Scar imaging using multislice computed tomography versus metabolic imaging by F-18 FDG positron emission tomography: A pilot study

Multiparametric assessment of left atrial remodeling using 18F-FDG PET/CT cardiac imaging: A pilot study

BACKGROUND

Left atrial (LA) remodeling is associated with structural, electric, and metabolic LA changes. Integrated evaluation of these features in vivo is lacking.

METHODS

Patients undergoing 18F-fluorodeoxyglucose (FDG) PET-CT during a hyperinsulinemic-euglycemic clamp were classified into sinus rhythm (SR), paroxysmal AF (PAF), and persistent AF (PerAF). The LA was semiautomatically segmented, and global FDG uptake was quantified using standardized uptake values (SUVmax and SUVmean) in gated, attenuation-corrected images and normalized to LA blood pool activity. Regression was used to relate FDG data to AF burden and critical patient factors. Continuous variables were compared using t-tests or Mann-Whitney tests.

RESULTS

117 patients were included (76% men, age 66.4 ± 11.0, ejection fraction (EF) 25[22-35]%) including those with SR (n = 48), PAF (n = 55), and PerAF (n = 14). Patients with any AF had increased SUVmean (2.3[1.5-2.4] vs 2.0[1.5-2.5], P = 0.006), SUVmax (4.4[2.8-6.7] vs 3.2[2.3-4.3], P < 0.001), uptake coefficient of variation (CoV) 0.28[0.22-0.40] vs 0.25[0.2-0.33], P < 0.001), and hypometabolic scar (32%[14%-53%] vs 16.5%[0%-38.5%], P = 0.01). AF burden correlated with increased SUVmean, SUVmax, CoV, and scar independent of age, gender, EF, or LA size (P < 0.03 for all).

CONCLUSIONS

LA structure and metabolism can be assessed using FDG PET/CT. Greater AF burden correlates with the increased LA metabolism and scar.

The Roles of Hypoxia Signaling in the Pathogenesis of Cardiovascular Diseases

The circulatory system distributes blood flow to each tissue and transports oxygen and nutrients. Peripheral circulation is required to maintain the physiological function in each tissue. Disturbance of circulation, therefore, decreases oxygen delivery, leading to tissue hypoxia which takes place in several cardiovascular disorders including atherosclerosis, pulmonary arterial hypertension and heart failure. While tissue hypoxia can be induced because of cardiovascular disorders, hypoxia signaling itself has a potential to modulate tissue remodeling processes or the severity of the cardiovascular disorders. Hypoxia inducible factor-1α (HIF-1α) and HIF-2α belongs to a group of transcription factors which mediate most of the cellular responses to hypoxia at a transcriptional level. We, and others, have reported that HIF-α signaling plays a critical role in the initiation or the regulation of inflammation. HIF-α signaling contributes to the tissue remodeling processes; thus it has a potential to become a therapeutic target. Elucidation of the molecular link, therefore, between hypoxia signaling and tissue remodeling will greatly help us to understand the pathophysiology of the cardiovascular disorders. The purpose of this review is to give a brief overview of the current understanding about the function HIF-α in inflammation processes especially by focusing on its roles in macrophages. In addition, the pathophysiological roles of hypoxia signaling for the development of cardiovascular disease will be discussed.

Myocardial scar characteristics based on cardiac magnetic resonance imaging is associated with ventricular tachyarrhythmia in patients with ischemic cardiomyopathy

OBJECTIVES

We hypothesized that myocardial scar characterization using cardiac magnetic resonance imaging (CMR) may be associated with the occurrence of ventricular tachyarrhythmia (VT), appropriate implantable cardioverter-defibrillator (ICD) therapy and mortality.

BACKGROUND

Since a minority of patients with prophylactic ICD implantation receive appropriate ICD therapy, there is a need for more effective risk stratification for primary prevention in patients with ischemic cardiomyopathy.

METHODS AND RESULTS

In 99 patients with ischemic cardiomyopathy, CMR was performed prior to ICD implantation. We assessed if CMR indices (cardiac mass, LVEF) and CMR scar characteristics (infarct core mass, peri-infarction mass and the ratio's between left ventricular mass, infarct core mass and peri-infarction mass) were associated with outcome. The primary endpoint was sustained VT and/or appropriate ICD therapy. The secondary endpoint was all-cause mortality. During a median follow-up of 5.4 years (IQR 4.5-6.6 years), 34 patients reached the primary end-point (17 appropriate ICD shocks) and 26 patients died. In multivariable Cox regression analysis, peri-infarction to core-infarction ratio (HR 2.01, 95%CI: 1.17-3.44, p=0.01) was independently and significantly associated with the primary endpoint, whereas NYHA-class and lower LVEF were not. Conversely, age (HR 1.06, 95% CI: 1.01-1.12, p=0.02) and lower LVEF (HR 0.95, 95% CI: 0.91-1.00, p=0.04) were independently associated with all-cause mortality, mainly due to heart failure.

CONCLUSION

A relatively large peri-infarction mass is associated with sustained VT and/or appropriate ICD therapy, whereas age and lower LVEF are associated with mortality. CMR based tissue characterization could aid in the prediction of specific outcome measures and in clinical decision making.

Role of viability imaging in the post-STICH era

PURPOSE OF REVIEW

Recent results from prospective randomized controlled trials examining the management of patients with ischemic cardiomyopathy (ICM) have questioned both the added value of revascularization over contemporary optimal medical therapy (OMT) and the use of viability testing as a gate-keeper to revascularization. The purpose of this review is to summarize recent trial evidence before discussing future perspectives in the field.

RECENT FINDINGS

The Surgical Treatment of Ischemic Heart Failure (STICH) trial, PPAR-2 trial and Heart Failure Revascularisation Trial have all reported their results within the past 5 years. None of these trials found revascularization superior to OMT in improving survival of ICM patients. Additionally, the STICH trial's viability substudy suggested that pretreatment viability testing was not beneficial.

SUMMARY

ICM patients remain a clinical conundrum. The numerous limitations of the recent RCTs have led to uncertainty about optimal management. Revascularization continues to be offered to patients with evidence of myocardial viability. Further studies are required to answer the outstanding questions in the management of patients with ICM.

Myocardial perfusion imaging with cardiac computed tomography: state of the art

Cardiac computed tomography (CCT) has become an important tool for the anatomic assessment of patients with suspected coronary disease. Its diagnostic accuracy for detecting the presence of underlying coronary artery disease and ability to risk stratify patients are well documented. However, the role of CCT for the physiologic assessment of myocardial perfusion during resting and stress conditions is only now emerging. With the addition of myocardial perfusion imaging to coronary imaging, CCT has the potential to assess both coronary anatomy and its functional significance with a single non-invasive test. In this review, we discuss the current state of CCT myocardial perfusion imaging for the detection of myocardial ischemia and myocardial infarction and examine its complementary role to CCT coronary imaging.