Digital angiographic assessment of the physiological changes to the regional microcirculation induced by successful coronary angioplasty

Development of a method for automated and stable myocardial perfusion measurement using coronary X-ray angiography images

The purpose of this study was to develop a method for automatic and stable determination of the optimal time range for fitting with a Patlak plot model in order to measure myocardial perfusion using coronary X-ray angiography images. A conventional two-compartment model is used to measure perfusion, and the slope of the Patlak plot is calculated to obtain a perfusion image. The model holds for only a few seconds while the contrast agent flows from artery to myocardium. Therefore, a specific time range should be determined for fitting with the model. To determine this time range, automation is needed for routine examinations. The optimal time range was determined to minimize the standard error between data points and their least-squares regression straight line in the Patlak plot. A total of 28 datasets were tested in seven porcine models. The new method successfully detected the time range when contrast agent flowed from artery to myocardium. The mean cross correlation in the linear regression analysis (R(2)) was 0.996 ± 0.004. The mean length of the optimal time range was 3.61 ± 1.29 frames (2.18 ± 1.40 s). This newly developed method can automatically determine the optimal time range for fitting with the model.

Development of a theory for generating regional cardiac perfusion images during coronary angiography in the coronary angiography lab

The purpose of this study was to develop a novel theory and method for generating regional myocardial perfusion images using fluoroscopy in the coronary angiography lab. We modified the Kety model to introduce the Patlak plot method for two-dimensional fluoroperfusion (FP) imaging. For evaluation, seven porcine models of myocardial ischemia with stenosis in the left coronary artery were prepared. Rest and stress FP imaging were performed using cardiovascular X-ray imaging equipment during the injection of iopamidol via the left main coronary artery. Images were acquired and retrospectively ECG gated at 80 % of the R-R interval. FP myocardial blood flow (MBF) was obtained using the Patlak plot method applied to time-intensity curve data of the proximal artery and myocardium. The results were compared to microsphere MBF measurements. Time-intensity curves were also used to generate color-coded FP maps. There was a moderate linear correlation between the calculated FP MBF and the microsphere MBF (y = 0.9758x + 0.5368, R² = 0.61). The color-coded FP maps were moderately correlated with the regional distribution of flow. This novel method of first-pass contrast-enhanced two-dimensional fluoroscopic imaging can quantify MBF and provide color coded FP maps representing regional myocardial perfusion.

Myocardium selective densitometric perfusion assessment after acute myocardial infarction

BACKGROUND

Myocardial perfusion is an important prognostic factor after recanalisation in acute myocardial infarction patients. We present a computerized, densitometric measurement method to assess myocardial perfusion on phase-matched digitally subtracted coronary angiograms.

METHODS AND MATERIALS

Quantitative myocardial perfusion was assessed by the G(max)/T(max) parameter of the time-density curves (TDCs) in infarct-related myocardial regions on X-ray coronary angiograms. Arteries were masked out from regions of measurement. This novel method has been compared with enzymatic infarct size, ST-segment resolution, and ejection fraction after successful revascularization of 62 patients with acute myocardial infarction.

RESULTS

Significant correlations were found between G(max)/T(max) and enzymatic infarct size (R=-0.445, P<.001), ST-segment resolution (R=0.364, P=.004), and ejection fraction (R=0.278, P=.029). Bland and Altman plot of G(max)/T(max) reveals good interobserver agreement.

CONCLUSIONS

G(max)/T(max) of the TDC measured in the infarct-related myocardial area is a reliable parameter to assess clinical indicators of myocardial reperfusion. Therefore, results suggest that it could be used to immediately assess the success of recanalisation at the tissue perfusion level during coronary intervention, and as an objective end point in clinical trials of new interventional devices and drugs.

Comparison of coronary flow velocity and regional myocardial perfusion for functional evaluation of coronary artery disease in the setting of angioplasty

Two essentially different methods for physiological evaluation of coronary artery disease were compared in the setting of angioplasty and related to quantitative coronary angiography. Forty-five patients, referred for percutaneous transluminal coronary angioplasty (PTCA), were examined by digital subtraction angiography (DSA) and by coronary flow velocity measurements distal to the target stenosis. Before PTCA, hyperemic mean transit time (HMTT) was correlated with % area stenosis r = 0.56*, coronary flow velocity reserve (CFVR) r = 0.58* and with CFVRN (CFVR normalized to a mean blood pressure of 100 mmHg) r = 0.68*. The correlation between CFVR and % area stenosis was r = 0.72* (*P < 0.001). After PTCA, all correlations between these measurements disappeared. HMTT and CFVR remained abnormal in 18% and 32 % of the patients, respectively. Pre-PTCA, distal coronary flow velocity measurements were reasonably well related to the assessment of regional myocardial perfusion. Flow velocity parameters, however, were better related to angiographic stenosis parameters. After PTCA, HMTT showed a more consistent improvement compared to CFVR. Flow velocity measurements appear to be more useful for the evaluation of local coronary stenoses, whereas the assessment of regional myocardial perfusion by DSA may be used for a more general evaluation of vessel territories.