Measuring left ventricular mechanical dyssynchrony from ECG-gated SPECT myocardial perfusion imaging.

Cardiac resynchronization therapy (CRT) has shown benefits in patients with severe heart failure. The traditional criteria to select patients for CRT (New York Heart Association [NYHA] class III or IV, depressed left ventricular [LV] ejection fraction, and prolonged QRS duration) result in at least 30% of the selected patients with no response to CRT. Recent studies with echocardiography have shown that the presence of LV dyssynchrony is an important predictor for response to CRT. However, the recent report from the predictors of response to cardiac resynchronization therapy (PROSPECT) trial suggested that under ''real-world'' conditions the current available echocardiographic techniques including tissue Doppler imaging (TDI) and myocardial strain-rate imaging are not ready for routine clinical practice to assess LV dyssynchrony. Phase analysis is a recently developed technique that allows measuring LV dyssynchrony from electrocardiogram (ECG)-gated single photon emission computed tomography (GSPECT) myocardial perfusion imaging (MPI). This technique uses Fourier harmonic functions to approximate regional wall thickening over the cardiac cycle and to calculate regional onset of mechanical contraction (OMC) phases. These OMC phases are obtained three-dimensionally over the entire left ventricle to quantitatively assess the degree of LV dyssynchrony. This technique has been compared to TDI and shown promising results in clinical validations. The advantages of this technique over echocardiography in measuring LV dyssynchrony are its automation, its high repeatability and reproducibility. It can be applied to any conventional GSPECT MPI study with no additional procedure. In this review the phase analysis methodology is described and its up-to-date clinical validations are summarized.

Non-invasive anatomical and functional imaging for the detection of coronary artery disease.

Coronary artery disease (CAD) is still an important cause of morbidity and mortality in the Western world. The gold standard for assessing significant coronary artery stenosis is invasive coronary angiography. Several disadvantages of the technique in combination with the fact that a substantial number of patients referred for conventional angiography appear free from significant stenosis have led to the pursuit of non-invasive imaging modalities for the diagnosis of CAD. The traditional modalities for this purpose are gated single-photon emission computed tomography, position emission tomography, (contrast) stress echocardiography and cardiac magnetic resonance (CMR), and these techniques can be characterized as functional imaging techniques as they detect ischaemia. Although the presence of a flow-limiting stenosis can be adequately ruled out with these techniques, atherosclerosis cannot be visualized with functional techniques. For this purpose, non-invasive coronary angiography techniques (computed tomography and CMR) are currently under development. The purpose of this review is to provide the reader an overview of the currently used imaging modalities to detect CAD.

Comprehensive cardiac assessment with multislice computed tomography: evaluation of left ventricular function and perfusion in addition to coronary anatomy in patients with previous myocardial infarction.

OBJECTIVE: To evaluate a comprehensive multislice computed tomography (MSCT) protocol in patients with previous infarction, including assessment of coronary artery stenoses, left ventricular (LV) function and perfusion. PATIENTS AND METHODS: 16-slice MSCT was performed in 21 patients with previous infarction; from the MSCT data, coronary artery stenoses, (regional and global) LV function and perfusion were assessed. Invasive coronary angiography and gated single-photon emission computed tomography (SPECT) served as the reference standards for coronary artery stenoses and LV function/perfusion, respectively. RESULTS: 236 of 241 (98%) coronary artery segments were interpretable on MSCT. The sensitivity and specificity for detection of stenoses were 91% and 97%. Pearson's correlation showed excellent agreement for assessment of LV ejection fraction between MSCT and SPECT (49 (13)% v 53 (12)%, respectively, r = 0.85). Agreement for assessment of regional wall motion was excellent (92%, kappa = 0.77). In 68 of 73 (93%) segments, MSCT correctly identified a perfusion defect as compared with SPECT, whereas the absence of perfusion defects was correctly detected in 277 of 284 (98%) segments. CONCLUSIONS: MSCT permits accurate, non-invasive assessment of coronary artery stenoses, LV function and perfusion in patients with previous infarction. All parameters can be assessed from a single dataset.