major cause of mortality in North America and Western Europe. Most acute coronary events, including myocardial infarction (MI) and sudden cardiac death, are initiated by the sudden rupture of mildly stenotic but vulnerable lesions and subsequent thrombosis. Recent results demonstrate a high prevalence of such plaques many years before clinical events occur. Because the event rate in asymptomatic patients, which would be candidate for primary prevention, is relatively low, pharmacological studies with the endpoint of MI and death require large study populations and long follow-up. Alternatively, the direct observation of coronary plaque burden and morphology with in vivo imaging modalities has been proposed as an endpoint in serial studies. This review will summarize the rational of this approach and describe the use of intravascular ultrasound (IVUS) for such studies.