Assessment of the Influence of Atrial Fibrillation on Gated SPECT Perfusion Data by Comparison with Simultaneously Acquired Nongated SPECT Data

Taking the perfect nuclear image: quality control, acquisition, and processing techniques for cardiac SPECT, PET, and hybrid imaging

Nuclear Cardiology for the past 40 years has distinguished itself in its ability to non-invasively assess regional myocardial blood flow and identify obstructive coronary disease. This has led to advances in managing the diagnosis, risk stratification, and prognostic assessment of cardiac patients. These advances have all been predicated on the collection of high quality nuclear image data. National and international professional societies have established guidelines for nuclear laboratories to maintain high quality nuclear cardiology services. In addition, laboratory accreditation has further advanced the goal of the establishing high quality standards for the provision of nuclear cardiology services. This article summarizes the principles of nuclear cardiology single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging and techniques for maintaining quality: from the calibration of imaging equipment to post processing techniques. It also will explore the quality considerations of newer technologies such as cadmium zinc telleride (CZT)-based SPECT systems and absolute blood flow measurement techniques using PET.

Prognostic value of exercise echocardiography in patients with atrial fibrillation

AIMS

Non-invasive imaging techniques for the detection of coronary artery disease (CAD) may have technical problems in patients with atrial fibrillation (AF). Although the prognostic value of exercise echocardiography (ExEcho) has been well established in several subgroups of patients, it has not yet been specifically evaluated in these patients.

METHODS AND RESULTS

From a population of 8095 patients with known or suspected CAD referred for ExEcho, 419 had AF at the time of the tests. Ischaemia was defined as the development of new or worsening wall motion abnormalities with exercise. Endpoints were hard cardiac events (i.e. cardiac death or non-fatal myocardial infarction). Mean age was 68.4 +/- 8.5 years, and 256 patients (61.1%) were men. Ischaemia was detected in 92 patients (22%). Over a mean follow-up of 3.10 +/- 2.98 years, 59 hard cardiac events occurred. The 5-year hard cardiac event rate was 37.3% in patients with ischaemia, when compared with 14.5% in patients without ischaemia (P < 0.001). In multivariate analysis, ischaemia on ExEcho remained an independent predictor of hard cardiac events (hazard ratio 1.99, 95% confidence interval 1.06-3.74, P = 0.03), and also provided incremental value over clinical, resting echocardiographic and treadmill exercise data for the prediction of hard cardiac events (P = 0.04).

CONCLUSION

ExEcho provides significant prognostic information for predicting hard cardiac events in patients with AF.

Myocardial perfusion imaging does not adequately assess the risk of coronary artery disease in patients with atrial fibrillation

AIMS

The role of coronary artery disease (CAD) in atrial fibrillation (AF) is poorly investigated. This study investigated the value of myocardial perfusion single-photon emission computed tomography (SPECT) in the assessment of risk of CAD in patients with a history of AF.

METHODS AND RESULTS

Out of consecutive patients without previous coronary angiogram or history of CAD referred for SPECT, patients with a history of AF (n = 129) were compared with age- and gender-matched controls (n = 124). Primary endpoint was positive SPECT, i.e. unambiguous signs of ischaemia. There was no significant difference with regard to positive SPECT outcome between AF patients and controls (14 patients, 11% vs. 21 patients, 17%; P = 0.16). Coronary angiography (CAG) performed after SPECT demonstrated a higher yield of positive SPECT regarding significant CAD in control patients (10 out of 15 patients, 67%) than in AF patients (2 out of 13 patients, 15%; P = 0.006).

CONCLUSION

Positive SPECT outcome was similar in patients with AF and in controls. Nevertheless, in AF patients a positive SPECT outcome was less often related to significant CAD in those patients who subsequently underwent CAG. These results emphasize the need for new non-invasive techniques to adequately assess the risk of significant CAD in AF patients.